Synthesis Of Graphene/Manganese Oxide Composites For Lithium-ion Batteries

The electric power storage and transmission is an important part of making full use of renewable energy and solving the current energy and environmental problems around the world.Compared with other energy storage devices,lithium ion batteries have the advantages of relatively mature technology,memory-free effect,light and relative environmental-friendly,which is suitable for large-scale applications in portable electronic equipment,electric vehicles and power grid storage.However,there exist one key factor which restricts further development of lithium-ion battery is the innovation of electrode materials.In this paper,we developed the manganese oxide electrode material,which has the advantage of low-price and environmental-friendly,by controlling the nanocomposites with different morphologies endows them with excellent structural stability and electronic conductivity and applied them to the cathode and negative electrode of lithium ion batteries to study the electrical properties of the nanocomposites.The specific detailed work is as follows:1.By using the oxygen containing functional groups on the surface of graphene oxide,the Li MnO₂-graphene composite（Li MnO₂@r GO）was synthesized by a simple one-pot hydrothermal method.The high theoretical capacity of Li MnO₂ itself and the good electronic transfer efficiency of the reduction of graphene oxide have been greatly enhanced in this way.About the electrochemical performance of this material,especially of the mass specific capacity,the first discharge capacity can be reached up to 175.08 m Ah·g-1 under the 100 m Ah·g-1 current density.The capacity retention rate can be maintained to 80.97% after the 100 cycle.It draws the conclusion that the Li MnO₂@r GO composites prepared by this method have a good application prospect.2.MnO₂ nanowires（MnO₂ NWs）were prepared by a simple hydrothermal method,and then it was endured the second hydrothermal method for the preparation of MnO₂ NWs-three-dimensional graphene composite（3DrGO@MnO₂ NWs）.By a series of structure and morphology characterization,it was found that the material had good onedimensional / three-dimensional interwoven structure and had good structural stability.The study of the electrochemical performance of a half cell assembled with composite materials shows that the 3DrGO@MnO₂ NWs negative electrode has the advantages of small charge transfer impedance and low polarization.At the current density of 300 m Ah·g-1,it is found that the mass ratio of the composites is 5 times as high as that of the MnO₂ NWs pure material electrode,which gives a forceful certify that the 3DrGO plays an important role in the performance improvement of the composite electrode.In addition,the synthetic method reported in this paper has the advantages of simple,easy for operation and suitable for large-scale synthesis,which is of great commercial significance.