JP3043048B2 - Solid electrolyte battery - Google Patents

Description

The present invention relates to a solid electrolyte battery using a conductive film.

(Mouth) Conventional technology With the recent reduction in size, weight, and thickness of electronic devices,
The battery used for this is small and has a total thickness
There is a demand for a very thin and high-performance one with a thickness of about 0.5 mm.

As a battery used for these applications, a lithium battery is promising in terms of high energy density and reliability, but a conventionally used electrolyte is a liquid electrolyte. in this case,
As a battery sealing method, a sealing technique using a crimp seal via a gasket is mainly used.

(C) Problems to be Solved by the Invention By the way, in the above-mentioned conventional battery, as the battery becomes thinner, the ratio of the sealing member to the battery volume becomes larger, which causes a decrease in the energy density of the battery, and also the electrolyte and the electrode activity. Since the substances react, decomposition of the electrolytic solution occurs, causing deterioration of battery characteristics and large self-discharge.

For this reason, in the conventional battery system, there were problems that the characteristics of the battery deteriorated due to the decomposition of the electrolytic solution, the self-discharge rate was large, and it was difficult to reduce the thickness of the battery.

The problem to be solved by the present invention is to provide a battery that is free from the risk of liquid leakage and decomposition of an electrolyte in view of the problems of the related art, and to provide a positive electrode and a negative electrode that are suitable for a thin shape of the battery. It is an object.

(D) Means for Solving the Problems The present invention provides a method of dissolving an inorganic metal compound or a conductive polymer, an organic polymer compound, and an alkali metal salt in a solvent as a positive electrode, and casting this on a substrate. Then, using a conductive film formed by drying, a carbon material, an organic polymer compound, and an alkali metal salt are dissolved in a solvent as a negative electrode, and this is cast on a substrate and dried to form. Using a conductive film made, an organic polymer compound as an electrolyte, and an alkali metal salt are dissolved in a solvent, cast on a substrate, and dried to form a solid electrolyte battery using a conductive film formed by drying. is there.

(E) Function With the above configuration, it is possible to easily produce a positive electrode, a negative electrode, and a polymer solid electrolyte film which are thin, uniform, and have a large degree of freedom in shape.

In addition, the solid electrolyte can suppress leakage of the battery and decomposition of the electrolyte, and can also suppress self-discharge.

These configurations are particularly effective for reducing the thickness of the electrode.

(F) Examples Hereinafter, the present invention will be described specifically with reference to Examples.

[Example 1] First, LiBF ₄ as an alkali metal salt was dissolved in N-methyl-2-pyrrolidone as a solvent, polyethylene oxide as an organic polymer compound was added thereto, and the mixture was shaken until uniform, and further, , Add MnO ₂ and shake until uniform, cast this solution on the cathode case,
Vacuum drying was performed under the condition of ° C. to obtain a conductive film for a positive electrode having a thickness of 30 μm.

In addition, LiBF ₄ was dissolved in N-methyl-2-pyrrolidone, polyethylene oxide was added thereto, and the mixture was shaken until uniform, graphite as a carbon material was added thereto, and the mixture was shaken again until the mixture became uniform. Was cast on a negative electrode package, and vacuum-dried at 80 ° C. to obtain a conductive film for negative electrode having a thickness of 30 μm.

Further, LiBF ₄ was dissolved in N-methyl-2-pyrrolidone, polyethylene oxide was added thereto, and the mixture was shaken until uniform, and the solution was cast on a glass substrate.
Vacuum drying was performed under the condition of ° C. to obtain a solid polymer electrolyte film having a thickness of 30 μm.

A flat lithium secondary battery as shown in FIG. 1 was assembled using the above electrodes and electrolyte. In FIG.
Reference numeral 1 denotes a positive electrode film, 2 denotes a negative electrode film, and 3 denotes a polymer solid electrolyte film, which is formed using the above method. In addition, 4 is an insulating sealing material, 5 is a positive electrode exterior body, 6
Denotes a negative electrode package. The battery assembled in this manner is referred to as Battery A of the present invention.

As a comparative example, a LiBF ₄ -PC solution (liquid) was used as an electrolyte instead of the polymer solid electrolyte film,
A comparative battery B was produced in the same manner as the battery A of the present invention, except that this was impregnated with a polypropylene separator.

The batteries A and B thus obtained were subjected to a charge / discharge test. The condition at this time is a charging current of 1 mA, 3.6
V, and in the case of discharge, up to 2.0 V with a discharge current of 1 mA.

FIG. 2 is a diagram showing the discharge characteristics of each of the batteries A and B after storage at room temperature for one month. Each battery showed a capacity of 20 mAh in the initial discharge characteristics and a charge / discharge efficiency of 100%. However, as shown in this figure, the battery A of the present invention was able to discharge 20 mAh after storage, while the comparative battery B was only 12 mAh. It can be seen that only discharge can be performed.

This is a comparative battery B using a LiBF ₄ -PC solution as the electrolyte.
In this case, the electrode active material reacts with the electrolytic solution, but it is considered that such a reaction does not occur in the battery A of the present invention.

[Example 2] N-methyl- was prepared in the same manner as in Example 1 except that polyaniline was used for the positive electrode instead of MnO ₂ in Example 1.
A thin battery C of the present invention using a polymer solid electrolyte made of 2-pyrrolidone and a thin battery D of a comparative example manufactured using propylene carbonate as a liquid electrolyte were produced.

These batteries C and D were subjected to a charge / discharge test. The condition at this time is a charging current of 1 mA, up to 3.6 V,
In the case of discharging, it was decided to carry out up to 2.5 V at a discharging current of 1 mA.

FIG. 3 is a view showing the discharge characteristics of each of the batteries C and D after storage at room temperature for one month. All of the batteries showed a capacity of 4 mAh in the initial discharge characteristics and a charge / discharge efficiency of 100%. However, as shown in this figure, the battery C of the present invention can discharge 4 mAh after storage, whereas the comparative battery D has only 2.8 mAh. It can be seen that only mAh can be discharged.

This is a comparative battery D using a LiBF ₄ -PC solution as the electrolyte.
In this case, the electrode active material reacts with the electrolytic solution, but it is considered that such a reaction does not occur in the battery A of the present invention.

In the above examples, the organic polymer compound is not particularly limited as long as it can be dissolved in a solvent, and specific examples thereof include polyethylene oxide, polypropylene oxide, and polyphosphazene.

As the solvent, a cyclic compound containing a nitrogen atom, in particular, pyrrolidone and its derivatives are preferable, and specific examples thereof include N-methyl-2-pyrrolidone.

Further example LiC1O as alkali metal salts _4, LiBF _4, L
iCF ₃ SO ₃ , LiPF ₆ , NaPF ₆ , NaBF ₄ , NaClO ₄ , NaAsF ₆ , KP
F ₆ , KAsF ₆ , KClO ₄ , KBF _{4 and the} like.

On the other hand, the type of the positive electrode of the solid electrolyte battery of the present invention is not particularly limited, and MnO ₂ , TiS ₂ , and FeS ₂ that reversibly react with an alkali metal as a compound to be mixed with the organic polymer compound and an alkali metal salt are used. _{, Nb 3 S 4, Mo 3} Se 4, CoS 2, V 2 O 5, P
Inorganic compounds such as ₂ O ₅ , CrO ₃ , V ₃ O ₆ , TeO ₂ , and GeO ₂ and conductive polymers such as polyaniline, polypyrrole, and polythiophene, which are reversibly doped and undoped with electrolyte anions, can be used.

The negative electrode is used by mixing carbon with the above organic polymer and alkali metal salt. Examples of carbon in this case include graphite and coke. The particle size of the carbon is desirably 100 μm or less, particularly desirably 50 μm or less.

(G) Effects of the Invention As described above, the present invention dissolves an inorganic metal compound or a conductive polymer, an organic polymer compound, and an alkali metal salt in a solvent, and casts this on a substrate. Using a conductive film obtained by drying as a positive electrode, a carbon material, an organic polymer compound, and an alkali metal salt are dissolved in a solvent, and this is cast on a substrate, and the conductive film obtained by drying is obtained. By using a conductive film as a negative electrode, an organic polymer compound and an alkali metal salt are dissolved in a solvent between the two electrodes, and this is cast on a substrate, and a solid electrolyte obtained by drying is interposed. It is possible to easily produce thin, uniform, positive electrodes, negative electrodes, and polymer solid electrolyte films with a large degree of freedom in shape,
In addition, there is no need to worry about leakage of the battery or decomposition of the electrolyte, and self-discharge can be suppressed.

Further, in particular, the thickness of the electrode can be reduced, and an effect of easily manufacturing an ultra-thin battery can be obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the structure of the battery of the present invention, and FIGS. 2 and 3 are diagrams showing the discharge characteristics of the battery of the present invention and the comparative battery after storage, respectively. DESCRIPTION OF SYMBOLS 1 ... Positive electrode film, 2 ... Negative electrode film, 3 ... Solid electrolyte film, 4 ... Insulating sealing material, 5 ... Positive electrode package, 6 ... Negative electrode package.

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-64-657 (JP, A) JP-A-1-319268 (JP, A) JP-A-62-12064 (JP, A) 105269 (JP, U) (58) Field surveyed (Int. Cl. ⁷ , DB name) H01M 10/40 H01M 4/02-4/04

Claims (1)

(57) [Claims] 1. A conductive film obtained by dissolving an inorganic metal compound or a conductive polymer, an organic polymer compound and an alkali metal salt in a solvent, casting this on a substrate and drying. Is used as a positive electrode, a carbon material, an organic polymer compound, and an alkali metal salt are dissolved in a solvent, and this is cast on a base material, and the conductive film obtained by drying is used as a negative electrode. A solid electrolyte battery in which an organic polymer compound and an alkali metal salt are dissolved in a solvent, cast on a substrate, and dried to interpose a solid electrolyte.