Pre-zeolite framework super-MIEC anodes for high-rate lithium-ion batteries

Zeolites, Prussian blue analogues (PBAs), and metal-organic frameworks (MOFs) rely on surface-like internal pore diffusions, which have generically low activation barriers to enable the rapid uptake of chemical species. Here we show that Wadsley-Roth oxides (WROs) with pore diameters of 2.5 angstrom < d < 2.8 angstrom, while excluding molecules, enable very rapid diffusion of Li+ in single-crystal particles >10 mu m size. This supports full charge cycles at high rates of similar to 30C, which would rival the filling up of gasoline vehicles, while reducing the contact and side reactions with the electrolyte and enhancing the cycle life up to 10 000 cycles. Pore diffusion in WRO mixed ionic and electronic conductors (MIECs) differs from that in lithium intercalation compounds in the off-centered Li storage and low-coordination saddle points for migration. The reduced topological constraints per atom and large free volume in the host also lead to abnormally low or even negative thermal expansion and soft phonons, similar to other open frameworks such as zeolites, PBAs, and MOFs. Based on these guidelines, we have synthesized new composition (Nb9W4Ti4O42.5) and crystal size-coarsened H-Nb2O5 (>20 mu m single crystals) with unprecedented performance.