Pseudocapacitive energy storage in supercapacitor electrodes differs significantly from the electrical double-layer mechanism of porous carbon materials, which requires a change from conventional thinking when choosing appropriate electrolytes. Here we show how simply changing the solvent of an electrolyte system can drastically influence the pseudocapacitive charge storage of the two-dimensional titanium carbide, Ti3C2 (a representative member of the MXene family). Measurements of the charge stored by Ti3C2 in lithium-containing electrolytes with nitrile-, carbonate- and sulfoxide-based solvents show that the use of a carbonate solvent doubles the charge stored by Ti3C2 when compared with the other solvent systems. We find that the chemical nature of the electrolyte solvent has a profound effect on the arrangement of molecules/ions in Ti3C2, which correlates directly to the total charge being stored. Having nearly completely desolvated lithium ions in Ti3C2 for the carbonate-based electrolyte leads to high volumetric capacitance at high charge–discharge rates, demonstrating the importance of considering all aspects of an electrochemical system during development.
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The data that support the plots within this paper and other findings of this study are available from the corresponding author upon reasonable request.
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The research was sponsored by the Fluid Interface Reactions, Structures, and Transport (FIRST) Center, an Energy Frontier Research Center (EFRC) funded by the US Department of Energy, Office of Science, and Office of Basic Energy Sciences. Access to the HFBS was provided by the Center for High Resolution Neutron Scattering, a partnership between the NIST and the NSF under agreement no. DMR-1508249. Certain commercial equipment, instruments or materials are identified in this paper in order to specify the experimental procedure adequately. Such identification is not intended to imply recommendation or endorsement by the National Institute of Standards and Technology, nor is it intended to imply that the materials or equipment identified are necessarily the best available for the purpose. J. Li and H. Wang from Drexel University are acknowledged for helping with material characterization. Y. Honda and Y. Soda from Murata Manufacturing Co. are acknowledged for helpful discussions and help with the characterization.
The authors declare no competing interests.
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Wang, X., Mathis, T.S., Li, K. et al. Influences from solvents on charge storage in titanium carbide MXenes. Nat Energy 4, 241–248 (2019). https://doi.org/10.1038/s41560-019-0339-9
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