Energy storage, in fact, could be dated back to ancient times. Mankind initially made fire using wood and charcoal, which are biomass energy storage carriers of solar energy and acted as one of the most important driving powers for ancient civilization. Then came coal and petroleum, which also store solar energy from buried plants in a much higher density than wood or charcoal to power steam engines and vehicles and to generate electricity. With the rapid development of economy and the increase of global population, the energy consumption has been dramatically increasing and its consumption manner is diversified. High-performance energy storage techniques are needed to enable efficient, versatile, and environmentally friendly uses of energy including electricity. Therefore, various energy storage systems are being developed aimed at proper utilization of different energy sources. In particular, popularization of portable electronics and electric vehicles worldwide stimulates the development of various energy storage devices, such as batteries, supercapacitors, solar cells, fuel cells, and thermoelectric devices, toward higher power density and energy density, which significantly depends upon the advancement of new materials. Therefore, energy storage science and technology are recognized as one of the most important parts of energy science and technology, while energy storage materials are taking the core position. In spite of such high demands, no journal specialized on energy storage materials exists.