Heterointerface with Continuous Channels Enables Fast Na⁺ Transport in Layered Na₂Ti₃O₇.

Abstract

High-power sodium-ion batteries are essential for grid energy storage; however, they are generally limited by Na⁺ transport. Herein, we tailor a highly matched heterostructure (MgTi₃O₇@Na₂Ti₃O₇) via a facile in situ synthesis method. The similar crystal structures of Na₂Ti₃O₇ and MgTi₃O₇ creat continuous Na⁺ diffusion channels at the heterointerface, and the interactions at the interface creat a built-in interface electric field with a direction from MgTi₃O₇ to Na₂Ti₃O₇. As a result, the particular heterointerface enable rapid Na⁺ diffusion in the MgTi₃O₇@Na₂Ti₃O₇ electrode. The heterostructure engineering regulate the electrochemical reaction mechanism, leading to the solid solution reaction in the MgTi₃O₇@Na₂Ti₃O₇ electrode, facilitating rapid Na⁺ transport. Therefore, the MgTi₃O₇@Na₂Ti₃O₇ electrode exhibits an excellent rate capability (123 mAh/g at 20 C) and cycling performance. This work highlights the importance of a heterointerface with continuous channels in overcoming Na⁺ transport limitations in electrodes and could serves as a guide for designing a heterointerface for high-power sodium-ion batteries.