A facile route to plastic inorganic electrolytes for all-solid state batteries based on molecular design

An easily synthesised Li–Al–O–Cl glassy electrolyte based on molecular design exhibits high ion conductivity, viscoplasticity and a transference number ∼1, along with exceptional anodic stability in a solid-state cell with an NMC85 cathode. Solid-state lithium batteries are on the threshold of commercialization as an alternative to liquid electrolyte batteries. Glassy or amorphous solid electrolytes could bring crucial benefits, but their lack of periodicity impedes structure-derived material design. Here, we report an approach for glassy electrolyte design based on well-defined lithium metal oxychloride linear oligomers. By packing these oligomers formed by oxygen-bridged chloroaluminates, a glassy solid model is constructed. Li ions in mixed-anion coordination with distorted polyhedra favor good lithium conductivity (1.3 mS cm −1 at 30 °C). The frustrated Li-ion geometry and non-crystallinity promote conformational dynamics of the oligomer backbone that generates mechanical plasticity. Ab initio molecular dynamics simulations depict the conformational motion that resembles that of organic molecules. Our all-solid-state battery based on this solid electrolyte shows exceptional long term electrochemical stability with a high-nickel NCM cathode. This work shows the impact of targeted structure models for rational design of glassy plastic electrolytes.