Silicon-based electrodes have garnered significant attention in the field of lithium-ion batteries owing to their promising features, notably the high specific capacity of approximately 3580 mAh g−1 of silicon and the element’s low cost coupled with high natural abundance. However, the practical utilization of silicon in battery electrodes is hindered by challenges such as high volumetric expansion during cycling, reaching approximately 280% compared to a mere 10% for graphite electrodes, thus posing a critical threat to battery life.[1-4]
Various strategies have been proposed and explored to address these challenges and leverage the inherent advantages of silicon-based electrodes. One prominent approach involves modifying silicon materials to enhance the performance and stability of silicon electrodes during cycling.[1,2] Additionally, pre-lithiation techniques have been investigated to mitigate the detrimental effects of volumetric expansion.[4] Furthermore, electrolyte modification has emerged as a promising avenue to overcome volumetric expansion issues and improve the efficiency of silicon-based batteries.[1,3]
Moreover, the formation of Li-M-Si (M = Ca, Mg) Zintl phases via Mg and Ca additives has been studied to stabilize silicon electrodes and enhance their battery performance. These phases not only accommodate the volume changes associated with lithiation and delithiation but also contribute to the overall performance and longevity of the battery. This phenomenon is already published for bis(trifluoromethane sulfonyl)imide (TFSI) salts of Mg and Ca.[3] It has shown promising results in improving the stability and lifespan of silicon-based batteries.[3,5]
Additionally, exploring Li-Mg-Si phases for Mg coating applications has demonstrated potential in enhancing silicon-based electrodes’ stability and electrochemical performance.[5]
This work investigated novel Mg and Ca salts for their effect as additives on our utilized silicon-based blend electrodes in (NMC622 ‖ Si-based blend-electrodes) cells. The salts were introduced as additives to the standard electrolyte LiPF6 (1 mol L−1) in EC:EMC (3:7, by weight). For completeness, experiments included MgX2, CaX2, and the equivalent Li salt, LiX. The anion’s nature has to be kept confidential for the project’s interest. Next to cycling behavior, Scanning electrode microscopy and Energy-dispersive X-ray spectroscopy were applied to examine the additive’s effect on the system.
[1] N. Nitta, F. Wu, J. T. Lee, G. Yushin, Mater. Today, 2015, 18, 252.
[2] Q. Shi et al., Energy Storage Mater., 2021, 34, 735.
[3] B. Han et al., ACS Appl. Mater. Interfaces., 2019, 11, 33.
[4] T. Jia et al., Green Energy and Environment, 2023, 8, 1325.
[5] Z. Li et al., ACS Appl. Energy Mater., 2020, 3, 11534.