Insight into fast ion migration kinetics of a new hybrid single Li-ion conductor based on aluminate complexes for solid-state Li-ion batteries

Abstract

A novel hybrid single Li-ion conductor (SLIC) for a Li-ion solid electrolyte was prepared by mixing aluminate complexes–polyethylene glycol (LiAl–PEG) and polyethylene oxide (PEO) for solid-state Li-ion batteries. The LiAl–PEG/PEO blend possesses high thermal stability and electrochemical stability with an oxidation decomposition voltage up to 4.8 V. Notably, this hybrid SLIC exhibits not only excellent Li-ion migration kinetics, but also good ionic conductivity as high as 4.0 × 10⁻⁵ and 2.6 × 10⁻⁴ S cm⁻¹ at 30 and 100 °C, respectively, which is much higher than previously reported SLICs. Importantly, by the combination of molecular dynamics simulations and experiment measurements, the mechanisms of Li-ion migration across the SLIC (LiAl–PEG), the salt-in-polymer (LiClO₄/PEO) and the optimized SLIC (LiAl–PEG/PEO) were systematically investigated for the first time. The new hopping transport mechanism was verified for the SLIC system at the nanoscale. As for the hybrid SLIC, PEO chains enhance the segmental mobility of the ether-chains bonded with Al atoms, improve the ionicity, and provide extra ionic paths for Li transfer, resulting in the optimized Li-ion migration kinetics of LiAl–PEG/PEO.