Residual alkali-evoked cross-linked polymer layer for anti-air-sensitivity LiNi0.89Co0.06Mn0.05O2 cathode

High-energy density lithium-ion batteries (LIBs) with layered high-nickel oxide cathodes (LiNixCoyMn1−x−−yO2, x ≥ 0.8) show great promise in consumer electronics and vehicular applications. However, LiNixCoyMn1−x−yO2 faces challenges related to capacity decay caused by residual alkalis owing to high sensitivity to air. To address this issue, we propose a hazardous substances upcycling method that fundamentally mitigates alkali content and concurrently induces the emergence of an anti-air-sensitive layer on the cathode surface. Through the neutralization of polyacrylic acid (PAA) with residual alkalis and then coupling it with 3-aminopropyl triethoxysilane (KH550), a stable and ion-conductive cross-linked polymer layer is in situ integrated into the LiNi0.89Co0.06Mn0.05O2 (NCM) cathode. Our characterization and measurements demonstrate its effectiveness. The NCM material exhibits impressive cycling performance, retaining 88.4% of its capacity after 200 cycles at 5 C and achieving an extraordinary specific capacity of 170.0 mA h g−1 at 10 C. Importantly, this layer on the NCM efficiently suppresses unfavorable phase transitions, severe electrolyte degradation, and CO2 gas evolution, while maintaining commendable resistance to air exposure. This surface modification strategy shows widespread potential for creating air-stable LiNixCoyMn1−x−yO2 cathodes, thereby advancing high-performance LIBs.