Multidimensional Branched Composite Binder via Covalent Grafting for High-Performance Silicon-Based Anodes

A binder plays an essential role in preserving the mechanical stability of electrodes and in enhancing the cycle life of Si anodes. Nevertheless, the typical binders normally are not effective enough to relieve the unavoidable volume expansion of Si during cycling. Herein, to make full use of the polar functional groups on the polymer backbone, the citric acid-grafted poly(acrylic acid) (CA-g-PAA) composite binder is rationally designed and prepared by a simple graft modification. The CA molecule not only provides more reactive groups but also connects with PAA to form a multidimensional branched structure. Due to the interaction of CA and PAA, the proposed binder (CA-g-PAA) demonstrates enhanced adhesion strength. Thus, the CA-g-PAA/Si electrode retains a high discharge specific capacity of 2482.3 mAh g–1 after 300 cycles at 840 mA g–1 and exhibits a better structural integrity. This study highlights the synergistic interaction of CA and PAA with Si particles and offers a simple path for the design of optimized binders.