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SCIENCE IN SOUTH AFRICA

in optimising Zebra battery technology and demonstrating it in electric vehicles in all-weather One year before Thackeray’s visit,
climates. Of note was that the technology was successfully used in Mercedes buses to Goodenough had published (and patented)
transport athletes within the Olympic Village at the 1992 Games in Barcelona. the concept of using a layered LiCoO2
Sadly, after 20 years of technological innovation and success, both Anglo American and electrode structure for lithium cells; this
Daimler Benz decided to withdraw from further development of the Zebra battery, evidently material was later to become the cathode
because of the lack of a worldwide electric vehicle infrastructure that would sustain the of choice for the first generation of
technology. This divestment came a few years after the United States Department of Energy rechargeable lithium-ion battery products.
had also decided to terminate its high-temperature battery R&D initiatives for transportation. In the autumn of 1981, Thackeray
The decision by Anglo American and Daimler Benz to terminate their development of arrived at Oxford with several spinel
the Zebra battery also coincided with the demise of GM’s all-electric vehicle, EV1, which samples in his possession, including
occupied an unprofitable niche of the car market; by 1999, only 800 EV1 units had been magnetite (Fe3O4) and hausmannite
leased over four years with production costs of $1 billion. In the same year the entire Zebra (Mn3O4), where he immediately launched
operation was sold to MES-DEA, Switzerland. an investigation of their chemical and
In 2007, Rolls-Royce Marine chose the Zebra battery as the propulsion source for the electrochemical reactions with lithium at
NATO rescue submarine. In the same year, General Electric acquired Beta R&D, which room temperature. Despite the robust,
enabled rapid advancement and the early production of Zebra-based ‘Durathon’ battery gem-like properties of the spinel structure
products. (that takes its name from the semi-
precious mineral ‘spinel’, MgAl2O4), and
Lithium Batteries to Goodenough’s surprise, Thackeray
Materials innovation and the exploitation of intellectual property demonstrated that it was possible to insert
During the early years of the Zebra project at CSIR in the late 1970s, Thackeray initiated lithium into both Fe3O4 and Mn3O4.
studies of high-temperature LiAl/ LiCl,KCl/iron oxide cells to evaluate their performance Subsequent structural refinements
against Argonne’s more corrosive LiAl/LiCl,KCl/iron sulphide system. In these studies, which undertaken together with Bill David, a post-
included the screening of a wide number of other metal oxides, it was observed that the family doctoral student in Goodenough’s group at
of iron oxides, notably Fe2O3 with a corundum-type structure and Fe3O4 with a spinel- the time, showed that the [Fe2]O4 – and
type structure, provided far superior electro-chemical performance than other metal oxide [Mn2]O4 framework of the Fe[Fe2]O4 and
electrodes. Another observation was that when the lithium cells were continuously discharged Mn[Mn2]O4 spinel structures remained
and charged, an iron oxide structure with spinel-type features was obtained in fully charged intact during lithium insertion, resulting in
cells, irrespective of the structure-type of the parent electrode material. The voltage of these the rock salt products LiFe[Fe2]O4 and
high-temperature LiAl/iron oxide cells was too low, with most of the discharge occurring at LiMn[Mn2]O4, respectively.
about 0.9 V, to be competitive with the Na/S (2.1 V) and LiAl/FeSx (1.7 V) systems and, During the electrochemical reactions,
therefore, received relatively low priority in CSIR’s battery research programmes. the Fe and Mn ions within the interstitial
By 1980, primary (i.e. non-rechargeable) lithium batteries that operated at room space of the spinel framework were
temperature were beginning to enter the market in consumer products such as calculators, displaced into neighbouring crystallographic
watches and cameras; primary lithium batteries were also under development for military sites to make room for the incoming lithium
applications. Thackeray took the opportunity, with financial support from CSIR, SAIDCOR ions. These findings and the recognition by
and Anglo American, to travel to the Inorganic Chemistry Laboratory at Oxford University, Goodenough (who was well acquainted with
UK, where high-level lithium battery research was being undertaken by Professor John spinel structures from his pioneering work
Goodenough, a world-renowned authority in the field, to learn the trade and to evaluate the in the 1950s on their magnetic properties)
room-temperature electrochemical behaviour of the most promising metal oxide electrode that the [Fe2]O4 and [Mn2]O4 spinel
materials that had been identified at the CSIR in high-temperature cells. framework provided a three-dimensional
interstitial space for Li+-ion diffusion had
immediate implications – led rapidly to the
investigation of the lithium spinel Li[Mn2]O4
system, in which lithium could diffuse more
rapidly within the structure than in Fe3O4
and Mn3O4. Because the discoveries
at Oxford University had originated from
CSIR’s ideas and spinel battery projects,
Goodenough graciously agreed to give
the SAIDCOR title to the international
patent that was filed on the use of the [M2]
O4 spinel framework (M=metal ions) as
an insertion electrode for lithium cells and
batteries. Thackeray returned to the CSIR
at the end of 1982 and established a team
to expand CSIR’s research activities on
the electrochemical properties of transition
metal oxide electrodes in room temperature
lithium cells.

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