JP4484205B2 - Organic electrolyte battery - Google Patents

Description

  The present invention relates to an organic electrolyte battery, and more particularly to an organic electrolyte battery having excellent cycle characteristics and excellent high-temperature storage characteristics.

Organic electrolyte batteries represented by lithium ion secondary batteries are in high demand because of their high voltage and high energy density. Conventionally, in this organic electrolyte battery, a carbon material such as graphite is used as a negative electrode active material, and the carbon material as the negative electrode active material is formed as a negative electrode active material-containing coating on a conductive substrate made of metal foil or the like together with a binder. Is used. In recent years, graphite having high crystallinity has been used as a carbon material for the negative electrode active material in order to increase the capacity.
JP 05-307958 A

  However, a carbon material with high crystallinity has a large volume change due to charge and discharge, and as a result, the binding property between the carbon materials and between the carbon material and the conductive substrate made of metal foil or the like is lowered, and the cycle characteristics are lowered. There was a problem to do.

In order to enable large current discharge, it has also been proposed to increase the specific surface area of the carbon material used as the negative electrode active material.
Japanese Patent Laid-Open No. 06-295725

  However, when the specific surface area is increased, large current discharge becomes possible and load characteristics are improved, but there is a problem that when the battery is stored at a high temperature in a charged state, it reacts with the electrolytic solution, resulting in a large decrease in capacity. .

  The present invention eliminates the problems in the conventional organic electrolyte battery as described above, and achieves a high capacity. Therefore, even when a carbon material having high crystallinity and a large specific surface area is used as the negative electrode active material. An object of the present invention is to provide an organic electrolyte battery having excellent cycle characteristics and excellent high-temperature storage characteristics.

The present invention has been made to achieve the above object, and in an organic electrolyte battery including a negative electrode, a positive electrode, and an organic electrolyte, lithium having a specific surface area of 3.0 m ² / g or more as a negative electrode active material. Atom obtained from a peak of 286 to 287 eV based on a carbon atom bonded to a hydroxyl group and an oxygen atom derived from a C—O bond in an X-ray photoelectron spectroscopic analysis of the carbon material By making the amount of 10 to 20 atomic% to 10 atomic%, an organic electrolyte battery having excellent cycle characteristics and high-temperature storage characteristics is obtained to solve the above problems.

  Further, in the present invention, the above-mentioned carbon material has a preferable embodiment in which the contents of Zn and Cu by ICP emission analysis are each 15 ppm or less and the content of Fe is 100 ppm or less.

  Furthermore, in this invention, it is set as the preferable aspect that the content of Cl by the fluorescent X-ray analysis is 70 ppm or less regarding the said carbon material.

In addition, in this invention, the quantity of the carbon atom calculated | required from the peak of 286-287 eV based on the carbon atom couple | bonded with the hydroxyl group and the oxygen atom derived from CO bond in the X-ray photoelectron spectroscopy analysis of carbon material is carbon material. Is measured using an Al-Kα ray at 400 W using “PHI5500MC” manufactured by ULVAC-PHI Co., Ltd., peak splitting is performed, and the amount of atoms in each peak is expressed as a percentage (%) of all constituent atoms. It is calculated.

  In addition, the contents of Zn, Cu, and Fe by ICP emission analysis are as follows. About 5 g of carbon material is precisely weighed, placed in a 200 ml beaker, 100 ml of (1 + 1) hydrochloric acid is added, and the solution is heated and concentrated until the liquid volume is about 20-25 ml. After cooling, the quantitative filter paper No. No. The carbon material was separated at 5B, and the filtrate and washing solution were placed in a 100 ml volumetric flask and diluted at a constant volume, and then measured using a sequential type ICP emission analyzer IPIS1000 manufactured by Japan Jarrell-Ash.

  The Cl content of the carbon material by fluorescence X-ray analysis was measured using a fluorescent X-ray analyzer “ZSX100e” manufactured by Rigaku Corporation on a sample obtained by molding the carbon material into a pellet.

  According to the present invention, in order to achieve high capacity, even when a carbon material having high crystallinity and a large specific surface area is used as the negative electrode active material, cycle characteristics are excellent and high-temperature storage characteristics are excellent. An organic electrolyte battery can be provided.

In the present invention, as the carbon material capable of occluding and releasing lithium having a specific surface area of 3.0 m ² / g or more used as the negative electrode active material, for example, a carbon material having a turbulent layer structure, natural graphite, artificial graphite, glassy Examples thereof include carbon materials such as carbon. Some of these do not contain lithium at the time of production, but when acting as a negative electrode active material, they are in a state containing lithium by chemical means or electrochemical means.

The carbon material has an amount of carbon atoms determined from a peak of 286 to 287 eV based on carbon atoms bonded to hydroxyl atoms and oxygen atoms derived from C—O bonds in X-ray photoelectron spectroscopic analysis. Although it is necessary to be at most atomic%, this is based on the following reasons. That is, when the amount of carbon atoms obtained from a peak of 286 to 287 eV based on carbon atoms bonded to hydroxyl atoms and oxygen atoms derived from C—O bonds in the X-ray photoelectron spectroscopy of the carbon material is less than 10 atomic% Can not sufficiently enhance the binding between the carbon material of the negative electrode active material or between the carbon material and the conductive substrate made of metal foil, etc. In addition, when the amount of the carbon atom is more than 20 atomic%, the SEI (Solid Electrolyte Interface) film on the negative electrode surface becomes unstable, resulting in capacity deterioration during high-temperature storage. . And as a quantity of the carbon atom calculated | required from the peak of 286-287 eV based on the carbon atom couple | bonded with the hydroxyl atom and the oxygen atom derived from CO bond in the X-ray photoelectron spectroscopy of this carbon material, 12 atomic% or more 20 atomic% or less is more preferable.

Prior to the completion of the present invention, the present inventors examined the cause of cycle deterioration of an organic electrolyte battery using a conventional highly crystalline carbon material as a negative electrode active material. The volume change due to charging / discharging is large, and repeated charging / discharging cycles over a long period of time may reduce the binding capacity between the carbon materials and between the carbon material and the conductive substrate made of metal foil, etc. I found out that it was a cause. On the other hand, in the present invention, the negative electrode active material is a lithium material capable of occluding and releasing lithium having a specific surface area of 3.0 m ² / g or more, and its hydroxyl group and C—O bond in X-ray photoelectron spectroscopy analysis. Cycle characteristics and high-temperature storage characteristics are excellent by using carbon atoms in an amount of 10 to 20 atom% determined from a peak of 286 to 287 eV based on a carbon atom bonded to a derived oxygen atom. An organic electrolyte battery has been obtained. This is because the presence of carbon atoms bonded to the hydroxyl groups and oxygen atoms derived from C—O bonds leads to a conductive substrate made of a carbon material binder or metal foil. Even if the affinity is improved and the charge / discharge cycle is repeated over a long period of time, the binding property between the carbon materials or between the carbon material and the conductive substrate made of metal foil, etc. is lowered. That the it is considered to be due to be inhibited.

In the present invention, the amount of carbon atoms determined from a peak of 286 to 287 eV based on a carbon atom bonded to a hydroxyl group and an oxygen atom derived from a C—O bond in X-ray photoelectron spectroscopy used as a negative electrode active material is 10 atomic%. The carbon material of 20 atomic% or less can be obtained by treating the carbon material with a solution of a compound such as oxalic acid or carboxymethyl cellulose. As a specific means, for example, a carbon material having a specific surface area of 3.0 m ² / g or more is immersed in an oxalic acid aqueous solution and the like, followed by heating and drying.

  Further, in the present invention, the carbon material used as the negative electrode active material has a Zn content of 15 ppm or less, a Cu content of 15 ppm or less, and an Fe content of 100 ppm or less by ICP emission analysis. Is preferred. This is because such a carbon material can further improve the cycle characteristics. The reason for this is not necessarily clear at present. However, side reactions caused by Zn, Cu, Fe, and their compounds are caused by keeping the contents of Zn, Cu, and Fe below a specific value as described above. This is considered to be suppressed. As is clear from this, the contents of these Zn, Cu, and Fe are preferably small, the contents of Zn and Cu are more preferably 10 ppm or less, and the content of Fe is more preferably 50 ppm or less. preferable.

  Furthermore, in the present invention, the carbon material used as the negative electrode active material preferably has a CI content of 70 ppm or less by fluorescence X-ray analysis. This is because the cycle characteristics are further improved when the Cl content of the carbon material is 70 ppm or less by fluorescent X-ray analysis. The reason for this is not necessarily clear at present, but by suppressing the amount of Cl in the carbon material below such a specific value, Cl contained in the carbon material and its compounds can be prevented from causing side reactions. It is thought that it is because it comes to be done. As apparent from this, the content of Cl in the carbon material is preferably as small as possible, and more preferably 50 ppm or less.

In the present invention, the carbon material used as the negative electrode active material needs to have a specific surface area of 3.0 m ² / g or more. This is to obtain a high capacity organic electrolyte battery, and 3.4 m ^2. / g or more, although the specific surface area is suitable for high capacity as large, since there is a tendency that too large the preparation of later negative electrode active material-containing coating, such as a difficult, 5.0 m ² / g or less is preferable.

  The negative electrode is, for example, a negative electrode active material made of the above carbon material, if necessary, a binder, and if necessary, an electron conduction aid, a solvent, and mixing to mix the negative electrode active material-containing paint. The coating material is prepared, applied to a conductive substrate, and dried to form a negative electrode active material-containing coating film. In preparing the negative electrode active material-containing paint, the binder is preferably used as a solution previously dissolved in an organic solvent, water, or an aqueous solution, and mixed with solid particles such as the negative electrode active material to prepare the paint.

  As the binder, for example, a polyvinylidene fluoride polymer (a polymer of a fluorine-containing monomer group containing 80% by mass or more of vinylidene fluoride as a main component monomer), a rubber polymer, a cellulose polymer, and the like are preferably used. It is done. You may mix and use the said polymer.

  Examples of the fluorine-containing monomer group containing 80% by mass or more of vinylidene fluoride as a main component monomer in the synthesis of the polyvinylidene fluoride-based polymer include, for example, vinylidene fluoride alone, or vinylidene fluoride and other A mixture with at least one of the monomers may be mentioned. Examples of the other monomer include vinyl fluoride, trifluoroethylene, trifluorochloroethylene, tetrafluoroethylene, hexafluoropropylene, and fluoroalkyl vinyl ether.

  Examples of the rubber-based polymer include styrene butadiene rubber, ethylene propylene diene rubber, and fluorine rubber.

  Examples of the cellulose polymer include carboxymethyl cellulose, methyl cellulose, ethyl cellulose, hydroxypropyl cellulose, hydroxyethyl methyl cellulose, and hydroxypropyl methyl cellulose.

  In this invention, it is preferable that a binder is 0.2-20 mass% in a negative electrode active material containing coating film, and it is especially preferable that it is 0.5-10 mass%. When the binder content is less than the above range, the negative electrode active material-containing coating film may be insufficient in mechanical strength, and the negative electrode active material-containing coating film may be peeled off from the conductive substrate. When more than the said range, there exists a possibility that the negative electrode active material in a negative electrode active material containing coating film may reduce, and battery capacity may fall.

  In addition, as the electron conduction aid, for example, flaky graphite, carbon black, ketjen black, acetylene black, carbon fiber and the like are preferably used.

  In the present invention, various coating methods such as an extrusion coater, a reverse roller, a doctor blade, and an applicator can be employed as a coating method when the negative electrode active material-containing paint is applied to a conductive substrate. .

  Further, as the negative electrode conductive substrate, for example, a metal, a punched metal, a foam metal, a foil processed into a plate shape, or the like made of a metal conductive material such as aluminum, stainless steel, titanium, or copper is used.

In the present invention, in constituting a positive electrode serving as a counter electrode of the negative electrode, as the positive electrode active material, for example, lithium nickel oxide, lithium cobalt oxide, lithium manganese oxide (these are usually LiNiO ₂ , LiCoO ₂ , Although represented by LiMn ₂ O ₄ , the ratio of Li to Ni, the ratio of Li to Co, and the ratio of Li to Mn often deviate slightly from the stoichiometric composition, but such a slight deviation Lithium-containing composite metal oxides such as may be used alone or as a mixture of two or more thereof or as a solid solution thereof.

  The positive electrode includes, for example, the above-described positive electrode active material, and optionally includes an electron conduction assistant such as flaky graphite and carbon black, and further prepares a positive electrode active material-containing paint containing a binder, and the paint is made conductive. It is produced through a process of applying to a substrate and drying to form a coating film containing a positive electrode active material.

  In the production of this positive electrode, the same materials as in the case of the negative electrode can be used for the binder, the electron conduction auxiliary agent, the conductive substrate, and the negative electrode active material can be applied with respect to the coating method of the positive electrode active material-containing paint. The same method as in the case of applying the substance-containing paint can be employed.

In the present invention, an electrolytic solution in which an electrolyte such as a lithium salt is dissolved in an organic solvent is used. Examples of the electrolyte include a general formula LiMF _n (wherein M is P, As, Sb or B). And n is 6 when M is P, As or Sb, and 4 when M is B). Can be used alone or in combination of two or more.

  The concentration of the electrolyte in the electrolytic solution is preferably 0.4 mol / l to 1.6 mol / l as a whole even when two or more different types of electrolytes are included, and particularly 0.6 mol / l to 1 It is preferably 4 mol / l.

  Examples of the organic solvent used for dissolving the electrolyte include ethers such as 1,2-dimethoxyethane, 1.2-diethoxyethane, dimethoxypropane, 1,3-dioxolane, tetrahydrofuran, and 2-methyltetrahydrofuran. , Propylene carbonate, ethylene carbonate, γ-butyrolactone, esters such as diethyl carbonate, dimethyl carbonate, and ethyl methyl carbonate, and sulfolane are used alone or as a mixed solvent of two or more.

  Among the above organic solvents, esters are preferable because they have little reactivity with the positive electrode active material even under a high voltage and have a large effect of improving storage characteristics. This ester is preferably 20% by volume or more in the total electrolytic solution solvent for the stability of the electrolytic solution during charging.

  As the separator, for example, a microporous polyethylene film or a microporous polypropylene film having a thickness of 10 to 50 μm and a porosity of 30 to 70% is preferably used.

  The battery is made of, for example, a spiral electrode body manufactured by winding a separator between a positive electrode and a negative electrode manufactured as described above, and aluminum, aluminum alloy, or nickel-plated iron. It is manufactured through a process of inserting into a battery case made of stainless steel or the like, injecting an electrolyte, and sealing. The battery usually incorporates an explosion-proof mechanism that discharges gas generated inside the battery to a certain pressure to the outside of the battery to prevent the battery from bursting under high pressure.

  Next, the present invention will be described more specifically with reference to examples. However, this invention is not limited only to those Examples.

Example 1
The negative electrode used in Example 1 was produced as follows. First, graphite having a specific surface area of 3.0 m ² / g was immersed in a 0.1 mass% oxalic acid aqueous solution for 30 minutes, washed with water, and then vacuum-dried at 100 ° C. for 3 hours. The amount of carbon atoms determined from a peak of 286 to 287 eV based on a carbon atom bonded to a hydroxyl group and an oxygen atom derived from a C—O bond by X-ray photoelectron spectroscopy analysis of the graphite was 12 atomic%. Further, the content of Zn by ICP emission analysis of the above graphite was 5 ppm, the content of Cu was 4 ppm, the content of Fe was 30 ppm, and the content of Cl by fluorescence X-ray analysis was 36 ppm.

  98 parts by mass of graphite, a suspension of styrene butadiene rubber as a binder and a 1.5% by mass carboxymethyl cellulose aqueous solution were mixed so that the solid content was 1 part by mass (2 parts by mass as a whole binder). A negative electrode active material-containing coating was prepared.

The obtained negative electrode active material-containing coating was applied on a conductive substrate made of a copper foil having a thickness of 8 μm using an applicator and dried at 100 ° C. to form a negative electrode active material-containing coating film. In addition, the coating material was applied to the back side of the conductive substrate made of the copper foil in the same manner as described above, and dried to prepare an electrode body. Thereafter, this electrode body was vacuum-dried at 100 ° C. for 10 hours and then roll-pressed to produce a sheet-like negative electrode. The total thickness of the negative electrode at this time was 125 μm, and the density of the negative electrode active material-containing coating film was 1.7 g / cm ³ .

  A positive electrode serving as a counter electrode of the negative electrode was produced as follows. First, 96 parts by weight of lithium cobalt oxide, 1 part by weight of carbon black and scaly graphite as electron conduction assistants, and 2 parts by weight of polyvinylidene fluoride as binder are added to N-methylpyrrolidone. The dissolved material was mixed to prepare a positive electrode active material-containing paint.

The obtained coating material was applied onto a conductive substrate made of an aluminum foil having a thickness of 15 μm using an applicator and dried at 100 to 120 ° C. to form a coating film containing a positive electrode active material. In addition, the coating material was applied to the back side of the conductive substrate made of the aluminum foil in the same manner as described above and dried to prepare an electrode body. The electrode body was vacuum-dried at 100 ° C. for 10 hours and then roll-pressed to produce a sheet-like positive electrode. The total thickness of the positive electrode at this time was 130 μm, and the density of the positive electrode active material-containing coating film was 3.8 g / cm ³ .

As the electrolytic solution, a solution in which LiPF ₆ was dissolved in a mixed solvent having a volume ratio of ethylene carbonate and methyl ethyl carbonate of 1: 2 to a concentration of 1.0 mol / l was used.

  A current collecting tab is attached to each of the sheet-like positive electrode and the sheet-like negative electrode, and the sheet-like positive electrode and the sheet-like negative electrode are overlapped via a separator made of a microporous polyethylene film having a thickness of 20 μm and wound in a spiral shape. After turning, pressurize to make a flat shape and make an electrode laminate with a flat wound structure, then attach an insulating tape, and a rectangular battery case with an outer dimension of 5 mm x 30 mm x 48 mm [thickness (depth) 5 mm , 30 mm wide and 48 mm high rectangular battery case], the lead body is welded, and the sealing lid plate is laser welded to the opening end of the battery case, and the electrolyte provided on the sealing lid plate After injecting the above electrolyte into the battery case from the inlet and sufficiently infiltrating the separator, etc., the electrolyte inlet is sealed and sealed, and then precharged and aged. 1 To produce an organic electrolyte secondary battery of prismatic having an appearance as shown in FIG. 2 in Suyo structure.

  The battery shown in FIGS. 1 and 2 will now be described. The positive electrode 1 and the negative electrode 2 are spirally wound through the separator 3 as described above, and then pressed so as to be flattened, thereby forming a flat winding structure. The electrode laminate 6 is housed in the rectangular battery case 4 together with the electrolyte solution. However, in FIG. 1, in order to avoid complication, a metal foil, an electrolytic solution, or the like as a conductive substrate used in manufacturing the positive electrode 1 and the negative electrode 2 is not illustrated.

  The battery case 4 is made of an aluminum alloy and constitutes a battery exterior material. The battery case 4 also serves as a positive electrode terminal. An insulator 5 made of a polytetrafluoroethylene sheet is disposed at the bottom of the battery case 4, and the positive electrode 1 and the negative electrode are formed from the flat electrode structure 6 made of the positive electrode 1, the negative electrode 2 and the separator 3. A positive electrode lead body 7 and a negative electrode lead body 8 connected to one end of each of the two are drawn out. A stainless steel terminal 11 is attached to an aluminum alloy cover plate 9 that seals the opening of the battery case 4 via a polypropylene insulating packing 10, and an insulator 12 is connected to the terminal 11. A stainless steel lead plate 13 is attached.

  And this cover plate 9 is inserted in the opening part of the said battery case 4, and the opening part of the battery case 4 is sealed by welding the junction part of both, and the inside of a battery is sealed.

  In the battery of Example 1, the battery case 4 and the cover plate 9 function as positive terminals by directly welding the positive electrode lead body 7 to the cover plate 9, and the negative electrode lead body 8 is welded to the lead plate 13, The terminal 11 functions as a negative electrode terminal by conducting the negative electrode lead body 8 and the terminal 11 through the lead plate 13, but depending on the material of the battery case 4, the sign may be reversed. There is also.

  FIG. 2 is a perspective view schematically showing the external appearance of the battery shown in FIG. 1. FIG. 2 is shown for the purpose of showing that the battery is a square battery. FIG. 1 schematically shows a battery, and only specific members of the battery are shown. Also in FIG. 1, the inner peripheral portion of the electrode body is not cross-sectional.

Example 2
The same treatment as in Example 1 was carried out except that the concentration of the oxalic acid aqueous solution for introducing carbon atoms bonded to oxygen atoms derived from C—O bonds into graphite was 0.5 mass%. The amount of carbon atoms determined from a peak of 286 to 287 eV based on carbon atoms bonded to hydroxyl groups and oxygen atoms derived from C—O bonds by X-ray photoelectron spectroscopy analysis of the graphite after oxalic acid treatment is 18 atomic%. there were. Further, the content of Zn by ICP emission analysis of the above graphite was 5 ppm, the content of Cu was 4 ppm, the content of Fe was 30 ppm, and the content of Cl by fluorescent X-ray analysis was 36 ppm. Then, a square organic electrolyte secondary battery was produced in the same manner as in Example 1 except that graphite having the above characteristics was used as the negative electrode active material.

Example 3
Using graphite with a specific surface area of 3.6 m ² / g, instead of oxalic acid treatment, a 1.5% by mass aqueous carboxymethyl cellulose solution was added so that the amount of carboxymethyl cellulose was 0.5 parts by mass with respect to graphite. After mixing and stirring for 3 hours, it was vacuum dried at 400 ° C. for 10 hours. The amount of carbon atoms determined from a peak of 286 to 287 eV based on carbon atoms bonded to hydroxyl groups and oxygen atoms derived from C—O bonds by X-ray photoelectron spectroscopy of the graphite thus treated is 15 atomic%. there were. Further, the content of Zn by ICP emission analysis of the graphite was 9 ppm, the content of Cu was 6 ppm, the content of Fe was 82 ppm, and the content of Cl by fluorescent X-ray analysis was 65 ppm. Then, a square organic electrolyte secondary battery was produced in the same manner as in Example 1 except that graphite having the above characteristics was used as the negative electrode active material.

Example 4
Oxalic acid treatment was performed in the same manner as in Example 1 except that graphite having a specific surface area of 3.7 m ² / g was used. The amount of carbon atoms determined from a peak of 286 to 287 eV based on a carbon atom bonded to a hydroxyl group and an oxygen atom derived from a C—O bond by X-ray photoelectron spectroscopy analysis of the graphite after the oxalic acid treatment is 17 atomic%. there were. Further, the content of Zn by ICP emission analysis of the above graphite was 9 ppm, the content of Cu was 6 ppm, the content of Fe was 90 ppm, and the content of Cl by fluorescent X-ray analysis was 35 ppm. Then, a square organic electrolyte secondary battery was produced in the same manner as in Example 1 except that graphite having the above characteristics was used as the negative electrode active material.

Example 5
The same treatment as in Example 1 was performed, except that graphite having a specific surface area of 4.0 m ² / g was used, and 0.05 mass% oxalic acid aqueous solution was used. The amount of carbon atoms determined from a peak of 286 to 287 eV based on carbon atoms bonded to hydroxyl groups and oxygen atoms derived from C—O bonds by X-ray photoelectron spectroscopy of graphite after oxalic acid treatment is 14 atomic%. there were. Further, the content of Zn by ICP emission analysis of the above graphite was 11 ppm, the content of Cu was 15 ppm, the content of Fe was 94 ppm, and the content of Cl by fluorescent X-ray analysis was 65 ppm. Then, a square organic electrolyte secondary battery was produced in the same manner as in Example 1 except that graphite having the above characteristics was used as the negative electrode active material.

Example 6
The same oxalic acid treatment as in Example 1 was performed except that graphite having a specific surface area of 4.3 m ² / g was used. The amount of carbon atoms determined from a peak of 286 to 287 eV based on carbon atoms bonded to hydroxyl groups and oxygen atoms derived from C—O bonds by X-ray photoelectron spectroscopy of graphite after oxalic acid treatment is 19 atomic%. there were. Further, the content of Zn by ICP emission analysis of the above graphite was 14 ppm, the content of Cu was 5 ppm, the content of Fe was 92 ppm, and the content of Cl by fluorescent X-ray analysis was 60 ppm. A square organic electrolyte secondary battery was produced in the same manner as in Example 1 except that graphite having the above characteristics was used as the negative electrode active material.

Comparative Example 1
The graphite having a specific surface area of 3.0 m ² / g as in Example 1 was used as it was without being treated with oxalic acid. The amount of carbon atoms determined from a peak of 286 to 287 eV based on a carbon atom bonded to a hydroxyl group and an oxygen atom derived from a C—O bond by X-ray photoelectron spectroscopy analysis of this graphite was 7 atomic%. Further, the content of Zn by ICP emission analysis of the above graphite was 4 ppm, the content of Cu was 4 ppm, the content of Fe was 56 ppm, and the content of Cl by fluorescent X-ray analysis was 26 ppm. Then, a rectangular organic electrolyte secondary battery was produced in the same manner as in Example 1 except that graphite having the above characteristics was used as the negative electrode active material.

Comparative Example 2
Graphite having a specific surface area of 3.2 m ² / g was immersed in a 0.5 mass% oxalic acid aqueous solution for 30 minutes, washed with water, and then vacuum-dried at 100 ° C. for 1 hour. The amount of carbon atoms determined from a peak of 286 to 287 eV based on carbon atoms bonded to hydroxyl groups and oxygen atoms derived from C—O bonds by X-ray photoelectron spectroscopy analysis of the graphite after oxalic acid treatment is 22 atomic%. there were. The graphite contained 5 ppm, Cu contained 3 ppm, Fe contained 67 ppm according to the fluorescent X-ray analysis, and Cl contained 40 ppm according to the fluorescent X-ray analysis. It was. Then, a rectangular organic electrolyte secondary battery was produced in the same manner as in Example 1 except that graphite having the above characteristics was used as the negative electrode active material.

Comparative Example 3
Graphite having a specific surface area of ^2.5 m ² / g was immersed in a 0.1 wt% oxalic acid aqueous solution for 30 minutes, washed with water, and then vacuum-dried at 100 ° C. for 3 hours. The amount of carbon atoms determined from a peak of 286 to 287 eV based on carbon atoms bonded to hydroxyl groups and oxygen atoms derived from C—O bonds by X-ray photoelectron spectroscopy of graphite after the oxalic acid treatment is 11 atomic%. there were. Further, the Zn content by ICP emission analysis was 7 ppm, the Cu content was 4 ppm, the Fe content was 82 ppm, and the Cl content by fluorescence X-ray analysis was 37 ppm. Then, a rectangular organic electrolyte secondary battery was produced in the same manner as in Example 1 except that graphite having the above characteristics was used as the negative electrode active material.

  For the batteries of Examples 1 to 6 and Comparative Examples 1 to 3 manufactured as described above, when the charge / discharge current is indicated by C, a current limiting circuit of 1 C is provided with 750 mA as 1 C, and a constant voltage of 4.2 V The battery was first charged and then discharged to 3.0V.

  Table 1 shows the cycle characteristics (%) obtained by multiplying the value obtained by dividing the discharge capacity at the 500th cycle by the discharge capacity at the first cycle in the repetition of charging and discharging of the battery at this time. Moreover, 2C discharge was performed in the 100th cycle, and 1C discharge was performed again from the 101st cycle. Table 1 shows the load characteristics (%) obtained by multiplying the value obtained by dividing the discharge capacity at the 100th cycle by the discharge capacity at the 101st cycle and multiplying by 100.

  Moreover, in the repetition of the said charging / discharging, after charging for the 11th cycle, it stored for 20 days in a 60 degreeC thermostat, cooled to room temperature, discharged, and measured the capacity | capacitance. Table 1 shows a value obtained by multiplying the discharge capacity after storage by the discharge capacity at the 10th cycle of repeated charge and discharge, multiplied by 100, as high-temperature storage characteristics (%).

  As is clear from the comparison between the characteristics of the batteries of Examples 1 to 6 shown in Table 1 and the characteristics of the batteries of Comparative Examples 1 to 3, the batteries of Examples 1 to 6 have cycle characteristics, load characteristics, and high temperature storage characteristics. Both were excellent.

On the other hand, the battery of Comparative Example 1 is obtained from the peak of 286 to 287 eV based on the carbon atom bonded to the hydroxyl atom and the oxygen atom derived from the C—O bond in the X-ray photoelectron spectroscopic analysis of graphite used as the negative electrode active material. The amount of carbon atoms produced is 7 atomic%, which is less than the range of 10 atomic% to 20 atomic% specified in the present invention, so that the cycle characteristics are worse than the batteries of Examples 1 to 6, and the battery of Comparative Example 2 is The amount of carbon atoms determined from the peak of 286 to 287 eV based on the carbon atom bonded to the hydroxyl atom and the oxygen atom derived from the C—O bond in X-ray photoelectron spectroscopy analysis of graphite used as the negative electrode active material is 22 atomic%. Since there are more than the range of 10 atomic% or more and 20 atomic% or less prescribed | regulated by invention, a high temperature storage characteristic is bad compared with the battery of Examples 1-6, and the battery of the comparative example 3 is, Since specific surface area of the graphite used as electrode active material is less than the provision that 3.0 m 2 / ^g or more as defined in the 2.5 m 2 / ^g and the present invention, load characteristics deteriorate in comparison with the batteries of Examples 1 to 6 High capacity could not be achieved.

It is a figure which shows typically an example of the organic electrolyte secondary battery which concerns on this invention, (a) is the top view, (b) is the fragmentary longitudinal cross-sectional view. It is a perspective view of the organic electrolyte secondary battery shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Battery case 5 Insulator 6 Electrode laminated body 7 Positive electrode lead body 8 Negative electrode lead body 9 Cover plate 11 Terminal 12 Insulator 13 Lead plate

Claims (3)

An organic electrolyte battery including a negative electrode, a positive electrode, and an organic electrolyte, wherein a carbon material capable of occluding and releasing lithium having a specific surface area of 3.0 m ² / g or more is used as a negative electrode active material. The amount of carbon atoms determined from a peak of 286 to 287 eV based on a carbon atom bonded to a hydroxyl group and an oxygen atom derived from a C—O bond in X-ray photoelectron spectroscopy is 10 atom% or more and 20 atom% or less. An organic electrolyte battery characterized.
2. The organic electrolyte according to claim 1, wherein the content of Zn and Cu by ICP emission analysis of the carbon material is 15 ppm or less, and the content of Fe by ICP emission analysis of the carbon material is 100 ppm or less. battery. 2. The organic electrolyte battery according to claim 1, wherein the carbon material has a Cl content of 70 ppm or less as determined by fluorescent X-ray analysis.

Images