Dynamic cathode-electrolyte interphase structuring by Al-F dual surface engineering for exceptional stability of Ni-rich NCM811 cathodes

초록

High-nickel layered oxides, particularly LiNi0.8Co0.,Mn0.,O2(NCM811), are regarded as front-runners for next-generation lithium-ion battery cathodes due to their high energy density and reduced cobalt content. However, their practical implementation is hindered by rapid surface degradation, oxygen evolution, and severe lattice collapse under high-voltage operation. Here, we propose a dynamic cathode-electrolyte interphase (CEI) engineering strategy via a synergistic Al-F dual surface modification, which concurrently stabilizes the bulk lattice and protects the interface. Fluorination with ammonium fluoride (NH4F) promotes the formation of a dense, LiFenriched CEI, while a conformal Al2O3 nanoshell provides adaptive protection against parasitic reactions and mechanical stress. The dual-modified NCM811 exhibits outstanding electrochemical performance, delivering a high initial discharge capacity of 227 mAh g-1 at 0.1C and maintaining 93.2 % capacity retention over 500 cycles at 0.2C. In-situ and ex-situ analyses, including X-ray diffraction and electrochemical impedance spectroscopy, reveal significant suppression of lattice distortion and interfacial resistance under high-voltage cycling. This scalable and cost-effective approach offers a universal platform for enabling high-voltage stability in Ni-rich cathodes, advancing their commercialization in high-energy lithium-ion batteries.

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