锂离子电池浮充测试的鼓胀原因分析及改善

Study on cause of swelling in float-charged lithium ion batteries

对浮充测试中发生鼓胀的锂离子电池进行了深入分析,对电池产气成分、正负极阻抗、晶体结构、隔膜形貌及孔隙等情况进行了检测,结果表明:在浮充过程中,溶剂及添加剂在嵌锂负极表面发生还原反应,同时SEI膜发生不断的重整及修复反应,这些反应产物沉积到负极表面及隔膜孔隙内,导致靠近负极面的隔膜孔隙堵塞甚至贯穿,一旦沉积物刺穿隔膜,即引起正负极微短路,导致SEI膜的溶解和溶剂的氧化,释放出大量CO2,电池厚度迅速鼓胀。通过更换Gurley值高的隔膜可显著改善电池的浮充性能,原因在于在发生相同程度副反应的情况下,Gurley值高的隔膜可穿透性差,不易被沉积物刺穿发生微短路。

The swelling lithium ion batteries in float-charged test were studied by analyzing the state of each component in battery. The experimental results suggest that the solvents reduction and the SEI reforming and repairing reaction may be caused by the float-charging process. The reaction products deposited on the anode surface and penetrated into the micro pores of separator on anode side. And it is easy to cause a short circuit of cathode and anode, which will lead to the release of CO2 by the dissolution of SEI and oxidation of solvents. According to this, if the separator changed to one with lower Gurley value, the swelling rate of battery would be greatly reduced.