An asymmetric supercapacitor includes a negative electrode made of a first carbon, a positive electrode made of a soft carbon, a separator and an electrolyte. The separator is disposed in between the negative and positive electrodes. The soft carbon has an activation threshold (AT) larger than 1400, and the activation threshold (AT) is obtained from the following formula: AT = La* (Aa/Ac). La is an in-plane correlation length of the soft carbon, Aa is an area of amorphous peak of the soft carbon analysed by X-ray diffraction in Gaussian distribution graph, and Ac is an area of crystalline peak of the soft carbon analysed by X-ray diffraction in Gaussian distribution graph. |