Abstract:        Energy utilization includes two aspects of storage and conversion. Both the density of energy storage and the efficiency of energy conversion are particularly considered in the application of energy. It is well known that chemical energy can be easily stored in chemical substances with high-energy density such as those containing hydrogen and lithium. Meanwhile, chemical energy can be highly converted into clean and efficient electrical energy through the systems of electrochemical energy storage and conversion, which include batteries, fuel cells, and electrochemical capacitors (also called supercapacitors). Thus, the combination of chemical energy and electrochemical reactions makes full use of the advantages of chemical energy and electrical energy. Nowadays, systems of electrochemical energy storage and conversion have already played an important role in powering an increasingly diverse range of applications from electronic devices to cars.
       Systems of electrochemical energy storage and conversion depend on the composition and structure of the materials as well as the electrochemical processes involved. However, the existing systems have many problems which are not satisfactory for their ever-increasing applications, such as low reaction activity, limited mass transport and charge transfer, slow kinetics, and uncontrolled surface/interface, as well as the other scientific and technological problems in traditional energymaterials, and cause the low actual energy density and low energy conversion efficiency in current batteries, fuel cells and supercapacitors. No matter how to change the energy structure around the world in future, high-density storage and high-efficiency conversion of chemical energy and electrical energy are two crucial approaches in energy distribution and ultilization. Therefore, the exploration of new key materials for hydrogen or lithium-based systems with electrochemical energy storage and conversion is of importance.
       This special issue collects 21 papers contributed by experts who are very lively in the frontier of academic field of electrochemical energy storage and conversion. It is really an interesting and exciting special issue that addresses on the topics of electrochemical hydrogen or lithium storage, cathode and anode materials for lithium-ion batteries, lithium-sulfur batteries, electrode materials for supercapacitors, electrocatalysis toward oxygen reduction reaction or ethanol oxidation, and electrolyte additives.
       This special issue is dedicated to the research and development of systems with electrochemical energy storage and conversion. It reflects, in a certain degree, the latest research development, progress, problems and future focus on the direction of electrochemical energy storage and conversion. I believe that this special issue should play valuable roles in strengthening the exchanges of scientific workers, and promoting the research development of electrochemical energy storage and conversion.