锂离子电池正极材料热稳定性研究

Study on Thermal Stability of Cathode Materials for Lithium-ion Batteries

通过差示扫描量热法(DSC)系统研究了三元材料、电解液的热分解问题,分析了不同电位及电解液的添加量对三元材料热分解的影响。研究表明,三元材料热分解过程历经层状到尖晶石再到岩-盐相的结构转变,同时伴随着氧气的析出。Ni含量越高,电位越高,三元材料的热稳定性越差,热分解温度越低,热分解焓越大。对于高镍材料来说,其热稳定性与充电过程中的结构相变存在对应关系,在相变转折处热稳性出现明显差异。电解液的分解历经锂盐的分解吸热及分解产物与气化溶剂反应的放热过程,其加入量对三元材料的热分解过程有很大影响。

The thermal decomposition of ternary materials and electrolyte was systematically studied by differential scanning calorimetry(DSC).The effects of different potentials and the amount of electrolyte on the thermal decomposition of ternary materials were analyzed.The results show that the thermal decomposition process of ternary materials undergoes a structural transformation from lamellar structure to spinel and then to rock-salt phase,accompanied by the precipitation of oxygen.The higher the Ni content and the higher the potential,the worse the thermal stability of the ternary material with lower thermal decomposition temperature and greater thermal decomposition enthalpy.For high-nickel materials,there is a corresponding relationship between the thermal stability and the structural phase change during charging,and there is an obvious difference in thermal stability at the phase transition point.The decomposition of electrolyte goes through the endothermic process of lithium salt decomposition and the exothermic process of the reaction of decomposition products with gasification solvent,and the addition amount of electrolyte has a great influence on the thermal decomposition process of ternary materials.