Targeting adequate thermal stability and fire safety in selecting ionic liquid-based electrolytes for energy storage.

The energy storage market relating to lithium based systems regularly grows in size and expands in terms of a portfolio of energy and power demanding applications. Thus safety focused research must more than ever accompany related technological breakthroughs regarding performance of cells, resulting in intensive research on the chemistry and materials science to design more reliable batteries. Formulating electrolyte solutions with nonvolatile and hardly flammable ionic liquids instead of actual carbonate mixtures could be safer. However, few definitions of thermal stability of electrolytes based on ionic liquids have been reported in the case of abuse conditions (fire, shortcut, overcharge or overdischarge). This work investigates thermal stability up to combustion of 1-butyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide ([C1C4Im][NTf2]) and 1-butyl-1-methylpyrrolidinium bis(trifluoromethanesulfonyl)imide ([PYR14][NTf2]) ionic liquids, and their corresponding electrolytes containing lithium bis(trifluoromethanesulfonyl)imide LiNTf2. Their possible routes of degradation during thermal abuse testings were investigated by thermodynamic studies under several experimental conditions. Their behaviours under fire were also tested, including the analysis of emitted compounds.

Fire and explosion hazards related to the industrial use of potassium and sodium methoxides.

Sodium and potassium methoxides are used as an intermediary for a variety of products in several industrial applications. For example, current production of so called "1G-biodiesel" relies on processing a catalytic reaction called "transesterification". This reaction transforms lipid resources from biomass materials into fatty acid methyl and ethyl esters. 1-G biodiesel processes imply the use of methanol, caustic potash (KOH), and caustic soda (NaOH) for which the hazards are well characterized. The more recent introduction of the direct catalysts CH3OK and CH3ONa may potentially introduce new process hazards. From an examination of existing MSDSs concerning these products, it appears that no consensus currently exists on their intrinsic hazardous properties. Recently, l'Institut National de l'Environnement Industriel et des Risques (France) and the Canadian Explosives Research Laboratory (Canada) have embarked upon a joint effort to better characterize the thermal hazards associated with these catalysts. This work employs the more conventional tests for water reactivity as an ignition source, fire and dust explosion hazards, using isothermal nano-calorimetry, isothermal basket tests, the Fire Propagation Apparatus and a standard 20 L sphere, respectively. It was found that these chemicals can become self-reactive close to room temperature under specific conditions and can generate explosible dusts.

Ability of the Fire Propagation Apparatus to characterise the heat release rate of energetic materials.

Energetic materials encompass a wide range of chemical compounds. They react very rapidly releasing large amounts of energy. One of their peculiarities is that they carry an oxidizer and do not require oxygen from the air as their primary reaction partner. The aim of this paper is to present an analysis of the ability to estimate the heat release rate of a sample energetic material using two calorimetric methodologies. The methods are based on Oxygen Consumption and Carbon Dioxide Generation principles. Data have been obtained from experiments carried out with the Fire Propagation Apparatus. First, results from smoke powder combustion tests reveal significant discrepancies between the two approaches. Results from a sensitivity analysis realised in a previous work underlined that the most likely parameters to alter the heat release rate estimation are the energy constants and the concentration of oxygen. Correction procedures have been developed; one based on the estimation of the amount of oxygen supplied by the oxidizer, and a second one based on the calculation of new energy constants accounting for the chemical decomposition of the tested materials. Results are presented in this study.