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Electrochemical capacitors, also called supercapacitors (SCs), play an important role in the field of electrochemical energy storage and have great potential to become the most advanced power supply for portable electronic devices and electric vehicles. The performance of SCs depends mainly on the properties of the electrode material, and many novel electrode materials have been explored. Clay mineral materials, including montmorillonite, halloysite, and attapulgite, are potential electrode materials due to their layered structure, high specific surface area, natural abundance, low cost, and environmentally friendly nature. However, most of them suffer from low electronic conductivity, which limits their application as high-performance electrodes for SCs. Many efforts have been made to resolve this issue. Here, we summarize a series of clay mineral based electrode materials for SCs. To better develop clay minerals to produce green and pollution-free electrode materials, the structures and properties of minerals are also introduced. In addition, the challenges and prospects of clay mineral materials are also blueprinted.

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Obtaining energy from renewable resources is a powerful measure in eliminating the impact of greenhouse gas and environmental pollution. At present, only 20% of energy comes from renewable energy sources, such as wind, solar, ocean, biomass, and geothermal energy. Sea water is the most abundant natural resource, accounting for more than 97% of total water resources. From a practical standpoint, it is very desirable to use seawater for conversion and energy production. Salinity gradient energy is the chemical potential energy difference between two kinds of water with different salt concentrations. It has a large energy density and is considered to be the most promising ocean energy. Here, we discuss the important features of energy production technologies with salinity gradient energy. The principles and related materials and important finding of the available technologies, such as pressure-retarded osmosis, reverse electro-dialysis, capacitive mixing, concentration capacitor, and mixing entropy battery, have been described in this review. We also found that the current research mainly uses seawater to harvest salinity gradient energy. Because of its high concentration, the salinity gradient energy of salt lake brine is larger, it can be researched by further experiments.