3D Printed Supercapacitor Exploiting PEDOT-Based Resin and Polymer Gel Electrolyte.

Renewable energy-based technologies and increasing IoT (Internet of Things) objects population necessarily require proper energy storage devices to exist. In the view of customized and portable devices, Additive Manufacturing (AM) techniques offer the possibility to fabricate 2D to 3D features for functional applications. Among the different AM techniques extensively explored to produce energy storage devices, direct ink writing is one of the most investigated, despite the poor achievable resolution. Herein, we present the development and characterization of an innovative resin which can be employed in a micrometric precision stereolithography (SL) 3D printing process for the fabrication of a supercapacitor (SC). Poly(3,4-ethylenedioxythiophene) (PEDOT), a conductive polymer, was mixed with poly(ethylene glycol) diacrylate (PEGDA), to get a printable and UV curable conductive composite material. The 3D printed electrodes were electrically and electrochemically investigated in an interdigitated device architecture. The electrical conductivity of the resin falls within the range of conductive polymers with 200 mS/cm and the 0.68 µWh/cm2 printed device energy density falls within the literature range.

Tragacanth Gum as Green Binder for Sustainable Water-Processable Electrochemical Capacitor.

Enabling green fabrication processes for energy storage devices is becoming a key aspect in order to achieve a sustainable fabrication cycle. Here, the focus was on the exploitation of the tragacanth gum, an exudated gum like arabic and karaya gums, as green binder for the preparation of carbon-based materials for electrochemical capacitors. The electrochemical performance of tragacanth (TRGC)-based electrodes was thoroughly investigated and compared with another water-soluble binder largely used in this field, sodium-carboxymethyl cellulose (CMC). Apart from the higher sustainability both in production and processing, TRGC exhibited a lower impact on the obstruction of pores in the final active material film with respect to CMC, allowing for more available surface area. This directly impacted the electrochemical performance, resulting in a higher specific capacitance and better rate capability. Moreover, the TRGC-based supercapacitor showed a superior thermal stability compared with CMC, with a capacity retention of about 80 % after 10000 cycles at 70 °C.

PDMS/Polyimide Composite as an Elastomeric Substrate for Multifunctional Laser-Induced Graphene Electrodes.

Laser-induced graphene (LIG) emerged as one of the most promising materials for flexible functional devices. However, the attempts to obtain LIG onto elastomeric substrates never succeed, hindering its full exploitation for stretchable electronics. Herein, a novel polymeric composite is reported as a starting material for the fabrication of graphene-based electrodes by direct laser writing. A polyimide (PI) powder is dispersed into the poly(dimethylsiloxane) (PDMS) matrix to achieve an easily processable and functional elastomeric substrate, allowing the conversion of the polymeric surface into laser-induced graphene (LIG). The mechanical and electrical properties of the proposed material can be easily tuned by acting on the polyimide powder concentration. The reported procedure takes advantage from the simple casting process, typical of silicone elastomer, allowing to produce electrodes conformable to any kind of shape and surface as well as complex three-dimensional structures. Electrochemical capacitors and strain gauges are selected as flexible prototypes to demonstrate the multifunctional properties of the obtained LIG on the PDMS/PI composite substrate.