(Invited) Utilizing Conjugated Imine Polymers to Stabilize Nanoparticle Silicon Anodes

Abstract

Silicon anodes provide a compelling route towards delivering high-capacity lithium-ion batteries, however they are notoriously difficult to stabilize in conventional liquid electrolytes that are compatible with high performance cathodes. Furthermore, the drastic changes in volume that occur as silicon is lithiated and delithiated can lead to rapid cell failure and innovative polymeric binders are required to help mitigate mechanical issues. We have recently developed a novel method to synthesize the conjugated binder polyphenylmethanimine (polyPMI) using an imine metathesis reaction. We have demonstrated that this polymer can be used to stabilize silicon nanoparticles to produce a composite lithium-ion battery anode that is electrochemically stable for hundreds of lithiation and delithiation cycles with a Coulombic efficiency that is greater than 99.95% in a traditional carbonate liquid electrolyte.1 This novel polymeric coating passivates silicon nanoparticles by shielding them from direct electrolyte contact while maintaining effective ionic and electronic transport and also imbues the electrodes with excellent mechanical resilience to the volumetric changes experienced during cycling. We will cover the structure/property relationship of polyPMI within the context of the unique mechanical and electrochemical requirements of nanoparticle silicon anodes. We will also discuss the electrochemical behavior of this polymer and how it also offers new opportunities as an organic lithium-coordinating material that can be used to stabilize a variety of other battery electrodes. More broadly, we will posit that this solution-processed, ionically conductive, and electronically conductive polymer is applicable for a variety of energy storage and conversion technologies. Finally, this work will demonstrate how this novel polymer chemistry provides additional opportunities for tuning electrode architecture to target high areal capacity electrodes that enable high gravimetric and volumetric capacity full cells.1. T. R. Martin et al., Adv. Energy Mater., 2203921 (2023).