Effect of Surface Fluorination and Conductive Additives on the Charge/Discharge Characteristics of Lithium Titanate for Lithium Ion Battery

Abstract

Effect of surface fluorination and conductive additives on the charge/discharge behavior of lithium titanate (Li4/3Ti5/3O4) has been investigated using F2 gas and vapor grown carbon fiber (VGCF). Surface fluorination of Li4/3Ti5/3O4 was made using F2 gas (3x104 Pa) at 25-150℃ for 2 min. Charge capacities of Li4/3Ti5βO4 samples fluorinated at 70℃ and 100℃ were larger than those for original sample at high current densities of 300 and 600 mA/g. Optimum fluorination temperatures of Li4/3Ti5/3O4 were 70℃ and 100℃. Fibrous VGCF with a large surface area (17.7 m2/g) increased the utilization of available capacity of Li4/3Ti5/3O4 probably because it provided the better electrical contact than acetylene black (AB) between Li4/3Ti5/3O4 particles and nickel current collector.