Separating Initial Loss from Storage Capacity: Core-Shell Materials as Advanced Anode Materials for Sodium Ion Batteries

The current imperative to shift towards an energy grid equipped with sustainable energy storage solutions has caused a renewed interest in sodium-ion batteries (SIBs). Hard carbons (HCs) are a promising option high-capacity anode materials in SIBs. Nevertheless, their elevated capacities frequently come at the cost of experiencing substantial non-reversible initial capacity losses.[1, 2]
Commonly, significant losses are associated with irreversible reactions, such as the creation of the solid electrolyte interphase (SEI), that occur during the initial sodium insertion in HC-materials. Intriguingly, high values of irreversible capacity are often found for samples with experimentally determined low specific surface area.[1] A more comprehensive understanding of the structure-property relations is essential for quantifying and grasping the potential of hard carbon materials in sodium-ion batteries (SIBs). Thus, the objective is to employ analytical methods to establish a link between the structure and the electrochemical attributes of HC materials. This has been a challenge, partly due to the non-stoichiometric nature of the sodium storage mechanism and the disordered structure of HCs.
To address the challenges mentioned above, our approach is to explore whether a core-shell structure can separate sodium storage and SEI-formation. This way, we can investigate and fine-tune storage capacity and irreversible losses, independently. The strategy involves the synthesis of various porous carbon structures to serve as the core material and their combination with sodium-conductive structures to core-shell materials. Herein, we will present different synthesis routes towards tailor-made carbon core materials. Moreover, different coatings concepts will be introduced, and the electrochemical performance of the core and core-shell materials compared.
Generally, these core-shell anodes promise to enable high capacities accompanied with low irreversible losses due to optimized SEI-formation.

Literature:
[1] Y. Matsukawa, F. Linsenmann, M. A. Plass, G. Hasegawa, K. Hayashi, and T.-P. Fellinger, Beilstein J. Nanotechnol. 2020, 11, 1217.
[2] A. Mehmood , G. Ali, B. Koyutürk, J. Pampel, K. Y. Chung, and T.-P. Fellinger, Energy Storage Materials 2020, 28, 101.