JPH0831453A - Nonaqueous solvent secondary battery - Google Patents

Abstract

PURPOSE:To provide a nonaqueous solvent electrolyte battery of an excellent discharge cycle life by assembling a nonaqueous solvent secondary battery comprising specific positive and negative electrodes, and then applying a pre- discharge process to it. CONSTITUTION:For a nonaqueous secondary battery including a positive electrode including lithium manganese compound formed of lithium nitrate and manganese dioxide, and a negative electrode comprising lithium and carbon material as carrier for it, after the battery is assembled, a pre-discharge process for 10-30% the capacity of the positive electrode is applied. For the lithium carrier to be used in the negative electrode, carbon material obtained by baking organic high polymer compound such as phenol resin, polyacrylonitrile, or cellulose; carbon material obtained by baking cokes or pitch; or carbon material such as artificial graphite or natural graphite can be listed. For the capacity of the pre-discharge process, storage characteristics in high temperatures are not improved when it is less than 10%, and when it exceeds 30%, the initial discharge capacity is decreased largely, which are not favorable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous solvent secondary battery, and more specifically, a lithium manganese compound containing lithium nitrate and manganese dioxide as a raw material for a positive electrode and lithium and a carbonaceous material as a carrier thereof for a negative electrode. And a non-aqueous solvent secondary battery containing the same.

[0002]

2. Description of the Related Art In recent years, with the development of electronic equipment, there has been a demand for the development of a secondary battery that is small and lightweight, has a high energy density, and can be repeatedly charged and discharged.

In this type of secondary battery, lithium or a lithium alloy is used as the negative electrode active material, and oxides, sulfides or selenides of molybdenum, vanadium, titanium, niobium and the like are used as the positive electrode active material. Things are known.

However, in a battery system using lithium or a lithium alloy as the negative electrode active material, there is a problem that charge / discharge cycle life is short because dendrite of lithium is generated on the negative electrode when charge / discharge is repeated.

This has been solved by using lithium and a carbonaceous material as a carrier thereof for the negative electrode. In particular, a non-aqueous solvent secondary battery using a lithium manganese compound using lithium nitrate and manganese dioxide as raw materials for the positive electrode and lithium and a carbonaceous material as its support for the negative electrode has a high operating voltage and a long charge / discharge cycle life. It is attracting attention as a battery that can be greatly improved.

However, in a non-aqueous solvent secondary battery in which a lithium manganese compound containing lithium nitrate and manganese dioxide as raw materials is used for the positive electrode and lithium and a carbonaceous material as its carrier are used for the negative electrode, a fully charged state Since the lithium manganese compound used as the positive electrode and made of lithium nitrate and manganese dioxide as a raw material has a high potential, decomposition of the electrolytic solution occurs. Therefore, when stored in a high temperature atmosphere, there is a problem that the discharge capacity after storage becomes lower than that before storage.

[0007]

SUMMARY OF THE INVENTION An object of the present invention is to solve the above problems and provide a non-aqueous solvent secondary battery having excellent charge / discharge cycle life.

[0008]

The present invention is directed to a non-aqueous solvent secondary containing a positive electrode containing a lithium manganese compound prepared from lithium nitrate and manganese dioxide as a raw material, and a negative electrode containing lithium and a carbonaceous material as its carrier. A battery, the battery having a positive electrode capacity of 10 to 30 after assembling the battery.
% Of the secondary battery is a non-aqueous solvent secondary battery.

The present invention is based on the fact that by pre-discharging 10 to 30% of the positive electrode capacity, deterioration of the discharge capacity of the battery during high temperature storage can be suppressed.

As the positive electrode used in the present invention, a lithium manganese compound obtained by using lithium nitrate and manganese dioxide as raw materials is used as an active material, and carbon black such as acetylene black, a conductive material such as nickel powder, and a poly material. Tetrafluoroethylene, polyethylene, polypropylene, poly (meth) acrylic acid, poly (meth) acrylic acid salt, poly (meth) acrylic acid ester and (meth) acrylic acid and / or (meth)
A binder such as a copolymer of an acrylate ester and another comonomer may be blended and molded into pellets, for example.

The lithium carrier used in the negative electrode of the present invention is a carbonaceous material obtained by firing an organic polymer compound such as phenol resin, polyacrylonitrile, or cellulose; a carbonaceous material obtained by firing coke, pitch or the like. Materials; and carbonaceous materials such as artificial graphite and natural graphite.

The negative electrode is manufactured as follows. For example,
A carbonaceous material obtained by firing the polymer compound in an atmosphere of an inert gas such as argon or nitrogen under the conditions of a temperature of 500 to 3,000 ° C. and normal pressure or reduced pressure, and the same binder as used for the positive electrode. This is to add lithium to a molded body obtained by adding and mixing a binder and molding it into, for example, a pellet shape by an electrolytic impregnation method.

The separator includes, for example, a non-woven fabric of polyolefin resin such as polyethylene or polypropylene,
These porous films and the like can be used. As the electrolytic solution, for example, one or more non-aqueous solvents selected from ethylene carbonate, propylene carbonate, dimethyl carbonate, diethyl carbonate, ethyl methyl carbonate, etc., and lithium hexafluorophosphate (LiPF
₆ ), an electrolyte such as lithium perchlorate (LiClO ₄ ) and lithium borofluoride (LiBF ₄ ) in an amount of 0.2 to 1.5.
It is possible to use the one dissolved at a concentration of mol / l.

A test battery including the above-mentioned battery components is assembled and, as shown below, a treatment including preliminary discharge is performed.

(1) After preliminary storage at room temperature for 7 to 14 days, until a predetermined discharge depth with respect to the positive electrode capacity is obtained,
Pre-discharge with constant current or constant resistance. (2) Then,
Store at room temperature for 3-20 days. (3) 20 more
Store at a temperature of ~ 60 ° C for 20-60 days.

The capacity of the pre-discharge treatment (discharge depth) before storage is in the range of 10 to 30%, preferably 15 to 30% of the capacity of the positive electrode. If the ratio of the depth of discharge to the positive electrode capacity is less than 10%, the storage characteristics at high temperatures are not improved, and if it exceeds 30%, the initial discharge capacity is greatly reduced, which is not preferable.

[0017]

According to the present invention, it is possible to suppress deterioration of the discharge capacity of a battery due to high temperature storage, and as a result, it is possible to provide a non-aqueous solvent secondary battery having a long charge / discharge cycle life.

[0018]

EXAMPLES The present invention will now be described in more detail based on examples.

(1) Preparation of Positive Electrode A lithium manganese compound prepared from lithium nitrate and manganese dioxide as an active material, artificial graphite as a conductive material and polytetrafluoroethylene as a binder, an active material, a conductive material and a binder. The weight ratio of the adhesive is 90:10:
The mixture was mixed and kneaded so that the mixture had a diameter of 19 mm and a thickness of 0.1 mm by using a pressure press at a pressure of ² ton / cm ² .
A 91 mm pellet was pressure-molded to obtain a positive electrode.

(2) Preparation of Negative Electrode Pitch-based carbon fibers made of menphatic pitch as a raw material were finely pulverized and fired at a temperature of 2800 ° C. to obtain a carbonaceous powder. Butadiene-styrene rubber as a binder was mixed and kneaded with this powder at a weight ratio of 95: 5, and the mixture was pressurized at a pressure of ² ton / cm ² and a diameter of 19
mm and a thickness of 1.19 mm was pressed into a pellet. Next, this pellet molded body was made to contain lithium by an electrolytic impregnation method to obtain a negative electrode.

(3) Assembly of Battery FIG. 1 is a sectional view of a non-aqueous solvent secondary battery according to the present invention. The non-aqueous solvent secondary battery was assembled as follows. The positive electrode (2) was housed on the inner surface of the positive electrode container (1) made of stainless steel via the positive electrode current collector (3) made of stainless expanded metal having a diameter of 12 mm and a thickness of 0.1 mm. A separator (4) in which a polypropylene nonwoven fabric is impregnated with an electrolytic solution in which lithium perchlorate is dissolved in a solvent in which ethylene carbonate and diethyl carbonate are mixed at a volume ratio of 1: 1 to a concentration of 1 mol / L, It was placed on the positive electrode (2). A negative electrode (7) was attached to the inner surface of a negative electrode container (5) made of stainless steel via a negative electrode current collector (6) made of nickel expanded metal having a diameter of 12 mm and a thickness of 0.1 mm. Finally, the negative electrode container (5) is fitted into the opening of the positive electrode container (1) via the insulating gasket (8), and the positive electrode container (1) is caulked to form the positive electrode container (1). The positive electrode (2), the separator (4) and the negative electrode (7) are hermetically sealed in the negative electrode container (5) to have an outer diameter of 24.5 mm and a thickness of 3.0 mm.
The coin type non-aqueous solvent secondary battery of was assembled.

(4) Pre-discharge treatment and measurement of battery characteristics After assembling the battery as described above and pre-storing at room temperature for 7 to 14 days, the discharge depth was 5 against the positive electrode capacity at a constant current of 2 mA. The battery was pre-discharged to 10, 15, 20 and 30%, and each battery was charged with A, B, C, D,
It was set to E. Among them, B to E are batteries according to the present invention, and A is a battery for comparison. In addition, the battery F that does not perform the preliminary discharge
Was also subjected to the following experiment as a battery for comparison. After the preliminary discharge, the battery was stored at room temperature for 4 days and then the open circuit voltage of the battery was measured. The result is shown in FIG. After that, battery A
~ F were stored in a 60 ° C atmosphere for 20, 40, and 60 days, respectively. After storage, the battery was taken out and left at room temperature for 8 hours or more. After that, constant resistance discharge was performed at 15 kΩ to 2.
The discharge capacity up to 0 V was measured, and the capacity retention rate after storage with respect to the initial discharge capacity was obtained. The result is shown in FIG.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of a coin type non-aqueous solvent secondary battery of the present invention.

FIG. 2 is a diagram showing a relationship between a preliminary discharge depth and an open circuit voltage of a battery.

FIG. 3 is a diagram showing a relationship between a preliminary discharge depth and a discharge capacity retention rate after high temperature storage.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode container 2 Positive electrode 3 Positive electrode current collector 4 Separator 5 Negative electrode container 6 Negative electrode current collector 7 Negative electrode 8 Insulating gasket A Battery with 5% preliminary discharge depth A B Battery with 10% preliminary discharge depth B C 15% preliminary discharge depth Battery C D Battery with pre-discharge depth of 20% D E Battery with pre-discharge depth of 30% E F Battery with no pre-discharge depth F

Claims (1)

[Claims] 1. A non-aqueous solvent secondary battery comprising a positive electrode containing a lithium manganese compound made from lithium nitrate and manganese dioxide as a raw material, and a negative electrode made of a carbonaceous material as a lithium and a carrier thereof. After that, 10 to 30% of the positive electrode capacity is subjected to a pre-discharge treatment, the non-aqueous solvent secondary battery.