Magnetic field control in the growth process of Co3O4 and its performance enhancement mechanism as an anode material for lithium ion capacitors

Due to the limitations of traditional materials or structures, many materials are difficult to meet usage requirements; therefore, there is an urgent need to develop new material preparation and structural control technologies. This study introduces a magnetic field during the growth process of ZIF-67, which changes the particle size and surface morphology of ZIF-67 and provides nanoscale mesoporous defect-rich Co3O4-M after direct calcination. The mesoporous structure of Co3O4-M provides effective channels for rapid electron transfer and lithium-ion storage, and it increases active-site density; the oxygen-vacancy defects increase the conductivity and pseudo-capacitance contribution. The Co3O4-M electrode exhibits a capacity of 1510 mA h g−1 after 300 cycles at a current density of 0.2 A g−1 and a capacity of 372 mA h g−1 after 1000 cycles at a current density of 5 A g−1, demonstrating excellent cycling stability. At the same time, it shows excellent fast charging and slow discharging performance, and the average charging time of Co3O4-M is 40 min. A lithium-ion capacitors (LIC) with activated carbon as the cathode and Co3O4-M as the anode achieves a high energy density of 322 W h kg−1 and high power density of 4885 W kg−1. After 3000 cycles at a current density of 1 A g−1, the capacity retention of this LIC is 60%.