复合三元电池高温循环劣化分析

Degradation analysis of composite ternary battery after high temperature cycle

选用LiNi_(0.6)Co_(0.2)Mn_(0.2)O_2(NCM)和LiMn_(0.8)Fe_(0.2)PO_4(LMFP)复合正极材料,与石墨负极材料制成额定容量为38 Ah的2714891型电池,研究55℃下电池的循环性能,对影响循环性能的电解液和电极进行分析。负极容量衰减是高温循环性能衰减的主要因素,负极石墨比容量测试分析发现其容量损失占负极总损失的85.1%。石墨电化学阻抗谱(EIS)测试结果表明:高温循环后,石墨表面脱嵌锂活性降低,电化学反应难度增大;扫描电子显微镜(SEM)与BET比表面积测试表明:石墨表面结构破坏,体相发生膨胀。石墨本征结构的变化,是负极劣化的主要因素。

Using the prismatic Li-ion battery with capacity of 38 Ah based on LiNi0.6 Co0.2 Mn0.2O2 （ NCM ） and LiMn0.8 Fe0.2 PO4 （LMFP） blended cathode and graphite anode, the electrolyte and electrode influencing the cycle performance were analyzed. The anode was the main factor for cycle degradation. It was found that the graphite electrode represented 85.1% of anode capacity loss. Electrochemical impedance spectroscopy（EIS） test results showed that the activity of Li ＋ at graphite surface was reduced to lower level, which made electrochemical reaction more difficult, after high temperature cycling. SEM and BET specific surface area tests indicated that the surface structure of graphite was destroyed and the phase expanded. The change of graphite structure was the main factor for anode degradation.