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Tonight the National Academy of Engineering celebrates the role in society of Materials Engineering. We four are delighted and honored to participate in this celebration, and we are grateful to all those who have contributed--intellectually, financially, and as colleagues--to our presence here.
The Li-ion battery illustrates the complex process of innovation in Materials Engineering and the importance of both the support of the individual investigator and the availability of open international communication between scientists.
In the early 1970s, there was a confluence of several events that led to the technology we are celebrating tonight: (1) the first energy crisis alerted the developed world to its vulnerability to dependence on imported oil; (2) the Three-Mile-Island incident helped to expose the limitations of nuclear energy; (3) explorations by Jean Rouxel in France and Robert Schöllhorn in Germany of the chemistry of reversible Li intercalation into layered compounds, particularly sulfides, led to the suggestion of a rechargeable Li battery having TiS2 as its cathode.
The Li/TiS2 battery was abruptly abandoned after incendiary cell failures, failures that resulted from internal short-circuits by dendrite growth from the metallic-lithium anode to the cathode after repeated charge/discharge cycling. My contribution was to realize that an oxide cathode could allow a higher voltage and use of a Li-free anode in the fabrication of a discharged cell. This realization led to the development of the LiCoO2 cathode in my laboratory at the University of Oxford. Quite independently, Rachid Yazami was exploring in Switzerland Li intercalation into graphite, a process he found did not result in dendrite formation providing the charging rate was not high enough to plate lithium on the surface of the graphite. In Japan, Akiro Yoshino, again quite independently, then understood he could assemble a rechargeable discharged cell with a Li-free graphite anode and a LiCoO2 cathode to create a safe Li-ion battery. Yoshino Nishi of the SONY Corporation, Japan, used this battery to develop the first wireless telephone. With a marketable product, the wireless revolution was born.
The batteries of the wireless revolution do not have to compete with the energy stored in fossil fuels. Today, the engineering challenge is the development of electrochemical devices that will enable electric vehicles and also the storage of electrical energy generated from wind and solar energy at a cost that is competitive with fossil fuels; this challenge is an urgent global priority for a sustainable modern society.