Microsoft PowerPoint - 2010-06-16_Non_Aqueous_Redox_Vienna_Fraunhofer_Michigan.ppt»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
NonAqueous Vanadium Redox Flow Batteries 1st International Flow Battery Forum (IFBF)
June 16th, 2010
Christian Doetsch, Sascha Berthold, Birgit Brosowski Fraunhofer Institute UMSICHT
Jens Tuebke, Jens Noack Fraunhofer Institute ICT
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
• Framework:  Cooperation between University of Michigan (United States) and Fraunhofer  Gesellschaft (Germany) established
• Project Partners: University of Michigan: Department of Chemical Engineering (Prof. Levi Thompson, Prof. Charles Monroe)
Fraunhofer Institute UMSICHT and ICT (Dr. Christian Doetsch, Dr. Jens Tuebke)
• Project Aim: Examination, developing and testing of materials and stack design for a  nonaqueous redox flow battery
Project Outline 1/2
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
•Main advantages of nonaqueous systems: Higher Voltage level No Hydrogen/oxygen production Higher energy densitiy
•Work plan: RedoxChemistry, materials, membranes: University of Michigan Prototype development: Fraunhofer ICT Scale up, test bench: Fraunhofer UMSICHT
• Time Frame: Start End of 2009 / Duration 24 months
Project Outline 2/2
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Singlemetal Redox Flow Batteries
• Aqueous allvanadium redox flow battery (RFB)
Performance depends on
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Existing RFBs mostly use aqueous electrolytes:
• Iron/chromium
• Bromine/polysulfide
• Zinc/bromine
Cell potential limited by water electrolysis (E° = 1.23 V)
ZBB Energy Corp, 500kWh ZnBr RFB
Commercial Redox Flow Battery Chemistry
Nonaqueous electrolytes enable higher cell potentials
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
NonAqueous Vanadium RFB
V(III)e(IV) V
Energy density dependent on:
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Equation of the solvent
[vanadiumactetylacetonate]              
Glassy carbon working electrode
[vanadylsulfat]
Glassy carbon working electrode
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 -1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
VIII/VIV
VII/VIII
2.2V
- 2
Potential/V vs.SHE -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0
-15
-10
-5
0
5
10
VIV/VV
VII/VIII
1.4V
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Progress: Redox Chemistry
• Presence of Cl ions (from  membrane manufacturing) produces  extra peak close to VIII/VIV redox  couple
-2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5 2.0 -1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
C ur
re nt
d en
si ty
/m A
cm 2
Potential/V vs. SHE -2.5 -2.0 -1.5 -1.0 -0.5 0.0 0.5 1.0 1.5
-10
-5
0
5
10
15
Potential/V vs. Ag/Ag+
• Peak circled in red corresponds to  oxidation of V(acac)3 to VO(acac)2  produced from active species in  presence of air
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Linear Sweep Voltammetry (LSV)
• Quasireversible Model
– Small reductant concentration 
– Microelectrode (Steady State)

• Diffusion Coefficient1
D = 1.8 x 105 ± 3.5 x 106 cm2/s 
(1)  Bard and Faulkner. Electrochemical Methods. 2001
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Linear Sweep Voltammetry: V(III) / V(IV) Redox Couple
Carbon Gold
Scan rate: 1 mV/s  Scan rate: 0.5 mV/s 
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Linear Sweep Voltammetry: V(III) / V(IV) Redox Couple
Platinum All
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Progress: Membrane diagnostics • Implementation of proposed onedimensional test cell
Critical system variables: liquid  solutions
membranes (or MEA)
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Progress: Membrane diagnostics • Charge/discharge with anionexchange membrane (Neosepta AHA) underway  Au electrodes, flowby mode, 0.1 M V(acac)3 [vanadiumactetylacetonate] and
0.5 M TEABF4/CH3CN [Tetraethylammoniumtetrafluoroborate / Acetonitrile]
• Charge current 0.4 mA, discharge –0.05 mA; Burnin complete after 3 cycles
• 85% Coulombic efficiency
-0.05
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.0
0.5
1.0
1.5
2.0
2.5
0.5
1.0
1.5
2.0
2.5
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Progress: Prototype development task
Redox Flow Test Cell – First Results
10 cm² active area Graphite felt (COS1006) Bipolar plate (Schunk GmbH, Germany) Microporous membrane (Scimat) 0.1 M V(Acac)3 0.05 M TEABF4 Acetonitrile
Rct = 1590 
Rs = 5 
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Progress: Prototype development task
Redox Flow Test Cell – Charge / Discharge
20 mA (2 mA/cm²) galvanostatic charge  up to 2 V, 2.2 V, 2.4 V, 2.6 V 5 min OCVMeasurement 5 mA (0.5 mA/cm²) galvanostatic discharge  down to 0.3 V
0 1 2 3 4 5
0,0
0,5
1,0
1,5
2,0
2,5
-0,01
0,00
0,01
0,02
0,03
0,04
0,05
0,06
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Progress: Scaleup Cell / Stack Design 
cell data (for a liquid, aqueous system)
number of cells 2
Voltage (charge)  
Current
»Non-Aqueous Vanadium Redox Flow Batteries« 1st International Flow Battery Forum (IFBF)
Scaleup and test bench Design and erecting a first test facility as a mobile test bench
• 15 kW power
• Electrolyte tank: 2 x 40 l 2 kWh
• Stack size up to 1 x 0.8 x 0.3 m 200 kg
• Charge 0 – 40 V 0 – 375 A
• Discharge < 40 V 0 – 440 A
• Flow rate 0.35 – 5 l/min