Effect of carbon coating toward cycling stability of Li4Ti5O12 anode material

Li4Ti5O12 has already become one of the most attractive anode materials for high power applications in Li-ion batteries (like electric vehicles (EV), hybrid vehicles (HEV) and plug-in hybrid vehicles (PHEV)), since it exhibits excellent Li+ insertion/extraction reversibility with zero structural change and a relatively high operating voltage (1.55 V vs. Li/Li+) to ensure excellent safety of the battery1. However, its power performance is greatly limited by its low electronic conductivity, which leads to a low specific capacity and poor capabilities at high rates2. To overcome this drawback, one effective way is to modify the Li4Ti5O12 surface with carbon coating in order to improve the electrochemical performances in terms of rate capability, lithium storage capacity and capacity retention3. In this work, we prepared and tested CMC-based Li4Ti5O12 (LTO) and Li4Ti5O12 carbon coated (LTOc.c) electrodes in order to investigate the effect of carbon coating both on electrochemical performances and on interfacial properties. The two materials have been tested by using charge/discharge cycles at several C-rates and impedance measurements. The results show that the cycling performances at room temperature of LTO and LTOc.c anodes are comparable, even if LTOc.c material delivers higher capacities at high C-rates than pristine one, confirming the beneficial effect of carbon coating toward rate capability and cycling stability. Furthermore, impedance measurements, carried out at both 25 °C and 50 °C, reveal that the carbon coating suppresses the rise of the cell impedance, especially for charge transfer resistance, at both temperatures. In addition, it improves the surface stability, promoting the good rate performances of LTO c.c.material.