The Heterogeneous Charge Transfer Mechanism in Lithium Metal Batteries: Revealing Abnormal Lithiophilicity through the Marcus Theory

Li metal batteries offer a high energy density but suffer from nonuniform Li metal electroplating and dendrite formation, limiting practical use. These issues arise from complex interfacial charge transfer kinetics, which are still ambiguously defined. Here, we reveal an abnormal dependence of Li electrodeposition kinetics on substrate lithiophilicity, rationalized by the Marcus-Hush-Chidsey (MHC) theory. Contrary to conventional expectations, lithiophobic Cu enables faster electron transfer and more stable Li electroplating at high overpotentials, whereas lithiophilic Au performs better at low overpotentials. This crossover behavior establishes a current density-dependent framework that redefines the classical understanding of lithiophilicity. Electrochemical characterizations, MHC-based modeling, and crystal orbital Hamilton population analysis attribute the phenomenon to an interplay between reorganization energy and electronic coupling strength. The findings, validated across various substrates and electrolytes, provide general mechanistic insights into heterogeneous charge transfer during Li electroplating and suggest new strategies for interface design in anodeless Li metal batteries.