Aqueous Guar Gum Binder Enables Regulated Surface Structure Evolution and Enhanced Electrochemical Performance of NFPP/Activated Carbon Composite Cathodes for Sodium‐Ion Batteries

Na 4 Fe 3 (PO 4 ) 2 (P 2 O 7 ) (NFPP) has emerged as a promising low‐cost, structurally stable cathode material for sodium‐ion batteries. However, the intrinsically low electronic conductivity of NFPP limits NFPP/activated carbon (NFPP/AC) composite performance. Considering that polymer binders control electrode microstructures and sodium‐ion reaction kinetics, the authors incorporated an aqueous guar gum (GG) binder into an NFPP/AC cathode and benchmarked it against polyvinylidene fluoride (PVDF) and carboxymethyl cellulose (CMC)/styrene‐butadiene rubber (SBR) systems. The GG‐based electrode slurry demonstrates superior rheological properties that facilitate electrolyte infiltration, promote uniform particle dispersion and improve electrode structural integrity. This effect is primarily ascribed to the hydroxyl‐rich structure of GG, which establishes hydrogen‐bond‐mediated multipoint interfacial interactions between NFPP and AC particles, enhancing particle dispersion, slurry structural recovery and interparticle contact. GG also promotes a uniform, dense, inorganic‐rich cathode‐electrode interface, minimizing charge‐transfer resistance and activation energy (61.1 kJ·mol −1 ). Consequently, the GG‐based electrode maintains a high Na + diffusion coefficient during cycling, retaining 73.8 mAh·g −1 at 5C and showing negligible capacity fading after 400 cycles at 1C. Overall, GG constructs a continuous interfacial binding network between NFPP and AC, regulating interfacial chemistry, structural integrity and Na + transport pathways.