In ‘3D Architecture Electrodes for Energy Storage Applications,’ Seonghyeon Park explores the demand for harnessing and keeping energy, and especially on the micro-scale. Although micro-scale devices have been created for smaller electronics, there are challenges because of low material loading per unit area on the substrate. Park sees 3D printed electrodes, bearing a high aspect ratio and porous architecture, as a solution to this problem, leading to better performance overall—and higher customer satisfaction globally.
The actual production processes to make simple 3D electronics have been fraught with problems such as expense, complications in manufacturing, lack of efficiency, toxicity from etching materials, and more. With DLP printing, many of the issues are overcome as it requires no supports, is affordable, and production is expedient.
“With these benefits, DLP printing proved to be a promising method to fabricate 3D electrodes. One of the main reasons why DLP printing is not reported much for producing 3D electrodes is the limitation of material, which is related to the mechanism of DLP printing,” states the author.
“DLP printing utilizes UV light to cure liquid resin consisting of a monomer, oligomer, and photo-initiator, and the irradiated pattern is polymerized, which converts shorter chain (monomer) into longer cross-linked chain (polymer), forming a 3D network by free radical polymerization. However, these resin materials are not usually conductive, and the final products are nonconductive polymers. Therefore, conductive materials for DLP printing have been required to print the electrodes. As an approach to develop a conductive 3D structure, composite materials which have a combination of resin and conductive fillers have been introduced. Silver nitrate (AgNO3) with polyethylene glycol diacrylate (PEGDA)- based composite resin [17] (500 KΩ) and multiwall carbon nanotubes (MWCNTs) with acrylic resin (2.7 × 10−2 S/m) [18] (4 × 10−6 S/m) [19] have been reported. Despite all these efforts, these electrical resistances are too high, or the conductivities are too low to use as a 3D electrode for supercapacitors.”
Schematic of charge storage via the process of either (a) electrochemical double-layer capacitance or (b) pseudo-capacitance [20]. Reprinted with permission in “Architecture Electrodes for Energy Storage Applications.”
- Increase active material loading in unit area with minimum performance loss,
- Timesaving, cost-effective manufacturing in ambient operation environment
- Realization of tailorable complex electrode designs which can increase surface area or mechanical stability.
- Adjustment of porosity by 3D design for electrolyte diffusion.
Park points out that pseudo-capacitors have been created to enhance micro-supercapacitors (MSCs) but these materials must be able to handle both ionic and electronic currents. Researchers are using 3D nanostructured materials to overcome current issues, introducing material from nanoparticles to nanoflowers. The energy density of the MSCs could also increase due to the nanostructures. 2D printed MSCs have also been introduced to increase the voltage of electrodes as they are connected by computer design.
Design of 2D to 3D electrodes on current collector: (a) Thick film, (b) Nanostructured material, (c) nanostructured material + additive, (d) Graphene sheet with active material, (e) 3D monolithic electrode, (f) 3D monolithic current collector with active material.
“Extrusion printing (EP), or direct ink writing (DIW), is one of the most promising 3D printing methods with numerous advantages such as flexibility of material selection, low cost, simple printing process without post process,” states Park. “The flexibility of material selection on MSCs electrodes could be more emphasized because various materials having high surface area such as CNT, graphene and pseudo material also can be used.”
Clogging has been a major problem in 3D printing electrodes, however, disrupting the fabrication of parts. Park sees aerosol jet printing as a possible method that would improve on this issue, and 3D printed electrodes for micro-batteries have been created with success.
“The conductive 3D hierarchical structures also could be applied in MSCs electrodes,” states Park. “The high surface area from hierarchical structure increases the capacitance of MSCs by having higher EDLC and vigorous electrochemical reaction. The high conductivity can also transport the electrons effectively.”
Ultimately, Park determined that the customization of 3D printed electrodes is possible when they are made of complex truss structures.
“The truss design contributes to durable property while it is pyrolyzed, resulting in maintaining its structures,” states Park.
“It is achievable to reduce size of electrode structure by high resolution DLP printer and pyrolysis method, generating hierarchical macroporous framework which can have high surface area and ideal size for electrolyte diffusion and its electrochemical performance can be significantly enhanced by deposition of electrochemical active materials,” concluded Park.
While it may be an overstatement to say that consumers around the world are obsessed with energy, it is certainly a continual consideration. Batteries, charging of devices, and the ongoing need to harness and store energy for countless needs lend themselves to a huge industry, and one that 3D printing is offering benefit to, from embedded batteries made from PLA to electrodes for use in light beam splitting, and in creating improved microfluidics. What do you think of this news? Let us know your thoughts; join the discussion of this and other 3D printing topics at 3DPrintBoard.com.
Directly Written MSCs: Extrusion printing with (a) reduced graphene oxide
[53], (b) CNT [55], (c) graphene/PANI [56], (d) V2O5 + GO, G–VNQDs + GO, LiCl with PVA. (e) Aerosol jet printing (AJP) with Ag nanoparticle [61]. Reprinted with permission in “Architecture Electrodes for Energy Storage Applications.”