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

为了支持日益增长的电化学储能需求，迫切需要与传统锂离子电池互补甚至更先进的技术解决方案。铝电池因其高的预计体积能量密度、低成本、高安全性而成为特别有吸引力的候选电池。此外，作为地壳中储量最丰富的金属，铝也符合可持续发展的要求，这是开发耐用技术的强制性要求。Al3+插层化学的一个关键特征是这种阳离子的高电荷密度，最终影响到电解液的性质(溶剂化-去溶过程)和主体骨架可逆地容纳大量Al3+从而产生高能量的能力。在这个德法联合项目中，我们研究了与高能量密度铝电池相关的界面工艺和材料化学的基本方面以及更多与电池相关的应用挑战。我们通过同时处理一系列电池组件和电池工艺来实现这一点，例如电解液、电极材料和电极-电解液界面。我们的工作将集中在具有受控阳离子空位数量的氧化物电极材料上，这在我们早期的工作中显示了能够实现Al3+的固态扩散，同时提供更多的插入位置。与此同时，合适的电解液及其与铝和正极材料的界面的物理化学性质(导电性、形态等)将使用广泛的原位和非原位技术来表征，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、对分布函数和其他。具体地说，利用我们的缺陷工程方法，法国团队(负责人：Damien Dambournet)将设计由氧化网络组成的新型插层化合物，其中含有前所未有的大量阳离子空位。例如，尖晶石氧化铁将与MoVI等高电荷阳离子掺杂以产生大量空位含量。德国小组(Leader：Peter Strasser)将研究法国小组设计的新材料嵌入Al3+的电化学动力学。电解液性质对电化学的影响将与电极-电解液界面一起研究。该项目在两个主要研究机构之间提供了很大的附加值，并将受益于德国和法国在用于多价电池的缺陷氧化物材料方面的强大和已经被证明是富有成效的合作。项目成果将包括对铝电池的嵌入化学、电池工艺和电池设计的基本和实用的新见解，从而将为未来更绿色、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.