A Fluorine-free Polysulfone-Polyamide-Polyimide Copolymer Binder for LiNi0.8Co0.1Mn0.1O2 Cathode in Lithium-ion Battery

High-voltage LiNi 0.8 Co 0.1 Mn 0.1 O 2 (NCM811) cathodes are critical for enhancing the energy density of lithium-ion batteries (LIBs). The development of binders compatible with high-voltage NCM811 cathode materials is crucial to enhance the electrochemical performance of LIBs. However, the traditional fluoropolymer binder, poly(vinylidene difluoride) (PVDF), can potentially leach components or break down into poly(fluoroalkyl substances) (PFAS) chemicals, thereby contributing to PFAS contamination. A novel fluorine-free polymer, polysulfone-polyamide-polyimide (SPIO), was designed and synthesized as a binder for NCM811 cathodes. The SPIO binder exhibits exceptional mechanical properties and superior electrochemical characteristics. The cathode film fabricated with SPIO demonstrated a remarkable delamination force of 8 N (390 N·m −1 ), indicating robust adhesion. The Li∥NCM811 cell incorporating the SPIO binder retained 80% of its initial capacity after 300 cycles at a current density of 0.2 C. In comparison, the control cells assembled with the PVDF binder retained only 52% of their capacities under the same cycling conditions. Furthermore, the SPIO binder exhibited improved compatibility with the electrolyte. Transmission electron microscopy analysis of the cathode films after 100 cycles revealed the formation of a uniform, dense, and continuous chemical-electrochemical interface (CEI) by the SPIO binder on the surface of the NCM811 particles, which significantly contributed to the enhancement of the electrochemical performance. These results highlight the potential of SPIO as an advanced binder material for high-performance lithium-ion batteries.