Π-Conjugated Polyphenols Regulate Interfacial Charge to Stabilize Lattice Oxygen in High-Voltage Ni-Rich Cathodes

Ni-rich layered cathodes operated at high voltages suffer from pronounced lattice-oxygen activation during deep delithiation, which triggers oxygen release, interfacial parasitic reactions, transition-metal destabilization, and rapid structural degradation. Here, a biomimetic interfacial-regulation strategy is reported for high-voltage LiNi_0.8Co_0.1Mn_0.1O₂ (NCM811) cathodes by introducing natural anthocyanins as π-conjugated polyphenol additives. Enabled by their conjugated electronic framework and catechol-derived binding sites, anthocyanin molecules preferentially accumulate at the cathode/electrolyte interface, where they regulate the local charge environment through anion coordination and interfacial electron delocalization. This molecularly regulated interphase moderates excessive lattice-oxygen involvement during deep delithiation and suppresses irreversible oxygen-related degradation, while promoting a thin, uniform CEI with reduced interfacial resistance and improved apparent Li⁺ transport kinetics. As a result, gas evolution, transition-metal dissolution, phase transition, and intragranular cracking are all effectively alleviated under high-voltage operation. Li||NCM811 cells deliver markedly improved cycling stability, retaining 81.4% of their capacity after 200 cycles at 4.6 V and 80.0% after over 500 cycles at 4.3 V. This work establishes π-conjugated polyphenols as a class of interfacial charge regulators for stabilizing lattice oxygen in Ni-rich layered cathodes and offers a molecular design principle for high-energy cathode interfaces.