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

• Published in: Electrochimica acta 2022-11, Vol.433, p.141247, Article 141247
• Main Authors: Zhang, Zhiqiang, Xia, Qiuyu, Chen, Yunkai, Pan, Xuexue, Pameté, Emmanuel, Zhang, Yong, Presser, Volker, Abbas, Qamar, Chen, Xinman
• Format: Article
• Language: English
• Subjects: Composite nanomaterial; Flexible electrodes; Gel polymer electrolyte; Graphene/cobalt hydroxide/Ni electrode; Micro-supercapacitors
• ISSN: 0013-4686; 1873-3859
• DOI: 10.1016/j.electacta.2022.141247

•Graphene/Co(OH)2/Ni electrode was synthesized by two-step electrodeposition.•Specific capacity of graphene/Co(OH)2/Ni electrode is 177 μAh cm−2 at 2 mA cm−2.•Hybrid MSC manifests remarkable energy density and excellent flexibility. 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 hydroxide 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 exhibits the oxidation of Co2+ to Co3+ dedicated to the OH- ion insertion. Furthermore, graphene/cobalt hydroxide/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° 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. [Display omitted]