Synthesis of 3-dimensional interconnected porous Na3V2(PO4)3@C composite as a high-performance dual electrode for Na-ion batteries

Three-dimensional (3-D) interconnected porous Na3V2(PO4)(3) coated with carbon (NVP@C) is synthesised by a simple modified sol-gel method. When 15 wt% glucose is used as the carbon precursor, the obtained NVP@C15 composite exhibits excellent electrochemical performance as a cathode as well as an anode for sodium-ion batteries (SIBs). As a cathode, the NVP@C15 electrode delivers a high capacity of 116.9 rnAh g(-1) at a rate of 1 C, which is close to its theoretical capacity. Even at a high rate of 20C, the NVP@C15 electrode exhibits an initial reversible capacity of 99.2 mAh g(-1) and a capacity retention of 77% after 6000 cycles. As an anode, the NVP@C15 delivers an initial reversible capacity of 85.8 mAh g(-1) at a rate of 1C. At higher rates of 10 and 20C, a remarkably good cydability, with a capacity retention of 76% over 4000 cycles and 62% over 5000 cycles, respectively, is achieved. Furthermore, the full cell, composed of two symmetric NVP@C15 electrodes, exhibits an initial reversible capacity of 73 mAh g(-1) at a rate of 1C. In addition, capacity retentions of 88% after 100 cycles and 61% after 500 cycles are obtained at rates of 1C and 5C, respectively.