Wang Xinxin, Wu Yang, Huang Peng, Chen Peng, Wang Zuyong, Xu Xiongwen, Xie Jian, Yan Ji, Li Shuigen, Tu Jian, Ding Yuan-Li
College of Materials Science and Engineering, Hunan University, Changsha, 410082, China.
Nanoscale. 2020 Dec 8;12(46):23682-23693. doi: 10.1039/d0nr07230c.
Bismuth (Bi) is a promising anode candidate for sodium ion batteries (SIBs) with a high volumetric capacity (3765 mA h cm-3) and moderate working potential but suffers from large volume change (ca. 250%) during the sodiation/desodiation process, resulting in pulverization of the electrode, electrical contact loss, excessive accumulation of solid electrolyte interfaces, etc., devastating the cycling stability of the electrode seriously. Addressing this issue significantly relies on rational micro- and nano-structuring. Herein, we prepared a 3D multi-layered composite assembly of Bi/carbon heterojunctions with 0D bismuth nanospheres distributed and anchored on 2D nitrogen-doped carbon nanosheets (NCSs), using a preorganization strategy by taking full advantage of the strong complexation ability of Bi3+. The multi-layered composite assembly is periodic and close-packed, with Bi nanospheres <25 nm, carbon nanosheets ∼30 nm, and an average interlayer space of ∼75 nm. Such a specific architecture provides abundant electrochemically active surfaces and ion migration channels as the Bi nanospheres are attached to the 2D nitrogen-doped carbon nanosheets via a point-to-surface pattern. Moreover, the mono-layer Bi nanospheres oriented along the 2D-surface of NCSs are kinetically favorable for the recognition of Na+ by the active sites of Bi nanospheres as well as for avoiding the long distance migration of Na+ (external diffusion of Na+). Furthermore, thermodynamically, the small size and high surface energy of ultrasmall Bi nanospheres could contribute to high ion mobility (internal diffusion of Na+) and promote electrochemical reactions as well. The multi-layered composite assembly of Bi@NCSs (ML-Bi@NCSs) not only provides a robust 3D framework guaranteeing the whole structural stability but also ensures direct and full contact of each active nano-building block with electrolyte, thereby forming a high-throughput electron/ion transport system. When evaluated as the anode for SIBs, ML-Bi@NCSs deliver superior high-rate capability up to 30 A g-1 (specific capacity: 288 mA h g-1) and long-term cycling stability (capacity retention: 95.8% after 5000 cycles at 10 A g-1 and 90.6% after 10 000 cycles at 20 A g-1, respectively).
铋（Bi）是钠离子电池（SIBs）中一种很有前景的负极候选材料，其具有高体积容量（3765 mA h cm-3）和适中的工作电位，但在 sodiation/desodiation 过程中会发生较大的体积变化（约 250%），导致电极粉化、电接触损失、固体电解质界面过度积累等问题，严重破坏了电极的循环稳定性。解决这个问题很大程度上依赖于合理的微观和纳米结构设计。在此，我们利用 Bi3+ 的强络合能力，采用预组织策略，制备了一种 Bi/碳异质结的 3D 多层复合组件，其中 0D 铋纳米球分布并锚定在 2D 氮掺杂碳纳米片（NCSs）上。多层复合组件具有周期性且紧密堆积，铋纳米球 <25 nm，碳纳米片约 30 nm，平均层间距约 75 nm。这种特殊的结构提供了丰富的电化学活性表面和离子迁移通道，因为铋纳米球通过点对面模式附着在 2D 氮掺杂碳纳米片上。此外，沿 NCSs 的 2D 表面取向的单层铋纳米球在动力学上有利于铋纳米球的活性位点识别 Na+，也有利于避免 Na+ 的长距离迁移（Na+ 的外部扩散）。此外，从热力学角度来看，超小铋纳米球的小尺寸和高表面能有助于提高离子迁移率（Na+ 的内部扩散）并促进电化学反应。Bi@NCSs 的多层复合组件（ML-Bi@NCSs）不仅提供了一个坚固的 3D 框架，保证了整体结构的稳定性，还确保了每个活性纳米构建块与电解质的直接和充分接触，从而形成一个高通量的电子/离子传输系统。当作为 SIBs 的负极进行评估时，ML-Bi@NCSs 具有出色的高倍率性能，高达 30 A g-1（比容量：288 mA h g-1）和长期循环稳定性（容量保持率：在 10 A g-1 下 5000 次循环后为 95.8%，在 20 A g-1 下 10000 次循环后为 90.6%）。
