Sandwich-like Na₂Ti₃O₇ Nanosheet/Ti₃C₂ MXene Composite for High-Performance\nLithium/Sodium-Ion Batteries

Abstract

MXenes have shown great promise in high-efficiency energy\nstorage\non account of superior electrical conductivity and outstanding mechanical\nproperties. However, the practical applications of MXenes in electrochemical\nenergy storage are limited by layer restacking and surface oxidation\nissues. Herein, a unique sandwich-like Na₂Ti₃O₇ nanosheet/Ti₃C₂ MXene composite\n(NTO@MXene) with an expanded interlayer spacing of MXene has been\nfabricated by one-step simultaneous alkalization and oxidation. The\nNTO@MXene with a unique structure shortens the ion diffusion distance\nand promotes electrolyte infiltration, which is favorable for high-performance\nrechargeable batteries. As a result, the NTO@MXene composite as an\nanode electrode for lithium-ion batteries delivered exceptional rate\nperformance (159 mAh g^–1 at 4 A g^–1) and long-life cycling performance (capacity retention of nearly\n100% at 4 A g^–1 after 1200 cycles). When used as\na sodium-ion battery anode, the electrode also achieved an extraordinary\ncapacity of 103 mAh g^–1 at 0.1 A g^–1 and an exceptional capacity retention of 70% at a high current density\nof 2 A g^–1 after 3000 cycles.