An investigation of Cu‐ZrO 2 ‐TiO 2 / CNTs anode material for lithium‐ion batteries

Abstract

Material Cu-ZrO2-TiO2/CNTs was prepared through the thermal decomposition of metal organic polymer/carbon nanotubes (CNTs) composite [CuxZrmTil(OCH2CH2O)2(m + l) + x]n/CNTs, which was 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. Higher specific capacity and higher rate capability (351 mAh g−1 at 100 mA g−1, 196 mAh g−1 at 2000 mA g−1) were 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 were created in the metal oxide phase and at the same time, part of Ti4+ and Cu2+ cations were 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. 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 render a highly efficient anode material for Li+ batteries. A 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.