Due to its capacity to manufacture low-cost 3D-printed structures, 3D-printing technology offers a unique opportunity for the fast epitome of various applications. Using a typical fused deposition modeling 3D printer along with a Discovery extruder, a graphene-ink can be 3D printed to produce an interdigitated electrode (IDE) arrangement. This work fabricated a 3D-printed planar supercapacitor from pristine graphene-ink without using high-temperature processing or functional additives. The printable ink (89%) is formulated from pristine graphene without the addition of any functional additives. The symmetric flexible supercapacitor is demonstrated with an excellent specific capacitance of 137.50 F/g at 0.5 A/g and an energy density of 12.23 Wh/kg. The obtained gravimetric energy density beats reported earlier carbon-based supercapacitors that are 3D or inkjet printed. The flexibility and robustness of 3D-printed devices are achieved up to 150° folding angles. This work demonstrates an efficient and easy method for fabricating practical energy storage devices featuring a customizable shape and excellent flexibility.

Conductive carbon cloths (CCs) have been great attention as a promising current collector for flexible supercapacitors that supply power to portable and wearable electronics. However, the hydrophobic surface and weak adhesion with active materials has limited to be adopted as the binder-free and flexible electrode with mechanical/electrochemical stability. In this work, we demonstrate preparation of binder-free and flexible electrodes based on polyaniline (PANI) on carbon cloth. Polydopamine (PDA) layer are used to impart hydrophilicity, leading to uniform growth of PANI on the hydrophobic surface of carbon. Furthermore, PDA layer improves adhesion strength between PANI and carbon substrates, which allows for superior mechanical stability under ultrasonic condition. PANI-based flexible electrode shows high areal capacitance (160.8 mF cm− 2 at 0.5 mA cm− 2), good rate capability (71.1% even at high current density of 10 mA cm− 2), and long-term cycling stability (82.6% capacitance retention after 1500 cycles). Furthermore, a quasi-solid-state flexible supercapacitor reveals remarkable mechanical flexibility and durability, with superior capacitance retention (~ 100%) in bent state and after repetitive 1000 cycles.

Vertically Aligned Carbon Nanotubes (VACNTs)-coated flexible aluminium (Al) foil is studied as an electrode for supercapacitor applications. VACNTs are grown on Al foil inside thermal Chemical Vapor Deposition (CVD) reactor. 20 nm thick layer of Fe is used as a catalyst while Ar, H2 and C2H2 are used as precursor gases. The effect of growth temperature on the structure of CNTs is studied by varying the temperature of CVD reactor from 550 °C to 625 °C. Better alignment of VACNTs arrays on Al foil is recorded at 600 °C growth temperature in comparison to other processing temperatures. Cyclic voltammetry results shows that VACNTs-coated Al foil has a specific capacitance of ~ 3.01 F/g at a scan rate of 50 mV/s. The direct growth of VACNT array results in better contact with Al foil and thus low ESR values observed in impedance spectroscopy analysis. This leads to a fast charge–discharge cycle as well as a very high value of power density (187.79 kW/ kg) suitable for high power applications. Moreover, wettability study shows that the fabricated VACNT electrode has a contact angle of more than 152° which signifies that it is a superhydrophobic surface and hence shows lower specific capacitance in comparison to reported values for VACNT array. Therefore, it is necessary to develop suitable post-processing strategies to make VACNTs hydrophilic to realize their full potential in supercapacitor applications.

Free-standing hybridized electrode consisting of double-walled carbon nanotubes (DWNTs) and activated carbon have been fabricated for flexible supercapacitor applications. The xanthan-gum, used in our methodology, showed high ability in dispersing the strongly bundled DWNTs, and was then effectively converted to activated carbon with large surface area via chemical activation. The homogeneously dispersed DWNTs within xanthan-gum derived activated carbon acted as both electrical path and mechanical support of electrode material. The hybridized film from highly dispersed DWNTs and activated carbon was mechanically strong, has high electrical conductivity, and exhibited high specific capacitance of 141.5 F/g at the current density of 100 mV/s. Our hybridized film is highly promising as electrode material for flexible supercapacitors in wearable device.

본 연구에서는 “이온젤” 이라고 불리는 고분자 기반의 PVA(polyvinyl alcohol)-H₃PO₄의 고체 전해질에 이온성 액체 BMIMBF4 (1-buthyl-3-methylimidazolium tetrafluoroborate)를 첨가하여 제조한 전고체 전해질과 환원된 그래핀 옥사이드/전도성 고분자 복합재료 기반의 전극 재료를 이용하여 유연성을 갖는 슈퍼커패시터를 제작 하였으며, 유연성에 따른 전기화학적 특성을 분석하여 보았다. 환원된 그래 핀 옥사이드/전도성 고분자 복합재료와 전고체 전해질 기반의 유연성 슈퍼커패시터의 전기화학적 특성을 유연성에 따라서 측정하기 위해서 프레스로 0.01 kg/cm²의 일정한 압력으로 최대 100회 까지 굽힘 시험 (bending test)을 진행 하였으며, 0~100 회의 굽힘 시험 이후에 순환 전압전류법(CV), 전기화학적 임피던스 분광법(EIS) 및 전정류 충·방전법(GCD)을 통하여 비교 및 분석하여 보았다. 그 결과로, 유연성 슈퍼커 패시터의 초기 전기용량은 43.9 F/g으로 확인 할 수 있었고, 이 값은 50회, 100회의 굽힘 시험 후에 각각 42.0F/g, 40.1F/g로 감소하는 현상을 확인할 수 있었다. 이러한 결과로 미루어 보아 물리적인 응력이 슈퍼 커패시터의 전기화학적 특성 감소에 영향을 주는 것으로 사료되며 또한, 굽힘 횟수에 따른 슈퍼커패시터의 전기화학적 특성 감소 원인을 확인하기 위해서 굽힘 시험 전과 후의 전극표면을 전자주사 현미경으로 관찰 하여 보았다.