Interfacial stress dissipation enabling stable solid Li metal batteries

Abstract

Li₇La₃Zr₂O₁₂ (LLZO) solid electrolyte with high mechanical strength and stability has promoted the revival of high energy density solid lithium (Li) metal batteries. However, its practical application is impeded by challenges such as dendrite penetration and insufficient interfacial contact. Thereinto, the mechanical failure of LLZO, caused by high localized internal stress introduced by Li deposition, contributes to cracks formation, which facilitates Li dendrite growth and penetration. Herein, a polytetrafluoroethylene (PTFE) film with unique node-fiber structure is constructed and applied as an interfacial stress dissipation layer between LLZO and Li anode, which displays an outstanding energy dissipation capability, contributing to relieve the high localized internal stress and restrain the LLZO crack formation. Meanwhile, its flexibility helps to accommodate the volume change of electrode, thus enabling a close interfacial contact with uniform Li deposition and decreased interfacial impedance. With this unique stress dissipation layer, symmetrical Li cells conduct critical current density as high as 5 mA cm⁻² and deliver over 2000 h lifespan at 0.2 mA cm⁻² current density, while its modified full batteries also exhibit superior electrochemical performance.