JPH06150975A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PURPOSE:To provide a nonaqueous electrolyte secondary battery preventing the thermal runaway by efficiently discharging an electrolyte which is a reactant to the outside when the battery temperature rises. CONSTITUTION:A nonaqueous electrolyte secondary battery is constituted of a positive electrode, a negative electrode using lithium and lithium ions as an active material, and a nonaqueous solution containing a carbonate solvent, and the incombustible filling gas easily dissolved in the nonaqueous electrolyte is pressed into the battery. When battery temperature rises due to an abnormal use in the lithium secondary battery pressure-filled with the electrolyte with carbon dioxide, the electrolyte can be efficiently discharged to the outside of the battery, the safety can be improved, and the industrial value is very large.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly to a non-aqueous electrolyte secondary battery comprising a negative electrode using lithium as an active material and a non-aqueous electrolyte.

[0002]

2. Description of the Related Art As electronic devices are becoming smaller and lighter and portable,
Development of a high energy density battery is required as the power source. As a battery that meets such a demand, a battery using an electrode that releases and absorbs lithium metal such as a negative electrode, a lithium alloy with aluminum or the like, or a lithium ion such as carbon is being developed (in this specification, A negative electrode using these lithium or lithium ions as an active material is a lithium negative electrode, and a chargeable / dischargeable battery using the lithium negative electrode is referred to as a lithium secondary battery).

However, as reported in a battery using manganese dioxide as a positive electrode active material, when a lithium secondary battery is heated in an oven, spontaneous heat generation occurs due to a chemical reaction between a lithium negative electrode and an electrolytic solution. A battery may ignite due to thermal runaway (Extended Abstracts o
f Electrochemical Society Fall Meeting, Seattle, Wa
shington, p-85, 1990). The above report is an example in which the battery temperature rises due to oven heating, but it is expected that the battery temperature will rise due to external short circuit, internal short circuit, reverse charge, overcharge, etc. in the battery. Ensuring safety is extremely important for commercializing lithium secondary batteries.

Since it is considered that the spontaneous heat generation in the lithium secondary battery is caused mainly by the reaction between the lithium negative electrode and the electrolytic solution, it is difficult to react with lithium in order to improve the safety of the battery. An electrolytic solution may be used. From these viewpoints, an electrolytic solution using sulfolane as an electrolytic solution solvent has been proposed (Proceedings of the 59th Congress of the Electrochemical Society p-238), but the stability and cycleability of a lithium secondary battery are Since the reaction product of the lithium negative electrode and the electrolyte is also affected (Lithium Batteries, Edited by
JPGabano, Academic Press, New York, p-195 (198
8)), negative effects such as deterioration of charge / discharge cycle characteristics occur.

[0005]

On the other hand, as described above, it is considered that the thermal runaway of the battery is caused by the spontaneous heat generation due to the chemical reaction between the lithium negative electrode and the electrolytic solution, so that the battery temperature rises. At this time, if the electrolytic solution, which is a reactant, is efficiently released to the outside, further heat generation is suppressed and the thermal runaway state is not reached. However, a normal safety valve cannot efficiently discharge the electrolytic solution to the outside of the battery.
This is because the electrolyte is filled in the positive electrode active material and the fine pores of the negative electrode, and even if the safety valve is opened, it is not sufficient to discharge the electrolyte in these fine pores.

[0006]

In order to solve the above problems, a non-aqueous electrolyte secondary battery according to the present invention comprises a positive electrode, a negative electrode containing lithium and lithium ions as an active material, and a non-carbonate-based solvent. A non-aqueous electrolyte secondary battery using an aqueous electrolyte is characterized in that a non-flammable filling gas that is easily dissolved in the non-aqueous electrolyte is injected into the battery.

In the present invention, it is noted that the spontaneous heat generation of the battery in the reaction in the battery is mainly due to the reaction between the lithium negative electrode and the electrolytic solution, and when the battery temperature rises, the electrolytic solution which is the reaction material is efficiently discharged. It is characterized by being released to the outside and avoiding heat generation due to further reaction.

Specifically, the inside of the battery is filled with a gas which is well dissolved in the electrolytic solution and which is nonflammable. like this
The properties required of the filling gas must be such that it is well soluble in the electrolyte solution, nonflammable, and does not deteriorate the charge / discharge cycle characteristics of the battery. Carbon dioxide is an example of a gas having such characteristics. Carbon dioxide is a carbonate-based solvent such as propylene carbonate, ethylene carbonate, butylene carbonate,
Dissolves well in diethyl carbonate, especially propylene carbonate (Solvent Handbook, Asahara Teruzou et al., P-
627, Kodansha), it is reported that it is nonflammable and the charge and discharge characteristics are improved by addition (Extended Abstracts
of 6th International Meeting on Lithium Batterie
s, p-228 (1992)).

The pressure of the filling gas inside the battery at room temperature is preferably 5 kg / cm ² or more and 15 kg / cm ² or less. If it is less than 5 kg / cm ² , it may be difficult to impregnate with the electrolytic solution, while 15 kg / cm ²
If it exceeds, the pressure becomes too high and the safety valve may operate.

In manufacturing the non-aqueous electrolyte secondary battery according to the present invention, as shown in FIG.
Stack the negative electrodes, roll them up, and insert them into the battery can. After that, the battery can is evacuated with a rotary pump to reduce the pressure to preferably 3 mmHg or less, and then an electrolytic solution is injected. When injecting the electrolytic solution, the battery is evacuated, and then the electrolytic solution is pressurized and filled using a filling gas that is easily dissolved in the electrolytic solution. At this time, the injection pressure is 5 to 15 kg for the same reason as above.
/ Cm ² is good.

In the non-aqueous electrolyte secondary battery according to the present invention, when the battery temperature rises for some reason such as an external short circuit, the gas dissolved in the electrolyte is vaporized and the internal pressure of the battery is raised to quickly open the safety valve. Not only is it activated, but the electrolyte in the micropores of the positive electrode or negative electrode is also efficiently discharged to the outside of the battery.

[0012]

In the lithium secondary battery in which the electrolytic solution is pressurized and filled with carbon dioxide as described above, the electrolytic solution can be efficiently discharged to the outside of the battery even when the battery temperature rises due to some abnormal use. The safety can be improved.

[0013]

EXAMPLES Examples of the present invention will be described in detail below.

[0014]

EXAMPLE 1 P ₂ O ₅ was an amorphous V ₂ O ₅ was added 5 mol% and a positive electrode active material, using a 130μm thick lithium metal as the negative electrode, positive electrode and the negative electrode of the average pore diameter 0.15 [mu] m, the thickness 50μ
It is electrically insulated with a polyethylene separator of m and rolled up, and inserted into a battery can. After the battery can was evacuated to 3 mmHg by a rotary pump (see the figure), a mixed solvent system electrolytic solution of propylene carbonate and ethylene carbonate was filled as an electrolytic solution at a pressure of 12 kg / cm ² , and the filling gas was filled with argon. Was compared (1) with carbon dioxide and (2) with carbon dioxide. After charging and discharging (1) and (2) 25 times at 60 mA, a short circuit test through a resistance of about 40 mΩ and a UL standard heating test of a lithium primary battery (room temperature to 5 ° C. up to 165 ° C. per minute) The temperature was raised and the temperature was maintained at 165 ° C. for 10 minutes), and the presence or absence of ignition was examined. The results are shown in Table 1.
In the short circuit test, both batteries (1) and (2) did not ignite, but the safety valve was activated in (2),
It did not work in (1). However, in the heating test, while the battery of (1) ignited, the battery of (2) did not ignite due to the early operation of the safety valve, and it is understood that the effect of the battery safety is great.

[0015]

[0016]

[Embodiment 2] The charging pressure of a battery having the same configuration as that of Embodiment 1 is 5
About the battery (kg / cm ² ) using argon as a filling gas (3) and carbon dioxide (4), after charging and discharging at 60 mA 25 times, about 4
Short circuit test through 0mΩ resistance and UL standard heating test of lithium primary battery (165 ° C from room temperature to 5 ° C per minute)
The temperature was raised to 165 ° C. and maintained for 10 minutes), and the presence or absence of ignition was examined. The results are shown in Table 2. In the short circuit test, neither battery (3) nor battery (4) ignited. Further, in the heating test, the battery of (3) is ignited, whereas the battery of (4) does not ignite due to the early operation of the safety valve, which shows that the effect of the battery safety is great.

[0017]

[0018]

As described above, in the lithium secondary battery in which the electrolytic solution is pressurized and filled with carbon dioxide, the electrolytic solution is efficiently discharged to the outside of the battery even if the battery temperature rises due to some abnormal use. Therefore, safety can be improved, and its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining a method for manufacturing a non-aqueous electrolyte secondary battery of the present invention.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Masahiro Ichimura 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A non-aqueous electrolyte secondary battery using a positive electrode, a negative electrode using lithium and lithium ions as an active material, and a non-aqueous electrolyte containing a carbonate-based solvent, wherein the non-aqueous electrolyte is inside the battery. A non-aqueous electrolyte secondary battery characterized in that a non-flammable filling gas that is easy to dissolve in is injected. 2. The non-aqueous electrolyte secondary according to claim 1, wherein the filling gas is carbon dioxide gas, and the carbonate-based solvent is propylene carbonate, ethylene carbonate, butylene carbonate, or diethyl carbonate. battery.