Electrochemical profile of lithium titanate/hard carbon composite as anode material for Li-ion batteries

In this study, we report a carbon-coated Li4Ti5O12/hard carbon composite as an anode for Li-ion batteries. The composite anode provides a clear edge in state-of-charge (SOC) estimation of Li-ion batteries and thus enables efficient energy management and health assessment. The shape of the charge/discharge curve for Li4Ti5O12 (LTO) is significantly modified by the addition of the hard carbon in an optimised amount to present a smoothly sloped voltage profile in the voltage window between 0.01 and 1.5 V. This voltage range is highly effective in avoiding overcharging of a type of Li-ion batteries, where cell voltages remain constant over a large SOC region. Compared with the pristine LTO anode charged/discharged between 3 and 0.01 V, the composite anode, in addition to showing an improved specific capacity and cycling stability, demonstrates a strong enhancement in the rate capability; at a rate as high as 20 C, a capacity of 160 mAh/g is still retained, which has been proven to arise from a dual improvement in the electronic conductivity by the hard carbon through mixing and the soft carbon via carbon coating. The advantages in SOC prediction and the excellent rate capability are expected to greatly promote its practical application.