ABSTRACT
In the last two decades, great progress has been achieved regarding the application of Li-ion batteries in various areas. They already dominate the electrochemical energy storage systems used for portable electronic devices and have exhibited potential in the application in electric vehicles and stationary electricity storage in recent years. However, the development of Li-ion batteries for large-scale energy storage, especially electric cars, has encountered a major obstacle, which is its relatively low energy density. Although the development of better electrode materials and the improvement of the manufacturing processes have continuously enhanced the energy density of Li-ions, their current level is still less than 200 Wh kg-1, and a theoretical limitation of 300 Wh kg-1 is anticipated, which is still far less than the energy density of traditional fossil fuels. This means that Li-ion batteries can only sustain electric cars for a small amount of miles after fully charged unless extremely heavy batteries are installed. Therefore, it is urgent to develop new energy storage devices with much higher energy densities than Li-ion batteries.
