Designing Cellulose Triacetate‐Based Universal Binder for High‐Voltage Sodium‐Ion Battery Cathodes with Enhanced Ionic Conductivity and Binding Strength

Abstract Binders play a pivotal role in the performance of sodium‐ion battery (SIB) cathodes, but traditional binders often struggle to balance broad compatibility, high ionic conductivity, superior binding strength, and environmental sustainability. In this study, a universal cellulose triacetate (TAC)‐based binder (TAC‐MMT) composed of TAC and natural montmorillonite (MMT) is designed to facilitate rapid Na + transport pathways and establish a robust hydrogen‐bonding network. This innovative TAC‐MMT binder features a unique chemical structure that achieves high ionic conductivity through a self‐enrichment and fast‐transport mechanism, while its superior binding strength is attributed to hydrogen‐bonding crosslinks between proton acceptors (C═O) in TAC and proton donors (−OH) in MMT. More importantly, the outstanding solubility and film‐forming properties of TAC‐MMT contribute to stable electrode protection and broad compatibility with high‐voltage SIB cathodes. Benefiting from these advantages, the Na 3 V 2 (PO 4 ) 2 O 2 F (NVPOF) electrodes with the TAC‐MMT binder demonstrate exceptional performance, including a high capacity retention of 95.2% over 500 cycles at 5C and a rapid rate response of up to 15C. The versatility of the TAC‐MMT binder is further confirmed with high‐voltage NaNi 1/3 Fe 1/3 Mn 1/3 O 2 and Na 0.61 [Mn 0.27 Fe 0.34 Ti 0.39 ]O 2 cathodes. This study highlights the potential of biomass‐based binders as a sustainable and effective solution for advancing high‐performance sodium‐ion batteries.