Mg-doped Li-rich vanadium phosphate Li9V3(P2O7)3(PO4)2 as cathode for lithium-ion batteries: electrochemical performance and lithium storage mechanism

作者：Yao, Heng; Chen, Da; Zhang, Jun; Duan, He; Chen, Ming; Zhou, Zhiyong; Zhao, Yanming; Kuang, Quan; Fan, Qinghua; Dong, Youzhong^*

来源：JOURNAL OF SOLID STATE ELECTROCHEMISTRY, 2021, 25(8-9): 2267-2277.

DOI：10.1007/s10008-021-04995-x

• Lithium-ion batteries
• Cathode material
• Mg ion doping
• Electrochemical performance

Considering the poor electronic conductivity of the pure Li9V3(P2O7)(3)(PO4)(2), we have successfully synthesized a series of Li9-xMgxV3(P2O7)(3)(PO4)(2) solid solution by aliovalent metal Mg ion doping on Li site. Due to the introduction of extra electrons caused by partially substituting Li+ ions by Mg2+, the electronic conductivity of the Mg-doped Li9V3(P2O7)(3)(PO4)(2) sample was improved from 3.20x10(-7) (for pure sample) to 8.85x10(-6) S cm(-1) (for Mg-doped sample). However, the inactive Mg2+ occupied the Li+ site often prevent the diffusion of the lithium ions in the electrode material and excessive Mg doping will obviously deteriorate the electrochemical performance of the electrode material. Considering the combined effect of the electronic conductivity and the lithium-ion diffusion coefficient for the excellent electrochemical performance, the optimal Mg-doping amount is x = 0.01 in our experiment. Compared with the pure sample, the Li9-xMgxV3(P2O7)(3)(PO4)(2) (x = 0.01) sample exhibited a significantly increased specific capacity at all density rates and the capacity retention, especially at high rates, almost keep 100%. In addition, using the in-situ X-ray diffraction (XRD) method, we explored the reaction mechanism of the Li9V3(P2O7)(3)(PO4)(2) electrode material and observed the existence and reversibility of the new phase during charge/discharge process.

• 单位
  广东工业大学