Amorphous MnO2-modified Li3V2(PO4)3/C as high-performance cathode for LIBs: the double effects of surface coating

Abstract

MnO2-modified Li3V2(PO4)3/C (LVP/C) composites with plate-like structure were prepared via an improved sol–gel method followed by PVA-assisted suspension coating. The plate-like structure provides an enlarged contact area between the electrolyte and electrode, alleviating the Li+ diffusion and e− transport during the reaction process. The formed hybrid coating layer consisted of C and MnO2 has the double effects, that is, the formation of a complete continuous protective layer on the surface of LVP particles and the simultaneous improvement of electronic and ionic conductivities. This coating layer not only prevents the V3+ dissolution into the electrolyte, but also achieves the simultaneous Li+/e− diffusion at charge–discharge process. Benefiting from the unique structure and the synergistic effect of C and MnO2, the 3 wt% MnO2-modified LVP/C material (M-3) exhibits the most excellent electrochemical performance among all the samples. At a high current rate of 5 C, the M-3 electrode delivers a discharge capacity of 113.2 mAh g−1 and corresponds to capacity retention almost 100% after 100 cycles. Even at low temperatures of 0 and − 20 °C, the discharge capacities of M-3 are 102.4 mAh g−1 at 2 C and 81.6 mAh g−1 at 1 C, with capacity retention of 98.8 and 97.3%, respectively. The enhanced electrochemical performance of M-3 is mainly attributed to the cooperation of C and MnO2, which provides large specific surface area and complete conductive network. As a result, the MnO2-modified LVP/C composites with the plate-like structure can be a promising candidate as cathode materials for LIBs.