JP5672464B2 - Secondary battery and manufacturing method thereof - Google Patents

Description

The present invention relates to a secondary battery including a current collector that has excellent corrosion resistance and can be used for a lithium ion battery, a sodium ion battery, an electric double layer capacitor, a lithium ion capacitor, and the like, and a method for manufacturing the same .

  In order to take in and out electrons between an electrochemical cell such as a battery and the outside, a conductive current collector is used in contact with the electrode. For example, in a lithium ion battery, a current collector made of aluminum is used as a current collector in contact with a positive electrode material, and nickel or the like is used as a current collector in contact with a negative electrode material. Discharging occurs. In a polymer electrolyte fuel cell, a separator made of metal functions as a current collector and takes out current to the outside.

  Current collectors are often placed in harsh corrosive environments (especially the current collector on the positive electrode (cathode) side where an electrochemical oxidation reaction takes place), and must have corrosion resistance. Is done. In order to meet the corrosion resistance requirement of the current collector, a corrosion-resistant film having conductivity is formed on the surface of the current collector made of metal. For example, Patent Document 1 proposes that a coating made of conductive graphite is formed on a substrate made of aluminum by sputtering to improve the corrosion resistance while having conductivity, and this is used as a separator for a fuel cell.

JP 2004-235091 A JP 2007-265852 A JP 2008-270092 A JP 2003-109582 A JP 2009-134988 A JP-A-11-111333 JP 2004-179146 A JP-A-8-321312

Surface Technology Vol.58, No.6, p337-341 (2007)

However, various electrode active materials (for example, positive electrode active materials such as Li ₂ NiPO ₄ F, LiNiPO ₄ , LiCoPO ₄ , and Li ₂ CoPO ₄ F in lithium ion batteries) have been developed for the battery, and the electromotive force of the battery is It is even bigger. Therefore, when the battery is charged, a large polarization voltage is applied to each electrode. If the electrolyte salt is a salt that does not easily form a fluorine compound or a complex compound of fluorine and oxygen, such as LiTFSI or LiBETI, There has been a problem that a corrosion current unrelated to charging / discharging of Li flows on aluminum as an electric material.

On the other hand, when the electrolyte salt is a salt that easily forms a fluorine compound or a compound compound of fluorine and oxygen represented by AlO _{x / 2} F _3-x , such as LiBF ₄ or LiPF ₆ (see Non-Patent Document 1). As the potential increases, the thickness of the passive film having a large electronic resistance to aluminum increases. As a result, the passivation progresses more than the contact area between the substrate and the conductive additive forming the electron path, and the electron path becomes narrow, so that there is a large possibility that the ohmic overvoltage increases and hinders high output. There are concerns.

  The present invention has been made in view of the above-described conventional circumstances, and has a current collector that exhibits conductivity and has excellent corrosion resistance even under severe corrosive environments, and a positive electrode active material that is charged at a high potential. It is a problem to be solved to provide a battery that exhibits excellent corrosion resistance even with a battery using the above.

The battery of the first invention has conductive diamond-like carbon, glassy carbon, gold and platinum on the surface of a current collector base material comprising aluminum, nickel or titanium as a main constituent or a current collector base material made of austenitic stainless steel. A current collector on which a conductive corrosion-resistant film made of one or more of these is formed;
A battery comprising an organic solvent,
The organic solvent includes a chain saturated hydrocarbon dinitrile compound in which a nitrile group is bonded to both ends of a chain saturated hydrocarbon compound, and a chain ether nitrile compound in which a nitrile group is bonded to at least one terminal of a chain ether compound. And at least one nitrile compound of cyanoacetate and at least one of cyclic carbonate, cyclic ester and chain carbonate.

In the battery of the first invention, conductive diamond-like carbon, glassy carbon, gold and platinum are formed on the surface of a current collector base material mainly composed of aluminum, nickel or titanium or a current collector base material made of austenitic stainless steel. Since the current collector on which a conductive corrosion-resistant film made of one or more of them is formed is used, the current collector exhibits excellent corrosion resistance.
The electrolytic solution is a chain saturated hydrocarbon dinitrile compound in which a nitrile group is bonded to both ends of a chain saturated hydrocarbon compound, or a chain ether nitrile compound in which a nitrile group is bonded to at least one terminal of a chain ether compound. And an organic solvent containing at least one nitrile compound of cyanoacetate and at least one of cyclic carbonate, cyclic ester and chain carbonate. For this reason, the excellent corrosion-resistant film | membrane originating in a nitrile is formed on an electrode or an electrical power collector, and it becomes a battery which has the further outstanding corrosion resistance with respect to electrolyte solution.

The current collector of the present invention has conductive diamond-like carbon, glassy carbon, gold and the like on the surface of a current collector base material comprising aluminum, nickel or titanium as a main constituent or a current collector base material made of austenitic stainless steel. A current collector on which a conductive corrosion-resistant film made of one or more of platinum is formed,
The corrosion-resistant film has defects, and the surface of the current collector substrate exposed from the defects is a fluorine compound, oxygen compound, nitrogen compound, carbon compound, phosphorus compound, boron of the current collector substrate. It is characterized by being covered with a passive film composed of one or more of the compounds.

  In the current collector of the present invention, a current collector base material mainly composed of aluminum, nickel or titanium or a current collector base material made of austenitic stainless steel is used. Here, “having aluminum, nickel, or titanium as a main constituent” refers to a metal containing 90% by mass or more of aluminum, nickel, or titanium. And since the electroconductive corrosion-resistant film which consists of 1 type or 2 types or more of electroconductive diamond-like carbon, glassy carbon, gold | metal | money, and platinum is formed in the surface of a collector base material, electrolyte salt is LiTFSI, Even in the case of a salt that does not easily form a complex compound of fluorine and oxygen, such as LiBETI, which is easily corrosion-resistant, it is far more than the current collector in which aluminum, nickel, titanium, or austenitic stainless steel is exposed. Therefore, the current collector has a wide potential window with high electron conductivity and excellent corrosion resistance.

  In addition, the surface of the current collector base material that is exposed to a defect in the corrosion-resistant film is one of the fluorine compound, oxygen compound, nitrogen compound, carbon compound, phosphorus compound, and boron compound of the current collector base material. Or since it is covered with the passive film which consists of 2 or more types, the progress of the corrosion from the defect which exists in a corrosion-resistant film | membrane is prevented by this passive film. For this reason, it has much higher conductivity and excellent corrosion resistance than a current collector made of aluminum, nickel, titanium, or austenitic stainless steel, as in the case where there is no defect in the conductive corrosion-resistant film. It becomes a current collector.

  As the austenitic stainless steel, one or more of SUS304, SUS316 and SUS306L defined by Japanese Industrial Standards can be used.

On the other hand, in the case where the electrolyte salt is a salt that easily forms a fluoride, such as LiBF ₄ or LiPF ₆ , a fluorine compound with high electronic resistance or fluorine and oxygen formed on aluminum or the like as the potential increases. By increasing the thickness of the passive film made of the composite compound, corrosion resistance can be secured even at a high potential of 10 V or higher. On the contrary, the electronic conductivity of the passive film portion made of a fluorine compound or a composite compound of fluorine and oxygen is lowered, but in the current collector of the present invention, most of the current collector base material has conductivity. Since it is covered with one or more of diamond-like carbon, glassy carbon, gold, and platinum, the decrease in electron conductivity due to the passive film on the current collector substrate is caused by a very small area of the defective portion. Only occurs. Therefore, even if the voltage is increased, the decrease in electron conductivity is negligible, and it is possible to prevent the decrease in output caused by the increased voltage.

In the present invention, the conductive diamond-like carbon is a carbon having an amorphous structure in which both diamond bonds (SP ₃ hybrid orbital bonds between carbons) and graphite bonds (SP ₂ hybrid orbital bonds between carbons) are mixed. Among them, the one whose conductivity is 1000 Ωcm or less. However, in addition to the amorphous structure, those having a phase composed of a crystal structure partially composed of a graphite structure (that is, a hexagonal crystal structure composed of SP ₂ hybrid orbital bonds) and thereby exhibiting conductivity are also included. . Diamond-like carbon having properties intermediate between graphite and diamond adjusts the conductivity by adjusting the ratio of SP ₂ hybrid orbital bonds and SP ₃ hybrid orbital bonds of the carbon atoms constituting diamond-like carbon during film formation. be able to. In addition, the conductivity and corrosion resistance can be adjusted by substituting trace elements for different elements other than carbon. Examples of the different elements include Ti, Cr, Al, Fe, Ni, Cu, Ag, Mo, W, B, and Si.

  As described above, since the current collector of the present invention is extremely excellent in corrosion resistance and has a wide potential window, the current collectors of various electric storage devices such as lithium ion batteries and sodium ion batteries with high charging voltage, such as electric double layer capacitors and lithium ion capacitors. It can be suitably used as a body.

The battery of the second invention of the present invention has a surface of a current collector base material comprising aluminum, nickel or titanium as a main component or a current collector base material made of austenitic stainless steel, conductive diamond-like carbon, glassy carbon, A current collector on which a conductive corrosion-resistant film made of one or more of gold and platinum is formed, and an electrolyte solution containing an electrolyte having at least one of BF ₄ anion and PF ₆ anion It is characterized by that.

In the battery according to the second aspect of the present invention, conductive diamond-like carbon, glassy carbon, Since the current collector on which a conductive corrosion-resistant film made of one or more of gold and platinum is formed is used, the current collector exhibits excellent corrosion resistance.
Furthermore, since the electrolyte has at least one of BF ₄ anion and PF ₆ anion, an excellent corrosion-resistant film containing fluorine or the like is formed.

  In the battery of the second invention of the present invention, the electrolytic solution contains a chain saturated hydrocarbon dinitrile compound in which a nitrile group is bonded to both ends of the chain saturated hydrocarbon compound, and a nitrile at at least one terminal of the chain ether compound. An organic solvent containing at least one nitrile compound among a chain ether nitrile compound and a cyanoacetate group to which a group is bonded and at least one of a cyclic carbonate, a cyclic ester, and a chain carbonate may be included. If it is like this, the outstanding corrosion-resistant film | membrane originating in a nitrile will be formed on an electrode or an electrical power collector, and it will become a battery which has the further outstanding corrosion resistance with respect to electrolyte solution.

It is a schematic diagram which shows the preparation methods of the electrical power collector of embodiment. It is a graph which shows the relationship between the electric potential in the electrode of Example 1 and Comparative Examples 1-4. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. It is a graph which shows the result of the surface analysis by XPS after the potential scan of the electrode of Example 3 and Comparative Examples 1, 5, and 8. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. It is a graph which shows the relationship between the electric potential in the electrode of Example 2 and Comparative Examples 5-7, and an electric current. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. It is a graph which shows the relationship between the electric potential in the electrode of Example 3 and Comparative Example 8, and an electric current. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. It is a graph which shows the electric potential in the electrode of Example 4 and Comparative Example 9, and the relationship of an electric current. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. It is a graph which shows the relationship between the electric potential in the electrode of Example 5 and Comparative Example 10, and an electric current. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. It is a graph which shows the relationship between the electric potential in the electrode of Example 6 and Comparative Example 11, and an electric current. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. 10 is a graph showing the relationship between potential and current in an electrode of Example 7. It is a graph which shows the relationship between the electric potential in the electrode of Example 8 and Comparative Examples 12-20, and an electric current. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. It is a graph which shows the relationship between the electric potential in the electrode of Example 9 and Comparative Examples 21-22, and an electric current. For simplification of the drawing, the conductive diamond-like carbon is indicated as DLC in the figure. 10 is a graph showing the relationship between potential and current in an electrode of Example 9. It is a schematic cross section of a lithium ion battery using the current collector of the embodiment. 2 is a potential-current curve of Example 1 and Comparative Example 1. FIG. It is the electric potential-current curve of Examples 2-9 and Comparative Example 1. 6 is a potential-current curve of Comparative Example 1. It is an electric potential-current curve of Examples 10-17 and Comparative Example 2. It is an electric potential-current curve of Examples 18-25 and Comparative Example 3. It is an electric potential-current curve of Examples 26-31 and Comparative Example 4. It is an electric potential-current curve of Examples 32 and 33 and Comparative Example 5. It is an electric potential-current curve of Examples 34-36 and Comparative Example 6. It is an electric potential-current curve of Examples 37-39 and Comparative Example 7. 4 is a potential-current curve of Examples 41 to 45 and Comparative Example 1. FIG. 10 is a potential-current curve of Example 45 and Comparative Example 8. FIG. It is an electric potential-current curve of Example 46 and Comparative Example 8. It is an electric potential-current curve of Example 47 and Comparative Example 1. It is a potential-current curve in a mixed solvent in which ethylene carbonate: dimethyl carbonate = 1: 1 and a predetermined amount of sebacononitrile was added. 42 is a potential-current curve of lithium occlusion / release using the lithium ion battery electrolyte of Example 41. FIG.

(Embodiment 1)
As shown in FIG. 1, a base material 1 made of aluminum, nickel, titanium, or austenitic stainless steel (for example, SUS304, SUS316, SUS306L, etc.) is prepared, and a corrosion-resistant film 2 made of conductive diamond-like carbon is formed thereon.

The method for forming the conductive diamond-like carbon film is not particularly limited. For example, CVD method, thermal CVD, plasma CVD (high frequency, microwave, direct current, etc.), PVD method, vacuum deposition method, ion plating (direct current excitation, It can be formed using techniques such as high frequency excitation), sputtering (bipolar sputtering, magnetron sputtering, ECR sputtering), laser ablation, ion beam deposition, and ion implantation.

A more specific method for the plasma CVD method and the PVD method is as follows.
(1) Method of forming a conductive diamond-like carbon film by plasma CVD method A current collector base is placed in a chamber, a hydrocarbon gas such as acetylene is introduced into the chamber, and plasma is generated by electromagnetic induction to generate a gas phase. The deposited hydrocarbon is deposited on the surface of the current collector substrate. The conductive diamond-like carbon film produced by this method always contains hydrogen because it contains hydrogen. This manufacturing method has many industrial advantages such as that the temperature of the current collector base material does not need to be so high, and it is easy to form a uniform film even in a complicated shape by the arrangement of electrodes, and the processing time is relatively short.
(2) Method of forming conductive diamond-like carbon film by PVD method It is preferable to use a sputtering method or an ion plating method which is a kind of PVD method. This method is a method in which graphite is exposed to an ion beam, an arc discharge, a glow discharge, or the like in a vacuum, and carbon atoms ejected by a sputtering phenomenon are attached to a current collector substrate.

Further, the surface of the current collector substrate 1 exposed from the defects 3 present in the conductive corrosion-resistant film 2 is made of one or more of fluorine compounds, oxygen compounds, nitrogen compounds, carbon compounds and phosphorus compounds. Cover with passive film 4. For example, it is known that a passive film is formed when aluminum is treated at high potential in the electrolyte of a lithium ion battery (2000 Electrochemical Society. Abstracts of Autumn Meeting, p.17 (2000) ), Surface technology Vol.58, No.6, p337-341 (2007)), this phenomenon can be used to form the passive film 4 on the defects of the corrosion-resistant film. That is, the current collector base material 1 on which the conductive corrosion-resistant film 2 is formed is immersed in a cyclic carbonate and / or chain carbonate solution of LiPF ₆ , LiBF _4, or LiClO ₄ used as an electrolyte of a lithium ion battery. And a potential required for charging (more desirably, a potential of about 6 V to 7 V with respect to the reference electrode (Li / Li ⁺ )). In the case of aluminum, it is oxidized by defects 3 present in the conductive corrosion-resistant film 2, and when the salt is LiPF ₆ or LiBF _4, a passive film 4 made of a fluorine compound or a composite compound of fluorine and oxygen is formed. When the salt is LiClO ₄ , an oxygen compound is formed. Thus, the current collector of the present invention is obtained.

(Embodiment 2)
Instead of the corrosion-resistant film made of conductive diamond-like carbon in Embodiment 1, a conductive corrosion-resistant film made of glassy carbon can also be used. Such a corrosion-resistant film can be formed, for example, by the method described in JP-A-11-4377. That is, the current collector base material made of a metal such as titanium is subjected to plasma heat treatment in an atmosphere of 0.1 to 30 torr and 400 to 1100 ° C. containing a hydrocarbon gas such as methane, ethane, or propane. Thereby, a glassy carbon film is formed on the surface of the current collector substrate.

(Embodiment 3)
Instead of the corrosion-resistant film made of conductive diamond-like carbon in Embodiment 1, a conductive corrosion-resistant film made of gold or platinum can also be used. In this case, the PVD apparatus is provided with gold or platinum as a target electrode, a current collector base is placed in the chamber and the apparatus is evacuated. Discharge is performed while applying a high negative voltage to the material. As a result, the ionized introduced gas is accelerated by the voltage and collides with the target electrode, causing a sputtering phenomenon. The sputtered gold or platinum particles adhere to the surface of the current collector substrate, and a conductive corrosion-resistant film can be formed.

Examples of the current collector of the present invention will be described below in comparison with comparative examples.
Example 1
In Example 1, an electrode in which a conductive diamond-like carbon film was formed on the surface of an aluminum electrode by plasma CVD was prepared, and the potential was scanned in an electrolyte for a lithium ion battery, and a potential-current curve was measured. The electrolytic solution was prepared as follows. That is, a mixed solution was prepared so that ethylene carbonate, dimethyl carbonate, and sebaconitrile were in a mass ratio of 25:25:50, and a solution in which LiPF ₆ was dissolved so as to be 1 mol / L was used as an electrolytic solution. Placed in an electrolytic cell container.

In the electrochemical measurement, an electrode (area 0.5 cm ² ) was used as a working electrode, a platinum mesh was used as a counter electrode, and Li metal was used as a reference electrode. The measurement was performed by scanning the reference electrode three times between 3V and 8V, and measuring the potential-current curve. The sweep speed was 5 mV / sec.

(Comparative Example 1)
In Comparative Example 1, the aluminum substrate was subjected to potential scanning in the electrolytic solution for lithium ion batteries in the same manner as in Example 1, and a potential-current curve was measured. Furthermore, the surface analysis by XPS was performed about the aluminum electrode which finished the potential scan.

(Comparative Example 2)
In Comparative Example 2 , a potential-current curve was measured by scanning the potential of the gold electrode in the electrolyte for a lithium ion battery in the same manner as in Example 1.

(Comparative Example 3)
In Comparative Example 3, a potential-current curve was measured by scanning the potential of the platinum electrode in the electrolyte for a lithium ion battery in the same manner as in Example 1.

(Comparative Example 4)
In Comparative Example 4, the potential-current curve was measured by scanning the potential of the glassy carbon electrode in the lithium ion battery electrolyte as in Example 1.

<Evaluation>
The results are shown in FIG. In the first sweep of the electrode (aluminum electrode) of Comparative Example 1, an oxidation current began to flow from about 4 V, and a large oxidation current flowed as the potential increased. However, in the second sweep, the oxidation current almost flowed. There wasn't. In XPS measurement, as shown in FIG. 3C, a fluorine compound, an oxygen compound, a nitrogen compound, a carbon compound, and a phosphorus compound are present on the surface of aluminum, and the electrode of Comparative Example 1 (aluminum electrode). Then, it turned out that the passive film which consists of these compounds is formed by the 1st sweep.

  On the other hand, in the electrode of Example 1 in which the film made of conductive diamond-like carbon was formed on the aluminum electrode, almost no current flows up to about 6.4 V even in the first scan, and about 50 μA even at 7.2 V. It was found that the corrosion resistance was also excellent after the second time. Moreover, from the comparison with the potential-current curve of Comparative Example 2 (gold electrode), Comparative Example 3 (platinum electrode), and Comparative Example 4 (glassy carbon), the electrode of Example 1 has better corrosion resistance than gold or platinum. It has been found that the glass has the same corrosion resistance as that of glassy carbon.

Further, from the XPS measurement results after potential scanning at the electrode (aluminum electrode) of Comparative Example 1 and the potential-current curve of the electrode of Example 1, the following became clear.
That is, in the electrode of Example 1, if a potential scan is performed in the above electrolyte solution for lithium ion batteries, fluorine compound, oxygen compound, nitrogen compound or carbon is exposed to aluminum exposed from defects in the film made of conductive diamond-like carbon. Corrosion resistance is ensured by covering with a passive film made of a compound or a phosphorus compound, and furthermore, a film made of conductive diamond-like carbon has a structure that can secure electron conductivity.

(Example 2)
In Example 2, an electrode in which a conductive diamond-like carbon film was formed on the surface of a nickel plate by plasma CVD was used as the electrode base on the working electrode side, and LiBF ₄ was used as the electrolyte. The other measurement conditions are the same as in Experimental Example 1, and detailed description thereof is omitted.

(Comparative Example 5)
In Comparative Example 5, the potential-current curve was measured by scanning the potential of the nickel substrate in the electrolyte for a lithium ion battery in the same manner as in Example 2. Furthermore, the surface analysis by XPS was performed about the nickel electrode which finished sweeping.

(Comparative Example 6)
In Comparative Example 6, the potential-current curve was measured by scanning the potential of the platinum electrode in the electrolyte for a lithium ion battery in the same manner as in Example 2.

(Comparative Example 7)
In Comparative Example 7, the potential-current curve was measured by scanning the potential of the glassy carbon electrode in the lithium ion battery electrolyte in the same manner as in Example 2.

<Evaluation>
As a result, as shown in FIG. 4, in the first sweep of the electrode of Comparative Example 5 (nickel electrode), an oxidation current began to flow from about 4.6 V, and a large oxidation current flowed as the potential increased. In the second sweep, the oxidation current hardly flowed up to about 6V. Further, from XPS measurement, as shown in FIG. 3 (a), oxygen compound, nitrogen compound, carbon compound and phosphorus compound are present on the surface of nickel. It was found that a dynamic film was formed.

  On the other hand, in the electrode of Example 2 in which a film made of conductive diamond-like carbon is formed on the nickel electrode, as shown in FIG. 4, almost no current flows up to about 6.4 V even in the first scan. In the second scan, the potential window further spreads to the high potential side by about 0.2V. Moreover, it turned out that the electrode of Example 2 shows the corrosion resistance superior to platinum by the comparison with the electric potential-current curve of the comparative example 6 (platinum electrode).

Further, from the XPS measurement results after potential scanning at the electrode (aluminum electrode) of Comparative Example 1 and the potential-current curve of the electrode of Example 1, the following became clear.
That is, the surface of nickel exposed from defects in the film made of conductive diamond-like carbon can be obtained by performing a potential scan in the electrolyte solution for lithium ion batteries on an electrode in which a film made of conductive diamond-like carbon is formed on a nickel electrode. Further, a passive film made of an oxygen compound, a nitrogen compound, a carbon compound, and a phosphorus compound covers it, and the corrosion resistance can be drastically improved.

Example 3
In Example 3, an electrode in which a conductive diamond-like carbon film was formed on the surface of a titanium plate by a plasma CVD method was used as the electrode base on the working electrode side. The other measurement conditions are the same as in Example 1, and detailed description thereof is omitted.

(Comparative Example 8)
In Comparative Example 8, the potential-current curve was measured by scanning the potential of the titanium substrate in the electrolyte for a lithium ion battery in the same manner as in Example 1. Furthermore, the surface analysis by XPS was performed about the nickel electrode which finished sweeping.

<Evaluation>
As a result, as shown in FIG. 5, in the first sweep of the electrode of Comparative Example 8 (titanium electrode), an oxidation current began to flow from about 4.6 V, and a large oxidation current flowed as the potential increased. In the second and subsequent sweeps, the increase in current was extremely small even when it exceeded 4.6 V, and it was superior to that of glassy carbon at 7 V or more.
Further, from the XPS measurement, as shown in FIG. 3B, oxygen compounds, nitrogen compounds, carbon compounds, and phosphorus compounds are present on the surface of titanium. It was found that a passive film composed of the compound was formed.

  On the other hand, in the electrode of Example 3 in which a film made of conductive diamond-like carbon is formed on the titanium electrode, as shown in FIG. In the second scan, it was found that the same level of corrosion resistance was exhibited.

Further, from the XPS measurement results after potential scanning at the electrode (titanium electrode) of Comparative Example 8 and the potential-current curve of the electrode of Example 3, the following became clear.
That is, even if an electrode having a film made of conductive diamond-like carbon formed on a titanium electrode is subjected to a potential scan in the lithium ion battery electrolyte, oxygen exposed to titanium exposed from defects in the film made of conductive diamond-like carbon. A passive film composed of a compound, a nitrogen compound, a carbon compound, and a phosphorus compound covers and can drastically enhance the corrosion resistance.

(Examples 4 to 6)
In Examples 4 to 6, conductive diamond-like carbon was formed on the surface of austenitic stainless steel (SUS304 in Example 4, SUS316 in Example 5 and SUS316L in Example 6) by plasma CVD as an electrode base on the working electrode side. An electrode on which a film was formed was used. The other measurement conditions are the same as in Example 1, and detailed description thereof is omitted.

(Comparative Examples 9-11)
In Comparative Examples 9 to 11, the austenitic stainless steel (Comparative Example 9 is SUS304, Comparative Example 10 is SUS316, and Comparative Example 11 is SUS316L). The potential-current curve was measured.

As a result, as shown in FIG. 6, in the first sweep of the electrode of Comparative Example 9 (SUS304 electrode), an oxidation current slightly flowed from about 5.6 V, and a substantially constant current continued thereafter. However, the current decreased in the second and subsequent sweeps.
On the other hand, in the electrode of Example 4 in which a film made of conductive diamond-like carbon was formed on the SUS304 electrode, almost no current flows up to about 7 V even in the first scan, and the same level is obtained in the second scan. It was found that it exhibits excellent corrosion resistance.

As for the electrode of Comparative Example 10 (SUS316 electrode) and the electrode of Comparative Example 11 (SUS316L electrode), as shown in FIG. 7 and FIG. A constant current continued to flow, but the current decreased in the second and subsequent sweeps.
On the other hand, in the electrode of Example 5 in which the film made of conductive diamond-like carbon was formed on the SUS316 electrode and the electrode of Example 6 in which the film made of conductive diamond-like carbon was formed on the SUS316L electrode, the first scan was performed. However, almost no current flows up to about 7V, and it was found that the second scan also showed the same excellent corrosion resistance.

(Example 7)
In Example 7, a conductive diamond-like carbon film was formed on an aluminum substrate in the same manner as in Example 1, and then an electrode whose surface was intentionally scratched by cutting glass made of diamond was used. For this electrode, as in the case of the measurement of the potential-current curve in Example 1, a mixed solution was prepared so that ethylene carbonate, dimethyl carbonate, and sebaconitrile were in a mass ratio of 25:25:50, and further LiPF. _A potential-current curve was measured using a solution in which ₆ was dissolved at 1 mol / L as an electrolytic solution.

As a result, as shown in FIG. 9, in the first sweep, 2.3V (vs Li / Li ⁺⁾ of the beginning oxidation current flows from, 3.3V current of more than (vs Li / Li ⁺⁾ at 50μA On the other hand, in the second sweep, almost no current flowed up to 5 V (vs Li / Li ⁺ ). In the first sweep, the current collector base aluminum, which is defective in the conductive diamond-like carbon film, reacts with the electrolytic solution and a reaction current flows to form a passive film. In the sweep, the defect portion is covered with a passive state, so that it is considered that almost no reaction current with aluminum flows near the current that reacts on the conductive diamond-like carbon. For this reason, in the second sweep, since most of the surface of the aluminum base material is covered with conductive diamond-like carbon, a conductive diamond-like carbon film having no defects is formed as in the electrode of Example 1. The electrode has a wide potential window as in the case of the electrode.

(Example 8)
The electrode of Example 8 was an electrode in which a conductive diamond-like carbon film having no defect was formed on a titanium substrate in the same manner as in Example 3.

(Comparative Examples 12 to 20)
Comparative Example 12 for an untreated titanium electrode, Comparative Example 13 for an untreated aluminum electrode, Comparative Example 14 for an untreated nickel electrode, Comparative Example 15 for an untreated SUS304 electrode, Comparative Example 16 for an untreated SUS316 electrode, The untreated SUS316L electrode was designated as Comparative Example 17, the untreated glassy carbon electrode as Comparative Example 18, the untreated platinum electrode as Comparative Example 19, and the untreated gold electrode as Comparative Example 20.

<Evaluation>
About the electrode of the said Example 8 and the electrodes of Comparative Examples 12-20, a liquid mixture is prepared so that ethylene carbonate, a dimethyl carbonate, and a sebaconitrile may be set to 25:25:50 by mass ratio, and also LiTFSI is 1 mol / L. The potential-current curve was measured using the solution so dissolved as an electrolyte.
A potential-current curve was measured.

As a result, as shown in FIG. 10, in this measurement using LiTFSI as the electrolyte, Comparative Example 12 (titanium), Comparative Example 13 (aluminum), Comparative Example 14 (nickel), and Comparative Examples 15 to 17 (austenitic series) A large current flowed through the electrode of stainless steel at a potential of 5 V (vs Li / Li ⁺ ) or less, and the potential window was narrow.
On the other hand, in the electrode of Example 8 in which a conductive diamond-like carbon film having no defect is formed on titanium, the potential window is relatively wide and the potential window is about 6.5 V (vs Li / Li ⁺ ). It was.
From the above results, there is no defect in conductive diamond-like carbon in any base material, not limited to the base material with a narrow potential window, as well as a titanium, aluminum, nickel, and austenitic stainless steel base material with a narrow potential window. It can be easily assumed that a wide potential window of 6.5 V (vs Li / Li ⁺ ) can be secured if the film is formed in this state.

Further, the potential windows of the electrodes of Comparative Example 18 (Glassy Carbon), Comparative Example 19 (Platinum), and Comparative Example 20 (Gold) are Comparative Example 12 (Titanium), Comparative Example 13 (Aluminum), and Comparative Example 14 (Nickel). And Comparative Examples 15 to 17 (austenitic stainless steel) have a wider potential window, about 6.3 V (vs Li / Li ⁺ ) in comparative example 18 (glassy carbon), and 5.9 V (vs in comparative example 19 (platinum)). Li / Li ⁺⁾ or so, it was the Comparative example 20 ^{(gold) 5.8V (vs Li / Li +} ) degree.
From the above results, even with electrodes with narrow potential windows such as titanium, aluminum, nickel, and austenitic stainless steel with narrow potential windows, glassy carbon, platinum, and gold are in a state of no defects as with conductive diamond-like carbon. It can be easily inferred that a wide potential window can be secured if a film is formed by (1).
If the adhesion between the conductive diamond-like carbon, glassy carbon, platinum and gold to be deposited and the electrode serving as the substrate is insufficient, the substrate temperature may be raised, and an intermediate layer may be inserted. May be. For example, the intermediate layer of conductive diamond-like carbon includes Ti, Si, SiC, TiC, Cr and Nb (DLC Handbook, published by NTS, p598). In the case of Au film formation, it is well known that adhesion is improved by using Ni as an intermediate layer.

(Comparative Example 21 and Comparative Example 22)
The electrode of Comparative Example 21 is an electrode in which a conductive diamond-like carbon film was formed on an aluminum substrate in the same manner as in Example 1, and then the surface was intentionally damaged by cutting glass made of diamond.
The electrode of Comparative Example 22 is an electrode in which a diamond-like carbon film was formed on a nickel substrate in the same manner as in Example 2, and then the surface was intentionally damaged by cutting glass made of diamond.

For the electrodes of Comparative Example 21 and Comparative Example 22 prepared as described above, a mixed solution was prepared so that ethylene carbonate, dimethyl carbonate and sebaconitrile were in a mass ratio of 25:25:50, and further LiTFSI was 1 mol / mol. The potential-current curve was measured using the solution dissolved so as to be L as the electrolytic solution.
For comparison, the potential-current curve was measured in the same manner for Example 8 (electrode formed with a conductive diamond-like carbon film having no defect on a titanium substrate) and an electrode made of Al, Ti, and Ni. went.

As a result, as shown in FIG. 11, in Example 8 (electrode having a film of conductive diamond-like carbon having no defect formed on the titanium substrate) having no defect, it is almost up to 6V (vs Li / Li ⁺ ). While no current flows, the electrode of Comparative Example 21 (that is, the electrode that was damaged after forming a conductive diamond-like carbon film on the aluminum substrate) was 4.1 V (vs. A small amount of corrosion current starts to flow from the vicinity of (Li / Li ⁺ ) (Comparative Example 21). Finally, a large current suddenly flowed from around 6.3 V (vs Li / Li ⁺ ) where the reaction current began to flow on the conductive diamond-like carbon.
Further, the electrode of Comparative Example 22 (that is, the electrode that was damaged after forming a conductive diamond-like carbon film on the nickel substrate) was corroded from around 5 V (vs Li / Li ⁺ ), the same as the nickel electrode. Current began to flow.
From the above results, it can be seen that when the conductive diamond-like carbon film has a defect and the substrate touches the electrolyte at that defect, the corrosion current starts to flow around the same potential as the potential for corrosion of the substrate. It was. Further, even if a glassy carbon, platinum, or gold film is formed, if the film is defective, similar to the electrodes of Comparative Examples 21 and 22, near the potential at which corrosion of the substrate occurs. It can be easily guessed that the corrosion current starts to flow.

Example 9
The electrode of Example 9 was prepared by forming a conductive diamond-like carbon film on an aluminum substrate in the same manner as in Example 1 and then intentionally scratching the surface with diamond glass. In addition, a mixed solution of ethylene carbonate, dimethyl carbonate, and sebaconitrile is prepared at a mass ratio of 25:25:50, and a solution in which LiPF ₆ is dissolved to 1 mol / L is prepared. It is an electrode after the potential sweep in which a potential-current curve was measured as an electrolytic solution.

  For the electrode of Example 9 obtained in this way, a mixed solution was prepared so that ethylene carbonate, dimethyl carbonate, and sebaconitrile were in a mass ratio of 25:25:50, and further LiTFSI was dissolved to be 1 mol / L. The potential-current curve was measured using the solution as an electrolytic solution. For comparison, a potential-current curve was similarly measured for an aluminum electrode that had not been subjected to any surface treatment.

As a result, as shown in FIG. 12, the electrode of Example 9 had a potential window at a level equivalent to that of the electrode of Example 8 in which a conductive diamond-like carbon film having no defect was formed on the titanium substrate. On the other hand, in the aluminum electrode not subjected to any surface treatment, a corrosion current suddenly flowed out from around 4.1 V (vs Li / Li ⁺ ).
The above results can be explained as follows. That is, as in the electrode of Example 9, even when the film was defective on the conductive diamond-like carbon, the mixed liquid was such that ethylene carbonate, dimethyl carbonate, and sebaconitrile were in a mass ratio of 25:25:50. In addition, by performing potential sweep using a solution in which LiPF ₆ is dissolved to 1 mol / L as an electrolytic solution, a passive film exhibiting excellent corrosion resistance can be formed on the defective portion. Further, since the portion other than the defect is covered with a film made of conductive diamond-like carbon, the portion capable of electrode reaction is substantially only the conductive diamond-like carbon film portion. For this reason, the electrode of Example 9 also has excellent corrosion resistance and an electrode having a wide potential window, similar to Example 8 (that is, an electrode formed with a conductive diamond-like carbon film having no defects in aluminum). It is.
Further, when glassy carbon, platinum, or gold is used as a film forming material instead of the conductive diamond-like material having defects in the ninth embodiment, the same film forming material as glassy carbon, platinum, or gold is used. A potential window of the order of magnitude.

From the above results, it can be seen that when LiPF ₆ or LiBF ₄ is used as the electrolyte of the secondary battery, when the electrode base material is aluminum, a passive film is formed and exhibits excellent corrosion resistance.
In addition, when LiTFSI is used as an electrolyte of a secondary battery, even if a film (for example, a conductive diamond-like carbon film, a glassy carbon, a platinum film, or a gold film) on an aluminum substrate has a defect, the electrode If the potential is swept in advance with an electrolyte containing LiPF ₆ or LiBF ₄ as an electrolyte, a passive film is formed on the aluminum in the defective portion, and the progress of corrosion from the defect can be stopped. The electrode has the same excellent corrosion resistance.

<Production of lithium ion battery>
A lithium ion battery can be manufactured using the current collector of the embodiment described above. That is, as shown in FIG. 13, a positive electrode 7 containing a positive electrode active material and a negative electrode 8 made of carbon or the like are disposed on both sides with a separator 6 sandwiched between battery containers 5 made of stainless steel or the like. Further, a current collector 9 made of aluminum as a base material is brought into contact with the positive electrode 7, and one end thereof is protruded from the battery container 5. Further, a current collector 10 made of nickel or titanium as a base material is brought into contact with the negative electrode 8, and one end of the current collector 10 protrudes from the battery container 5. And the electrolyte solution for lithium ion batteries is put in an inside. The current collectors 9 and 10 have a conductive diamond-like carbon film formed on the base material, and defects in the film made of conductive diamond-like carbon, glassy carbon, Pt, and Au are made of aluminum, nickel, or titanium. Since it is covered with a passive film made of a fluorine compound, it has conductivity and is extremely excellent in corrosion resistance. The passive film differs depending on the electrolyte and solvent used, but is formed of one or a composite of fluorine compounds, oxygen compounds, nitrogen compounds, carbon compounds and phosphorus compounds.

In the lithium ion battery, a high-potential redox positive electrode active material in which the potential for charging exists in a region exceeding 5.2 V (vs. Li / Li ⁺ ) by using a battery electrolyte containing nitrile. Can be used as the positive electrode active material, and therefore, the electromotive force and energy density of the battery can be extremely increased. Such high potential redox positive electrode active material, for _{example, Li 2 CoPO 4 F, Li} 2 NiPO 4 F, LiCoPO 4, LiNiPO 4 , and the like. These positive electrode active materials have high energy density and can be a lithium ion battery having a large capacity. For example, Li ₂ CoPO ₄ F is predicted to have a theoretical energy density that is at least twice that of LiCoO ₂ as a positive electrode active material. If the potential density can be sufficiently exhibited, a lithium-ion battery having a large capacity can be produced. be able to. In addition, since the potential at which Li ₂ CoPO ₄ F is oxidized extends to a high potential region, a battery with high electromotive force can be obtained. Furthermore, Li ₂ CoPO ₄ F is excellent in thermal stability, and it is known from the thermal analysis results that it does not show an exothermic reaction even at a high temperature of 400 ° C., and it is possible to prevent the battery temperature from rising.

  Hereinafter, examples embodying the electrolytic solution for lithium ion batteries containing nitrile will be described in more detail.

Example 1
In Example 1, a solvent in which adiponitrile, ethylene carbonate (EC), and dimethyl carbonate (DMC) were mixed at a volume ratio of 50:25:25 was used as the organic solvent, and LiPF ₆ ( Lithium hexafluorophosphate) was dissolved at 0.05 mol / L to obtain an electrolyte for a lithium ion battery.

(Comparative Example 1)
In Comparative Example 1, a mixed solvent of 50% by volume of ethylene carbonate and 50% by volume of dimethyl carbonate was used as the organic solvent, and LiPF ₆ as a lithium salt was dissolved to 1 mol / L to obtain an electrolyte for a lithium ion battery. did.

(Examples 2-9)
In Examples 2 to 9, the solvent was various nitrile: ethylene carbonate: dimethyl carbonate = 50: 25: 25 (volume ratio), and the electrolyte was LiPF ₆ (lithium hexafluorophosphate) at 1 mol / L in this mixed solvent. The so-dissolved solution was used as an electrolyte solution for a lithium ion battery (however, in Example 6 in which the nitrile compound was oxydipropionitrile, LiPF ₆ was 0.5 mol / L).
The types of nitriles used in each example are as follows.
Example 1 Adiponitrile NC (CH ₂ ) ₄ CN
Example 2 Succinonitrile NC (CH ₂ ) ₂ CN
Example 3 Sevacononitrile NC (CH ₂ ) ₈ CN
Example 4 Dodecanedinitrile NC (CH ₂ ) ₁₀ CN
Example 5 2-Methylglutaronitrile NCCH (CH ₃ ) CH ₂ CH ₂ CN
Example 6-oxy dipropionate nitrile _{NCCH 2 CH 2 -O-CH 2} CH 2 CN
EXAMPLE 7 3-methoxy propionitrile _{CH 3 -O-CH 2 CH 2} CN
Example 8 Methyl cyanoacetate NCCH ₂ COOCH ₃
Example 9 cyanoacetate butyl _{NCCH 2 COO (CH 2) 3} CH 3

-Evaluation-
(Measurement of potential-current curve)
With respect to the electrolyte solutions for lithium ion batteries of Examples 1 to 9 and Comparative Example 1 prepared as described above, potential-current curves were measured. A potentiogalvanostat was used for measurement, glassy carbon was used for the working electrode, and a platinum wire was used for the counter electrode. As the reference electrode, (Ag / Ag +) or (Li / Li +) was used. In the measurement, after scanning several times on the positive side and the negative side, the potential was swept from the natural potential in the positive direction or in the negative direction at a speed of 5 mV / sec, and the potential-current curve was measured. The results are shown in FIG. 14, FIG. 15 and FIG.

As a result, as shown in FIG. 14, the potential window of the electrolytic solution of Example 1 was 6.9 V with respect to the Li potential (Li / Li ⁺ ) (the judgment criterion of the potential window was 50 μA / cm ^2, and so on). It became. On the other hand, the potential window of Comparative Example 1 using a mixed solvent of ethylene carbonate and dimethyl carbonate is 5.2 V as shown in FIG. 16, and the potential window of the electrolytic solution of Example 1 is Comparative Example 1. Compared to the electrolyte solution of, it was found that it spreads greatly on the positive side. From this result, when the electrolytic solution of Example 1 is used, a high potential redox positive electrode active material that exists in a region where the potential for charging exceeds 5.2 V can be used as the positive electrode active material of the lithium ion battery. Thus, a lithium ion battery having high electromotive force and energy density and large capacity can be obtained. For example, in the electrolytic solution of Comparative Example 1, the organic solvent undergoes electrolysis even at the redox potential of Li ₂ CoPO ₄ F or Li ₂ NiPO ₄ F, and these positive electrode oxidizing substances cannot be used. If the electrolytic solution of Example 1 is used, not only Li ₂ CoPO ₄ F or Li ₂ NiPO ₄ F can be used as the positive electrode active material, but also LiCoPO ₄ , LiNiPO _4, etc. can be used.

Further, as shown in FIG. 15, in the electrolyte solutions of Examples 2 to 9 as well, as in Example 1, all of the potential windows spread in the positive direction as compared with the electrolyte solution of Comparative Example 1. . From these results, the chain saturated hydrocarbon dinitrile compound (Examples 1 to 5) in which nitrile groups were bonded to both ends of the chain saturated hydrocarbon compound, ethylene carbonate and dimethyl carbonate, the end of the chain ether compound By adding a chain ether nitrile compound (Examples 6 and 7) having at least one nitrile group bonded thereto and at least one nitrile compound (Examples 8 and 9) among cyanoacetic acid esters, the solvent is decomposed to a high potential. It was found that it can exist stably without doing. In particular, the potential window greatly widened in Examples 1 to 5 using a chain saturated hydrocarbon dinitrile compound in which a nitrile group was bonded to both ends of a chain saturated hydrocarbon compound as a nitrile compound, which has branches. Also in Example 5, it was found that the potential window greatly spreads in the positive direction. Also, in Example 6 using oxydipropionitrile NCCH ₂ CH ₂ —O—CH ₂ CH ₂ CN, it was found that the potential window greatly expanded in the positive direction.

(Examples 10 to 17)
In Examples 10 to 17, the solvent was various nitrile: ethylene carbonate: diethyl carbonate = 50: 25: 25 (volume ratio), and the electrolyte was LiPF ₆ (lithium hexafluorophosphate) at 1 mol / L in this mixed solvent. What was dissolved in this way was used as the electrolyte solution for lithium ion batteries (however, in Example 10 in which the nitrile compound was glutaronitrile, LiPF ₆ (lithium hexafluorophosphate) was 0.5 mol / L. ).
The types of nitriles used in each example are as follows.
Example 10 Glutaronitrile NC (CH ₂ ) ₃ CN
Example 11 sebaconitrile NC _{(CH 2)} 8 CN
Example 12 Dodecanedinitrile NC (CH ₂ ) ₁₀ CN
Example 13 2-methylglutaronitrile _{NCCH (CH 3) CH 2 CH} 2 CN
Example 14 oxy dipropionate nitrile _{NCCH 2 CH 2 -O-CH 2} CH 2 CN
Example 15 3-Methoxy-propionitrile _{CH 3 -O-CH 2 CH 2} CN
Example 16 methyl cyanoacetate NCCH ₂ COOCH ₃
Example 17 cyanoacetate butyl _{NCCH 2 COO (CH 2) 3} CH 3

(Comparative Example 2)
In Comparative Example 2, a mixed solvent of ethylene carbonate: diethyl carbonate = 50: 50 (capacity ratio) was used as the organic solvent, and LiPF ₆ was dissolved as a lithium salt to 1 mol / L so as to electrolyze the lithium ion battery. A liquid was used.

-Evaluation-
(Measurement of potential-current curve)
About the electrolyte solution of Examples 10-17 and the comparative example 2, it carried out similarly to the above-mentioned method, and measured the electric potential-current curve. The results are shown in FIG.
From this figure, it was found that in the electrolytic solutions of Examples 10 to 17, the potential window spreads in the positive direction as compared with the electrolytic solution of Comparative Example 2. From this result, even when ethylene carbonate and diethyl carbonate were used as solvents, both of the chain saturated hydrocarbon compounds were the same as when ethylene carbonate and dimethyl carbonate were used as solvents (that is, in the case of Examples 1 to 9). Add at least one nitrile compound among a chain saturated hydrocarbon dinitrile compound having a nitrile group bonded to the terminal, a chain ether nitrile compound having a nitrile group bonded to at least one terminal of the chain ether compound, and a cyanoacetate ester. It was found that the solvent exists stably up to a high potential. In particular, the potential window greatly widened in Examples 10 to 13 using a chain saturated hydrocarbon dinitrile compound in which a nitrile group was bonded to both ends of a chain saturated hydrocarbon compound as a nitrile compound, which has branches. Also in Example 13, it was found that the potential window greatly expanded in the positive direction. Also, in Example 14 and Example 15 using a chain ether nitrile compound in which a nitrile group was bonded to at least one end of the chain ether compound, it was found that the potential window greatly expanded in the positive direction.

(Examples 18 to 25)
In Examples 18 to 25, the solvent was various nitrile: γ-butyrolactone: dimethyl carbonate = 50: 25: 25 (volume ratio), and the electrolyte was LiPF ₆ (lithium hexafluorophosphate) at 1 mol / L in this mixed solvent. What was melt | dissolved so that it might become was used as the electrolyte solution for lithium ion batteries. In the example using adiponitrile as the nitrile, LiPF ₆ was 0.5 mol / L.
The types of nitriles used in each example are as follows.
Example 18 Glutaronitrile NC (CH ₂ ) ₃ CN
Example 19 adiponitrile NC _{(CH 2)} 4 CN
Example 20 sebaconitrile NC _{(CH 2)} 8 CN
Example 21 dodecane dinitrile _{NC (CH 2)} 10 CN
Example 22 2-methylglutaronitrile _{NCCH (CH 3) CH 2 CH} 2 CN
Example 23 oxy dipropionate nitrile _{NCCH 2 CH 2 -O-CH 2} CH 2 CN
Example 24 methyl cyanoacetate NCCH ₂ COOCH ₃
Example 25 cyanoacetate butyl _{NCCH 2 COO (CH 2) 3} CH 3

(Comparative Example 3)
In Comparative Example 3, a mixed solvent of γ-butyrolactone: dimethyl carbonate = 50: 50 (volume ratio) was used as the organic solvent, and LiPF ₆ was dissolved as a lithium salt at 1 mol / L so as to be used for a lithium ion battery. An electrolyte was used.

-Evaluation-
(Measurement of potential-current curve)
For the electrolytic solutions of Examples 18 to 25 and Comparative Example 3, potential-current curves were measured in the same manner as described above. The results are shown in FIG.
From this figure, it was found that also in the electrolyte solutions of Examples 18 to 25, the potential window greatly expanded in the positive direction as compared with the electrolyte solution of Comparative Example 3. From this result, even when dimethyl carbonate and cyclic ester γ-butyrolactone are used as a solvent instead of cyclic carbonate ethylene carbonate, a chain formula in which nitrile groups are bonded to both ends of the chain saturated hydrocarbon compound. It was found that by adding the saturated hydrocarbon dinitrile compound, the solvent exists stably to a high potential. Moreover, it turned out that a potential window spreads in the positive direction greatly not only in Examples 18 to 21 which are linear molecules among chain-type saturated hydrocarbon dinitrile compounds but also in Example 22 having branches. Further, in Example 23 using a chain ether nitrile compound in which a nitrile group is bonded to both ends of the chain ether compound, and in Examples 24 and 25 using cyanoacetate, the potential window is greatly widened in the positive direction. I understood that.

(Examples 26 to 31)
In Examples 26 to 31, the solvent was various nitriles: dimethyl carbonate = 50: 50 (volume ratio), and the electrolyte was LiPF ₆ (lithium hexafluorophosphate) 1 mol / L (Examples 30 and 31). In this case, an electrolyte solution for a lithium ion battery was dissolved so as to be 0.1 mol / L. The types of nitriles used in each example are as follows.
Example 26 glutaronitrile NC _{(CH 2)} 3 CN
Example 27 sebaconitrile NC _{(CH 2)} 8 CN
Example 28 Dodecanedinitrile NC (CH ₂ ) ₁₀ CN
Example 29 2-methylglutaronitrile _{NCCH (CH 3) CH 2 CH} 2 CN
Example 30 oxy dipropionate nitrile _{NCCH 2 CH 2 -O-CH 2} CH 2 CN
Example 31 methyl cyanoacetate NCCH ₂ COOCH ₃

(Comparative Example 4)
In Comparative Example 4, LiPF ₆ as a lithium salt was dissolved in dimethyl carbonate as an organic solvent so as to be 1 mol / L to obtain an electrolytic solution for a lithium ion battery.

-Evaluation-
(Measurement of potential-current curve)
About the electrolyte solution of Examples 26-31 and the comparative example 4, the electric potential-current curve was measured like the above-mentioned method. The results are shown in FIG.
From this figure, in the electrolytic solutions of Examples 26 to 31 in which dimethyl carbonate alone was added in addition to the nitrile compound as a solvent, the potential window was positive in comparison with the electrolytic solution of Comparative Example 3 in which dimethyl carbonate was the sole solvent. I understood that it spreads. It was also found that the solvent was stably present up to a high potential by adding a chain saturated hydrocarbon dinitrile compound having nitrile groups bonded to both ends of the chain saturated hydrocarbon compound (Examples 26 to 29). Furthermore, it was found that, among the chain saturated hydrocarbon dinitrile compounds, not only in Examples 26 to 28 which are linear molecules, but also in Example 29 having branches, the potential window greatly spreads in the positive direction. Furthermore, in Example 30 using a chain ether nitrile compound in which a nitrile group was bonded to both ends of the chain ether compound, the potential window was greatly expanded, and in Example 31 using cyanoacetate, the potential window was expanded.

(Examples 32 and 33)
In Examples 32 and 33, the solvent was various nitrile: propylene carbonate = 50: 50 (volume ratio), and the electrolyte was dissolved in this mixed solvent so that LiPF ₆ (lithium hexafluorophosphate) was 1 mol / L. This was used as an electrolyte for lithium ion batteries. The types of nitriles used in each example are as follows.
Example 32 sebaconitrile NC _{(CH 2)} 8 CN
Example 33 dodecane dinitrile _{NC (CH 2)} 10 CN

(Comparative Example 5)
In Comparative Example 5, an electrolyte solution for a lithium ion battery was prepared by dissolving LiPF ₆ as a lithium salt in propylene carbonate as an organic solvent so as to be 1 mol / L.

-Evaluation-
(Measurement of potential-current curve)
With respect to the electrolytic solutions of Examples 32 and 33 and Comparative Example 5, potential-current curves were measured in the same manner as described above. The results are shown in FIG.
From this figure, in the electrolytic solutions of Examples 32 and 33 in which propylene carbonate alone was added in addition to the nitrile compound as the solvent, the potential window was positive in comparison with the electrolytic solution of Comparative Example 5 in which propylene carbonate was the sole solvent. It was found that it spreads greatly. It was also found that the solvent was stably present up to a high potential by adding a chain saturated hydrocarbon dinitrile compound having nitrile groups bonded to both ends of the chain saturated hydrocarbon compound.

(Examples 34 to 36)
In Examples 34 to 36, the solvent was various nitriles: γ-butyrolactone = 50: 50 (volume ratio), and the electrolyte was dissolved in this mixed solvent so that LiPF ₆ (lithium hexafluorophosphate) was 1 mol / L. This was used as an electrolyte for a lithium ion battery. The types of nitriles used in each example are as follows.
Example 34 glutaronitrile NC _{(CH 2)} 3 CN
Example 35 sebaconitrile NC _{(CH 2)} 8 CN
Example 36 dodecane dinitrile _{NC (CH 2)} 10 CN

(Comparative Example 6)
In Comparative Example 6, an electrolyte solution for a lithium ion battery was prepared by dissolving LiPF ₆ as a lithium salt in γ-butyrolactone as an organic solvent so as to be 0.1 mol / L.

-Evaluation-
(Measurement of potential-current curve)
For the electrolytic solutions of Examples 34 to 36 and Comparative Example 6, potential-current curves were measured in the same manner as described above. The results are shown in FIG.
From this figure, in the electrolytic solutions of Examples 34 to 36 in which γ-butyrolactone was added alone as a solvent in addition to the nitrile compound, the potential window was larger than that of the electrolytic solution of Comparative Example 5 in which γ-butyrolactone was the sole solvent. It turns out that it spreads greatly in the positive direction. It was also found that the solvent was stably present up to a high potential by adding a chain saturated hydrocarbon dinitrile compound having nitrile groups bonded to both ends of the chain saturated hydrocarbon compound.

(Examples 37 to 39)
In Examples 37 to 39, the solvent is various nitrile: ethylene carbonate: γ-butyrolactone = 50: 25: 25 (volume ratio), and the electrolyte is LiPF ₆ (lithium hexafluorophosphate) at 1 mol / L in this mixed solvent. What was melt | dissolved so that it might become was used as the electrolyte solution for lithium ion batteries. The types of nitriles used in each example are as follows.
Example 37 sebaconitrile NC _{(CH 2)} 8 CN
Example 38 2-methylglutaronitrile _{NCCH (CH 3) CH 2 CH} 2 CN
Example 39 oxy dipropionate nitrile _{NCCH 2 CH 2 -O-CH 2} CH 2 CN

(Comparative Example 7)
In Comparative Example 7, an electrolyte solution for a lithium ion battery was prepared by dissolving LiPF ₆ as a lithium salt in ethylene carbonate: γ-butyrolactone = 50: 50 (volume ratio) as an organic solvent so as to be 1 mol / L.

-Evaluation-
(Measurement of potential-current curve)
About the electrolyte solution of Examples 37-39 and the comparative example 7, the electric potential-current curve was measured like the above-mentioned method. The results are shown in FIG.
From this figure, in the electrolytic solutions of Examples 37 to 39 in which ethylene carbonate, which is a cyclic carbonate, and γ-butyrolactone, which is a cyclic ester, were added as solvents in addition to the nitrile compound, the nitrile compound was not added. It was found that the potential window spreads greatly in the positive and negative directions as compared with the electrolyte. It was also found that the solvent was stably present up to a high potential by adding a chain saturated hydrocarbon dinitrile compound having nitrile groups bonded to both ends of the chain saturated hydrocarbon compound. Furthermore, it was found that, among the chain-type saturated hydrocarbon dinitrile compounds, not only in Example 37, which is a linear molecule, but also in Example 38 having branches, the potential window greatly spreads in the positive and negative directions. Further, in Example 39 using a chain ether nitrile compound in which a nitrile group was bonded to both ends of the chain ether compound, the potential window was greatly widened in the positive and negative directions.

(Examples 40 to 44)
In Examples 40 to 44, the solvent was sebacononitrile (adiponitrile in Example 42): ethylene carbonate: dimethyl carbonate = 50: 25: 25 (volume ratio), and various electrolytes were dissolved in this mixed solvent so as to be 1 mol / L. This was used as an electrolyte for a lithium ion battery. The types of electrolyte used in each example are as follows.
Example 40 LiPF ₆
Example 41 LiTFSI
Example 42 LiTFSI
Example 43 LiBF ₄
Example 44 LiBETI

(Example 45)
In Example 45, a solvent in which sebacononitrile, ethylene carbonate (EC), and dimethyl carbonate (DMC) were mixed at a volume ratio of 50:25:25 was used as the organic solvent, and LiPF ₆ ( Lithium hexafluorophosphate) was dissolved at 0.05 mol / L and LiTFSI (lithium bis (trifluoromethanesulfonyl) imide) was dissolved at 1.0 mol / L to obtain an electrolyte for a lithium ion battery.

(Example 46)
In Example 46, a solvent in which butyl cyanoacetate, ethylene carbonate (EC), and dimethyl carbonate (DMC) were mixed at a volume ratio of 50:25:25 as an organic solvent, and LiTFSI as a lithium salt was used. (Lithium bis (trifluoromethanesulfonyl) imide) was dissolved at 1.0 mol / L to obtain an electrolytic solution for a lithium ion battery.

(Example 47)
In Example 47, a solvent obtained by mixing butyl cyanoacetate, ethylene carbonate (EC), and dimethyl carbonate (DMC) in a volume ratio of 50:25:25 as an organic solvent, and LiBF as a lithium salt was used. ₄ (lithium tetrafluoroborate) was dissolved at 1.0 mol / L to obtain an electrolyte for a lithium ion battery.

(Comparative Examples 8 to 10)
In Comparative Examples 8 to 10, various lithium salts were added instead of LiPF ₆ which is the lithium salt in Comparative Example 1. That is, various lithium salts (LiTFSI in Comparative Example 8, LiBF ₄ in Comparative Example 9, LiBETI in Comparative Example 10) at 1 mol / L as an organic solvent, ethylene carbonate: dimethyl carbonate = 50: 50 (volume ratio). It was made to melt | dissolve and it was set as the electrolyte solution for lithium ion batteries.

-Evaluation-
(Measurement of potential-current curve)
With respect to the electrolytic solutions of Examples 40 to 44, Comparative Example 1 and Comparative Examples 8 to 10, potential-current curves were measured in the same manner as described above. The results are shown in FIG. In addition, Table 1 shows the value of the potential obtained from this figure when the current density is 50 μA / cm ² .
From FIG. 23 and Table 1, in the electrolytic solutions of Examples 40 to 44 in which ethylene carbonate, which is a cyclic carbonate, and dimethyl carbonate, which is a chain carbonate, are added as solvents in addition to the nitrile compound, regardless of the type of electrolyte. It was found that the potential window greatly expanded in the positive direction as compared with the electrolytic solutions of Comparative Example 1 and Comparative Examples 8 to 10 in which no nitrile compound was added.
The potential window of the electrolytic solution of Example 45 is 6.6 V (see FIG. 24), the potential window of the electrolytic solution of Example 46 is 5.4 V (see FIG. 25), and the potential window of the electrolytic solution of Example 47 is It became 6.1V (refer FIG. 26), and it turned out that all have spread to the positive side.

Similarly, the lithium salt and LiPF _6, the electrolyte of the other examples and comparative examples, the potential - was determined from current curve, shown in Table 2 an electrode potential when a predetermined current density. From this table, a chain saturated hydrocarbon dinitrile compound having a nitrile group bonded to both ends of the chain saturated hydrocarbon compound, a chain ether nitrile compound having a nitrile group bonded to at least one of the ends of the chain ether compound, and cyano It can be seen that the potential window widens in the positive direction when at least one nitrile compound of the acetic ester and at least one of cyclic carbonate, cyclic ester and chain carbonate are contained.

<Influence of nitrile addition amount>
In order to investigate the influence of the addition amount of nitrile in the electrolytic solution of the present invention, a predetermined amount of sebacononitrile was added to a mixed solvent of ethylene carbonate: dimethyl carbonate = 1: 1 (volume ratio), and a potential-current curve was measured. Incidentally, the electrolyte was added LiPF ₆ as a 1M (However, in the case of sebaconitrile 100% by volume, it was 0.1M for dissolution of 1M was difficult). The results are shown in FIG. From this figure, it was found that the amount of sebacononitrile added had the effect of expanding the potential window even at 1% by volume, and the potential window expanded in the higher potential direction as the amount added increased. However, when 100% by volume of sebacononitrile is used, the solubility of LiPF ₆ that is an electrolyte is lowered and the viscosity is also increased. Therefore, there is a problem that the conductivity is lowered and the internal resistance of the battery is increased. For this reason, the preferable amount of sebacononitrile added as an electrolyte for a lithium battery is 1% by volume or more and less than 100% by volume, more preferably 5% by volume or more and less than 90% by volume, and most preferably 30% by volume or more and 70% by volume. %.

  As described above, in the potential-current curve for the electrolytic solution of the example, it was found that the potential window greatly expanded in the positive direction by adding the nitrile compound to the organic solvent. In the measurement of the potential-current curve of the above example, as described above, after scanning several times on the positive side and the negative side, the potential is swept at a rate of 5 mV / sec from the natural potential in the positive direction or the negative direction. And the potential-current curve is measured. In the potential scan several times before this measurement, the potential window spreads after the second time. Therefore, by sweeping the potential in the positive direction in the electrolytic solution of the present invention, an electrode having a wide potential window is formed. It can be seen that it can be manufactured.

From the above, the following matters are disclosed.
(1) an immersion step of immersing the electrode in an organic solvent containing a nitrile compound;
And a positive voltage applying step for applying a potential higher than the potential that can be applied when the electrode is immersed in a liquid containing only the organic solvent that does not contain the nitrile compound after the immersion step. Electrode processing method.
(2) The method for treating an electrode according to (1), wherein the high potential is more than 5.2 V, preferably 6.0 V or more with respect to the (Li / Li ⁺ ) reference electrode.
(3) The nitrile compound is a chain saturated hydrocarbon dinitrile compound in which a nitrile group is bonded to both ends of a chain saturated hydrocarbon compound, or a chain ether nitrile in which a nitrile group is bonded to at least one end of a chain ether compound. At least one of a compound and a cyanoacetic acid ester,
The electrode processing method according to (2), wherein the electrode is made of carbon.
(4) A chain saturated hydrocarbon dinitrile compound having a nitrile group bonded to both ends of a chain saturated hydrocarbon compound, a chain ether nitrile compound having a nitrile group bonded to at least one terminal of the chain ether compound, and cyanoacetic acid An immersion step of immersing the electrode in an organic solvent containing a nitrile compound that is at least one of the esters;
And a positive voltage applying step of applying a positive voltage to the electrode after the immersion step.

<Measurement of battery characteristics>
In order to evaluate the performance of the electrolyte solution for lithium ion batteries of the present invention as a battery, a potential-current curve was measured using a cathode for a lithium battery and a cathode for a lithium battery.
That is, the electrolyte solution for lithium ion battery of Example 41 (that is, EC: DMC: sebacononitrile = 25: 25: 50 by volume ratio, LiTFSI (lithium bis (trifluoromethanesulfonyl) imide) as a lithium salt was 1.0 mol / L), and a lithium battery cathode and a lithium battery anode were used as working electrodes, and a potential-current curve of lithium occlusion / release was measured. The cathode for a lithium battery using _Li 4 _Ti 5 O1 _2, as a positive electrode for a lithium battery using LiCoO ₂ and LiCoPO _4. A potentiogalvanostat was used for the measurement. Further, (Ag / Ag ⁺ ) was used as the reference electrode. In the measurement, after scanning several times on the positive side and the negative side, the potential was swept from the natural potential in the positive direction or in the negative direction at a speed of 0.5 mV / sec, and the potential-current curve was measured.

As a result, as shown in FIG. 28, Li ₄ Ti ₅ O ₁₂ as the cathode for the lithium battery, LiCoO ₂ and LiCoPO ₄ as the cathode for the lithium battery, both lithium (0) and lithium ions A nearly reversible current associated with redox was observed. From this result, it was found that by using the lithium ion battery electrolyte of Example 4, smooth charge / discharge between lithium (0) and lithium ions was possible.

<Production of sodium ion battery>
By using a positive electrode, a negative electrode, and an electrolytic solution for a sodium ion battery instead of the lithium ion battery, a sodium ion battery having extremely excellent corrosion resistance can be obtained.

  As described above, the current collector of the present invention can be applied to lithium ion batteries and sodium ion batteries. These ion batteries include an electrolytic solution, a positive electrode, a negative electrode, a separator, and a case.

<Lithium ion battery>
(Electrolyte)
The electrolyte solution of a lithium ion battery contains Li salt (electrolyte) and an organic solvent.
As the Li salt, a general Li salt for a Li ion battery can be used. For example, LiPF ₆ (lithium hexafluorophosphate), LiBF ₄ (lithium tetrafluoroborate), LiTFSI (lithium bis (trifluoromethanesulfonyl) imide), LiTFS (lithium trifluoromethanesulfonate), LiBETI (lithium bis ( Pentafluoroethanesulfonyl) imide) or two or more thereof can be used.
Among them, for those redox potential of the positive electrode is more than 4.5V, it is preferable to use LiPF _6, and / or LiBF _4. In the case of using a LiTFSI and LiTFS and LiBETI, it is preferable to add LiPF ₆ or LiBF _4.

As the organic solvent, a general solvent used for a Li ion battery can be adopted. Such an organic solvent is preferably one or more selected from cyclic carbonates, cyclic carboxylic acid esters and chain carbonates. More preferably, a cyclic carbonate and a chain carbonate are used in combination. Specifically, it is particularly preferable to use ethylene carbonate and dimethyl carbonate in combination. The blending ratio of both is not particularly limited. As the cyclic carboxylic acid ester, γ-butyrolactone can be used.
Furthermore, a nitrile compound can be used as an organic solvent. Here, as the nitrile compound, a chain saturated hydrocarbon dinitrile compound in which a nitrile group is bonded to both ends of a chain saturated hydrocarbon compound, a chain ether in which a nitrile group is bonded to at least one terminal of a chain ether compound. Mention may be made of at least one nitrile compound among nitrile compounds and cyanoacetic acid esters.

Examples of the chain saturated hydrocarbon dinitrile compound in which nitrile groups are bonded to both ends of the chain saturated hydrocarbon compound include succinonitrile NC (CH ₂ ) ₂ CN, glutaronitrile NC (CH ₂ ) ₃ CN, adiponitrile In addition to linear dinitrile compounds such as NC (CH ₂ ) ₄ CN, sebaconitrile NC (CH ₂ ) ₈ CN, dodecanedinitrile NC (CH ₂ ) ₁₀ CN, 2-methylglutaronitrile NCCH (CH ₃ ) _CH 2 _CH 2 CN may have a branched as such. These chain saturated hydrocarbon dinitrile compounds are not particularly limited in carbon number, but are preferably 20 or less. More preferably, it is 7-12.

Examples of the chain ether nitrile compound in which a nitrile group is bonded to at least one end of the chain ether compound include oxydipropionitrile NCCH ₂ CH ₂ —O—CH ₂ CH ₂ CN and 3-methoxypropionitrile CH _{3. -O-CH} 2 CH 2 CN, and the like. These chain ether nitrile compounds are not particularly limited in carbon number, but are preferably 20 or less.
Examples of cyanoacetic acid esters include methyl cyanoacetate, ethyl cyanoacetate, propyl cyanoacetate, and butyl cyanoacetate. These cyanoacetic acid esters are not particularly limited in carbon number, but are preferably 20 or less.

These nitrile compounds have the effect of expanding the potential window particularly in the positive direction in the electrolytic solution.
A dinitrile compound is preferable from the viewpoint of the action of expanding the potential window. Of these, the use of sebacononitrile is more preferable.
However, since a nitrile compound has high viscosity, it is preferable to use together with the above-mentioned chain carbonate ester, cyclic carbonate ester, and / or cyclic carboxylic acid ester. More preferably, a nitrile compound, a chain carbonate ester and a cyclic carbonate ester are used in combination. Dimethyl carbonate can be employed as the chain carbonate, and ethylene carbonate can be employed as the cyclic carbonate.
In this case, the blending ratio of the nitrile compound in the whole organic solvent is preferably 1 to 90% by volume. More preferably, it is 5-70 volume%, More preferably, it is 10-50 volume%.

  The concentration of the Li salt is 0.01 mol / L or more and is lower than the saturated state. When the concentration of the Li salt is less than 0.01 mol / L, ion conduction by Li ions is reduced, and the electric resistance of the electrolytic solution is increased, which is not preferable. On the other hand, exceeding the saturation state is not preferable because the dissolved Li salt precipitates due to environmental changes such as temperature.

(Positive electrode)
The positive electrode includes a positive electrode active material and a current collector.
(Positive electrode active material)
The positive electrode active material refers to “a material in which lithium is inserted / extracted in the crystal structure at a higher potential than the negative electrode, and oxidation / reduction is performed accordingly”.
Examples of the positive electrode active material include (1) an oxide system, (2) a phosphate system having an olivine type crystal structure, and (3) an olivine fluoride system.
Since the current collector of the present invention is excellent in corrosion resistance at a high potential, a lithium ion battery using a phosphate-based or olivine fluoride-based positive electrode active material having an olivine-type crystal structure that is charged and discharged at a high potential Is effective.

(1) Oxide-based 1-1 specific substances As oxide-based materials, Li _1-x CoO ₂ (x = 0 to 1: layered structure), Li _1-x NiO ₂ (x = 0 to ₁ : layered structure) ), Li _1-x Mn ₂ O ₄ (x = 0 to 1: spinel structure), Li _2−y MnO ₃ (y = 0 to 2) and their solid solutions (herein, solid solutions are those of the above oxide series) A substance in which metal atoms are mixed in a free ratio in the positive electrode active material. Moreover, what doped the metal atom of these with the other metal atom is also contained. The dopant is not particularly limited as long as the electrochemical characteristics can be changed in the oxidation-reduction reaction. For example, one or more of Li, Mg, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo can be used.
1-2 Characteristics The general discharge potential of this positive electrode active material is less than 5 V (vs Li / Li ⁺ ). However, LiNi _0.5 Mn _1.5 O ₄ partially substituted with Ni in the LiMn ₂ O ₄ system has a discharge potential of 4.7 V, and takes into account overvoltage when performing rapid charging, and 5 V May require a charging voltage exceeding. Further, since LiCoMnO ₄ starts with a discharge voltage of about 5.2V, the charge voltage also exceeds 5V. In addition, oxide systems generally decompose at less than 300 ° C., and have a relatively large exothermic reaction as oxygen is generated. Therefore, a control circuit that does not cause overcharging is required.

(2) Phosphate-based 2-1 specific substance having olivine-type crystal structure As phosphate-based substances having olivine-type crystal structure, Li _1-x NiPO ₄ (x = 0 to ₁ ), Li _1-x CoPO ₄ (x = 0 to ₁ ), Li _1-x MnPO ₄ (x = 0 to ₁ ), Li _1-x FePO ₄ (x = 0 to 1) and their solid solutions (herein the solid solution is the above-mentioned phosphorus In the acid salt positive electrode active material, it refers to a material in which metal atoms are mixed in a free ratio. Moreover, what doped the metal atom of these with the other metal atom is also contained. The dopant is not particularly limited as long as the electrochemical characteristics can be changed in the oxidation-reduction reaction. For example, one or more of Mg, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo can be used (see JP 2008-130525 A).
2-2 Characteristics The oxidation-reduction potential of this positive electrode active material is attracting attention because, unlike the above oxide system, if it is less than 300 ° C., the exothermic reaction is small, oxygen is not generated, and safety is high. Of the phosphate systems, the LiCoPO ₄ system has a discharge potential of about 4.8 V, and an electrolyte having a withstand voltage of 5 V or more is required for rapid charging. It is suggested that the discharge potential of LiNiPO ₄ is 5.2 V (vs Li / Li ⁺ ).

(3) Olivine fluoride system 3-1 Specific substances Li _2-x NiPO ₄ F (x = 0-2), Li _2-x CoPO ₄ F (x = 0-2) are known, and other Li _{2 -x MnPO 4 F (x = 0~2} ), Li 2-x FePO 4 F (x = 0~2) are considered.
Further, these solid solutions (herein, the solid solution refers to a material in which metal atoms are mixed in a free ratio in the olivine fluoride-based positive electrode active material) can also be mentioned. Furthermore, the thing which doped the metal atom of these with another metal atom is also contained. The dopant is not particularly limited as long as the electrochemical characteristics can be changed in the oxidation-reduction reaction. For example, one or more of Mg, Al, Ti, V, Mn, Fe, Co, Ni, Cu, Zn, Zr, Nb, and Mo can be used.
3-2 Characteristics Similar to the olivine system, the redox potential of this positive electrode active material is different from that of the above oxide system. The effect of battery ignition is considered to be small, and is attracting attention in terms of safety. Moreover, the electric capacity density (mAh / g) of a battery can be made higher than the said phosphate system (refer Unexamined-Japanese-Patent No. 2003-229126). However, for example, the Li ₂ CoPO ₄ F system has an average discharge potential of about 4.8 V, and an electrolytic solution having a withstand voltage of 5 V or more is required for rapid charging. Further, the discharge potential of the Li ₂ NiPO ₄ F system is about 5.2 V (vs Li / Li ⁺ ), and an electrolytic solution having a withstand voltage at 5 V or more is required.

(4) Others In addition, lithium-free FeF ₃ , a conjugated polymer using an organic conductive material, a chevrel phase compound, or the like can also be used. In addition, transition metal chalcogenides, vanadium oxides and lithium salts thereof, niobium oxides and lithium salts thereof, and a plurality of different positive electrode active materials may be used in combination.
The average particle diameter of the positive electrode active material particles is not particularly limited, but is preferably 10 nm to 30 μm.

(Current collector for positive electrode)
The positive electrode current collector is a conductive substrate carrying a positive electrode active material.
The molding material for the current collector of the positive electrode is preferably stable during charging. In particular, when using a phosphate-based and olivine fluoride-based positive electrode active material having an olivine-type crystal structure with a high redox potential, it is preferable to use a material excellent in corrosion resistance.
The shape and structure of the current collector can be arbitrarily designed according to the structure of the positive electrode active material and the battery.

(Pretreatment of positive electrode)
The positive electrode for a lithium ion battery performs an immersion treatment step of immersing the positive electrode in a pretreatment electrolytic solution in which a lithium salt is dissolved in an organic solvent containing 1% by volume or more of a nitrile compound before being incorporated in the lithium ion battery, Further, a positive voltage processing step for applying a positive voltage to the electrode is performed. The electrode thus pretreated has a wide potential window even when used in an electrolyte solution containing no nitrile compound or in a lithium ion battery using an electrolyte solution with a small amount of nitrile compound added. It becomes difficult to disassemble (see Japanese Patent Application No. 2009-180007). The reason why the electrode has such a wide potential window is presumed to be that a corrosion-resistant film containing nitrogen as a component is formed on the electrode.

(Negative electrode)
The negative electrode includes a negative electrode active material and a current collector.
(Negative electrode active material)
The negative electrode active material refers to “a material in which lithium is inserted / extracted in the crystal structure at a lower potential than the positive electrode, and oxidation / reduction is performed accordingly”.
Examples of the negative electrode active material include various carbon materials such as artificial graphite, natural graphite, and hard carbon, lithium titanate (Li ₄ Ti ₅ O ₁₂ ), H ₂ Ti ₁₂ O ₂₅ , H ₂ Ti ₆ O ₁₃ , Fe ₂ O ₃ etc. are mentioned. Moreover, the composite material which mixed these suitably can also be mentioned. Furthermore, there may be mentioned Si fine particles and Si thin films, and fine particles and thin films in which these Si are Si-based alloys such as Si—Ni, Si—Cu, Si—Nb, Si—Zn, Si—Sn. Further, SiO oxide, Si-SiO ₂ composite, Si-SiO ₂ - can be given complex, etc., such as carbon.

(Current collector for negative electrode)
The current collector for the negative electrode can be formed of a general-purpose conductive metal material, Cu, Al, Ni, Ti, austenitic stainless steel, or the like.
However, when a nitrile compound is used for the electrolytic solution (including combined use with other organic solvents), it is necessary to select appropriately according to the Li salt in the electrolytic solution. That is, when LiPF ₆ or LiBF ₄ is used as the electrolyte, austenitic stainless steel, Ni, Al, Ti, or the like can be used. However, it is necessary to select appropriately according to the operating potential of the negative electrode active material to be used. In the case of using carbon or Si as the negative electrode active material, when LiBF ₄ is used as the electrolyte, a current collector made of Al, Ni, Ti, austenitic stainless or the like other than Cu can be used. In the case where lithium titanate or a Fe ₂ O ₃ based compound is used as the negative electrode active material, all of the above materials containing Cu are applicable. On the other hand, when LiPF _{6 is} used as the electrolyte, Al, Ni and Ti are preferable, and austenitic stainless steel and Cu are not preferable. In addition, when LiTFSI, LiBETI, or LiTFS is used as the electrolyte, any of Ni, Ti, Al, Cu, and austenitic stainless steel can be used.

(Electroconductive member for positive electrode)
Some positive electrode active materials have low electrical conductivity. Therefore, it is preferable to provide a sufficient electron conduction path between the positive electrode active material and the current collector by interposing a conductive electron conduction member.
Here, the shape of the electron conducting member is not particularly limited as long as an electron conduction path can be formed between the positive electrode active material and the current collector. For example, carbon black such as acetylene black, graphite powder, conductive diamond-like carbon Further, conductive powder (conductive aid) such as glassy carbon can be used. Conductive diamond-like carbon and glassy carbon have a much wider potential window than carbon black and graphite, and are excellent in corrosion resistance when a high potential is applied, and therefore can be suitably used. Moreover, it is also preferable that metal fine particles are supported on these conductive assistants. Examples of the metal fine particles include Pt, Au, Ni and the like. These may be used alone or an alloy thereof.
As the electron conductive material, a conductive film ( conductive DLC film or the like) covering the positive electrode active material or a conductive thin film (gold thin film or the like) in which the positive electrode active material is embedded can be used.
In particular, since the Li ₂ NiPO ₄ F-based positive electrode active material has low conductivity of its own and / or its surface coating, it does not function as a positive electrode of a lithium ion battery if it is simply supported on a current collector. There is a case. In order to evaluate the performance of the Li ₂ NiPO ₄ F-based positive electrode active material, it can be physically driven into a conductive thin film such as gold with a hammer or the like to form the positive electrode of the battery.
Here, the Li ₂ NiPO ₄ F-based positive electrode active material refers to Li ₂ NiPO ₄ F and a material appropriately doped with dopant.

(Electroconductive member for negative electrode)
The thing similar to the electron conductive member for positive electrodes can be used.

(Separator)
The separator is immersed in the electrolytic solution, separates the positive electrode and the negative electrode, prevents a short circuit therebetween, and allows the passage of Li ions.
Examples of such separators include porous films made of polyolefin resins such as polyethylene and polypropylene.

(Case)
The case is formed of a material having corrosion resistance against the electrolytic solution. The shape can be arbitrarily designed according to the intended use of the battery.
When the case also serves as a current collector or is electrically coupled to the current collector, the current collector of the present invention can be used as the current collector.

<Sodium ion battery>
(Electrolyte)
The electrolyte of the sodium ion battery contains Na salt (electrolyte) and an organic solvent.
As the Na salt, those conventionally known as Na salts for Na ion batteries can be used. For example, for example, NaClO ₄ , NaPF ₆ , NaBF ₄ , NaCF ₃ SO ₃ , NaN (CF ₃ SO ₂ ) ₂ , NaN (FSO ₂ ) ₂ , NaN (C ₂ F ₅ SO ₂ ) ₂ , NaC (CF ₃ SO ₂ ) ₃ etc. are mentioned. The mixing ratio of the solvent and the solute is not particularly limited and is appropriately set according to the purpose.
Moreover, it is also preferable to add about 0.1 to 3% of various additives (for example, vinylene carbonate, fluoroethylene carbonate, ethylene sulfite). Thereby, a corrosion-resistant film is formed on the negative electrode side, and the corrosion resistance is improved.

As the organic solvent, a general one used for a Na ion battery can be adopted. As such an organic solvent, one kind or two or more kinds selected from cyclic carbonates, cyclic carboxylic acid esters and chain carbonates are preferable. More preferably, a cyclic carbonate and a chain carbonate are used in combination. Specifically, it is particularly preferable to use ethylene carbonate and dimethyl carbonate in combination. The blending ratio of both is not particularly limited. As the cyclic carboxylic acid ester, γ-butyrolactone or propylene carbonate can be used.
As the chain carbonate, in addition to dimethyl carbonate, diethyl carbonate or ethyl methyl carbonate can be used.
Furthermore, a nitrile compound can be used as an organic solvent. Here, as the nitrile compound, a chain saturated hydrocarbon dinitrile compound in which a nitrile group is bonded to both ends of a chain saturated hydrocarbon compound, a chain ether in which a nitrile group is bonded to at least one terminal of a chain ether compound. Mention may be made of at least one nitrile compound among nitrile compounds and cyanoacetic acid esters.

Examples of the chain saturated hydrocarbon dinitrile compound in which nitrile groups are bonded to both ends of the chain saturated hydrocarbon compound include succinonitrile NC (CH ₂ ) ₂ CN, glutaronitrile NC (CH ₂ ) ₃ CN, adiponitrile In addition to linear dinitrile compounds such as NC (CH ₂ ) ₄ CN, sebaconitrile NC (CH ₂ ) ₈ CN, dodecanedinitrile NC (CH ₂ ) ₁₀ CN, 2-methylglutaronitrile NCCH (CH ₃ ) _CH 2 _CH 2 CN may have a branched as such. These chain saturated hydrocarbon dinitrile compounds are not particularly limited in carbon number, but are preferably 7 to 20. More preferably, it is 10-12.

Examples of the chain ether nitrile compound in which a nitrile group is bonded to at least one end of the chain ether compound include oxydipropionitrile NCCH ₂ CH ₂ —O—CH ₂ CH ₂ CN and 3-methoxypropionitrile CH _{3. -O-CH} 2 CH 2 CN, and the like. These chain ether nitrile compounds are not particularly limited in carbon number, but are preferably 20 or less.
Examples of cyanoacetic acid esters include methyl cyanoacetate, ethyl cyanoacetate, propyl cyanoacetate, and butyl cyanoacetate. These cyanoacetic acid esters are not particularly limited in carbon number, but are preferably 20 or less.

These nitrile compounds have the effect of expanding the potential window particularly in the positive direction in the electrolytic solution.
A dinitrile compound is preferable from the viewpoint of the action of expanding the potential window. Of these, the use of sebacononitrile is more preferable.
However, since a nitrile compound has high viscosity, it is preferable to use together with the above-mentioned chain carbonate ester, cyclic carbonate ester, and / or cyclic carboxylic acid ester. More preferably, a nitrile compound, a chain carbonate ester and a cyclic carbonate ester are used in combination. Dimethyl carbonate can be employed as the chain carbonate, and ethylene carbonate can be employed as the cyclic carbonate.
In this case, the blending ratio of the nitrile compound in the whole organic solvent is preferably 1 to 90% by volume. More preferably, it is 15-70 volume%, More preferably, it is 30-50 volume%.

  The concentration of Na salt is 0.01 mol / L or more, which is lower than the saturated state. If the concentration of Na salt is less than 0.01 mol / L, ion conduction due to Na ions is reduced, and the electric resistance of the electrolytic solution is increased, which is not preferable. On the other hand, exceeding the saturated state is not preferable because a dissolved Na salt is precipitated due to environmental changes such as temperature.

(Positive electrode)
The positive electrode includes a positive electrode active material and a current collector.
The positive electrode active material refers to a “substance that can be reversibly oxidized and reduced by charge and discharge as a positive electrode of a secondary battery”. Further, the positive electrode active material of the sodium ion battery is required to be a material capable of reversibly intercalating and deintercalating sodium ions.
Examples of such a positive electrode active material include NaFeO ₂ , NaNiO ₂ , NaCoO ₂ , NaMnO ₂ , NaFe _1-x M ¹ _x O ₂ , and NaNi _1-x M ¹ _{x described in} JP2009-129741A. O ₂ , NaCo _1-x M ¹ _x O ₂ , NaMn _1-x M ¹ _x O ₂ (where M ¹ is one or more elements selected from the group consisting of trivalent metals, and 0 ≦ x <0 .5)) and the like. Among these, a composite oxide mainly containing iron and sodium, and using a composite oxide having a hexagonal crystal structure as a positive electrode active material, a high discharge voltage can be obtained. A secondary battery having a high density can be obtained.

More preferably, the positive electrode active material is a composite oxide mainly containing iron and sodium, has a hexagonal crystal structure, and has an interplanar spacing of 2 in the X-ray diffraction analysis of the composite oxide. A complex oxide having a value obtained by dividing the intensity of a peak of 20 angstroms by the intensity of a peak of 5.36 angstroms in plane spacing is 2 or less. In heating a metal compound mixture containing a sodium compound and an iron compound in a temperature range of 400 ° C. or more and 900 ° C. or less, the atmosphere is heated as an inert atmosphere in a temperature range of less than 100 ° C. during the temperature increase. Is preferred.
Moreover, what doped the transition metal atom of these compounds with the other metal atom may be used. The dopant is not particularly limited as long as the electrochemical characteristics can be changed in the oxidation-reduction reaction.

(Pretreatment of positive electrode)
The positive electrode for a sodium ion battery is subjected to an immersion treatment step of immersing the positive electrode in a pretreatment electrolyte solution in which a sodium salt is dissolved in an organic solvent containing 1% by volume or more of a nitrile compound before being incorporated in the sodium ion battery, Furthermore, a positive voltage processing step of applying a positive voltage to the electrodes can be performed. The electrode thus pretreated has a wide potential window even when used in an electrolyte solution containing no nitrile compound or an electrolyte solution with a small amount of nitrile compound added. It becomes difficult to disassemble. The reason why the electrode has such a wide potential window is presumed to be that a corrosion-resistant film containing nitrogen as a component is formed on the electrode.

(Negative electrode)
The negative electrode includes a negative electrode active material and a current collector.
The negative electrode active material is “a material capable of reversibly repeating oxidation-reduction while sodium ions enter and exit by charging and discharging as a negative electrode of a secondary battery”. For example, Li ₄ Ti ₅ O ₁₂ can be used.

(Electroconductive member for positive electrode)
Some positive electrode active materials have low electrical conductivity. Therefore, it is preferable to provide a sufficient electron conduction path between the positive electrode active material and the current collector by interposing a conductive electron conduction member.
Here, the shape of the electron conducting member is not particularly limited as long as an electron conduction path can be formed between the positive electrode active material and the current collector. For example, carbon black such as acetylene black, graphite powder, conductive diamond-like carbon Further, conductive powder (conductive aid) such as glassy carbon can be used. Conductive diamond-like carbon and glassy carbon have a much wider potential window than carbon black and graphite, and are excellent in corrosion resistance when a high potential is applied, and therefore can be suitably used. Moreover, it is also preferable that metal particles for electrochemical reaction are supported on these conductive assistants. Examples of the metal include Pt, Ru, Rh, Pd, Ag, Ir, Au, Ni, and Cu. These may be used alone or an alloy thereof.
As the electron conductive material, a conductive film ( conductive DLC film or the like) covering the positive electrode active material or a conductive thin film (gold thin film or the like) in which the positive electrode active material is embedded can be used.
In particular, since the conductivity of the positive electrode active material itself and / or its surface coating is small, if it is simply supported on the current collector and does not function as the positive electrode of a sodium ion battery, the positive electrode active material For performance evaluation, this can be physically driven into a conductive thin film such as gold with a hammer or the like to form the positive electrode of the battery.

(Electroconductive member for negative electrode)
The thing similar to the electron conductive member for positive electrodes can be used.

(Separator)
The separator is immersed in the electrolytic solution, separates the positive electrode and the negative electrode to prevent a short circuit therebetween, and allows the passage of Na ions.
Examples of such separators include porous films made of polyolefin resins such as polyethylene and polypropylene.

(Case)
The case is formed of a material having corrosion resistance against the electrolytic solution. The shape can be arbitrarily designed according to the intended use of the battery.
When the case also serves as a current collector or is electrically coupled to the current collector, the current collector of the present invention can be used as the current collector.

  The present invention is not limited to the description of the embodiment of the invention. Various modifications may be included in the present invention as long as those skilled in the art can easily conceive without departing from the description of the scope of claims.

DESCRIPTION OF SYMBOLS 1 ... Current collector base material 2 ... Corrosion-resistant film 3 ... Defect 4 ... Passive film 9, 10 ... Current collector

Claims (3)

A positive electrode having a current collector base material comprising aluminum, nickel, or titanium as a main component or a current collector base material made of austenitic stainless steel; and a battery electrolyte; ⁺ ) In the above secondary batteries,
The collector base material surface of the positive electrode is coated with a corrosion-resistant film made of conductive diamond-like carbon ,
The battery electrolyte contains an organic solvent containing nitrile, and when the corrosion resistant film has a defect, further contains at least one of BF ₄ anion and PF ₆ anion,
The conductive diamond-like carbon is conductive among carbons having an amorphous structure in which both diamond bonds (SP ₃ hybrid orbital bonds between carbons) and graphite bonds (SP ₂ hybrid orbital bonds between carbons ) are mixed. In addition to the amorphous structure, it has a phase partially composed of a crystal structure composed of a graphite structure ( hexagonal crystal structure composed of SP ₂ hybrid orbital bonds), thereby making it electrically conductive. Secondary batteries , including those that exhibit The secondary battery of claim 1 wherein the battery electrolyte solution including at least one of LiPF ₆ and LiBF ₄ as an electrolyte, it is characterized. A current collector having a corrosion-resistant film made of conductive diamond-like carbon formed on the surface of a current collector base made of aluminum, nickel or titanium as a main component or a positive electrode current collector made of austenitic stainless steel When,
A secondary battery having a charging potential of 5 V (vs Li / Li ⁺ ) or more,
The battery electrolyte contains an organic solvent,
The conductive diamond-like carbon is conductive among carbons having an amorphous structure in which both diamond bonds (SP ₃ hybrid orbital bonds between carbons) and graphite bonds (SP ₂ hybrid orbital bonds between carbons ) are mixed. In addition to the amorphous structure, it has a phase partially composed of a crystal structure composed of a graphite structure ( hexagonal crystal structure composed of SP ₂ hybrid orbital bonds), thereby making it electrically conductive. Including those where
Dipping the current collector in the electrolyte containing nitrile and at least one of BF ₄ anion and PF ₆ anion, and sweeping the potential so that a positive potential capable of forming a passive film is applied to the current collector. A method for producing a secondary battery, comprising:

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