Aqueous Sodium Humate Binder Enabling Ultra-Stable High-Voltage Cathodes via Protection from Interface to Bulk

Raising the charging cutoff voltage is a well-established approach to enhance the energy density of LiCoO₂ (LCO) cathodes, known for their high bulk energy density, in lithium-ion batteries (LIBs). However, their practical implementation under high-voltage conditions remains limited by interphase instability and bulk structural degradation. Herein, an innovative application of low-cost and water-soluble sodium humate (NaHA) is proposed, traditionally employed in aquaculture and pharmaceuticals, as a multifunctional binder for high-voltage LCO cathodes. Enriched with ─COOH and ─OH functional groups, NaHA not only forms robust hydrogen bonds with the LCO surface, enabling uniform coating on LCO particles, but also promotes a protective interphase microenvironment. More importantly, NaHA facilitates lattice-cognate in situ trace Na doping into the LCO bulk lattice during cycling, effectively enhancing its structural stability. This dual modification strategy, combining surface confinement and bulk reinforcement, endows LCO cathodes with ultra-stable electrochemical performance, retaining 95.1% capacity after 1700 cycles at 4.45 V and 87.1% over 1000 cycles at 4.5 V. Moreover, the water solubility of NaHA simplifies end-of-life electrode disassembly and promotes recyclability, supporting sustainable battery design. This binder-directed strategy offers a scalable, eco-friendly, and efficient binder-based stabilization route for high-voltage LCO cathodes, paving the way for the development of high-specific-energy LIBs.