Study On The Effect Of Mesoporosity On Electric Capacity Performance

Electrochemical capacitor is a new energy storage component between storage battery and staticcapacitor, which has such advantages as high power density, long cycle life, broad workingtemperature range, etc. Electrode material is a key effect factor on performance ofelectrochemical capacitor, so it has become a hotspot in research. Due to the advantages of highspecific surface, stable electrochemical performance, low cost, activated carbon becomes thepreferred material for EDLC. To a large degree, the special capacitance of a EDLC depends onthe pore structure and surface functional groups of the activated carbon used, so to get highestspecial surface area and optimal pore structure is important.A series of mesoporous activated carbons with narrow pore size distribution have beenprepared via template method using synthetic resin as carbon precursor. The structure andmorphology of the samples were characterized by N2 adsorption and scanning electronmicroscopy (SEM). The carbons prepared have high special surface (1060.33～1948.80 m2/g) ,and the average diameters of the carbons are 2～4 nm. The effects of the activation temperatureand activation time on the yield and pore structure of the activated carbons were studied. It wasfound that with the rising of activation temperature, the yield decreased, while the mesoporevolume increased and micropore volume decreased. With the extending of activation time, theyield decreased, while the mesopore volume first decreased and then increased, and microporevolume first increased and then decreased. The capacitance properties of the carbons have beenstudied by cyclic voltammetry, charge-discharge in a constant current and leakage current test.The effect of the pore structure on the capacitance was studied. The carbons show idealcapacitance properties. When charge and discharge with high current density, the specificcapacity of sample AC02 is 214.7 F/g, and the efficiency remains above 87%.A model hybrid capacitor was fabricated usingβ-Ni(OH)₂ and activated carbon as positiveelectrode and negative one materials respectively. The electrochemical performance of the hybridcapacitor and the EDLC was compared by electrochemical tests. It is suggested that:β-Ni(OH)₂electrode has outstanding Faradaic pseudocapacitance. Compared to the carbon electrode,β-Ni(OH)₂ electrode has higher faradaic impedance, higher special capacitance by 77.0%, andhigher power density by 116%.The results of this study provide a technical basis for preparation and characterization ofmesoporous activated carbons, and provide a reference for further research and application.