Abstract: A method of manufacturing a positive electrode for a battery that cycles lithium ions is disclosed, as well as a battery including the positive electrode. In the disclosed method, a single crystal precursor particle is placed in contact with an aqueous solution. The precursor particle includes a lithium-rich manganese-based transition metal oxide (LRMO) having a layered crystal structure, and the aqueous solution includes exchangeable cations. When the precursor particle is placed in contact with the aqueous solution, lithium ions are removed from an exterior surface portion of the precursor particle and the LRMO in the exterior surface portion of the precursor particle is transformed into a lithium-deficient manganese-based oxide (LDMO). Then, the precursor particle is heated such that the LDMO in the exterior surface portion of the precursor particle undergoes a phase transition and is transformed into a lithium manganese-based transition metal oxide having a spinel crystal structure (spinel-LMO).