Transient Interfacial Electron Transfer: The Hidden Kinetic Driver of Graphite Lithiation

Graphite (Gr) lithiation is fundamentally an electron-driven process, where the temporal disparity between femtosecond-scale (10^-15 s) interfacial electron transfer (IET) and picosecond-to-nanosecond (10^-12 ∼ 10^-9 s) ion migration dictates a non-concerted kinetic response. Since electrons respond instantaneously to potential while solvated lithium (Li) remains momentarily stationary, this transient IET acts as a critical upstream "kinetic regulator" by pre-polarizing the interface, which in turn lowers the activation barrier for the subsequent rate-determining Li⁺ desolvation step. However, this foundational precursor is frequently overlooked. Compared with neutral solvents, anions possess higher charge density and frontier orbital levels, offering a superior propensity for electron transfer. In this work, we reveal that modulating anion participation in the solvation sheath can purposely tailor the Gr surface toward an electron-rich state, which effectively weakens Li⁺-solvent interactions and lowers the activation barrier of Li de-coordination. To quantify this effect, we propose the "apparent electron transfer propensity" (AETP) descriptor to bridge microscopic solvation speciation with macroscopic kinetics. This finding also elucidates why anion‑rich Li solvates or anions with high electron density delocalization (such as FSI^-) can deliver superior battery rate capability. This work establishes IET as a discrete physical criterion for deciphering kinetic bottlenecks and designing high-power battery interfaces.