Chen Kuan-Ting, Tuan Hsing-Yu
Department of Chemical Engineering, National Tsing Hua University, Hsinchu 30013, Taiwan.
ACS Nano. 2020 Sep 22;14(9):11648-11661. doi: 10.1021/acsnano.0c04203. Epub 2020 Sep 11.
The development of high-performance potassium ion battery (KIB) electrodes requires a nanoengineering design aimed at optimizing the construction of active material/buffer material nanocomposites. These nanocomposites will alleviate the stress resulting from large volume changes induced by K ion insertion/extraction and enhance the electrical and ion conductivity. We report the synthesis of phosphorus-embedded ultrasmall bismuth-antimony nanocrystals (BiSb@P, (0 ≤ ≤ 1)) for KIB anodes a facile solution precipitation at room temperature. BiSb@P nanocomposites can enhance potassiation-depotassiation reactions with K ions, owing to several attributes. First, by adjusting the feed ratios of the Bi/Sb reactants, the composition of BiSb nanocrystals can be systematically tuned for the best KIB anode performance. Second, extremely small (diameter ≈ 3 nm) BiSb nanocrystals were obtained after cycling and were fixed firmly inside the P matrix. These nanocrystals were effective in buffering the large volume change and preventing the collapse of the electrode. Third, the P matrix served as a good medium for both electron and K ion transport to enable rapid charge and discharge processes. Fourth, thin and stable solid electrolyte interface (SEI) layers that formed on the surface of the cycled BiSb@P electrodes resulted in low resistance of the overall battery electrode. Lastly, X-ray diffraction analysis of K ion insertion/extraction into/from the BiSb@P electrodes revealed that the potassium storage mechanism involves a simple, direct, and reversible reaction pathway: (Bi, Sb) ↔ K(Bi, Sb) ↔ K(Bi, Sb). Therefore, electrodes with the optimized composition, , BiSb@P, exhibited excellent electrochemical performance (in terms of specific capacity, rate capacities, and cycling stability) as KIB anodes. BiSb@P anodes retained specific capacities of 295.4 mA h g at 500 mA g and 339.1 mA h g at 1 A g after 800 and 550 cycles, respectively. Furthermore, a capacity of 258.5 mA h g even at 6.5 A g revealed the outstanding rate capability of the Sb-based KIB anodes. Proof-of-concept KIBs utilizing BiSb@P as an anode and PTCDA (perylenetetracarboxylic dianhydride) as a cathode were used to demonstrate the applicability of BiSb@P electrodes to full cells. This study shows that BiSb@P nanocomposites are promising carbon-free anode materials for KIB anodes and are readily compatible with the commercial slurry-coating process applied in the battery manufacturing industry.
高性能钾离子电池（KIB）电极的开发需要进行纳米工程设计，旨在优化活性材料/缓冲材料纳米复合材料的结构。这些纳米复合材料将减轻钾离子嵌入/脱出所引起的大量体积变化导致的应力，并提高电导率和离子电导率。我们报道了用于KIB阳极的磷嵌入超小铋锑纳米晶体（BiSb@P，0≤≤1）的合成——在室温下通过简便的溶液沉淀法合成。BiSb@P纳米复合材料能够增强与钾离子的钾化-脱钾化反应，这归因于几个特性。首先，通过调整Bi/Sb反应物的进料比例，可以系统地调节BiSb纳米晶体的组成，以实现最佳的KIB阳极性能。其次，循环后获得了极小（直径≈3nm）的BiSb纳米晶体，它们牢固地固定在P基质内部。这些纳米晶体有效地缓冲了大量的体积变化并防止电极坍塌。第三，P基质作为电子和钾离子传输的良好介质，以实现快速的充放电过程。第四，在循环后的BiSb@P电极表面形成的薄而稳定的固体电解质界面（SEI）层导致整个电池电极的电阻较低。最后，对钾离子嵌入/脱出BiSb@P电极的X射线衍射分析表明，钾存储机制涉及一个简单、直接且可逆的反应途径：(Bi, Sb) ↔ K(Bi, Sb) ↔ K(Bi, Sb)。因此，具有优化组成的BiSb@P电极作为KIB阳极表现出优异的电化学性能（在比容量、倍率性能和循环稳定性方面）。BiSb@P阳极在800次和550次循环后，在500 mA g和1 A g下分别保持295.4 mA h g和339.1 mA h g的比容量。此外，即使在6.5 A g下仍具有258.5 mA h g的容量，这表明基于Sb的KIB阳极具有出色的倍率性能。利用BiSb@P作为阳极和苝四羧酸二酐（PTCDA）作为阴极的概念验证KIB被用于证明BiSb@P电极在全电池中的适用性。这项研究表明，BiSb@P纳米复合材料是用于KIB阳极的有前途的无碳阳极材料，并且很容易与电池制造行业中应用的商业浆料涂覆工艺兼容。
