Investigation of the Mechanism of Self-Healing Binders for Silicon Anodes

Tamara Patranika^a, Kristina Edström^a, Guiomar Hernández^a

^aDepartment of Chemistry, Ångström Laboratory, Uppsala University, Sweden

Materials for Sustainable Development Conference (MATSUS)
Proceedings of MATSUS Fall 2023 Conference (MATSUSFall23)

#EMERBAT - Emerging battery technologies

Torremolinos, Spain, 2023 October 16th - 20th

Organizers: Philipp Adelhelm, Maria Crespo and Guiomar Hernández

Oral, Tamara Patranika, presentation 029
DOI: https://doi.org/10.29363/nanoge.matsus.2023.029
Publication date: 18th July 2023

Silicon is a promising active material for anodes in lithium-ion batteries owing to its high theoretical capacity (3579 mAh/g)¹. However, it is well known that the compound contends with large volume changes during cycling, creating cracks in the material and therefore limiting the lifetime and capacity of the cell. To cope with these volume changes, this project aims to develop self-healing binders to improve the cycling stability of lithium-ion batteries.

Both hydrogen bonds and dynamic covalent bonds have previously been used to modify binder systems to get self-healing properties through reversible cross-linking with the binder in the electrode. While the hydrogen bonds have eminent reversibility, the dynamic covalent bonds provide high mechanical stability^2–4. Both of which is desirable properties to implement in the polymeric binder system.

Specifically, the focus of this work has been to utilize the reversibility of borate ester bonds and couple them with the polymer binder poly(vinyl alcohol) (PVA). The electrochemical performance of the cells has been investigated, where the borate ester-based binders have shown an increased capacity compared to the PVA binder alone. Besides the performance, understanding the self-healing mechanism of these binders and possible degradation reactions from these functionalities is key to further improving the system and cycle life. Therefore, the mechanism behind the self-healing was investigated through FTIR measurements at room and elevated temperatures. Furthermore, the electrochemical stability of the functional groups was investigated in order to compare the impact of dynamic covalent bonding, especially at the low operating voltages of silicon. This purposes that the self-healing functionalities are electrochemically stable and do not contribute to increased degradation in the cell.

References:

[1] Nguyen, C. C et al., Systematic Investigation of Binders for Silicon Anodes: Interactions of Binder with Silicon Particles and Electrolytes and Effects of Binders on Solid Electrolyte Interphase Formation. ACS Appl Mater Interfaces 8, 12211–12220 (2016).

[2] Chen, G et al., Design of Robust Self-Healing Silicone Elastomers Based on Multiple H-Bonding and Dynamic Covalent Bond. Langmuir (2021).

[3] Dahlke, J et al., How to Design a Self-Healing Polymer: General Concepts of Dynamic Covalent Bonds and Their Application for Intrinsic Healable Materials. Adv Mater Interfaces 5, 1800051 (2018).

[4] Xu, J. H. et al., Intrinsic self-healing polymers for advanced lithium-based batteries: Advances and strategies. Appl Phys Rev 7, 031304 (2020).

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