Electrochemical Behavior of 3,4-ethylenedioxythiophene as an Anti-overcharge Additive for Lithium-ion Batteries

Abstract

The overcharge protection performance of LiNi0.8Co0.1Mn0.1O2 as the positive electrode materials for the lithium-ion batteries is significantly enhanced by adding 3,4-ethylenedioxythiophene (EDOT) into the electrolyte. The effect of anti-overcharge on LiNi0.8Co0.1Mn0.1O2electrodes are analyzed by microelectrode linear scan voltammetry measurement, electrochemical impedance measurement, constant current charge/discharge and overcharged tests. The cycled electrodes are also tested by scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis. The results show that the EDOT additive can react with the base electrolyte and easily form a polymer layer on the surface of LiNi0.8Co0.1Mn0.1O2 electrodes at a stable platform of 4.4 V (vs Li/Li+ ). The time for the voltage rising to the overcharge state is apparently delayed from 25 h to 58 h. After 100 cycles at 0.5 C rate, the capacity retention rate of the half-cell is increased from 80.1% to 93.4% after adding the EDOT additive. The results demonstrate that this promising anti-overcharged and cyclic performance are attributed to the protective film generated by EDOT which may enhance the interfacial stability of LiNi0.8Co0.1Mn0.1O2/electrolyte.