Foss Carl Erik Lie, Müssig Stephan, Svensson Ann Mari, Vie Preben J S, Ulvestad Asbjørn, Mæhlen Jan Petter, Koposov Alexey Y
Institute for Energy Technology, P.O. Box 40, 2027, Kjeller, Norway.
Department of Material Science and Engineering, Norwegian University of Science and Technology (NTNU), Høgskoleringen 1, 7491, Trondheim, Norway.
Sci Rep. 2020 Aug 6;10(1):13193. doi: 10.1038/s41598-020-70001-5.
Silicon, while suffering from major degradation issues, has been recognized as a next promising material to replace currently used graphite in the anodes of Li-ion batteries. Several pathways to mitigate the capacity fading of silicon has been proposed, including optimization of the electrode composition. Within the present work we evaluated different binder formulations to improve the long-term performance of the Li-ion batteries' anodes based on industrial grade silicon (Si) which is typically characterized by a particle sizes ranging from 100 nm to 5.5 microns. The decrease of pH in a binder formulation was found to detrimental for the cycling performance of Si due to enhanced formation of an ester-type bonding between the carboxylic group of the binder and hydroxyl group on the Si surface as well as cross-linking. Furthermore, the present work was focused on the use of the industrial grade Si with very high loading of Si material (up to 80% by weight) to better highlight the effects of the surface chemistry of Si and its influence on the performance of Si-based anodes in Li-ion batteries. The tested system allowed to establish a pseudo self-healing effect that manifests itself through the restoration of the anode capacity by approximately 25% and initiates after approximately 20 cycles. The stabilization of the capacity is attributed to self-limiting lithiation process. Such effect is closely related to SEI formation and transport properties of an electrode prepared from silicon of industrial grade.
硅虽然存在严重的降解问题，但已被公认为是有望替代锂离子电池负极中目前使用的石墨的下一种材料。已经提出了几种减轻硅容量衰减的途径，包括优化电极组成。在本工作中，我们评估了不同的粘结剂配方，以改善基于工业级硅（Si）的锂离子电池负极的长期性能，该工业级硅的典型粒径范围为100纳米至5.5微米。发现粘结剂配方中pH值的降低对硅的循环性能有害，这是由于粘结剂的羧基与硅表面的羟基之间形成酯型键以及交联增强所致。此外，本工作重点关注使用具有非常高硅材料负载量（高达80重量%）的工业级硅，以更好地突出硅的表面化学作用及其对锂离子电池中硅基负极性能的影响。所测试的系统能够建立一种伪自修复效应，该效应通过阳极容量恢复约25%来体现，并在大约20次循环后开始。容量的稳定归因于自限性锂化过程。这种效应与由工业级硅制备的电极的SEI形成和传输特性密切相关。
