Electrochemical Behaviors of a Vapor-Phase Polymerized Conductive Polymer Coated on LiV₃O₈ in Li-Metal Rechargeable Batteries

A new coating method called vapor-phase polymerization (VPP) is used to coat a conductive polymer on LiV₃O₈ (LVO) surfaces for the first time in lithium-metal secondary batteries to protect the interface layer and enhance the electrochemical properties of the cathode. The VPP method can be used to coat an appropriate amount of the polymer and homogeneously coat the LVO active material surfaces because of the use of vapor-phase monomers. The presence of the coating layer was confirmed by X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, and transmission electron microscopy. Polymer coating of LVO by VPP results in enhanced cyclic stability and rate capability at various C-rates. At 0.2 C-rate, it has high specific capacities of 254.7 and 272.2 mA h g^-1 in the first and second cycles, respectively. Further, the capacity retention is 94.6% from the 2nd cycle to the 100th cycle. The improved electrochemical performance is attributed to the homogeneously conductive polymer formed by VPP, which can improve the electrical conductivity of the active material and inhibit dissolution by preventing direct contact with the electrolyte.