JPS60258870A - Organic electrolyte lithium secondary battery - Google Patents

Abstract

PURPOSE:To improve the safety of a lithium secondary battery by properly maintaining its characteristics during charge-and-discharge by installing a hydrogen-absorbing alloy in the battery. CONSTITUTION:In a lithium secondary battery containing an organic electrolyte, a hydrogen-absorbing alloy 5 or a member containing the alloy 5 is placed over a generation element having a negative electrode 2, a positive electrode 3 and a separator 4 contained in a case 1 so that the alloy 5 does not touch the generation element. The alloy 5 is composed of at least one compound selected from among CaNi5, LaNi5, Ti0.6, Zr0.4 and Mn1.9Cu0.1. In the battery having the above structure, when the internal pressure of the battery increases to a given level due to hydrogen gas produced in the battery, the alloy 5 absorbs hydrogen to produce a metal hydride thereby resulting in reduced internal pressure of the battery. Consequently, there is no possibility that the battery expands or explodes.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to improving the quality and safety of organic electrolyte lithium secondary batteries.

Conventional configuration and its problems Organic electrolyte lithium batteries have high energy density.

It has the advantages of low-temperature properties, leakage resistance, and storage stability.
Batteries using manganese dioxide and carbon fluoride as positive electrodes have already received high praise in the market and are now widely used.

Currently, efforts are being made to develop rechargeable batteries that can be charged and discharged by taking advantage of these characteristics. During development, problems include decomposition of the electrolyte during charging, and problems with the lithium negative electrode (short circuit between the positive and negative electrodes due to dendrite-like precipitated lithium) during charging.

In particular, regarding the final problem of lithium precipitated in the form of dendrites, methods are being considered to completely reduce this by using all lithium storage alloys, by using additives, or by making the negative electrode capacity larger than the positive electrode capacity. ing.

Although lithium batteries are required to be non-aqueous as a basic principle, moisture that is adsorbed or built into the battery power generation element or moisture that is brought in from the atmosphere during battery assembly is unavoidable. In lithium-secondary batteries, the negative lithium surface is
Thermal force 3 ＼ Passive film formed by chemical reaction with electrolyte solvent, e.g. L12CO3
Even if there is about 11,000 pp of water in the electrolyte, it will not react any further with lithium, and there will be no major difference in battery characteristics.

However, in lithium secondary batteries, according to the following formula,
During charging, active atomic lithium is generated, so if water molecules are present near the atomic lithium at this time, hydrogen gas is generated according to the following formula: Li + H20 → LiOH-1
-V2H2+. The presence of hydrogen gas was confirmed by gas chromatography analysis. This generation of hydrogen gas continues as the water present in the battery is consumed.

In addition, a small amount of moisture from the atmosphere also enters through the battery seal. This moisture also causes gas generation. This generated water increases the internal pressure of the battery.When the internal pressure increases, the battery bulges.
In some cases, the problem of bag breakage occurs. At the same time, when the internal pressure increases, a problem arises in that hydrogen gas remains between the positive and negative electrodes, increasing the internal resistance. In addition, in the case of a red wire, Joule heat is generated due to the electrical resistance of the lead wire itself, causing the lead wire to become red hot.

In this case, hydrogen gas burns, and since an organic solvent is used in the electrolyte, there are internal pressures that are important for safety, such as ignition of the organic solvent and melting of the lithium negative electrode.

Therefore, the present inventors have discovered a method to eliminate or alleviate these problems that lithium secondary batteries have.

Purpose of the Invention The present invention provides a lithium secondary battery in which a hydrogen-absorbing alloy is installed inside the battery, and when the internal pressure of the electric oil increases due to the generated hydrogen gas, the alloy absorbs hydrogen at a certain pressure or higher, causing the metal to absorb hydrogen. As it becomes a hydride, the internal pressure of the battery decreases,
The above-mentioned dangers are eliminated and the characteristics of the battery can be appropriately ensured.

58.

Structure of the Invention The present invention uses calcium nickel (CaN15), lanthanum nickel (La
N15) or titanium zirconium manganese copper (T
io6Zro4Mn, Cuo, ) alloy in the battery,
The power generation element is installed in a non-contact manner.

Description of examples The figure shows a cross-sectional view of a battery used in an example of the present invention.

In the figure, 1 is the thickness of the nickel plated O, ellJl
1 Case that also serves as a negative electrode terminal with an outer diameter of 17.0mm, 2 is a negative electrode lithium with a thickness of 0.38NII+ and a length of 105ff.

A lithium sheet with a width of 23 mm is crimped onto a nickel expanded metal, and this is further welded to the case 1. 3 is a positive electrode made of commercially available vanadium pentoxide (v205
) 100 parts by weight of the product heat-treated at 800°C for 6 hours, mixed with 11 parts by weight of acetylene black and 20 parts by weight of a fluororesin binder, and 6.0 g of the expanded current collector made of natanium was mixed into medium and b. Thickness: 0.68, length: 1
00 sake, filled to a width of 25 mm. The negative electrode 2 and positive electrode 3 are spirally wound with a polypropylene nonwoven fabric separator 4 interposed therebetween, and are housed in a case 1.

5 is a molded body containing a hydrogen storage alloy, in which 0.5 g of lanthanum nickel alloy (LaN15) is mixed with 0.2 g of activated carbon powder.
g, thickness 1.5 with 0.16 g of polypropylene powder
111111, is molded into a perforated disk shape with an outer diameter of 24 mm and a hole of 6 mm in diameter in the middle and U portion. This molded body is placed above the power generation element so that it does not come into contact with it. 6
is a rivet-shaped positive electrode connector made of titanium, and is integrated by caulking with a nickel-plated ring that also serves as a positive electrode terminal 8 through a hole in the center of the polypropylene insulating gasket 7. 9 is a jacket made of polyvinyl chloride. As the electrolyte, a methyl formate solution of lithium hexafluoroarsenate (Li1sF6) with a concentration of 1.5 mol/e is used and is injected into the 2.5 fi f battery. Let's say this battery is a person.

7 ＼ In addition, in order to confirm the hydrogen gas absorption ability of the electrolyte,
Water was added to give 600 and 11000 pp. For comparison, we prototyped a battery B using a perforated disk 5 of the same thickness and composition except for the hydrogen storage alloy (other conditions were exactly the same as A). Batteries A and B have a theoretical capacity of 560 mAh and a maximum total height of 33 mm.

Electro-oil A, B (z25mi at 20°C (0,5v,
Discharge for 14 hours at a constant current of /cA (approximately 62% depth)
Then, the battery was charged at 1o mi (0.2 mA/C+J) for 30 hours. This was regarded as one cycle, and six cycles of charging and discharging were performed. These batteries A and H were equipped with an internal pressure measuring device prior to charging and discharging, and Tables 1 and 2 show the battery characteristics, pressure, and behavior of the batteries at the end of charging. In addition, the internal resistance is 20'C and l'l! at AC I#IKHz! II was determined.

(Leaving space below) Placement I9--7 From the above, using a hydrogen storage alloy in a lithium secondary battery will ensure the battery characteristics and the impact it will have on the battery9.
This can be reduced by 1.

In the example, lanthanum nickel (L
aNi5)'r: Calcium nickel (
CaN15) Yatitan zirconium manganese copper (Tio
6Zro4Mn19Cuo1) alloy may be used.

Effects of the Invention As described above, according to the present invention, by using a hydrogen storage alloy in a lithium secondary battery, battery characteristics can be ensured and the influence on the battery can be reduced during charging and discharging.

[Brief explanation of the drawing]

The figure shows a cross-sectional view of a battery used in an example of the present invention. 2...Negative electrode, 3...Positive electrode, 5...
Hydrogen storage alloy.

Claims (1)

[Claims] (1) An organic electrolyte lithium secondary battery characterized in that a component containing a hydrogen-absorbing alloy, such as Takeko, is built into the battery in a non-contact state with a power generation element. ? ) The hydrogen storage alloy is calcium nickel (CaNi5
), lanthanum nickel (LaN15) and titanium zirconium manganese copper (71662184Mn1.Cuo
The organic electrolyte lithium secondary battery according to claim 1, comprising at least one alloy of the group consisting of , ).