Ni film decorated on Au-Ag alloy line to enhance graphene/cobalt hydroxide electrodes for micro-supercapacitors

A nanocomposite of graphene, cobalt hydroxide and nickel can conveniently be synthesized on gold-silver alloy lines. Using a two-step electrodeposition method, the scaly morphology is pre-deposited on a Ni film, followed by the interconnecting corrugated graphene/cobalt hydroxide composite nanomaterial. Due to the pre-deposited Ni film, the area capacity of the graphene/cobalt hydroxide/Ni electrode is 1.6-times of the graphene/cobalt hy-droxide electrode. The kinetic analysis of the graphene/cobalt hydroxide/Ni electrode displays diffusion and non-diffusion contributions of 38% and 62% at 10 mV s-1, respectively. X-ray photoelectron spectroscopy ex-hibits the oxidation of Co2+ to Co3+ dedicated to the OH- ion insertion. Furthermore, graphene/cobalt hy-droxide/Ni//activated carbon flexible micro-supercapacitor (MSC) was assembled by gel KOH-PVA electrolyte, graphene/cobalt hydroxide/Ni (positive electrode), and activated carbon (negative electrode), which manifests maximum volumetric energy of 18.6 mWh cm-3. Moreover, MSC retains over 94% capacitance after 10,000 cycles. After 1,000 continuous bending/unbending cycles at a 180 degrees bending angle with the frequency of 100 mHz, the capacitance retention of MSC is still maintained at 97% of the initial value. The results show outstanding flexibility and mechanical stability of MSC based on graphene/cobalt hydroxide/Ni electrode and confirm that further chemical and physical optimization may lead to the development of quasi-solid-state hybrid MSCs.

Automated summary

A nanocomposite of graphene, cobalt hydroxide, and nickel with a large specific surface area and improved diffusion performance can be conveniently synthesized on gold-silver alloy lines. This electrode exhibits enhanced capacity and cycling stability, showing potential for the development of high-performance micro-supercapacitors.