Metastable pathways allow high rates In batteries that allow for fast charging and discharging, lithium usually forms a solid solution with the anode so that the only limiting factor is the ionic diffusion. However, for a lithium titanate (Li ₄ Ti ₅ O ₁₂ ) anode, the lithium ions interact with two phases and the diffusion is slow in both, but it still shows high-rate capabilities. Zhang et al. used electron energy-loss spectroscopy combined with density functional theory calculations to probe the anomalous behavior. They found that a diffuse interface forms between the starting and ending compositions, Li ₄ Ti ₅ O ₁₂ and Li ₇ Ti ₅ O ₁₂ , and this is what allows the lithium ions to travel quickly. Science , this issue p. 1030