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  • 2.2 V wearable asymmetric s...
    Deng, Ming-Jay; Wu, Yu-Syuan

    Journal of alloys and compounds, 06/2023, Letnik: 945
    Journal Article

    In this study, redox-active polyvinyl alcohol (PVA)-KOH-urea-LiClO4 alkaline gel electrolyte was prepared and used to assemble a Co oxide//Mn oxide wearable asymmetric supercapacitor (WASC). This experiment was achieved by choosing a deep eutectic solvent, urea-LiClO4, as the redox additive and aid a broad operating voltage, alongside an alkaline KOH-PVA gel to enhance redox performance and as plasticizer. The nanoporous Co oxide and Mn oxide electrodes were prepared using electroplating. The Co oxide//Mn oxide WASC with a PVA-KOH-urea-LiClO4 gel electrolyte can operate with an output voltage of 2.2 V and produce a high energy density of 125 Wh/kg at 2200 W/kg. The WASC showed good performance (186 F/g at 2 A/g) and 89.5% capacitance retention after 6000 charging/discharging cycles. Additionally, the WASC can maintain its electrochemical performance at various bending angles. Studied as the WASC electrode, in-situ/operando X-ray absorption near-edge spectroscopy revealed that the Co oxide suffers a reversible oxidation state-alteration reaction related to the redox pseudocapacitance reaction in PVA-KOH-urea-LiClO4. To show real life application, the WASCs were successfully applied to power a light-emitting diode and a digital watch. •Nanoporous Co oxide and Mn oxide electrodes were prepared.•A redox-active PVA-KOH-urea-LiClO4 alkaline gel electrolyte was designed to improve operating voltage and pseudocapacitance.•Co-NCC//Mn-NCC WASCs exhibit high energy density of 125 Wh/kg at 2200 W/kg.•In-situ/operando XANES was used to identify the chemical state shift during charge-discharge cycling.