Unexpected reversible crystalline/amorphous (de)lithiation transformations enabling fast (dis)charge of high-capacity anatase mesocrystal anode

High-power, fast-charging capability is an urgent issue for the development of advanced Li-ion batteries (LIBs) for electrified mobility applications. An anatase titanium oxide mesocrystal (TOM) Li-ion battery (LIB) anode comprising extremely small (3–5 nm) and crystallographically coherent nanocrystallite subunits demonstrate a high specific capacity (up to 225 mAh g -1 ) and extraordinary rate capability and cycle stability under stressful currents (83 % capacity retention after 9000 cycles at 10 C rate, 1 C = 168 mA g -1 ), considerably outperforming the conventional nanocrystalline titanium oxide (TO) electrode. The investigation of the underlying (de)lithiation mechanism using synchrotron X-ray analyses and density functional theory calculations reveals a novel crystalline–amorphous–crystalline pathway for TOM involving an amorphous phase existing within a Li stoichiometry range approximately Li x TiO 2 , x = 0.2–0.9. The combination of structure amorphization and existing of a fast inter-grain diffusion network inherent to the hierarchical interior of mesocrystal empowers the TOM electrode with orders-of-magnitude higher diffusion rates as compared with the TO electrode. The single-crystal-like crystallographic coherence of the (de)lithiation end-products enables favorable chemo-mechanical stability to avert particle cracking during high-rate cycling. The study indicates a potential new direction for engineering cycle-stable fast-charging electrode materials.