Enhanced electrochemical performance of cyclized PAN-based tetrazole-mediated PEG-crosslinked binder for high-performance silicon anodes

Abstract

Si, a promising alternative to graphite, a widely used anode material, exhibits a capacity over tenfold higher (4200 mAh g⁻¹) than that of graphite. However, its low conductivity, combined with the intrinsic resistance of the electrode, makes it challenging to fully utilize its theoretical capacity. Moreover, the repeated volume expansion of Si during charge and discharge cycles adversely affects electrode stability, a key barrier to commercializing Si anodes. In this study, bis(azide)-polyethylene glycol (PEG) is used as a crosslinking agent in polyacrylonitrile (PAN). A 3D network structure is generated via thermally induced cyclization and click reactions, yielding the cyclized PAN-based PEG-crosslinked x-cPAN-PEG. The binder exhibits high electronic and ionic conductivity and enhances adhesion to Si compared with the cyclized PAN (cPAN) binder. The crosslinked structure of x-cPAN-PEG also leads to excellent mechanical properties. The electrodes using 350-nm Si and x-cPAN-PEG demonstrates a high initial coulombic efficiency (ICE) of 88 %, with an initial capacity of 4276.9 mAh g⁻¹. Notably, the capacity retention is 70 % after 100 cycles. Furthermore, Si/C composite electrodes using 2-μm Si and x-cPAN-PEG shows much higher capacity retention of 64.6 % after 350 cycles, confirming a superior cell performance compared to CMC/SBR, a commercial binder.