화학공학소재연구정보센터
International Journal of Energy Research, Vol.44, No.8, 6608-6622, 2020
Ultra-long cycle life and high rate performance subglobose Na3V2(PO4)(2)F-3@C cathode and its regulation
A nitrogen-doped carbon coated subglobose Na3V2(PO4)(2)F-3@C (NVPF) cathode for sodium-ion batteries was synthesized by using hexadecyl trimethyl ammonium bromide (CTAB) as soft template and polyvinylidene fluoride (PVDF) as carbon source. CTAB plays a significant role on the formation of sphere micelles. Precursor ions are self-assembled on the surface at appropriate concentration and its mechanism is investigated in subglobose NVPF@C-4. CTAB also increases the conductivity of carbon layer as -(CH3)(3)N+ in CTAB is combined with residual carbon from PVDF to form partially N-doped carbon. Meanwhile, the carbon source PVDF contributes to prevent the generation of impurity Na3V2(PO4)(3) by compensating the evaporative fluorine. Generally, CTAB and PVDF play multifunctional roles in regulating Na3V2(PO4)(2)F-3@C cathode with well-developed crystallite, high rate performance, good conductivity, and ultra-long cycle life. The specific capacity of NVPF@C-4 cathode at 0.1 C and 10 C is as high as 121.5 mAh center dot g(-1) and 99.2 mAh center dot g(-1) with high capacity retention of 90.1% even after 1000 cycles at 10 C. The excellent rate performance is also attributed to the high diffusion coefficient of Na+ and high exchange current according to the kinetic analysis. The enhanced electrochemical performances reveal the special regulation in this paper is feasible to obtain excellent structural stability of NVPF materials.