Organic Cathode Materials for Magnesium Batteries

在德国，人们对开发新的可再生能源的必要性达成了巨大的共识。然而，其中许多能源，如风能或太阳能，并不是持续可用的，因此对储能材料的研究变得必要。在电动汽车应用中，当涉及到为私人、经济、公共或军事应用扩大电动汽车或无人驾驶飞行器的覆盖范围时，这一点将更加重要。与锂相比，镁不仅在地壳中更丰富、更便宜、危险更小，而且具有类似的比容和更高的体积电容，而标准电极电位仅略低于锂。这使得镁成为下一代充电电池的一种有前途的材料。目前，除了许多电解液的电化学稳定性不足外，主要的挑战是动力学速度慢，可逆性差，电极中镁离子的浓度较低，阻碍了此类电池的实现。在快速充放电过程中，例如在电迁移率中，迟缓地结合到主体材料中的一个主要问题是二价镁离子的高电荷密度。因此，作为目前研究的插层电极的替代方案，本项目集中在有机聚合物电极材料的研究上。由于高比表面积，聚合物中氧化还原活性基团与镁离子之间的相互作用仅发生在电极表面，从而实现更快的充电和放电。木质素广泛存在于所有植物生物质中，将被用作电活性聚合物物种。已经有文献将其与导电聚合物结合用于有机电池应用。此外，高比表面积也是至关重要的。在本项目中，将通过静电纺丝获得具有高比表面积的多孔导电木素纤维。首先，将木质素、水溶性辅助聚合物和导电聚合物或其前体或碳纳米管的组合纺丝，然后溶解辅助聚合物。该项目包含不同问题的木质素。一方面，它涉及以木质素为基础的聚合物材料及其结构，以及三元聚合物混合物的结构。另一方面，木质素的电化学性质及其与离子的相互作用也是焦点。将这两个学科结合起来，将能够创造出基于生物的聚合物电极材料。通过更好地了解电化学镁在聚合物材料和复杂环境中的传导和沉积，将完成迈向未来储能材料的重要一步。

In Germany there is a great consensus about the necessity of developing new sources of renewable energy. However, many of these, like wind or solar power, are not continuously available, and research on energy storage materials becomes necessary. In electromobility applications this will be even more important when it comes to expanding the reach of electric cars or unmanned aerial vehicles for private, economic, public or military applications. Compared to lithium, not only is magnesium more abundant in the earth crust, cheaper, and less dangerous, it also has a similar specific and higher volumetric capacitance while the standard electrode potential is only slightly less negative. This makes magnesium a promising material for next generation rechargeable batteries. Currently, major challenges besides insufficient electrochemical stability of many electrolytes are the slow kinetics, bad reversibility, and low density of magnesium ion incorporation into electrodes, preventing such batteries from being realized. One major problem for sluggish incorporation into host materials as necessary for fast charge-discharge processes in, e.g., electromobility is the high charge density of bivalent magnesium ions. As an alternative to currently investigated intercalation electrodes, this project hence focusses on research about organic polymer electrode materials. Because of a high specific surface area, interactions between redox active groups within the polymer and magnesium ions will only be at the electrode surface, enabling faster charging and discharging. Lignin, which is omnipresent in all plant biomass, will be used as electroactive polymer species. There is already literature about using it for organic battery applications in combination with conductive polymers. Also there, a high specific surface area is crucial. In this project, porous conductive lignin fibers with a high specific surface area will be gained by electrospinning. First, a combination of lignin, a water-soluble auxiliary polymer, and a conductive polymer or its precursor or carbon nanotubes will be spun, followed by dissolution of the auxiliary polymer. The project contains different issues of lignin. On the one hand it deals with lignin based polymer materials, its structures, and with structuring a ternary polymeric mixture. On the other hand the electrochemistry of lignin and interaction with ions is in focus. Combining both subjects will enable creation of bio-based polymeric electrode materials. Through a better understanding of electrochemical magnesium conduction and deposition in polymer materials and intricate settings, an important step towards future energy storage materials will be completed.