A facile chemical reduction method for preparation of CoNiB was designed and developed. The obtained products showed outstanding electrochemical performances as positive electrode materials in aqueous electrolytes at different current densities (from 1 A g−1 to 20 A g−1). CoNiB nanocomposite exhibited reversible specific capacity of 319.4 mAh g−1, remarkable rate capability over 90% at 20 A g−1, and excellent cyclability with no obvious decay over 100 cycles. The high surface area of CoNiB facilitated the mass and charge transfer, which, in turn, boosted the electrochemical performances.