Anhydride type film-forming electrolyte additives for high-temperature LiNi0.6Co0.2Mn0.2O2//graphite pouch cells

LiNi0.6Co0.2Mn0.2O2//graphite full cell, due to its high energy density as the most promising candidate for power batteries received increased attention, but the severe capacity loss under high-temperature conditions prevents their large-scale application. Here, glutaric anhydride (GA) and succinic anhydride (SA) as electrolyte additives are investigated to overcome the high-temperature problem of LiNi0.6Co0.2Mn0.2O2//graphite cells. Due to the unique film-forming features and high-temperature stability, the cells containing 0.5% GA and 0.5% SA can retain capacity retention of 91.2% and 92.4% stored at 60 ​°C for 15 days, corresponding to a negligible capacity loss of 4.6 and 0.8 mAh g-1 after 200 cycles, respectively. In addition, the lifespans of cells under 25 ​°C are also significantly extended by introducing GA and SA into the electrolytes. Electrochemical and spectroscopic techniques results indicate the full cell capacity loss is predominantly caused by the unstable anode solid electrolyte interphase (SEI) layer and a stable SEI film derived from GA and SA is formed on the graphite electrode surfaces. The SEI film can effectively inhibit the consumption of electrolytes and enhance the high-temperature performance of cells. This work paves a way for moderating high energy density cells' work under high-temperature operation by developing special anodic film-forming electrolyte additives.