Abstract: In the long river of human history, every technological revolution is accompanied by transition of cognition, development and utilization of energy. At present, China has become the No. 1 in the world in both production and consumption of energy, which continue rising in the excepted future. Developing energy technology is still a key way to solve the problems of excessive dependence on traditional fossil energy and environmental pollution, construct a reasonable social structure, promote the sustainable development of human society, and achieve the goals of carbon emission peaking and carbon neutrality. In 2020, renewable energy in China such as photovoltaics and wind power evolved marvelously which occupied 1/3 of global total volume. In this regard, energy materials are indispensable components, which play the core role in realizing conversion and utilization of clean energy, developing new energy technologies, and supporting the entire energy system.
In recent years, energy materials have achieved extensive and sustainable development in many fields, including secondary batteries, fuel cells, solar cells, supercapacitors, photoelectric catalysis, and energy-containing materials. For example, high nickel ternary materials as cathode material in the lithium-ion battery are leading the future of a new generation of automotive power battery technology towards faster charging speeds, longer service life and longer mileage^[1-4]. The ever increasing demand for energy storage has also spawned simultaneously a series of new battery technologies, such as lithium-sulfur^[5], lithium-air^[6] and solid-state batteries^[7]. They have advantages in energy density, economy and safety, but technical defects (e.g., shuttle effect in Li-S battery attributed to polysulfides, blockage of matrix pores in Li-air battery attributed to discharging product, unsatisfactory electrical conductivity of electrolyte in solid-state battery) are frustrating. Technological improvement and industrialization are strongly dependent on the innovative design and structural optimization of electrode and electrolyte materials. To promote the share of renewable energy in primary source, photovoltaics, the representative of new energy, received great expectation. In addition, halogen perovskite-based third-generation solar cell technology has achieved a solar energy conversion efficiency comparable to that of silicon single crystal, showing a prosperous photovoltaic industry in the future^[8]. However, its sensitivity to temperature, humidity, light, and oxygen^[9], and inevitable Pb-containing raw material in preparation still need to find a solution in the underlying materials design. Moreover, as continuously optimizing the traditional catalyst materials, like Pt and Pd, as well as the non-precious and non-metallic catalysts, the energy conversion efficiency of fuel cells has been gradually improved with reduction of their technical costs, meeting a certain degree of commercial application^[10-11]. Besides, photocatalytic and electrocatalytic technologies for CO₂ reduction and nitrogen fixation also provide a new way for the storage and utilization of renewable energy, technically support the carbon emission peak in 2030 and carbon neutrality in 2060^[12-13].
In the context of the era of sustainable development and the fiercely competitive international scientific and technological frontier research environment, in the energy materials research, including the exploration of physical and chemical properties, functional discovery, precise design and preparation of nanomaterials, and advanced device assembly, China has made many important breakthroughs. In order to focus on displaying the research results of Chinese scholars in this field, to promote academic exchanges among peers, and to stimulate interest in energy materials from all walks of life, Nanjing University of Science and Technology, Shanghai Institute of Ceramics, Huazhong University of Science and Technology, etc. hereby organize the publication of “Energy Materials Special Issue”, containing the latest research articles and reviews related to energy materials involved with perovskite photovoltaics, semitransparent solar cell, Li-ion battery, Mg battery, Li-S battery, thermoelectrics, CO₂ splitting, etc. It is hoped that this Special Issue can offer useful references for the scientific research and disciplinary development of energy materials in China.