LiNi0.8Co0.15Al0.05O2/石墨锂离子电池高荷电存储老化机理研究

高荷电存储寿命对锂离子电池的使用性能具有重要影响, 但是相关研究却较为缺乏。本研究通过高温加速实验, 研究了LiNi_0.8Co_0.15Al_0.05O₂(NCA)/石墨锂离子电池在55 ℃下的存储寿命, 分析了正负极材料在电池寿命终点时的电化学性能和界面变化。研究结果表明, 在55 ℃、高荷电状态下NCA/石墨锂离子电池的存储寿命约为90 d。在寿命终点时, 正负极活性材料的容量有一定下降, 但不是电池容量衰减的主要原因。界面分析表明, 存储后负极表面固体电解质界面(SEI)膜增长明显, 而正极表面固体电解质界面(PEI)膜无明显变化。SEI膜的增长主要是由于电解液溶剂和锂反应, 造成石墨内锂损失, 使电池内可循环锂减少, 这是NCA/石墨电池在存储过程中容量损失的主要原因。

Storage Aging Mechanism of LiNi0.8Co0.15Al0.05O2/Graphite Li-ion Batteries at High State of Charge

Storage life at high state of charge is a key factor affecting the application of Li ion battery,but the related mechanism research is insufficient.In this study,the storage life of LiNi_0.8Co_0.15Al_0.05O₂(NCA)/graphite battery was evaluated via accelerating experiment at elevated temperature,and the electrochemistry performances and interface properties of fresh and aged active materials were analyzed.Storage experiment shows that the storage life of NCA/graphite battery at high state of charge under 55℃is about 90 d.Electrochemical test shows that the capacities of NCA and graphite decrease when the batteries reach the end of life,but that is not the main cause inducing capacity degradation.Interface analysis illustrates that the solid electrolyte interface(SEI)film on graphite anode significantly grows when batteries reach the end of life,while the positive solid electrolyte interface(PEI)film on NCA cathode keeps basically unchanged.The growth of SEI film on graphite owing to the decomposition of carbonates in electrolyte results in Li loss in anode,which contributes to the capacity loss of NCA/graphite battery during the storage aging at high state of charge.