The Effects of Fluorine Doping on the Structure, Interface and Electrochemical Properties of Lithium Titanate

Enhancing the electronic and ionic conductivity of Li4Ti5O12 electrode materials, as well as suppressing the interface reaction between Ti4+ on the surface of Li4Ti5O12 and the electrolyte, is one of the key factors in preparing high-power and long-life Li4Ti5O12 lithium-ion batteries. To tackle these challenges, fluorine ions with strong electronegativity was chosen as dopants to engineer fluorine-doped Li4Ti5O12 electrode materials. Fluorine ion doping changes the surface state of Li4Ti5O12, increases the interface compatibility, suppresses the reactivity between Li4Ti5O12 and the electrolyte, and forms a uniform SEI film during cycling. Moreover, fluorine ion doping induces the generation of oxygen vacancies and improves the crystallinity of Li4Ti5O12, thereby fostering improved electronic and ionic transport kinetics. The above appealing features enables the prepared fluorine-doped Li4Ti5O12 material demonstrates exceptional high-rate performance, delivering specific capacities of 175 mAh·g-1/0.5C, 159 mAh·g-1/10C, and 138 mAh·g-1/50C. In essence, the fluoride ion doping strategy holds profound implications for enhancing electrode interface characteristics, transport kinetics, and the fabrication of high-power lithium-ion batteries.