Improving the performance of lithium ion capacitor by stabilizing anode working potential using CoSe2 nanoparticles embedded nitrogen-doped hard carbon microspheres

Lithium-ion capacitors (LIC) have problems such as the imbalance of electrochemical kinetics between the battery-type anode and the capacitive cathode, and the large change in the working potential of the hard carbon anode during charge and discharge, which limit the improvement of electrochemical performance for LIC. To solve these problems, CoSe 2 nanoparticles embedded nitrogen-doped hard carbon microspheres (NCS-CoSe 2 ) are synthesized and used as the anode material of LIC. Electrochemical tests show that NCS-CoSe 2 has a reversible specific capacity of as high as 500 mAh g −1 at a current density of 1 A g −1, which can effectively stabilize the working potential of the anode. At a high working voltage window of 2.2–4.5 V, the potential change of the NCS-CoSe 2 anode is as low as 0.35 V, significantly smaller than that of the pure hard carbon (0.87 V). Regarding the electrode kinetics, the NCS-CoSe 2 anode is matched with the active carbon cathode well. When the power density rises sharply from 335 W kg −1 to 6700 W kg −1 , the energy density of NCS-CoSe 2 //AC LIC can attain 82 Wh kg −1 (56.9% of initial energy density).