JPH02256164A - Organic electrolyte battery - Google Patents

Abstract

PURPOSE:To permit the internal impedance rise of a battery to be restrained in conservation at a high temperature by using steel with a specific amount of molybdenum and chrome contained for a battery case and using the same tape of metal material as the battery case for a positive collector. CONSTITUTION:Alkaline metal is used as active material for a negative electrode 3, metal oxide or carbon fluoride as active material for a positive electrode 5 and organic solvent for electrolyte. Steel which contains 1-3wt.% molybdenum and 15-20wt.% chrome is used as materials for a positive collector 4 and a battery case 1 in contact the positive electrode 5. As the materials for the battery case 1 and the positive collector 4 are used which are the same type of metal materials in this way, the materials for the battery case 1 and the positive collector 4 allow internal impedance rise to be restrained in conservation at a high temperature, compared with different types of metal materials.

Description

[Detailed description of the invention] Industrial applications The present invention relates to improvements in organic electrolyte batteries.

Conventional technology organic electrolyte batteries have high energy density, storage stability,
Due to its excellent leakage resistance, it is currently widely used as a power source for small electronic devices such as watches and calculators, as well as precision equipment such as cameras and computers.

These organic electrolyte batteries use lithium as the negative electrode active material, fluorocarbon or metal oxides such as manganese dioxide as the positive electrode active material, and propylene carbonate, propylene carbonate, etc. as the electrolyte.
LiBF4, Lieβ0 is used to impart conductivity to one or more mixed solvents of γ-butyrolactone, 1゜2 dimethoxyethane, dioquinrane, etc.
A solution of lithium salt such as 4 is used.

Since this type of battery has a high battery voltage, it is very difficult to select materials for forming the battery case, positive electrode current collector, sealing plate, etc. For example, if nickel-plated steel, nickel, etc., which are used for dry battery sealing plates and battery cases, are used in the battery case, these metals will gradually dissolve in the electrolyte during the battery storage period. These dissolved metals become ions in the electrolytic solution and precipitate on the surface of the negative electrode, leading to an increase in internal resistance and, as a result, deterioration of discharge capacity. In addition, if the metal is significantly dissolved, a hole is formed in the battery case, causing liquid leakage.

3B-7 To prevent these things, it is desirable to use a metal with a higher potential than the active material of the positive electrode in the organic electrolyte. Forms a current collector. Specifically, steel containing about 30% by weight of chromium is used.

Problems to be Solved by the Invention However, steel containing about 30% by weight of chromium has the drawback of being hard and having poor workability. Therefore, the sealing mold is changed.
In the process of sealing the battery opening, the sealing process may cause stains and scratches on the side of the battery case, and part of the periphery of the opening of the battery case may peel off, and the peeled metal pieces may cause damage.
There was a problem in that the sealing plate and the battery case were short-circuited, causing voltage failure and discharge capacity failure. In addition, since the positive electrode current collector material is made of steel containing about 30% by weight of chromium, there is a problem that the cutting cutter easily collapses when cutting the hoop of the positive electrode current collector material and spotting it on the battery case. In consideration of corrosion resistance, Ti was used for the positive electrode current collector material, but since the metal was dissimilar to the battery case material, a corrosion potential was generated and the internal impedance of the battery increased during high-temperature storage.

The present invention is intended to solve these problems, and aims to suppress the increase in internal impedance during high-temperature storage, improve storage performance, and at the same time eliminate voltage failures during the manufacturing process. .

Means for Solving the Problems In order to solve the above problems, the present invention uses 1 to 3% by weight of molybdenum as the battery case material and positive electrode current collector material.
Steel containing 15 to 20% chromium by weight is used.

This structure reduces the chromium content compared to conventional battery case materials, improving processability and reducing battery voltage defects and appearance defects such as scratches during the case sealing process described above. The incidence can be reduced. In addition, since the same type of metal is used for the battery case and the positive electrode current collector, the battery interior has better corrosion resistance than those using different metals, especially when stored at high temperatures. It is possible to suppress the increase in impedance. Furthermore, since the amount of chromium, which is a rare metal, used can be reduced, the material cost is less than half that of conventional products, making it extremely economical.

Examples Below, examples of the present invention are shown in Figures 1 to 6, Tables 1 and 2.
This will be explained with reference to.

FIG. 1 shows a flat organic electrolyte battery of lithium-fluorocarbon yarn in an example. In the figure, reference numeral 1 denotes a battery case that also serves as a positive terminal, and is made of the composition according to the present invention described above. An example of its composition in weight percentage is as shown in Table 1, which corresponds to 5US444 of stainless steel in the JIS standard.

(hereinafter referred to as gold and white) 2 is a sealing plate made of the same material, and 3 is a negative electrode active material, lithium, which is press-bonded to the sealing plate 2, and has a capacitance of 165 mAh. A positive electrode current collector 4 is made of 5US444, which is the same material as the battery case 1, and is spot welded to the inner surface of the battery case 1.

5 is a positive electrode mixture, which includes 100 parts by weight of fluorocarbon as an active material, 10 parts by weight of acetylene black, and 1 part by weight of a fluororesin binder.
A mixture of 4 parts by weight was molded into pellets. 6 is a separator made of polypropylene nonwoven fabric.

The electrolytic solution contains 1 mole of lithium fluoroborate in a mixed solvent of equal volumes of propylene carbonate and 1,2-dimethoxyethane.
A solution dissolved at a ratio of β was used.

After impregnating the negative electrode fixed to the sealing plate and the positive electrode fixed to the case with an electrolytic solution, the peripheral edge of the separator was placed under a polypropylene insulating backing 7 and caulked together with the sealing plate to form a battery. This battery has a total height of 2
．． 5 mm, outer diameter 23 mm, and capacity 165 mAh.

This battery is a person. In addition, as a comparative product, a battery was created in the same manner as battery A, using Ti as the positive electrode current collector material and using the composition materials shown in A, B, and C in Table 1 in the case described above. B, C and Toshida. Note that battery B is a conventional product.

In this example, carbon fluoride was used as the positive electrode active material, but molybdenum oxide, manganese dioxide, silver chromate, etc., which are known as active materials for organic electrolyte batteries, were also used together with conductive materials and binders. All mixtures and formulations can be applied in the same manner.

Table 2 shows the internal impedances and voltage failure rates of these batteries A, A', B, and C immediately after assembly. Note that each data is an average value of N=100 pieces.

Table 2 From Table 2, A with low chromium content in the battery case,
It can be seen that the voltage defective rate immediately after assembly of battery A' is in the Q group, and the higher the chromium content of battery cases B and C, the higher the voltage defective rate immediately after assembly. This is because, as mentioned above, a part of the case was peeled off and the metal piece caused an external short circuit.

Next, in order to compare the storage characteristics of these batteries, 60
After 20 days, 60 days, and 100 days at 85°C and 85°C, the internal impedance of each battery and the discharge capacity were determined by performing constant resistance discharge at 15Ω in an atmosphere of 20°C. The results are shown in FIGS. 2 to 5. Each data is an average value of each battery N=20.

In Figures 2 and 3, the battery characteristics after storage at 60°C are as follows:
No difference is observed between A, A', and B, but a large increase in internal impedance and a decrease in discharge capacity are observed in C. In FIGS. 4 and 5, regarding the battery characteristics after storage at 85° C., an abnormal increase in internal impedance and a decrease in discharge capacity are observed for C. Next, comparing A, A', and B, as the number of days of storage at 85°C increases, the internal impedance of A' and B gradually increases compared to A, and the deterioration of discharge capacity gradually increases. I can see that it's happening.

From the above results, battery storage characteristics are abnormally poor when the battery case does not contain molybdenum.

Furthermore, even if the amount of chromium in the battery cases of A and A' is low, if the amount of molybdenum is the same as that of conventional product B, the battery cases exhibit comparable battery storage characteristics. In addition, as shown in A, the battery case and the positive electrode current collector are made of the same metal material, so that even when stored at a high temperature of 85°C, the material of the battery case and the positive electrode current collector remains unchanged, as shown in A'. Compared to those using dissimilar metal materials, the increase in internal impedance can be suppressed, and a good battery with less deterioration in discharge capacity can be obtained.

Further, FIG. 6 shows the degree of corrosion when steels with different molybdenum and chromium contents were stored at 70° C. for 1 month in the electrolytic solution described above, with a potential of 5 V applied to lithium. In FIG. 6, the amount of molybdenum is shown in a range of 0 to 1.5 weight units, but based on other studies, the preferred amount of molybdenum added is 1 to 3 weight units.

The steel used in this test was commercially available stainless steel or prototype steel, and the amounts of impurities other than chromium and molybdenum, such as manganese, carbon, nickel, silicon, and other impurities, were the same. not,
They are slightly different.

Effects of the Invention As is clear from the above explanation, the battery case is made of steel containing 1 to 3 weight percent molybdenum and 15 to 20 weight percent chromium, and the positive electrode current collector is made of the same metal as the battery case. By using this material, it is possible to suppress the increase in internal impedance of the battery during high-temperature storage compared to conventional batteries, and the workability of the case can be improved, which has the effect of eliminating voltage defects. Ta.

[Brief explanation of drawings]

FIG. 1 is a vertical cross-sectional view of a battery in an embodiment of the present invention, and FIG.
6 to 6 are diagrams showing the test results of the battery according to the present invention. 1... Case, 2... Sealing plate, 3...
...Negative electrode, 4...Positive electrode current collector, 5...
・Positive electrode mixture pellet, 6... Separator, 7.
...Insulating backing. Name of agent: Patent attorney Shigetaka Awano and 1 other person W1

Claims (1)

[Claims] (1) A battery that uses an alkali metal as the negative electrode active material, a metal oxide or carbon fluoride as the positive electrode active material, and an organic solvent as the electrolyte, and the positive electrode current collector material and battery case material that are in contact with the positive electrode. An organic electrolyte battery characterized by using steel containing 1 to 3% by weight of molybdenum and 15 to 20% by weight of chromium.