A method for predicting the cycle life of lithium-ion batteries based on the expansion of pole pieces

Abstract

The invention discloses a method for predicting the cycle life of a lithium ion battery based on the expansion degree of a pole piece, and belongs to the technical field of lithium ion battery cycle life testing. The method includes: increasing the cycle number of the same batch of lithium batteries with a fixed gradient, and establishing a relationship curve between the cycle number and the capacity retention rate; disassembling the tested lithium ion battery after discharging; The ion battery is cycled, and the pole piece swelling degree is photographed and calculated; the relationship curve between the capacity retention rate and the pole piece swelling degree is established; the lithium ion battery to be predicted is cycled for a certain number of weeks and then disassembled, and the pole piece swelling degree and the pole piece swelling degree are calculated. Capacity retention rate; calculate the cycle life of lithium-ion batteries. The invention provides a method for predicting the cycle life of a lithium ion battery based on the expansion degree of the pole piece. Based on the change of the expansion degree of the pole piece during the battery cycle, the battery life is predicted by fitting and calculation of the measured data after a short-term cycle, which is consistent with the actual test. The results are more consistent and easy to follow.

Description

technical field [0001] The invention relates to the technical field of cycle life testing of lithium ion batteries, in particular to a method for predicting the cycle life of lithium ion batteries based on the expansion degree of pole pieces. Background technique [0002] Cycle life is an important indicator that limits the practical application of lithium-ion batteries. In the field of power batteries, it is generally believed that when the battery capacity drops to 80% of the rated capacity, it can no longer be used in electric vehicles. However, the conventional lithium-ion battery cycle life test method takes a long time and takes up a lot of manpower and material costs. Therefore, it is necessary to find a method that can quickly predict the battery life. [0003] The Chinese patent (Notice No. CN107144790A) provides a method for predicting the cycle life of lithium-ion batteries. By measuring the impedance spectra of different cells and comparing the relationship betw...

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Problems solved by technology

[0004] The purpose of the present invention is to provide a method for predicting the cycle life of a lithium-ion battery based on the degree of expansion of the pole piece to solve the existing method for predicting the life of a lithium-ion battery. The process is complicated, takes a long time, and is affected by many factors , resulting in the inability to objectively predict the cycle life of lithium-ion batteries

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