Engineering of Sn and Pre‐Lithiated Sn as Negative Electrode Materials Coupled to Garnet Ta‐LLZO Solid Electrolyte for All‐Solid‐State Li Batteries

Abstract All‐solid‐state batteries using garnet‐type solid electrolyte are considered as a promising solution for the next generation energy storage systems but to date they still suffer from low ionic conductivity compared to organic liquid electrolytes and poor interfacial contact between the electroactive materials and the electrolyte. Here we propose several proof‐of‐concept level strategies to enhance the interfacial contact between the electroactive material Sn and the solid electrolyte Ta‐LLZO doped (hereafter called LLZTa) to enable proper electrochemical cycling. First, we demonstrate that the conventional slurry‐based technique is not appropriate to ensure cycling of a Sn based electrode in all‐solid‐state batteries due to poor interfacial contact. Then, we demonstrate (proof‐of‐concept) that thin films deposition is a more suitable approach to ensure electrochemical activity but the large volume changes of Sn during alloying process is leading to a rapid cell failure. This last challenge was overcome by the use of a chemically pre‐lithiated Sn thin film which then delivers, after an activation process, specific charge close to the theoretical one (900 mAh/g) at C/30 rate and T=80 °C.