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Carbonaceous Separators modified to improve the cyclability of lithium sulfur batteriesCalderón Cecilia1, Lener Germán1, Sapag Karim2, Visintin Arnaldo3, Leiva Ezequiel4, Barraco Daniel1AffiliationAddresse-mail addressWithin electrochemical batteries, lithium-containing batteries are being used in various electronic devices such as electric cars, hybrid motors, laptops, cell phones, etc. Due to the diversity of materials that can be used as electrodes1-4 the spectrum of applications of these devices is in constant increase. However, current commercial batteries still present operational problems that limit their application. That is why new materials constantly come up that try to overcome such problems.5,6 Lithium?sulfur batteries are especially promising electrochemical systems because of their high theoretical capacity of 1672 mAh/g and energy density of 2600 Wh/kg. The higher energy density is due to the phase transitions undergone by the sulfur which allows capturing more lithium ions than the transition metal based materials currently used. In a charge/discharge cycle can be seen two plateaus: one at 2,3 V vs. Li/Li+ that corresponds at reduction from S8 solid to Li2S4 and the other at 1,9 V vs. Li/Li+ that corresponds at reduction from Li2S4 to Li2S with corresponding formation of intermediate products. Also, the active material is sulfur, which is economical, abundant, and non toxic.7-10 Neverthless this material has several problems that need solution. Some of these problems are: Li2S and S8 are insulating, so it is necessary to cover with some conductive material; the material has a change of volumen of 80% between lithiated and delithiated phase, polysulfides formed as intermediated are very soluble in the electrolite wich cause a loss of active material; shuttle efect, when the efficiency of the lithium anode can be lowered due the passivation with insoluble sulfides; metalic lithium as anode; degradation of electrolite by the polysulfides.One of the strategies used to improve ciclability of the material, avoiding shuttle effect is the modification of separator with some materials like TiO211, or carboneaus materials12, etc., that trap the polysulfides avoiding diffusion and suppresing the shuttle effect. In this work we study the ciclability of S/C composites as cathodic material. We used modified separators with different quantities of CMK3 oxidied prepared in the laboratory. Two kinds of separators were used: Celgard and ceramic impregnated separators. It can be seen than when modified separators are used improves the retention of the initial capacity with the number of cycles, respect to separator without modification. Also we studied the efect of the quantity of CMK3 in the separator in the ciclability of the system. All samples were characterized physical and electrochemically using techniques as Scanning Electron Microscopy, Energy-dispersive X-ray spectroscopy, Cyclic voltamperometry, Galvanostatic charging/discharging test, etc. [1] B.L. Ellis, K. Town, L.F. Nazar, Electrochim. Acta 84 (2012) 145.[2] S.B. Chikkannanavar, D.M. Bernardi, L. Liu, J. Power Sources, 248 (2014) 91.[3] B.L. Ellis, K.T. Lee, L.F. Nazar, Chem. Mater. 22 (2010) 691. [4] P. Roy, S.K. Srivastava, J. Mater. Chem.A 3 (2015) 2454.[5] B. Scrosati, J. Solid State Electrochem. 15 (2011) 1623.[6] P. Roy, S.K. Srivastava, J. Mater. Chem.A 3 (2015) 2454.[7] J.B. Goodenough, Acc. Chem. Res. 46 (2013) 1053.[8] B. Scrosati, J. Hassoun, Y.K. Sun, Energy Environ. Sci. 4 (2011) 3287.[9] K. Sun, S.T. Myung, B.C. Park, J. Prakash, I. Belharouak, K. Amine, Nat. Mater. 8 (2009) 320.[10] M.S. Whittingham, Chem. Rev. 104 (2004) 4271.[11] Z. Xiao , Z. Yang , L. Wang , H. Nie , M. Zhong , Q. Lai , X.Xu , L. Zhang , S. Huang, Adv. Mater. 27 (2015) 2891.[12] Y-S. Su, A. Manthiram, Nat. Comm., 3 (2012) 1166.

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