The Preparation Of TiO₂ Nanosheets And The Application Of Its Carbon Composite Materials In Anode Materials For Lithium Ion Batteries

Two-dimensional ultrathin nanosheets have attracted wide attention due to its novel physical,chemical properties,and unique two-dimensional crystal structure.Graphene,which has received much attention,is an ultra-thin two-dimensional carbon nanomaterial,as the basic structural unit of layered graphite.Such ultrathin carbon nanosheets can also be obtained by exfoliating its layered precursor graphite.During the past two decades,scientists have published many works about ultrathin nanosheets with a similar two-dimensional structure which can also be obtained via the exfoliating process.However,this material suffers a big problem that how to regulate the structure and achieve large-scale production while ensuring the quality of nanosheets.While trying to exfoliate these ultra-thin nanosheets,some reseracher also tried to integrate these nanosheets into a new type of two-dimensional artificial heterojunction or superstructure.Generally,the two-dimensional superstructure is composed of different two-dimensional ultrathin nanosheets stacked alternately at the molecular level.Depending on the stack method,a superstructure stacked in the same order can exhibit different properties due to its unique internal structure.In particular,when the TiO₂/C superstructure is applied to the anode electrode material of a lithium ion battery,due to the influence of the pseudocapacitance effect on the interface of TiO₂/C,how to regularly arrange the two-phase substances of this superstructure to obtain a larger area the two-phase interface is critical.In this paper,we have improved the procedure of the nanosheet prepared by the exfoliating method.Besides,we also propose a strategy to introduce the assembled benzidine molecules as pillars and construct the TiO₂ nanosheets into a two-dimensional layered pillar-layer structure.Thus,the C/TiO₂ nanosheet composites with a periodic interval of 1.1 nm can be obtained via polymerization and carbonization.Firstly,we have successfully achieved the aim of preparing a large number of TiO₂nanosheets in a short period by improving the preparation process of osmotic swelling.Secondly,this method not only effectively alleviates the stress caused by chemical bond distortion in the carbonization process but also prevents the structure collapse of TiO₂through proper control of carbonization temperature.Finally,the C/TiO₂ nanosheet composites obtained by the above synthesis method have a large two-phase interface.This interface provides a lot of active sites for rapid pseudocapacitive lithium ion storage.Thus,the composites show an excellent rate performance with 67.8 m Ah/g at 12.8 A/g and great cycle stability with 87.4%capacity after 3000 cycles.