A High-performance Cathode Of Three-Dimensional Graphene@CuCo₂O₄ Microflower For Li-O₂ Batteries

With the development of society and the advancement of science and technology,people’s demand for energy is also increasing.The increasing shortage of traditional petroleum resources has made the development of new energy systems an urgent need.Among them,Li-O2 batteries with high theoretical energy density have attracted the attention of researchers.The theoretical energy density of the lithium-air battery is close to that of gasoline,and the cathode reactants are oxygen and pollution-free.Therefore,it is expected to become a new generation of energy system to replace gasoline.However,research on Li-O2 batteries is still imperfect,and there are still problems such as high overpotential and poor cycle stability,and the development of a stable and efficient cathode catalyst is considered to be the key to solve the problem.In this paper,a multi-layered graphene with wrinkled structure was grown on a foamed nickel substrate by chemical vapor deposition method.The distribution was uniform and the structure was relatively complete.A three-dimensional graphene was used as the cathode of Li-O2 batteries for electrochemical testing,the ORR onset potential was low,and the reversibility of the battery is general.The discharge specific capacity of the first charge-discharge is 271 mAh/g,the charging voltage platform is about 4.3V,the discharge voltage platform is about 2.4V,and the potential difference is approximately 1.9V.CuCo2O4 microflowers were synthesized on the surface of three-dimensional graphene by hydrothermal method,and 3D graphene@CuCo2O4 MF were prepared.The cathode has a unique hierarchical porous structure,which could provide the enough space for O2 transport and discharge product storage.The Li-O2 battery with 3D graphene@CuCo2O4 MF cathode has a higher ORR onset potential,better reversibility and lower charge-discharge potential difference compared with the three-dimensional graphene cathode.The discharge specific capacity of the Li-02 battery with the composite cathode reach 3278 mAh/g at a current density of 100 mA/g,far higher than the three-dimensional graphene cathode.In addition,the 3D graphene@CuCo2O4 MF electrode has good rate performance,under the current density of 0.4 A/g,the discharge specific capacity can still reach 785 mAh/g.The battery can also sustain 169 stable cycles at 100 mA/g with a limited charge/discharge capacity of 500 mAh/g.Notably,the charging platform was as low as 3.6 V for the first circle.