Amylopectin induces chain porous carbon skeleton boosting high performance of Na3V2(PO4)3

Abstract

Poor conductivity and stability seriously hinder the development of Na3V2(PO4)3 (NVP). In current work, we use a facile hydrothermal method to dissolve low-cost amylopectin in urea as an additional carbon source for in-situ modification of NVP. The unique amylopectin, as structure guide agent, induces the formation of one-dimensional chain structure to cross each other. The gas produced in the urea decomposition process promotes the generation of pores on the one-dimensional chain structure. Finally, one-dimensional chain porous carbon skeleton is constructed. Plentiful defects and active sites are formed in the N-doped carbon derived from urea, effectively promoting the ionic conductivity at interface of NVP grains. Notably, amylopectin can induce the O atom in NVP bulk to escape from the crystal and combine with the N atom in carbon layer to form an N–O bond, thus generating abundant oxygen vacancy inside the NVP bulk. This special effect can reduce the resistance of Na+ transport in the crystal and enhance the connect bonds between the active particles and coated carbon substrate. Thus, both the ionic conductivity and the structural stability can be significantly improved. Moreover, the ex-situ SEM/TEM/XRD/XPS/CV/EIS measurements after cycling all demonstrate the optimized crystal structure and unique morphology can be perfectly maintained during the prolonged cycling process. The optimized NVP/C,N-0.25 sample reveals 116.3 mA h g−1 at 0.1 C. Even at 80 C, it still releases 74.4 mA h g−1 and maintains 51.2 mA h g−1 after 12,000 cycles, corresponding to a low decay rate of 0.0026 % per cycle.