Preparation And Electrochemical Study Of TiO₂/Graphene Composites Based Anode Materials For Lithium-ion Battery

In recent years,as a new type of anode materials,metal oxides have been widely investigated as anode materials for LIBs.In this respect,titanium dioxide?TiO₂?has become one of the most attractive anode materias for lithiumion battery because of its environment-friendly and safe stable structure.On the other hand,the massive volume changes during the charge-discharge processes can damage the anodes gradually and further cause electrical short circuit and the falling off or even exploding of the electrode material,TiO₂ has lower volume variation?4%?during the lithiation/delithiation process which favors large-scale energy storage.Unfortunately,TiO₂ has poor electronic and ionic conductivity that limits its application as a high power anode material.Based on the good electrical conductivity of graphene,in this work,the TiO₂/graphene nanocomposites were researched and syntheticed.In this paper,titanium dioxide/graphene composites?TiO₂/rGO?was synthesized from different layers of graphene oxide?GO?and three different sources of titanium?TiO₂,Tetrabutyl titanate,Titanium oxysulfate?using hydrothermal method,and we have prepared various TiO₂ with different morphology,such as rutile TiO₂,anatase TiO₂ and investigated the electrochemical performance of the composites.By using different layers of GO as precursors for preparation of composites,we explored the influence of the layers of graphene and the sources of titanium on the composites for lithium-ion battery.The main conclusions have been summarized as following:?1?Titanium dioxide/graphene composites?TiO₂/rGO?was synthesized from different layers of graphene oxide?GO?and commercial TiO₂ using hydrothermal method,and the structure of TiO₂ is rutile.The test results indicate that the TiO₂/rGO-2?few-layers?electrode exhibit higher electrochemical performance than that of the TiO₂/rGO-1?multi-layers?electrode.At the current density of 100 mA/g,the discharge capacity of TiO₂/rGO-2?few-layers?is 322.3 mAh/g after 100 cycles,and the Coulombic efficiency is still maintained as high as 98.9%,which is superior to that of the TiO₂/rGO-1?multi-layers??240.2 mAh/g?.TiO₂/rGO-2?few-layers?shows reversible capacity values of 285.8 mAh/g and 235.6 mAh/g at current rates of 160 mA/g and 320 mA/g,respectively,showing better rate performance.Compared with TiO₂/rGO-1?multi-layers?composites,the TiO₂/rGO-2?few-layers?composites electrode has the lower SEI film and charge transfer resistance,which is beneficial for the electrochemical performance of the materials.?2?By changing the sources of titanium,TiO₂/rGO composites with anatase TiO₂structure were successfully prepared by using different layers of GO and Tetrabutyl titanate as precursors.The obtained composites showed that many TiO₂ particles are uniformly dispersed on the wrinkled graphene layers,displaying a superior cover of particles on rGO.After 100charge-discharge cycles,the discharge capacity and Coulombic efficiency of the TiO₂/rGO-4?few-layers?composites maintained up 344.3 mAh/g and 99.3%,respectively,and the electrochemical performance was better than that of TiO₂/rGO-3?multi-layers?composites.?3?TiO₂/rGO-5?multi-layers?and TiO₂/rGO-6?few-layers?composites with anatase TiO₂structure were synthesized by using Titanium oxysulfate as titanium source and graphene oxide?GO?as the precursor in the synthesis system.After 100 charge-discharge cycles,the discharge specific capacity of TiO₂/rGO-6?few-layers?was 285.3 mAh/g,and the Coulombic efficiency was 98.6%;at the higher current density of 160 mA/g and 320 mA/g,the discharge capacities of each period for TiO₂/rGO-6?few-layers?are 201.2 mAh/g and 162.5 mAh/g,respectively;however,the discharge capacities of TiO₂/rGO-5?multi-layers?are only 78.9mAh/g and 49.6 mAh/g,respectively.At the same time,the TiO₂/rGO-6?few-layers?electrode exhibited better rate performance than the TiO₂/rGO-5?multi-layers?at all the current densities.?4?By exploring the electrochemical properties of composites prepared from three different sources of titanium?TiO₂,Tetrabutyl titanate,Titanium oxysulfate?using hydrothermal method,the results showed that the composites synthesized with Tetrabutyl titanate as titanium source have better dispersibility.Tetrabutyl titanate is more suitable for the preparation of TiO₂ with relatively homogeneously distributed on the layers of graphene,and good dispersibility is beneficial to the electrochemical properties of the materials.In addition,for three different sources of titanium,the TiO₂/rGO composites prepared by using the few-layers of graphene oxide as the precursor had better electrochemical properties,which indicates that the few-layers graphene is more suitable for application in electrode materials.