The line between batteries and supercapacitors is no longer clear as scientists and engineers name these devices with less consistency. As the lines blurr and thechnology advances we may be moving clocer to a device with the energy density of a battery and charge and discharge characteristics of a capacitor.
This is according to a group of researchers who published their findings in their report called, Science-Where Do Batteries End and Supercapacitors Begin?
Wrong terminology costs research time and money
Energy storage has taken off in the last five to seven years in response to energy supplier and consumer needs.
Much too often, battery materials are called supercapacitors in the scientific literature, unknowingly or perhaps deliberately, says Yury Gogotsi, a materials science and engineering professor at Drexel University. He says that this confusion is not helping the energy storage industry to progress. He explains that attempts to sell a poor quality material as a good one by using wrong terminology is holding back research and often leads to a significant waste of time and finance.
The basics explained
Batteries store charge through a redox reaction, which involves a material giving up electrons and the transport of ions through some other material. So batteries can store a lot of energy but they typically take hours to recharge.
Supercapacitors, also called ultracapacitors, store charge electrostatically on high surface-area electrodes. They store less energy but can charge or discharge in seconds. They are used mostly to provide short bursts of power in buses and cranes and they hold much promise for electric cars and the green grid.
The aim is to create a device that is able to store a significant amount of energy and charge or discharge quickly. Researchers have recently discovered that graphene foam may be able to enhance the supercapacitor’s performance levels by increasing energy density. Their findings are published in Nature Scientific Reports-“Hydrous Ruthenium Oxide Nanoparticles Anchored to Graphene and Carbon Nanotube Hybrid Foam for Supercapacitors”
According to Mr Gogotsi, technology and terminology confusion tend to occur in rapidly growing fields.
Lack of knowledge or deliberate?
In the case of energy storage, one reason for the confusion is that new materials—especially those on the nanoscale—combine the characteristics of the batteries and supercapacitors. This often confuses scientists who have just entered the field.
However, there are those instances where scientists will deliberately sell a battery material as a supercapacitor, according to Mr Gogotsi. As a result, investors may end up investing in battery development instead of supercapacitor development.
Defining the battery and the supercapacitor
The defining character is really the electrical response, explains Mr Gogotsi. A linear change of the electric potential during discharge typically results in a constant current for a supercapacitor, whereas in a battery the current peaks at two specific potentials because of the oxidation (electron loss) and reduction (electron gain) reactions that happen at the electrodes.
Researchers need to look at the material’s electrochemical characteristics and then accurately name the device. Journal editors and reviewers also need to take responsibility for this, explains Mr Gogotsi.