Reducing the reliance on the cobalt in electrode chemistry is a promising step towards more sustainable and cost-effective lithium-ion batteries. However, the elimination of cobalt in layered oxides generally ends up with a significant decrease in capacity and/or a compromised cycle stability. Herein, we show that these intertwined issues of the cobalt-less systems can be remedied by meticulously tailoring inherent defects induced at multi-scale. It is demonstrated that a simple excess incorporation of lithium in the structure can effectively reduce the cation disorder and unexpectedly alters the microstructure forming routes, thereby enhancing electro-chemo-mechanical stabilities of layered cathodes. Our investigations reveal that this surplus lithium facilitates topotactic lithiation of precursors during calcination, rendering mechanically robust particles with fewer nano-porous defects and reduced cation disorder. Defect-regulated cobalt-free layered oxides successfully deliver a reversible capacity of 189 mAh g^-1 at 0.5C with a retention of ~85% after 300 cycles under commercial-level electrode loading.