3D printed supercapacitor electrode, performance and stability are stronger than ever
Time：2020.08.07
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In addition to batteries, there are many ways to store electricity in the world. For example, super capacitors that have been in full swing in recent years are one of them. Now, American scientists use 3D printing to make graphene aerogel. The 3D porous capacitor electrode with greatly improved performance can store more charge per unit than previous research.
Super capacitors are power storage devices between traditional capacitors and batteries. Although they have lower storage capacity compared to batteries, they have the advantages of fast charging speed, long life, high temperature and high pressure resistance, and high safety. The density is higher than the general capacitance, and the power density is also better than other batteries.
The storage methods of supercapacitors are divided into two types, namely electric double layer capacitors and pseudocapacitors (pseudocapacitor, also known as pseudocapacitors). The former uses high surface area carbon materials as electrodes, and the electrode materials are only used to absorb charge, and It does not react with the electrolyte. The latter uses the electrochemical reaction between the electrode surface and the electrolyte to store electricity. The power storage method is similar to that of existing batteries.
Among them, the University of California Santa Cruz (UCSC) and Lawrence Livermore National Laboratory (LLNL) have always wanted to use 3D printed graphene aerogel to create pseudo-capacitor electrodes, but this is not a simple matter. Yat Li, a professor at the Department of Chemistry and Biochemistry at UCSC, said that the current challenge is that when the thickness of the electrode increases, the ion diffusion rate of the overall structure will decrease, which will affect the performance of the capacitor, so the team has to increase the pseudo-capacitance without affecting the storage capacity. Mass loading of materials.
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(Source: UCSC)
To this end, the team used 3D printed graphene aerogel to create a porous scaffold, and then filled it with manganese oxide, a common material for pseudo-capacitors, to successfully achieve a breakthrough in capacitor mass loading.
In the past, the manganese oxide content of the pseudo-capacitance electrode was 10 mg per square centimeter, while the new electrode can increase the content to 100 mg without affecting performance. The experiment indicates that although the area of the capacitor will increase with the increase of the manganese oxide content and the thickness of the electrode, the volume of the capacitor has hardly changed, which means that even if the mass load of the capacitor is increased, the ion diffusion rate has not decreased.
UCSC graduate student Bin Yao said that in the traditional supercapacitor process, because the thickness of the electrode coating will affect performance, manufacturers use very thin coatings and metals to create current collectors, and then use a layer-by-layer stack to manufacture capacitors. Only this will increase the weight and cost.
If the new research of the team can be used to skip the stacking process, the porous graphene aerogel lattice electrode designed by the researchers, in addition to allowing the uniform deposition of manganese oxide materials and effectively improving the ion diffusion efficiency of charge and discharge, the new method can also be used in Increase the electrode thickness to 4mm with reduced performance.
According to Yat Li, experimental tests indicate that the amount of stored charge per unit of the new capacitive electrode has exceeded previous research. The main innovation of this research is that the electrode structure can be manufactured by 3D printing, and the stability of the new electrode is also very high. The capacity can still be maintained at 90% after 20,000 charge and discharge cycles. The 3D printed graphene gas condenses The flexibility of the design of the glue electrode is also very high, and it can even be printed in any shape, which is expected to improve the scope of application of supercapacitors. The team has published the research in "Joule".
