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New Mechanism for the Reduction of Vanadyl Acetylacetonate to Vanadium Acetylacetonate for Room Temperature Flow Batteries
Author(s) -
Shamie Jack S.,
Liu Caihong,
Shaw Leon L.,
Sprenkle Vincent L.
Publication year - 2017
Publication title -
chemsuschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 2.412
H-Index - 157
eISSN - 1864-564X
pISSN - 1864-5631
DOI - 10.1002/cssc.201601126
Subject(s) - vanadium , redox , acetylacetone , chemistry , electron transfer , anode , flow battery , faraday efficiency , inorganic chemistry , electrolyte , electrode , photochemistry
Abstract In this study, a new mechanism for the reduction of vanadyl acetylacetonate, VO(acac) 2 , to vanadium acetylacetonate, V(acac) 3 , is introduced. V(acac) 3 has been studied for use in redox flow batteries (RFBs) for some time; however, contamination by moisture leads to the formation of VO(acac) 2 . In previous work, once this transformation occurs, it is no longer reversible because there is a requirement for extreme low potentials for the reduction to occur. Here, we propose that, in the presence of excess acetylacetone (Hacac) and free protons (H + ), the reduction can take place between 2.25 and 1.5 V versus Na/Na + via a one‐electron‐transfer reduction. This reduction can take place in situ during discharge in a novel hybrid Na‐based flow battery (HNFB) with a molten Na–Cs alloy as the anode. The in situ recovery of V(acac) 3 during discharge is shown to allow the Coulombic efficiency of the HNFB to be ≈100 % with little or no capacity decay over cycles. In addition, utilizing two‐electron‐transfer redox reactions (i.e., V 3+ /V 4+ and V 2+ /V 3+ redox couples) per V ion to increase the energy density of RFBs becomes possible owing to the in situ recovery of V(acac) 3 during discharge. The concept of in situ recovery of material can lead to more advances in maintaining the cycle life of RFBs in the future.