Single-Layer Dititanium Oxide Ti<sub>2</sub>O MOene: Multifunctional Promises for Electride, Anode Materials, and Superconductor
Yan Luo, Tao Bo, Bao‐Tian Wang, Sergei Tretiak, Liujiang Zhou
Abstract
Using the first-principles calculations, we report the existence of the single-layer (SL) dititanium oxide Ti2O (labeled as MOene) that constructs a novel family of MXene based on transition-metal oxides. This MOene material strongly contrasts the conventional ones consisting of transition-metal carbides and/or nitrides. SL Ti2O has high thermal and dynamical stabilities because of the strong Ti–O ionic bonding interactions. Moreover, this material is an intrinsic electride and exhibits extremely low diffusion barriers of ∼12.0 and 6.3 meV for Li and Na diffusion, respectively. When applied as anode materials in lithium-ion batteries and sodium-ion batteries, it possesses a high energy storage capacity (960.23 mAhg–1), surpassing the traditional MXenes-based anodes. The superb electrochemical performance stems from the existing anionic electron on Ti2O surface. Astonishingly, SL Ti2O is also determined to be a superconductor with a superconducting transition temperature (Tc) of ∼9.8 K, which originates from the soft-mode of the first acoustic phonon branch and enhanced electron–phonon coupling in the low-frequency region. Furthermore, this soft-mode behaves much softer upon applying a compressive strain of 2%, leading to a higher Tc of 11.9 K. Our finding broadens the family of MXenes and could facilitate more experimental efforts toward future nanodevices.