ИСТИНА

With the rapid development of renewable energy sources, such as the wind and the sun, large-scale electric energy storage systems are becoming extremely important to realize the smooth integration of these intermittent energies into the grid. Among the potential energy storage technologies, electrochemical secondary battery technology is one of the most promising means of storing electricity on a large-scale because of flexibility, high energy conversion efficiency and simple maintenance. So far, lithium-ion batteries are the most successfully developed technology, have been widely used in portable electronic devices and have been regarded as the best choice for (hybrid) electric vehicles. The latter application raises concern for a possible shortage of the limited lithium resources in the Earth’s crust. Therefore, alternatively, room-temperature sodium and potassium-ion batteries have again aroused a great deal of interest recently, particularly for largescale stationary energy storage applications, due to the practically infinite sodium and potassium resources and their low cost.