St Petersburg University students find a way to make energy storage more efficient and affordable

Energy ‘reserve’

One of the major issues of the modern electric power industry is fluctuations in electricity consumption. Due to the fact that it is used more actively during the day than at night, power plants experience abrupt changes in load, which lead to inefficient energy consumption. With the switch to renewable energy sources, the issue of fluctuations in electricity consumption is becoming more serious. Many of these sources prevent from generating energy non-stop. They are therefore often used in combination with traditional ones. In this case, power plant capacity changes will depend not only on the time of day, but also on the season and weather conditions. It will become more difficult to regulate their operation.

Students of St Petersburg University – participants in the start-up contest – have decided to address the issue of efficient energy use. They paid attention to energy storage systems – batteries that are installed in a specific area or residential complex. They are capable of:

accumulating the surplus of electricity generated during its low consumption; and distributing the accumulated energy during its intensive use. As a result, it makes it possible to smooth out the peaks of electricity consumption and prevent its irrational consumption. At present, these storage systems use lithium-ion batteries. However, they have a small capacity, which gradually decreases due to: the formation of dendritic chains (‘spikes’ emerging from the lithium surface); and the washing out of the cathode. All this increases the cost of energy storage, which, in turn, affects the price for electricity.

‘We are developing magnesium-sulphur batteries. They will have two to two and a half times more capacity than lithium-ion batteries and will not be subject to the risk of dendrites,’ said Vadim Kozlov, the team captain, master's student in physics. ‘As a result, the cost of electricity storage can be reduced by 50%. Additionally, magnesium and sulphur, unlike lithium, are mined in Russia, which should also reduce the cost of producing energy storage systems. All this can have a positive effect on the final price of electricity for the consumer.’

Do not let sulphur ‘wash away’

Attempts to invent magnesium-sulphur batteries have been made for a long time. The difficulty to create them lies in the fact that the electrolyte, which is used in lithium-ion storage, in magnesium-sulphur storage contributes to the washing out of sulphur from the cathode. This reduces the storage capacity. Part of this challenge has been solved by Toyota. In 2010, they produced the first magnesium-sulphur batteries, having developed a new electrolyte for them. However, the inventors failed to eliminate completely the sulphur leak from the cathode. As a result, the capacity of such a storage did not exceed the performance of lithium-ion batteries.

The students have put forward another way to avoid the washing out of sulphur – with the help of double protection of the cathode. First, the sulphur molecules are placed in a special titanium oxide sphere that does not let them out. In this case, magnesium, whose ions are inferior in size to sulphur ions, can penetrate the shell and react with sulphur. Secondly, a special film is applied to the cathode using the molecular layering method. This film prevents sulphur from entering the electrolyte. Through this combined approach, the sulphur will be isolated from the electrolyte, resulting in high storage capacities. The preliminary calculations of the inventors show that if by 2025 batteries for energy storage systems have been produced according to their technology, five years after its introduction, the cost of electricity may fall by 30%.

‘We believe that our development might be of interest to enterprises that make batteries for smart houses and those that make batteries for energy storage systems,’ said Vadim Kozlov. ‘The introduction of our technology will require a significant restructuring of the process of manufacturing the cathode and anode. However, according to our calculations, these investments will pay off quickly.’

The team is currently working on creating electrodes and measuring how many charge and discharge cycles they can perform. In the final, the participants will show cathode and anode tests with the desired effect.

The team consists of five people. Artur Taishev (‘Chemistry’) is working on the trapping of sulphur in the cathode. Alina Seitova (‘Applied Mathematics and Informatics’) is responsible for collecting the data on electricity consumption required to calculate the battery capacity. Iana

Buchkovski (‘Management’) is in charge of the business model for the project. Nikita Kuznetsov (‘Physics’) deals with the molecular layering of the film on the cathode. Vadim Kozlov (‘Physics’) is also responsible for this task and for coordinating the work in the team.

The ‘SPbU Start-up’ contest is being held at the University for the sixth time. Teams that have presented best knowledge-intensive and commercially viable business models will receive monetary prizes from the St Petersburg University Endowment Fund: 300,000 roubles for the first place; 200,000 for the second; and 100,000 for the third. Additionally, the two winning teams may be offered to establish a small innovative enterprise with the participation of St Petersburg University. Grants for their projects’ development will amount to 1,000,000 and 700,000 roubles for the first and second places respectively. For more detailed information about the ‘SPbU Start-up-2021’ student contest please visit the website of the Endowment Fund of St Petersburg University.