Pectic Acid-Derived Biobased Poly(ionic liquid) Binder for High-Performance Lithium-Ion Battery Anodes

This study utilizes 1-allyl-3-methylimidazolium chloride ([AMIm][Cl]) for ion exchange to obtain [AMIm][OH], which subsequently reacts with polygalacturonic acid (pectic acid) to synthesize a water-soluble poly(ionic liquid) (PIL) binder intended for application in graphite anodes within lithium-ion batteries. The objective is to supplant poly(vinylidene fluoride) (PVDF), a binder known for its adverse environmental effects. Through mechanical testing and a series of electrochemical characterizations, the results demonstrate the superior performance of the synthesized binder, [AMIm][Pectate], in comparison to commercial PVDF. Notably, the peeling force of the [AMIm][Pectate]-based anode registered at 11.1 N, surpassing that of the PVDF-based counterpart at 10.3 N. Also, under the influence of solid electrolyte interface (SEI) formation, lithium-ion (Li+) transport within [AMIm][Pectate]-based anode cells was accelerated, attributable to reduced charge transfer resistance, decreased SEI resistance, and lower activation energy of lithiation. This is underscored by enhancement in the specific capacity of the [AMIm][Pectate]-based half-cell, achieving 239.8 mAh/g, in contrast to the highest specific capacity attained by PVDF, 208 mAh/g. Even after 1000 cycles at 1C, the capacity retention of the [AMIm][Pectate]-based cell reached 76.4%, surpassing that of PVDF (63.4%). Moreover, scanning electron microscopy analysis provides compelling evidence of the [AMIm][Pectate] binder’s effectiveness in binding conductive and active materials within anodes. This strong adhesion ensures structural integrity and stability throughout Li+ intercalation and deintercalation processes, preventing electrode degradation and enhancing the long-term cycling performance.