Synergy of non-lithium cation doping and the lithium concentration affecting lithium ion transport in solid electrolytes

Abstract

The doping of non-lithium cations has a very significant effect on the electrochemical performance of inorganic solid electrolytes. In this work, the effect of non-lithium cations on the ionic conductivity of LISICON-type solid electrolytes at different lithium-ion concentrations is investigated based on first principles calculations. The results show that the doping of non-lithium cations has different effects on Li⁺ diffusion at different lithium-ion concentrations. This might be due to the fact that the doping of non-lithium cations at different lithium-ion concentrations results in different changes in the energy landscape of lithium ions. Therefore, we propose that large non-lithium cation doping can increase lithium-ion conductivity at low lithium-ion concentrations while the doping of non-lithium cations with a small radius can improve the lithium-ion conductivity at high lithium-ion concentrations. Besides, all these solid electrolytes are proved to be poor electronic conductors with a wide bandgap. Finally, from the thermodynamic point of view, these solid electrolytes show good thermal stability and match well with LiNiO₂. These superior properties indicate that these materials are very promising solid electrolytes for lithium-ion batteries.