A Series of Ternary Metal Chloride Superionic Conductors for High-Performance All-Solid-State Lithium Batteries

Understanding the relationship between structure, ionic conductivity, and synthesis is the key to the development of superionic conductors. Here, a series of Li3-3xM1+xCl6 (-0.14 < x <= 0.5, M = Tb, Dy, Ho, Y, Er, Tm) solid electrolytes with orthorhombic and trigonal structures are reported. The orthorhombic phase of Li-M-Cl shows an approximately one order of magnitude increase in ionic conductivities when compared to their trigonal phase. Using the Li-Ho-Cl components as an example, their structures, phase transition, ionic conductivity, and electrochemical stability are studied. Molecular dynamics simulations reveal the facile diffusion in the z-direction in the orthorhombic structure, rationalizing the improved ionic conductivities. All-solid-state batteries of NMC811/Li2.73Ho1.09Cl6/In demonstrate excellent electrochemical performance at both 25 and -10 degrees C. As relevant to the vast number of isostructural halide electrolytes, the present structure control strategy guides the design of halide superionic conductors.

Automated summary

Understanding the relationship between structure, ionic conductivity, and synthesis is crucial for developing superionic conductors. This study reports a series of Li3-3xM1+xCl6 solid electrolytes with orthorhombic and trigonal structures. The orthorhombic phase shows significantly higher ionic conductivity compared to the trigonal phase. Molecular dynamics simulations explain the enhanced ionic conductivity by the facile diffusion in the z-direction in the orthorhombic structure. All-solid-state batteries based on NMC811/Li2.73Ho1.09Cl6/In exhibit excellent electrochemical performance. The findings provide guidance for the design of halide superionic conductors.