Lithium ion capacitors (LICs) are hybrid electrochemical energy storage devices which combine the intercalation mechanism of a lithium ion battery with the cathode of an electric double-layer capacitor (EDLC). LICs are quite suitable for applications which require a high energy density, high power densities and excellent durability, including energy recovery systems or start power in transportation systems, such as electric vehicles, high speed rail and inter-city rail transit.  

Researchers from Qingdao Institute of Bioenergy and Bioprocess Technology (QIBEBT), Chinese Academy of Sciences, have developed high performance LICs using graphene based composites as electrodes. They solved the key technologies including pre-doping lithium ions, coating slurries on special current collectors, inhibiting gas release and system integration.  QIBEBT researchers have also developed LIC devices with capacity of 150F, 1000F, 2000F and 3500F. The energy density are above 45 Wh/L based on the volume of the cell. After 20000 times of charge/discharge cycles, the ratio of the capacity retention is as high as 84.3%. Encouragingly, the LICs have been successfully and demonstratively applied to the electric bicycles.  

Next, the researchers will make endeavor to further improve the energy density, adaptability to the harsh environment. The research works are supported by the National High Technology Research and Development Program of China (863 project) and Key Technology Research Projects of Qingdao.