Researchers from Japan have made a breakthrough in developing high-performance solid electrolytes for rechargeable batteries using material informatics. This innovative approach has the potential to increase the safety, energy density, and lifespan of next-generation batteries, paving the way for wider adoption of electric vehicles and renewable energy storage solutions. The study, published in the journal ACS Applied Electronic Materials, showcases the power of combining empirical knowledge and machine learning to explore new organic ionic plastic crystal (OIPC) materials with excellent ionic conductivity.
Unlocking the Potential of Organic Ionic Plastic Crystals
The surge in the adoption of renewable energy and the rapid growth of the electric vehicle market have significantly increased the demand for high-performance, all-solid-state batteries. Compared to conventional liquid electrolyte-based batteries, solid-state batteries offer several advantages, including higher energy density, improved safety, longer lifespan, and reliable operation over a wide temperature range.
However, there are still challenges to their widespread applications, such as low ionic conductivity, high interfacial resistance, and the presence of particle-particle interfaces in the electrolyte, which can lead to increased resistance and lower energy density. To address these issues, researchers have been exploring various solid electrolyte materials, including inorganic and organic solid electrolytes.
Harnessing the Power of Material Informatics
In the recent study, the research team from Sophia University and the Tokyo Institute of Technology turned their focus toward organic ionic plastic crystals (OIPCs) as a promising solution. OIPCs consist of an organic cation and a suitable inorganic anion, together with the lithium salt of the same anion. Being entirely composed of ions, these materials offer high ionic conductivity, high stability, and negligible flammability, making them highly suitable as solid electrolytes for batteries.
To explore highly conductive OIPCs, the researchers utilized material informatics (MI), which leverages informational science, such as statistical science and machine learning, for efficient material development. By combining empirical rules and a machine learning-based MI model, the team successfully synthesized eight new compounds, including six OIPCs and two ionic liquids. One of the synthesized OIPCs exhibited an excellent ionic conductivity of 1.75 × 10^-4 S cm^-1 at 25°C, which is among the highest reported values to date.
Insights into the Relationship between Ionic Radius and Conductivity
The MI results also revealed new insights into the relationship between ionic radius and ionic conductivity of OIPCs. Conventional empirical rules suggest that a lower ionic radius to ionic conductivity ratio is desirable. However, the newly synthesized compounds indicate that an optimal value exists. Additionally, the MI model predicted discontinuous changes in the OIPC structure, suggesting that further improvements in prediction accuracy can also enable the prediction of phase transitions.
Explaining the potential benefits of the new OIPCs, Professor Masahiro Yoshizawa-Fujita from Sophia University stated, “The development of high-performance solid electrolytes will increase the safety of rechargeable batteries, as there will no longer be a concern about liquid leakage. Also, it will increase the energy density of these batteries, making devices equipped with batteries lighter and more compact. For example, OIPC-based rechargeable batteries can increase the range of electric vehicles and promote their widespread adoption.”
