Strengthening the susceptible interphase of layered oxide cathodes via eco-friendly aqueous binders

Layered oxides present compelling potential as cathode materials for sodium-ion batteries (SIBs). However, challenges including interfacial instability and sluggish reaction kinetics critically limit their rate capability and cycling performance. Herein, we introduce the water-soluble sodium polyacrylate (NaPAA) binder as a promising approach to mitigating these issues in P2-type layered oxides. The NaPAA binder facilitates the formation of a uniform Na+ conductive interfacial film, which protects the cathode against electrolyte-induced corrosion and effectively inhibits the dissolution of transition metals in P2-Na0.85Li0.12Ni0.22Mn0.66O2 (NLNMO). Furthermore, we elucidate the mechanism by which the NaPAA binder dynamically regulates the coordination of free anions at the electrode–electrolyte interface. This regulation reduces solvent decomposition and promotes the formation of a stable, ionically conductive layer. Consequently, the P2-NLNMO@NaPAA integrated electrode exhibits enhanced electrochemical performance, achieving an 89.2 % capacity retention after 200 cycles at 0.2 C and delivering an initial capacity of 102.9 mA h g−1 even at 0 °C. This study advances the fundamental understanding of binder-mediated interface engineering and demonstrates a scalable and eco-friendly manufacturing pathway for high-performance SIBs.