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Highlights • Coral-like NiCoP@C@Ni(OH) 2 nanoarrays are vertically grown on nickel foams. • The cycling performance of NiCoP@C@Ni(OH) 2 has been increased from 53.5% to 81.2%. • Hybrid supercapacitor delivers a high energy density of 49.5 Wh kg−1 at 399.8 W kg−1. Abstract Transitional metal phosphides (TMPs) are regarded as comparatively promising electrode materials for energy storage and conversion. However, the poor cycling performance of TMPs remains to be a major challenge of their practical application for supercapacitor. In this work, coral-like NiCoP@C@Ni(OH) 2 core-shell nanoarrays are vertically grown on nickel foams using two-step hydrothermal reaction, followed by carbonization and phosphorization treatment. The participation of amorphous carbon layer and ultrathin Ni(OH) 2 nanosheets is expected to improve the performance of cycling stability and energy density. This NiCoP@C@Ni(OH) 2 NAs exhibit high specific capacitance of 2300.8 F g−1 at a density of 1 A g−1, good rate capability (72.1% of capacitance at 20 A g−1) and long-term cycling stability (81.2% retention after 3000 cycles at 10 A g−1). Moreover, with the help of ultrathin Ni(OH) 2 nanosheets, a hybrid supercapacitor assembled by the NiCoP@C@Ni(OH) 2 NAs electrode against activated carbon achieves a high energy density (49.5 Wh kg−1 at a power density of 399.8 W kg−1). These results demonstrate that such NiCoP@C@Ni(OH) 2 NAs hold great promise as novel battery-like electrode for hybrid supercapacitors in energy conversion. [ABSTRACT FROM AUTHOR]

• The unique nanoarchitecture with PBA-derived nanocubes anchored on nanowires and nanoflakes are rationally constructed. • The proper P incorporation in (Ni,Co)Se 2 could greatly increase the electrochemical properties. • The operating potential of hybrid supercapacitor could be extended to 1.8 V. • The P-(Ni,Co)Se 2 //ZC device shows a high energy density of 45.0Wh kg−1 at the power density of 446.3 W kg−1. Nanostructure construction and composition tuning are two effective methods to accelerate electrochemical reaction kinetics and increase electroactive sites of nickel cobalt selenides nanoarrays. Herein, we have successfully designed and fabricated the P-(Ni,Co)Se 2 nanoarrays on activated carbon cloth with PBAs nanocubes anchored on the nanoflakes-nanowires by a facile hydrothermal method, followed precipitate reaction and phosphorization/selenylation treatment. The continuous hollow PBAs nanocubes and proper P incorporation in (Ni,Co)Se 2 could greatly increase active surface area and enhance the ions diffusion and charge transfer. The resultant P-(Ni,Co)Se 2 NAs electrode delivers a high areal capacity of 3.02C cm−2 (a specific capacity of 755C g−1) at 2 mA cm−2 and a good rate capability (2.61C cm−2 at 30 mA cm−2). Furthermore, the all-solid-state hybrid supercapacitor device is also constructed by using P-(Ni,Co)Se 2 NAs and ZIF-8 derived carbon as positive electrode and negative electrode, respectively, which shows a high energy density of 45.0 Wh kg−1 at the power density of 446.3 W kg−1. This work offers new strategies to synthesize transition nickel cobalt selenides for high performance supercapacitor devices. [ABSTRACT FROM AUTHOR]