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

A cylindrical hybrid supercapacitor is fabricated using activated carbon positive electrode and H2Ti12-xNbxO25 (0 ≤ x ≤ 0.6) negative electrode materials. The hybrid supercapacitor using H2Ti11.85Nb0.15O25 exhibits the best electrochemical performance. It has a capacitance of 78.4 F g−1, charge transfer resistance (Rct) 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).