Ryan Tae

Optimizing Silicon Anodes: Investigating Ultra-High Carboxyl Density Binders

Started June 9, 2023

Abstract or project description

While electric vehicles offer a promising solution to fossil fuel-induced environmental damage, over 70% of consumers hesitate to transition, citing limited capacity as their primary concern. Replacing traditional graphite anodes with silicon (Si) can solve this gap and revolutionize battery technology, expanding capacity 11-fold. However, Si expansion during charging can compromise battery integrity, prompting the aim of this study–improving Si-anode stabilization with polymeric binders. Preliminary research, using data-driven models, theoretically suggested that binders with ultra-high carboxyl (COOH) density (.33 COOH/monomer) could optimize Si-stabilization through opposing mechanisms–adhesion and electrolyte consumption. This study resolves these mechanisms, examining their relationships with ultra-high COOH density binders, to predict and optimize Si-anode functionality. Using Density Functional Theory (DFT) simulations, interaction energy (IE) was used to quantify binder adhesion whereas pKa was used for electrolyte consumption. COOH density was strongly correlated with increased IE (r = 0.90), as opposed to pKa (r = -0.15), indicating enhanced binder adhesion without additional electrolyte consumption at ultra-high COOH densities. Qualitative molecular analysis, using DFT WebMO simulation, revealed coordinate covalent-bonding as a novel adhesion mechanism, with unpaired t-tests indicating a significant increase in IE (p<.01). Standard (n=2) and ultra-high COOH (n=1) batteries were then physically synthesized to measure true performance using standard electrochemical charging/discharging techniques, confirming that ultra-high COOH density improves battery performance by 90% (p<0.01). Demonstrating that ultra-high COOH density binders achieve unprecedented adhesion without simultaneously increasing electrolyte consumption, this study establishes proof of concept for ultra-high COOH density binders in next-generation Si-anodes to meet global, sustainable energy demands.