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Song Y, Yan H, Hao H, Liu Z, Yan C, Tang A. Simultaneous Regulation of Solvation Shell and Oriented Deposition toward a Highly Reversible Fe Anode for All-Iron Flow Batteries. SMALL (WEINHEIM AN DER BERGSTRASSE, GERMANY) 2022; 18:e2204356. [PMID: 36310140 DOI: 10.1002/smll.202204356] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/14/2022] [Revised: 09/17/2022] [Indexed: 06/16/2023]
Abstract
Developing low-cost all-iron hybrid redox flow batteries (RFBs) presents a practical alternative to the high-cost all-vanadium RFBs and is deemed vital for grid-scale energy storage applications. However, the intrinsically poor Fe anode reversibility associated with the deposition and dissolution of metallic iron greatly limits the cycling performance and long-term stability of all-iron hybrid RFBs. Herein, a highly reversible and dendrite-free Fe anode is reported for all-iron RFBs through regulation of polar solvent dimethyl sulfoxide (DMSO) on FeCl2 anolyte, which simultaneously reshapes Fe2+ solvation structure and induces controllable oriented Fe deposition. Combining both experimental and theoretical analyses, the polar DMSO additives prove effective in replacing H2 O molecule from the primary solvation shell of Fe2+ cation via the Fe2+ -O (DMSO) bond and meanwhile induces a fine-grained Fe nucleation on the preferred Fe (110) plane, which are responsible for the minimized hydrogen evolution and dendrite-free Fe deposition that significantly enhance Fe anode reversibility. The all-iron RFB based on the proposed FeCl2 -DMSO anolyte demonstrates an excellent combination of peak power density of 134 mW cm-2 , high energy efficiency of 75% at 30 mA cm-2 , and high capacity retention of 98.6% over 200 cycles, which presents the best performance of all-iron RFBs among previously reported research.
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Affiliation(s)
- Yuxi Song
- Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
- School of Materials Science and Engineering, University of Science and Technology of China, Shenyang, 110016, China
| | - Hui Yan
- Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
- School of Materials Science and Engineering, University of Science and Technology of China, Shenyang, 110016, China
| | - Huanhuan Hao
- Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
- School of Materials Science and Engineering, University of Science and Technology of China, Shenyang, 110016, China
| | - Zihe Liu
- Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
- School of Materials Science and Engineering, University of Science and Technology of China, Shenyang, 110016, China
| | - Chuanwei Yan
- Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
| | - Ao Tang
- Institute of Metal Research, Chinese Academy of Sciences, Shenyang, 110016, China
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Luin U, Valant M. Electrolysis energy efficiency of highly concentrated FeCl2 solutions for power-to-solid energy storage technology. J Solid State Electrochem 2022. [DOI: 10.1007/s10008-022-05132-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
AbstractAn electrochemical cycle for the grid energy storage in the redox potential of Fe involves the electrolysis of a highly concentrated aqueous FeCl2 solution yielding solid iron deposits. For the high overall energy efficiency of the cycle, it is crucial to maximize the energy efficiency of the electrolysis process. Here we present a study of the influence of electrolysis parameters on the energy efficiency of such electrolysis, performed in an industrial-type electrolyzer. We studied the conductivity of the FeCl2 solution as a function of concentration and temperature and correlated it with the electrolysis energy efficiency. The deviation from the correlation indicated an important contribution from the conductivity of the ion-exchange membrane. Another important studied parameter was the applied current density. We quantitatively showed how the contribution of the resistance polarization increases with the current density, causing a decrease in overall energy efficiency. The highest energy efficiency of 89 ± 3% was achieved using 2.5 mol L−1 FeCl2 solution at 70 °C and a current density of 0.1 kA m−2. In terms of the energy input per Fe mass, this means 1.88 Wh g−1. The limiting energy input per mass of the Fe deposit was found to be 1.76 Wh g−1.
Graphical abstract
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