Ionic liquids and their solid-state analogues as materials for energy generation and storage

Abstract

Salts that are liquid at room temperature, now commonly called ionic liquids, have been known for more than 100 years; however, their unique properties have only come to light in the past two decades. In this Review, we examine recent work in which the properties of ionic liquids have enabled important advances to be made in sustainable energy generation and storage. We discuss the use of ionic liquids as media for synthesis of electromaterials, for example, in the preparation of doped carbons, conducting polymers and intercalation electrode materials. Focusing on their intrinsic ionic conductivity, we examine recent reports of ionic liquids used as electrolytes in emerging high-energy-density and low-cost batteries, including Li-ion, Li–O2, Li–S, Na-ion and Al-ion batteries. Similar developments in electrolyte applications in dye-sensitized solar cells, thermo-electrochemical cells, double-layer capacitors and CO2 reduction are also discussed.

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Figure 1: Ionothermal synthesis of hybrid IL–Co(OH)2 capacitor materials.
Figure 2: High rate cycling of lithium.
Figure 3: OIPC-based dye-sensitized solar cells.
Figure 4: Reaction pathways for the electrochemical reduction of CO2 at a lead electrode in acetonitrile.
Figure 5: Photo-driven water oxidation in butylammonium protic ILs.
Figure 6: Wastewater-driven microbial fuel cell.

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Acknowledgements

D.R.M. and M.F. thank the Australian Research Council for support from the Australian Laureate Fellowship programme and J.M.P. and P.C.H. for support from the Discovery Projects program and the Australian Centre for Electromaterials Science. This work was supported in part by the National Natural of Science Foundation of China (Grant Nos 21371101, 21421001), 111 Project (B12015) and MOE Innovation Team (IRT 13022) of China. H.O. acknowledges the financial support of the Grant-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (KAKENHI, No. 26248049).

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Correspondence to Douglas R. MacFarlane.

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