Developing Tailor-Made Core-Shell Hard Carbon Materials As Anode Materials in Sodium Ion Batteries

Abstract

The current strong interest in electromotive mobility and the need to transition to an energy grid with sustainable storage devices has led to a renewed interest in sodium ion batteries (SIBs). Hard carbons (HCs) are promising candidates for high-capacity negative electrode materials in SIBs. Their high capacities, however, are often accompanied with high irreversible capacity losses during the initial cycles.[1]Generally, large losses can be connected to irreversible reactions, e.g., the formation of the solid electrolyte interphase (SEI), during the initial sodiation of the HC-material. However, high irreversible capacity values are often in contradiction to the experimentally determined low surface area of the sample material.[1] A better understanding of the structure-property relationship should enable quantification and understanding of the potential of hard carbon materials for SIBs. Hence, the aim is to use analytical techniques to establish a correlation between the structure and the electrochemical characteristics of HC-materials. This has previously been difficult, in part because the sodium storage mechanism is not stoichiometric and due to the disordered structure of HCs.In order to tackle the aforementioned challenges, our approach is to explore whether a core-shell structure can separate sodium storage and solid electrolyte interphase formation. Thus, storage capacity and irreversible losses could be investigated and finally optimized separately. The synthesis of a selection of porous carbon structures serving as the core material, will be attempted. Simultaneously, sodium-conducting shell structures will be developed to allow for separation of sodium ions and electrolyte molecules. Subsequently, the combination of core and shell materials will be undertaken. These anodes should enable high capacities accompanied with low irreversible losses due to optimized SEI-formation.Literature:[1] Matsukawa, Y.; Linsenmann, F.; Plass, M. A.; Hasegawa, G.; Hayashi, K.; Fellinger, T.-P. Beilstein J. Nanotechnol. 2020, 11, 1217–1229.