History and Recent Progress in Redox Flow Battery Development and Implementation

Maria Skyllas-Kazacos School of Chemical Engineering University of New South Wales Sydney, NSW, AUSTRALIA

FLOW BATTERIES

• Two types: Redox Flow (fully soluble) and Hybrid metal-flow batteries that involve plating of metal such as zinc on negative electrode during charging

Fe/Cr Redox Flow Battery

• Fe/Cr initially developed by NASA in 1970s and 80s. • Abandoned due to technical problems. • Deeya Energy re-introduced Fe/Cr system around 2006 but changed to

vanadium electrolyte soon after and renamed Imergy. • EnerVault began to develop Fe/Cr based energy storage products with funding

from the US Department of Energy. • Enervault’s first battery installation in May 2014 on an almond farm in Turlock, California. Farm has 186KW of onsite solar to power irrigation system for almond trees • De-commisioned June 2015

http://www.energystorageexchange.org/projects/150

Flow Battery Technologies Undergoing Field Trials and Commercialisation

Zinc-Bromine Zinc-Iron

Source: http://www.zbbenergy.com/

http://www.energystorageexchange.org/projects/150

All-Iron 10 kW/60 kWh Stone Edge Farm Winery USA UNSW All-Vanadium

https://www.viznenergy.com/news/ www.redflow.com.au

• Uses vanadium solutions in both half-cells. • Cross-mixing of electrolytes across membrane does

not lead to contamination of electrolytes so solutions have indefinite life

• Replacement costs are low (only battery stacks need replacement at end of life).

• Long cycle life (> 100,000 cycles) • Capacity loss readily restored by remixing solutions • Fast (ms) response time even when pumps off. • Capacity increased simply by adding more solution. • Can be electrically and mechanically recharged (ie

Instant recharge possible by exchanging solutions) • Cost per kWh decreases as storage capacity

increases.

Vanadium Redox Flow Battery Technical Features and Benefits

G1 VRB Capital costs per kWh versus storage time

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700

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Storage time/h

$AU

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Series1

All-Vanadium Redox Battery • Uses vanadium solutions in both half-cells

• First practical VRFB demonstrated by Skyllas-Kazacos and co-workers at the University of NSW in 1984 and patented in 1986.

• Proposed to overcome cross-contamination problems of NASA’s Fe-Cr system.

• Extensive R&D effort at UNSW between 1984 and 2000, covering all aspects of cell materials, electrolyte characterisation and production, stack design, modelling, fabrication and testing, sensor and control system development etc.

• Early UNSW field trials in solar house in Thailand, electric golf cart and submarine applications.

• Projects funded by Australian national and state government bodies interested in energy storage for remote area power systems.

Early UNSW R&D Projects: Vanadium Electrolyte Production

Investigation of V2 O5: •chemical reduction •leaching •suspended powder electrolysis

From C. Menictas PhD thesis UNSW, 1993

"Vanadium salt dissolution process", M. Skyllas-Kazacos and R. McDermott, Patent Appl. No. PCT/AU88/00471.

Early UNSW R&D Projects: Graphite Felt Activation Studies

Investigation of thermal, chemical and electrochemical activation processes for graphite felt electrodes.

From B.T. Sun PhD thesis, UNSW, 1991

Early UNSW R&D Projects: Bipolar Electrode Development

Conducting plastic substrate- carbon filled PE/PP/rubber blends

End electrodes

Bipolar electrode

S.Zhong, PhD thesis UNSW, 1992 V. Haddadi-Asl PhD thesis, UNSW, 1995

Early UNSW R&D Projects: Membrane Screening and Modification 1. Wide range of commercial membranes screened for: •electrical conductivity •permeability •chemical stability in V(V) •water transfer behaviour

2. Developed membrane modification processes to reduce water transfer 3. Novel low cost composite membrane based on “Daramic” separator.

From T. Mohammadi PhD thesis UNSW, 1995

Early UNSW R&D Projects: Electrolyte Additive Development

• Wide range of organic and inorganic additives screened and evaluated to stabilise V electrolytes at high and low temperatures

• Phosphoric acid initially identified as stabilising agent for V(V) at elevated temperatures – currently used in “standard V-Sulphate” electrolytes in most commercial systems

• Further studies led to identification of following compounds:

1. "M. Kazacos and M.Skyllas-Kazacos, Prov. Patent Appl No PN2747, May, 1995, US Patent 6,143,443. 2. "M. Skyllas-Kazacos, International Patent Appl No. PCT/AU96/00268, May, 1996, US Patent 7078123

Early UNSW R&D Projects: SOC Monitoring

Conductivity vs SOC Absorbance vs SOC

Michael Kazacos MSc Thesis, UNSW 1889 S. Corcuera et al Eur. Chem. Bull. 2012, 1(12), 511-519

Early Cell and Stack Designs

First VFB flow cell: 1986

First VFB multi-cell: 1987

First 1 kW VFB stack: 1988

First 5 kW VFB stack: 1989

First field trial VFB stack (external manifold design): 1993

Early VRB Demonstration Projects at UNSW

Emergency Back-up Battery for Submarines (1995)

Vanadium Battery Powered Solar House in Thailand (1993)

UNSW vanadium battery powered golf-cart (1996)

Recent Commercial VRB Systems and Installations

1 MW/5 MWh VRB - Sumitomo - Japan

Gildemeister - Germany 300 kW/3.6 MW Prudent - California

5 MW/10 MWh Rongke Power - China

Sumitomo VFB Wind Energy Storage Demonstration

Tomomae wind farm on Hokkaido: – 30.6 MW rated output VFB demonstration system: - Sumitomo / J-Power - 4 MW / 6 MWh NEDO funding for optimisation of control system After 3 year operation more than 200,000 cycles completed

Sumitomo 60 MWh VRB in Hokkaido

30 MW/ 60 MWh VFB Location: Hokkaido, Japan Started: December 2015 Grid Use: - Suppress WT and PV output

fluctuations - Load Frequency control - Suppress long-period fluctuations - Over generartion measures - Hybrid operation of Long and Short

period fluctuations

Shibata et al, IFBF 2017, Manchester UK.

Sumitomo 8 MWh VRB in USA

Shibata et al, IFBF 2017, Manchester UK.

3 MW/ 8 MWh VFB Location: Miguel, CA, USA Grid use with following functions: - Frequency and Voltage Regulation - Capacity smoothing - Peak shaving and base loading - Mitigation for over generation - Starting date: March 2017

Sumitomo Containerised VFB Sumitomo recently started producing containerised systems for easy

installation and cost reduction

125 kW / 2 MWh VFB (4x4h containers) Location: Sumitomo Yokohama Workd, Japan Starting date: October 2016

250 kW/ 750 kWh VFB Location: Sumitomo Osaka Works Japan Starting date: July 2017

Shibata et al, IFBF 2017, Manchester UK.

Rongke Power VFB Manufacturing Plant in Dalian, China

Huamin Zhang, IFBF 2017, Manchester, UK

Dalian VFB - UET / Rongke Power 200 MW / 800 MWh VFB announced for China in May 2016 Battery arrays approved by China National Energy Administration will comprise ten (10X) 20 MW / 80 MWh Vanadium Flow Battery (VFB) systems deployed on the Dalian peninsula Construction began October 2016. After full commissioning, the VFB battery will be able to peak-shave approximately 8% of Dalian's expected load in 2020. In addition, battery will form additional load centre, which will enhance grid stabilization including securing power supply and providing black-start capabilities in event of emergency.

http://www.energystorageexchange.org/projects/2169

800 MWh Rongke Power Dalian Project

Rated Power: 200 MW Rated Capacity: 800 MWh AC efficiency > 70% Components: Battery: 500 kW/2 MWh x 400

Huamin Zhang, IFBF 2017, Manchester, UK

Rongke Power 2MW Containerised VRB

Huamin Zhang, IFBF 2017, Manchester, UK

VFB SYSTEM FOR UNSW TYREE BUILDING • $129.7 million grant awarded to AGL Energy and

First Solar under Solar Flagships Program in 2012 • $40.7 million to University of Queensland and

UNSW to conduct related research. • Part of UNSW funds for installation of 30 kW/ 120

kWh VFB unit in new Tyree Energy Technology Building at UNSW

• Installation of Gildemeister VFB completed June 2015

• VFB system used to store solar energy from PV array on roof of building, while also allowing research on different energy storage applications.

CellCube VFB Installation in UNSW Tyree Building

Connected to building grid and 120 kW rooftop PV array

Mixed Acid Electrolyte VFB

• Mixed acid electrolyte VFB developed by PNNL

• Employs V/H2SO4/HCl in both half-cells • Mixed acid electrolyte increases solubility of each of the V

ions allowing solutions up to 2.7 M vanadium • Mixed acid electrolyte offers greater temperature range (0 to

50 oC) • Greater temperature range reduces need for cooling or

heating system.

• Currently being commercialised by UniEnergy Technologies

30

UniEnergy Technologies in Washington State, USA, in strategic partnership with Rongke (China) for supply of VRB stacks from China to be used by UET together with their G3 mixed acid VRB electrolyte, power conditioning equipment and battery management unit to assemble their high energy density containerised systems in the USA

UniEnergy Technologies containerised VRB system. (Ref: http://www.uetechnologies.com/product.htm )

Implementation of Mixed Acid Electrolyte in UET System using Rongke Stacks

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COST REDUCTION Current focus for VFB technology is to further reduce cost. Two approaches: 1. Reduce component costs.

• Membrane is most expensive stack component and currently used membranes vary in price from $350 to $800 per square metre.

• New membranes/separators now developed with costs < $50 per square metre. Currently undergoing long-term testing

2. Increase power density

• Reduce cell resistance – mainly ohmic • Reduce anode-cathode spacing without increasing pressure drop • Researchers adopting fuel cell stack architectures employing

serpentine flow fields

Rongke high power density stack development

Huamin Zhang, IFBF 2017, Manchester, UK

ENHANCING ENERGY DENSITY

• The energy density of the G1 VFB is determined by the solubility of the V(II), V(III), V(IV) and V(V) ions in sulphuric acid at different temperatures.

• 2 M vanadium concentrations stable during continuous operation within 15 to 40 oC temperature range.

• 1.6 M vanadium solutions employed to extend operating temperature, but at expense of energy density

• PNNL mixed acid chemistries can increase the energy density by modifying supporting electrolyte composition to increase solubilities of all four vanadium ions over broader temperature range.

• New improved G1 using 3 M vanadium solutions with stabilising agents can be used at room temperature with continuous charge-discharge cycling.

2M 3M 4M 5M

2M 3M 4M 5M

2M

3M

4M

5M

Vanadium Ion Solubility

Vanadium Electrolyte Studies for the Vanadium Redox Battery – A Review. M. Skyllas-Kazacos*, L. Cao, M. Kazacos, N. Kausar and A. Mousa. ChemSusChem. Volume 9, Issue 13, July 7, 2016 Pages 1521–1543

Improved G1 VRB with supersaturated solutions and precipitation inhibitors

"Stabilised Electrolyte Solutions, Methods of Preparation Thereof and Redox Cells and Batteries Containing Stabilised Electrolyte Solutions" M. Kazacos and M.Skyllas-Kazacos, Prov. Patent Application No PN2747, May, 1995, Australian Patent No 696452, Dec 1998. US Patent 6,143,443. "High Energy Density Vanadium Electrolyte Solutions, Methods of Preparation Thereof and All-Vanadium Redox Cells and Batteries Containing High Energy Density Vanadium Electrolyte Solutions", M. Skyllas-Kazacos, International Patent Application No. PCT/AU96/00268, May, 1996, United States Patent 7078123

- PNNL’s H2SO4/HCl mixed acid electrolyte uses 2.2 - 2.7 M V solutions (compared with 1.6-2.0 M in G1 VRB) and offers increased energy density, but charging must be limited to lower SOCs to prevent Cl2 generation.

- Potential safety issue - Alternative is to enhance energy density of the UNSW sulphuric

acid-based system - In mid 1990s, Skyllas-Kazacos and co-workers patented use of

precipitation inhibitors to stabilise up to 4 M vanadium electrolytes concentrations

Improved UNSW G1 VRB with Additives

Solution Induction time (hour)

Degree of Precipitation

Blank 16 5 Ammonium Sulphate 34 2 Ammonium phosphate 46 1 Ammonium oxalate 16 5 Phosphoric acid 16 3 Potassium triphosphate 16 3 Sodium triphosphate 16 4 Sodium Pyrophosphate 16 3 Potassium Sulphate 16 4 Potassium persulphate 16 4 Sodium Sulfite 16 4 Boric acid 24 3 Tungstic acid No ppt Nil Sodium Tungstate No ppt Nil

Induction times and degree of precipitation for additives [V(II)] = 2.0 M, [total SO4-2] = 5.0 M, %additive = 1% (wt/wt), T = 5.0 oC.

The Effect of Additives on the Low Temperature Stability of the Vanadium Redox Flow Battery Negative Half-Cell Electrolyte. Asem Mousa and Maria Skyllas-Kazacos, ChemElectroChem, . Volume 2 Issue 11, 2015, pp. 1742 - 1751.

Improved G1 with Additives

Solution Induction time (day)

Degree of Precipitation

Blank 4 4 Ammonium Sulphate 38 1 Ammonium phosphate > 52 Nil Ammonium oxalate 10 3 Phosphoric acid 10 2 Potassium triphosphate 8 2 Sodium triphosphate 30 3 Sodium Pyrophosphate 30 4 Potassium Sulphate 10 3 Potassium persulphate 9 2 Sodium Sulfite 30 3 Boric acid 5 5 Tungstic acid > 52 Nil Sodium Tungstate > 52 Nil

Induction times and degree of precipitation for the inorganic additives [V(III)] = 2.0 M, [total SO4-2] = 6.5 M, %additive = 2% (wt/wt), T = 1.0 oC.

.

The Effect of Additives on the Low Temperature Stability of the Vanadium Redox Flow Battery Negative Half-Cell Electrolyte. Asem Mousa and Maria Skyllas-Kazacos, ChemElectroChem, . Volume 2 Issue 11, 2015, pp. 1742 - 1751.

Name of Additive Dosage (wt.%)

Amount of Precipitates / Solution Volume after 20 days as % SOC (%)

100 % SOC 90 % SOC 80 % SOC Blank -- 55 – 60 25 – 30 < 1

Ammonium Sulphate

2 28 – 30 5 – 6 0.5 3 40 – 42 21 – 23 1 – 1.5

Ammonium Phosphate

1 3 – 4 0.8 – 0.9 < 0.5 2 1 – 2 1 – 1.2 < 0.5

Potassium Phosphate (tribasic)

1 30 – 35 7 – 8 0.8 – 0.9

2 15 – 20 4 – 5 0.8 – 0.9

Sodium hexameta Phosphate 1 10 – 12 7 – 8 3 – 4 2 4 – 5 2 – 3 1 – 1.5

Phosphoric Acid 1 5 – 6 No ppt No ppt 2 10 -12 4 – 5 3 – 4

Sodium Pentapolyphosphate 2 7 – 8 5 – 6 1 – 1.5

Phosphoric Acid + NH4-Sulphate 1 + 2 4 – 5 1 – 1.5 No ppt.

Potassium Phosphate + Ammonium Sulphate

1 + 2 4 – 5 1.5 - 2 0.5 – 0.6

2 + 2 4 – 5 1.5 – 2 No ppt.

Qualitative Comparison of Amount of Precipitates after 20 days at 50 oC in 2.0 M V(V) / 5 M Total Sulphate Solution

"The Effect of Additives on the High Temperature Stability of the Vanadium Redox Flow Battery Positive Electrolytes." Nadeem Kausar, Asem Mousa and Maria Skylas-Kazacos, ChemElectroChem. Volume 3, February 2016 , Pages 276–282.

Additive Effect on Induction time for precipitation in 2 M V(V) / 5M Total Sulphate solution at various SOCs at 50 oC. AS = Ammonium sulphates, PP = Potassium Phosphate, PA = orthophosphoric acid, SHMP = Sodium hexameta phosphate, SPPP = Sodium pentapolyphosphate. Suffix numbers represent the wt.% of additive/V(V) solution wt. (Kausar, Mousa and Skyllas-Kazacos)

SOC%

A High Energy Density Vanadium Redox Flow Battery with 3 M Vanadium Electrolyte. Sarah Roe, Chris Menictas and Maria Skyllas-Kazacos, J. Electrochem Soc., Focus Special Issue. Published July 23, 2015.

Additive wt% Induction time

(days)

Amount precipitate at 22

Days (%) Blank - 3 20 SPPP 1 14 0.1

2 5 1 3 4 5

K3PO4 1 5 1 2 5 1 3 18 2

H3PO4 1 47 - 2 5 5 3 4 5

(NH4)2SO4 1 4 20 2 3 50 3 3 50

Effect of Additives on Thermal Stability of 3 M V(V) solutions in 5 M HSO4

-/H2SO4. Temperature = 30°

Improved UNSW G1 VFB with 3 M V Electrolyte and Additives

Right: Capacity vs Cycle Number for Vanadium Redox Flow Cell employing 3 M V in 5 M total sulfate electrolyte with 1 wt% H3PO4 + 2wt% Ammonium Sulfate Additives and Left: Electric golf cart filed test using 3 M V electrolyte in 1998

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0.5

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3.5

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acity

/ A

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Vanadium- Oxygen Redox Fuel Cell - The Vanadium-Oxygen Redox Fuel Cell (VOFC) concept initially proposed by Kaneko and co-workers in 1992 and first evaluated at UNSW by Menictas and Skyllas-Kazacos in 1997

- Positive half-cell electrolyte replaced with oxygen gas diffusion electrode – halving electrolyte volume.

- Recent development at University of Twente and at Fraunhofer Institute

-UNSW recently awarded grant from US Office of Naval Research to further develop technology.

-Using a 3 M V(II) electrolyte with oxygen electrode equivalent energy density as 6 M VRB electrolyte

- Challenges to develop efficient oxygen electrode and stable membrane electrode assemblies that do not delaminate or leak with extended operation UNSW 5-cell VOFC stack (1997)

Vanadium- Oxygen Redox Fuel Cell

0 200 400 600 800 1000

0.80

0.84

0.88

0.92

0.96

1.00

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1.08

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Time/s

5 mA cm-2

10 mA cm-2

50 mA cm-2

100 mA cm-2

Recent laboratory tests Oxygen electrode: Commercial Pt catalyst GDE (0.3 mg/cm2 PtC 40% on Sigracet 29 BC carbon paper) Electrode area: 10 cm2 MEA: Catalyst layer hot pressed onto VB1 membrane using 5% Nafion solution as a binder Project aims: - to develop non-noble metal

catalyst for O2 reduction reaction - Optimise negative electrolyte

composition to maximise energy density

Project funded by US Office of Naval Research Tests conducted by: Dr Mandar Risbud, UNSW Sydney

Comparison of VFB chemistries G1 Mixed Acid Improved G1 V/O

Electrolyte composition

V/Sulphate in both sides

V/H2SO4/HCl in both sides

V/Sulphate in both sides

Varied

Neg. couple V3+ / V2+ V3+ / V2+ V3+ / V2+ V3+ / V2+

Positive couple V(IV)/V(V) V(IV)/V(V) V(IV)/V(V) O2/H2O

Maximum V Concentration

1.5 – 2 M 2.0 – 2.7 M 2 – 3 M 3 - 4 M

Specific Energy (Wh/kg)

15-25 Wh/kg 25- 30 Wh/kg 25 - 40 Wh/kg 50-80 Wh/l

Energy density 20-30 Wh/l 30 – 40 Wh/l 30 - 50 Wh/l 60-100 Wh/l

Operating temp. range

10 – 40 oC 0 to 50oC 10 to 40oC 0 to 50oC

Positive overcharge reaction

Oxygen Chlorine Oxygen Oxygen

SUMMARY • Flow batteries currently receiving considerable attention for energy

storage applications requiring >2 hours storage capacity. • The vanadium redox flow battery developed at UNSW since 1984

now undergoing significant commercialisation around the world • Rapid expansion in R&D activities internationally since 2005. • New membranes and electrode materials helping to achieve

significant cost reduction • Improved cell architectures from fuel cell development enabling

considerable enhancement of power density, allowing both stack volume reduction and cost reduction

• Improvements in electrolyte chemistry significantly enhancing energy density and operating temperature ranges.

• New chemistries investigated for further cost reduction – eg organics, all-iron – however still at early development stage.

• V/O redox fuel cell system promises energy densities up to 100 Wh/l, but considerable R&D required before commercialisation

Thank You

Questions?