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Agrandir Original (png, 247k)

Baghdad battery, sketch of the three pieces

© Ironie

2The development of humanity has always been linked to that of materials. This premise is constantly being confirmed today, since emerging technology is still reliant on chemistry’s sometimes capricious ability to supply more efficient materials which are better suited to the additional constraints imposed on them.

3In this context, the “solid-state chemistry – energy” pairing is crucial to meeting the fundamental and applied challenges surrounding energy transition.

4For thousands of years solid-state chemistry was used as a series of recipes, similar to those found in culinary art. Over time and following nineteenth-century scientific discoveries, it became a real science of matter and its transformations. Through experiments, chemists were able to reveal the secrets of matter and to understand it better, in order to transform it rationally to create materials with the functionalities relevant to energy.

5Judging from the Baghdad battery, the “solid-state chemistry – energy” coupling already existed in Antiquity. Erstwhile potters moreover knew how to turn an ordinary mix of clay and water into beautiful pottery, and foundry-men knew how to obtain metals. Thus, over the centuries, the Stone Age led to the Copper Age, then to the Bronze and the Iron Ages. Note also that the first artificial pigment, Egyptian blue, was synthesized 5,000 years BCE. None of these craftsmen knew the chemical reactions involved in these transformations but they operated with reliable recipes whose science they did not understand.

6The shift from know-how to a science governed by scientific laws was not made easier by alchemists, whose overriding intention was to transform metals into gold by combining four elements: fire, air, earth, and water. It took over 2,000 years to shift from these four combined elements to the thirty-three elements proposed in 1789 by Lavoisier – who is considered de facto as the father of modern chemistry. His work triggered an effervescence of all aspects of chemistry, at a time when it would benefit from the great nineteenth-century discoveries (particularly the X-ray by Röntgen and atomic theory, developed by Planck and Schrödinger).

7All these discoveries contributed to the revival of solid-state chemistry in the early 1950s. This new expansion was also fuelled by the strong interactions that had developed with solid-state physicists and an industrial context highly conducive to the creation of innovative materials. Solid-state chemistry thus became a science, based on the relationship between properties and structures, which could be used to develop new materials with specific functionalities.

8Once these foundations were established, solid-state chemists used their main tool, the periodic table, to choose the right elements to control chemical bonding, compose its partition and design new composites, or adjust their physical-chemical properties on demand. Thus, through cationic/anionic substitution, they were able to orient the electronic and ionic conduction properties of materials, their optical properties, their colours, their magnetic properties, and even their energy storage properties, so as to turn them into materials valued highly in industry.

9This soft chemistry thus revolutionized our approaches to synthesis, allowing not only for the stabilization of new phases but also for the modification of their morphology, so that they could be used as a third dimension (in addition to temperature and pressure). This, in turn, would allow for the optimal orientation of the performance of the materials obtained. “Optimal”, as this science can sometimes find itself at the crossroads of the foreseen and the unforeseen, which is what makes it appealing to chemists.

10Given the limited time we have to address energy issues, the chemist’s intuition and ability to assemble atoms and create composites are no longer sufficient to exploit rapidly the full wealth of the periodic table. Thousands of combinations are possible. Much hope is therefore put in the ability of rational combinatorial theoretical chemistry to imitate, with materials, the processes that occur in the genome.

• A video of the Lecture can be found at www.college-de-france.fr, on the professor’s page.