- Researchers loaded 3D-printed structures of porous graphene aerogel with manganese oxide.
- This enabled them to capture an ultrahigh energy storage capacity into a small area.
- The energy densities are equivalent to that of some traditional batteries.
Pseudocapacitors are a type of energy storage devices that could effectively balance the requirement of fast charging/discharging and high energy density. To realize practical pseudocapacitors, we need to develop a collector that can concurrently enable efficient electron transport and ion diffusion.
The recent advances in 3D printing technology have offered new ways to address this exceptional challenge for pseudocapacitors. So far, numerous strategies have been employed to enhance the performance of these devices, including defect introduction, crystallinity engineering, and elemental doping.
Recently, a team of researchers at the University of California, Santa Cruz and Lawrence Livermore National Laboratory built 3D-printed supercapacitor electrodes that are far superior to conventional supercapacitors in terms of energy density and performance.
Using Pseudocapacitive Material To Pack More Density
In this work, researchers have shown 3D-printed structures of porous graphene aerogel that can support high volumes of a widely-used pseudocapacitive material, manganese oxide (MnO2). The material is known for chemically storing electric charge and exhibiting an ultrahigh theoretical energy capacity.
This results in a supercapacitor that has high areal capacitance or a massive storage of electric charge per unit area. Until now, no one has been able to achieve this feat. Compared to other capacitors, it has an exceptional energy density. The study could open new doors for using this type of capacitors as fast-charging power sources for devices like mobiles and laptops.
The team loaded the 3D printed porous structures with 180 mg of manganese oxide, using a chemical decomposition technique. Surprisingly, they were able to achieve up to 100 times more loading levels than what others have reached, without degrading performance.
Reference: Cell | doi:10.1016/j.joule.2018.09.020 | LLNL
They added a layer of pseudocapacitive manganese oxide on 3D printed graphene structure to extend the overall energy density and capacitance. Rather than applying a selective coating on the structure’s external surface, they completely utilized its huge surface area.
The Plus Point
What’s more exciting about this project is that it’s still not the limit. Everything is scalable. There’s a lot of accessible macropores – a crucial element for depositing MnO2 and diffusing ions efficiently.
Fabrication of a 3D printed graphene aerogel/MnO2 electrode | Courtesy of researchers
They can make the electrodes thick while retaining decent conductivity and ion diffusion. Typically, if you keep increasing thickness, eventually it will reach a threshold, particularly at high charging rates.
But since researchers have used a 3D structure, they can make a decent utilization of a higher charge. The gravimetric value won’t degrade much, even if they make the structure thicker.
The 3D printed structure has many other advantages. For example, you can control the size of pores, fabricate electrodes rapidly, and configure the parameters the way you want. Also, the porosity can be altered by changing the structure’s architectural design.
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The present work emphasizes on symmetric supercapacitor devices’ performance that relies on two similar 3D-printed electrodes. In the coming years, researchers will use extremely high loading of active materials to build asymmetric devices, which would use two different substance on each electrode, further increasing the levels of energy density and working voltage.
