Flexible PEDOT Multi-decorated Co₃O₄ Polyhedrons as Anodes for High-Performance Lithium-Ion Batteries

In this work, a Co₃O₄@PEDOT composite with flexible and conductive poly(3,4-ethylenedioxythiophene) (PEDOT)-coated porous Co₃O₄ polyhedrons is prepared. The hierarchical porous Co₃O₄ polyhedrons are obtained by the treatment of cobalt metal-organic framework (ZIF-67) precursors, and their surface is coated with PEDOT via in situ multistage oxidative polymerization of 3,4-ethylenedioxythiophene. Various characterizations, such as X-ray diffraction (XRD), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), indicate that the Co₃O₄@PEDOT exhibits a core-shell structure. The core is Co₃O₄ polyhedron with a hierarchical porous structure made up of Co₃O₄ nanoparticles, while the shell is composed of amorphous PEDOT. The core-shell Co₃O₄@PEDOT as anode of a lithium-ion battery is tested for charge-discharge performance and exhibits excellent electrochemical performance, delivering capacities of 586 mAh g^-1 and 711 mAh g^-1 at current densities of 0.3 and 1C (1C = 1A g^-1) at 200 cycles, respectively. As a contrast, the uncoated sample Co₃O₄ only has a capacity close to zero (4 mAh g^-1) at 0.3C. These results indicate that the intact and good conductive PEDOT polymer improves the electronic conductive property of Co₃O₄ and ensures the structural stability of the porous hierarchical Co₃O_4. The hierarchical porous core-shell structure can provide the abundant space and pathways, which can alleviate the impact of volume changes and accelerate lithium-ion diffusion dynamics during the cyclic process.