LiTFSI electrolyte system

The highest room temperature conductivity of the electrolyte system d-U(2000) LiTFSIis3.2 x 10 S cm registeredwiththed-U(2000)35LiTFSI composition. This value is similar to that reported by Armand et al. for the POE LiTFSI electrolyte system. The highest conductivity over the temperature range studied was found with the d-U(2000)ioLiTFSI ormolyte, and was recorded as 1.2 x 10 S cm at 95°C (Fig. 5.1). 

These two effects were clearly seen in a study undertaken by Kara et al. [36]. In their work, PPy doped with bis(trifluoromethanesulfonyl)imide (TFSI) was actuated in various water/propylene carbonate (PC) solutions containing LiTFSI. The optimum performance of 23.6 % maximum strain at a strain rate of 10.8 % s was achieved within an actuation solution that consisted of 60 % water and 40 % PC. Improvements in both the strain rate and the maximum strain were seen with actuation in LiTFSI electrolytes of water/PC blended solvents over actuation in electrolytes of either water or PC alone. The improved actuation was attributed to the fact that a greater swelling occurred from the PC solvent (enabling a faster and easier ion transfer) and an improvement in the ionic conductivity from the water solvent (enabling a better charge transfer). As such, the optimised performance for this system was realised at 40 % PC. 

Based on electrolyte systems mentioned-above, traditional liquid electrolytes in Li-S batteries always use the lithium salt of LiTFSI in single or combination of solvents. 

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