A composite gel polymer electrolyte for sodium metal battery at a wide temperature range

Sodium-metal batteries (SMBs) are considered a promising alternative to lithium-metal batteries due to their high-energy density, low cost, and good low-temperature performance. However, the serious side reactions and dendrites growth during the process of sodium ions deposition/stripping are the bottleneck that inhibits the further capitalization of SMBs, especially at low temperatures. Herein, a porous framework of 50 μm thickness composite gel-polymer-electrolyte (GPE) supported by polyvinylidene difluoride nanowires membrane and Na₃Zr₂Si₂PO₁₂ ceramic particles is proposed to tackle the issues. This GPE not only has high ionic conductivity but also can promote the uniform transportation of sodium ions to form a stable and dense metal-GPE interfacial layer, which can effectively inhibit the side reactions and dendrites growth in a wide temperature range. The assembled Na//GPE//Na₃V₂(PO₄)₃ full battery provides a specific capacity of 100 mAh g⁻¹ at 10 C for more than 3000 cycles calendar life at room temperature. Moreover, the full battery based on this GPE has an extraordinary performance at low temperatures, reaching a specific capacity of 93 and 61 mAh g⁻¹ at 0.5 and 1 C at −20°C, respectively. This work provides a reliable solution for low-temperature applications of high-energy density and long-cycle life SMBs.