JPH08203502A - Method for producing non-aqueous electrolyte secondary battery and negative electrode thereof - Google Patents

Abstract

(57) [Summary] [Objective] When a graphite material, particularly graphite having a high degree of graphitization capable of occluding a large amount of lithium, is used for the negative electrode, gas is prevented from being generated by decomposition of the electrolytic solution on the surface of the negative electrode. [Structure] A graphite powder having an 002 plane spacing (d002) of 3.36 Å or more and 3.39 Å or less by X-ray wide-angle diffraction method is used as a negative electrode, and a calcined organic material is supported on the surface of the graphite powder particles. is there.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to graphite powder particles for use in a non-aqueous electrolyte secondary battery, especially in its negative electrode.

[0002]

2. Description of the Related Art In recent years, portable electronic devices for consumer use,
Cordless is advancing rapidly. Along with this, there is an increasing demand for a small-sized, lightweight secondary battery having a high energy density, which serves as a driving power source. From this point of view, non-aqueous secondary batteries, especially lithium secondary batteries, have great expectations as batteries having particularly high voltage and high energy density, and development is urgently needed.

Heretofore, manganese dioxide, vanadium pentoxide, titanium disulfide and the like have been used as positive electrode active materials for lithium secondary batteries. A battery is composed of the positive electrode, a negative electrode using lithium metal, and an organic electrolyte solution, and when the battery is repeatedly charged and discharged, dendrite-like lithium is generated on the surface of the lithium metal of the negative electrode, which causes an internal short circuit of the battery. It was happening.

In order to solve this problem, a carbon material, which is a layered compound capable of inserting and extracting lithium between layers, has attracted attention, and a graphite material is particularly promising.

[0005]

However, when a graphite material having a 002 plane spacing (d002) of 3.36 Å or more by X-ray wide-angle diffraction method, which is excellent in crystallinity and has a large lithium absorption amount, is used for the negative electrode, When the battery is charged and discharged, the electrolytic solution is decomposed on the surface of the negative electrode, and gas is generated with the decomposition of the electrolytic solution to increase the internal pressure of the battery, which causes expansion of the battery and leakage of the electrolytic solution.

Although the mechanism of gas generation by decomposition of the electrolytic solution on the surface of the negative electrode is unknown, there is an active portion on the surface of the graphite used for the negative electrode, and the active portion reacts with the solvent in the electrolytic solution to produce gas. It is thought to occur.

The present invention solves such a problem and prevents generation of gas due to decomposition of the electrolytic solution on the surface of the negative electrode when a graphite material having a large lithium occlusion amount is used for the negative electrode. It is a thing.

[0008]

In order to solve the above problems, in the non-aqueous electrolyte secondary battery of the present invention, the negative electrode has a 002 plane spacing (d002) of 3.36Å according to the X-ray wide angle diffraction method.
Graphite powder particles having a particle size of 3.39 Å or less are used, and an organic material fired body is carried on the surface of the graphite powder.

Examples of the precursor material of the fired organic material include rubbers such as styrene-butadiene rubber, celluloses such as carboxymethyl cellulose, polyethers, polyesters, polyvinyls, resins such as acrylic resins and phenolic resins.

[0010]

In this constitution, the organic substance calcined material is supported on the surface of the graphite powder having the interplanar spacing (d002) of the 002 plane of 3.36 Å or more and 3.39 Å or less by the X-ray wide-angle diffraction method. Since direct contact is prevented, the decomposition of the electrolytic solution on the surface of the graphite powder particles can be suppressed, the generation of gas due to the decomposition of the electrolytic solution can be suppressed, and the rise of the internal pressure of the battery can be prevented.

The pseudo graphite powder having a 002 plane spacing (d002) of 3.40 Å or more has a low graphitization degree and an undeveloped layered structure, so that the amount of lithium that can be stored in the crystal is small.

[0012]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a vertical sectional view of a cylindrical non-aqueous electrolyte secondary battery of the present invention. In the figure, 1 is a positive electrode, in which carbon black is mixed as a conductive material with LiCoO ₂ as an active material, and an aqueous dispersion of polytetrafluoroethylene as a binder is mixed at a weight ratio of 100: 3: 10. Is applied to both sides of an aluminum foil, dried, rolled, and then cut into a predetermined size. The lead plate 2 made of titanium is spot-welded to the positive electrode. The mixing ratio of the aqueous dispersion of polytetrafluoroethylene as the binder is calculated by its solid content. Reference numeral 3 is a negative electrode, and the surface spacing of the 002 plane by wide-angle X-ray diffraction (d002)
Needle-shaped artificial graphite powder particles having a diameter of 3.37Å are added to styrene-butadiene rubber (SB
R) Aqueous dispersion of resin powder is used in a solid content weight ratio of 1
The main constituent material is mixed at 00: 5, dried at 60 ° C. for 10 hours, lightly pulverized, and heat-treated in air at 250 ° C. for 5 hours to carry carbonized SBR on the surface of graphite particles. Then, an acrylic resin emulsion as a binder was mixed with the graphite powder at a weight ratio of 100: 5, the mixture was applied to both surfaces of the nickel foil, dried, rolled, and then cut into a predetermined size. . A lead plate 4 made of nickel is spot-welded to the negative electrode. 5 is a separator made of polypropylene microporous film,
And the negative electrode 3, and these are spirally wound to form an electrode plate group. Insulating plates 6 and 7 made of polypropylene are arranged at the upper and lower ends of the electrode plate group, respectively, and inserted into a nickel-plated stainless steel case 8. Then, the positive electrode lead 2 is connected to the sealing plate 10 made of titanium.
Then, after spot-welding the negative electrode lead 4 to the bottom of the case 8, 1 LiPF ₆ of lithium salt was added to a mixed solvent of equal volume of ethylene carbonate and diethyl carbonate.
A predetermined amount of the nonaqueous electrolytic solution dissolved at a ratio of mol / l is injected into the case, and the battery is sealed with the sealing plate 10 through the gasket 9 to form the battery. The size of this battery is 14
mm, height 50 mm. In addition, 11 is a positive electrode terminal of the battery, and the battery case 8 also serves as a negative electrode terminal. The battery thus prepared was designated as Battery A of the present invention.

A battery similar to that of the present invention except that the mesophase spheres, which are formed by the graphite material in the carbonization process of the pitch, are graphitized at 2800 ° C. and the plane spacing (d002) of 002 planes is 3.37Å. Was produced and used as Battery B of the present invention.

Further, batteries similar to the battery B of the present invention were prepared except that the precursor material of the organic burned material was as shown in (Table 1), and these batteries were designated as batteries C to G of the present invention.

[0016]

[Table 1]

On the other hand, as a graphite material, mesophase spherules formed in the carbonization process of pitch were graphitized at 2800 ° C., and graphite having a 002 plane spacing (d002) of 3.37Å was used as a binder. A battery similar to that of the present invention was prepared except that a certain acrylic resin emulsion was mixed at a weight ratio of 100: 5 to form a negative electrode, and this was used as a comparative battery H.

Also, the mesophase spheres are
Carbonized at ℃, the spacing between 002 planes (d002) is 3.42
A battery similar to that of the present invention was manufactured except that the carbonaceous material of Å was used, and this was used as a comparative battery I.

Next, using these batteries A to I,
A cycle of charging to 4.1 V with a constant current of 00 mA and discharging to 3.0 V was repeated twice. At this time, when the battery internal pressure increased and the valve of the battery operated, the non-defective rate was examined.

The results are shown in (Table 1). As shown in (Table 1), in the batteries A to G, gas generation due to decomposition of the electrolytic solution could be suppressed, and increase in the battery internal pressure could be prevented.

In Battery I, it was possible to prevent the internal pressure of the battery from rising, but since d002 was 3.42Å, the layered structure of the carbon material was undeveloped, and the amount of lithium that could be stored in the crystal decreased. Battery capacity has decreased. Therefore, graphite having d002 of 3.40 Å or less is preferable.

In this embodiment, LiCo is used as the positive electrode active material.
O ₂ was used, but other than this, LiNiO ₂ , LiFe
O ₂ , LiMn ₂ O ₄ , these Co, Ni, Fe, Mn
It may be a lithium-containing composite oxide in which a part of is replaced with another transition metal.

As the organic solvent for the non-aqueous electrolyte, propylene carbonate, ethylene carbonate, 1,2-dimethoxyethane, 1,2-diethoxyethane, γ-butyrolactone, tetrahydrofuran, 1, 3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methyl sulfolane, acetonitrile, propionitrile, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate, acetic acid Propyl, methyl propionate, ethyl propionate and the like may be used alone or in admixture of two or more.

LiC which has been conventionally known as a solute
lO ₄ , LiAsF ₆ , LiBF ₄ , LiPF ₆ , LiB
(C ₆ H ₅ ) ₄ , LiCl, LiBr, CH ₃ SO ₃ Li,
CF ₃ SO ₃ Li or the like may be used. Further, as the precursor material of the organic material fired body, rubbers such as acrylonitrile butadiene rubber (NBR), butadiene rubber (BR), isoprene rubber (IR), resins such as phenol resin, carboxyethyl cellulose, etc. are used as the precursor material. Similar effects can be obtained even with celluloses such as, polyethers such as polybutylene oxide, polyesters, and polyvinyls.

[0025]

As described above, in the non-aqueous electrolyte secondary battery of the present invention, the negative electrode is made of graphite powder having a 002 plane spacing (d002) of 3.36 Å or more and 3.39 Å or less by the X-ray wide angle diffraction method. The organic powder calcined product is supported on the surface of the graphite powder particles, and even if the graphite used for the negative electrode is a graphite powder having a high graphitization degree with a large lithium occlusion amount, direct contact between the graphite surface and the electrolytic solution is achieved. Since the contact is prevented by the fired organic material, it is possible to suppress the generation of gas due to the decomposition of the electrolytic solution and prevent the internal pressure of the battery from rising.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a cylindrical non-aqueous electrolyte secondary battery used in this example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Positive electrode lead 3 Negative electrode 4 Negative electrode lead 5 Separator 6 Insulating plate 7 Insulating plate 8 Battery case 9 Sealing gasket 10 Sealing plate 11 Positive electrode terminal

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Akikatsu Morita 1006 Kadoma, Kadoma City, Osaka Prefecture Matsushita Electric Industrial Co., Ltd.

Claims (4)

[Claims] 1. A positive electrode using a lithium-containing oxide, a non-aqueous electrolyte, and a negative electrode using a graphite powder capable of intercalating / deintercalating lithium, wherein the graphite powder particles are X-ray wide-angle diffraction method. The non-aqueous electrolyte secondary battery in which the interplanar spacing (d002) of 002 surface is 3.36 Å or more and 3.39 Å or less, and the fired organic material is supported on the surface of the graphite powder particles. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the graphite powder is formed by graphitizing mesophase spherules formed in the carbonization process of pitch. 3. A graphite powder and an organic material powder having an interplanar spacing (d002) of 002 planes of 3.36 Å or more and 3.39 Å or less by X-ray wide-angle diffraction method are mixed and heat-treated to carbonize the organic material. A method for producing a negative electrode for a non-aqueous electrolyte secondary battery, in which a fired body of an organic material is supported on the surface of the graphite powder particles, and then the graphite particles are applied or molded on a metal current collector. 4. The method for producing a negative electrode for a non-aqueous electrolyte secondary battery according to claim 3, wherein the graphite is formed by graphitizing mesophase spherules formed in the carbonization process of pitch.