Effect of adding solid electrolyte to tin-based glass-ceramics anode for all-solid-state sodium-ion batteries by laser-induced local heating

In oxide-based all-solid-state sodium-ion batteries, glass anodes containing a high concentration of tin oxide doped with iron ions strongly absorb near-infrared laser light (λ ≈ 1 µm), enabling localized melting and solidification through position-selective laser heating. To enhance ionic transport within the anode layer and to clarify the relationship between laser irradiation conditions, resulting microstructure, and electrochemical performance, 30 wt% of the sodium-ion conductor Na3Zr2Si2PO12 (NZSP) was incorporated into the glass anode as an active component. The laser-processed anode layer exhibited a dense, void-free microstructure and strong interfacial bonding with the solid electrolyte substrate. Owing to the high optical absorption of the glass matrix, the temperature at the laser focal point rapidly increased to approximately 1700°C, which was sufficient to soften the glass within a short irradiation time. In contrast, NZSP, which is optically transparent at the laser wavelength, retained its crystalline structure during the rapid melting and quenching process, indicating minimal thermal degradation. NZSP incorporation significantly improved ionic conductivity in the anode layer, increasing the initial charge and discharge capacities by 5.3 and 7.2 times, respectively, and enhancing capacity after 100th cycles.