汪国秀EcoMat：锑基纳米材料助力高性能钾离子电池
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成果简介
钾离子电池（PIBs）由于其高能量密度和丰富的钾储量，在大规模储能应用中具有巨大的潜力。然而，K+的大半径及其超反应金属性质使得大多数常规电极材料难以实现可逆的电化学存储。目前，开发具有高比容量、长循环寿命和低成本的PIBs负极材料仍然是一个巨大的挑战。锑基材料因其具有高理论容量、适当的钾化电势和相对较低的成本而被公认为有前途的负极候选材料。鉴于此，悉尼科技大学汪国秀团队在EcoMat发表了题为“Antimony-based nanomaterials for high-performance potassium-ion batteries”的综述性文章，回顾了用于 PIB 的锑基负极材料的最新进展，包括金属锑、锑基合金、锑硫属化物和复合材料等。同时，本综述还重点介绍了电化学反应机制、电极材料的设计和合成策略，以及电解质改性和电极配方的进展。最后，作者提出了需要解决的关键挑战以及促进 PIB 发展途径的前景。
内容详情
FIGURE 1 A, The theoretical capacity and corresponding discharge products of the mostly studied alloy-based materials for potassium storage (graphite is presented as reference). B, Schematic illustration of the methodology for improving electrochemical performance of Sb-based anodes in potassium-ion batteries
FIGURE 2 A, In situ X-ray diffraction patterns of the three-dimensional SbNPs@C electrode during the galvanostaticde potassiation/depotassiation process at 100 mA g−1, image plot of the diffraction patterns at 28° to 33° during the first two cycles. B, Ex situ Raman spectra of a Sb/C electrode collected at different states at a current density of 0.5 A g−1. C, Crystal structure of K and stages of the structure evolution from Sb to K3Sb during the potassiation process. D, Density functional theory-calculated equilibrium voltages (vs K/K+) for the potassiation process. E, Cyclic voltammetry curves for the Sb@CSN electrode at a scan rate of 0.05 Mv s−1. F, Typical second charge/discharge profile Sb@CSN in the 4 M potassium trifluoromethane-sulfonimide (KTFSI) electrolyte at 50 mA g−1.
FIGURE 3 A, Schematic of the reducing grain size of bulk Sb material to the nanoscale. B, Scanning electron microscopy image of Sb nanoparticles. C, A comparison of rate performances of the bulk Sb and Sb nanoparticles. D, Schematic of the preparation of nanoporous Sb by the vacuum-distillation approach. Schematic of potassiation process for the, E, bulk Sb and, F, nanoporous Sb anodes.
FIGURE 4 Schematic illustrations of the Sb nanoparticles anchored on the, A, one-dimensional (1D) nanofibers, B, two-dimensional (2D) nanosheets, and, C, three-dimensional (3D) porous network. D, Scanning electron microscopy (SEM) and, E, transmission electron microscopy (TEM) images of the u-Sb@CNFs. F, SEM image, G, TEM image and (inset of G) particle size distribution of the Sb/CNS. H, Low-magnification and, I, high-magnification SEM images of 3D SbNPs@C.
FIGURE 5 A, Schematic of the structural evolution of the Sb-C-rGO during potassiation and depotassiation. B, Cycling performance of the Sb-C and Sb-C-rGO composites at 0.5 A g−1. C, Schematic illustration of the MS@C and MoS2/Sb heterostructure (MS) composites during long-term cycling. D, Cycling performance of the MS@C and MS at 0.5 A g−1.
FIGURE 6 A, Schematic illustration of the preparation of the BiSb@C composite. B, X-ray diffraction (XRD) pattern with Reitveld-refined results, C, Scanning electron microscopy, D, transmission electron microscopy (TEM), and, E, High-resolution TEM (HRTEM) images of the BiSb@C. F, Cycling performance of Bi@C, Sb@C and BiSb@C electrodes. G, Operando XRD results of BiSb@C anode during the first and second cycles and the proposed potassium storage mechanism.
FIGURE 7 A, Schematic illustration of the structural change of bulk Sb2S3 and few-layered Sb2S3/carbon (SBS/C) electrodes. (B) TEM image of the SBS/C composite and corresponding energy disperse spectroscopy spectrum of the indicated area. Scale bars: 200 nm. C, Rate capabilities of SBS/C electrodes exfoliated with different solvents obtained at the various charge and discharge current densities and their cycling performance after rate testing at 500 mA g−1. D, Schematic illustration of the potassiation/depotassiation process in (Bi,Sb)2S3.
FIGURE 8 A, Nanoindentation force of the alloy anode at a given indentation depth after cycling in potassium hexafluorophosphate (KPF6) and potassium bis(fluorosulfonyl)imide (KFSI) electrolyte, respectively. Surface potential maps of the electrode for, B, KPF6 electrolyte and, C, KFSI electrolyte, respectively. D, The cycling performance of Sb/C electrodes in KPF6 and KFSI electrolytes at 50 mA g−1. E, Cycling performance of the Sb@CSN electrode at 100 mA g−1 in different electrolytes. F, In-depth X-ray photoelectron spectroscopy (XPS) spectra in the F1s region for the Sb@CSN electrode in 1 M and 4 M potassium trifluoromethane-sulfonimide (KTFSI) electrolyte. G, Illustration of the influence of dilute and concentrated electrolytes on the formation of the solid electrolyte interface (SEI) layer.
结论与展望
本综述系统回顾和总结了Sb和Sb基合金用作PIB负极的最新进展。锑具有较高的理论容量和适当的钾化电位，被认为是一种很有前途的合金型PIB负极材料。然而，Sb电极在嵌钾/脱钾过程中体积变化较大，导致循环性能较差，阻碍了其实际应用。为了解决这些问题，大量的工作致力于Sb的纳米工程、将Sb与导电基体复合、合金化以及构建分层多孔纳米复合材料。这些策略能够有效缓冲Sb的体积变化，促进电子和离子电导率，并提高充放电过程中的电化学动力学，从而提高倍率性能和循环性能。除了金属Sb之外，锑硫属元素化物由于其高理论容量和低成本也被认为是有前途的PIB负极材料。此外，相较于金属Sb，这些金属硫化物/硒化物的形貌可以更容易地通过自下而上或自上而下的方法进行调控，从而有利于电极构造。
除了对Sb基材料进行优化外，电解质组成是决定SEI层形成的另一个重要因素，对储钾的循环性能也有很大影响。特别地，合适的电解质可以减少钾与电解质之间的副反应，提高PIBs的库仑效率。此外，还可以通过调控电极中的其他组分（如粘合剂和碳添加剂）来提高电池性能。尽管在过去几年中Sb基负极在钾储方面已经取得了巨大进步，但仍需要进一步的研究以加速PIB的实际应用。
1. 尽管钾储存机制已有广泛报道，但很少有研究详细探究电池失效机制。深入的研究对于全面了解Sb基电极的失效机制至关重要，可以有效指导未来电极的设计。值得注意的是，在半电池中，金属钾的降解可能比Sb基负极的降解更严重。因此，应更加关注金属钾作为对电极对容量衰减的影响。为了避免这个问题，应组装全电池来评估电化学性能。
2. 通过合金化提高性能的研究不应仅限于那些可以与Sb形成合金的元素。先前的工作表明，即使两种成分不会相互合金化，简单地将Sb与黑磷混合也可以大大提高循环性能。此外，电化学反应过程中的原位合金化是另一种值得考虑的缓冲体积变化的途径。特别地，此类与钾具有反应活性的材料可能对稳定电极结构以及提高电池容量具有协同作用。
3. 通过纳米结构来缓解Sb基负极的巨大体积膨胀不可避免地降低了电极材料的振实密度和最终器件的体积密度。由体积变化引起的机械应力在高负载下会变得更加严重，导致电极退化更快。因此，未来的研究也应关注高负载下的电化学性能。我们可以得出结论，将金属锑或锑硫属元素化物与石墨以及其他导电基体复合可以很好地平衡容量和循环稳定性，适合实际应用。
电解质改性对PIB的电化学性能有关键影响。优化的电解质不仅具有高离子电导率，而且有助于在正极和负极两侧形成坚固且导电的SEI。应致力于开发低成本、稳定、安全的高性能合金负极电解质，并研究其基础机制。
希望这些观点能给该领域的研究人员带来一些启发，促进PIBs负极材料的发展。该综述中总结的提高Sb基负极性能的纳米工程也适用于改性可充电电池中许多其他转化和合金类型的电极材料。
文献信息
Hong Gao, Xin Guo,* Shijian Wang, Fan Zhang, Hao Liu,* Guoxiu Wang,* Antimony-based nanomaterials for high-performance potassium-ion batteries, EcoMat. 2020;2: e12027.
原文链接：https://doi.org/10.1002/eom2.12027
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