Symmetric/Asymmetric Supercapacitor Based on the Perovskite-type Lanthanum Cobaltate Nanofibers with Sr-substitution

Highlights: • The nanofiber possessed excellent performance (747 F g⁻¹) in Na₂SO₄ electrolyte • The symmetric and asymmetric supercapacitor device were firstly prepared • The maximum energy density is 34.8 Wh·kg⁻¹ with power density of 400 W·kg⁻¹ • This symmetric supercapacitor also shows an excellent cycling life (97% retention) - Abstract: In this study, we synthesize the La_xSr_1−xCoO_3−δ (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 747.75 F·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 ∽97% and ∽80% specific capacitance retention after 2000 cycles, respectively.