Abstract:

Low-temperature environment seriously affects the battery discharge performance. Considering the influence of various preheating methods on the temperature field distribution of the battery, this paper used insulating oil immersion to heat the NCM811 battery. The temperature rise rate of the battery and the temperature difference in the battery surface during the preheating process in different low-temperature environments and the discharge parameters of the battery under distinctive SOC during 1C discharge were tested. The results showed that the NCM811 battery had good low-temperature performance, and preheating was very important for low SOC discharge. When SOC was lower than 33.3%, it was almost impossible to discharge without preheating at -20℃. Preheating could significantly improve the battery discharge performance at low-temperature and reduce the internal resistance. The rising rate of battery temperature could reach 0.31℃/s when the internal temperature of battery was preheated to 0℃ in a low-temperature environment of -20℃. For the initial battery states of 100% SOC and 33.3% SOC, the corresponding ohmic internal resistance of the battery decreased to 39.5% and 37.9% after preheating, respectively, and the polarization internal resistance decreased to 15.4% and 21.1% after preheating. Even in the initial state of 33.3% SOC, the released capacity at the 1C discharge rate could reach 81.68% of the charged.

Key words: Li-ion battery, immersing preheating, insulating oil, rate of temperature rise, discharge capacity

摘要：

低温环境严重影响了电池放电性能，综合考虑多种预热方法对电池温度场分布的影响，利用绝缘油浸没加热NCM811电池，测试了不同低温环境下预热过程电池的温升速率、电池表面温差、不同电池剩余容量（SOC）下的电池1C放电时的放电参数。结果表明，NCM811电池低温性能良好，但是预热对于低SOC放电很重要，当SOC低于33.3%时，在-20℃的环境下，不预热则几乎无法放电。预热能明显改善低温下的电池放电性能、减小内阻，在-20℃的低温环境中将电池内部温度预热至0℃时，其温升速率可以达到0.31℃/s，对于100% SOC与33.3% SOC的初始电池状态，其对应的电池欧姆内阻分别降低至预热前的39.5%和37.9%，极化内阻则降低至预热前的15.4%和21.1%，即使是33.3%SOC的初始状态，1C倍率放出的容量可以达到充入容量的81.68%。

关键词: 锂电池, 浸没式预热, 绝缘油, 温升速率, 放电容量