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

Abstract

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 LiNi0.8Mn0.1Co0.1O2 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 (approximate to 81.9% in half-cell; approximate to 87.82% in full-cell after 200 cycles) compared to PVDF-based NCM811 electrode (approximate to 58.8% in half-cell; approximate to 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. A Fluorine-Free organic-inorganic crosslinked siloxane-based nanohybrid (SNH) binder enabling stabilization of Ni-rich layered cathodes with a novel materials design strategy is reported. Thanks to fluorine-free and robust nanohybrid-type network structure in SNH, exceptional cyclability of Ni-rich cathode-based lithium-ion batteries is achieved by stabilizing the structure of cathode active material. image