Aqueous Zn-ion batteries have tremendous potential to penetrate the energy storage market, as an alternative to Liion batteries, given the high volumetric capacity of Zn (5853 mAh cm −3 ), cost-effectiveness, earth abundance, and enhanced safety arising from using the aqueous electrolyte. However, its performance is stunted due to the poor rate capability and low cycle life originating from the degradation of cathode materials upon Zn 2+ insertion/deinsertion. Thanks to the stability of aromatic organic cathode materials with the required intermolecular spacing, pentacene-5,7,12,14-tetraone (PT) is encapsulated into mesoporous conductive carbon (CMK-3) additive, which ensures the electrode performs charge−discharge at rates as high as 20 A g PT −1 (63C) with ∼ 46% capacity retention. Such rates are common for supercapacitors; therefore, this work is of significance because an excellent faradic behavior is obtained due to the chemical robustness of the cell. Further, the PT/CMK-3 composite electrode exhibited outstanding cycling stability up to 5000 cycles with more than 95% capacity retention at 2.5 A g PT −1. To enhance the potential and thereby cell voltage and energy density, sulfur (S) was introduced to the PT skeleton to obtain dibenzo[b,i]thianthrene-5,7,12,14-tetraone (SPT).
Prospective high reduction potential cathode material has been proposed that can be used in non-aqueous redox flow battery application. New class of material, 3,6-dibromo-9-(p-tolyl)-9H-carbazole (3) incorporating carbazole core, showing a...
Aqueous organic redox flow batteries (AORFBs) hold great
promise
in the storage of fluctuating renewable energy output for later use
when there is a demand for electricity. Anthrarufin (AN), reported
earlier as an anolyte material for the AORFB application, offered
limited energy density due to its poor solubility. Here, we present
a derivative of AN, 1,5-dihydroxy-9,10-dioxo-9,10-dihydroanthracene-2,6-disulfonic
acid (DSAN) as an anolyte to improve the energy density of the AORFB.
Sulfonic acid functional groups were introduced to hike the solubility
of DSAN in an alkaline medium. DSAN is soluble up to 110 mM in 0.4
M KOH and offers a theoretical capacity of 5.9 A h L–1, which is more than twice that of AN. Cyclic voltammetry studies
reveal the quasi-reversible nature of DSAN with the redox potential
centered at around −0.64 V versus Ag/AgCl. However, upon cycling,
the cell enters into capacity imbalance mainly due to DSAN reacting
with water in the presence of carbon felt producing H2.
This parasitic reaction makes catholyte the capacity-limiting side.
Hence, an in situ electrolysis route is introduced to restore the
capacity of the battery in the event of capacity decay. In addition,
the use of d-fructose as an additive in the anolyte compartment
increases the overpotential for H2 evolution and minimizes
capacity fading. Hence, we believe that the work is relevant as it
addresses a much bigger problem of parasitic reactions in an alkaline
medium and benefits a broader spectrum of work.
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