title: Hierarchical nanosheet-constructed yolk-shell TiO₂ porous microspheres for lithium batteries with high capacity, superior rate and long cycle capability.
abstract: A hierarchical nanosheet-constructed yolk-shell TiO2 (NYTiO2) porous microsphere is synthesized through a well-designed, one-pot, template-free solvothermal alcoholysis process using tetraethylenepentamine (TEPA) as the structure directing reagent. Such a yolk-shell structure with a highly porous shell and dense mesoporous core is quite advantageous as an anode material for lithium ion batteries (LIBs). The outer, 2D nanosheet-based porous (15 nm) shell and the nanocrystal-based inner mesoporous (3 nm) core provide a stable, porous framework, effective grain boundaries and a short diffusion pathway for Li(+) and electron transport, facilitating lithium insertion/extraction. The voids between the core and the shell can not only store the electrolyte due to capillary and facilitate charge transfer across the electrode/electrolyte interface but also buffer the volume change during the Li(+) insertion/extraction. As a result, NYTiO2 demonstrates excellent Li(+) capacity with outstanding cycle performance and superior rate capability at different rates for >700 cycles, retaining a 225 mA h g(-1) reversible capacity after 100 cycles at 1 C. In particular, the reversible capacity can still be maintained at 113 mA h g(-1) after 100 cycles at 10 C. We also observe the formation of homogeneously distributed 5-10 nm Li2Ti2O4 nanocrystallites on the surface of the nanosheets during the discharge-charge process. The synergy of the yolk-shell structure with dual mesopores in the shell and core and the Li2Ti2O4 nanocrystallites endow the hierarchical NYTiO2 with high reversible capacity, excellent rate capability and outstanding cycle performance.
authors.affiliation: Laboratory of Living Materials at the State Key Laboratory of Advanced Technology for Materials Synthesis and Processing, Wuhan University of Technology, 122 Luoshi Road, 430070 Wuhan, Hubei, China. yu.li@whut.edu.cn baoliansu@whut.edu.cn.
authors.forename: Jun
authors.initials: J
authors.lastname: Jin
authors.forename: Shao-Zhuan
authors.initials: SZ
authors.lastname: Huang
authors.forename: Yu
authors.initials: Y
authors.lastname: Li
authors.forename: He
authors.initials: H
authors.lastname: Tian
authors.forename: Hong-En
authors.initials: HE
authors.lastname: Wang
authors.forename: Yong
authors.initials: Y
authors.lastname: Yu
authors.forename: Li-Hua
authors.initials: LH
authors.lastname: Chen
authors.forename: Tawfique
authors.initials: T
authors.lastname: Hasan
authors.forename: Bao-Lian
authors.initials: BL
authors.lastname: Su