By Prof. Andreas Hintennach, Daimler AG, Mercedes-Benz, Group Research, Germany.
Ever since the development of lithium-ion batteries the spirit of invention has mainly lead to an evolution of existing materials. With the focus on olivine and Nickel- and cobalt based materials the energy densities, power densities and ageing mechanisms could be investigated over the years and support the understanding of the underlying mechanisms of electrochemical energy storage and conversion.
With increasing numbers of cells being used in the world the need of a post Lithium-Ion technology emerges due to a limited availability of highly pristine nickel and cobalt and increasing need for recycling, environmental protection and overall energy efficiency. Nevertheless there is still an ongoing and very promising approach for e. g. novel stoichiometries of NMC materials, olivine materials, and nickel-rich materials with can significantly increase the energy density. But due to some limitation in the field of raw materials availability, accessibility, and sustainability, low-cobalt or cobalt-free materials are of very high interest, too. For example LMR (LNMO) can be an ideal candidate. Due to the very high reactivity and potential (i. e. 4.5 V) these materials require highly stable electrolytes.
Finally, lithium-sulphur can lead to a highly recyclable, environmentally friendly system. Having a silicon-based anode (> 85 % Si) included both volumetric and gravimetric energy density can mean an interesting alternative to metal-oxide based materials.
With the increased energy density, safety becomes a more and more important aspect in thermodynamic and kinetic investigations of these materials. This aspect can lead to the development of non-flammable electrolytes or solid state cells.
Solid state cells are a very different but highly promising approach. Having a solid-solid interphase between electroactive materials and electrolyte the chemicals mechanisms significantly change to solid state chemistry rather than solid-organic interphases chemistry.
All types of novel chemistries exhibit very different chemical mechanisms which require specific synthetically work, e. g. with the support of numerical simulation, for electrolytes, additives, binders, carbon materials, and even the surfaces of the electro-active materials itself. Understanding these mechanisms is essential to further improve the life-time, efficiency, and hence, the sustainability of any kind of energy storage and conversion, but batteries in particular.
Andreas Hintennach is a chemist and medical doctor. He received his PhD in electrochemistry from the ETH Zurich and Paul Scherrer Institute (Switzerland) in 2010. After a postdoc stay at MIT in the field of lithium-air and catalysis 2010-11 he joined the research department of Daimler AG where he serves as a senior manager. His present focus in the field of electrochemistry is fundamental research on next generation electrical energy storage and conversion materials and systems, sustainability and toxicology.