In this study, we modified an attractive water-dispersed poly(acrylonitrile–butylacrylate) binder used for lithium-ion batteries by the addition of highly acidic acrylic acid (AA). The synthesized poly(acrylicacid–acrylonitrile–butylacrylate)–polystyrene polymer showed an improved performance as a binder with smaller particle size, stiffer polymer matrix, higher adhesion strength, and lower contact angle characteristics. Consequently, the modified water-dispersed binder by the addition of AA increased the cyclic capacity and retention of physically mixed silicon/graphite anodes, when compared to the unmodified poly(acrylonitrile–butylacrylate) binder.