Improved electrochemical performance of a Li3V2(PO4)3 cathode in a wide potential window for lithium-ion storage by surface N-doped carbon coating and bulk K-doping

NASICON-structured monoclinic Li3V2(PO4)(3) (LVP) is considered as a promising cathode material. However, the disadvantages including low intrinsic electronic conductivity, low ionic conductivity and fast capacity fading at high voltage limit the application of LVP. In order to overcome these drawbacks of LVP and optimize its electrochemical properties, a LVP cathode material is successfully modified for the first time by combining surface N-doped carbon coating with bulk phase K+ doping after the in situ fabrication process in this paper. On the one hand, N-doped carbon coating is able to improve the electron transfer rate at the electrode/electrolyte interface and enhance the electrochemical reaction activity. On the other hand, bulk phase K+ doping can stabilize the crystal structure, limit the structural damage during the Li+ reinsertion process and improve the intrinsic conductivity of LVP. After collaborative modification with N-doped carbon coating and K+ doping, the electron conductivity and Li+ diffusion rate of LVP are improved obviously. Therefore, compared with singly modified LVP samples, the collaborative modified sample reveals better electrochemical properties, especially in the wide potential range of 3-4.8 V vs. Li/Li+. This novel modification method of surface N-doped carbon coating and bulk K+ doping is highly effective and can be widely used to optimize the electrical conductivity of electrode materials for Li-ion batteries.