Aiming at increased performances for battery systems, lithium/sulfur technology (Li/S) is widely regarded as one of the most promising alternatives to lithium-ion systems. Although the cyclability of the best Li/S current prototypes needs to be further improved, the potentially superior expected energy density (400-600 Wh.Kg^-1) explains the high attention that this technology has received over the last 10 years. ¹

Different studies ^2,3 have pointed out that both high sulfur loading and utilization are required to achieve the high energy and capacity targeted for Li/S cells. While this is a real challenge to achieve with classic aluminum-supported 2-D electrodes, several 3-D carbon-sulfur architectures have started to be explored. ^2,4 Since the Li/S reactions involve solid-liquid transitions at the positive side of the battery, the pore volume and the active surface of the electrode available for the products deposition have been shown to be crucial parameters in order to optimize the battery performances. ⁵

To enable the transfer of these progresses from a laboratory to an industrial scale, the optimization of the cathode structures should be achieved with simple and cost-effective formulations, and with means of production possible to scale up. In this regard, printing methods have been increasingly investigated for the production of Li-ion flexible batteries, with performances of the resulting products which are comparable to the classic production methods. ^6,7

In our work we therefore applied the printing techniques to the production of 3-D carbon-based current collectors for Li/S positive electrodes: different formulations based on carbon fibers and high active surface materials (VGCF®, Ketjenblack®, etc.) have been produced and tested in coin and pouch cells with metallic lithium as negative electrode.

SEM and BET analyses have been systematically performed on the samples, and showed that the high flexibility of the formulations permits to tailor the bulk and surface pore distribution, and the active surface. The first electrochemical tests were performed in a “catholyte” configuration and have shown, for all the 3-D structures produced, promising results with respect to state-of-the-art references, with the reversible capacity being clearly oriented by the ratio carbon fibers/ high active surface materials.

The use of carbon fibers and polymer binders provides the structures with a sufficient mechanical strength to be self-standing and to be used for an in-line printing process. These promising results on 3-D architectures pave the way for the first time to printable, Li/S positive electrodes.

[1] O. Gröger, H.A. Gasteiger, J.-P. Suchsland, Journal of The Electrochemical Society, 162 (14), A2605-A2622 (2015)

[2] M. Hagen, D. Hanselmann, K. Ahlbrecht, R. Maça, D. Gerber, J. Tübke, Advanced Energy Materials, 5 (15), 1401986 (2015)

[3] M.A. Pope, I.A. Aksay, Advanced Energy Materials, 5 (16), 1500124 (2015)

[4] S. Waluś, C. Barchasz, R. Bouchet, J.-F. Martin, J.-C. Leprêtre, F. Alloin, Electrochim. Acta, 180 (2015) 178-186

[5] Y.Ma, H. Zhang, B. Wu, M. Wang, X. Li, H. Zhang, Scientific Reports, 5, Article Number : 14949 (2015)

[6] R.E. Sousa, C.M. Costa, S. Lanceros-Méndez, ChemSusChem, 8, 3539-3555 (2015)

[7] K. Sun, T.-S. Wei, B.J. Ahn, J.Y. Seo, S.J. Dillon, J.A. Lewis, Advanced Materials, 25, 4539-4543 (2013)