Maximizing ionic transport of Li1+xAlxTi2-xP3O12 electrolytes for all-solid-state lithium-ion storage: A theoretical study

Tiantian Wang^1,2,3，Jun Mei^4,5，Jianjun Liu^1,3，Ting Liao^2,3

1. State Key Laboratory of High Performance Ceramics and Superfine Microstructure, Shanghai Institute of Ceramics, Chinese Academy of Sciences2. School of Mechanical, Medical and Process Engineering, Queensland University of Technology3. Centre of Materials Science and Optoelectronics Engineering, University of Chinese Academy of Sciences4. School of Chemistry and Physics, Queensland University of Technology5. Centre for Materials Science, Queensland University of Technology

摘 要：The concept of all-solid-state batteries provides an efficient solution towards highly safe and long-life energy storage,while the electrolyte-related challenges impede their practical application.Li_1+xAl_xTi_2-xP₃O₁₂（0≤x≤1） with superior Li ionic conductivity holds the promise as an ideal solidstate electrolyte.The intrinsic mechanism to reach the most optimum ionic conductivity in Al-doped Li_1+xAl_xTi_2-xP₃O₁₂,however,is unclear to date.Herein,this work intends to provide an atomic scale study on the Li-ion transport in Li_1+xAl_xTi_2-xP₃O₁₂electrolyte to rationalize how Al-dopant initiates interstitial Li activity and facilitate their easy mobility combining Density Functional Theory （DFT） and ab initio Molecular dynamics （AIMD） simulations.It is discovered that the interstitial Li ions introduced by Al dopants can effectively activate the neighboring occupied intrinsic Li-ions to induce a long-range mobility in the lattice and the maximum Li ionic conductivity is achieved at 0.50 Al doping concentration.The Li-ion migration paths in Li_1+xAl_xTi_2-xP₃O₁₂have investigated as the degree of distortion of[PO4]tetrahedra and[TiO6]octahedra resulted by different Al doping concentrations.The asymmetry of the surrounding distorted[PO4]and[TiO6]polyhedrons play a critical role in reducing the migration barrier of Li ions in Li_1+xAl_xTi_2-xP₃O₁₂.The flexible[Ti O6]polyhedrons with a capacity to accommodate the structural distortion govern the Li ionic conductivity in Li_1+xAl_xTi_2-xP₃O₁₂.This work rationalizes the mechanism for the most optimum Li ionic conductivity in Al-doped Li Ti₂P₃O₁₂electrolyte and,more importantly,paves a road for exploring novel all-solid-state lithium battery electrolytes.

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