两步固相碳包覆法合成Li3V2(PO4)3/C正极材料及其性能研究

摘要

以VPO4/C为中间体,相继以乙炔黑及葡萄糖作为碳源,通过两步固相碳包覆法制备了纯相单斜晶系的Li3V2(PO4)3/C复合材料.该方法首先通过制备纳米级的 VPO4/C 中间体,为后续制备 Li3V2(PO4)3/C 提高反应活性,降低热处理温度,其中碳源不仅起到还原剂、导电剂的作用,还能细化晶粒,且两步法包碳使得材料颗粒表面的碳层更均匀,从而改善材料的综合电化学性能.最终在750 ℃下煅烧12 h 得到颗粒细小且分布均匀的Li3V2(PO4)3/C样品,在电压区间3.0~4.5 V 内,该材料在0.1,1和2 C 倍率下的首次放电比容量分别为141.5,119.8和109.4 mAh/g,在0.1 C倍率下循环50次后的容量保持率高达97.7%.%In this study,the pure monoclinic Li3V2(PO4)3/C composite was prepared by a two-step solid-phase carbon coating method with VPO4/C as an intermediate and acetylene black and glucose as carbon sources.The nano-sized VPO4/C intermediate was synthesized to induce rapid reaction of Li3V2(PO4)3/C preparation,which would decrease the treatment temperature.The carbon sources as reductant and conductive agent can also reduce the particle size.Moreover,the carbon layer out of the Li3V2(PO4)3 grain is more uniform by two-step solid-phase method,resulting in the enhancement of the Li3V2(PO4)3 electrochemical performance.The Li3V2 (PO4)3/C synthesized at 750 ℃ for 12 h has evenly distributed,fine particles.The initial specific discharge ca-pacities at 0.1,1 and 2 C are 141.5,119.8 and 109.4 mAh/g,respectively,in the potential range of 3.0-4.5 V, and the capacity retention after 50 cycles at 0.1 C rate still remains 97.7%.