Lithium Difluoro(Oxalate)Borate‐Induced Interphase for High‐Voltage LiFe0.15Co0.85PO4@C Cathode by Solid‐State Synthesis

Herein, the effect of lithium difluoro(oxalate)borate (LiDFOB) as an electrolyte additive on the electrochemical performance of LiFe0.15Co0.85PO4@C (LFCP@C) cathode, synthesized by a scalable solid‐state synthesis method is reported. Galvanostatic studies revealed better electrochemical performance among the LFCP@C (LiDFOB: 0.5–2 wt%) in a half‐cell assembly compared to the LiFe0.15Co0.85PO4 in the absence of LiDFOB. Also, among the various concentrations of LiDFOB, the LFCP@C (LiDFOB—1.5 wt%) and LFCP@C (LiDFOB—2 wt%) are optimized as suitable candidates for further electrochemical studies owing to the high discharge capacities of 116 and 118 mAh g−1. In addition, the electrochemical impedance studies (EIS) exhibited an increase in the charge–transfer resistance (R ct) as the amount of LiDFOB was increased, whereas a lower R ct value is observed in the absence of additive. In addition, the diffusion coefficient calculation is calculated using the EIS data, which shows a diffusion coefficient in the order of ≈10−13 cm2 s−1. However, as the amount of LiDFOB is increased from 0 to 2 wt%, a decrease in the diffusion coefficient is observed owing to the formation of a stable and thicker passivation layer. Herein, a solid‐state synthesis of LiFe x Co 1−x PO4@C (X: 0.15) is reported, which is used as a cathode for lithium‐ion batteries. The use of lithium difluoro(oxalate)borate as an electrolyte additive takes part in the formation of a stable solid electrolyte interphase layer, hence improving the electrochemical stability.