Capsules and lithium-ion batteries

Abstract

The invention provides a capsule and a lithium ion battery. Capsules are used to be contained in lithium-ion batteries, including capsule walls and capsule cores. The material of the capsule wall has a melting point of 100°C to 160°C and is insoluble in the electrolyte of the lithium-ion battery; the gasification temperature of the material of the capsule core is not It is lower than the melting point of the material of the capsule wall and not higher than 400°C. The gas formed by the gasification of the material of the capsule core is a flame-retardant gas, which is compatible with the electrolyte vapor and / or Combustible fumes / combustible fumes are mixed and ejected from the outer packaging of lithium-ion batteries. The lithium ion battery includes the aforementioned capsule accommodated therein. When the lithium-ion battery is working normally, the capsule will not affect the electrochemical performance of the lithium-ion battery; when the thermal runaway of the lithium-ion battery occurs, the capsule wall ruptures and the material of the capsule core is released and further vaporized to form a flame-retardant Gas, so as to exert the flame-retardant function of the capsule, so as to achieve flame retardancy and improve the safety performance of lithium-ion batteries.

Description

technical field [0001] The invention relates to the field of batteries, in particular to a capsule and a lithium ion battery. Background technique [0002] The application of lithium-ion batteries in the field of new energy vehicles is becoming more and more widespread. However, reports of lithium-ion battery safety accidents have also increased significantly, such as the battery fire of Shanghai electric bus No. The taxi collided and caught fire, etc. Therefore, more and more attention has been paid to the safety performance of lithium-ion batteries. The common causes of lithium-ion battery accidents are mechanical abuse, that is, accidental collisions, extrusions, drops, etc. lead to internal short circuits in lithium-ion batteries; harsh operating environments, such as long-term operation in high-temperature environments; improper use or other reasons. Abuse, such as overcharge, overdischarge, etc. Normally, when the temperature of a lithium-ion battery reaches 100°C, ...

AI Technical Summary

Problems solved by technology

However, this method has its own defects. Although it can cut off the connection between the lithium-ion battery and the outside, it cannot prevent the internal reaction of the lithium-ion battery from continuing, or even thermal runaway.

(3) By improving the design of lithium-ion batteries, such as using a positive temperature coefficient thermistor, when the temperature exceeds a certain temperature, its resistance value increases stepwise with the increase of temperature, and it will fuse when it reaches a certain temperature. The thermal self-closing diaphragm is similar, and it cannot prevent the reaction inside the lithium-ion battery from continuing, and thermal runaway may also occur

However, studies have found that directly adding flame retardant additives to the lithium-ion battery electrolyte will greatly affect the electrochemical performance of the lithium-ion battery, such as affecting the formation of the SEI film on the negative electrode, which will lead to the electrolysis of the exposed negative electrode active material and the lithium-ion battery. The liquid solvent directly contacts and undergoes a reduction reaction, producing a large amount of gas, and even graphite peeling, which will cause the lithium-ion battery to lose its function

Images