High Voltage Li-Ion Capacitors in a Fluoro-Ether Based Electrolyte System

The specific capacity of a lithium-ion capacitor (LIC) with an activated carbon (AC) cathode depends on the range of potential during the charge/discharge process, but the electrolyte tends to decomposition when it is cycled in high voltage. An effective additive, fluorinated ethers (FE, HCF2CF2CF2CH2OCF2CF2H), which can inhibit the decomposition of carbonate-based electrolyte has been reported in this paper. The electrochemical measurements indicate that activated carbon exhibits poor cyclic stability when it is cycled under 4.5 V (versus Li/Li+) in the basic electrolyte. This issue can be overcome effectively by adding FE into the basic electrolyte. When the concentration of LiPF6 is increased to 1.1 mol L−1, the half cell exhibited an excellent cyclic performance. Charge/discharge tests indicate that the half cell has displayed outstanding cycling stability of 93.98% capacity retention after 200 cycles in the potential range of 1.5–4.5 V.