Ultrathin atomic layer deposited ZrO2 coating to enhance the electrochemical performance of Li4Ti5O12 as an anode material

Atomic layer deposition (ALD) was used to deposit ZrO2 directly on Li4Ti5O12 electrode to improve its electrochemical performance. The thickness of the deposited ZrO2 was controlled by adjusting ALD cycles from 0 to 1, 2, 5, 10 and 50. The Li4Ti5O12 electrodes with and without ZrO2 coating were characterized by scanning electron microscope, energy dispersive X-ray spectroscopy, high-resolution transmission electron microscope, cyclic voltammetry (CV) and galvanostatic charge-discharge test. The CV result indicated that ZrO2 coating with 2, 5 and 10 ALD cycles could effectively reduce the electrochemical polarization of the Li4Ti5O12 electrode. Charge-discharge test revealed that the Li4Ti5O12 electrodes with 1-, 2- and 5-cycle ZrO2 coating exhibited higher specific capacity, better cycling performance and rate capability than the pristine Li4Ti5O12 in a voltage range of 0.1-2.5 V. However, ZrO2 coating with more than 5 ALD cycles could lead to degraded performance of Li4Ti5O12. Mechanism for the enhanced electrochemical performance of Li4Ti5O12 was explored by electrochemical impedance spectroscopy, and the reason was attributed to the suppressed formation of solid electrolyte interphase and the improved electron transport by ultrathin ZrO2 coating.