Lithium Sulfide/Carbon (Li2S/C) Electrode Preparation in Hydrogen Sulfide (H2S) Flow and Its Electrochemical Performance

Energy storage for automotive and portable devices is one of the main research topics today and in the future. Today’s batteries based on Li-ion technology are not up to par with the demands of long-range vehicles[1]. The solutions to this problem are beyond Li-ion technologies, e.g. Li/S or Li/air. Possible distances of >400 km or >550 km for Li/S or Li/air, respectively, compared to today’s 160 km with Li-ion technology are desirable[2]. The biggest obstacle in Li/S and Li/air batteries are safety concerns due to the use of elemental lithium as anode material[3]. This may be overcome by using a Li₂S cathode, equivalent to the discharged state of the Li/S battery, and a lithium free anode such as carbon.

Since Li₂S is very moisture sensitive, preparation of Li₂S electrodes needs to be in a very controlled environment. We invented a new method to produce Li₂S/C electrodes in a H₂S flow, by using various lithium salts as starting materials. This way the air-sensitive Li₂S is introduced in the electrode in the very last step. This lowers the process costs and allows an easier handling of the electrodes during preparation, since it is less moisture sensitive. Furthermore it might allow the use of aqueous binder systems which is novel for Li₂S electrodes.

Electrodes containing a lithium salt, carbon and a binder were cast and after drying exposed to H₂S. The resulting electrode consists of lithium sulfide, carbon and the binder. The reaction is confirmed by X-ray diffraction and elemental analysis. The morphology and homogeneity of the electrode is investigated by scanning electron microscopy. Galvanostatic cycling of the Li₂S/C electrode validates the new method.

[1] X. Ji, L.F. Nazar, Advances in Li–S batteries, Journal of Materials Chemistry, 20 (2010) 9821.

[2] P.G. Bruce, S.A. Freunberger, L.J. Hardwick, J.M. Tarascon, Li-O₂ and Li-S batteries with high energy storage, Nature materials, 11 (2012) 19-29.

[3] J.M. Tarascon, M. Armand, Issues and challenges facing rechargeable lithium batteries, Nature, 414 (2001) 359-367.