Enhanced high-voltage cycling stability of nickel-rich cathodes through sodium doping and oxide surface coatings

초록

Nickel-rich layered oxides are promising high-energy cathodes but suffer from structural instability and interfacial degradation under high-voltage operation. Here, we report a dual-functional strategy integrating sodium (Na+) lattice doping with conformal LaAlO3, LaTiO4, and TiSiO4 surface nanolayers on LiNi0.83Co0.11Mn0.06O2. Sodium incorporation suppresses Li/Ni anti-site disorder, expands inter-slab spacing, and enhances lithium (Li+) transport kinetics. Ultrathin (2-3.7 nm) coatings induce stable, Li-conductive interphases that mitigate electrolyte reactivity and oxygen release. Structural and spectroscopic analyses reveal reduced cation mixing, strengthened TM-O covalency, and regulated surface chemistry. The optimized LaAlO3-coated Na-doped cathode exhibits superior electrochemical performance, achieving 84.13% capacity retention at 0.5C and 79.44% at 1C after 100 cycles (2.8-4.5 V), along with markedly reduced interfacial resistance. The synergistic bulk-surface modulation suppresses irreversible H2-H3 phase transitions and stabilizes high-voltage cycling. This work establishes a rational design paradigm for engineering durable, high-energy Ni-rich cathodes by coupling lattice and interfacial properties.

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