Nitride-engineered interfaces enabling long-cycle solid-state lithium metal batteries

Abstract

Solid electrolyte Li_1.3Al_0.3Ti_1.7(PO₄)₃ (LATP) has attracted significant attention due to its high ionic conductivity, good air stability, and low cost. However, the practical application of LATP is limited by its instability with Li metal, poor interfacial contact, and sluggish ion transport. Herein, a multifunctional layer composed of LiN_xO_y and LiGa is designed via an in situ conversion reaction between Li metal and Ga(NO₃)₃. LiN_xO_y (LiNO₃ phase) with low interface energy and high affinity can improve interfacial contact, while LiN_xO_y (Li₃N phase) can provide rapid Li⁺ transport with its low migration barrier. The insulating LiN_xO_y prevents side reactions, and the conductive LiGa alloy homogenizes electric fields, enabling uniform Li deposition. Therefore, the preference layer ensures stable and tight contact at the interface throughout the cycle. The initial interfacial resistance of the symmetric battery is reduced from 1677.2 to 152.2 Ω cm⁻², and the critical current density is increased to 1.6 mA cm⁻². Long-term stable cycling at 0.1 mA cm⁻²/0.1 mA h cm⁻² for 3000 h and 0.2 mA cm⁻²/0.2 mA h cm⁻² for 2500 h can be achieved. Full cells with LiFePO₄ retain 89.3% capacity after 300 cycles at 0.5C, while Li₁.₂Mn₀.₆Ni₀.₂O₂-based cells also exhibit high capacity and cycling stability.