Structurally Distorted Perovskite La 0.8 Sr 0.2 Mn 0.5 Co 0.5 O 3-Δ by Graphene Nanoplatelet and Their Composite for Supercapacitors with Enhanced Stability

Supercapacitors are promising energy storage devices with high charging/discharging speeds and power densities. To improve their poor stability, we fabricated electrodes by integrating perovskite materials (La 0.8 Sr 0.2 Mn 0.5 Co 0.5 O 3-δ , LSMCO) possessing redox reaction ability with graphene nanoplatelets exhibiting good electronic properties. One of the resultant composites (L25G70) demonstrated high capacitance and excellent capacitance retention (95% after 5000 cycles). These results are superior to other electrodes (L50G45 and L75G20) containing a larger ratio of LSMCO, even L75G20 did not exhibit supercapacitor behavior after 3000 cycles. GN can induce structural distortion in LSMCO, thereby the high amount of adsorbed oxygen per lattice oxygen can explain the best electrochemical performance of L25G70, while structural collapse rationalized the failure of L75G20. The findings of this study demonstrated that the use of LSMCO can improve the cycling stability of supercapacitors.