Lithium battery has become an indispensable part of our daily life. It not only dominates the small battery market of portable electronic devices, but also is widely used in electric vehicles. However, it also has many serious problems, including potential fire hazards and performance degradation at low temperature, as well as the considerable impact of waste battery disposal on the environment. However, the latest results from a Russian research team make a new type of battery possible.
According to Oleg Levin, head of the research team and professor of electrochemistry at St. Petersburg University in Russia, chemists have been exploring nitro-containing polymers with redox activity as electrochemical energy storage materials because of their high energy density. Due to the rapid redox kinetics, the polymer batteries charge and Discharge very fast.
But at the same time, Levin also pointed out that when it is implemented in the product, it will face the problem of insufficient conductivity, which hinders the collection of charge, and it is difficult to solve the problem even with highly conductive additives such as carbon.
To solve this problem, researchers from the University of St. Petersburg synthesized a polymer based on nickel-selenium complexes. The molecule of this metal polymer is like a molecular thread, connecting the energy-intensive nitryl pituitary to it. The molecular structure of the material enables it to achieve high capacitance in a wide temperature range.
Levin further explained, "We put forward the concept of this material as early as 2016. In the study of the charge transfer mechanism of these compounds, we found that there are two key development directions. First of all, these compounds can be used as a protective layer to cover the battery's main conductor cable. Secondly, they can be used as active components of electrochemical energy storage materials. "
It took scientists more than three years to develop the polymer. In the first year, they tested the concept of the new material: combining the various components to simulate a conductive trunk and a redox-active pituitary containing nitroxyl groups. It is important to ensure that all parts of the structure work together and reinforce each other. The next stage is the chemical synthesis of compounds. This is also the most challenging part of the project. This is because some ingredients are so sensitive that even the slightest mistake made by scientists can lead to the degradation of the sample.
Of the several polymer samples obtained, only one was found to be stable and efficient enough. The main chain of the new compound is formed by the complex of nickel and Salen ligand. A stable free radical capable of rapid oxidation and reduction (charge and discharge) is connected to the main chain through a covalent bond.
"batteries made from our polymers can be recharged in seconds, 10 times faster than conventional lithium-ion batteries," Levin said. This has been confirmed by a series of experiments. At this stage, however, it still lags behind in terms of capacity, 30-40% lower than lithium-ion batteries. We are currently working to improve this indicator while maintaining the charge and discharge rate. "
The cathode of this new type of battery has been fabricated and used as the cathode of the chemical current source. What is needed now is the negative electrode, that is, the anode. In fact, it does not need to be made from scratch and can be selected from existing electrodes. Together, the researchers point out, they will form a system that, in some areas, may soon replace lithium-ion batteries.
"the new battery can work at low temperatures, and it will be a good choice in places where there is a high demand for fast charging. It is safe to use and does not have any substance that may pose a burning hazard, unlike the cobalt-based batteries commonly used today. It also contains a significant reduction in the number of metals that may cause harm to the environment. " Levin added, "our polymers contain a small amount of nickel, but much less than in lithium-ion batteries."
