MATERIALLY BETTER BATTERIES FOR ENERGY STORAGE

The lithium-ion battery has already revolutionised portable electronics, but to meet the new challenges of climate change and energy security that face humanity in the 21^st-century, new generations of lithium batteries are required. In large measure advances in materials will drive advances in lithium batteries. New anode, electrolyte and cathode materials are required and such materials have to be fashioned in new ways and with new, often hierarchical, structures. This is a vast topic. I shall focus on two key materials challenges, high capacity cathodes for lithium-ion batteries and the lithium-oxygen battery.

The energy stored in lithium-ion batteries is, in large part, limited by the capacity to store charge in the positive electrode (cathode). While advances have been made over the years, progressing from the original and still widely used LiCoO₂ to Li(NiMnCo)O₂ in its various forms, there is a need to go further. High-capacity cathodes will be discussed with particular emphasis on progressing our fundamental understanding of the mechanisms in such materials.

While lithium-ion batteries will be a major technology for some years to come, the maximum energy storage possible with such a technology will not meet the longer term demands of society for energy storage. As scientists and engineers we must work now on exploring electrochemical energy storage beyond the horizon of lithium-ion batteries. The lithium- air (O₂) battery offers theoretically the highest specific energy. Recent progress has shown the direction that should be followed towards a technology but challenges certainly remain, many of which are materials challenges. The operation and materials challenges that face the lithium-oxygen battery will be discussed.