Abstract
Aqueous rechargeable zinc-ion batteries (ZIBs) have recently shined in energy storage and transmission, which are due to high safety and low cost. However, the extremely stubborn by-products in the Zn anode severely inhibited the Zn2+ adsorption/desorption and exacerbated the dendrite formation. Herein, we report a facile strategy to eliminate inert Zn4(OH)6SO4·xH2O for the improvement of ZIBs according to the coordination effect by employing ethylenediaminetetraacetic acid-diamine (EDTA-2Na) as a coordination additive in traditional electrolyte. Zn2+ is coordinated with the carboxyl group of the four acetyl carboxyl groups and the N in C–N bonds, forming a new chelating structure, and thus stubborn deposition will be dissolved in the electrolyte. As a result, the discharge capacity of 102 mAh g−1 in the ZnSO4/Li2SO4 with EDTA-2Na electrolyte at a current density of 4 C and a stable cycle life with a capacity of 90.3% after 150 cycles are achieved. It has been concluded that the coordination effect strategy provides a valuable idea for solving the defects of ZIBs.
Highlights
The huge advantages in energy density, cycle stability, and output voltage make lithium-ion batteries (LIBs) available and popular (Clément et al, 2020; Liu et al, 2021; Zhang et al, 2021), while frequent reports on fire and explosion of LIBs, due to the flammability of organic electrolytes, raised people’s concerns on their safety (Zhu et al, 2021; Xu and Jiang, 2021)
The aqueous electrolyte with 1 M ZnSO4 and 3 M Li2SO4 in water is employed as control
The peak at about 9.8o in the x-ray diffraction (XRD) (Figure 2B) spectrum confirms that the insulating layer is Zn4(OH)6SO4.5H2O (Jiao et al, 2021)
Summary
The huge advantages in energy density, cycle stability, and output voltage make lithium-ion batteries (LIBs) available and popular (Clément et al, 2020; Liu et al, 2021; Zhang et al, 2021), while frequent reports on fire and explosion of LIBs, due to the flammability of organic electrolytes, raised people’s concerns on their safety (Zhu et al, 2021; Xu and Jiang, 2021). ZIBs face a series of severe challenges especially for zinc anodes, including dendrite growth and related parasitic reactions caused by free water (such as HER and by-product) (Yang et al, 2020; Sun H et al, 2021). Many methods have been reported to improve the performance of ZIBs by inhibiting hydrogen evolution or dendrite in aqueous electrolytes and proved to be effective, such as electrolyte additives (Soundharrajan et al, 2020; Guo et al, 2021; Hao et al, 2021; Guan et al, 2022), artificial SEI layers (Hao et al, 2020; Di et al, 2021; Hong et al, 2021; Shin et al, 2021), and zinc anode. In the local alkaline environment caused by the hydrogen evolution, Zn electrode would be corroded by increased concentration of hydroxide ions to generate ionic-insulating Zn4SO4(OH)6·xH2O, which becomes the barrier for ion/ electron diffusion, such as Eqs 1, 2 (Cao Z et al, 2020)
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