(Invited) Functional Binder for Battery Electrode: Formation of Hierarchically Ordered Structures in Conductive Polymers to Enhance Ion and Electron Transport in the Electrode

Abstract

Electrode binder is a critical component for the successful engineering of modern lithium-ion rechargeable batteries. Electrode binder provides cohesion among the micron and nano size electrode particles, adhesion between particles and current collectors, and modulates particles volume changes during charge and discharge. The alloy material-based anode such as Si and Sn, is an attractive candidate for lithium-ion batteries and solid-state battery because it delivers much greater theoretical (e.g. Si at 4200 mAh/g) specific capacity than that of a traditional graphite anode material (∼370 mAh/g). However, the widespread application of silicon materials has remained a significant challenge because of the large volume change during lithium insertion and extraction processes, disrupting the electrode surface, electrode mechanical formation and cell integrity. The instabilities of the alloy materials lead to loss of the electrical contact in the electrode and increased parasitic reactions with electrolyte, causing the battery failure and significantly shorten the battery life. To address those challenges, multifunctional conductive polymers have been re-designed. In the conventional design of conductive polymers, organic functionalities are introduced via bottom-up synthetic approaches to enhance specific properties by modification of the individual polymers. Unfortunately, the addition of functional groups leads to conflicting effects, limiting their scaled synthesis and broad applications. Here we show a conductive polymer coating with simple primary building blocks that can be thermally processed to develop hierarchically ordered structures (HOS) with well-defined ordered morphologies. Our approach to constructing permanent HOS in conductive polymers leads to substantial enhancement of charge transport properties and mechanical robustness, which are critical for alloy material-based electrode and overall cell integrity.