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SCIENCE IN SOUTH AFRICA

Questions at that time were: FeSx, LiAl/FeCl2 and Na/S cells that
• Would the ultimate answer to energy storage lie in high temperature sodium- or lithium- are assembled in the charged state with
based batteries; and highly reactive LiAl and Na negative
• if so, would the liquid-solid-liquid configuration of the Na/S battery be preferable to the electrodes (anodes), CSIR’s sodium-iron
solid-liquid-solid configuration of the LiAl/FeS2 system? chloride cells could be assembled in the
discharged state using a simple mixture of
Because molten sodium and sulphur are highly reactive and combine violently if the table salt (NaCl) and iron metal powders
ceramic ‘β-Al2O3’ solid electrolyte in Na/S cells ruptures, and because molten sulphur is in the positive electrode (cathode), thereby
highly corrosive, Coetzer proposed the idea of using the pores within zeolitic structures to circumventing the difficulty and hazards
immobilise and contain the sulphur in a solid electrode matrix, thereby enhancing safety and of handling LiAl alloy or metallic sodium.
minimising corrosion. This concept was first evaluated in high-temperature LiAl/LiCl,KCl/ Galloway also showed that the Na/NiCl2
zeolite-sulphur cells using Argonne’s cell configuration. This study prompted Coetzer to electrochemical couple offered a slightly
consider alternative electrodes for Argonne’s technology and his thinking moved away from higher cell voltage (2.58 V) and was more
FeS2 and zeolite-sulphur to iron chloride electrodes, the initial studies being conducted on stable than the Na/FeCl2 couple (2.35 V)
chlorinated iron carbides, ‘FexCCly’ and subsequently, simply iron dichloride, FeCl2. to electrochemical cycling, making it the
Meanwhile, Thackeray broadened the scope of the research by initiating an exploration preferred system. Despite the demise of
of less corrosive metal oxides as alternatives to iron sulphide and iron chloride electrodes CSIR’s Na/zeolite-sulphur technology, the
in high temperature lithium cells, notably those from the family of stable iron oxides such as name ‘Zebra’ persisted and is still in use to
Fe2O3 and Fe3O4. describe sodium-metal chloride batteries,
although the acronym was temporarily
Sodium batteries – the Zebra battery changed to represent ‘Zero Emission
The early battery work and the ideas being generated at CSIR did not go unnoticed. In 1976, Battery Research Activity’.
Coetzer elicited the interest of industry and, in particular, Roger Wedlake of De Beers who, Significant progress was made by
recognising the future potential of electric vehicles, persuaded senior management at De CSIR and Harwell in the early 1980s in
Beers and Anglo American Corporation to invest in CSIR’s battery initiatives, along with the demonstrating the feasibility of sodium/
South African Inventions Development Corporation (SAIDCOR) that was affiliated to the CSIR. metal chloride battery technology.
In 1977, a formal agreement between CSIR, SAIDCOR, De Beers and Anglo American to In 1982, recognising the need to
undertake high-temperature battery research and development (R&D) was signed. scale up the production and expedite the
Significant progress was made and within two years several key patents had been evaluation of Zebra batteries in electric
filed internationally; potential partners abroad were identified to help drive CSIR’s battery test vehicles, Anglo American acquired
technologies forward. facilities in Derby, UK, and established
In 1979, visits were made to Argonne National Laboratory USA, and to the Atomic the company Beta R&D to manufacture
Energy Research Establishment (AERE) at Harwell, UK, where the Li/FeSx and Na/S ‘β-Al2O3’ tubes, cells, and batteries under
technologies, respectively, were in advanced stages of development. the management of Jim Sudworth, a
Argonne declined the offer to collaborate, ostensibly because of the political pioneer of Na/S technology from British
sensitivities in South Africa at the time. On the other hand, Ron Dell and Roger Bones Rail. By 1984, a multi-kWh Zebra battery
at Harwell, who had participated with British Rail in the development of Na/S batteries, had been built and demonstrated in an
sensing the technological and safety limitations of the Na/S system, welcomed the South electric vehicle. The Zebra project had
African delegation in anticipation of developing an alternative system, despite the political made excellent technological progress.
embargoes against the country at the time. Anglo American’s growing confidence
and investment in a project with huge
Huge advantage from the collaboration industrial potential and significance led to
A huge advantage of the early collaboration with AERE, Harwell, was that it gave CSIR their establishment of a new facility, Zebra
scientists immediate access to sodium-sulphur technology that enabled the evaluation of Power Systems, outside Pretoria, with
CSIR’s zeolite-sulphur and iron-chloride electrodes in the sophisticated sodium-sulphur Johan Coetzer as managing director.
battery configuration. The transfer of the project to industry
The political isolation of South Africa and international scientific and trade boycotts with most of the CSIR team joining the
against the country made it difficult for De Beers/Anglo American and particularly CSIR, a Anglo American operation gave CSIR
government-owned research institution, to operate openly with Harwell and Beta R&D. For the opportunity in 1986 to divest from the
this reason, the scientific collaboration was undertaken without public exposure. The project Zebra battery initiative and sell its share
was code-named ‘Zebra’ for ‘Zeolite Battery Research in Africa’. of investments, while maintaining its links
Because the zeolite-sulphur electrode was solid, a molten salt NaAlCl4 electrolyte (m.p. = with the project through contract research.
155 °C) was added to the electrode compartment to enable rapid Na+-ion diffusion between Thackeray decided to remain at the
the zeolite-sulphur and sodium electrodes via the solid ‘β-Al2O3’ electrolyte. The early results CSIR where he and Keith Adendorff
on Na/zeolite-sulphur cells were not promising, largely because the zeolite component continued to provide R&D support to Anglo
added considerable extra weight to the system, thereby yielding lower energy per unit mass American/Zebra Power Systems.
compared to the pure Na/S battery. Fortunately, the sodium-sulphur battery configuration was Over the next 15 years, in a joint
also suitable for evaluating the iron chloride electrodes being developed by Coetzer and his effort between Zebra Power Systems,
team for the Argonne-type high-temperature lithium battery. Harwell, Beta R&D and Daimler Benz,
It was Roy Galloway at the CSIR who first realised and demonstrated that, unlike LiAl/ Germany, outstanding progress was made

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