Gennady Detinich
Recently in the magazine Science came out article authors from the McKelvey School of Engineering at Washington University in St. Louis, which is dedicated to the study of heterogeneous thin film structures for capacitors. Working with ferroelectrics, scientists accidentally created a capacitor with an energy density 19 times higher than the density of conventional elements. In fact, they developed a battery with exceptional fast charging capabilities, which today’s batteries do not have.
Image source: Sang-Hoon Bae
It’s no secret that capacitors are the most important elements of power supply subsystems and circuit stability. Today’s smartphones can have up to 500 capacitors, and laptops can have up to 800 or more (we’ll leave oscillatory circuits out of brackets in this article, we’re just talking about power supply). In all cases, capacitors work as elements that can be quickly discharged and charged, which cannot be said about batteries. But batteries have the highest energy storage density. Scientists have been trying to find a middle ground for a long time – a high-density battery with the ability to charge and discharge quickly, but at the same time be intact and capable of many charging cycles. It seems that scientists from the US are closer to finding such a battery.
An experiment with heterostructures based on barium titanate (BaTiO3) – a type of perovskite – discovered “new physics,” as scientists said. In general, the researchers were able to control the discharge (relaxation) time of the ferroelectric device. This ability was gently revealed when they were investigating a combination of 2D and 3D materials in 2D/3D/2D2 or Au/MoS2/BaTiO3/MoS2/Au sandwich combinations. A barium titanate core is surrounded by two atomically thin layers forming a layer just 30 nm thick, or 1/10th the thickness of a normal virus. Carefully chosen chemical and non-chemical bonds, as well as the gaps between the layers, became the key that allowed us to control the discharge time of the capacitor battery.
By maintaining the crystallinity of the 3D ferroelectric and reducing energy loss, the scientists were able to achieve an energy storage density in this heterogeneous multilayer structure of 191.7 J/cm3 with an efficiency higher than 90 %. Precise control of discharge timing opens up opportunities for a wide range of applications and could accelerate the development of highly efficient energy storage systems.
“We have created a new structure based on techniques we have already implemented in our laboratory using 2D materials, said lead author Sang-Hoon Bae. “We weren’t initially focused on energy storage, but during our research into the properties of materials we discovered a new physical phenomenon that we realized could be applied to energy storage, and which was both very interesting and could be much more useful.”
“We discovered that the relaxation time of the dielectric can be controlled or induced by a very small gap in the material’s structure, – Bay explained. “This is a new physical phenomenon – something we haven’t encountered before.” This allows us to manipulate the dielectric material in such a way that it does not polarize and lose its charge capacity.”
Scientists do not hide that there will be a long optimization of the material ahead of us, but even at this stage, development is higher than the performance of other laboratories. Therefore, the researchers see great promise in the “electronic material,” as they called their solution.
