Fe3+-stabilized Ti3C2Tx MXene enables ultrastable Li-ion storage at low temperature

Abstract It is highly important to develop ultrastable electrode materials for Li-ion batteries (LIBs), especially in the low temperature. Herein, we report Fe3+-stabilized Ti3C2Tx MXene (donated as T/F-4:1) as the anode material, which exhibits an ultrastable low-temperature Li-ion storage property (135.2 mA h g−1 after 300 cycles under the current density of 200 mA g−1 at −10 °C), compared with the negligible capacity for the pure Ti3C2Tx MXene (∼26 mA h g−1 at 200 mA g−1). We characterized as-made T/F samples via the X-ray photoelectron spectroscopy (XPS), Fourier transformed infrared (FT-IR) and Raman spectroscopy, and found that the terminated functional groups (-O and -OH) in T/F are Li+ storage sites. Fe3+-stabilization makes -O/-OH groups in MXene interlayers become active towards Li+, leading to much more active sites and thus an enhanced capacity and well cyclic stability. In contrast, only -O/-OH groups on the top and bottom surfaces of pure Ti3C2Tx MXene can be used to adsorb Li+, resulting in a low capacity. Transmission electron microscopy (TEM) and XPS data confirm that T/F-4:1 holds the highly stable solid electrolyte interphase (SEI) layer during the cycling at −10 °C. Density functional theory (DFT) calculations further uncover that T/F has fast diffusion of Li+ and consequent better electrochemical performances than pure Ti3C2Tx MXene. It is believed that the new strategy used here will help to fabricate advanced MXene-based electrode materials in the energy storage application.