Chemists from St Petersburg University develop an electrode system to manufacture organic batteries

Scientists from St Petersburg University, as part of an international team of researchers, have developed an electrode system that will help to gain a deeper insight into the properties of various materials. In future, it is expected to help scientists to develop organic batteries that are safe analogues of lithium-ion batteries.

Electrochemical cell
Electrochemical cell

Today, traditional lithium batteries are used everywhere: in laptops, cell phones, and cameras to name just a few. However, these batteries are produced by using heavy metals such as nickel or cobalt. These metals, when disposed, enter the soil and groundwater and pollute the environment. Additionally, metals can accumulate in the human body and lead to intoxication. At the same time, resources for the manufacture of lithium batteries are limited, and every year ore deposits around the world are depleted.

The project is supported by the grant from the Russian Science Foundation. The research findings are published in the journal Energy & Environmental Science.

An international team of scientists, which included chemists from the research group "Organic Electrode Materials for Chemical Power Sources" at St Petersburg University, has developed an electrode system to study various polymers using electron paramagnetic resonance (EPR). The EPR method is used to determine the presence of radicals and ongoing redox reactions in the structure of the active electrode. Additionally, this method can be used to analyse properties of the active electrode and develop strategies to increase its efficiency. This makes it possible to choose the substances that are most suitable for creating organic batteries. When it comes to efficiency, these organic batteries are superior to lithium-ion technologies. The method can also detect changes in the film and detect inactive centres that can reduce the efficiency of the battery.

At the Berlin Joint EPR lab (BeJEL), the chemists conducted experiments on the p-DiTS film. The film is quite stable due to the fragments of the heterocyclic radical TEMPO (2,2,6,6-tetramethylpiperidin-1-yl)oxyl). However, it substantially loses its activity after 36 redox cycles of reactions. This is due to the fact that regions of electrochemically inactive particles are formed on the film. This, in turn, leads to deterioration in conductivity.

The developed electrode system makes it possible for us to study and understand how such "empty" areas are formed on the film. By doing so, we can chemically change the structure of the polymer in order to eventually obtain a material with high capacity and stability.

Oleg Levin, Principal Investigator and Professor in the Department of Electrochemistry at St Petersburg University

Conducting polymers that contain nitroxyl radicals can serve as prominent electrode materials. They work on redox reactions. In other words, when discharged, the radical is oxidised to a positive cation, and when charged, it is restored back. This increases the energy efficiency of the battery. The prototypes of batteries based on nitroxide radicals have already been developed. They can be charged in seconds. However, their energy is still half that of lithium-ion systems.

’At the moment, the development of methods for efficient and safe storage of electricity is much up to date. The results of our work will help facilitate the production of organic batteries that do not contain heavy metals. They will be quite efficient in operation; safe to use; and easy to dispose together with household waste,’ said Oleg Levin, Professor in the Department of Electrochemistry at St Petersburg University.