Page 44 - EngineerIt August 2021

SCIENCE IN SOUTH AFRICA

With the departure of the Zebra project from the CSIR in 1986, Anglo American’s
focus and commitment to the industrial development and commercialisation of high-
temperature sodium/metal chloride batteries, and the CSIR’s decision to withdraw from the
industrialisation process, control of the lithium battery patent portfolio that had been initiated
at the CSIR was released by Anglo American and fully vested in Technifin, a company
established by CSIR to replace SAIDCOR, 50% of which was owned by CSIR and 50% by
the Industrial Development Corporation (IDC) of South Africa.
By the late 1980s, despite the unsuccessful attempt by Moli Energy, Canada, to
commercialise a rechargeable lithium battery with a metallic lithium anode that resulted
in fire-related incidents, there were strong signals from the lithium battery industry in
Japan that significant progress was being made to overcome the safety limitations of the
Moli Energy cells. Moreover, it became apparent that LiMn2O4 spinel electrodes were
receiving considerable attention by Sony Corporation and Sanyo Electric Company. Michael Thackeray
Thackeray and his team, therefore, intensified their research to design and patent novel
manganese oxide electrode structures, which offered greater long-term prospects than
the relatively unstable and higher cost LiCoO2- based (and LiNiO2-based) electrode campus and did not foresee the impending
systems pioneered by Goodenough. The strategy, which ultimately proved successful, impact of lithium battery technology that was
was to target stabilised manganese oxides with one-dimensional tunnels for lithium- to follow during the consumer electronics
ion transport, layered manganese oxide structures that offered two-dimensional lithium boom in the 1990s. Thackeray, sensing a
diffusion, and spinel-related manganese-oxide structures with a three-dimensional bright future for lithium battery technology
interstitial space for lithium. and receiving an offer to continue his
In 1991, Sony Corporation introduced the first commercial, rechargeable lithium-ion materials-related lithium battery research at
cells into the market. In order to reduce the safety hazards of the lithium metal anode, Sony Argonne National Laboratory, left the CSIR
applied the same principle that had been used in the sodium/metal chloride Zebra cells, i.e. for the United States in January 1994. The
assemble the lithium-ion cells in the discharged state. battery group that remained at the CSIR
In this case, the lithium was initially contained within a LiCoO2 cathode structure in the continued to operate for another year before
same manner as sodium is contained in the NaCl structure of a discharged Zebra cathode. closing its operations.
Instead of plating metallic lithium at the anode during charge, Sony used carbon (typically The foundational research at the
graphite), as a host structure to accommodate the lithium, thereby significantly enhancing CSIR subsequently paved the way for
the safety of the cell. The reversible lithium insertion/extraction reaction that takes place the later design by Thackeray’s team
during operation of the Sony lithium-ion cell is represented as: LixC6 + Li1–xCoO2 ↔ C6 + at Argonne National Laboratory of high
LiCoO2 in which xmax is approximately 0.5. During charge and discharge of the cell, which capacity composite electrode structures,
occurs at approximately 4 V, the lithium ions shuttle between the anode and cathode host xLi2MnO3•(1–x)LiMO2, in which M
structures, hence the name ‘lithium-ion’ cell. A similar reaction occurs in cells with a LiMn2O4 is predominantly Mn and Ni. Lithium
spinel cathode: LixC6 + Li1–xMn2O4 ↔ C6 + LiMn2O4. Reaction also occurs at 4 V, making batteries containing Argonne’s patented
LiMn2O4 a particularly attractive alternative to the more expensive LiCoO2. materials are currently being licensed and
However, LiMn2O4 electrodes were observed to dissolve and lose electro-chemical commercialised worldwide, not only for
capacity (energy) during electro-chemical cycling, which precluded their widespread use in portable electronic devices but also for
lithium-ion cells. By slightly modifying the composition of the spinel electrode to increase the larger scale transportation applications.
Mn4+ content in the structure, for example, as in the lithium-rich spinels Li1+xMn2–xO4 After leaving the CSIR, Thackeray
(0 < x ≤ 0.33), Gummow, de Kock and Thackeray showed that it was possible to suppress continued to provide technical support as
solubility as well as severe structural distortions in the spinel electrode, leading to significantly a consultant to CSIR/Technifin to secure
improved electro-chemical performance. At about the same time, Ferg, Gummow, de Kock and defend important patents within
and Thackeray demonstrated that safe lithium-ion cells could be constructed by coupling the portfolio. The foundational research
a Li4Ti5O12 spinel anode with a stabilised Li1+xMn2–xO4 spinel cathode. In this case, conducted at CSIR in the 1980s, on both
the lithium ions shuttle between two metal oxide structures at 2.5 V. These inventions sodium and lithium battery technologies,
complemented the original Thackeray and Goodenough spinel patent, and they significantly was clearly years ahead of its time.
strengthened CSIR’s growing internationally-lodged patent portfolio on lithium battery Through his studies and understanding
electrode materials. of structure-electrochemical relationships,
The introduction of the first commercial lithium-ion batteries by Sony Corporation Thackeray has pioneered the discovery,
triggered a series of visits in 1992 and 1993 by Ora Safriel of Technifin and Thackeray to design, and development of new and
various battery companies in Japan, Europe and the United States in an attempt to gauge improved battery materials for industry,
interest in, and exploit, CSIR’s lithium battery patent portfolio. These visits heralded the start particularly lithium metal oxide electrode
of a successful licensing campaign, particularly with the major Japanese lithium battery structures for lithium-ion battery systems.
manufacturers. The first license was executed in 1995 and other followed, generating He is the author of over 200 scientific
significant royalty income for CSIR/Technifin over the next several years. In 1992, after papers and holds 60 patents. Six of
supporting lithium battery research for approximately ten years, CSIR management decided his scientific papers received more
to terminate its investment in this field, supposedly because of the lack of a lithium battery than 1000 citations. He also authored
industry in South Africa. a memoir, Running with Lithium —
They were unaware of the full significance of the research being undertaken on the CSIR Empowering the Earth. n

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