Electrochemically induced interface by LiBOB to enhance cycling performance of LiFe0.4Mn0.6PO4 cathode for lithium-ion batteries

Olivine-type lithium iron manganese phosphate (LFMP) combines the high energy density of LiMnPO4 with the high safety of LiFePO4, is considered to be one of the most promising cathode materials for the next generation. However, the Mn dissolution behavior due to the Jahn-Teller effect of Mn3+ irreversibly causes loss of active material during electrochemical cycling, accompanied by severe capacity decay and structural degradation, which is more severe at elevated temperature. Herein, in order to enhance the cycling performance of LFMP cathode material, the cathode-electrolyte interface is stabilized by inducing bis(oxalate)borate (LiBOB) decomposition electrochemically to form a CEI layer. Specifically, the capacity retention of the battery in the electrolyte containing 0.75 wt% LiBOB is 95.37 % after 200 cycles at 25degree celsius and 1C. (1C = 170 mA g(-1) ) The capacity retention is 89.17 % after 200 cycles at 55degree celsius and 1C, compared to only 72 % in the electrolyte without LiBOB. The superior cycling performance is attributed to the formation of a uniform CEI layer induced by LiBOB electrochemically, which inhibits the parasitic reaction between the cathode and electrolyte, reduces the dissolution of Mn in the active substance, enabling superior and safer cycling performance even at elevated temperature.