Eliminating lattice collapse in dopant-free LiNi0.9Mn0.1O2 cathodes via electrochemically induced partial cation disorder

Abstract

Layered oxide cathodes for lithium-ion batteries typically undergo large expansion and contraction during cycling, including a particularly abrupt shrinkage along the c lattice (c-collapse) at high states of charge, which limits their lifetime. Here we suppress the c-collapse in compositionally simple LiNi0.9Mn0.1O2 by electrochemically inducing partial disorder that is permanently retained throughout the bulk. Our approach leverages irreversible oxygen oxidation in Li-excess Ni-rich oxides to activate partial disordering of the cation sublattice, while preserving the long-range layered structure. By varying the initial Li-excess, we obtain Li-stoichiometric transition-metal oxides with tunable cation disorder. Surprisingly, when the concentration of transition-metal ions occupying Li sites (TMLi) reaches ≥12%, the c-lattice parameter remains nearly invariant during (de)lithiation, reducing chemical strain, preserving microstructural integrity and extending battery cycle life. The resulting material displays high specific capacity, long-term stability, small voltage hysteresis and negligible voltage decay. This concept opens the possibility of designing materials by inducing persistent intrinsic disorder electrochemically.