Ionic Liquid Electrolytes for Energy Storage Applications

Ionic liquid electrolytes have emerged as a versatile class of media for next-generation energy storage, offering intrinsic non-volatility, high thermal and electrochemical stability, and wide electrochemical windows. Composed entirely of organic cations and inorganic or organic anions, these room-temperature molten salts can be tuned to optimise ionic conductivity, viscosity and safety. Their negligible vapour pressure and resistance to flammability address long-standing concerns over thermal runaway in lithium, sodium and other metal-ion batteries. Furthermore, the design flexibility of ionic liquids enables the formation of robust interfacial layers on metal electrodes, suppressing dendrite growth and enhancing cycle life. In addition to conventional liquid formulations, hybrid systems that incorporate polymers, solid supports or carbonate cosolvents combine the desirable attributes of ionic liquids with mechanical or transport advantages. Globally, the adoption of ionic liquid electrolytes promises to enhance the performance, lifespan and safety of large-scale grid storage, electric vehicles and portable electronics, while reducing dependency on volatile organic solvents. Continued research focuses on understanding ion transport mechanisms, interfacial chemistry and the development of ultra-concentrated or protic variants for diverse metal-ion platforms.

Research from Nature Portfolio

Recent studies have demonstrated that pre-conditioning lithium metal electrodes with specific ionic liquids yields a durable solid–electrolyte interphase that enables over 1,000 charge–discharge cycles with Coulombic efficiencies exceeding 99.5%, thus preventing dendrite formation and electrolyte depletion. Another investigation introduced a bespoke dicationic imidazolium-based ionic liquid as an additive in conventional organic carbonate electrolytes, significantly improving high-temperature stability, cycle life and discharge capacity by forming a stabilising interfacial film on graphite and nickel-rich cathodes. Additionally, hybrid electrolytes combining a phosphonium bis(salicylato)borate ionic liquid with glycol ether solvents have been shown to afford strong lithium–anion coordination, tune ion association and enhance transport numbers, offering a pathway to safer, halogen-free formulations with favourable viscosity and conductivity profiles.

Ionic Liquid Electrolytes for Energy Storage Applications publication trend

The graph below shows the total number of articles in ionic liquid electrolytes for energy storage applications across all publications each year (not limited to Nature Index journals).

Technical terms

Ionic liquid: A salt that is liquid at ambient temperature, consisting solely of ions and exhibiting negligible vapour pressure, high stability and tunable conductivity.

Solid–electrolyte interphase (SEI): A passivation layer formed at the electrode–electrolyte interface that regulates ion transport and prevents continuous electrolyte decomposition.

Dendrite: Filamentary deposits of metal (often lithium) that grow on the electrode surface during cycling and can lead to short circuits and capacity loss.

Transference number: The proportion of charge carried by a specific ion species in an electrolyte, influencing overall conductivity and electrode kinetics.

References

1. Stabilizing lithium metal using ionic liquids for long-lived batteries. Nature Communications (2016).
2. Synthesis, characterization and application of a non-flammable dicationic ionic liquid in lithium-ion battery as electrolyte additive. Scientific Reports (2020).
3. Transport and Association of Ions in Lithium Battery Electrolytes Based on Glycol Ether Mixed with Halogen-Free Orthoborate Ionic Liquid. Scientific Reports (2017).
4. Ionic liquid electrolytes for sodium-ion batteries to control thermal runaway. Journal of Energy Chemistry (2023).
5. Recent Advance in Ionic‐Liquid‐Based Electrolytes for Rechargeable Metal‐Ion Batteries. Advanced Science (2021).
6. Understanding transport mechanisms in ionic liquid/carbonate solvent electrolyte blends. Physical Chemistry Chemical Physics (2018).