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

• Published in: Nano energy 2022-11, Vol.102, p.107715, Article 107715
• Main Authors: Wu, Junxiu, Liu, Hao-Wen, Tang, Anwen, Zhang, Weifeng, Sheu, Hwo-Shuenn, Lee, Jyh-Fu, Liao, Yen-Fa, Huang, Shuping, Wei, Mingdeng, Wu, Nae-Lih
• Format: Article
• Language: English
• Subjects: Anatase TiO2; Fast charging; Li-ion battery; Mesocrystal; Phase transformation
• ISSN: 2211-2855
• DOI: 10.1016/j.nanoen.2022.107715

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 LixTiO2, 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. [Display omitted] •Revealing a highly reversible crystalline–amorphous–crystalline lithiated pathway.•The final crystalline phase delivers a capacity about twice theoretical value.•The amorphous intermediate of LixTiO2 over a wide range of Li stoichiometry (x = 0.2–0.9).•Rapid grain-boundary diffusion network allowing uniform (de)lithiation.•Discovering an engineering cycle-stable fast-charging TiO2 mesocrystal electrode.