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Pawel Jezowski1 Elise Deunf2 Olivier Crosnier2 Philippe Poizot2 Thierry Brousse2 Francois Beguin1

1, Poznan University of Technology, Poznan, , Poland
2, Nantes University, Nantes, , France

Internal hybridization of a battery-type electrode with an electrical double-layer (EDL) electrode appears as a key for opening a path to more versatile devices which can at the same time deliver high power and high energy, while being able to display a long term cycle life. The best example is the lithium-ion capacitor (LIC) which implements an EDL positive electrode made from porous carbon and a LIB faradaic negative electrode made from graphite or hard carbon, while using a lithium salt (LiPF6) generally dissolved in ethylene carbonate:dimethyl carbonate (EC:DMC) mixture [2]. Since lithium must be intercalated in the graphite/carbon negative electrode, the first concept of LIC included an auxiliary metallic lithium electrode which was used for pre-lithiation, hence complicating the cell design and being potentially the cause of safety issues as thermal runaway. Therefore, pre-lithiation has been proposed directly from the electrolyte [3], but it leads to a decrease of ionic concentration and conductivity, which might have a negative impact on the LIC power.

A novel strategy to lithiate the negative electrode consists in an irreversible lithium de-intercalation from a sacrificial lithiated material incorporated together with activated carbon in the positive electrode [4]. Using lithiated oxides with low band gaps, such as Li5ReO6, enables extracting lithium ions at a potential around 4.2 V vs. ref. Li/Li+ and to avoid detrimental electrochemical oxidation of the electrolyte [5]. Very promising performance was obtained with renewable organic lithium salts from which lithium is irreversibly extracted, with a capacity of ca. 350 mAh/g, at potential as low as. 3.3 V vs. Li/Li+; the resulting LIC cells demonstrate an excellent cycle life in the potential range from 2.2 ~ 4.0 V [6].

This presentation will briefly introduce the various strategies which have been successfully used by our group with a special focus on the structural/microstructural changes occurring after the first pre-lithiation step and on the performance of LICs in terms of energy and power densities as well as cycle life. New perspectives, using materials leaving a reduced dead-mass after pre-lithiation, will be also detailed.


References
[1] F. Béguin, E. Frackowiak, Supercapacitors: Materials, Systems and Applications, Wiley-VCH, Weinheim, 2013.
[2] T. Aida, K. Yamada, M. Morita, Electrochem. Solid-State Lett., 9 (2006) A534.
[3] V. Khomenko, E. Raymundo-Piñero, F. Béguin, J. Power Sources, 177 (2008) 643.
[4] M.-S. Park, Y.-G. Lim, J.-H. Kim, Y.-J. Kim, J. Cho, J.-S. Kim, Adv. Energy Mater., 1 (2011) 1002.
[5] P. Jezowski, K. Fic, O. Crosnier, T. Brousse, F. Béguin, J. Mat. Chem. A, 4 (2016) 12609.
[6] P. Jezowski, O. Crosnier, E. Deunf, P. Poizot, F. Béguin, T. Brousse, Nat. Mat. (in press).

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