Improved performance of cylindrical hybrid supercapacitor using activated carbon/ niobium doped hydrogen titanate

Abstract A cylindrical hybrid supercapacitor is fabricated using activated carbon positive electrode and H 2 Ti 12-x NbxO 25 (0 ≤ x ≤ 0.6) negative electrode materials. The hybrid supercapacitor using H 2 Ti 11.85 Nb 0.15 O 25 exhibits the best electrochemical performance. It has a capacitance of 78.4 F g −1 , charge transfer resistance (R ct ) of 0.03 Ω, capacitance retention of 91.4% after 1000 cycles at 3.0 A g −1 and energy density of 24.3 W h kg −1 at a power density of 1794.6 W kg −1 . Therefore, the Nb doped HTO negative electrode material is a promising candidate as an energy storage system for electric vehicles (EVs).