Monday, 20 June 2016
Riverside Center (Hyatt Regency)
The quest for higher energy density Li-ion batteries pushes toward ‘high voltage’ cathode operating above 4.5V. However, if such materials have been proposed for many years in the case of LiNi0.5 Mn1.5 O41 or more recently for LiCoPO4F2, the implementation of such materials is currently prevented by the lack of adapted electrolyte. Several reports deal with high voltage electrolytes such as ionic liquids, dinitrile compounds or fluorinated carbonates. Yet, another class of solvents investigated are the alkyl sulfone, linear3 or cyclic4. Among them, sulfolane, despites its high viscosity has been reported to allow low potential anode operation (such as Li metal or graphite), while other reports point out the high oxidative stability of the electrolytes made thereof4, which was explained based on fundamental studies such as QC5 and MD6. Mixtures of sulfolane seem able to allow room temperature operation of both graphite and high voltage electrodes but no report can be found of a sulfolane-based electrolyte compatible, at the same time, with graphite and a high voltage electrodes. Thus, we examine here the possibility of forming new electrolyte system, based on sulfolane/DMC mixtures for room temperature operation. In particular, the role of the Li salt has been investigated as it is known to play a role on conductivity, via viscosity and dissociation in a solvent system that has a lower dielectric constant and higher viscosity than alkyl carbonate mixtures such as EC/DMC. In addition, keeping the application in mind, SEI building on graphite and aluminum current collector corrosion are also dependent on the Li salt or mixture used. Thus several inorganic and organic Li salts have been investigated in terms of conductivity and electrochemical stability and tested versus graphite and LiNi0.5 Mn1.5 O4 electrodes in a DMC/sulfolane mixed solvent.
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The research presented is part of the ‘SPICY’ project, funded by the European Union’s Horizon 2020 research and innovation programme under grant agreement No 653373.