Sol-gel synthesis of hybrid organic-inorganic electrolytes for application in Lithium-ion microbatteries

JADRA MOSA; RAÚL A. PROCACCINI; JOHN FREDY VÉLEZ; MARIO APARICIO AMBRÓS

Vitoria - Gasteiz

Congreso; Power our future 2012: The first International Forum on Progress Trends in Batteries and Capacitor Technologies; 2012

CIC energigune

Great attention is presently devoted to lithium batteries, as they may greatly contribute to achieve important goals such as energy renewal and environmental control. In fact, lithium batteries are expected to play a key role storage of intermittent energy sources, e.g., solar or wind, as well as in the powering of controlled emission, electric or hybrid vehicles. However to achieve these important goals, lithium batteries still require improvements especially in terms of reliability, safety and cost. In this respect, a promising approach is based on the change from a conventional liquid electrolyte configuration. Traditionally, a liquid electrolyte including a lithium salt (most commonly LiPF6) and organic solvents is used in Li-ion batteries, either with a separator or as a component in a polymer gel. However, it is difficult to obtain conformal coatings of either the separator or the inert polymer gel component onto complex substrates, both at the nano- and micro-scale. When miniaturizing the battery, new methods are therefore required. Another drawback with liquid electrolytes is that these are prone to leakage and harmful sidereactions with the electrode materials. The problem of finding a suitable, solid-state electrolyte is therefore crucial in many of the currently studied 3Dmicrobatteries approaches. Polymeric and inorganic solid electrolytes have been extensively investigated, but their major drawback is that the conductivity values achieved are too low respecting to those of lithium salts in organic solutions. The suitable combination of inorganic and organic materials into hybrid nanostructured thin film electrolytes could result in an interesting combination of properties able to substitute the liquid electrolyte: they are amorphous at room temperature, which causes comparatively higher conductivities, and they provide higher mechanical and thermal stability than pure organic matrices. In this work, we report on the preparation and properties of a new silica-epoxi hybrid ionic conductor, using a sol-gel approach. Tetraethyl orthosilicate (TEOS), 3-glycidoxypropyltrimethosysilane (GPTMS) and lithium acetate have been used as precursors. Optimization of the processing parameters leads to homogeneous coatings of several microns. Small Angle X-ray Spectroscopy (SAXS) was performed with synchrotron light on these coatings, in order to characterize the size distribution of particles, even sub-nanometric and small clusters (1). No evidence of lithium agglomeration as clusters was observed. Preliminary impedance measurements show an increase of the ionic conductivity with the temperature, reaching 10-5 S/cm at 120ºC.