Improved Cycle Performance of LiNi0.8Co0.1Mn0.1O2 Positive Electrode Material in Highly Concentrated LiBF4/DMC

Charge/discharge characteristics of nickel-rich LiNi0.8Co0.1Mn0.1O2 cathode was investigated in highly concentrated lithium tetrafluroborate (LiBF4)/dimethylcarbonate (DMC) electrolytes with better electrochemical stability against oxidation. Raman spectra indicated that almost all DMC solvent molecules coordinated Li+ ions, and BF4− anions were likely to form aggregates (AGGs) with Li+ ions and DMC in the nearly saturated 8.67 mol kg−1 electrolyte. A LiNi0.8Co0.1Mn0.1O2|Li half-cell using the nearly saturated 8.67 mol kg−1 LiBF4/DMC showed a good cycle performance up to 50 cycles at C/10 rate with a capacity retention of 93.3%. Furthermore, cross-sectional SEM images and EDX mappings revealed that the highly concentrated electrolyte effectively suppressed not only oxidative decomposition of electrolyte solution on the particle surface, but also the particle fracture caused by crack propagation.