Zinc iodine batteries have emerged as a promising battery system due to their cost-effective raw materials. However, there is an immediate need to improve the overall energy density of the battery, which is crucial to its competitiveness. In this study, a CuI cathode is employed alongside an aqueous deep eutectic solvent-based electrolyte formulated using low-cost triethylamine hydrochloride and ZnSO4·7H2O. Electrochemical analysis and XPS spectra reveal that the discharge product of CuI within this electrolyte comprises a mixture of Cu and I-, while the fully charged product consists of Cu2+ and I+, indicative of a four-electron transfer electrode reaction, significantly enhancing the discharge capacity. The assembled Zn-CuI battery demonstrates a notable discharge voltage of 1.7 V and a high discharge specific capacity of 518.1 mAh/g at a current density of 0.2 A/g. Furthermore, at a current density of 3.0 A/g, the battery exhibits an initial discharge specific capacity of 299.3 mAh/g and maintains a discharge specific capacity of 210.1 mAh/g after 200 cycles, showcasing a capacity retention rate of 70.2%.
随着全球对绿色储能装置需求的不断增长,水系锌离子电池逐渐受到学术界关注[1]。截至目前,基于锰氧化物[2]、钒基化合物[3]、普鲁士蓝类似物[4]、卤素[5]、有机化合物[6]等正极的水系锌离子电池已被相继开发并得到了深入研究。其中,锌-碘电池表现出优异的循环稳定性和性价比,被认为是具有发展潜力的水系锌离子电池之一[7]。然而,传统的水系Zn-I2电池基于I0 ↔ I-的单电子反应,表现出较低的放电电压(~1.2 V vs Zn2+/Zn)和容量,限制了其应用潜力[8]。
最近的研究表明,通过I2的进一步氧化得到更高价态的I+,可实现两电子转移的正极反应,从而获得额外的高放电电压平台(~1.7 V vs Zn2+/Zn)与相应的放电容量,显著提高了电池整体的能量密度[9]。然而,为了抑制I+在传统水系电解液中的水解反应,研究者往往利用高浓度氯盐[9]、引入有机溶剂[10]或设计特殊的含碘正极[11]等方式。这些手段增加了Zn-I2电池的成本与环境危害性。因此,探寻适用于高容量Zn-I+电池的低成本绿色电解液,并明晰其储能机理是一个亟待解决的问题。深共晶溶剂(deep eutectic solvent,DES)是利用氢键相互作用降低组分熔点形成的液体,作为一种低成本绿色溶剂,近年来被广泛应用于电化学储能[12]。深共晶溶剂利用氢键供体和氢键受体在室温下形成液体可以抑制水的活度,从而表现出优于水溶液的电化学窗口(0~2.5 V)[12]。与高浓度盐电解液和有机电解液相比,深共晶电解液的成本更低、环境友好性更高,更能发挥水系锌电池的优势[13]。三乙胺盐酸盐是一种常见配体,具有价格低、易于形成共晶的优点,是制备DES电解液的理想材料[14]。锌盐方面,使用低成本的七水硫酸锌有利于Zn2+的可逆沉积/溶解[15]。
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