Institute for Superconducting and Electronic Materials, Australian Institute for Innovative Materials, University of Wollongong Innovation Campus, North Wollongong, New South Wales, 2500, Australia.
School of Chemistry, Physics and Mechanical Engineering, Queensland University of Technology, Brisbane, Queensland, 4000, Australia.
Adv Mater. 2018 Dec;30(49):e1804157. doi: 10.1002/adma.201804157. Epub 2018 Oct 10.
Sodium-ion batteries (SIBs) have drawn remarkable attention due to their low cost and the practically inexhaustible sodium sources. The major obstacle for the practical application of SIBs is the absence of suitable negative electrode materials with long cycling stability and high rate performance. Here, sulfur-doped double-shell sodium titanate (Na Ti O ) microspheres constructed from 2D ultrathin nanosheets are synthesized via a templating route combined with a low-temperature sulfurization process. The resulting double-shell microspheres deliver a high specific capacity (≈222 mAh g at 1 C), excellent cycling stability (162 mAh g after 15 000 cycles at 20 C), and superior rate capability (122 mAh g at 50 C) as anode for SIBs. The improved electrochemical properties originate from synergistic effects between the unique double-shell nanostructures built from 2D nanosheets architecture and sulfur doping. This synergistic effect not only stabilize Na Ti O -based electrode during the cycling, but also improve the sluggish Na insertion/extraction kinetics by narrowing the bandgap of Na Ti O . The synthesis strategy proposed here can be developed into a technical rationale for generating high-performance sodium-storage devices.
钠离子电池（SIBs）由于其低成本和几乎用之不竭的钠资源而受到了极大的关注。SIBs 实际应用的主要障碍是缺乏具有长循环稳定性和高倍率性能的合适负极材料。在这里，通过模板路线与低温硫化工艺相结合，合成了由二维超薄纳米片构建的硫掺杂双壳层钛酸钠（Na2Ti3O7）微球。所得的双壳微球作为 SIBs 的阳极表现出高比容量（≈222mAh g-1 在 1C 下）、优异的循环稳定性（在 20C 下 15000 次循环后为 162mAh g-1）和卓越的倍率性能（在 50C 下为 122mAh g-1）。电化学性能的提高源于由二维纳米片结构构建的独特双壳纳米结构与硫掺杂之间的协同效应。这种协同效应不仅在循环过程中稳定了基于 Na2Ti3O7 的电极，而且通过缩小 Na2Ti3O7 的能带隙来提高 Na 插入/提取动力学的迟缓性。这里提出的合成策略可以发展成为一种用于制造高性能钠离子存储器件的技术原理。
