The hierarchical architecture of biomass activated carbon and metal oxides has attracted wide attention in the field of energy storage owing to its high specific surface area, good electrical conductivity, low cost and environmental friendliness. Herein, biomass carbon-based porous microsheets with thickness of 150–200 nm are obtained by ultrasonic crushing the carbonized poplar catkins (PC) micro-hollow fibers. The carbon microsheets were modified with polydopamine and further deposited with ultrathin nickel cobaltite nanosheets (NiCo2O4 NSs) to form a NiCo2O4 shell-carbon core sandwich composite. Benefiting from its characteristics, as-prepared hybrid electrodes exhibit significantly enhanced specific capacity (922.9C g−1 at 1 A g−1), excellent rate capability and good cycling stability. Furthermore, the hybrid supercapacitor was also fabricated with NiCo2O4 NSs@PD-PC and polydopamine-modified poplar catkins (PD-PC) carbon materials as positive electrode and negative electrode, respectively. It shows remarkable energy-storage characteristics, such as a high energy density of 39.1 W h kg−1 at the power density of 799.9 W kg−1, only 4.5% capacity loss after 5000 cycles, as well as a wide potential window of 0–1.6 V. Such excellent performance makes poplar catkins-derived carbon-based electrodes promise as one of the attractive candidates for high performance energy storage devices.