Carbon-based Fiber Supercapacitors: Design, Construction And Electrochemical Performance

Conventional energy storage device is hard to meet the application requirements of lightweight,flexibility and integrability,which is the mainstream development of next generation devices.Fiber-shaped supercapacitors?FSCs?with unique one-dimensional fiber electrodes,can satisfy the miniaturization,integration and flexibility requirements of wearable devices in practical applications.However,the relatively low capacitance makes it difficult to meet the requirements of high-energy density of flexible devices.Normally,fiber electrodes are constructed with electrochemically active materials and fibrous supports.One common approach is to coat redox-active materials on carbonaceous materials to combine the electric double layer capacitance and the pseudocapacitance.This paper designs and builts activated carbon fibers?ACF?multifunctional templates to construct MnO₂@ACF and MnO₂@Ink/ACF fiber electrodes and devices.And the main results are as follows:ACFs are used as flexible substrates to load MnO₂ materials by KMnO₄ etching for high-energy FSCs.The content of MnO₂ in fiber electrodes is optimized to endow the FSCs with high specific capacitance.By using carboxymethyl cellulose?CMC?/Na₂SO₄ gel electrolyte,highly flexible FSCs are fabricated.And the assembled device exhibits a maximum capacitance of 410 mF cm^-2 at 0.1 mA cm^-2.However,relatively compact structure makes low utilization of MnO₂ materials and poor rate performance of devices.To overcome above problems,commercial ink carbon decorated ACF multi-level substrate?Ink/ACF?is fabricated and MnO₂@Ink/ACF composite fiber electrodes are obtained after KMnO₄ etching.The loose porous structure with a higher surface area of MnO₂ benefits the utilization efficiency of MnO₂.Therefore,the device exhibits ultrahigh capacitance of 649 mF cm^-2 at 0.1 mA cm^-2,1.58 times higher than MnO₂@ACF,with excellent rate performance.From 0.1 mA cm^-2 to 1.0 mA cm^-2,the capacitance retention increased from 35%to 63%.