To effectively enhance the energy density and cycling life of supercapacitors, we propose a novel strategy to use La0.85Sr0.15MnO3 as the core and encapsulated it with NiCo2O4 nanosheets to grow La0.85Sr0.15MnO3@NiCo2O4 (LSM15@NC) core–shell nanoflowers on Ni foam for the first time. Here, we systematically study the effect of KOH electrolyte concentration on the electrochemical behavior of LSM15@NC electrode. It manifests ultrahigh capacitance of 1341 F g−1 in 6 M KOH, which is around a threefold increase compared to that of 1 M KOH (400 F g−1 at 0.5 A g−1). Asymmetric supercapacitor assembled with activated carbon (AC) as negative electrode possesses remarkable performance with a wider work voltage of 1.8 V and maximum energy densities of 63.5 Wh kg−1 at a power density of 900 W kg−1. Even at ultra-high power density of 57600 W kg−1, it still retains high energy density of 25.2 Wh kg−1. Most importantly, it exhibits outstanding cycling life (retaining twice as much as the initial capacitance after 10,000 cycles), either as a single electrode or assembled asymmetric supercapacitor, much better than previously reported.