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Density Functional Theory and Electrochemistry Studies on LiFexMn1-xPO4 Solid Solutions
Kang-ping Wang1, Tao-tao Shen2, Dong-ming Chen*1, Wen-lou Wang*1,2,3,4
1.Department of Chemical Physics, University of Science and Technology of China, Hefei 230026, China;2.Nano Science and Technology Institute, University of Science and Technology of China, Suzhou 215123, China;3.Collaborative Innovation Center of Suzhou Nano Science and Technology, Suzhou 215123, China;4.National Synchrotron Radiation Laboratory, University of Science and Technology of China, Hefei 230029, China
Abstract:
The thermodynamic stability and lithiated/delithiated potentials of LiFexMnfeng1-xPO4 were studied with density functional theorical calculations. The results show that the formation free energy of the LiFexMn1-xPO4 solid solution is slightly higher than that of the phase-separated mixture of LiFePO4 and LiMnPO4, and the two forms may co-exist in the actual LiFexMn1-xPO4 materials. The calculation manifests that the lithiated/delithiated potentials of LiFexMn1-xPO4 solid solutions vary via the Mn/Fe ratio and the spatial arrangements of the transition metal ions, and the result is used to explain the shape of capacity-voltage curves. Experimentally, we have synthesized the LiFexMn1-xPO4 materials by solid-phase reaction method. The existence of the LiFexMn1-xPO4 solid solution is thought to be responsible for the appearance of additional capacity-voltage plateau observed in the experiment.
Key words:  LiFexMn1-xPO4, Solid solution, Solid state synthesis, Density functional theory calculation, Electrochemical performance
FundProject:
LiFexMn1-xPO4固溶体的密度泛函理论与电化学研究
王康平1, 沈桃桃2, 陈东明*1, 王文楼*1,2,3,4
1.中国科学技术大学化学物理系,合肥 230026;2.中国科学技术大学纳米科学技术学院,苏州 215123;3.苏州纳米科技协同创新中心,苏州 215123;4.中国科学技术大学国家同步辐射实验室, 合肥 230029
摘要:
本文用DFT计算方法研究了LiFexMn1-xPO4的热力学稳定性和嵌/脱锂电位. 结果表明,LiFexMn1-xPO4固溶体的自由能比相分离的LiFePO4/LiMnPO4混合物略高,这两种形式可能在实际LiFexMn1-xPO4材料中共存. 计算表明,LiFexMn1-xPO4固溶体的嵌/脱锂电位随锰/铁比以及过渡金属离子的空间排列而变化,并用计算结果解释了放电曲线的形状. 采用固相反应法合成了LiFexMn1-xPO4材料并研究了其电化学性质,实验中观察到附加的放电平台,其出现可能与LiFexMn1-xPO4固溶体的存在有关.
关键词:  LiFexMn1-xPO4,固溶体,密度泛函理论计算,固相合成,电化学性能
DOI:10.1063/1674-0068/cjcp1904071
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