A research team under the guidance of Professor Pavel Troshin from Skoltech analyzed coordination polymers, a family of compounds with rarely explored applications in metal-ion batteries, and indicated their possible future applications in energy storage devices with a high charging and discharging rate and stability.
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The study outcomes have been published in Chemistry of Materials.
One of the main characteristics of lithium-ion batteries is the charging–discharging rate. Many advanced commercial batteries require at least an hour to get completely charged, which surely restricts their wider application, specifically for electric vehicles. The problem with the active materials, like the well-known anode material graphite, is that their capacity decreases considerably with the increase in their charging rate.
To retain the capacity of the battery at high charging rates, these active electrode materials should have high ionic and electronic conductivity, which can be found in the case of new coordination polymers that are obtained from aromatic amines and transition metal salts, like copper or nickel. Although such compounds are a promising candidate, their use in lithium-ion batteries remains almost undiscovered.
A new study by researchers from Skoltech and the Institute for Problems of Chemical Physics of RAS headed by Professor P. Troshin together with the University of Cologne (Germany) and the Ural Federal University was centered on tetraaminobenzene-based linear polymers of copper and nickel.
Despite the fact that these linear polymers displayed much less initial electronic conductivity than their 2D equivalents, it was found that they can be used as anode materials that become charged or discharged within a minute, as their conductivity increases markedly after the first discharge owing to lithium doping.
These anode materials were also found to have remarkable stability at high charging and discharging rates: they have been shown to retain about 79% of their maximum capacity following about 20,000 charging and discharging cycles.
Moreover, copper-based polymers were found to be useful as anode and high-capacity cathode materials. The scientists indicate that there are ample opportunities for structure optimization though the cathode never works in a stable condition.
There are a lot of methods for fine-tuning the characteristics of coordination polymers. Actually we deal here with a sort of a construction kit where the parts can be easily changed or replaced.
Roman Kapaev, Study First Author and PhD Student, Skoltech
Kapaev continued, “We can modify both the amine structure and the transition metal cation, and by doing so, raise the capacity, increase or decrease the redox potential, improve stability and various other performances. This trail-blazing study touches upon an extensive research area, which, I am sure, has yet a lot to reveal.”