Ion transport dynamics in ionic liquid incorporated Cu BTC-metal- organic framework based composite polymer electrolyte

摘要

Cu based metal-organic framework (MOF), copper 1,3,5-benzenetricarboxylate (CuBTC) has been incorporated with ionic liquid (IL) 1-butyl-3 methylimidazolium bromide at different wt% to be used as composite nanofiller in poly (ethylene oxide) polymer electrolyte system. Shifting of carboxylate vibrational modes is observed from FTIR and significant changes of binding energies of Cu spin-orbit peaks are obtained from XPS spectra suggesting strong interaction between Cu metal cluster of MOF and Br- anions of the IL. Oscillation periodicity and local coordination structure of Cu K-edge are investigated in k-space and R-space from the scanning XANES and EXAFS spectra. Dielectric modulus spectra show non-Debye relaxation dynamics and optimum ionic conductivity of 5x10(-3)Scm(-1) is obtained for the nanocomposite containing 50wt% IL at 380K. The frequency dependent AC conductivity curves depict ion concentration and temperature independent scaling behavior by collapsing to a single curve. The electrochemical stability and cycling performance increases with increasing IL concentration and attains electrochemical stability of 6.1V with discharge capacity of 152.5mAh/g after 500 cycles at 50wt% of IL.