Stabilizing the Cathode/Electrolyte Interface Using a Dry-Processed Lithium Titanate Coating for All-Solid-State Batteries
Rajendra Singh Negi, Philip Minnmann, Ruijun Pan, Shamail Ahmed, Marcel J. Herzog, Kerstin Volz, Ryo Takata, Franz Schmidt, Jürgen Janek, Matthias T. Elm
Abstract
Considering the high theoretical energy density and improved safety, thiophosphate-based all-solid-state batteries (ASSBs) have become one of the most promising candidates for next-generation energy storage systems. However, the intrinsic electrochemical instability of thiophosphate-based solid electrolytes in contact with oxide-based cathodes results in rapid capacity fading and has driven the need of protective cathode coatings. In this work, for the first time, a fumed lithium titanate (LTO) powder-based coating has been applied to Ni-rich oxide-based cathode active material (CAM) using a newly developed dry-coating process. The LTO cathode coating has been tested in thiophosphate-based ASSBs. It exhibits a significantly improved C-rate performance along with superior long-term cycling stability. The improved electrochemical performance is attributed to a reduced interfacial resistance between coated cathode and solid electrolyte as deduced from in-depth electrochemical impedance spectroscopy analysis. These results open up a new, facile dry-coating route to fabricate effective protective CAM coatings to enable long-life ASSBs. This nondestructive coating process with no post-heat-treatment approach is expected to simplify the coating process for a wide range of coatings and cathode materials, resulting in much improved cathode/electrolyte interfacial stability and electrochemical performance of ASSBs.