Synthesis,Modification And Electrochemical Performance Of Li₄Ti₅O₁₂/TiO₂ Nanosheets As Anodes For Lithium-ion Batteries

Spinel Li₄Ti₅O₁₂（LTO）,as a promising anode material,has been widely studied due to its outstanding structural stability and remarkable safety for lithium-ion batteries（LIBs）.However,the poor electron conductivity and low lithium-ion diffusion coefficient seriously limit its rate capability for the application in power LIBs.Carbon-free TiO₂ as a fast Li insertion/extraction host with high theoretical capacity is expected to be a highly promising modifier for LTO.Nevertheless,the poor electron conductivity of LTO/TiO₂ composites still impedes the practical application for LIBs.In this work,the electrochemical performances of LTO/TiO₂ nanosheets（NSs）were promoted with dispersing the Ag quantum dots（QDs）on the surface and synthesizing nanosheet arrays（NSA）.Firstly,highly dispersed Ag QDs were integrated into 2-dimensionl（2D）LTO/TiO₂ NSs for the first time to overcome the poor electron conductivity.Herein,we demonstrate rationally designed Ag quantum dot modified LTO/TiO₂ nanosheets（Ag-LTO/TiO₂ NSs）synthesized via a facile hydrothermal process,highlighting simultaneously the promotion of electron conductivity and lithium-ion diffusion coefficient.Furthermore,the structure of nanosheets can provide sufficient active sites to boost the electrochemical reactions and significantly shorten the transport lengths of lithium ions and electrons.The newly prepared Ag-LTO/TiO₂ NSs demonstrated excellent electrochemical performances with an ultrahigh reversible capacity of 177 mA h g-1 at 0.5 C and a superior rate performance of more than 148 mA h g-1 at 30 C between 1.0 and 2.5 V as the anode for LIBs.These novel quantum dot modified 2-dimensional materials will pave the way to a new family of carbon-free anode materials in response to the increasing demands for high-power energy storage.Secondly,arrays with a three-dimensional architecture can effectively reduce the lithium-ion diffusion path and simultaneously improve electron transfer by offering a higher contact area between electrolytes and active materials,thus not only minimizing the electrode resistance but also enhancing the rate performance.Combined with the carbon-free TiO₂,we also reported a facile template-free hydrothermal process to synthesize well-aligned LTO/TiO₂ nanosheet arrays with only the deionized water as the solvent.Furthermore,the well-structured 3-dimensionl（3D）morphology of the prepared LTO/TiO₂ nanosheet arrays with different molar concentrations of LiOH·H2O was systemically studied.The optimized molar concentration of LiOH·H2O is 0.10mol/L.The obtained materials demonstrated greatly enhanced electrochemical performances when used as the anode for LIBs with an ultrahigh reversible capacity of nearly 193 mA h g-1 at 0.5 C and 148 mA h g-1 at 30 C between 1.0 and 2.5 V vs.Li+/Li.We claim that the advanced LTO/TiO₂ nanosheet arrays will hold great promise for next-generation power LIBs.