Engineering the defects of Co3O4- bubbles in lotus root-like multichannel nanofibers to realize superior performance and high durability for fiber-shaped hybrid Zn battery

Herein, a lotus root-like nanofibers composed of Co3O4-x bubbles (MCB) with engineered defects is introduced as a novel cathode for hybrid Zn battery (HZB). The nanoscale Co3O4-x bubbles with tailored defects are encapsulated by porous carbon matrix and construct the lotus root-like multichannel structure. The porous and conductive carbon based substrate enables the fast electron/ion transport and facilitates highly reversible redox reaction. In addition, the engineered defects of Co3O4-x bubbles and the multichannels inside the nanofiber provide abundant active sites and ensure the high bifunctional activities towards oxygen evolution/reduction (OER/ORR) reactions. Meanwhile, the good mechanical characteristics and unique structure enable it a good flexible electrode with high areal mass loading and superior electrochemical properties. Accordingly, the MCB nanofiber is a highly efficient platform to synergistically achieve fast kinetics, high energy/power density and excellent durability. For the first time, the formation mechanism of the MCB nanofiber is probed. The relationship between the oxygen vacancies regulated by Kirkendall effect and the electrochemical performance of the electrode is clarified. Moreover, the fabricated fiber-shaped HZB achieves high energy density, superior high-rate capability and long-term cycling stability. Even after high-rate and long-term cycling, it still retains the characteristic two-set charge/discharge profiles and high energy efficiency. More impressively, it exhibits high durability in different outside deformation, working environments or even during working condition transitions.