Electrode-Electrolyte Interface Regulation Enables Large-Capacity Gel-State Na Metal Batteries with Appealing Cycling Stability

Abstract

Gel-state Na metal batteries (NMBs) are promising candidates for the large-scale energy storage due to the merits of low cost, abundant sodium resources, and high energy density. However, the long-term lifespan and safety of NMBs with large capacity are limited by unstable electrode-electrolyte interface. Herein, the electrode-electrolyte interfaces are regulated by the mechanically robust GPE coupled with the artificial NaBr/Na_xSn_y layer on Na anode, enabling the symmetric cells with a long-term cycling lifespan of over 2500 h at 0.5 mA cm⁻², along with an ultralong cycle life of ca. 4700 h at 0.2 mA cm⁻² under −20 °C. With an area capacity of ca. 0.9 mAh cm⁻² based on Na₃V₂(PO₄)₃, the SnBr₂-Na|GPE|Na₃V₂(PO₄)₃ full cells exhibit a capacity retention of 96.6% after 1100 cycles, resulting from high ionic conductivity (3.7 mS cm⁻¹) of GPE and stable inorganic NaBr/Na_xSn_y layer on Na surface. This work provides a new insight for the development of NMBs with high safety and large capacity.