Photo‐Thermal Mediated Li‐ion Transport for Solid‐State Lithium Metal Batteries

Abstract The development of lithium‐based solid‐state batteries (SSBs) has to date been hindered by the limited ionic conductivity of solid polymer electrolytes (SPEs), where nonsolvated Li‐ions are difficult to migrate in a polymer framework at room temperature. Despite the improved cationic migration by traditional heating systems, they are far from practical applications of SSBs. Here, an innovative strategy of light‐mediated energy conversion is reported to build photothermal‐based SPEs (PT‐SPEs). The results suggest that the nanostructured photothermal materials acting as a powerful light‐to‐heat converter enable heating within a submicron space, leading to a decreased Li⁺ migration barrier and a stronger solid electrolyte interface. Via in situ X‐ray diffraction analysis and molecular dynamics simulation, it is shown that the generated heating effectively triggers the structural transition of SPEs from a highly crystalline to an amorphous state, that helps mediate lithium‐ion transport. Using the assembled SSBs for exemplification, PT‐SPEs function as efficient ion‐transport media, providing outstanding capacity retention (96% after 150 cycles) and a stable charge/discharge capacity (140 mA g⁻¹ at 1.0 C). Overall, the work provides a comprehensive picture of the Li‐ion transport in solid polymer electrolytes and suggests that free volume may be critical to achieving high‐performance solid‐state batteries.