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The intelligent construction of electrode nanostructures with unique morphologies is of admirable importance for increasing the energy storage capacity of highly efficient supercapacitor devices. In this study, the negative electrode material Bi2O3/Bi2Se3 nanoflower (Bi2O3/Bi2Se3 NFs) hybrid was first fabricated via a simple one-step solvothermal approach; due to the favorable conductivity of Bi2Se3, high theoretical capacity of Bi2O3 and their distinctive nanostructures, the achieved Bi2O3/Bi2Se3 NFs exhibited the maximum specific capacity of 132.7 mA h g−1 (∼531 F g−1) at 1 A g−1 and the superior rate capability of 113.8 mA h g−1 (∼455 F g−1) at 10 A g−1. Moreover, the positive electrode material NiCoSe2/Ni0.85Se nanoparticles (NiCoSe2/Ni0.85Se NPs) obtained by an electrodeposition method delivered the high specific capacity of 248.4 mA h g−1 (∼1788 F g−1) at 1 A g−1 as well as the appealing rate property of ∼84% capacity retention when the current density was increased by 100 times (i.e., 100 A g−1). More significantly, it was found that the assembled Bi2O3/Bi2Se3 NFs//NiCoSe2/Ni0.85Se NP asymmetric aqueous battery (AAB) device achieved the extraordinary energy density of 88.4 W h kg−1 at the power density of 2.4 kW kg−1 along with a durable lifespan (maintaining the capacity retention of up to 91.5% even after 10 000 cycles). Consequently, the design strategy and novel perspectives reported herein not only hold extensive promise for expanding the preparation techniques of morphology-controlled composites with robust electrochemical properties but also promote the practical applications of newly emerging metal selenides in next-generation aqueous batteries. [ABSTRACT FROM AUTHOR]