Enhancement of high rate performance and diffusion properties for Li4Ti5O12 anode materials by carbon additive

摘要

We prepared pristine Li4Ti5O12 (P-LTO) using a combustion method. Carbon additive Li4Ti5O12 (C-LTO) were prepared by using L-ascorbic acid at 500 degrees C for 2 h. The diffraction peaks of XRD can be indexed to the cubic spinel structure of LTO with space group Fd-3m. When the carbon was added, there was no change in the diffraction data. The P-LTO morphology is flaky and highly porous. The bulk sizes of the P-LTO vary between a few nanometres to a few micrometres. The discharge capacities at 1 C (160 mA g(-1)) of the P-LTO and C-LTO-1, C-LTO-2 are 161, 160 and 157 mAh g(-1) respectively. The small amount of carbon additive solution can improve the discharge capacities in the high current range. The C-LTO-1 has a more stable voltage plateau and better rate performance at high current densities compared to the P-LTO and C-LTO-2. This means that a small amount of carbon solution additive can enhance the surface conductivity and reduce the interface resistance, which directly led to improved high rate capabilities and cycle performance. In particular, the discharge capacity decrease of the P-LTO in the early stage is higher than that of the C-LTO. The CV of the P-LTO and C-LTO-1 was carried out at different scan rates in the range of 0.2-1 mV s(-1) within a potential window of 1.0-2.6 V (versus Li/Li+). The diffusion coefficient of C-LTO is higher than that of P-LTO. The addition of carbon can effectively improve the electrochemical reaction kinetics of Li+ intercalation/deintercalation. These CV results are also evidence for the good high rate capability of C-LTO.