Model carbon materials derived from tannin to assess the importance of pore connectivity in supercapacitors

A surfactant-water-assisted mechanochemical mesostructuration method is used to produce model carbon materials with a disordered or ordered mesoporous structure (DMCs or OMCs, respectively) from a sustainable precursor, mimosa tannin. These model materials, differing only in their mesoporous structure, allow assessing the importance of the connectivity of the micro-mesopore network on the electrochemical performance of the resultant supercapacitors (SCs). Connectivity is studied through the scanning of hysteresis loops from nitrogen adsorption-desorption isotherms and, contrary to what it is suggested in the literature, order is not always beneficial for the performance of SCs. A thorough review of the open literature and comparison with our electrodes led us to conclude that CO2-activated DMCs and OMCs are among the best materials reported so far, as they exhibit excellent SC behavior, high-rate capability, and long-term stability in aqueous and organic electrolytes. It is showed that ordered mesopores improve the diffusion of the small-size ions of the aqueous electrolyte and hence favor a better performance at high charging rates, resulting in a 12% higher capacitance retention at 80 A g−1 when compared to that obtained with the disordered materials. However, the more interconnected porosity of the disordered materials allows better diffusion of large-size ions, thus improving the electrochemical performance in the organic electrolyte by 15% at 40 A g−1.