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Lithium-rich layered oxides (LLOs) exhibit great potential as high-capacity cathode materials for lithium-ion batteries, but usually suffer from capacity/voltage fade during electrochemical cycling. Herein, a gradient polyanion-doping strategy is developed to initiate surface structural transition to form a spinel-like surface nanolayer and a polyanion-doped layered core material in LLOs simultaneously. This strategy integrates the advantages of both bulk doping and surface modification as the oxygen close-packed structure of LLOs is stabilized by polyanion doping, and the LLO cathodes are protected from steady corrosion induced by electrolytes. A LLO material modified with 5 at% phosphate (5%P@LLO) shows a high reversible discharge capacity of ≈300 mAh g−1 at 0.1 C, excellent cycling stability with a capacity retention of 95% after 100 cycles, and enhanced electrode kinetics. This gradient doping strategy can be further extended to other polyanion-doped LLO materials, such as borate and silicate polyanions. [ABSTRACT FROM AUTHOR]