Ionic Liquid-Protected Edge Plane of Graphite to Overcome Initial Irreversible Capacity Loss for Improved Lithium-Ion Batteries

Lithium-ion batteries (LIBs) are considered indispensable in contemporary life because of their appropriate power density, rechargeability, and exceptional energy density. In recent decades, the crucial role of graphite (Gt) as the primary material for LIB anodes has been established. Although extensive research has been conducted to find alternatives with higher power and energy densities, Gt continues to be selected as the predominant material for commercial LIBs. During the operation of LIBs, the Gt reacts with the electrolyte to form a solid–electrolyte interphase (SEI). This complex and structurally disordered SEI layer acts as a barrier that suppresses undesirable reactions but also increases resistance, which in turn affects the LIB performance. Ionic liquids (ILs) are providing a promising solution for improving LIB performance owing to their nonflammability, low vapor pressure, tunability, and large electrochemical window. In this study, we examined the functionalization of Gt edges by employing 4-bromobenzoic acid (4BAc) via a direct Friedel–Crafts acylation reaction in a polyphosphoric acid (PPA)/phosphorous pentoxide (P₂O₅) medium. Additionally, we investigated the attachment of IL monomers to modified Gt to control the SEI layer formation. Our research findings demonstrated that IL-modified Gt exhibit significantly improved electrochemical cycle stability and durability, effectively addressing the capacity degradation and limitations of conventional Gt anodes “to” LIBs, indispensable in modern life, owe their ubiquity to their high energy density, rechargeability, and optimal power performance. Among anode materials, Gt has remained the cornerstone of commercial LIBs for decades due to its stability and cost-effectiveness. Despite extensive efforts to identify superior alternatives with enhanced power and energy densities, Gt’s dominance persists. However, during LIB operation, Gt reacts with electrolytes to form a structurally disordered SEI layer. While this layer prevents undesirable side reactions, it also increases resistance, thereby limiting LIB performance. In this study, we introduce a novel approach to address these challenges by functionalizing Gt edges using 4BAc via a direct Friedel–Crafts acylation reaction in a PPA/P₂O₅ medium. Furthermore, IL monomers were grafted onto the modified Gt surface to regulate SEI layer formation. This dual-functionalization strategy uniquely leverages the nonflammability, tunability, and wide electrochemical window of ILs to enhance anode performance. Our findings reveal that IL-modified Gt significantly improves electrochemical cycle stability and durability, mitigating capacity degradation, and resistance issues associated with conventional Gt anodes. This work offers a groundbreaking pathway to overcoming key limitations in LIB technology, advancing the development of next-generation energy storage systems.