Design of High-Entropy Electrolytes Enabled By the High-Throughput and Autonomous Procedure
Authors: Martinez Victor , Fisker-Bødker Nis , Vincent Smobin , Chang Jin Hyun 
Published: February 2024

Electrolytes in Li-ion batteries play a significant role as they influence different aspects directly related to the battery performance, such as safety, voltage window, electrochemical stability, and the formation of solid-electrolyte interphase (SEI). Conventionally, these electrolytes are composed of a lithium salt dissolved in an organic solvent such as ethylene carbonate and propylene carbonate. Regarding safety, these organic electrolytes can be replaced by room-temperature ionic liquids (RTILs), which present lower vapor pressure and non-flammability.1 Moreover, adding polymer to these liquid electrolytes to form polymer gel electrolytes has proven to be a good strategy to avoid dendritic growth and increase electrolyte stability.2

The properties of RTIL electrolytes containing Li salts have been studied in the last decade. Still, the scope has been limited primarily to simple RTILs consisting of one cationic and one anionic species. Inspired by the success of high-entropy alloys (HEAs) for forming stable solid solutions with excellent mechanical properties,3 the concept of high-entropy materials has been recently transferred to electrolytes, where the effect of mixing multiple Li salts is explored.4 However, the number of compositional combinations increases rapidly when multiple salts, cationic and anionic species are introduced, and the explorable compositional space increases even more when polymers are added to the mixture.
Automating the electrolyte preparation and characterization can be the key feature to allow the exploration of all the possible electrolyte combinations. In this work, we explain the first preliminary results obtained from an autonomous preparation and characterization of high-entropy electrolytes composed of a mixture of two different lithium salts in ionic liquids consisting of multiple anionic and cationic species. In addition, the adaptation of the autonomous system of preparation and characterization of liquid electrolytes to polymer gel electrolytes is also proposed and explained.

References.

(1) Niu, H.; Wang, L.; Guan, P.; Zhang, N.; Yan, C.; Ding, M.; Guo, X.; Huang, T.; Hu, X. Recent Advances in Application of Ionic Liquids in Electrolyte of Lithium Ion Batteries. J. Energy Storage
2021, 40, 102659. https://doi.org/10.1016/j.est.2021.102659.
(2) Chen, J.; Wu, J.; Wang, X.; Zhou, A.; Yang, Z. Research Progress and Application Prospect of Solid-State Electrolytes in Commercial Lithium-Ion Power Batteries. Energy Storage Mater.
2021, 35, 70–87. https://doi.org/10.1016/j.ensm.2020.11.017.
(3) Yeh, J.-W.; Chen, S.-K.; Lin, S.-J.; Gan, J.-Y.; Chin, T.-S.; Shun, T.-T.; Tsau, C.-H.; Chang, S.-Y. Nanostructured High-Entropy Alloys with Multiple Principal Elements: Novel Alloy Design Concepts and Outcomes. Adv. Eng. Mater.
2004, 6 (5), 299–303. https://doi.org/10.1002/adem.200300567.
(4) Wang, Q.; Zhao, C.; Wang, J.; Yao, Z.; Wang, S.; Kumar, S. G. H.; Ganapathy, S.; Eustace, S.; Bai, X.; Li, B.; Wagemaker, M. High Entropy Liquid Electrolytes for Lithium Batteries. Nat. Commun.
2023, 14 (1), 440. https://doi.org/10.1038/s41467-023-36075-1.