Electrochemically-Induced Partial Cation Disorder Eliminates Lattice Collapse in Compositionally-Simple LiNi0.9Mn0.1O2

Virtually all layered oxide positive electrodes (cathodes) for lithium-ion batteries exhibit abrupt shrinkage along the c lattice (c-collapse) at high states-of-charge, limiting cycle life. In this work, we suppress c-collapse by electrochemically inducing partial disorder permanently throughout the bulk of compositionally-simple LiNi0.9Mn0.1O2. Our approach leverages irreversible oxygen oxidation in the as-synthesized Li-excess Ni-rich oxides to activate partial disordering of the cation sublattice, while preserving the long-range layered structure. Using this method, Li-stoichiometric transition metal oxides with variable extents of cation disorder are readily fabricated by adjusting the starting Li-excess in the as-synthesized materials. Surprisingly, at a TMLi concentration of ≥12%, the c lattice parameter remains nearly invariant during (de)lithiation, leading to decreased chemical strain, enhanced microstructural integrity, and improved battery cycle life. We demonstrate a combination of high specific capacity and long cycle life, along with negligible voltage hysteresis and decay. This concept opens the opportunity for designing materials by inducing persistent intrinsic disorder electrochemically.