A Four-Armed Polyacrylic Acid Homopolymer Binder with Enhanced Performance for SiOx/Graphite Anode

The large-scale application of Si-based anodes is impeded by their fast capacity decay, which is mainly attributed to the huge volume expansion upon cycling. The employment of functional binders is one efficient method to mitigate this issue. In this work, a four-armed polyacrylic acid (4A-PAA) homopolymer is explored as a remarkably effective binder for Si-based anodes. The 4A-PAA binder is prepared via an atom transfer radical polymerization, followed by ester hydrolysis. Compared to the conventional linear polyacrylic acid (PAA) binder, the 4A-PAA not only shows enhanced toughness due to its decreased molecular regularity and intramolecular hydrogen bond but also exhibits increased binding strength because of its multidimensional binding structure. As a result, the SiO/graphite electrode using the 4A-PAA retains a capacity retention of 89.1% and a capacity of 558.1 mAh g after 200 cycles at 0.16 A g, which are superior to the PAA electrode, corresponding to 80.4% and 469.3 mAh g, respectively. The improved performance is attributed to the employment of the 4A-PAA, which mitigates the volume change of the SiO/graphite anode. This work not only offers a promising binder for Si-based anodes but also presents a universal solution for other anodes with high volume expansion during cycling.