Ti4+离子掺杂对Li3V2(PO4)3晶体结构与性能的影响

采用溶胶凝胶/碳热还原法合成了锂离子电池正极材料Li3V2(PO4)3及其掺Ti化合物Li3-2x(V1-xTix)2-(PO4)3. 电化学测试结果表明, 经Ti4+离子掺杂后材料的充放电性能及循环性能明显提高. 与纯相Li3V2(PO4)3在3.58、3.67和4.08 V出现三个平台相比, 掺杂后材料的前两个平台发生简并且平台趋于模糊的倾斜状态. 这种趋势随掺杂量的增大而增强. 差热分析(DTA)表明掺杂生成了稳定的酌相产物. 采用X射线衍射和Rietveld方法表征了化合物的晶体结构, 结果表明, 三个不同位置Li的不完全占据导致晶体中产生阳离子空穴, 使材料在常温下的离子电导率提高了3个数量级. 锂离子混排提高了样品的电导率和充放电比容量.

Effect of Doping Ti4+ on the Structure and Performances of Li3V2(PO4)3

Lithium-ion battery cathode material Li3-2x(V1-xTix)2(PO4)3 was synthesized using sol-gel/carbothermal reduction method. Electrochemical properties of substituted samples were investigated, which showed the enhancement of discharge capacity and the cycle performance by the substitution of Ti4+. The pure material of Li3V2 (PO4)3 presented three plateaus around 3.58, 3.67, and 4.08 V, but the first two plateaus slightly sloping in the substituted samples and the boundary gradually became ambiguous with the increase in the substitution ratio. The differential thermal analysis (DTA) indicated that a stabilized γ -phase product was obtained. The crystal structure was characterized by the X-ray diffraction and the Rietveld method. The results showed that all the lithium sites were partially occupied, which introduced additional vacancies into the lithium sites. The ionic conductivity of doped material was increased to three orders of magnitudes. The disorder of lithium ion would correspond to the enhancement of the conductivity and
specific capacity.