Study On The Electrochemical Performance Of TiO₂/C Interface And N-doped TiO₂

As one of the energy storage devices,lithium-ion batteries?LIBs?are still concerned for its mature application.In the anode materials,Si anode has a high theoretical specific capacity,which is considered to be a promising anode material to replace the traditional carbon.The improvement of the performance of the Si anode has gone through the design process from nanosizing to composite and then to hierarchical composite structure.Although the electrochemical performance of the Si based anode has been significantly improved,its stability of performance and consistency are not good so that it not be widely used in commercial LIBs.The reason is that the basic properties of the hetero-interface in the composite structure of Si based anode are not very clear.Therefore,the research on the related hetero-interface in the Si based anode material is of great significance to improve and stabilize the Si based anode material.In this paper,the following research is carried out.1.Based on Si@C@TiO₂ coating structure,the TiO₂/C interface electrochemical performance was studied by using the multilayer structure model?amorphous TiO₂/C multilayer?.1)the amorphous TiO₂/C interface has strong lithium storage capacity.The kinetic analysis shows that the Li⁺concentration gradient at the local interface and between the interfaces can promote the transport of Li⁺.2)In the anatase TiO₂/C anode,the C layer doped TiO₂ with different concentration,and the best electrochemical performance could be obtained by the appropriate TiO₂/C thickness(the specific capacity of the sample with 10:5 thickness ratio was greatly improved(900.6 mAh g^-1),and the apparent diffusion coefficient of Li⁺was also the largest?0.131?).2.The experiment of homogeneous N-doped TiO₂ was designed to study the change of its electrochemical performance.The experimental results show that the specific capacity of N-doped amorphous TiO₂?TiON?is higher than that of amorphous TiO₂?a-TiO₂?,and its specific capacity is more than three times of that of anatase structure?c-TiO₂?,and more than two times of that of undoped anatase TiO₂?c-TiO₂?.N-doping can improve the initial coulomb efficiency of TiO₂?from less than50%to more than 80%?,and TiO₂ has better Li⁺diffusion coefficient.It is found that the excellent electrochemical performance of TiO₂ is the result of the synergistic effect of bulk electrochemical reaction and pseudocapacitance.3.Cu film is introduced into Si/C multilayer,due to the low diffusion barrier of Cu to Li⁺,the existence of Cu film enhances the diffusion of Li⁺and the conductivity of anode materials.At the same time,due to the good ductility of Cu film,it can promote the stability of the structure and the full performance of the material,and improve the specific capacity and rate performance of the anode material.