Abstract <p>Phosphorus-doped MnCo₂S₄ hollow spheres with a heterogeneous, nanosheet-assembled architecture were synthesized via a simple gas–liquid diffusion method under ambient conditions, in contrast to conventional hydrothermal and gas-phase phosphating techniques. Ammonia diffusion into a homogeneous manganese–cobalt sulfate solution led to the formation of well-dispersed hollow spheres with lamellar structures, promoting efficient electron transport and enhanced electrochemical activity. Phosphorus atoms partially substituted sulfur in the lattice, generating abundant vacancies that improved conductivity and charge transfer kinetics. The resulting electrode exhibited a high specific capacity of 928.2 C g^–1 at 1 A g^–1 and excellent cycling stability, retaining 93.8% of its capacity after 10 000 cycles. A hybrid supercapacitor was assembled using the phosphorus-doped MnCo₂S₄ as the cathode and activated carbon as the anode in 6 M KOH electrolyte. The device delivered a specific capacity of 225.6 C g^–1 at 1 A g^–1, retained 75.5% capacity at 30 A g^–1, and achieved a high energy density of 55.8 Wh kg^–1 with a power density up to 24453.6 W kg^–1, demonstrating excellent rate performance and long-term stability.</p>