JPH0815082B2 - Non-aqueous secondary battery and negative electrode material for non-aqueous secondary battery - Google Patents

Description

Detailed Description of the Invention

[0001]

The present invention relates to a non-aqueous secondary battery and a non -aqueous secondary battery.
The present invention relates to a negative electrode material for a water-based secondary battery , and more specifically to improvement of coke which is a negative electrode material for the purpose of increasing battery capacity.

[0002]

2. Description of the Related Art Conventionally, the problems to be solved by the invention
As a negative electrode material for a non-aqueous secondary battery, coke has been proposed as a material that replaces conventional lithium metal because of its excellent flexibility and the fact that mossy lithium is not likely to be electrodeposited.

In a non-aqueous secondary battery, coke occludes lithium in the pores or between layers during charging and releases the occluded lithium during discharging, so to speak, a negative electrode for giving and receiving lithium ions during charging and discharging. It functions as the host on the side.

The capacity of coke per unit weight is usually 200 to 250 mA, regardless of whether it is petroleum-based coke such as pitch coke or coal-based coke.
It is about h / g, and it is hard to say that it has a sufficient capacity as a negative electrode material for a non-aqueous secondary battery in which a long charging interval is required, and storage characteristics and cycle characteristics are also sufficiently satisfactory. It is hard to say that it has some characteristics.

The reason why the characteristics of the coke as a negative electrode material are not good is as follows. That is, in the case of industrially producing coke, the carbon material that is a raw material in the calcination step is 1200 to 1400 ° in a rotary kiln.
Although it is calcined at a temperature of C, since the heating at this time is performed by burning the combustible gas, oxygen such as a hydroxyl group, a carbonyl group and a carboxyl group generated by decomposition of the combustible gas at the time of combustion is formed on the surface of the coke. A large number of contained functional groups will be bound inevitably.

The crystal structure of coke is its d _002.
Value (d value in the lattice plane (002) plane) and Lc (size of crystallite in the c-axis direction), the crystal surface is in a transitional stage before it develops into a graphite crystal. In particular, there are many active points such as unpaired electrons and radicals at the ends.

The small capacity of the negative electrode is because the lithium occluded by the initial charge binds to the oxygen-containing functional group and the active site and is trapped (fixed) on them, so that the electric charge during the subsequent charge / discharge is reduced. This is because the amount of lithium that can participate in the chemical reaction decreases. In addition, the electrolytic solution is decomposed by the oxygen-containing functional groups and active points, and the generated decomposition gas hinders smooth occlusion / release of lithium in the coke during charging / discharging, which is another cause of the small negative electrode capacity.

Further, the storage characteristics and cycle characteristics are not good because the electrolytic solution is contacted with oxygen-containing functional groups and active points and reacts with each other, so that the electrolytic solution is self-discharged or the electrolytic solution is discharged during repeated charge / discharge cycles. This is because it will deteriorate.

The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a non-aqueous secondary battery having a large battery capacity and excellent storage characteristics and cycle characteristics, and to use it. Another object of the present invention is to provide a negative electrode material for a non-aqueous secondary battery .

[0010]

In order to achieve the above object, a non-aqueous secondary battery according to the present invention (hereinafter referred to as "invention battery") has an alkali metal or alkaline earth metal as an oxygen-containing functional group. And coke bound to the active site, thereby suppressing the reactivity of the oxygen-containing functional group and the active site, is used as the negative electrode material. Also,
The negative electrode material for a non-aqueous secondary battery according to the present invention is made of alkaline gold.
Genus or alkaline earth metal as an oxygen-containing functional group and active site
Is bound to the oxygen-containing functional group and the activity.
It consists of coke in which the reactivity of the points is suppressed.

In the present invention, an alkali metal or an alkaline earth metal is used as a metal bonded to the oxygen-containing functional group and the active site in order to suppress the reactivity of the functional group.
This is because these metals do not easily impair the characteristics of coke as a negative electrode material. However, the content of these is 1
If it exceeds 000 ppm, the above-mentioned characteristics may be impaired, so it is preferable to suppress the content to less than that.

As a method for binding an alkali metal or an alkaline earth metal to an oxygen-containing functional group and an active site, an alkali (a hydroxide of an alkali metal or an alkaline earth metal) or an alkali salt (a nitrate, a sulfate, a chloride) is used. , Acetate, etc.)
Examples of the method include immersing coke in a solution obtained by dissolving a coke in a solvent or a melt thereof.

The amount of solution or melt required for a given amount of coke to be treated depends on the amount of oxygen-containing functional groups and active sites in the coke, ie the type of coke to be treated. The more oxygen-containing functional groups and active sites there are, the more solution or melt is required.

When coke having a large amount of free alkali metal ions or alkaline earth metal ions remaining therein is used as a negative electrode material, these ions hinder the smooth movement of lithium ions in the charge / discharge reaction. Content of those metals in coke is 10,000p
Excess solution or melt is preferably removed by filtration and washing so as to be pm or less.

The solvent for dissolving the alkali is not particularly limited, but it is convenient to use water. However, when coke with residual water is used as a negative electrode material, water reacts with lithium to hinder battery characteristics. Therefore, when water is used as a solvent, it is necessary to sufficiently dry it to remove it. . The same applies when water is used as the washing liquid during filtration.

The binding reaction by the above-mentioned treatment originally proceeds rapidly at room temperature, but oxygen-containing functional groups and active sites present on the surface of the pores inside the coke are perceived by the solution and melt as they permeate there. Since it takes a considerable amount of time, it is usually preferable to perform the treatment for about 24 hours under normal pressure. In addition, if a surfactant or alcohol is added to increase the permeability and the treatment is performed under reduced pressure or pressure,
It is also possible to shorten the processing time.

For the negative electrode in the battery of the present invention, the coke treated as described above is used as the negative electrode material, and this is mixed with a binder such as polytetrafluoroethylene (PTFE) or polyvinylidene fluoride (PVdF). The negative electrode mixture is used and then pressure-molded at a predetermined pressure. If necessary, a conductive agent such as acetylene black or carbon black may be added.

As described above, the battery of the present invention is characterized in that coke in which reactivity of oxygen-containing functional groups and active sites is suppressed is used as the negative electrode material. Therefore, for other members constituting the battery such as the positive electrode material, the non-aqueous electrolyte, and the separator (when the liquid electrolyte is used), various materials which have been practically used or proposed for the conventional non-aqueous secondary battery. Can be used.

[0019]

In the battery of the present invention, since the coke in which the reactivity of the oxygen-containing functional group and the active site is suppressed is used as the negative electrode material, the amount of lithium that can participate in the electrochemical reaction during charge / discharge increases. At the same time, self-discharge and decomposition of the electrolyte are less likely to occur.

[0020]

The present invention will be described in more detail based on the following examples, but the invention is not intended to be limited by the following examples, and various modifications can be made without departing from the scope of the invention. Is possible.

[Tripolar Battery Test] (Production Example 1) Jet mill crusher (manufactured by Seishin Enterprise Co., Ltd.,
Model "CPN-04"), average particle size 14μ
petroleum calcined coke crushed to m (specific surface area: 6.5 m
² / g, d ₀₀₂ : 3.441Å, Lc: 49Å) 100
g was immersed in 2 liters of 0.025N-KOH aqueous solution, and stirred at room temperature for 24 hours.

Next, this aqueous solution is suction-filtered using a Buchner funnel, and then deionized water 10 having a pH of 6.8 is used.
Washed using 1 liter. The pH of the filtrate at the end of washing was 7.1.

The thus-obtained filtered product was treated at 120 ° C.
And dried for 12 hours to prepare coke as a negative electrode material. The specific surface area of this coke was 6.6 m ² / g, and d ₀₀₂ and Lc by X-ray diffraction were 3.440Å and 4 respectively.
9Å, and the potassium content was 42 ppm.

The specific surface area is measured by Carlo Elba's surface area measuring device (product code "Sorptomatic 190").
0 ") was used for the BET method, and d
The X-ray diffraction parameters of ₀₀₂ and Lc are obtained according to the Gakshin method. In addition, the potassium content after the treatment is determined by JIS after ashing the sample in air at 800 ° C.
It is measured by the flame method according to K0102.
The same applies to the following values.

(Production Example 2) 500 g of petroleum calcined coke having the same average particle diameter as that prepared in Production Example 1 was added to 0.0
It was dipped in 10 liters of a 5N-KOH aqueous solution and stirred in an oil bath at 80 ° C for 24 hours.

Next, 3 kg of this aqueous solution was applied using a pressure filter (manufactured by BF Kogyo Co., Ltd., model "FB-30").
Pressure filtration was performed at a pressure of / cm ² G.

Further, the filtration product was dispersed in 10 liters of water and then filtered, which was repeated twice for washing. The pH of the filtrate at the end of this washing was 7.3.

The thus-obtained filtered product was treated at 120 ° C.
And dried for 12 hours to prepare coke as a negative electrode material. The specific surface area of this coke was 6.0 m ² / g, and d ₀₀₂ and Lc by X-ray diffraction were 3.441Å and 5 respectively.
0Å, and the potassium content was 105 ppm.

(Production Example 3) A coke as a negative electrode material was produced in the same manner as in Production Example 1 except that a 0.0005N-KOH aqueous solution was used instead of the 0.025N-KOH aqueous solution. The specific surface area of the coke is 6.5 m ² /
g, d ₀₀₂ and Lc by X-ray diffraction were each 3.44.
1Å, 49Å, and the potassium content was 0.8 ppm.

Each electrode using the coke produced in the above Production Examples 1 to 3 or the coke not treated with the KOH aqueous solution (the coke to be treated in Production Examples 1 to 3) as a negative electrode material was used as a working electrode. , A lithium electrode was used as a counter electrode and a reference electrode, and a three-electrode battery test was conducted. The initial charge capacity (mAh / g) and discharge capacity (mAh / g) per unit weight of each electrode and the battery capacity of each three-electrode battery ( mAh), battery capacity after 500 cycles (mAh)
h) and the residual capacity rate (%) after storage at 60 ° C. for 10 days were examined. Charge / discharge current density 0.2mA / cm
Went in ² . The results are shown in Table 1.

[0031]

[Table 1]

[Battery Test] (Example 1) [Production of Positive Electrode] LiCoO ₂ as a positive electrode active material, acetylene black as a conductive agent, and fluororesin as a binder were mixed at a weight ratio of 85: 10: 5. The mixture was mixed in a ratio to obtain a positive electrode mixture. The positive electrode mixture thus obtained was pressure-molded into a disk shape at a pressure of 2 ton / cm ² , and the obtained molded product was heat treated at 250 ° C. for 2 hours to prepare a positive electrode. An aluminum lath plate was used as the positive electrode current collector.

[Production of Negative Electrode] The coke produced in Production Example 1 was used as a negative electrode material, and this was mixed with PTFE in a weight ratio of 90: 1.
The mixture was kneaded at a ratio of 0 to obtain a negative electrode mixture. The negative electrode mixture thus obtained was pressure-molded into a disc shape at a pressure of 2 ton / cm ² , and the obtained molded product was heat-treated at 250 ° C. for 2 hours to prepare a negative electrode. A copper lath plate was used as the negative electrode current collector.

[Preparation of Non-Aqueous Electrolyte] LiPF ₆ was dissolved in propylene carbonate at 1 mol / liter to prepare a non-aqueous electrolyte.

[Preparation of Non-Aqueous Secondary Battery]
A flat type non-aqueous secondary battery BA1 (battery size: diameter: 24 mm, thickness: 3 mm) according to the present invention was produced by using a positive electrode can, a negative electrode can and the like in addition to the non-aqueous electrolyte solution. As the separator, a microporous thin film made of polypropylene was used and impregnated with the above-mentioned non-aqueous electrolyte solution. Further, the positive and negative electrode capacities were regulated so that the negative electrode capacities were made smaller than the positive electrode capacities and the negative electrode capacities were controlled.

FIG. 1 is a schematic cross-sectional view of the manufactured battery BA1. The battery BA1 shown in the drawing is a positive electrode 1, a negative electrode 2, a separator 3, a positive electrode can 4, a negative electrode can 5, a positive electrode current collector 6, and a negative electrode. It is composed of a current collector 7 and an insulating packing 8 made of polypropylene. The positive electrode 1 and the negative electrode 2 are housed in a battery case formed by positive and negative bipolar cans 4 and 5 facing each other with a separator 3 in between, and the positive electrode 1 is provided with a positive electrode collector 6 and a positive electrode can 4 in between.
In addition, the negative electrode 2 is connected to the negative electrode can 5 through the negative electrode current collector 7 so that the chemical energy generated inside the battery BA1 can be extracted as electric energy from both terminals of the positive electrode can 4 and the negative electrode can 5. Has become.

Example 2 A battery BA2 of the present invention was produced in the same manner as in Example 1 except that the coke produced in Production Example 2 was used as the negative electrode material.

Comparative Example 1 A comparative battery BC1 was produced in the same manner as in Example 1 except that the coke produced in Production Example 3 was used as the negative electrode material.

(Comparative Example 2) Untreated without treatment with KOH aqueous solution (ie potassium content 0 ppm)
A comparative battery BC2 was produced in the same manner as in Example 1 except that the coke of Example 1 was used.

Inventive batteries BA1 and BA2 and comparative battery B
C1 and BC2 were charged and discharged at a current density of 1 mA / cm ² , and the initial battery capacity (mAh) of each battery, the battery capacity after 500 cycles (mAh) and 10 ° C. at 60 ° C.
The capacity remaining rate (%) after storage for a day was examined. The results are shown in Table 1 above.

From Table 1, the batteries BA1 and BA2 of the present invention using the coke treated with the KOH aqueous solution as the negative electrode material have larger battery capacities at the initial stage and after 500 cycles than the comparative batteries BC1 and BC2. It can be seen that the capacity remaining rate after storage is high. Comparative battery B
Like the batteries BA1 and BA2 of the present invention, C1 is a battery using coke treated with a KOH aqueous solution as a negative electrode material, but good results could not be obtained because the amount of potassium used was too small. Is.

In the above embodiment, a specific example in which the present invention is applied to a flat type battery has been described. However, the shape of the battery is not particularly limited, and the present invention has various shapes such as a cylindrical shape and a square shape. It is applicable to non-aqueous electrolyte batteries.

[0043]

EFFECTS OF THE INVENTION Since the battery of the present invention can store and release lithium in the negative electrode in a large amount, the present invention has excellent unique effects such as a large battery capacity and excellent storage characteristics and cycle characteristics.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of a battery of the present invention (flat battery).

[Explanation of symbols]

 BA1 flat battery 1 positive electrode 2 negative electrode 3 separator

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Masahisa Fujimoto, 2-18, Keihanhondori, Moriguchi-shi, Osaka Sanyo Electric Co., Ltd. (72) Noriyuki Yoshinaga, 2--18, Keihanhondori, Moriguchi, Osaka Sanyo Inside the Electric Co., Ltd. (72) Inventor Koji Nishio 2-18 Keihan Hon-dori, Moriguchi City, Osaka Sanyo Electric Co., Ltd. (72) Inventor Nobuhiro Furukawa 2-chome Keihan Hon-dori, Moriguchi, Osaka Sanyo Electric Co., Ltd.

Claims (2)

[Claims] 1. A coke in which an alkali metal or an alkaline earth metal is bound to an oxygen-containing functional group and an active site, thereby suppressing the reactivity of the oxygen-containing functional group and the active site, as a negative electrode material, A non-aqueous secondary battery characterized by being used. 2. A non-aqueous secondary comprising a coke in which an alkali metal or an alkaline earth metal is bound to an oxygen-containing functional group and an active site, whereby the reactivity of the oxygen-containing functional group and the active site is suppressed. Negative electrode material for batteries.