Zinc sulfide (ZnS), one of the main ingredients of zinc ore and emerging materials, partly processes environmental risk. Deep eutectic solvents (DESs) are green solvents to efficiently separate metals with less emission. In this study, a novel route for direct electroseparation of Zn from ZnS in eco-friendly choline chloride-urea DES with the addition of malonic acid (MA) is studied for the first time. The role of MA and the reduction behavior of Zn(II) are systematically analyzed by cyclic voltammetry. The reduction of Zn(II) is quasi-reversible and follows one-step two-electron transfer process. Pure Zn with nanostructure is obtained with the current efficiency of 86.5 % and energy consumption of 2621.8 kW·h·t −1 at the optimized parameters of 10 mA·cm −2 , 353 K and 100 mM·L -1 ZnS. Mechanisms analyses indicate that in the presence of 60 mM·L -1 MA, besides [ZnCl − 3 ] - and [ZnCl − 5 ] 3- , some ZnS are dissolved to form stable [Zn(MA) 2- Cl − 2 ] 4- , [Zn(MA) 2- Cl - ] 3- and other MA based ligands, which causes a higher Zn ion solubility of 0.13 mol·L -1 and may promote the subsequent electroseparation of ZnS. Results from this study are expected to propose a simplified route to directly separate Zn from ZnS without oxidation pretreatment to achieve hazardous waste minimization.
Kewei Shu,Wenjuan Li,Yi Zhang,Yan Zong,Huilan Li,Yu Wang,Zixiong Sun
Flexible, miniature, and lightweight supercapacitor is ideal power source for next-generation portable and wearable electronics. However, their widespread application is limited by a critical drawback, self-discharge, which leads to energy loss during idle periods. To this end, a polyvinylidene fluoride (PVDF)-based nanofiber separator with piezoelectric properties that can effectively suppress self-discharge in supercapacitors, was prepared via electrospinning. By incorporating hydrophilic cellulose acetate (CA) and reduced graphene oxide (rGO) into the PVDF matrix, both the electrolyte affinity and piezoelectric output of the separator are significantly enhanced. The resulting rGO/CA/PVDF composite membrane exhibits outstanding mechanical flexibility, high porosity, excellent electrolyte uptake, making it highly suitable separator for flexible supercapacitor. Supercapacitors equipped with such separator exhibit superior electrochemical performance with a specific capacitance of 178.2 F/g at 10 A/g. Notably, an impressive capacitance retention of 79 % was achieved after 24 h of self-discharge test. The reduction in self-discharge is primarily due to the limited diffusion of electrolyte ions, induced by the polarized rGO/CA/PVDF composite separator endowed with improved piezoelectric characteristics. This work highlights the potential of piezoelectric separators as an effective strategy for long-term energy retention, and offers new insights into the rational design of functional separators with self-discharge mitigation capabilities.
Xuan Li,Fan Chen,Yuhuan Ye,Chenyu Wang,Guoli Ding,Yilin Zhang,Xiquan Xiao,Lei Li,Zhi-Guang Guo,Li-Chuan Jia,Jun Lei,Gan-Ji Zhong,Hongli Yang,Shengyang Zhou,Zhong-Ming Li
The aqueous zinc-ion batteries (AZIBs) are emerging as highly promising electrochemical energy storage solutions, owing to their advantages in safety and cost-effectiveness. However, the poor reversibility of zinc metal anode in aqueous electrolytes is the main bottleneck limiting their practical application. In this study, an easily fabricated mesoporous ferroelectric separator designed to significantly enhance the reversibility of zinc anode in aqueous electrolytes is introduced. The ferroelectric fields generated by this separator induce a uniform distribution of hydrated zinc ions between the inner Helmholtz plane (IHP) on the zinc surface and the bulk electrolyte, which in turn reduces the reactivity of parasitic reactions, such as hydrogen evolution and hydroxide formation. Meanwhile, the reduction of zinc reactivity, coupled with an increased zinc ion diffusion barrier, benefits planar zinc plating with minimal dendrite formation. Experimental evidence demonstrates that the zinc anode, equipped with the ferroelectric separator, achieves high reversibility in a standard 2 m ZnSO 4 aqueous electrolyte, with stable stripping/plating observed over 4000 cycles at various current densities. This study thus presents a novel separator for AZIBs that effectively mitigates parasitic reactions and dendrite growth by regulating the IHP structure, which offers a practical and low-cost pathway toward the actual application of AZIBs.
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