A single-phased ringed pyrazolium imide and its potential application for plastic crystal-lithium batteries

A new member of the plastic crystal, pyrazolium imide family, N,N'-pentamethylene pyrazolium bis-(trifluoromethanesulfonyl)imide Pyr7, was prepared. It showed a single, plastic crystalline phase that extends from 47°C to its melting at 75°C. The high conductivity of its neat (1.8×10^-4 S.cm^-1 at 7_1/2= 61°C) and 10 molar% LiTFSI-doped compound (7.9×10^-4 at T_1/2= 55.5°C) along with the wide electrochemical window of Pyr7 ( ∼4.3 V) encouraged us to employ the doped-compound in a lithium-ion battery and good performance was obtained. For the first time, we introduced the σT _1/2 term, which should provide a good tool for the comparison of conductivity values for different compounds at the middle of their plastic crystal range.