Enhancing high-voltage cycling stability of LiCoO₂via a cyclized polyacrylonitrile coating

High voltage (4.6 V) is crucial for enhancing the specific capacity of lithium cobalt oxide (LiCoO₂, LCO) materials; however, this approach significantly compromises their stability. In this study, a cPAN-LCO-3 material was prepared by a simple solvothermal method, followed by coating with cyclized polyacrylonitrile (cPAN) obtained via heat treatment. The capacity retention rate of cPAN-LCO-3 after 100 cycles reached 80.1% with a voltage range of 3.0-4.6 V at 0.5C, while pristine LCO only maintained 50.6%. This is because the robust and conductive core-shell structure effectively acts as a physical barrier, inhibiting the "hexagonal-monoclinic-hexagonal" phase transition process of pristine LCO, thereby enhancing the cycling stability. At the same time, it significantly improves the discharge specific capacity and rate performance of LCO at 4.6 V, with its discharge specific capacity reaching 219.0 mAh g^-1 at 0.1C, which is higher than the discharge specific capacity of pristine LCO (204.2 mAh g^-1). This is due to the graphene-like cPAN (shell) structure coating, which facilitates rapid charge transfer and Li⁺ conduction.