A core-shell (CS) structured cathode with a LiNiO₂ core and Li[Ni_0.87Co_0.065Mn_0.065]O₂ shell, resulting in an average composition of Li[Ni_0.95Co_0.025Mn_0.025]O₂, was synthesized via the co-precipitation method. The core material, LiNiO₂, designed to maximize the discharge capacity, was protected by a 500-nm-thick encapsulating Li[Ni_0.87Co_0.065Mn_0.065]O₂ shell layer to improve the structural stability. The CS cathode delivered an initial discharge capacity of 235.7 mAh g^-1 at 0.1 C (18 mA g^-1) and 90% of its initial capacity was maintained after 100 cycles at 0.5 C (90 mA g^-1), whereas the capacity retention of the LiNiO₂ cathode without the protective shell was limited to 74.2% after 100 cycles. The improved cycling stability of the CS cathode was also verified in a full cell test (against graphite anode) in which the cathode also clearly outperformed the LiNiO₂ cathode. The improved cycling performance is mainly attributed to stabilization of the inherently reactive LiNiO₂ surface by the Ni-depleted protective shell layer. The proposed CS approach allows harnessing of the high capacity of LiNiO₂ and other extremely Ni-rich compositions with dramatically improved capacity retention, thus moving closer to satisfying the high energy density and long lifetime requirements for lithium-ion batteries for electric vehicles.

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