Sulphur-impregnated flow cathode to enable high-energy-density lithium flow batteries

Abstract

Redox flow batteries are promising technologies for large-scale electricity storage, but have been suffering from low energy density and low volumetric capacity. Here we report a flow cathode that exploits highly concentrated sulphur-impregnated carbon composite, to achieve a catholyte volumetric capacity 294 Ah l À 1 with long cycle life (4100 cycles), high columbic efficiency (490%, 100 cycles) and high energy efficiency (480%, 100 cycles). The demonstrated catholyte volumetric capacity is five times higher than the all-vanadium flow batteries (60 Ah l À 1 ) and 3-6 times higher than the demonstrated lithium-polysulphide approaches (50-117 Ah l À 1 ). Pseudo-in situ impedance and microscopy characterizations reveal superior electrochemical and morphological reversibility of the sulphur redox reactions. Our approach of exploiting sulphur-impregnated carbon composite in the flow cathode creates effective interfaces between the insulating sulphur and conductive carbon-percolating network and offers a promising direction to develop high-energy-density flow batteries.

Redox‐Flow Batteries: From Metals to Organic Redox‐Active Materials

“…Chen et al. reported a non‐aqueous sulfur‐impregnated carbon composite dispersion as the catholyte and combined it with a Li (s) anode 111. This setup leads to an average discharging voltage of 2 V and an immense volumetric capacity of 294 Ah L −1 .…”

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

“…[ 29 ] We found that the LiI not only increases the reversible volumetric capacity of the catholyte but also improves the electrochemical utilization of insulating sulfur. We evaluated a number of com- Adding LiI increases the reversible volumetric capacity of the catholyte.…”

“…In conventional all-liquid RFBs [ 34,35 ] and semi-solid RFBs, [26][27][28][29] the liquid phase includes solvents, dissolved salts, and/or soluble active species. In the MRSSL approach, we employ bi-functional soluble active species that not only contribute reversible capacity but also support ion conduction as an electrolyte salt, to maximize the capacity contribution from the liquid phase.…”

“…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).…”

Advances in electrode materials for Li-based rechargeable batteries

“…[225][226][227][228] For the traditional Li-S batteries, the formation of soluble polysulde species leads to detrimental self-discharge. However, such attributes can be utilized in ow battery systems.…”