Phytate lithium cross-linked polyacrylamide aqueous binder mediated LiF-rich cathode electrolyte interphase stabilizes 4.6 V LiCoO₂

The practical operation of LiCoO₂ (LCO) at high voltages is limited by severe interfacial parasitic reactions and structural deterioration. Tuning interphase chemistry, mainly through electrolyte engineering and surface coating, has been proven to be effective in mitigating such degradation. Recently, replacing polyvinylidene difluoride (PVDF) with versatile binders has emerged as a promising approach to constructing stable cathode-electrolyte interphase (CEI). However, the underlying mechanisms remain poorly understood. Here, we reveal at molecular level that phytate lithium cross-linked polyacrylamide (PL-PAM) forms a uniform binder layer that modulates the solvation sheath via intermolecular hydrogen bonding. The optimized solvation structure, enriched with contact ion pairs (CIPs), facilitates the formation of a robust LiF-rich CEI, which significantly suppresses parasitic reactions and well preserves the layered LCO structure at high-voltage operation. Consequently, the PL-PAM based LCO delivers a high capacity of 206.5 mAh g⁻¹ at 0.5C and a retention rate of 89.16% after 100 cycles at 4.6 V. This work provides molecular-level insights into binder-mediated CEI formation and establishes a designing paradigm for multifunctional binders in high-voltage lithium-ion batteries. © 2026 Elsevier B.V.