Non-aqueous Redox Flow Batteries with Nickel and Iron Tris(2, 2’-bipyridine) Complex Electrolytes
Journal
Electrochemical and Solid-State Letters
Date
2012.04.30
Abstract
A redox flow battery of tris(2,2’-bipyridine)nickel(II)tetrafluoroborate (Ni(Bpy)3(BF4)2) and tris(2,2’-bipyridine)iron(II)tetrafluoroborate (Fe(BPy)3(BF4)2)) in propylene carbonate electrolyte is investigated. With cyclic voltammetry, the redox current of one-electron related Fe(II)/Fe(III) and two-electron related Ni(II)/Ni(0) appears at 0.65 V and -1.66 V (vs.Ag/Ag+), respectively and their electrochemical behaviors are almost constant during 100 cycles without electrolyte decomposition. Their charge-discharge characteristics on carbon felt electrodes are evaluated with 0.4 M Fe(Bpy)3(BF4)2 and 0.2 M Ni(Bpy)3(BF4)2 which were adopted as catholyte and anolyte. Comparing with aqueous system, higher cell voltage of 2.25 V was achieved and initial coulombic and energy efficiencies were reached with 90.4％ and 81.8％.