Precise and Rapid Prelithiation of Hard Carbon Anodes via Tuning the Solution Chemistry of Aryl-Lithium Reagents

While hard carbon (HC) is a compelling anode candidate for lithium-ion batteries (LIBs), its practical viability has long been constrained by the low initial Coulombic efficiency (ICE). Chemical prelithiation using polycyclic aryl-lithium (PAH-Li) reagents offers an effective mitigation pathway, yet current methods struggle with insufficient precision and sluggish reaction kinetics. Here, we report a precise and rapid chemical prelithiation strategy for HC anodes by tuning the solution chemistry of PAH-Li reagents to simultaneously optimize thermodynamic driving force and kinetic pathways of the prelithiation reaction. Through rational molecular design, a customized phenanthrene-lithium/1,2-dimethoxyethane (E^Θ _Pha-Li/DME = 0.46 V vs. Li⁺/Li) was identified to precisely match the irreversible lithium-storage threshold potential of HC (E_HC-irr = 0.47 V), thereby establishing a self-terminating, spontaneous reaction that delivers an ideal 100% ICE. Furthermore, raising the reagent concentration to 1.5 M progressively drives Pha^•- radical anions into the Li⁺ solvation sheath, weakening the Li⁺-solvent interaction and lowering the desolvation energy barrier, which accelerates the reaction to reach equilibrium within an unprecedented 90 s. Full cells using the prelithiated anodes demonstrate marked improvements in both ICE and lifespan. This work provides new mechanistic insights into the solution chemistry design of advanced prelithiation reagents for high-performance LIBs.