Co₃O₄/nitrogen modified graphene electrode as Li-ion battery anode with high reversible capacity and improved initial cycle performance

Co₃O₄ nanoparticles are grown on nitrogen modified microwave exfoliated graphite oxide (NMEG) with weight ratio controlled from 10% to 70%. Electrochemical performance reveals that the obtained Co₃O₄/NMEG composite as Li-ion battery anode exhibits improved cycle stability, excellent reversible capacity, high current rate performance, and reduced irreversible capacity loss in the initial cycle compared to pure Co₃O₄ without graphene or Co₃O₄ on thermally reduced graphene oxide (tRG-O). The 70%Co₃O₄/NMEG composite has initial irreversible capacity of 230mAhg^-1 (first cycle efficiency of 77%), and 910mAhg^-1 of capacity is retained after 100 cycles. The 70%Co₃O₄/tRG-O delivers a reversible capacity of 750±20mAhg^-1, and the irreversible capacity loss during the first cycle is 700±20mAhg^-1. Nitrogen functional groups in NMEG, especially pyridinic and pyrrolic N are advantageous for the Co₃O₄ growth. Furthermore, the N modification is effective in reducing the oxygen content of chemically prepared graphene and hence is good for Co₃O₄ dispersion and the amelioration of first cycle efficiency, demonstrating the potential of NMEG based composite as high performance Li-ion battery anode materials.