Synthesis of Co–Ni oxide microflowers as a superior anode for hybrid supercapacitors with ultralong cycle life

Abstract

Li-ion hybrid capacitors (LIHCs), composing of a lithium-ion battery (LIB) type anode and a supercapacitor (SC) type cathode, gained worldwide popularity due to harmonious integrating the virtues of high energy density of LIBs with high power density of SCs. Herein, nanoflakes composed microflower-like Co–Ni oxide (CoNiO) was successfully synthesized by a simple co-precipitation method. The atomic ratio of as-synthesized CoNiO is determined to be 1:3 through XRD and XPS analytical method. As a typical battery-type material, CoNiO and capacitor-type activated polyaniline-derived carbon (APDC) were used to assemble LIHCs as the anode and cathode materials, respectively. As a result, when an optimized mass ratio of CoNiO and APDC was 1:2, CoNiO//APDC LIHC could deliver a maximum energy density of 143Whkg−1 at a working voltage of 1–4V. It is worth mentioning that the LIHC also exhibits excellent cycle stability with the capacitance retention of ∼78.2% after 15,000 cycles at a current density of 0.5Ag−1.