CENTRO DE INVESTIGACION Y DESARROLLO EN MATERIALES AVANZADOS Y ALMACENAMIENTO DE ENERGIA DE JUJUY
congresos y reuniones científicas
Separators modified to improve the cyclability of lithium sulfur batteries
EZEQUIEL LEIVA; DANIEL BARRACO; VISINTIN A.; KARIM SAPAG; CECILIA CALDERON; GERMAN LENER,
Congreso; 20th Topical Meeting of the International Society of Electrochemistry Advances in Lithium and Hydrogen Electrochemical Systems for Energy Conversion and Storage; 2017
20th Topical Meeting of the International Society of Electrochemistry Advances in Lithium and Hydrogen Electrochemical Systems for Energy Conversion and Storage
Within 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, for ej the low capacity. 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 Nevertheless 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 volume of 80% between lithiated and delithiated phase, polysulfides formed as intermediated are very soluble in the electrolyte wich cause a loss of active material; shuttle ( asi se dice?)efect, when the efficiency of the lithium anode can be lowered due the passivation with insoluble sulfides; metalic lithium as anode; degradation of electrolyte 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 suppressing 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 oxidized 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 effect 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 voltammetric, Galvanostatic charging/discharging test, etc.