Improving Na/Na₃Zr₂Si₂PO₁₂ Interface via SnO_x/Sn Film for High-Performance Solid-State Sodium Metal Batteries

Sodium (Na) metal batteries have attracted much attention due to their rich resources, low cost, and high energy density. As a promising solid electrolyte, Na₃Zr₂Si₂PO₁₂ (NZSP) is expected to be used in solid-state Na metal batteries addressing the safety concerns. However, due to the poor contact between NZSP and the Na metal, the interfacial resistance is too large to gain proper performance for practical solid-state batteries (SSBs) application. Here, a SnO_x/Sn film is successfully introduced to improve the interface between Na and NZSP for enhancing the electrochemical performance of SSBs. As a result, the Na/NZSP interfacial resistance is dramatically reduced from 581 to 3 Ω cm². The modified Na||Na symmetric cell keeps cycling over 1500 h with an overpotential of 40 mV at 0.1 mA cm^–2 at room temperature. Even at current densities of 0.3 and 0.5 mA cm^–2, the cell still maintains an excellent cyclability. When coupled with NaTi₂(PO₄)₃ and a Na₃V₂(PO₄)₃ cathode, the full-cell demonstrates a good performance at 0.2 C and 1 C, respectively. The present work provides an effective way to solve the interface issue of SSBs.