Rechargeable high energy density Aluminum ion-batteries - Fundamental structural material defect engineering and interface control

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To support the growing demand for electrochemical energy storage, complementary or even superior technological solutions over traditional Li-ion batteries are urgently needed. Aluminum batteries are particularly attractive candidates owing to their high projected volumetric energy density, low cost, high safety. Moreover, being the most abundant metal on the Earth crust, aluminum also matches the sustainability requirement that is mandatory to develop durable technologies. A critical feature of Al3+ intercalation chemistry is the high charge density of this cation that ultimately affects the electrolyte properties (solvation-desolvation processes) and the ability of host frameworks to reversibly accommodate a large proportion of Al3+ thus generating high energy. In this German-French consortium project, we study fundamental aspects as well as more applied cell-related challenges of the interfacial processes and materials chemistry pertinent to high-energy density aluminum batteries. We achieve this by working on a range of cell components and cell processes simultaneously, such as the electrolytes, electrode materials and electrode-electrolyte interfaces. Work will be focusing on oxide-based electrode materials with controlled amounts of cationic vacancies, that were shown in our earlier work to enable solid-state diffusion of Al3+ while providing additional insertion sites. Concomitantly, physicochemical properties (conductivity, speciation, etc) of suitable electrolytes and their interface with Al and the positive electrode material will be characterized using a wide array of in-situ und ex-situ techniques, such as X-ray Absorption, Nuclear Magnetic Resonance, high resolution Transmission electron microscopy, X-ray scattering, pair distribution functions and others.Specifically, exploiting our defect engineering approach, the French group (Leader: Damien Dambournet) will design novel intercalation compounds consisting of oxidic networks with unprecedented large content of cationic vacancies. For example, spinel iron oxide will be doped with high charge cations such as MoVI to generate large vacancy content.The German group (Leader: Peter Strasser) will study the electrochemical dynamics of Al3+ intercalation of the new materials designed by the French group. The impact of the electrolyte properties on the electrochemistry will be investigated along with the electrodes-electrolyte interfaces. This project offers much added value between two premier research institutions and will benefit from a strong and already proven fruitful German-French collaboration on defective oxide materials for multi-valent batteries. Project outcomes will include fundamental and practical new insights into the intercalation chemistry, the cell processes, and the cell design of Al batteries, and thus will make important contributions to a greener, safer and higher-energy density battery technology in the future.