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.

One‐Pot Fabrication of Hierarchical Nanosheet‐Based TiO2–Carbon Hollow Microspheres for Anode Materials of High‐Rate Lithium‐Ion Batteries

“…21‐1272), confirming that A‐TiO 2 NHS possess an anatase phase with good crystallinity and purity. The uncalcined TiO 2 NHS (Figure a) and calcinate under N 2 (C/TiO 2 NHS, Figure b) have moderate crystalline in the anatase phase and an extra peak of 8.8 °, reflecting the lamellar structure with a layer spacing of ≈10.1 Å . The result obtained from XRD patterns is in good agreement with the SAED patterns and indicates the better inheritance of original morphology and structure under N 2 calcination.…”

“…The difference of reversible capacity between these two calcinated hierarchical materials at current rates of 5 C is even more remarkable, implying that the dominant interface‐based storage of C/TiO 2 NHS, which originates from the appropriate integration of the inherited hierarchically nanosheet‐based hollow structure and carbon doping, possesses higher kinetic efficiency than the dominant bulk intercalation and phase change of A‐TiO 2 NHS. The high‐capacity and high‐rate performance of C/TiO 2 NHS were approximately equal to rutile TiO 2 submicroboxes and hierarchical yolk‐shell TiO 2 porous microspheres, and even surpass the previously reported TiO 2 hollow microspheres, porous anatase TiO 2 , and TiO 2 ‐carbon composite . Therefore, C/TiO 2 NHS are promising anode materials for fast rechargeable LIBs.…”

“…Developing new materials with excellent rate performance, long‐term cycling life, and safety has always been the priorities of the present studies. Recently, TiO 2 and TiO 2 ‐based materials have been demonstrated as promising anodes because of their low cost, structural stability, and marginally high working potential, as well as their avoidance of the formation of the solid electrolyte interfacial (SEI) layers for better safety . Nevertheless, the performance of the TiO 2 ‐based anode materials, especially their inherent poor electronic conductivity and sluggish Li + diffusion, is still not satisfactory for large‐scale commercialization.…”

Multishelled Ni x Co3- x O4 Hollow Microspheres Derived from Bimetal-Organic Frameworks as Anode Materials for High-Performance Lithium-Ion Batteries

“…As a result, electrical energy storage technology plays a decisive role to address this challenge. Rechargeable lithium‐ion batteries (LIBs), as the ideal electrical energy storage device, have been the leading power source because of their relatively high energy density, long lifespan, and environmentally friendliness . As we all know, traditional graphite offers a low theoretical capacity (372 mAh g −1 ) when served as anode material in LIBs, which would restrict the booming market for portable electronic devices and the development of electric vehicles (EVs)/hybrid EVs, and also stationary energy storage systems .…”

Solvothermal alcoholysis synthesis of hierarchical TiO 2 with enhanced activity in environmental and energy photocatalysis

“…The structure, crystalline phase, and porosity of TiO2 significantly affect the lithium ion diffuse and electron transportation. TiO2 yolk-shell microspheres comprising of a shell with high porosity and dense mesoporous core showed great advantages as an anode in lithium batteries (LIBs) [83]. As shown in Fig.…”