Rational Design of Nanostructured Electrode Materials for High-performance Supercapacitors

Abstract

As is well known, the update of various electronic products is getting faster and faster to meet the requirements of electronic market. In this proposed circumstance, supercapacitors with high performance including energy density, power density, cycling stability, long shelf duration and short charging time, are highly demanded. Moreover, as a sustainable development strategy requested, it is also necessary to consider the environmental benignity, low cost and natural benignity when designing supercapacitor electrode materials. In this thesis, a novel electrode material of supercapacitors is designed and investigated to solve the problems that are commonly encountered among current energy storage technologies. Partially graphitized hierarchical porous carbon was combined with manganese dioxide to use as supercapacitor electrode material, providing both high power density and energy density. Manganese dioxide has been studied and proven to be a suitable potential electrode material for supercapacitors due to high theoretical specific capacitance, low cost, non-toxicity and a large reservation in nature. Combining the carbon framework with transition metal oxide is an effective method of increasing the total conductivity of electrodes. Thus, special carbon substrate was synthesized with the aerosol assisted spray drier method using sucrose as the carbon precursor, TEOs and colloidal silica as dual templates. A hierarchical nanostructured porous carbon was achieved, in which were two types of pores with different diameters. On one hand, the large pores in this material mainly aim to establish rapid ion transfer channels, which is beneficial for the rate capability. On another, the small pores are fabricated to increase the total specific surface area, which is significant to the capacity of supercapacitors. Owing to the unique design, a specific capacitance of 412 F/g has been achieved with a good rate capability and cycling stability. A cycling test which was conducted at the current density of 1 A/g showed that 88% of initial capacitance was retained after over 4000 cycles.