A study is carried out on how the composition of lithium-excess oxides of d metals with the disordered rocksalt structure formed in the \({\text{L}}{{{\text{i}}}_{{1 + 0.5y}}}{\text{Ti}}_{y}^{{4 + }}{\text{M}}{{{\text{n}}}_{{1 - 1.5y}}}{{{\text{O}}}_{2}}\) and \({\text{L}}{{{\text{i}}}_{{1 + y}}}{\text{Nb}}_{y}^{{5 + }}{\text{M}}{{{\text{n}}}_{{1 - 2y}}}{{{\text{O}}}_{2}}\) systems can affect the nature of redox pairs. The samples are synthesized by a mechanochemically assisted solid-state method with the annealing temperature of 950°С. The crystal structure, the morphology, and electrochemical properties are studied by the methods of X-ray diffraction, scanning electron microscopy, and galvanostatic cycling. The particle size in the Li1 + 0.5yTiyMn1 – 1.5yO2 and Li1 + yNbyMn1 – 2yO2 samples is found to be 1–5 and 0.5–3 µm, respectively. The further grinding together with carbon lowers the particle size to 0.3–0.5 µm. The charge–discharge cycling curves demonstrate two plateaus in the potential regions of 3.5–3.7 and 4.0–4.4 V, which are attributed to the multielectron process involving the Mn3+/Mn4+ and O2–/O– redox pairs. It is shown that for the Li1 + 0.5yTiyMn1 – 1.5yO2 composites, the redox pair Mn3+/Mn4+ makes the main contribution to the discharge capacity, whereas in the case of Li1 + yNbyMn1 – 2yO2 the effect of both pairs Mn3+/Mn4+ and O2–/O– is noticeable.