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Ultrasmall Co₃O₄ Nanoparticles Confined in P, N-Doped Carbon Matrices for High-Performance Supercapacitors

Co₃O₄ nanoparticles with smaller particle size can expose more active sites to react with electrolytes, thereby exhibiting better supercapacitive performance. However, the size of Co₃O₄ nanoparticles is difficult to be effectively controlled in traditional carbon matrices. Herein, P, N-codoped carbon matrices with ultrahigh surface area and abundant nanocavities are used as a novel host to confine the growth of Co₃O₄ nanoparticles. The Co₃O₄/carbon composites with high redox activities of Co₃O₄ are successfully obtained, in which Co₃O₄ nanoparticles are strongly anchored in the carbon matrices, resulting in the enhancement of the composites’ capacitive performance (1310 F g–¹ at 0.5 A g–¹). Meanwhile, the strong anchoring effect of the carbon host on Co₃O₄ nanoparticles because of the rich doping elements and the confinement effect of the nanocavities ensure long-term stability (92% capacitance retention after 5000 cycles). Furthermore, the assembled asymmetric supercapacitor using this composite as the cathode material and activated carbon as the anode material delivers a high energy density of 47.18 W h kg–¹ at 375 W kg–¹.