Graphene-related materials for electrochemical capacitors

Abstract

The research described throughout this doctoral thesis has been carried out at CICenergiGUNE, an Energy Cooperative Research Centre, located in Miñano (Alava,Spain).Doctor Javier Carretero-González and Professor Teófilo Rojo Aparicio have beenthe supervisors of this work. During the development of this thesis and as part ofthe doctoral training, Miss Adriana M. Navarro-Suárez, the PhD candidate, hascarried out a 6-month stay at A.J. Drexel Nanomaterials Institute (Philadelphia,USA). Professor Yury Gogotsi is the founder and director of this institute.In the development of this doctoral thesis, the PhD candidate has explored thepotential applications of graphene-related materials for electrochemical energystorage (EES), specifically in supercapacitors. Supercapacitors are expected tofind many forthcoming applications in hybrid electric vehicles and other loadlevellingapplications. In order to achieve that end, their energy density must bemaximized while the power capability continues intact. In the constantly changingtechnological landscape, it is relevant to face new strategies and mechanisms toachieve high energy density materials. Hence, in this thesis, the preparation ofinnovative redox active materials along with their nanostructuration withgraphene or other nanomaterials to lead a high energy and high powerdensity electrode in supercapacitors were our main goal.Graphene has a large theoretical specific surface area and a very high intrinsicelectrical conductivity in plane as well as high mechanical strength and chemicalstability. Because of these characteristics, graphene has been projected to providebetter means for storing electricity. In this thesis, we explored and evaluated newelectrode materials that either showed graphene-type structure or contained directlygraphene layers. By using these materials, we expected to develop supercapacitorsthat exhibit double-layer capacitance, redox pseudo-capacitance, extrinsic redoxpseudo-capacitance, or intercalation pseudo-capacitance.To this end, this Doctoral Thesis has four defined objectives.1. Synthesis of a nanoporous carbon with graphene-like structure to use it asdouble-layer capacitors.2. Design, characterization and development of novel polymer-graphene cellswith enhanced redox-pseudocapacitive behaviour.3. Synthesis of an electrochemically active polymer as electrode material andthe nanostructuration of the electrode by introducing low-dimensionalcarbon nanostructures.4. Development of an asymmetric supercapacitor with two 2D nanomaterialsshowing intercalating pseudocapacitance.