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很大的共识。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，当涉及到扩大电动汽车或无人驾驶飞行器的私人、经济、公共或军事应用范围时，这将更加重要。与锂相比，镁不仅在地壳中更丰富、更便宜、更不危险，而且在标准电极电位略低于负的情况下，它也具有相似的比容量和更高的体积电容。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够外，主要的挑战是动力学慢、可逆性差、镁离子在电极中的掺入密度低，阻碍了此类电池的实现。二价镁离子的高电荷密度是快速充放电过程（例如，电动汽车）所必需的，但在宿主材料中缓慢掺入的一个主要问题。作为目前研究的插层电极的替代方案，本项目将重点研究有机聚合物电极材料。由于具有较高的比表面积，聚合物中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进行，从而实现更快的充放电。木质素是一种普遍存在于所有植物生物量中的电活性高分子材料。已经有文献将其与导电聚合物结合用于有机电池。同样，高比表面积也是至关重要的。本课题将通过静电纺丝获得具有高比表面积的多孔导电木质素纤维。首先，将木质素、水溶性辅助聚合物和导电聚合物或其前驱体或碳纳米管结合在一起，然后将辅助聚合物溶解。该项目包含不同的木质素问题。一方面，它处理木质素为基础的高分子材料，其结构，并与结构三元聚合物混合物。另一方面，木质素的电化学和与离子的相互作用是重点。结合这两门学科将使生物基聚合物电极材料的创造成为可能。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.