A comparative study on binders for the expanded mesocarbon microbeads as the positive electrodes of lithium-ion capacitors

Abstract Poly(vinylidene fluoride) (PVdF), carboxymethyl cellulose (CMC), and half-sodiated poly(acrylic acid) (PAANa) are typically selected to examine the influences of polymeric binders on the charge storage performances of expanded mesocarbon microbeads (EMCMB) as the positive electrode in the lithium-ion capacitors (LICs). The surface composition of various EMCMB-coated electrodes before and after electrochemical activation are examined by X-ray photoelectron spectroscopy (XPS). The enhanced and reversible capacitance of EMCMB electrodes after electrochemical activation is examined by various electrochemical tests. In comparison with the electrode using PVdF, electrochemically activated EMCMB electrodes with the aqueous binders show a lower onset potential of electrochemical activation and a lower contact resistance. Both aqueous binders can increase the micro-porosity and specific capacitance of EMCMBs, confirmed by the electrochemical impedance spectroscopic (EIS) test although the electrode using PVdF shows better capacitance retention in the 1000-cycle test.