High Capacitance Hybrid Nanomaterials for Supercapacitors Electrodes

摘要

Energy storage systems (ESS) such as lithium ion batteries (LIBs) and electrochemical capacitors (EC) are commercial devices widely used to power all kind of commodity and industrial goods. However, these devices have a limited capacity of storage, and the main reason for this limitation lies on the active material that is commercially available activated carbon (capacitance 80-150 F/g). The amount of energy that is being consumed worldwide grows yearly and projections indicate that this trend will continue exponentially. It is widely accepted that there is an urgent need to produce more powerful and cost-efficient ESS to ease the technological evolutions to come. Graphene is called to lead a technological revolution due to its extraordinary physical properties. Thanks to its very large surface area, electrical conductivity and chemical stability, graphene is the most promising active material to improve the performance of ESS. As a matter of fact, for the last 15 years, scientists and technologists have done a great effort to incorporate graphene in commercial devices. However, graphene is finding a hard time to fit into commercial applications as it tends to restack, losing its large surface area and volumetric capacitance. So far, graphene/metal oxide (MO) hybrid nanomaterials (NMs) have revealed as the best option to overcome this problem. These hybrid structures show a synergistic effect between both phases, taking advantage of the electrical double layer capacitance of graphene and the faradaic surface reactions of the MO. Additionally, the re-agglomeration of each of the phases is hindered by the other, exposing more surface area available for the storage mechanism. In this work we expose the use of two graphene/MO nanomaterials as alternative electrode active materials to activated carbon, currently used in commercial devices. Nanomaterials NM1 and NM2 were prepared by using a proprietary technology and were fully characterized, presenting well defined nanostructured morphologies and high mass purity. The electrochemical performance of these nanomaterials was analyzed in charge/discharge cycles, presenting a hybrid supercapacitor profile and gravimetric capacitance between 150 and500 F/g and an equivalent series resistance of around 3 ohms. Furthermore, high capacitance retention was achieved after many charge/discharge cycles for one of the composites synthesized.