Electrochemical Properties Of The Composites Of Reduced Graphene Oxide And LiCoO₂?rGO/LiCoO₂?

Since it was recognized as a cathode material by Goodenough in1980,LiCoO₂ has been widely used in commercialized lithium ion battery.Owing to its high volume density(1.7².9 g cm^-3),high working potential?³.8 V Li/Li⁺?and simple production process.However,as the same as other cathode materials,LiCoO₂ has limited electrical conductivity(10^-3 S cm^-1)and the low Li⁺diffusion rate,which lead to relatively poor rate capability and charge/discharge stability.In this work,the composites of LiCoO₂ particle and reduced graphene oxide?rGO?were prepared to improve its electrical conductivity and Li⁺diffusion rate,which was helpful to enhance its electrochemical performances.The detail research works are following:?1?The rGO was used to modify the surface of commercial LiCoO₂and the composites of rGO/LiCoO₂ with the three-dimensional conductive network were prepared.We studied the influence of reaction time and mass ratio on the preparation and electrochemical performance of rGO/LiCoO₂ composition respectively.Furthermore,the effects of different reduction degree of GO on LiCoO₂ had also been investigated systematically.And the results showed that the discharge capacity of rGO/LiCoO₂ reached to 106 mAh g^-1 at 5 C when the mass ratio of rGO to LiCoO₂ was 5:1000.The micro-morphology and structure of rGO/LiCoO₂ composites were characterized by FE-SEM,FTIR and Raman.The rate capability and cycle stability of them were tested on LAND-CT2001A electrochemical workstation?Wuhan,China?.And the kinetics performances were performed on electrochemical working station?PGSTAT 302N??Metrohm,Switzerland?at 23?.?2?To investigate the effects of the lateral sizes and basal plane structure of graphene on the electrochemical properties of LiCoO₂,the rGO,prGO and GQDs were prepared and used to form rGO/LiCoO₂,prGO/LiCoO₂,GQDs/LiCoO₂ composites,their electrochemical performances were studied systematically.The surface morphology of rGO,prGO,GQDs and three kinds of composition were characterized by AFM,FE-SEM and TEM.The electrochemical performances including rate capability and cycle stability and kinetics performances were tested on LAND-CT2001A electrochemical workstation?Wuhan,China?and electrochemical working station?PGSTAT 302N??Metrohm,Switzerland?respectively.The results showed that the rGO/LiCoO₂ had the better electrochemical performances.That was because the nanopores in prGO could destroy the electron conjugate state of the rGO basal plane,which determined the overall physical/chemical properties including the electron and ion conductivity.And for GQDs,the limited rate capability and cycle stability had been improved owing to its small coating surface area.In summary,the electrochemical properties of rGO/LiCoO₂ were not only influenced by the reaction time and mass ratio of rGO and LCO,but also affected by the lateral size and surface morphology of rGO.Which was useful to enhance the electrochemical performances of LCO and other cathode materials.