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广泛的共识。然而，其中许多能源，如风能或太阳能，并不是持续可用的，因此有必要对储能材料进行研究。在电动汽车应用中，当涉及到扩大电动汽车或无人驾驶飞行器在私人、经济、公共或军事应用中的覆盖范围时，这将更加重要。与锂相比，镁不仅在地壳中更丰富，更便宜，危险性更低，而且还具有类似的比电容和更高的体积电容，而标准电极电位仅略低于负。这使得镁成为下一代可充电电池的有前途的材料。目前，除了许多电解质的电化学稳定性不足之外，主要的挑战是镁离子掺入电极中的缓慢动力学、不良可逆性和低密度，这阻碍了此类电池的实现。一个主要的问题是缓慢地掺入到主体材料中，这是快速充放电过程所必需的，电迁移率是二价镁离子的高电荷密度。作为目前研究的嵌入电极的替代方案，本项目因此集中于有机聚合物电极材料的研究。由于高比表面积，聚合物内的氧化还原活性基团与镁离子之间的相互作用将仅在电极表面，从而实现更快的充电和放电。木质素，这是无处不在的所有植物生物质，将被用作电活性聚合物物种。已经有关于将其与导电聚合物结合用于有机电池应用的文献。此外，高比表面积也至关重要。本课题采用静电纺丝技术制备具有高比表面积的多孔木质素导电纤维。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。该项目包含木质素的不同问题。一方面，它涉及基于木质素的聚合物材料，其结构，以及三元聚合物混合物的结构化。另一方面，木质素的电化学和与离子的相互作用是焦点。结合这两个主题将能够创建生物基聚合物电极材料。通过更好地理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.