A scalable fibrous membrane reinforced solid polymer composite electrolyte for sodium metal battery

All-solid-state sodium batteries utilizing polyethylene-oxide (PEO) based solid polymer composite electrolytes (SPCEs) is promising candidates for the next-generation energy storage devices. However, the reported SPCEs still suffer from poor stability and restricted workability. Here, a PEO-based composite SPCE incorporated with Al₂O₃ nano particles as localized-crystallinity regulator and high-porosity polyimide (PI) fibrous membrane as mechanical-strength enhancer was fabricated. The tensile strength of the SPCE was significantly improved from 0.15 to 17.72 MPa, which made the SPCE's potential capability for industrially scalable fabrication. When applied in Na||Na symmetrical cells, the SPCE exhibits superior thermal stability and excellent dendrite-suppressing capability. As the consequence, the critical current density was improved from 0.06 to 0.62 mA cm^-2, and the Na||Na cells can stably cycle for 4000 h at 0.15 mA cm^-2 (60 °C) and for 1000 h at 0.2 mA cm^-2 (80 °C), respectively. Furthermore, the Na₂CO₃-NaF-Na₂O based solid electrolyte interphase was investigated, providing more insights into the NaTFSI-PEO based SPCEs. It was further validated that the designed SPCE can achieve large-scale preparation due to the excellent mechanical properties, full cells and pouch cell also presented remarkable performances and reliable safety. This work develops an effective approach to realizing the high-performance and large-scale-application all-solid-state batteries.