In this study, we synthesize the LaxSr1-xCoO3-delta (0.3 <= x <= 1) nanofibers (LNF-x) by Electrospun method to improve the energy density of supercapacitor. As well, the structure and electrochemical properties of LNF-x are investigated in detail. As a result, LNF-0.7 sample with high specific surface area possesses the maximum specific capacitance value of 747.75F.g(-1) at a current density of 2 A.g(-1) in 1 M Na2SO4 aqueous electrolyte. In addition, a symmetric supercapacitor and an asymmetric supercapacitor are constructed using the LNF-0.7 as the positive electrode, while the LNF-0.7 and activated carbon (AC) are applied to the negative electrode, respectively. The LNF-0.7//LNF-0.7 device with an extended operating voltage range of 0-1.6 V displays excellent electrochemical performance with a high energy density of 34.8 Wh.kg(-1) at a low power density of 400 W.kg(-1). On the other hand, the LNF-0.7//AC supercapacitor is operated reversibly at a high cell voltage of 2.0 V and exhibits a high energy density of 27.7 Wh.kg(-1) with a low power density of 500 W.kg(-1). Furthermore, the LNF-0.7//LNF-0.7 and LNF-0.7//AC devices have superior cycling stability with similar to 97% and similar to 80% specific capacitance retention after 2000 cycles, respectively. (C) 2015 Elsevier Ltd. All rights reserved.