Highly reversible Zn anode with a practical areal capacity enabled by a sustainable electrolyte and superacid interfacial chemistry
Joule(2022)
Abstract
Aqueous zinc-metal batteries are plagued by poor Zn reversibility owing to zinc dendrite and layered double hydroxide (LDH) formation. Here, we introduce a novel additive—N,N-dimethylformamidium trifluoromethanesulfonate (DOTf)—in a low-cost aqueous electrolyte that can very effectively address these issues. The initial water-assisted dissociation of DOTf into triflic superacid creates a robust nanostructured solid-electrolyte interface (SEI)—revealed by operando spectroscopy and cryomicroscopy—which excludes water and enables dense Zn deposition. We demonstrate excellent Zn plating/stripping in a Zn||Cu asymmetric cell for more than 3,500 cycles. Furthermore, near 100% CE is realized at a combined high current density of 4 mA cm−2 and an areal capacity of 4 mAh cm−2 over long-term cycling. Zn||Zn0.25V2O5·nH2O full cells retain ∼83% of their capacity after 1,000 cycles with mass-limited Zn anodes. By restricting the depth of discharge, the cathodes exhibit less proton intercalation and LDH formation with an extended lifetime of 2,000 cycles.
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Key words
Zn-ion batteries,Zn anode,Superacid,SEIRAS,XPS,Zn metal batteries,cryo-TEM
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