Hybrid battery integrated by Zn-air and Zn-Co3O4 batteries at cell level

The construction of Zn based hybrid battery through the combination of Zn-air and Zn-CoObatteries at cell level is a feasible strategy to integrate high voltage, specific capacity and energy density in one power supply equipment. For Zn based hybrid battery, an efficient cathode material with high specific capacitance and excellent ORR, OER activities is a vital component, which determines its performance in great extent. In this work, with Co based coordination polymer as precursor, oxygen vacancy-rich Co3 O4 based cathode material is synthesized. In this material CoOparticles with the size about 20 to 35 nm reside evenly in mesoporous carbon matrix doped by nitrogen atoms. In OER, the overpotential of this cathode material is merely 330 m V. Its ORR proceeds with a typical four electron process with half wave achieving 0.76 V. If charge/discharge at 1 A·g, specific capacitance of this cathode material is 254.4 mAh·g. As current density increases to 20 A·g, the specific capacitance still arrives at 122.5 mAh·gwith nearly 50% retained. Based on attractive performance of this cathode material, Zn based hybrid battery is assembled. When discharge at 1 m A·cm, it presences two voltage platforms at 1.71 and 1.14 V. In this situation, specific capacitance reaches 790 m Ah·gwith energy density 928 Wh·kg. Hybrid battery shows promising stability after 300-cycle continuous test.