A Fluorine-Free Binder with Organic–Inorganic Crosslinked Networks Enabling Structural Stability of Ni-Rich Layered Cathodes in Lithium-Ion Batteries

Although the high-energy Ni-rich layered cathodes suffer from undesirable surface reactions with the electrolyte, the polyvinylidene fluoride (PVDF) binder has a limitation on surface stabilization because of its weak affinity and low adhesion/cohesion. Here, it is demonstrated that the novel fluorine-free and hydroxyl-rich siloxane nanohybrid (SNH) binder can enhance the electrochemical performances of LiNi_0.8Mn_0.1Co_0.1O₂ cathode (NCM811) via successful surface stabilization. The high silanol content in the SNH binder enhances the affinity to both NCM811 and conductive agent, facilitating uniform electron/ion pathways with high mass loading, improved shear thinning, and superior mechanical properties. Moreover, the fluorine-free organic-inorganic hybrid structure prevents the dissolution of transition metals, active material structural changes, and electrolyte interaction, leading to greatly enhanced cyclability of the SNH-based NCM811 electrode (≈81.9% in half-cell; ≈87.82% in full-cell after 200 cycles) compared to PVDF-based NCM811 electrode (≈58.8% in half-cell; ≈61.24% in full-cell after 200 cycles). Various analyses also indicate that the application of the fluorine-free SNH binder successfully stabilizes both the surface and bulk structure of the NCM811 cathode during charge/discharge. The binder design represents a straightforward yet highly effective approach to achieving remarkably prolonged cyclability in lithium-ion batteries, surpassing the performance of other fluorine-based or polymer-based binders.