One-step synthesis of amino acid-derived HTC/NiO/Ni(OH)2@Ni cathode for high performance supercapacitors

Abstract

Binder-free nano-sized structure composed of pseudocapacitive materials covered by carbon is concerned to be the next-generation electrode for supercapacitor due to the avoidance of binder and additional electrode preparation, high capacitance of the pseudocapacitive materials, and high conductivity of carbon. Here, a serial of amino acids chosen as hydrothermal carbon (HTC) source were loaded on conductive substrate surface of Ni foam (NF), which constructed binder-free electrodes by a one-step hydrothermal process. Because of its weak oxidative and acid properties, an in-situ redox reaction occurred in the existence of L-glutamic acid, in which Ni is also simultaneously converted into nanostructured NiO/Ni(OH)2 (HTC/NiO/Ni(OH)2@NF). It is discovered that HTC/NiO/Ni(OH)2@NF electrode derived from L-glutamic acid at 2 g L-1 and 160 °C exhibited a battery-like behavior and superior charge/discharge performances, i.e., a specific capacitance of 2586 F g−1 (1293 C g−1) at 2.8 A g−1, and an excellent stability of 91.30% retention after 20,000 cycles.