Enhancing lithium storage in Co-free Li-rich Li1.2NixMn0.8-xO2 through the tuning Ni/Mn ratio

Co-free Li-rich layered Li 1.2 Ni x Mn 0.8− x O 2 (x = 0.2, 0.3, 0.4) was synthesized by co-precipitation using an α-MnOOH sacrificial template. XRD with Rietveld refinement and electron microscopy confirm a well-developed layered framework consisting of R 3 ‾ m and Li 2 MnO 3 -like C2/m domains, together with a clustered morphology assembled from small primary particles. Varying the Ni/Mn ratio tunes the phase balance and the extent of Ni/Li antisite disorder and is accompanied by stacking disorder associated with minor Ni 2+ incorporation in the Li layer of the monoclinic component, improving Li + transport and electrochemical reversibility. The optimized composition (x = 0.3; Ni/Mn = 0.6) delivers 256.05 mAh g −1 at 0.1C and 208.57 mAh g −1 at 0.5C (1C = 200 mA g −1 ), with 96.71% capacity retention after 100 cycles at 0.1C in half-cells. These results define a practical design window for Co-free Li-rich layered cathodes enabled by α-MnOOH-templated synthesis.