Effect of LiBOB Additive on the Electrochemical Performance of LiCoPO₄

Abstract

Solid-state method is used to synthesize sub-micron size lithium cobalt phosphate, LiCoPO 4 particles. Powder X-ray diffraction pattern reveal the formation of pure phase orthorhombic structure with pnma space group. Electrochemical properties of LiCoPO 4 are evaluated in half-cell configurations with conventional 1 M LiPF 6 ethylene carbonate (EC): diethyl carbonate (DEC) electrolyte solution. Interestingly, increasing charging potential leads to the decrease in re-insertion potential as is confirmed by cyclic voltammetric (CV) measurements. Galvanostatic studies corroborated CV analysis and suggest that higher charge potential delivers maximum discharge capacity, but with severe capacity fade upon cycling. Incorporation of lithium bis(oxalato)borate (LiBOB) in conventional electrolyte solutions certainly enhances the cycleability of LiCoPO 4 electrode, for example 3 wt% of LiBOB comprising electrolyte shows capacity retention of 74% of its initial discharge capacity after 25 cycles. The present study elucidates LiBOB addition is one of the unique approaches to alleviate the capacity fade of LiCoPO 4 during cycling.