An Energy‐Dense, Powerful, Robust Bipolar Zinc–Ferrocene Redox‐Flow Battery

Abstract

Zinc metal represents a low‐cost, high‐capacity anode material to develop energy‐dense aqueous redox‐flow batteries (RFB). However, the energy‐storage applications of traditional inorganic Zn halide flow batteries are primarily plagued by the material challenges of traditional halide cathode electrolytes (e.g., bromine), including corrosion, toxicity, and severe crossover. Herein, we report a bipolar zinc–ferrocene salt compound, zinc 1,1′‐bis(3‐sulfonatopropyl)ferrocene, Zn[Fc(SPr)2] (1.80 M solubility or 48.2 Ah L− charge storage capacity)—a robust, energy‐dense, bipolar redox‐active electrolyte material for RFBs. Zn[Fc(SPr)2]‐based redox‐flow batteries operated at high current densities of up to 200 mA cm−2 and delivered an energy efficiency of up to 81.5 % and a power density of up to 270.5 mW cm−2. A Zn[Fc(SPr)2] flow battery demonstrated an energy density of 20.2 Wh L−1 and displayed nearly 100 % capacity retention for 2000 cycles (1284 h or 53.5 days).

Engineering a self-adaptive electric double layer on both electrodes for high-performance zinc metal batteries

“…According to previous studies, the introduction of ImS breaks the strong hydrogen bonds before the water cluster, which indicates the interaction between ImS and water molecules. 45…”

“…Furthermore, previous studies proved that the ZnS component probably originates from the reduction of SO 4 . 2–53…”

“…According to previous studies, the introduction of ImS breaks the strong hydrogen bonds before the water cluster, which indicates the interaction between ImS and water molecules. 45 Liquid-state nuclear magnetic resonance (NMR) spectroscopy was employed to further demonstrate the interaction among Zn 2+ , ImS, and water in the ImS/ZSO electrolytes. As shown in Fig.…”

Redox Flow Batteries: Electrolyte Chemistries Unlock the Thermodynamic Limits

“…The low cost of Zn and rich knowledge in Zn‐based electrolyte chemistries make it competitive for large‐scale RFB applications [33–35] . However, the formation of Zn dendrites is common in aqueous electrodeposition, which may pierce the ion‐conducting membranes and cause short circuit [36] .…”

“…[2,32] The low cost of Zn and rich knowledge in Zn-based electrolyte chemistries make it competitive for large-scale RFB applications. [33][34][35] However, the formation of Zn dendrites is common in aqueous electrodeposition, which may pierce the ion-conducting membranes and cause short circuit. [36] Recently, the [Sn(OH) 6 ] 2À /Sn redox couple (À 0.92 V vs. SHE) in alkaline electrolyte has been reported, which showed merits of dendrite-free deposition and high solubility (2.25 M for K 2 Sn-(OH) 6 in 1 M KOH).…”