Method for assessing lithium ion battery safety through forced internal short circuit

Abstract

The invention discloses a method for assessing lithium ion battery safety through a forced internal short circuit. A hole is produced in a closed shell of a lithium ion battery to be assessed to keep a consistent pressure inside and outside the battery. Then with an overcharging method, lithium dendrites are forced to grow on the negative electrode until puncturing a separator film and causing an internal short circuit, and meanwhile the battery is checked to find out whether thermal runaway happens so as to assess the safety performance of the battery. The method is simple in operation and can simulate the situation that the lithium dendrites grow and puncture the separator film to cause the internal short circuit under an extreme condition during real charging. The newly-generated lithium dendrites have the same surface status, and the reproducibility is expected to be good.

Description

technical field [0001] The invention relates to a method for evaluating the safety performance of a lithium-ion battery, in particular to a method for evaluating the safety of a forced internal short circuit of a lithium-ion battery. Background technique [0002] Due to its higher specific energy compared with traditional secondary batteries such as lead-acid batteries and nickel-hydrogen batteries, lithium-ion batteries are widely used in consumer electronics, electric bicycles, electric vehicles, energy storage, etc. field. Generally, the cathode materials of lithium-ion batteries, such as lithium cobalt oxide, lithium nickel cobalt manganese oxide, lithium manganate and other transition metal oxide lithium salts, are unstable compounds in the charged state, and can decompose and desorb oxygen under high temperature conditions. The oxygen in the electrolyte may react with combustible substances such as the flammable components in the electrolyte, the graphite material in ...

AI Technical Summary

Problems solved by technology

[0006] This method is easy to implement and can simulate the internal short circuit phenomenon of the battery to a certain extent. However, for the following two reasons, the acupuncture test is not included in the UL standards in other application fields.

[0007] 1) Poor reproducibility: It is greatly affected by factors such as the material of the steel needle, the surface oxidation state, and the puncture speed, which leads to an increase in the chance of the experiment and poor reproducibility

[0008] 2) The so-called anti-acupuncture structure can cause a phenomenon similar to an external short circuit before the internal short circuit caused by the acupuncture, thus causing the shutdown of the diaphragm, and it is impossible to evaluate the safety of the battery during an internal short circuit under normal circumstances

However, it is a very complicated and highly skillful work to open the sealed battery case in a dry environment, implant a nickel nail between the positive and negative electrodes and then seal it, and then perform operations such as heating and pressing down, so in addition to JIS standards No other well-known standard currently takes this approach

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