Bifunctional 2D g-C3N4 Interfacial Layer for Stabilizing the LATP/Lithium Metal Interface in Solid-State Lithium Batteries

Abstract

NASICON-type Li1.3Al0.3Ti1.7(PO4)3 (LATP) solid-state electrolytes have attracted considerable attention because of their relatively high ionic conductivity and excellent ambient stability. However, their practical application is hindered by continuous interfacial degradation, triggered by the spontaneous reduction of Ti4+ upon direct contact with the highly reactive lithium metal anode. In this study, a conformal two-dimensional (2D) graphitic carbon nitride (g-C3N4) layer is introduced via a facile chemical vapor deposition (CVD) process as a bifunctional interfacial modification between the LATP electrolyte and the lithium anode. This rationally designed g-C3N4 coating serves as a robust physical and electron-blocking barrier, effectively suppressing the reduction of LATP. Post-cycling XPS further indicates the formation of a Li3N-rich solid electrolyte interface (SEI), which is consistent with more stable interfacial Li+ transport during cycling. As a result, the Li|g-C3N4@LATP|Li symmetric cell exhibits markedly improved interfacial stability for over 500 cycles at 0.2 mA cm−2. In addition, the LFP|g-C3N4@LATP|Li full cell delivers a capacity retention of 81.3% after 100 cycles at 0.1 C. This work demonstrates an effective interfacial engineering strategy for stabilizing LATP-based solid electrolytes and provides a promising route toward high-performance solid-state lithium batteries.