(中南大学 材料科学与工程学院,长沙 410083)
摘 要: 用乙炔碳作为碳源,采用机械活化辅助碳热还原两步法合成xLi3V2(PO4)3·LiVPO4F/C复合正极材料。采用XRD、SEM、TEM等技术对样品的晶体结构和微观形貌进行了表征,采用循环伏安法和恒流充放电等测试方法对合成样品的电化学性能进行分析研究。结果表明:xLi3V2(PO4)3·LiVPO4F/C复合正极材料兼备了Li3V2(PO4)3的循环稳定性好、倍率性能佳的优点和LiVPO4F能量密度高的优势,此外还弥补了Li3V2(PO4)3在3~4.7 V电压范围充放电时放电电压平台缺失的缺陷。该材料在3~4.7 V之间的循环稳定性较好,在1C倍率下最高放电比容量为119.7 mA?h/g,循环300圈后为97.5 mA?h/g。其倍率性能较好,在0.1C倍率下充放电可获得高达152 mA?h/g的放电比容量,倍率升高到8C时仍能保持100 mA?h/g的放电比容量。
关键字: 锂离子电池;正极材料;碳热还原法;xLi3V2(PO4)3·LiVPO4F/C
(School of Materials Science and Engineering, Central South University, Changsha 410083, China)
Abstract:A two-step mechanical activation and carbon thermal reduction method was used to synthesize xLi3V2(PO4)3·LiVPO4F/C composite cathode material, using actylene black as carbon source. The crystal structure and morphology were characterized by using XRD, SEM, and TEM techniques. In addition, the electrochemical performances of the prepared materials were characterized by cyclic voltammetry (CV) and galvanostatic charge/discharge tests. The results show that xLi3V2(PO4)3LiVPO4F/C composite cathode material has the advantages of good cyclic stability of Li3V2(PO4)3 and the high energy density of LiVPO4F. Meanwhile, it makes up for the shortcoming of the disappeared voltage platform of Li3V2(PO4)3 cathode within 3-4.7 V. The cyclic stability of the composite is good. The maximum value of discharge specific capacity is 119.7 mA?h/g under the rate of 1C which can retain 97.5 mA?h/g after 300 cycles. The rate performance is excellent. The composite electrode delivers a high capacity of 152 mA?h/g at 0.1C. When the current density increases to 8C, the electrode can still deliver a specific discharge capacity of 100 mA?h/g.
Key words: lithium-ion battery; cathode material; carbothermal reduction method; xLi3V2(PO4)3·LiVPO4F/C