三元二维层状过渡金属硫属化合物助力高性能钾离子电池

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三元二维层状过渡金属硫属化合物助力高性能钾离子电池

Unlocking Few-Layered Ternary Chalcogenides for High-Performance Potassium-Ion Storage

Huajun Tian, Xuechao Yu, Hezhu Shao, Liubing Dong, Yi Chen, Xiaqin Fang, Chengyin Wang, Weiqiang Han, and Guoxiu Wang

DOI: 10.1002/aenm.201901560

Potassium-ion batteries (KIBs) have attracted increasing attention for grid-scale energy storage due to the abundance of potassium resources, low cost, and competitive energy density. The key challenge for KIBs is to develop highperformance electrode materials. However, the exploration of high-capacity and ultrastable electrodes for KIBs remains challenging because of the sluggish diffusion kinetics of K+ ions during the charging/discharging processes. This study reports for the first time a facile ion-intercalation-mediated exfoliation method with Mg2+ cations and NO3anions as ion assistants for the fabrication of expanded few-layered ternary Ta2NiSe5 (EF-TNS) flakes with interlayer spacing up to 1.1 nm and abundant Se sites (NiSe4 tetrahedra/TaSe6 octahedra clusters) for superior potassium-ion storage. The EF-TNS deliver a high capacity of 315 mAh g–1, excellent rate capability (121 mAh g–1 at a current density of 1000 mA g–1), and ultrastable cycling performance (81.4% capacity retention after 1100 cycles). Detailed theoretical analysis via first-principles calculations and experimental results elucidate that K+ ions intercalate through the expanded interlayers effectively and prefer to transport along zigzag pathways in layered Ta2NiSe5. This work provides a new avenue for designing novel ternary intercalation/pseudocapacitance-type KIBs with high capacity, excellent rate capability, and superior long-term cycling performance.

层状过渡金属硫属化合物(TMDs)以类石墨烯的层状结构,潜在的高比容量和丰富的元素储量等特点,有望应用于碱金属(锂,钠,钾)可充电电池和超级电容器。层状过渡金属硫属化合物具有独特的物理和化学性质使其能够进行调整和增强碱金属离子的存储能力和电荷传输行为。近年来,二元的二维层状过渡金属硫属化合物MX2(M = V,Ti,Zr,Ta,Nb,Mo,W; X = S,Se,Te等)在锂电池和钠电池中得到了广泛的关注。与锂电池和钠电池相比,由于钾元素储量丰富(地壳中第七位储量丰富的元素,约占2.09%)和较低的氧化还原电位(-2.93 V),钾离子电池已经成为很具有吸引力的替代品,可以实现高能量密度,较低的生产成本并且提供更高的电压平台。但是,与锂离子或钠离子相比,钾离子半径(离子半径为1.4 Å)要远大于锂离子(0.76 Å)和钠离子(1.02 Å),这就导致缓慢的钾离子传输和较差的钾离子储存能力。到目前为止,只有少数二元层状过渡金属硫属化合物的正极材料(例如TiS2和TiSe2)和 负极材料(例如VSe2,ReS2,MoS2,VS2,MoSe2)用于钾离子电池。

最近,悉尼科技大学汪国秀课题组和浙江大学韩伟强课题组报道了一种三元二维硫属化合物Ta2NiSe5超薄材料用于高性能钾离子电池。该材料具有宽的层间距(~1.1 nm)和丰富的硒吸附(K+)位点(NiSe4四面体/ TaSe6八面体簇)。而且该材料具有的层状三元结构实现了钾离子电池的高容量,高倍率和超长循环寿命的电池性能。作者对此材料的钾离子扩散途径通过DFT计算进行了系统的研究。结合ULF拉曼光谱,非原位XRD,TOF-SIMS,非原位XPS,和DFT计算表明了钾离子的运输是可逆地沿着Zigzag路径传输,并且发现钾离子易吸附于悬挂的硒原子位点。这些结果清楚地表明该宽层间距的三元材料对钾离子具有强吸附能和低扩散势垒,从而可以实现高效率钾离子的吸附和嵌入。这项工作为设计具有宽层间距和丰富的表面氧化还原位点的高性能电极材料提供了有效的参考。该工作还对三元二维材料在钾离子储能应用方面具有很好的指导意义。相关论文以题为“Unlocking Few-Layered Ternary Chalcogenides for High-Performance Potassium-Ion Storage”发表在Advanced Energy Materials (DOI: 10.1002/aenm.201901560)上。