In-situ solution phase synthesis of LiFePO4@VSe2 composite as highly active cathode for Li-ion batteries

Abstract

Surface engineering of transition metal oxide cathode materials for Li-ion batteries is highly important to achieve high-capacity retention, high-rate capability, and long-life term. In this study, VSe2 nanosheets are prepared and used as a surface sensitizer to enhance the electrochemical properties of LiFePO4 (LFP) cathode material. The LiFePO4 @VSe2 (LFP@VSe2) composite is formed by anchoring 1D-LFP particles with the as-prepared 2D-VSe2 nanosheets by using an in-situ solution phase technique. When the LFP@VSe2 composites are used as cathode materials for Li-ion batteries, the Li surface-controlled storage behavior of the batteries is reasonably enhanced. The performance is attributed to the improvement in the inherent Li-ion conductivity of LFP particles, thereby inhibiting surface diffusion drawbacks and decreasing charge transfer resistance. The exterior VSe2 attached to the LFP serves as a second electrically conducting layer to increase conductivity into the entire electrode. Thus, these conditions enhance the electron transfer kinetics and surface stability of the LFP cathode. LFP@VSe2 composite cathode exhibits an ultrastable specific capacity of 166.5 mAh g−1 after 100 cycles @ 0.1 C and can retain a specific capacity of 146.7 and 46.5 mAh g−1 after 700 and 2000 cycles respectively at a current rate of 0.3 C and 10 C.