Tent-pitching-inspired high-valence period 3-cation pre-intercalation excels for anode of 2D titanium carbide (MXene) with high Li storage capacity

Abstract

MXenes exhibit potentials as electrode materials for metal ion batteries because of high electronic conductivity. However, ionic conductivity of MXenes has set the bottleneck to meet high energy and powder density demand in energy storage. Even though significant progresses have been made for more delicate design of electrodes, it remains very challenging for how to enhance the ion transport capability with the aid of external electric field upon charging process. Herein, high-valence cation (i.e., Al3+ in Period 3) pre-intercalation was utilized to construct an expanded ion transfer channel, which allows for further broadening upon the charging process, in order to enhance the ionic conductivity. This approach was confirmed to effectively improve Li storage capacity and cyclic stability of 2D Ti3C2Tx MXene anode. Compared to low-valence cation Na+, high-valence Al3+ into MXenes layer affords a strong Coulombic interaction upon lithiation/charging process to sustain ion transport channels. Moreover, the common deformation of electrodes upon cycling was limited due to a lower Li diffusion barriers. These findings raise the prospects of an enhanced ion transport capability and reinvent our knowledge of high-valence cations incorporation into 2D and layered materials.