Asymmetric hybrid capacitors comprising an activated carbon (AC) positive electrode and a Li4Ti5O12 (LTO) negative electrode can achieve much higher energy density than conventional electric double layer capacitors. However, when operated at 3 V, the positive electrode develops an over-potential, leading to gas generation. Here, we investigated the feasibility of realizing a stable potential at the positive electrode using capacitance balancing. The voltage characteristics of the positive and negative electrodes were measured using a three-electrode system. The linear relationship between the potential and capacitance of the AC electrode was used to balance the capacitances of the two electrodes. Thus, stable operation and enhanced specific capacity were obtained at an operation voltage of 3 V.
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