Advanced electrochemical properties of Mo-doped Li4Ti5O12 anode material for power lithium ion battery

Abstract

Mo⁶⁺-doped Li₄Ti_5−xMo_xO₁₂ (0 ≤ x ≤ 0.2) samples have been synthesized via a simple solid-state reaction. The products were characterized by X-ray diffraction (XRD), Raman spectroscopy (RS), scanning electronic microscope (SEM), cyclic voltammetry (CV), electrochemical impedance spectroscopy (EIS), and galvanostatic charge-discharge testing. Li₄Ti_5−xMo_xO₁₂ (x = 0, 0.05) shows the pure phase structure, but several impurity peak can be detected when x ≥ 0.1. Mo-doping did not change the electrochemical reaction process and basic spinel structure of Li₄Ti₅O₁₂. The particle size of the Li₄Ti_5−xMo_xO₁₂ (0≤ x ≤ 0.2) sample was about 2–3 μm and Li₄Ti₅O₁₂ has less agglomeration. Electrochemical results show that the Mo⁶⁺-doped Li₄Ti₅O₁₂ samples display a larger diffusion coefficient of lithium ions, lower charge transfer resistance, higher rate capability and excellent reversibility. The Li₄Ti_5−xMo_xO₁₂ (x = 0.1, 0.15) sample maintained considerable capacities until 6 C rates, whereas pristine Li₄Ti₅O₁₂ shows a severe capacity decline at high rates. After 100 cycles, the specific reversible capacities of Li₄Ti₅O₁₂ and Li₄Ti_4.9Mo_0.1O₁₂ are 195.8 and 210.8 mAh g⁻¹, respectively. The superior cycling performance and wide discharge voltage range, as well as simple synthesis route and low synthesis cost of the Mo-doped Li₄Ti₅O₁₂ are expected to show a potential commercial application.