JPH02148576A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To extend a cycle characteristic by providing a negative electrode and a positive electrode that are composed of metallic lithium as well as a nonaqueous electrolyte that is obtained by having lithium salt resolved in an organic solvent, and by defining the volume of the electrolyte as 0.2 to 0.3cc per 100mAh of discharge capacity. CONSTITUTION:A separator 3 is provided between a positive and a negative electrodes 1 and 2, and entire body being wound in vortex so as to construct an electrode body. An upper insulating plate 6 and a lower insulating plate 7 are put on the upper and lower parts of the electrode body so as to be inserted into a case 8, wherein an electrolyte is poured after a stage part is formed on the upper part of the case 8. After a sealing plate 9 is installed therein, the opening end of the case 8 is caulked and built up. When the pouring amount is not more than 0.15cc per 100mAh of discharge capacity, permeation of solution between the positive and the negative electrodes is insufficient, and partial short-circuit occurs while the cycle is not extended. When it is not less than 0.35cc, dendrite is adhered on the bottom of a can, and internal short-circuit is observed. By defining the pouring amount of the electrolyte within the range of 0.2 to 0.3cc per 100mAh of discharge capacity, wettability inside the can is in the best condition.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and particularly to improvement of its cycle characteristics.

Conventional technology Conventionally, this type of non-aqueous electrolyte battery has been widely used as a power source for consumer electronic devices because of its high voltage, high energy density, and excellent reliability such as storage performance and leakage resistance. It is being Furthermore, recently there have been many attempts to convert this battery into a secondary battery. For secondary batteries, transition metal oxides and chalcogen compounds with a layered or tunneled crystal structure are being considered, with lithium ions in the negative electrode and lithium ions eluted from the negative electrode in the positive electrode. Oh,
During charging and discharging, lithium ions move between the positive and negative electrodes via the electrolyte. Currently, active efforts are being made to develop and research a cylindrical non-aqueous electrolyte secondary t1 (pond) having a spiral electrode.

Problems to be Solved by the Invention In a cylindrical non-aqueous electrolyte secondary battery having a spiral electrode, the amount of electrolyte is an important factor determining the cycle characteristics of the battery.

Regardless of the type of electrolyte used in this type of battery, if the amount of injected electrolyte is less than 0.2 cc per 100 mAh of discharge capacity, if the battery is repeatedly charged and discharged, the battery will discharge before the number of cycles increases significantly. The capacitance value decreases, and good cycle characteristics cannot be obtained. This is because the amount of liquid injected is insufficient, resulting in uneven wetting of the separator, and in reality, only a portion of the plate is involved in charging and discharging, and the amount of charge required per unit area of the plate is The current density of discharge is increasing.

As a result, dendrite-like lithium produced during repeated charging and discharging is more actively accumulated on the surface of the negative electrode lithium, penetrating the holes in the separator and causing a partial short circuit between the positive and negative electrodes. As a result, the voltage did not rise above 90 degrees during charging, and sufficient charging was not achieved.On the other hand, it is thought that the cycle characteristics are poor because the surface condition of the lithium is rapidly deteriorating.

In addition, the injection amount is 0.35 c per 100 mAh of discharge capacity.
In the case of more than c, a problem arises in that as the amount of liquid in the battery can increases, the volume that can be filled with the positive electrode, that is, the filling electric capacity, decreases in inverse proportion to the amount of liquid in the battery can. Furthermore, when a battery with a large amount of liquid was actually disassembled after being charged and discharged for several tens of cycles, dendrite-like lithium was found attached to the bottom of the can, indicating the risk of causing an internal short circuit.

This is because there is a large amount of extra liquid other than the liquid circulating between the positive and negative electrodes, so that the dendrite-like lithium cannot be held between the separator and the negative electrode, and moves inside the can and adheres to the bottom.

It is an object of the present invention to solve the above-mentioned problems, to determine the optimum range of the amount of liquid to be injected when configuring a battery, and to extend the cycle characteristics of the battery.

As a means to solve the problem, the present invention has been developed by reducing the injection amount to 0.2 to 3 CC per discharge capacity i1oomAh, regardless of the type of liquid.
That is.

Effect By setting the amount of electrolyte injected to 0.2 to 3 CC per person per 100 m of discharge capacity, the liquid surroundings between the positive and negative electrodes will be sufficient and the generation of dendrite-like lithium will be prevented. This means that the amount of excess liquid around the group can be kept to a minimum.

Example An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a cross-sectional view of a cylindrical lithium secondary battery used in an example. In the figure, the positive electrode plate 1 is chromium chloride (Cr20s).
) is filled into a core material made of expanded titanium metal and dried. 4 is a positive electrode lead plate made of the same material as the core material and spot welded to the core material.

The negative electrode plate 2 is made of metal lithium, and a negative electrode current collector 6 is crimped to the negative side thereof.

3 is a microporous film of polyolefin (polypropylene, polyethylene, or a copolymer thereof) having a three-dimensional pore structure (sponge-like) (the pore size is 0.01 to 0.00 mm in terms of charge/discharge characteristics and safety). The separator 3 is interposed between the positive and negative electrodes 1.2, and the whole is spirally wound to form an electrode body.

Then, while rotating the electrode body, hot air is blown from slightly above obliquely in the direction of the winding core of the electrode body to the separators protruding from the upper and lower end surfaces of the electrode, that is, the positive and negative electrodes 1.2. The electrode body is assembled by bending the electrode body while contracting it to complete the electrode body configuration. Note that the heating temperature varies depending on the material of the separator, but in this example, the heating temperature is 1.
The temperature was 40-180°C. Alternatively, a flat plate may be appropriately pressed against the bent portion to further enhance adhesion.

Next, there are upper isolation plates 6 above and below the electrode body, respectively. After applying the lower insulating plate 7 and inserting it into the case 8 to form a step on the upper part of the case 8, an electrolytic solution (in this example, a mixed solvent of propylene carbonate and 1,2-dimethoxy/ethane) is added. (using a solution of lithium perchlorate as a solute) is injected into the solution. When injecting liquid, operate under reduced pressure to achieve a uniform impregnated state in a short time. After attaching the sealing plate 9, the open end of the case 8 is sealed by crimp inward to complete the assembly of the battery.

In the present invention, the amount of liquid injected is 0.15°/100mAh.
Six types of cylindrical lithium secondary batteries, 2, 0.25, 0.3, and 0.35cc, were subjected to a cycle test.
I investigated its lifespan.

The test conditions in this case were a constant current of 100 m at 20'C, and a 600 m
It is repeatedly charged and discharged at human depths.

FIG. 2 shows the relationship between the liquid volume and the number of cycles obtained as a result of the above test. The cycle was considered to have ended when the charge/discharge depth fell to 300 mAh or less, which is 50% deterioration of the charge/discharge depth of 600 mAh.

As is clear from these results, the discharge field i1o.

In the range of 0.15 to 2 CC per mAh, as the liquid volume increases, the cycle life increases considerably in proportion.

This tendency becomes saturated at 0.25 cc per 100 mAh. Therefore, the injection volume is 100 m
If the amount is 0.15 cc or less per Ah, the liquid circulation between the positive and negative electrodes is insufficient, resulting in a partial short circuit, and the cycle cannot be extended.

In addition, when the test was stopped and disassembled after 100 cycles of charging for 6 types of batteries, the amount of liquid injected was 100 mA with a discharge capacity of 100 mA.
Regarding the 0.35 cc per h, adhesion of dendrites was observed on the bottom of the can, indicating the risk of internal short circuit.

From the above, in cylindrical non-aqueous electrolyte secondary batteries,
The optimal liquid amount is in the range of 2 to 0.3 cc per 100 mAh, in which case the separator should be evenly wetted, and the liquid between the electrode plate group and the can should be kept to a minimum. It is thought that the

Effects of the Invention As described above, according to the present invention, in a cylindrical non-aqueous electrolyte secondary battery, the injection amount of the E solution can be adjusted to 0.2 to 0.00% per 100 mAh of discharge capacity, regardless of the type of electrolyte plug. When the range is 3CC, the liquid inside the can is in the best condition.
Good cycle characteristics can be obtained.

In the examples, chromium pentoxide was used as the positive electrode active material, but other materials such as manganese dioxide, molybdenum trisulfide, and vanadium oxide (V2O5, V2O+51v308) were used.
-Titanium disulfide, copper oxyphosphate, vanadium sulfide (
V2S5>, LiMnO4, other chromium oxides, etc. may be used.

Further, although pure metallic lithium was used as the negative electrode active material, an alloy capable of intercalating and deintercalating lithium ions may be used.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view of a cylindrical battery in an embodiment of the present invention;
FIG. 2 is a diagram showing the relationship between the number of cycle life and the amount of liquid. 1...Positive electrode, 2...Negative electrode, 3...Separator. Name of agent: Patent attorney Shigetaka Awano and 1 other person f-
Seigen 2 - Part 2 of the amendment [CyoJ Procedural amendment dated 12th month, 1989 ■ Case description 1986 Name of patented invention Name of non-aqueous electrolyte secondary battery Case Address Name Representative Patent Filer 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture (582) Matsushita Electric Industrial Co., Ltd. Akio Tanii 4 Agent Address 1006 Oaza Kadoma, Kadoma City, Osaka Prefecture 571 Matsushita Ikufure & (around) drawing in Denki Sangyo Co., Ltd.

Claims (1)

[Claims] It is equipped with a negative electrode made of metallic lithium, a positive electrode, and a non-aqueous electrolyte obtained by dissolving a lithium salt in an organic solvent, and the volume of the non-aqueous electrolyte is 0.2 per 100 mAh of discharge capacity.
~0.3cc non-aqueous electrolyte secondary battery.