锂离子电池Li_2Fe_(1-x)V_xSiO_4/C复合正极材料的合成、结构形貌和电化学性能

Synthesis,structure,morphology and electrochemical performances of Li_2Fe_(1-x)V_xSiO_4/C complex cathode materials for lithium ion batteries

采用液相预处理和固相反应相结合的方法合成了聚阴离子型锂离子电池Li2Fe1-xVxSiO4/C(x=0,0.1,0.3,0.5)复合正极材料,采用XRD、SEM、EDX和电化学测试对材料进行了表征,研究了钒掺杂对材料结构、形貌和电化学性能的影响。结果表明所有样品均为正交晶系,属P21mn空间群,钒掺杂量x=0.1时样品晶格常数发生明显变化,晶胞呈c轴方向拉长的立方体,导致了材料的比容量和循环性能下降;所有样品均为纳米至亚微米尺寸颗粒,且随钒掺杂量的增加而增大,但x=0.5时样品的电化学性能最优。在常温和0.2C倍率下初始放电容量为124.3mAh/g,循环10次后容量无衰减,可逆放电容量仍高达126.2mAh/g,显示了良好的循环性能和应用前景。

Li2Fe1-xVxSiO4/C（x=0,0.1,0.3,0.5）complex cathode materials have been synthesized via a method which was combined by liquid pretreatment and solid state reaction and characterized by XRD,SEM,EDX and electrochemical tests.The effects of vanadium substitution on the structure,morphology and electrochemical performances of Li2Fe1-xVxSiO4/C were investigated.The results demonstrated that the prepared Li2Fe1-xVxSiO4/C samples can all be indexed on the basis of the orthorhombic unit cell in space group P21mn,and their lattice parameters are not similar as x=0.1,the cell is like a stretched cubic along C-axis,which leads to decrease of capacity and cycle performance,and nano to submicro-sized particles can be observed in the samples.The sample which x=0.5shows better electrochemical performance than other samples,the initial discharge capacity is 124.3mAh/g,and 126.2mAh/g remained after 10cycles at 0.2 Crate and ambient temperature.It displays excellent cyclic properties and application prospects.