Highly Adhesive and Ionic Conductive Aqueous Carboxymethyl Cellulose Binder via Direct Sulfate-Ester Functionalization for Durable Graphite Anodes

Abstract

Sodium carboxymethyl cellulose (CMC) is a promising aqueous binder for graphite anodes, but its limited adhesion, poor Li⁺ transport, and interfacial instability hinder long-term performance. Herein, CMC was functionalized with lithium sulfate ester groups to obtain a multifunctional aqueous binder (CMCSL). The introduced –OSO₃Li groups strengthen interfacial interactions, improve electrolyte wettability, and facilitate Li⁺ transport, thereby preserving electrode integrity and promoting a thin, stable solid electrolyte interphase. Compared to 2.05 N for CMC and 1.33 N for PVDF, CMCSL reaches a peel force of 3.40 N, an ionic conductivity of 3.1 × 10^–3 mS cm^–1, and a Li⁺ diffusion coefficient of 7.14 × 10^–9 cm² s^–1. Consequently, the CMCSL-based electrode retains 265.43 mAh g^–1 after 1000 cycles at 1 C with 88.79% capacity retention and delivers 121.1 mAh g^–1 at 5 C. This work demonstrates an effective molecular-engineering strategy for developing durable aqueous binders with high adhesion, ion transport, and interfacial stability.