Geometry-matched chelation enhances Li⁺ diffusion on electrodes binded by modified carboxymethyl cellulose

Carboxymethyl cellulose (CMC) is attracting increasing interest as a sustainable binder for flexible lithium-ion batteries, yet its dense H-bond network and poorly organized oxygen functionalities limit both chain mobility and efficient Li⁺ coordination. Here, we report a molecular-engineering strategy in which CMC is grafted with flexible, low-polarity polyisoprene chains and subsequently oxidized to generate cis-glycol units that form a geometry-matched chelation environment for Li⁺. Density-functional theory and molecular-dynamics simulations reveal that the O···O spacing of the cis-glycol pair closely matches the ionic diameter of Li⁺, enabling strong yet dynamic chelation that significantly increases Li⁺ correlation and promotes interfacial diffusion. The amphiphilicity introduced by the grafted chains improves compatibility with hydrophobic conductive carbons and weakens the original H-bond network, lowering shear viscosity by 42% and enhancing chain mobility. Galvanostatic intermittent titration and electrochemical impedance spectroscopy further confirm a 2.4-fold increase in interfacial Li⁺ diffusivity. Half-cell tests demonstrate 69% capacity retention after 500 cycles at 2C, and post-mortem microscopy and XPS analyses show a thinner, smoother, and more chemically stable SEI that suppresses dendrite formation. This study establishes geometry-matched chelation as an effective design paradigm for enhancing Li⁺ transport on electrode surfaces, providing molecular-level guidance for next-generation carbohydrate-based binders.