Abstract:

In this work, we construct Na₂Li₂Ti₆O₁₄@LiAlO₂ (NLTO-L) composites by a simple ball milled process and post-calcination in air atmosphere to improve the electrochemical performance. The thickness of the LiAlO₂ coating layer is approximate 2 nm. The morphology and particle size of Na₂Li₂Ti₆O₁₄ are not dramatically altered after LiAlO₂ coating. All samples display similar particles with a size range from 150 to 500 nm. The LiAlO₂ coating can supply fast charge transmission paths with good insertion/extraction dynamics of lithium ions and provide an excellent rate performance and cycle performance of as-prepared Na₂Li₂Ti₆O₁₄@LiAlO₂ anodes. Therefore, LiAlO₂ coating efficiently enhances the rate performance and cycle performance of Na₂Li₂Ti₆O₁₄ anode, even at large current densities. As a result, Na₂Li₂Ti₆O₁₄@LiAlO₂ (5 wt%) reveals remarkable rate properties with reversible charge capacity of 238.7, 214.7, 185.8, 168.5 and 139.8 mAh g⁻¹ at 50, 100, 200, 300 and 500 mA g⁻¹, respectively. Na₂Li₂Ti₆O₁₄@LiAlO₂ (5 wt%) also possesses a good cycle performance with a de-lithiation capacity of 166.5 mAh g⁻¹ at 500 mA g⁻¹ after 200 cycles. Nonetheless, the corresponding de-lithiation capacity of pure Na₂Li₂Ti₆O₁₄ is only 140.1 mAh g⁻¹. Consequently, LiAlO₂ coating is an efficient approach to enhance the electrochemical performances of Na₂Li₂Ti₆O₁₄.

Key words: Li-ion batteries, Na₂Li₂Ti₆O₁₄, LiAlO₂, Anode material, Electrochemical properties