Tailored carbon aerogels as positive electrodes in Li-ion capacitors: Porosity analysis for a suitable electrochemical performance

Nowadays, carbons are reaching high attention in the field of materials science due to their low cost and good availability. However, in most of their potential applications, specific characteristics are required for their good performance. The properties of natural carbon materials sometimes are not easy to modify as they are directly related to their precursor source. Carbon aerogels are promising materials to solve this drawback as their porosity can be easily tailored by selecting suitable initial conditions during the synthesis. Although these materials have been already employed in a wide range of applications, the combination of a well-developed porosity with high electrical conductivity, normally opposite characteristics in carbon materials, makes them suitable candidates for being used in high-power electrochemical devices. In this sense, carbon aerogels might be of interest for a technology such as lithium-ion capacitors, which, despite having reached the market, still require improvements to trigger their expansion. In the present study, carbon aerogels are used as positive electrodes, in which it is observed that micropores are essential to attain high capacitances at low current densities and that the presence of mesopores is a key factor for the stability of the device in the range of medium-high current densities. However, a certain diameter of mesoporous is essential for their effectiveness.