The idea of flow batteries goes back to NASA research in the 1970s, but the honour of converting theory into practice using vanadium belongs to Maria Skyllas-Kazacos. Flow batteries are now an increasing part of utilities’ armoury for energy storage and grid balancing.

Maria Skyllas-Kazacos aka… Lady Vanadium

To Maria Skyllas-Kazacos goes the honour of turning the early idea of a flow battery — where energy is stored in an ion exchange between two pumped liquids separated by a membrane — into something practical. And something commercially possible too.

Maria was born in 1951 in the chaos of post-civil war Greece, but moved to Sydney aged three. A remarkable scientific aptitude led her to the University of New South Wales in an age when it was uncommon for girls to go to university. She graduated with a first class degree and the University Medal in Industrial Chemistry at the University of New South Wales in 1974. For a PhD she researched the electrochemistry of molten salts.

In 1978, PhD in hand — and with a prestigious CSIRO Postdoctoral Fellowship — she moved to John Broadhead’s battery group in Bell Telephone Laboratories at Murray Hill, New Jersey.

Maria Skyllas-Kazacos in the V-Fuel lab in 2008 with husband Michael and son George

Maria Skyllas-Kazacos in the V-Fuel lab in 2008 with husband Michael and son George

She gained valuable experience in lead acid batteries and identified a new ionic species that forms as an intermediate during the charge-discharge reactions at the positive electrode.

The result was her first single author paper published in the Journal of the Electrochemical Society that was to later earn her the Royal Australian Chemical Institute’s Bloom-Guttmann Prize for the best young author under 30.

Despite a permanent position at Bell Labs on offer, in 1980 she moved back to Australia after winning the prestigious Queen Elizabeth II fellowship. This enabled her to continue her research in liquid junction solar cells in the School of Physics at the University of New South Wales.

In 1982 Skyllas became a lecturer in the School of Chemical Engineering and Industrial Chemistry at the university.

Meanwhile, professor Bob Robins invited her to join a research project on lead acid batteries funded by a National Energy Research Development and Demonstration Council of Australia grant.

Then she had her eureka moment with vanadium.

Chlorides of vanadium were generated in 1830 by Nils Gabriel Sefström. He named the new element vanadium after the Germanic goddess of beauty and fertility, Vanadis.

The use of vanadium in batteries had been suggested earlier by NASA researchers and by others in 1978, but no one had previously used vanadium redox couples in a working flow battery. A reason for this was the low solubility of pentavalent vanadium compounds in acidic solutions that would limit the practical energy density of such a system.

The fact that vanadium exists in several oxidation states, however, made it an excellent candidate for a single element flow battery that might overcome the problem of cross contamination observed with the Fe/Cr battery by NASA researchers in the 1970s and 80s.

Maria began some preliminary electrochemical studies on vanadium electrolytes to confirm its viability. Her preliminary studies with VCl3 solutions in H2SO4 showed good reversibility for the V(II)/V(III) and V(IV)/V(V) couples. However, further research was needed to optimize the solution chemistry to achieve a practical system.

When new funding arrived, Maria set out to explore the possibility of producing concentrated V(V) solutions by oxidizing 2M VOSO4 (Vanadyl sulphate), a much more soluble form of vanadium. Together with newly appointed research fellow Miron Rychcik, a 2M vanadium electrolyte was produced and tested, the results giving rise to the filing of the first all-vanadium redox flow battery patent in 1986.

This was the start of a 25-year programme that continues to this day. During the early years, development efforts were hampered by the lack of suitable off-the-shelf membranes and other cell components. In particular the use of VOSO4 for electrolyte production was found to be uneconomical from the outset.

One of the first tasks was to develop a process that would allow the use of the much cheaper V2O5 compound for electrolyte production ($5/ kg compared with more than $400/kg for VOSO4).

Her pioneering work meant she had to take charge of tasks such as producing electrolytes, novel plastic electrodes, and new modified membranes, as well as developing mathematical models and designs for battery technology and components, through to prototype testing and manufacturing trials in conjunction with industrial licences.

She became a senior lecturer at the university in 1986, associate professor in 1988 and professor in 1993. In 1987, a small feature on her battery in the university magazine attracted the interest of the local media in Australia. Almost over night, the vanadium redox flow (VRF) battery was featured in newspaper articles around the world.

In the wake of the media attention, Australian vanadium mining company Agnew Clough acquired an exclusive international licence to the VRF battery technology that led to three years of industrial funding to further develop the battery technology at the University of New South Wales.

But financial problems in the company led to the return of the technology to the University in 1991. Two years later, construction firm Thai Gypsum Products was granted a licence to the technology for south-east Asia.

Around the same time, Kashima- Kita Electric Power Corporation, a subsidiary of Mitsubishi Chemical Corporation, was drawn to the technology as a way to use vanadium waste extracted from power station soot.

This led to the granting of a licence to Kashima-Kita Electric Power Corporation and Mitsubishi Chemicals in 1993 that was followed by a five year R&D collaboration programme between the Japanese companies and the University of New South Wales research team, leading to further advances in stack design, improved materials and control systems.

Maria continued at the university and since 1993 has been professor at the School of Chemical Engineering and industrial chemistry director of the Centre for Electrochemical and Minerals Processing, which she founded.

From 1993 a number of field trials of the vanadium battery were undertaken both by UNSW and the university’s licensees in Thailand and Japan. As part of the R&D collaboration programmes with the licensees, regular trips between Sydney, Bangkok and Japan maintained a close relationship that culminated in several field trials, the first of which was the installation of a 5kW/15kWh battery in the first vanadium-powered solar demonstration house just outside of Bangkok.

To demonstrate the vanadium battery in a mobile application, a 36V prototype was installed in an electric golf cart at UNSW in 1994, where it was subjected to more than two and a half years of off-road testing by the development team. A new improved 3M vanadium had been undergoing bench-testing since late 1997 and was subsequently evaluated in the golf cart battery.

Preliminary results were promising, but further long-term testing would still be needed before a practical 3M vanadium electrolyte with energy density of more than 35Wh/kg would be available for commercial application.

Further research into air regeneration of the positive electrolyte was also explored as a means of doubling this to more than 70 kW/kg.

In 1998, however, the vanadium battery patents were sold by the University of New South Wales to the Australian listed company Pinnacle VRB, but rather than speeding up the commercial development of the battery, corporate restructurings and take-overs followed that ended with the patents being acquired by the Canadian company VRB Power and later Prudent Energy in China, with no further involvement of the UNSW team in its commercialization.

In the meantime, however, Maria was keen to explore new electrolytes for a high energy density vanadium redox flow battery and in 2001, filed the first patent on a new vanadium polyhalide flow battery that led to the second generation vanadium bromide flow battery with almost double the energy density of the original vanadium sulphate system.

The technology was licensed to the Australian company V-Fuel, however difficulties in attracting investment income in Australia saw the company folding in 2010 with the patent rights returned to the University. Further development of the G2 V/Br is continuing as part of an R&D collaboration between UNSW and Nanyang Technological University in Singapore and progress has been made with new low-cost bromine complexing agents and membranes.

Maria Skyllas-Kazacos’s contribution to the development of flow batteries is widely recognized.

More than 20 medium to large-scale VRB systems have been installed by Sumitomo Electric Industries in Japan, US, Europe and Australia for the storage of wind and solar energy and for load levelling at power stations and back-up power.

Skyllas-Kazacos has more than 250 publications including more than 40 patents and patent applications to her name. She is professor emeritus at the University of New South Wales.