Polyacrylic Acid Binder Enabling High Areal Capacity V₂O₅·nH₂O Cathode for Aqueous Zinc-Ion Batteries

Polyvinylidene difluoride (PVDF) is traditionally used as a cathode binder in aqueous zinc-ion batteries. However, its poor mechanical properties lead to cycling degradation of the electrodes. Herein, It is reported that polyacrylic acid (PAA) with hydrophilic carboxyl groups can serve as a high-performance binder for aqueous zinc-ion batteries. The structure and electrochemical properties of the V₂O₅·nH₂O electrode is significantly improved by using the PAA binder, showing desirable mechanical properties, enhanced electrolyte wettability, and greatly improved electrochemical reaction kinetics compared to the traditional PVDF binder. The V₂O₅·nH₂O-PAA electrode demonstrates a high-capacity retention of 84.1% after 2000 cycles at the 2 A g^-1 current density. Moreover, the thick electrode with a high active material loading of 21.4 mg cm^-2 retains a large areal capacity of 7.44 mAh cm^-2 with stable cycling, highlighting the great potential of PAA binder in practical aqueous zinc ion batteries.