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

为了支持对电化学能量存储的日益增长的需求，迫切需要与传统锂离子电池互补甚至上级的技术解决方案。铝电池由于其高体积能量密度、低成本、高安全性而特别有吸引力。此外，作为地壳上最丰富的金属，铝也符合开发耐用技术所必需的可持续性要求。Al 3+嵌入化学的关键特征是该阳离子的高电荷密度，其最终影响电解质性质（溶剂化-去溶剂化过程）和主体框架可逆地容纳大比例的Al 3+从而产生高能量的能力。 在这个德法联盟项目中，我们研究了与高能量密度铝电池相关的界面过程和材料化学的基本方面以及更多与电池相关的应用挑战。我们通过同时研究一系列电池组件和电池工艺来实现这一目标，例如电解质，电极材料和电极-电解质界面。工作将集中在具有受控量的阳离子空位的氧化物基电极材料上，这些材料在我们早期的工作中显示出能够使Al 3+固态扩散，同时提供额外的插入位点。同时，理化性质合适的电解质及其与Al和正电极材料的界面（电导率、形态等）将使用广泛的原位和非原位技术来表征，例如X射线吸收、核磁共振、高分辨率透射电子显微镜、X射线散射、对分布函数等。具体地，利用我们的缺陷工程方法，法国小组（组长：Damien Dambournet）将设计新型插层化合物，该化合物由具有前所未有的大量阳离子空位的氧化物网络组成。例如，尖晶石氧化铁将掺杂高电荷阳离子如MoVI，以产生大的空位含量。德国小组（组长：Peter Strasser）将研究法国小组设计的新材料的Al 3+嵌入的电化学动力学。将沿着电极-电解质界面研究电解质性质对电化学的影响。 该项目为两个主要研究机构提供了更多的附加值，并将受益于德法在多价电池缺陷氧化物材料方面的强大且已被证明富有成效的合作。项目成果将包括对铝电池的插层化学、电池过程和电池设计的基本和实用的新见解，从而为未来更绿色、更安全和更高能量密度的电池技术做出重要贡献。

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.