High-performance hybrid supercapacitors enabled by CoTe@CoFeTe double-shelled nanocubes

Metal tellurides, known for their superior electrical conductivity and excellent electrochemical properties, are promising candidates for supercapacitor applications. This study introduces a novel method involving a metal-organic framework hybrid to synthesize CoTe@CoFeTe double-shelled nanocubes. Initially, zeolitic imidazolate framework-67 (ZIF67) and CoFe Prussian blue analog (PBA) nanocubes are synthesized through an anion-exchange reaction with [Fe(CN)₆]^3- ions. Subsequent annealing treatment converts these structures into Co₃O₄@CoFe₂O₄ double-shelled nanocubes. These are then subjected to a tellurization process to form CoTe@CoFeTe, which exhibits outstanding supercapacitive performance. Notably, the CoTe@CoFeTe based-electrode demonstrates superior supercapacitive properties compared to their oxide counterparts, mainly due to the introduction of tellurium ions. These nanocubes show an impressive specific capacity of 1312 C g^-1 at a current density of 1 A g^-1 and maintain 92.35% of their capacity after 10 000 charging cycles, highlighting their durability and the synergistic effect of the mixed metals and their hollow structure. Furthermore, when used as the positive electrode material in a hybrid supercapacitor with activated carbon (AC), the device achieves an energy density of 64.66 W h kg^-1 and retains 88.25% of its capacity after 10 000 cycles. These results confirm the potential of the developed material for advanced supercapacitor applications.