fabrication processes
In the thesis, we present the fabrication processes of three types of active
materials for electrochemical capacitors. The unique hierarchical pore structure and nanostructure exhibit high performance in energy storage. The results will not only be helpful
to the future design of advanced electrode materials and configurations, but also be
beneficial to better understand the physical and chemical processes at the
electrode/electrolyte interface. Ions in the electrolyte cross the pore space onto the
surface of carbon via diffusion, but too small or tortuous micropores may hinder the ion
transport. For the as-prepared carbon nanofibers, both the outer fiber surface and inner
pores can be accessible for charge accumulation through pores on the surface.
Hierarchical macropores/mesopores in the fiber are also beneficial to accelerate the iondiffusion into inner micropores. In the hierarchically porous carbon design, macro-pores,
meso-pores and micro-pores are combined to achieve improved power density and
energy density at the same time: the macro-pores can minimize the diffusion distance, the
meso-pores accelerates ion-transport whereas the micro-pores contributes to the
capacitance values. Cost is another consideration for electrochemical capacitors to meet
demands of energy storage. The utilization of lignin, the major aromatic constituent of
plant and woods, enables potential applications in low-cost energy storage devices. These
electrodes materials are promising candidates for high-performance electrochemical
capacitors.
