From Li7La3Zr2O12 to Li4La4Zr2Cl24: Rapid three-dimensional transport of ions in halide solid electrolytes

Abstract

Inorganic solid electrolyte materials have emerged as a central focus in battery research, with halide solid electrolytes particularly favored due to their exceptional overall performance. However, the current preparation methods for halides often require extended time, and most raw materials, with the exception of Li₂ZrCl₆, tend to be costly. In this context, we focused on the oxide Li₇La₃Zr₂O₁₂ and successfully synthesized Li₇La₃Zr₂Cl₂₄ by substituting all O with Cl. Taking advantage of the unique properties of the LaCl₃ lattice, we adjusted the ratios of La and Zr, and finally reported a novel halide, Li₄La₄Zr₂Cl₂₄, which exhibits a balanced Li and vacancies, as well as a three-dimensional interconnecting network for Li⁺ conduction. It is important that the synthesis process for this new material is relatively straightforward, requiring only 8 h of ball milling to achieve optimal ionic conductivity of 0.21 mS cm⁻¹. This method has the potential to lower production costs and facilitate the development of halide series materials. At a current density of 1 C, the capacity retention rate of the all-solid-state battery assembled from this material is 73.66 % after 200 cycles. Additionally, the battery demonstrates stable cycling performance within a high voltage range of 2.2 to 4.5 V.