Strategic Surface Engineering of Lithium Metal Anodes: Simultaneous Native Layer Elimination and Protective Layer Formation via Gas-Solid Reaction

Abstract

Lithium (Li) metal has received significant attention as an anode material for next-generation batteries due to its high theoretical capacity and low redox potential. However, the high reactivity of Li metal leads to the formation of a native layer on its surface, inducing nonuniform Li+ flux at the electrolyte/Li metal interface, which promotes the growth of Li metal dendrites. In this study, perfluorooctyltriethoxysilane (PFOTES) was vaporized to chemically react with the native layer and modify the Li metal surface. This gas-solid reaction removes the native layer while simultaneously forming a homogeneous solid electrolyte interphase (SEI) layer. The Si-O-Si network formed through condensation reactions between PFOTES molecules, combined with the fluorinated carbon chain of PFOTES, facilitates rapid Li+ kinetics at the Li metal/electrolyte interface. Consequently, the exchange current density of PFOTES-modified Li (PFOTES-Li) increased to 0.2419 mA cm-2, which is 20 times higher than that of Bare-Li (0.0119 mA cm-2). The SEI layer derived from PFOTES effectively mitigates Li pulverization and the formation of dead Li during the long-term cycling. As a result, the PFOTES-Li||LiNi0.8Mn0.1Co0.1O2 full cell exhibits an excellent discharge capacity of 203.4 mAh g-1 under a high areal loading of 4.2 mAh cm-2. This study demonstrates a gas-solid reaction strategy for removing the native layer from the Li metal surface while forming a stable SEI layer, thereby ensuring high Li+ conductivity and mechanical stability, thus improving the cycling stability of Li metal batteries.