To extend the lifespan of Ni-rich layered oxide cathodes, doping, coating, and particle-morphology optimization strategies have been explored, often resulting in reduced reversible capacity. In this study, we introduce a novel LiNi0.92Co0.04Mn0.04O2 cathode featuring gradients in Li concentration and particle size at the secondary-particle level. By controlling the oxygen partial pressure during synthesis, enhanced cycle stability can be achieved without compromising the capacity for this unique structure. Contrary to common knowledge, we report the superior performance of cathode materials synthesized under oxygen-deficient conditions, with delivery of a remarkable capacity of 226.7 mAh g−1 and robust cycle retention of 87.23% after 200 cycles. Through comprehensive diffraction and microscopy analyses, we identified secondary particles with Li-excess structures on their surfaces (characterized by larger primary particles) and stoichiometric structures in the core (featuring smaller primary particles). These distinctive compositions and structures contribute to both the high capacity and cycle stability. Our study highlights the potential of using Li concentration gradients in mitigating surface side reactions, paving the way for the development of durable, high-capacity, and cost-effective cathodes.