Li-and Mn-rich (LMR) nickel, manganese, and cobalt oxides as positive electrodes for lithium-ion batteries promise improved material cost and energy density over conventional layered oxides. Their high capacity and sustainable compositions, consisting predominantly of abundant Mn, with minority of Ni and little to no Co (<20 mol% metals basis) are appealing. However, issues of voltage fade, 2-7 gas release, slow kinetics, and low density 7 remain critical bottlenecks.