The cycle life and performance attenuation mechanism of Lithium battery

On the afternoon of March 31, 2016, the "OFweek2016 China lithium battery industry technology seminar" hosted by OFweek China high-tech industry portal and hosted by OFweek lithium power grid was held in the conference hall of hall 1 of Guangzhou Pazhou international procurement center. Many experts of lithium battery gather together to discuss the development trend and future trend of the industry. Professor He Yanbing from the department of energy and environment of Shenzhen graduate school of Tsinghua university delivered a keynote speech on "analysis of the mechanism of lithium ion battery life and performance attenuation".

Under high temperature, low temperature, rapid charging and other working conditions, performance attenuation of lithium ion battery is very serious, which greatly limits its range of use. Analyzing the performance attenuation mechanism and process of power battery under different working conditions is of great significance for promoting the development of new energy vehicle and power battery. Therefore, how to improve the performance of the battery to meet the vehicle power battery life requirements has become an urgent technical problem.

Taking LiFePO4/ graphite battery as an example, he analyzed the performance attenuation mechanism of power battery in detail through disintegration and non-disintegration technology, and drew the main conclusions of battery cycle capacity attenuation and shelf capacity attenuation. Among them, the attenuation of battery cycle capacity is mainly caused by the lithium loss in the positive electrode (FePO4 phase generation). For the first time, the coexistence of FePO4 and LiFePO4 was observed by TEM, and the lithium loss was consumed by the negative SEI film. Battery storage capacity attenuation is mainly caused by lithium loss in the positive electrode (FePO4 phase generation), which increases with the increase of temperature and SOC. By lithium supplement, FePO4 phase can be restored to LiFePO4.

He also elaborated on the influence and promotion process of extreme working conditions (such as high temperature, low temperature, over charge, over discharge, floating charge, etc.) on the aging process, and said: "to find the key influencing factors of battery capacity decline can better improve the service life of lithium ion battery and obtain better battery pack. Finally, he introduced the application of graphene conductive agent in different electrode systems and polymer gel electrolyte in li-sulfur batteries, and made an important summary of the development of cutting-edge battery technology.

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