A High‐Energy‐Density Multiple Redox Semi‐Solid‐Liquid Flow Battery

Abstract

well as safety concerns if/when crossover occurs.Non-aqueous Li-based fl ow batteries utilizing organic redox compounds (e.g., ferrocene-based redox, [ 24,25 ] 2,2,6,6-tetramethylpiperidine-1-oxyl, (TEMPO)-based) [ 8,11 ] as catholytes have been shown an effective approach to increase the power density, [ 24,25 ] cycle life, [ 24,25 ] and energy density of the RFBs. [ 1,6,7,9,24,25 ] However, the low solubility of organic redox compounds has limited further improvement in energy density. Alternatively, a non-aqueous Libased semi-solid fl ow battery was proposed by Duduta et al. [ 26 ] In this concept, insoluble active materials (lithium cobalt oxide (LiCoO 2 ), [ 26 ] lithium iron phosphate (LiFePO 4 ), [ 27 ] silicon [ 28 ] ) are mixed with conducting carbon (e.g. Ketjenblack (KB)) and Li + ion supporting electrolyte to form a suspension, which permits catholyte/anolyte concentration beyond solubility limit and shows much higher achieved volumetric capacity. Along this concept, we have recently reported a sulfur/carbon (S/C) composite semi-solid fl ow battery achieving superior volumetric capacity (294 Ah L −1 catholyte ). [ 29 ] Another important emerging direction in the fi eld is applying redox reactions to mediate and facilitate intercalation or conversion reactions of energy storage materials. [30][31][32] Applying this concept, Jia et al. [ 33 ] have recently demonstrated a high-energy density all redox fl ow lithium battery reaching tank energy density ≈500 Wh L −1 (50% porosity).In this work, we propose a new concept of multiple redox semi-solid-liquid (MRSSL) fl ow battery, which takes advantage of both highly soluble active materials in the liquid phase and high-capacity active materials in the solid phase, to form a biphase MRSSL catholyte. Here, we used liquid LiI electrolyte and solid S/C composite as an example to demonstrate an LiI-S/C MRSSL catholyte, which achieved the highest catholyte volumetric capacity (550 Ah L −1 catholyte ) to date and superior energy density (580 Wh L −1 catholyte+lithium ) with high columbic effi ciency (>95%). We further show that the presence of LiI synergistically facilitates the electrochemical utilization and reduces the viscosity of the catholyte. A continuous fl ow battery system based on the LiI-S/C MRSSL catholyte is demonstrated and the infl uence of fl ow rate and current density on the battery performance will be discussed. The MRSSL concept provides wide-open opportunities for numerous combinations of solid and liquid active materials and offers a new direction for designing next-generation high-energy-density fl ow batteries.

Stable Performance of Aluminum‐Metal Battery by Incorporating Lithium‐Ion Chemistry

“…On another note, it has been recently revealed that cells adopting catholytes and Li metal anodes could suffer from severe self‐discharge because the reaction products at the cathodes tend to spontaneously react with Li metal. By contrast, the self‐discharge of the present Al−Li hybrid cell barely occurs, for not only are the carrier ions relatively unreactive toward the counter electrodes, but the Al metal in the anode and the FP in the cathode are also physically separated; the AlCl 4 − ‐Al 2 Cl 7 − redox couple does not react with LFP, and similarly, Li ions are inert with respect to the Al metal anode.…”

Evaluation of Hybrid Anode Usability in Lithium Polysulfide Flow Batteries

“…There are two main methods to construct a Li–S flow battery. One is to combine S or LiPS with conductive carbon to form a suspension ,,. As the catholyte is a suspension, the dissolution of S as LiPS is no longer an issue and the battery can be charged and discharged to the full potential of the Li–S battery chemistry.…”

“…The Cui group was the first to demonstrate a proof‐of‐concept semisolid LiPS battery prototype, and several variants by other groups have appeared since –. The all‐liquid flow battery was demonstrated by the Wang group using a dissolved LiPS catholyte .…”

Review Article: Flow battery systems with solid electroactive materials

“…Chen et al reported a catholyte containing solid sulfur/carbon composites and liquid lithium iodide (LiI) electrolyte, where the LiI serves as both a Li þ conductor and energy storage active material. 354 This design achieved a high energy density (580 W h L…”