HIGH-VOLTAGE DURABILITY AND DEGRADATION MECHANISM OF SEAMLESS ACTIVATED-CARBON ELECTRODE FOR ELECTROCHEMICAL CAPACITORS

摘要

The electric double layer capacitor(EDLC)is an electrochemical energy-storage device with high power density.In the EDLC,the higher voltage operation than 3 V is required for improving the energy density and achieving more reliability,but electrochemical decomposition during high voltage charge causes the decrease in the capacitance and the increase in the internal resistance through i)the micropore blocking by the decomposition products,ii)the destroy of capacitor cell by the gas evolution,or iii)the breakdown of electric network in the electrode.The authors are focusing on the suppression of the breakdown of electric network.The conventional EDLC electrode,which is composed of the activated carbon powder,carbon black,and binder(Fig.l(a)),is easily deteriorated by the breakdown of electric network at high voltage charge.Thus,the author's newly proposed the seamless structure of the activated carbon electrode containing no particle-boundaries(Fig.1(b))to realize high durability against higher voltage charge for the EDLC [1].Fig.2 shows the Ragone plot of the EDLC using seamless activated carbon electrode before and after the floating durability test with high voltage charge(3.5 V,100 h,70 C).The excellent durability,which is demonstrated using seamless activated carbon electrode,is derived from the electrochemical stability against the breakdown of electric network in the electrode.