Potassium-Ion batteries: sustainable strategies

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Li-ion batteries (LIB) as high-energy storage solution of choice experience a tremendous growth in recent years owing to increasing demand in the transport sector. The expansion of battery storage is accompanied with the concern of resource shortage in the foreseeable future for elements such as Li, Co or Ni. Successor technologies like Na- or K-ion batteries (NIB and KIB) ought to avoid this problem by use of more abundant resources. Up until now, these technologies suffer from poor reversibility and short battery life. A successful development of KIB has to focus not only on individual components but on the entire system allowing mutual adjustment of the cell components. Hence, this project aims at understanding of fundamental aspects of the key battery components, i.e. cathodes, anodes and electrolytes, and their mutual interactions in a KIB. This will be achieved by developing novel active materials, such as hexacyanometallates and oxo(fluoride)phosphates, hard carbons and studying their interactions at the electrode-electrolyte-interface. For example, oxo(fluoride)phosphates are considered nowadays a class of promising superfast cathodes for metal-ion batteries, that show stable cycling at high current densities, high mechanical stability due to a minor volume change, and operate at high electrochemical potentials. That latter, however, turns into a problem when the stability window of the electrolyte is exceeded. Therefore, novel and innovative material strategies are required to enable compatibility between the electrode interface and electrolyte, which can lift the energy density closer to the levels of common LIB at potentially lower cost and greater sustainability. Potential solutions are available through the research on LIB, e.g. lowering of the cathode redox potential by choice of less electropositive transition metals or developing suitable electrolyte additives that promote stable interface formation. However, in this respect KIB research is still at its beginning. Despite parallels to LIB, knowledge transfer between the two technologies has to be critically reviewed. At the same time, existing synergies shall be used most effectively in order to solve the major fundamental scientific challenges that currently hamper the KIB technology. Therefore, simultaneous development of the three key battery components is envisaged in this project. The link between anode and cathode activities is the electrolyte and the analysis of electrode-electrolyte interfaces in order to move KIB research forward in all major directions. The project is intended for three years and will be worked out by three teams: Skoltech (Russia), IFW Dresden and KIT (both in Germany). In order to promote a close collaboration between the teams, in particular Bachelor/Master and PhD students, joint beamtimes at synchrotron sources as well as constant sample exchange are planned. The teams possess all necessary infrastructure to perform this project.