Improvement of the cycling performance of LiCoO₂ with assistance of cross-linked PAN for lithium ion batteries

Highlights: • Cross-linked PAN coating was prepared without damaging the surface of LiCoO₂. • The coating layer owns good electronic conductivity and mechanical strength. • The cross-linked PAN coating layer is more sufficient than Al₂O₃ coating. • It shows much improved cyclability than that of bare and Al₂O₃ coated LiCoO₂. - Abstract: LiCoO₂ has been widely used in lithium ion batteries for digital electronic products. However, the limited cycling performance under high cut-off voltage hinders its commercial application. Many metal oxides and/or phosphorus coating have been reported to improve the cycling performance of LiCoO₂. In this paper, we report on cross-linked PAN coated LiCoO₂ composite as a cathode material for lithium ion batteries. The coating layer was obtained by intermolecular crosslinking of PAN polymer chain by heat treatment at high temperature in air. The air heating process avoids the possible damage arising from the carbon thermal reduction to the surface structure of LiCoO₂. Electrochemical test indicates that the LiCoO₂ with the cross-linked PAN coating layer shows much improved cycle performance compared with that of bare and Al₂O₃ coated LiCoO₂. These findings might also open new avenues to explore polymer coating for other cathode materials of lithium ion batteries