Institute of Engineering Thermodynamics, German Aerospace Center (DLR), Pfaffenwaldring 38-40, 70569 Stuttgart, Germany.
Institute of Inorganic Chemistry, University of Stuttgart, Pfaffenwaldring 55, 70569 Stuttgart, Germany.
ACS Appl Mater Interfaces. 2023 Jul 12;15(27):33013-33027. doi: 10.1021/acsami.3c07223. Epub 2023 Jun 30.
In the search for post-lithium battery systems, magnesium-sulfur batteries have attracted research attention in recent years due to their high potential energy density, raw material abundance, and low cost. Despite significant progress, the system still lacks cycling stability mainly associated with the ongoing parasitic reduction of sulfur at the anode surface, resulting in the loss of active materials and passivating surface layer formation on the anode. In addition to sulfur retention approaches on the cathode side, the protection of the reductive anode surface by an artificial solid electrolyte interphase (SEI) represents a promising approach, which contrarily does not impede the sulfur cathode kinetics. In this study, an organic coating approach based on ionomers and polymers is pursued to combine the desired properties of mechanical flexibility and high ionic conductivity while enabling a facile and energy-efficient preparation. Despite exhibiting higher polarization overpotentials in Mg-Mg cells, the charge overpotential in Mg-S cells was decreased by the coated anodes with the initial Coulombic efficiency being significantly increased. Consequently, the discharge capacity after 300 cycles applying an Aquivion/PVDF-coated Mg anode was twice that of a pristine Mg anode, indicating effective polysulfide repulsion from the Mg surface by the artificial SEI. This was backed by operando imaging during long-term OCV revealing a non-colored separator, i.e. mitigated self-discharge. While SEM, AFM, IR and XPS were applied to gain further insights into the surface morphology and composition, scalable coating techniques were investigated in addition to ensure practical relevance. Remarkably therein, the Mg anode preparation and all surface coatings were prepared under ambient conditions, which facilitates future electrode and cell assembly. Overall, this study highlights the important role of Mg anode coatings to improve the electrochemical performance of magnesium-sulfur batteries.
在寻找锂离子电池之后的电池系统时，由于具有高的能量密度、丰富的原料和低成本，镁-硫电池近年来引起了研究关注。尽管取得了重大进展，但该系统仍然缺乏循环稳定性，主要与阳极表面不断进行的硫的寄生还原有关，导致活性材料损失和阳极表面钝化层形成。除了在阴极侧保留硫的方法外，通过人工固体电解质界面（SEI）保护还原的阳极表面是一种很有前途的方法，因为它不会阻碍硫阴极的动力学。在这项研究中，采用基于离聚物和聚合物的有机涂层方法来结合机械柔韧性和高离子导电性所需的特性，同时实现简便且节能的制备。尽管在 Mg-Mg 电池中表现出更高的极化过电位，但经涂层处理的阳极使 Mg-S 电池的充电过电位降低，初始库仑效率显著提高。因此，在应用 Aquivion/PVDF 涂层的 Mg 阳极 300 次循环后，放电容量是原始 Mg 阳极的两倍，表明人工 SEI 有效地排斥了镁表面的多硫化物。这得到了在 OCV 期间进行的长时间操作成像的支持，显示出非着色的分离器，即减轻了自放电。虽然 SEM、AFM、IR 和 XPS 被应用于进一步了解表面形貌和组成，但还研究了可扩展的涂层技术，以确保实际相关性。值得注意的是，Mg 阳极的制备和所有表面涂层都是在环境条件下进行的，这便于将来进行电极和电池组装。总的来说，这项研究强调了 Mg 阳极涂层对于改善镁-硫电池电化学性能的重要作用。
