Phenylphenol-Derived Carbon and Antimony-Coated Carbon Nanotubes as the Electroactive Materials of Lithium-Ion Hybrid Capacitors

Energy storage of the lithium-ion hybrid capacitor can be upgraded through adjusting the mismatched rate qualities between the positive and negative electrodes because the positive electrode of the electrical double layer (EDL) stores and releases electricity in a smaller quantity, yet much faster than the negative battery electrode. To increase the EDL capacity, nitrogen-doped carbon (KPN900) with a hollow-onion structure is prepared with phenylphenol, achieving a surface area above 3000 m² g^-1. The capacitance of KPN900 displays a diffusive component of 57 F g^-1, exceeding its capacitive counterpart at 10 mV s^-1. Moreover, its total capacitance reaches 168 F g^-1 at 1 mV s^-1 with a diffusive component of 112 F g^-1. On the other hand, the power of the negative electrode is improved through electrodeposition of metallic antimony on carbon nanotubes, Sb/CNTs, evidenced by the capacity of ∼250 mA h g^-1 at 1.0 A g^-1. Hence, the capacitor, with a 2:1 mass ratio of KPN900 to Sb/CNT, exhibits an effective trade-off between energy and power, distinct from the one-sided dependence on the carbon electrode of most hybrid capacitors. This capacitor stores 97 W h kg^-1 at a power level 0.12 kW kg^-1 and 17.4 W h kg^-1 at power 7.90 kW kg^-1.