Hérou Servann, Bailey Josh J, Kok Matt, Schlee Philipp, Jervis Rhodri, Brett Dan J L, Shearing Paul R, Ribadeneyra Maria Crespo, Titirici Magdalena
Department of Chemical Engineering, Imperial College Road, Kensington, London, SW7 2AZ, UK.
Electrochemical Innovation Lab, Department of Chemical Engineering, UCL, London, WC1E 7JE, UK.
Adv Sci (Weinh). 2021 Sep;8(17):e2100016. doi: 10.1002/advs.202100016. Epub 2021 May 20.
Supercapacitors are increasingly used in short-distance electric transportation due to their long lifetime (≈15 years) and fast charging capability (>10 A g ). To improve their market penetration, while minimizing onboard weight and maximizing space-efficiency, materials costs must be reduced (<10 $ kg ) and the volumetric energy-density increased (>8 Wh L ). Carbon nanofibers display good gravimetric capacitance, yet their marketability is hindered by their low density (0.05-0.1 g cm ). Here, the authors increase the packing density of low-cost, free-standing carbon nanofiber mats (from 0.1 to 0.6 g cm ) through uniaxial compression. X-ray computed tomography reveals that densification occurs by reducing the inter-fiber pore size (from 1-5 µm to 0.2-0.5 µm), which are not involved in double-layer capacitance. The improved packing density is directly proportional to the volumetric performances of the device, which reaches a volumetric capacitance of 130 F cm and energy density of 6 Wh L at 0.1 A g using a loading of 3 mg cm . The results outperform most commercial and lab-scale porous carbons synthesized from bioresources (50-100 F cm , 1-3 Wh L using 10 mg cm ) and contribute to the scalable design of sustainable electrodes with minimal 'dead volume' for efficient supercapacitors.
超级电容器因其长寿命（约15年）和快速充电能力（>10 A g）而越来越多地用于短距离电动运输。为了提高其市场渗透率，在尽量减少车载重量并最大化空间效率的同时，必须降低材料成本（<10美元/千克）并提高体积能量密度（>8 Wh/L）。碳纳米纤维具有良好的重量电容，但其市场适用性受到其低密度（0.05 - 0.1 g/cm³）的阻碍。在此，作者通过单轴压缩提高了低成本、自支撑碳纳米纤维垫的堆积密度（从0.1 g/cm³提高到0.6 g/cm³）。X射线计算机断层扫描显示，致密化是通过减小不参与双层电容的纤维间孔径（从1 - 5 µm减小到0.2 - 0.5 µm）实现的。提高后的堆积密度与器件的体积性能直接成正比，在0.1 A/g的电流密度下，使用3 mg/cm²的负载量时，器件的体积电容达到130 F/cm³，能量密度达到6 Wh/L。该结果优于大多数由生物资源合成的商业和实验室规模的多孔碳（使用10 mg/cm²时为50 - 100 F/cm³，1 - 3 Wh/L），并有助于设计具有最小“死体积”的可持续电极的可扩展设计，以实现高效超级电容器。
