Dual-carbon coated Na3V2(PO4)3 derived from reduced graphene oxide and nanocellulose with porous structure for high performance sodium-ion batteries

The intrinsic electronic conductivity of Na3V2(PO4)3 (NVP) limits its further application. Herein, a synergetic strategy for in situ synthesis of porous NVP using reduced graphene oxide (rGO) and nanocellulose as additional carbon sources is proposed. Specifically, the carbonization of GO forms a highly graphitized rGO substrate, which effectively hinders the agglomeration of NVP particles. Meanwhile, the disordered and thin carbon coating layers are generated by the carbonization of nanocellulose, constructing an interconnected conductive network with rGO substrate. The dual-carbon coated network significantly improves the electronic conductivity to enhance the kinetic characteristics. Furthermore, the active NVP grains form a porous structure by epitaxial homogenous growth on rGO, which is conducive to further utilization of active substances. The mesopores in the sample can serve as storage sites for Na+ to provide capacitive contributions to the reversible capacity, which makes the capacity exceeds the theoretical value of NVP. The optimized CNF-GC-3 delivers amazing electrochemical properties. It submits an impressive reversible specific capacity of 123.77 mAh/g at 1C and maintains 99.70 mAh/g after 700 cycles, corresponding to a capacity decay rate of 0.028 % per cycle. Even at 60C, it still exhibits a prominent discharge capacity of 95.59 mAh/g.