Li-based layered nickel-tin oxide obtained through electrochemically-driven cation exchange.

The Li-based layered nickel-tin oxide LiNaNiSnO has been synthesized electrochemically-driven Li for Na exchange in O3-NaNiSnO. The crystal structure of LiNaNiSnO was Rietveld-refined from powder X-ray diffraction data ( = 3.03431(7) Å, = 14.7491(8) Å, S. G. 3̄). It preserves the O3 stacking sequence of the parent compound, but with ∼13% lower unit cell volume. Electron diffraction and atomic-resolution scanning transmission electron microscopy imaging revealed short-range Ni/Sn ordering in both the pristine and Li-exchanged materials that is similar to the "honeycomb" Li/M ordering in LiMO oxides. As supported by bond-valence sum and density functional theory calculations, this ordering is driven by charge difference between Ni and Sn and the necessity to maintain balanced bonding for the oxygen anions. LiNaNiSnO demonstrates reversible electrochemical (de)intercalation of ∼0.21 Li in the 2.8-4.3 V Li/Li potential range. Limited electrochemical activity is attributed to a formation of the surface Li/Ni disordered rock-salt barrier layer as the Li for Na exchange drastically reduces the energy barrier for the Li/Ni antisite disorder.