External Armoring Nickel-Rich Cathode with Thermoset-Functionalized Polyurethane for Enhanced Performance

Nickel-rich Li[NixCoyMn1–x–y]O2 (NCM) is critical for high-energy-density lithium-ion batteries but suffers from severe capacity fading and short cycle life, especially in high-nickel compositions such as NCM811, due to structural and interfacial instability. To address this, we develop an in situ-formed, thermoset cross-linked polyurethane acrylate (PUA) binder that acts synergistically as a robust binder and an artificial cathode–electrolyte interphase (CEI). This multifunctional PUA layer effectively shields active material from electrolyte corrosion, mitigates mechanical stress from volume change, and suppresses microcrack formation. As a result, the PUA-modified NCM811 cathode exhibits significantly improved cycling stability with 88.9% capacity retention after 200 cycles and superior rate capability (91 mAh g–1 at 5 C). Furthermore, mechanistic investigations confirm the suppression of irreversible phase transitions and metal dissolution. This work demonstrates a practical electrode engineering strategy for stabilizing nickel-rich cathodes through interfacial control.