Cation-Effect-Driven Modulation of Interfacial Solvation Structures Enables Fast-Charging Lithium-Ion Batteries

Abstract Fast battery charging is limited by sluggish Li+ transport at the anode/electrolyte interface, which is governed by the interfacial solvation structure (ISS). However, negative polarization disfavors anion accumulation at the anode interface, hindering the formation of anion-rich ISS required for rapid Li+ transfer. Here, leveraging the cation effect in electrocatalysis, we propose a cation-mediated strategy to reshape the interfacial electric field and construct anion-rich ISS in commercial electrolytes. With benzyltriethylammonium serving as a model cationic regulator, we show that it accumulates near the polarized graphite surface and forms a cation layer that alters the local electric field. This cation-mediated interfacial regulation promotes PF6– accumulation at the interface, redirects early solid electrolyte interphase (SEI) formation toward anion-derived pathways, mitigates solvent decomposition, and accelerates Li+ desolvation and transport. As a result, graphite-based pouch cells deliver ∼88.2% state of charge within 6 min, maintain stable cycling for 2000 cycles with ∼71% capacity retention, and provide ∼218.2 Wh kg–1 with 10 min charging. Beyond LiPF6-based electrolytes, this cation effect also promotes reduction of the anions in other lithium-salt systems. This work bridges electrocatalytic cation effects and battery interfacial chemistry, offering a practical route to fast-charging lithium-ion batteries.