RGO wrapped tungsten trioxide hydrate on CNT-modified carbon Cloth as self-supported high-rate lithium-ion battery electrode

In this study, tungsten trioxide hydrate (WO3 center dot 0.33H(2)O) was partially wrapped by reduced graphene oxide (rGO) sheets to form flower-like structures, which was then directly loaded as a whole on carbon nanotube-modified carbon cloth (CNT-CC) to obtain a self-supported electrode with hierarchical structures. The orthorhombic WO3 center dot 0.33H(2)O contains a thin water layer in its crystal structure to offer abundant internal and surface channels for lithium ions. Also, the synthesized WO3 center dot 0.33H(2)O is proved to be partially reduced with mixed W5+/W6+ valence, which induces inter-valence charge transfer to bring increased conductivity. Additionally, by forming WO3 center dot 0.33H(2)O@rGO combining flowers, interpenetrating conductive network and interior mesoporosity are created, which shortens the electronic/ionic diffusion length and promotes charge transfer for WO3 center dot 0.33H(2)O. Specially, the rGO sheets are partially wrapped on WO3 center dot 0.33H(2)O, which ensures high Coulombic efficiency values by enabling active lithium-ion exchange between electrolyte and the electrode. Moreover, the thin CNT coating on the surface of the CNT-CC substrate helps to regulate the loading of WO3 center dot 0.33H(2)O@rGO by offering rich surface defects and regular attaching points, leading to the anchoring of WO3 center dot 0.33H(2)O@rGO layer with uniform morphology and thickness. Direct charge transfer is also demonstrated between WO3 center dot 0.33H(2)O@rGO and the flexible current collector of CNT-CC, thus inhibiting the use of binders causing side reactions during cycling. Moreover, the three-dimensional self-assembly structure can effectively alleviate the huge volume change of WO3 center dot 0.33H(2)O upon Li+ intercalation/extraction and ensures high structural stability. As an anode for lithium-ion batteries, the WG/CNT-CC electrode delivered high initial Coulomb efficiency of 81%, a high capacity of 1260.8 mAh g(-1) after 200 cycles at 200 mA g(-1), and a high capacity of 1087 mAh g(-1) after 400 cycles at 1000 mA g(-1), showing great potential as anode material for lithium-ion batteries. (C) 2021 Elsevier Ltd. All rights reserved.

Automated summary

In this study, tungsten trioxide hydrate was partially wrapped by reduced graphene oxide sheets to form flower-like structures and loaded on carbon nanotube-modified carbon cloth to create a self-supported electrode with hierarchical structures. The synthesized material offered abundant internal and surface channels for lithium ions and increased conductivity through inter-valence charge transfer. The hierarchical structure promoted charge transfer and shortened diffusion length, while the use of binders was avoided to inhibit side reactions during cycling.