Spontaneous Reduction and Adsorption of K3[Fe(CN)6] on Zn Anodes in Alkaline Electrolytes: Enabling a Long-Life Zn-Ni Battery
Yuanhao Shen,Qingyu Wang,Jie Liu,Cheng Zhong,Wenbin Hu.Spontaneous Reduction and Adsorption of K3[Fe(CN)6] on Zn Anodes in Alkaline Electrolytes: Enabling a Long-Life Zn-Ni Battery[J].Acta Physico-Chimica Sinica,2022,38(11):2204048-0.
1. Key Laboratory of Advanced Ceramics and Machining Technology (Ministry of Education), Tianjin Key Laboratory of Composite and Functional Materials, School of Materials Science and Engineering, Tianjin University, Tianjin 300072, China;2. Joint School of National University of Singapore and Tianjin University, International Campus of Tianjin University, Fuzhou 350207, China
Abstract:
In view of the continuously worsening environmental problems, fossil fuels will not be able to support the development of human life in the future. Hence, it is of great importance to work on the efficient utilization of cleaner energy resources. In this case, cheap, reliable, and eco-friendly grid-scale energy storage systems can play a key role in optimizing our energy usage. When compared with lithium-ion and lead-acid batteries, the excellent safety, environmental benignity, and low toxicity of aqueous Zn-based batteries make them competitive in the context of large-scale energy storage. Among the various Zn-based batteries, due to a high open-circuit voltage and excellent rate performance, Zn-Ni batteries have great potential in practical applications. Nevertheless, the intrinsic obstacles associated with the use of Zn anodes in alkaline electrolytes, such as dendrite, shape change, passivation, and corrosion, limit their commercial application. Hence, we have focused our current efforts on inhibiting the corrosion and dissolution of Zn species. Based on a previous study from our research group, the failure of the Zn-Ni battery was caused by the shape change of the Zn anode, which stemmed from the dissolution of Zn and uneven current distribution on the anode. Therefore, for the current study, we selected K3Fe(CN)6] as an electrolyte additive that would help minimize the corrosion and dissolution of the Zn anode. In the alkaline electrolyte, Fe(CN)6]3– was reduced to Fe(CN)6]4– by the metallic Zn present in the Zn-Ni battery. Owing to its low solubility in the electrolyte, K4Fe(CN)6] adhered to the active Zn anode, thereby inhibiting the aggregation and corrosion of Zn. Ultimately, the shape change of the anode was effectively eliminated, which improved the cycling life of the Zn-Ni battery by more than three times (i.e., from 124 cycles to more than 423 cycles). As for capacity retention, the Zn-Ni battery with the pristine electrolyte only exhibited 40% capacity retention after 85 cycles, while the Zn-Ni battery with the modified electrolyte (i.e., containing K3Fe(CN)6]) showed 72% capacity retention. Moreover, unlike conventional organic additives that increase electrode polarization, the addition of K3Fe(CN)6] not only significantly reduced the charge-transfer resistance in a simplified three-electrode system, but also improved the discharge capacity and rate performance of the Zn-Ni battery. Importantly, considering that this strategy was easy to achieve and minimized additional costs, K3Fe(CN)6], as an electrolyte additive with almost no negative effect, has tremendous potential in commercial Zn-Ni batteries.
