Dual Doping: An Effective Method to Enhance the Electrochemical Properties of Li10GeP2S12-Based Solid Electrolytes

Multiple doping is widely used to improve the performance of a material, including its electrical transport, mechanical, and photovoltaic properties. In this paper, Sn-Se dual-doped Li10GeP2S12 (LGPS, thio-LISICON II analogue) electrolytes were synthesized via ball milling and sintering and compared with those Sn or Se single-doped. Successful Sn and/or Se substitution expanded the unit cell and formed SnSe44- units, which were verified by X-ray powder diffraction, energy-dispersive X-ray spectroscopy, and Raman spectroscopy. In contrast to the limited benefits of Se single doping and the negative effects of Sn single doping, Sn-Se dual doping demonstrated up to 53% enhancement in ionic conductivity. More importantly, Sn-Se dual-doped LGPS showed an extremely low activation energy of 16 kJ/mol, which is one of the lowest known values for lithium ion conductors; as well as one of the widest electrochemical windows of 8 V. Sn-Se dual-doped LGPS is a promising electrolyte for advanced all-solid-state batteries.