Modification of nanoporous structure and surface of carbon electrodes for use in power storage systems

Method for modification of nanoporous structure and surface of carbon materials to be used as supercapacitor electrodes has been developed and optimized as to the microwave treatment (MWT) regimes. Mechanisms of MWT due to the dielectric and Maxwell-Wagner polarization effects have been discussed. It has been found that due to the dielectric polarization and a fast increase in temperature inside pores, which were saturated with etching agents (water, oxalic or formic acid) beforehand, the selective pore etching “from inside” can occur that increases the pore size and, as a result, increases the electrostatic capacitance of supercapacitors by 20%. Processes of pore structure development have been optimized as to the treatment duration and the carbon material grain size. It has also been shown that the pore surface can be modified with Nitrogen heteroatoms due to the MWT of carbon and melamine powder mixtures. This modification enables to step up the supercapacitor rated voltage from commonly used 2.7V to 3.0V that additionally increases the supercapacitor energy density by 23%. Yet another advantage of MWT is a significant reduction in treatment duration (from hours to minutes) and in energy consumption; besides, the loss of carbon material does not exceed 10% due to the mostly “from inside” etching process.