Capacitors with dielectrics, multiplied by 2 the energy density
Rechargeable batteries are not the only efficient devices when it comes to mobile storage. One of the most promising alternative technologies in this field is represented by capacitors with dielectrics. What is it? Of components that store electrostatic energy by polarization and are composed of two metal electrodes (the armatures) separated by insulating material (a dielectric film). Operation is simple: when applying an electrical voltage to the armatures, the charges separate – the positive ones are attracted towards the negative electrode and the negative ones towards the positive electrode – polarizing the dielectric.
Compared to batteries, these devices have much higher power densities, offer fast charging and discharge times and do not undergo electrolyte degradation phenomena. But if they have not yet depopulated in the field of energy storage there is a reason. The energy density of the current dielectrics, that is, the amount of energy they are able to store, cannot be compared with that of rechargeable batteries.
A nanoscale approach
Today, a research group from Nagoya University in Japan in collaboration with the National Institute for Materials Science is helping the sector. The scientists, led by Professor Minoru Osada, have developed a nanostructured capacitors with the highest accumulation performance ever achieved.
Because the energy stored in dielectric capacitors is related to polarization, the key to increasing energy density is to apply the highest possible electric field to a material with a high dielectric constant. However, current insulators have limitations in the ability to manage such fields. To overcome the problem, the group used layers of calcium, sodium, niobium and oxygen nanosheets with a perovskite crystal structure, which offers excellent dielectric properties such as high polarization.
“We discovered – Osada explained – that by using this property, we can apply a high electric field to dielectric materials with high polarization, converting it into electrostatic energy without losses and reaching the highest energy density ever registered”. The results of the research group confirmed that capacitors with nanosheet dielectrics achieve a higher energy density of 1-2 orders of magnitude while maintaining the same high output density, The research was published in Nano Letters.