Electrochemical impedance spectroscopy characterization of LiFePO4 cathode material with carboxymethylcellulose and poly-3,4-ethylendioxythiophene/polystyrene sulfonate

摘要

Novel cathode material compositions based on lithium iron phosphate (LFP) were prepared using conducting polymer dispersion poly-3,4-ethylenedioxythiopeneipolystyrene sulfonate (PEDOT:PSS) and water-based carboxymethylcellulose (CMC) as a binder solely and in mixture PEDOT:PSS/CMC. The electrochemical properties of materials in lithium-ion batteries were investigated by galvanostatic charge-discharge curves and by electrochemical impedance spectroscopy and the results were compared with conventional PVDF-bound material. Our best materials consisting of 92 wt% of C-LiFePO4, 4 wt% of carbon black and 4 wt% of conducting polymer binder exhibited excellent rate capability with discharge capacity 148 mAh g(-1) (at 0.2C, normalized by the electrode mass), 143 mAh g(-1) at 1C and 128 mAh g(-1) at 5C as well as good cycling stability at 1C (less than 1% decay after 100 cycles).