As a widely concerned material for supercapacitors, nickel cobalt layered double hydroxides (NiCo-LDHs) often suffer from the inferior rate capability and cycling stability due to the low electrical conductivity and easy agglomeration. To address these shortcomings, a simple in-situ hydrolysis approach is successfully developed to construct a binder-free system consisting of acetate anion-intercalated nickel cobalt layered double hydroxides (A-NiCo-LDHs) and Ni foam (NF) without additional alkali sources. The resulting A-NiCoLDH/NF electrodes exhibited obviously enhanced capacitive properties owing to the unique nanostructure and strong synergistic effects. It is worth noting that the optimized A-Ni5Co5-LDH/NF electrode delivered the highest performance among the electrodes studied, including ultrahigh specific capacitance (2445 Fg(-1) at 0.5 Ag-1) and superior rate capability (1644 Fg(-1) and 1383 Fg(-1) at 20 Ag-1 and 50 Ag-1, respectively), as well as satisfactory long-term endurance (similar to 93% capacitance retention after 10,000 cycles at 20 Ag-1). The attractive performances and facile fabrication make the A-Ni5Co5-LDH/NF system a promising candidate for low-cost high-performance energy storage devices. (C) 2017 Elsevier Ltd. All rights reserved.