This tutorial review provides a brief summary of recent research progress on carbon-based electrode materials for supercapacitors, as well as the importance of electrolytes in the development of supercapacitor technology. The basic principles of supercapacitors, the characteristics and performances of various nanostructured carbon-based electrode materials are discussed. Aqueous and non-aqueous electrolyte solutions used in supercapacitors are compared. The trend on future development of high-power and high-energy supercapacitors is analyzed.

Graphene is an emerging carbon material that may soon find practical applications. With its unusual properties, graphene is a potential electrode material for electrochemical energy storage. This article highlights recent research progress in graphene-based materials as supercapacitor electrodes. With a brief description of the working principle of supercapacitors, research progress towards the synthesis and modification of graphene-based materials, including graphene oxide, fullerenes, and carbon nanotubes, is presented. Applications of such materials with desirable properties to meet the specific requirements for the design and configuration of advanced supercapacitor devices are summarized and discussed. Future research trends towards new approaches to the design and synthesis of graphene-based nanostructures and architectures for electrochemical energy storage are proposed.

The oxygen reduction reaction (ORR) is one of the most important electrochemical reactions in energy conversion and storage technologies, such as fuel cells and metal–air batteries. However, the sluggish kinetics of the ORR is a key factor limiting the performance of these energy storage and conversion devices. Perovskite oxides are a promising family of electrocatalysts for the ORR because of their unique physical and chemical properties, such as variable crystal structure and non-stoichiometric chemistry. Studies have shown that the catalytic properties of perovskite oxides in the ORR are largely related to oxygen vacancies, which alter their electronic and crystal structures and surface chemistry. This review summarizes recent research advances on understanding the role of oxygen vacancies of the ABO₃ perovskite oxides in catalyzing the ORR. With a brief introduction of perovskite oxides, approaches to creating oxygen vacancies in the ABO₃ perovskite oxides and the role of oxygen vacancies in improving their catalytic performance for the ORR are discussed. Research perspectives in this important area are highlighted.

An asymmetric supercapacitor (ASC) was fabricated using reduced graphene oxide (RGO) sheets modified with ruthenium oxide (RGO–RuO₂) or polyaniline (RGO–PANi) as the anode and cathode, respectively. The ASC exhibited a significantly improved capacitive performance in comparison with that of the symmetric supercapacitors fabricated with RGO–RuO₂ or RGO–PANi as the electrodes. The improvement was attributed to the broadened potential window in an aqueous electrolyte, leading to an energy density of 26.3 W h kg⁻¹, about two-times higher than that of the symmetrical supercapacitors based on RGO–RuO₂ (12.4 W h kg⁻¹) and RGO–PANi (13.9 W h kg⁻¹) electrodes. In addition, a power density of 49.8 kW kg⁻¹ was obtained at an energy density of 6.8 W h kg⁻¹.

The ever-increasing demands for energy and environmental concerns due to burning fossil fuels are the key drivers of today's R&D of innovative energy storage systems. This paper provides an overview of recent research progress in graphene-based materials as electrodes for electrochemical energy storage. Beginning with a brief description of the important properties of single-layer graphene, methods for the preparation of graphene and its derivatives (graphene oxide and reduced graphene oxide) are summarized. Then, graphene-based electrode materials for electrochemical capacitors and lithium-ion batteries are reviewed. The use of graphene for improving the performance of lithium–sulfur and lithium–oxygen batteries is also presented. Future research trend in the development of high-power-density and high-energy-density electrochemical energy storage devices is analysed.