Guidelines for designing high-deformability materials for all-solid-state lithium-ion batteries

Abstract

Weak contact and high resistance between ceramic powder particles limit their applicability in all-solid-state Li-ion batteries, particularly those assembled via powder moulding. To overcome these limitations, sulfide and chloride materials have been extensively studied because their deformability and Li diffusivity are typically greater than those of oxide materials. However, not all sulfide and chloride materials exhibit the high Li diffusivity and deformability necessary for all-solid-state batteries. This study focused on determining the suitability of the shear modulus as an index of deformability, in addition to a Li diffusivity index. These indices were calculated for all the Li-containing chloride compounds in a structural database. Six chloride materials (Li₂CoCl₄, Li₂CrCl₄, Li₁₀Mg₇Cl₂₄, Li₄Mn₃Cl₁₀, Li₂FeCl₄, and LiAlCl₄) with different shear moduli were experimentally evaluated. The Li diffusion coefficients of most of these chlorides were found to be higher than those of the oxide and sulfide electrode materials typically employed in Li-ion batteries. Moreover, deformability, which for compressed pellets includes contributions from the relative density and grain boundary resistance, was observed to vary among these chlorides. The shear modulus, as determined by first-principles calculations, was confirmed to be a suitable screening index for deformability. The utilisation of the design guidelines for deformability is expected to facilitate significant advancements in all-solid-state battery material research.