Staggered Quadruple-Rutile Oxides as Low-Strain and High-Power Anodes for Lithium-Ion Batteries

Tunnel-structured oxides provide attractive hosts for lithium-ion storage. However, their application is frequently limited by structural instability or sluggish ion transport at high lithium contents. Here, we demonstrate that the staggered quadruple-rutile framework represents a structurally robust and electrochemically viable host for lithium insertion. A nonstoichiometric Li1-δCr1-δTi1+δO4 (δ = 0.15) reversibly accommodates 1.15 Li per formula unit, corresponding to a reversible capacity of ∼183 mAh g-1 at moderate potentials (≈ 1-2 V vs Li/Li+). Lithium insertion proceeds via a continuous solid-solution reaction without phase separation, where the opposing responses along the a- and c-axes result in an almost net-zero unit-cell volume change (≈ -0.4%) upon full lithiation. Lithium diffusion in this tunnel framework exhibits a low activation energy of ∼0.21 eV. The combination of moderate reaction potential, large reversible capacity, excellent rate capability, minimal volume change, and fast lithium mobility identifies the staggered quadruple-rutile framework as a promising platform for high-power and fast-charging lithium-ion battery anodes.