Tuning Na3Hf2Si2PO12 electrolyte surfaces by metal coating for high-rate and long cycle life solid-state sodium ion batteries

Abstract

Solid-state sodium ion batteries have attracted wide attention due to their high energy density, low cost and high security. However, the poor contact and high interfacial resistance between sodium and the electrolyte seriously hindered their large-scale application. In this work, the surface of the Na₃Hf₂Si₂PO₁₂ (NHSP) electrolyte with a NASICON structure was regulated by various metal claddings, and the underlying mechanisms were investigated. We found that the interfacial reaction has an important effect on the wettability of the interface. The stronger the interfacial reaction, the better the interfacial wettability. Based on the above-mentioned theory, we chose lead as the interface modification element. Owing to the formed interphase between sodium and lead with good wettability and fast charge conductivity, the lead decorated NHSP exhibits superior interface stability to others. Consequently, the battery with the lead decorated NHSP can cycle stably for more than 2400 hours at room temperature and the critical current density can reach 2.5 mA cm⁻² at 60 °C. This work represents an effective avenue to address the interfacial challenges between sodium and solid electrolyte and providing opportunities to use in solid-state sodium ion battery in the future.