Improved cyclic performances of LiCoPO4/C cathode materials for high-cell-potential lithium-ion batteries with thiophene as an electrolyte additive

LiCoPO4/C composites were synthesized through a sol–gel route, followed by thermal treatment. X-ray diffraction patterns demonstrate the phase formation of LiCoPO4. Scanning electron microscopy and transmission electron microscopy show the network structure of LiCoPO4/C composites with the grain size ranging from 240 to 350 nm. For the electrochemical measurements of LiCoPO4/C composites in Li test cells, thiophene was added as an electrolyte additive. After 30 cycles, the discharge capacity of LiCoPO4/C composites was 92.8 mAh g−1 with 68% capacity retention; the improved cyclic performance was attributed to the combination of the network structure LiCoPO4/C composites and the thiophene addition to the electrolyte.

► LiCoPO4/C composites were synthesized through a sol–gel method, followed by thermal treatment.
► Thiophene was added to the conventional electrolyte as an additive.
► Polymerized thiophene film and carbon coating protect electrolyte from decomposition.
► Combination of C coating and thiophene electrolyte additive is effective for cyclic stability.