K1.33Mn8O16 nanorods were successfully prepared by a facile sol-gel method with KHCO3, Mn(Ac)(2) and citrate acid as raw materials. The cyclic voltammetry results demonstrate that the K1.33Mn8O16 nanorods exhibit a quasi-reversible K+ intercalation/deintercalation behavior in a 0.5 M K2SO4 aqueous solution. It has also been found that the assembled activated carbon (AC)//K1.33Mn8O16 asymmetric hybrid supercapacitor delivers an energy density of 17.74 Wh kg(-1) at a power density of 210 W kg(-1), and an energy density of 8.18 Wh kg(-1) at a high power density of 2124 W kg(-1). Moreover, the AC//K1.33Mn8O16 supercapacitor shows a good cycling property. To the best of our knowledge, the synthesis of K1.33Mn8O16 nanorods via the sol-gel route and the use of K1.33Mn8O16 in supercapacitors are reported for the first time.