Incorporation of a Cross-Linked Protective Layer Containing AgNO₃ Additive for Improving Cycling Stability of Anode-Free Lithium Metal Batteries

Anode-free lithium metal batteries (AFLMBs) have attracted significant attention as next-generation energy storage systems due to their high energy density, cost-effectiveness, and simplified production process, which results from the absence of reactive lithium metal. However, the practical development of AFLMBs has been obstructed by dendritic lithium growth on the lithiophobic current collector, causing continuous electrolyte decomposition and depletion of lithium sources. Various approaches, such as electrolyte design, formation of an artificial SEI layer, and use of lithiophilic materials, have been proposed to improve the uniformity of lithium deposition and extend the cycle life of AFLMBs. Among these strategies, the application of an artificial SEI layer is a simple and cost-effective way to suppress lithium dendrites by limiting their direct contact with electrolytes. In this study, we proposed an artificial 3D cross-linked polymeric protective layer (Ag-CPL) incorporating a lithiophilic AgNO₃. The cross-linked polymeric layer synthesized from three different monomers exhibited high ionic conductivity, impressive mechanical strength, and high elasticity. The embedded AgNO₃ nanoparticles were gradually dissolved into the electrolyte during cycling, releasing Ag⁺ ions that served as nucleation seeds on the current collector. The Ag-CPL facilitated uniform lithium deposition and provided mechanical strength to inhibit dendrite formation. The cycling performance of the Ni/LiNi_xCo_yAl_1-x-yO₂ (NCA) pouch cell (with an areal capacity of 4.76 mAh cm^-2) incorporating the Ag-CPL was assessed in the voltage range of 3.6 to 4.3 V at 0.5 C rate. The cell showed a high coulombic efficiency and retained 80% of its initial capacity after 200 cycles, outperforming AFLMBs without Ag-CPL.