关键词: 锂离子电池, 硅基负极, 针刺, 热失控

Abstract:

It is of great significance to study the thermal runaway of lithium-ion power batteries to create an early warning system and to optimize the design of batteries to prevent thermal runaway. In this work, we investigated the thermal runaway characteristics of different anode materials at different states of charge (SOC) of the batteries using the positive active material NCM811. The heat generated by thermal runaway was calculated using the equivalent temperature of a steel nail, and was then converted into the heat released per unit capacity with varied SOC. Heat transfer in the form of flame and ejected high-temperature solids were also analyzed. The studies indicated that at the same SOC, cells with a SiO_x/graphite anode exhibited more severe thermal runaway than cells with graphite only anodes. When the SOC was 25%, the cells with SiO_x/graphite anode still experienced severe thermal runaway during the penetration test, while the cells with a graphite only anode showed relatively mild thermal changes. When the batteries with a SiO_x/graphite anode were at 100% SOC, 50% SOC, and 25% SOC, the region surrounding the battery was heated to a dangerously high temperature that could endanger the thermal propagation of nearby batteries. The weight loss of the battery in the nail penetration test increased with a higher SOC, and the weight loss ratio of the 100% SOC SiO_x graphite anode battery was the highest, reaching 75.2%.

Key words: lithium-ion battery, SiO_x/graphite anode, nail penetration, thermal runaway