Nanocomposite LiFePO_4·Li_3V_2(PO_4)_3/C synthesized by freeze-drying assisted sol-gel method and its magnetic and electrochemical properties  

冷冻干燥辅助溶胶-凝胶法制备纳米复合材料LiFePO_4·Li_3V_2(PO_4)_3/C及其磁学和电化学性能的研究（英文）

作　　者：刘丽英 肖文学 郭剑峰 崔艳艳 柯曦 蔡伟通 刘军 陈易明 施志聪 侴术雷 

机构地区：[1]School of Materials and Energy, Guangdong University of Technology [2]Institute for Superconducting & Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong

出　　处：《Science China Materials》2018年第1期39-47,共9页中国科学（材料科学（英文版）

基　　金：supported by the National Natural Science Foundation of China (21673051);Guangdong Province Science & Technology Bureau (2014A010106029, 2014B010106005 and 2016A010104015);Guangzhou Science & Innovative Committee (201604030037);the Youth Foundation of Guangdong University of Technology (252151038);the link project of the National Natural Science Foundation of China and Guangdong Province (U1401246);the Science and Technology Program of Guangzhou City of China (201508030018)

摘　　要：Nano-sized LiFePO_4·Li_3V_2（PO_4）_3/C was synthesized via a sol-gel route combining with freeze-drying. X-ray diffraction results show that this composite mainly consists of olivine Li Fe PO4 and monoclinic Li3 V2（PO4）3 phases with small amounts of V-doped LiFePO_4 and Fe-doped Li_3V_2（PO_4）_3. The magnetic properties of LiFePO_4·Li_3V_2（PO_4）_3/C are significantly different from LiFePO_4/C. Trace quantities of ferromagnetic impurities and Fe_2P are verified in LiFePO_4/C and LiFePO_4·Li_3V_2（PO_4）_3/C by magnetic tests, respectively. LiFePO_4·Li_3 V_2（PO_4）_3/C possesses relatively better rate capacities and cyclic stabilities, especially at high charge-discharge rates.The initial discharge capacities are 136.4 and 130.0 mA h g^（-1）,and the capacity retentions are more than 98% after 100 cycles at 2C and 5C, respectively, remarkably better than those of LiFePO_4/C. The excellent electrochemical performances are ascribed to the mutual doping of V^（3＋）and Fe^（2＋）, complementary advantages of LiFePO_4 and Li_3V_2（PO_4）_3 phases, the residual high-ordered carbon and Fe_2P with outstanding electric conductivity in the nanocomposite.本文采用冷冻干燥与溶胶-凝胶相结合的方法制备了纳米复合材料LiFePO_4·Li_3V_2(PO_4)_3/C.XRD结果表明该复合材料主要由橄榄石型LiFePO_4和单斜晶系Li_3V_2(PO_4)_3相组成,同时包含少量的V掺杂LiFePO_4和Fe掺杂Li_3V_2(PO_4)_3.磁学测试结果表明,LiFePO_4·Li_3V_2(PO_4)_3/C的磁学特性显著区别于LiFePO_4/C,并且痕量的铁磁性杂质和Fe_2P杂质分别存在于LiFePO_4/C和LiFePO_4·Li_3V_2(PO_4)_3/C中.LiFePO_4·Li_3V_2(PO_4)_3/C具有相对优良的循环稳定性,尤其是在大倍率条件下.在2 C和5 C时,首次放电容量分别为136.4和130.0 mA h g^(-1),100周循环后保持率在98%以上,优于LiFePO_4/C的电化学性能.LiFePO_4·Li_3V_2(PO_4)_3/C电化学性能的改善归因于V^(3+)和Fe^(2+)的相互掺杂,LiFePO_4和Li_3V_2(PO_4)_3相的优势互补,残留的高有序碳以及导电性优异的Fe_2P.

关 键 词：lithium ion battery cathode material lithium iron phosphate lithium vanadium phosphate magnetic property 

分 类 号：TB33[一般工业技术—材料科学与工程]