Catalyzing zinc-ion intercalation in hydrated vanadates for aqueous zinc-ion batteries
Catalyzing zinc-ion intercalation in hydrated vanadates for aqueous zinc-ion batteries
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DOI：
10.1039/d0ta01468k
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发表时间：
2020-04-28
影响因子：
11.9
通讯作者：
Cao, Guozhong
中科院分区：
文献类型：
--
作者：
Liu, Chaofeng;Tian, Meng;Cao, Guozhong
由于水基锌离子电池中V离子的价态从5+变化到3+，水合五氧化二钒(VOH)可以提供高达400 mA h g(-1)的重量容量。二价过渡金属阳离子的引入已被证明克服了结构不稳定、动力学缓慢、容量快速退化和严重极化的问题。目前的研究表明，过渡金属阳离子的催化作用可能是显著改善电化学性能和电池性能的关键，因为在各自的样品中，铜-氧键的共价性较高，为55%，而镁-氧键的共价性为32%。铜(II)预嵌VOH(CuVOH)具有显著增强的嵌入存储容量、较高的放电电压、较大的输运性能和较小的极化，而VOH和镁(II)预嵌VOH(MgVOH)表现出相似的电化学性质和性能，表明镁离子的加入对电池性能的影响很小或没有影响。例如，CuVOH的氧化还原电压间隙为0.02V，远小于VOH的0.25V和MgVOH的0.27V。CuVOH的交换电流密度为0.23Ag(-1)，而VOH和MgVOH的交换电流密度分别为0.20Ag(-1)和0.19Ag(-1)。CuVOH的锌离子存储容量为379 mA h g(-1)，高于0.5A g(-1)时的349 mA h g(-1)和337 mA h g(-1)。CuVOH的能效为72%，优于VOH的53%和MgVOH的55%。这些结果表明，预先插入的铜(II)离子对锌离子的插层反应起着关键的催化作用，而镁(II)离子对锌离子的插层反应没有明显的催化作用。
Hydrated vanadium pentoxide (VOH) can deliver a gravimetric capacity as high as 400 mA h g(-1) owing to the variable valence states of the V cation from 5+ to 3+ in an aqueous zinc ion battery. The incorporation of divalent transition metal cations has been demonstrated to overcome the structural instability, sluggish kinetics, fast capacity degradation, and serious polarization. The current study reveals that the catalytic effects of transition metal cations are probably the key to the significantly improved electrochemical properties and battery performance because of the higher covalent character of 55% in the Cu-O bond in comparison with 32% in the Mg-O bond in the respective samples. Cu(ii) pre-inserted VOH (CuVOH) possesses a significantly enhanced intercalation storage capacity, an increased discharge voltage, great transport properties, and reduced polarization, while both VOH and Mg(ii) pre-inserted VOH (MgVOH) demonstrate similar electrochemical properties and performances, indicating that the incorporation of Mg cations has little or no impact. For example, CuVOH has a redox voltage gap of 0.02 V, much smaller than 0.25 V for VOH and 0.27 V for MgVOH. CuVOH shows an enhanced exchange current density of 0.23 A g(-1), compared to 0.20 A g(-1) for VOH and 0.19 A g(-1) for MgVOH. CuVOH delivers a zinc ion storage capacity of 379 mA h g(-1), higher than 349 mA h g(-1) for MgVOH and 337 mA h g(-1) for VOH at 0.5 A g(-1). CuVOH shows an energy efficiency of 72%, superior to 53% for VOH and 55% for MgVOH. All of the results suggest that pre-inserted Cu(ii) cations played a critical role in catalyzing the zinc ion intercalation reaction, while the Mg(ii) cations did not exert a detectable catalytic effect.