Role of calcination atmosphere in vanadium doped Li₄Ti₅O₁₂ for lithium ion battery anode material

Highlights: • First comparison on V doped Li₄Ti₅O₁₂ (VLTO) synthesized in air and argon. • Ti⁴⁺ do not reduce to Ti³⁺ in air calcined VLTO. • V doping enhances reducing of Ti⁴⁺ to Ti³⁺ in argon calcined VLTO. • Li₄Ti_4.9V_0.1O₁₂ calcined in argon shows best charge-discharge behaviors. • Conductivity enhancement in argon calcined VLTO upto three orders. - Abstract: Li₄Ti₅O₁₂ (LTO) with enhanced properties can replace the conventional carbonaceous anode material of lithium ion battery. Vanadium doped LTO (Li₄Ti_5-xV_xO₁₂, x = 0, 0.05, 0.1, 0.15) materials are synthesized by sol-gel process followed by calcination of dried gel in air and argon atmosphere. No additional phase corresponding V is indicated in XRD patterns. Calcination in argon reduces the particle size of Li₄Ti_5-xV_xO₁₂ while V doping reduces particle size distribution. XPS reveals that Ti⁴⁺ get reduced to Ti³⁺ only in argon calcined Li₄Ti_5-xV_xO₁₂ which is enhanced by V doping. Electrochemical impedance spectroscopy confirms that compared to LTO, lithium ion diffusion coefficient of air and argon calcined Li₄Ti_4.85V_0.15O₁₂ is approximately two and three times higher. Argon calcined Li₄Ti_4.9V_0.1O₁₂ shows highest charge-discharge capacities at almost all C-rates (0.1 to 5C; 1C = 175mAg⁻¹). Electronic conductivity of argon calcined Li₄Ti_4.9V_0.1O₁₂ is 1.7 × 10⁻² S cm⁻¹ which is three orders higher than that of LTO.