Morphology control and its effect on the electrochemical performance of Na2Li2Ti6O14 anode materials for lithium ion battery application

Na2Li2Ti6O14 was successfully prepared by a solvothermal method. The XRD patterns show that the as-prepared samples have good purity and crystallinity. Further Rietveld refinement and theoretical calculation suggested that lithium should occupy 16n and 8e sites of the lattice during the intercalation process, and nearly six lithiums can be inserted reversibly into the lattice. The amount of ammonium hydrogen carbonate added during the reactions have significant impacts on the structures and morphologies of the materials, and well-defined hierarchical and porous spheres can be obtained at a suitable condition. The electrochemical tests showed that the charge/discharge specific capacities of the four samples under a current density of 50 mA g-1 after 50 cycles are 103.9/104.3, 175.1/177.1, 191.9/194.1, and 138.4/140.4 mA h g(-1), suggesting that the performance of the NLTO-L-3 is much better than other samples. Furthermore, NLTO-L-3 also exhibits good cycling stability and rate capability, and its revisable capacity is about 93 mA h g(-1) at 2.8 A g(-1) after 500 cycles. The excellent performance can be attributed to the hierarchical structures and porous characteristics. These features are helpful for reducing the impedance and for improving the diffusion dynamics of materials, as further confirmed by EIS measurement. (c) 2017 Elsevier Ltd. All rights reserved.