Interfacial stabilization strategy via In-doped Ag metal coating enables a high cycle life of anode-free solid-state Li batteries

"Anode-free" solid-state Li batteries have recently gained attention for achieving superior energy density by eliminating Li from the anode. However, they face significant challenges in practical applications, primarily due to the unstable interface between the solid electrolytes and the bare current collector. Here, we introduce an In-doped Ag metal coated current collector, which can induce a synergetic effect, and optimize the composition of Ag and In. Interestingly, with adding only small amount of In, the performance significantly improves compared to using Ag alone. Li undergoes the alloying reaction with Ag-In layer during Li deposition, as verified through scanning electron microscopy, X-ray photoelectron spectroscopy and X-ray diffraction analyses. In the full-cell tests with the NCM cathode, it delivered stable cycle life (>80 %) over 250 cycles at 1 C-rate and maintained a stable average Coulombic efficiency of 99.8%. This study marks a significant step forward in enhancing interfacial stability and thereby extending the cycle life of anode-free solid-state Li batteries.