The high energy capacity of Silicon (Si) anodes in Li-ion batteries is plagued with huge volume fluctuations during battery cycling, leading to rapid material degradation and poor cycle life. Binders are polymeric additive materials that are used to combine several components of the electrode and the current collector. Si anodes with traditional binders (that are used in graphite anodes) have poor cycle life. Si anodes with various other binders have shown significant improvement in cycle life. However, not all binders work with Si, which suggests that certain key properties are essential. In this work, we have examined three crucial binder properties: adhesion strength to Si, mechanical elasticity, and Li-ion conductivity. We investigated three widely used C/H/N-based binders for their applicability in Si anodes: pyrolyzed polyacrylonitrile (PPAN), polyacrylonitrile (PAN), and polyaniline (PANI). Utilizing both experiments and ReaxFF based molecular dynamics simulations, we determined that on all the three property metrics, PPAN appears superior compared to the other two binders. Electrochemical cycling experiments show that PPAN outperforms the other two binders, retaining a capacity of ~1400 mAhg<sup>-1</sup> for 150 cycles. The analysis of each property not only helps us understand why PPAN is superior to other binders and but also reveals several structural features that are important for designing high-performance binders for Si anodes. Using a similar approach, we are currently investigating the binder/electrolyte interfaces, which are also important for controlling irreversible capacity losses and the overall cycle life of the Si-anode based Li-ion batteries.

Designing high-performing binders for Si anodes in Li-ion batteries: Experiments and ReaxFF Simulations

ACS Spring 2022

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.