The synergistic optimization of the LA133 binder and electrode interface using sodium lignosulfonate comprehensively enhances the electrochemical performance of sodium-ion batteries

Sodium-ion batteries (SIBs) have become a focal point in large-scale energy storage research owing to the inherent economic advantages and the abundant sodium reserves. In sodium-ion battery that employ hard carbon as the anode, the binder is crucial for ensuring robust adhesion between the active material and the current collector, addressing issues such as numerous surface defects and inadequate mechanical properties of hard carbon, thereby maintaining electrode integrity and enhancing electrochemical performance. Polyacrylonitrile multi-copolymer LA133, an environmentally friendly aqueous binder with superior functional groups diversity compared to the conventional PVDF binder, nonetheless suffers from excessive viscosity, easy polarization, and poor electrolyte resistance. To address these challenges, this study proposes a novel composite water-soluble binder system (LA133/LS) through a molecular engineering strategy, combining LA133 with the biomass-derived sodium lignosulfonate (LS). The cyano groups (–C≡N) in LA133 form robust chemical adsorptions with defect sites on the hard carbon surface. Simultaneously, the amide (–CONH–), carboxyl (–COOH), and sulfonic acid (–SO 3 H) groups in LS interact to reversibly capture Na + , facilitating its transport within the electrode and improving Na + desolvation through Lewis acid-base interactions. The bulky aromatic framework and amphiphilicity of LS boost the binder's dispersibility, effectively dissipating stress during charge and discharge cycles, and optimizing the mechanical-electrochemical synergy of the electrode. Experimental results show that hard carbon electrodes using LA133/LS (the quality ratio is 1:1) as the binder achieve an initial coulombic efficiency (ICE) of 83.5 %, exhibit an average reversible specific capacity of 353.17 mAh g −1 at a current density of 0.05 A g −1 , and forming a stable SEI film predominantly inorganic with a certain amount of organic content. These results indicate that the LA133/LS binder can effectively regulate the interfacial molecular structure and properties, significantly enhancing the capacity and rate performance of sodium-ion batteries. Consequently, the binder offers a novel material design paradigm for the development of highly stable sodium-ion batteries. • Sodium lignosulfonate modification of LA133 overcomes its inherent drawbacks via molecular interface engineering. • The composite binder system enhances ionic conductivity, adhesion, and interfacial stability of hard carbon anodes. • Hard carbon electrode with this binder achieved 83.5% ICE and 353.17 mAh·g −1 capacity at 0.05 A·g −1 . • A robust SEI film forms with mainly inorganic components, ensuring stable long-term sodium storage performance. • Future research should explore diverse biomass modifications to further expand binder multifunctionality.