A multifunctional polymer brush network binder for high-nickel cathodes: architecture-driven elastic recovery, adhesion, and Li+ transport

Abstract

Fabricating thick, high-loading electrodes using nickel-rich layered oxides such as LiNi_xCo_yMn_zO₂ (NCM) is essential for maximizing energy density of lithium-ion batteries, but it also intensifies mechanical and interfacial stresses that compromise cycling stability. Here, we report a multifunctional polymer brush network (PBN) binder synthesized by covalently cross-linking poly(vinylidene fluoride)-graft-poly(acrylic acid) with polyethylene glycol diglycidyl ether (PEGDGE). This architecture-driven design imparts pseudo-elastic recovery through network elasticity, strong adhesion via hydrogen-bond-rich side chains, and enhanced Li⁺ transport facilitated by PEG domains. Comprehensive mechanical analyses reveal that the PBN binder mitigates the brittleness of conventional PVDF while exhibiting improved toughness, elasticity, and stress recovery, which together enable excellent capacity retention under both high-loading and lean binder conditions. High-rate performance correlates with improved Li⁺ diffusion and favorable Li⁺-binder interactions, as confirmed by electrochemical measurements and theoretical calculations. Post-mortem analyses of cycled cathodes further highlight the critical role of binder multifunctionality in preserving electrode integrity and stabilizing the cathode–electrolyte interphase (CEI). This study emphasizes the importance of architecture-driven multifunctionality in binder design and establishes the PBN binder as a robust platform for high-performance lithium-ion batteries.