Deep Eutectic Solvents in Electrochemical Energy Storage

Deep eutectic solvents (DESs) constitute a rapidly expanding class of designer electrolytes formed by the combination of a hydrogen‐bond donor and a quaternary ammonium salt or other electron acceptor. The complex hydrogen‐bond network leads to a pronounced depression in melting point compared with the parent components, yielding a non‐volatile, non‐flammable medium with tunable viscosity, conductivity and electrochemical stability. These attributes have prompted intensive investigation of DESs as green electrolytes across diverse energy storage platforms, including supercapacitors, lithium‐ion and post‐lithium batteries, redox flow systems and emerging semi‐solid devices. Recent work has focused on correlating microscale structure and dynamics with macroscopic transport and stability, while application‐driven studies have demonstrated enhanced cycle life, wide voltage windows and high energy densities. The inherent modularity of DES formulations permits tailor‐made electrolytes for specific electrode chemistries, addressing safety, cost and sustainability challenges in next‐generation energy storage.

Research from Nature Portfolio

A multidisciplinary investigation into model DESs comprising choline chloride with glycerol or ethylene glycol has revealed how microscopic heterogeneities emerge during eutectic formation and govern dynamic modes from picoseconds to seconds. The study combines advanced spectroscopy, scattering techniques and molecular simulations to map local structuring, showing that the addition of salt induces transient domains that modulate structural relaxation and ionic transport. Insights into the coupling between rotational and translational motions have established design principles for optimising viscosity and conductivity. This deeper understanding of structure–dynamics relationships provides a predictive framework for tailoring DES electrolytes to achieve target performance metrics in electrochemical energy storage applications.

Deep Eutectic Solvents in Electrochemical Energy Storage publication trend

The graph below shows the total number of articles in deep eutectic solvents in electrochemical energy storage across all publications each year (not limited to Nature Index journals).

Technical terms

Deep eutectic solvent (DES): A eutectic mixture of hydrogen bond donor and acceptor species that exhibits a melting point lower than either component.

Hydrogen bond network: A three‐dimensional arrangement of hydrogen bonds that influences liquid structure, viscosity and transport properties in DESs.

Electrochemical window: The potential range over which an electrolyte remains stable without decomposition.

Ionic conductivity: A measure of an electrolyte’s ability to transport charge through ion movement.

Specific capacitance: The capacitance per unit mass of electrode material, indicating energy storage capability in supercapacitors.

Transference number: The fraction of total ionic current carried by a specified ion species in an electrolyte.

References

1. Evolution of microscopic heterogeneity and dynamics in choline chloride-based deep eutectic solvents. Nature Communications (2022).
2. Translational and reorientational dynamics in deep eutectic solvents. The Journal of Chemical Physics (2021).
3. Reline deep eutectic solvent as a green electrolyte for electrochemical energy storage applications. Energy & Environmental Science (2022).
4. Lithium Salt Effects on the Liquid Structure of Choline Chloride–Urea Deep Eutectic Solvent. ACS Sustainable Chemistry & Engineering (2022).
5. Rationally Designed Ternary Deep Eutectic Solvent Enabling Higher Performance for Non-Aqueous Redox Flow Batteries. Processes (2022).