Preparation And Electrochemical Performance Of Lithium Cu-ZrO₂-TiO₂/CNTs Anode Materials

Material Cu-ZrO₂-TiO₂/CNTs is prepared through the thermal decomposition of metal organic polymer/CNTs composite [Cu_xZr_mTi_l（OCH₂C H₂O）_2（m+l）+x]_n/CNTs,which is synthesized through the polymerization of ethylene glycol with metal organic compounds titanium tetra-isopropanolate,zirconium tetra-n-butoxide,and copper acetylacetonate in the presence of CNTs.High specific capacity and high rate capability(351 mAh g-2 at 100 mA g^-1,196 mAh g^-1 at 2000 mA g^-1)are reached.The reasons for the excellent electrochemical performances of the material could be found from the following aspects.In the thermal decomposition process of the metal organic polymer,nano pores are created in the metal oxide phase and at the same time,part of Ti⁴⁺and Cu²⁺cations are reduced to Ti³⁺ions and metal Cu.The substitution of Ti⁴⁺ions by Ti³⁺ ions in TiO₂ phase could form oxygen vacancies in the bulk of the material.The nano pores and the oxygen vacancies in Cu-ZrO₂-TiO₂/CNTs could offer large number of diffusion channels for lithium ions and open up more Li+ion storage positions to receive Li+ions at high rate.The presences of the oxygen vacancies,the Ti³⁺ions,and the metal copper in the material could enhance the electric conductivity of the material.In addition,the metal oxide phase wraps the carbon nanotubes,which form a good three-dimensional conductive network inside the material.Meanwhile,the existence of carbon nanotubes effectively alleviates the agglomeration of metal oxides.The investigation results show that the presence of Zr⁴⁺ions in the material could stabilize the pore structure.The stable pore structure,the oxygen vacancies,and the good electric conductivity of the material rend it a highly efficient anode material for Li+batteries.Rate performance test:Under the current density of 0.1 A g^-1,0.2 A g^-1,0.4 A g^-1,0.6 A g^-1,0.8 A g^-1,1.0 A g^-1,2.0 A g^-1,the specific capacities are 351 mAh g^-1,298 mAh g^-1,281 mAh g^-1,259 mAh g^-1,245 mAh g^-1,230 mAh g^-1,and 196 mAh g^-1,respectively.When the current density of returned to 0.1 A g^-1,the specific capacity of the material returns to 314 mAh g^-1.After a series of high current density impact,the capacity still maintained very well.The material has good reversibilities.The cycling life-time test shows that the Cu-ZrO₂-TiO₂/CNTs anode material gives a specific capacity of 351 mA h g^-1 at 100 mA g^-1 and a capacity retention rate of 92%after 200 cycles of charge/discharge.