Synthesis And Electrochemical Performance Of Li₁₀GeP₂S₁₂-based Solid Electrolyte

Li₁₀GeP₂S₁₂（LGPS） has a high lithium ionic conductivity（1.2×10-2 S/cm） at room temperature. However, the electrochemical stability of LGPS is poor. In this paper, we aim to seek a suitable doping element to improve the electrochemical stability of LGPS. The first-principle calculations based on the density functional theory have reveaed that not only the Coulomb interaction but also the Van Der Walls account for the electrochemical stability of LGPS. If the lithium ions in the frame work are partially substituted by divalent/trivalent metal cations, the coulomb repulsion between S2- will be screened and the total energy of LGPS system will be reduced, thus the electrochemical stability will be improved. In this paper BaS, Al2S3, CaS were chosen as the sources for dopant and the Ba, Al, Ca doped LGPS, i.e. materials Li10-2xBaxGeP2S12（0.1≤x≤0.5）, Li10-3xAlxGeP2S12（0.02≤x≤0.3）, and Li10-2xCaxGeP2S12（0.1≤x≤0.5） were synthesized by solid state reaction. The effects of different doping elements on the structure, ionic conductivity, activation energy and electrochemical stability of LGPS doped with different elements are systematically studied. The influence of the doping elements with different valence and ionic radius on the ionic conductivity and electrochemical stability of LGPS is further investigated.