3D carbon-coated MXene architectures with high and ultrafast lithium/sodium-ion storage --- Energy Storage Materials, 2020, 2020, 29,163-171

Peng Zhang, Razium Ali Soomro, Zhaoruxin Guan, Ning Sun, Bin Xu*.

       MXenes have recently emerged as a promising candidate for energy storage devices due to their high volumetric capacitance and robust energy profile. However, MXenes are prone to surface oxidation and layer re-stacking, which compromise their practical applications in energy storage. Here, we propose a simple approach to directly transform 2D T₃C₂T_x MXene nanosheets into 3D carbon-coated T₃C₂T_x architecture. The nanohybrid was synthesized by achieving self-polymerization of dopamine over the surface of pristine T₃C₂T_x nanosheets followed by freeze-drying and carbonization under an inert air atmosphere. The self-polymerization of dopamine not only facilitated the transformation of 2D T₃C₂T_x sheets into 3D tremella-like architecture, but its subsequent carbonization resulted in complete coverage of a thin carbon coating that preserves the structure from both airoxidation and structural aggregation. The 3D tremella-like architecture (T-MXene@C) with active and stable surface-facets facilitated fast charge transportation, ultrahigh capacity, superior rate performance, and long cyclability when being used as anode material for lithium-ion batteries (LIBs) and sodium-ion batteries (SIBs). In the case of LIBs, the T-MXene@C exhibited a high capacity of 499.4 mA h g^-1 at 0.2 C and 101.5 mA h g^-1 at 100 C. Whereas, a high capacity of 257.6 mA h g^-1 at 0.05 A g^-1 after 200 cycles and 77.8 mA h g^-1 at 10 A g^-1 were obtained for SIBs, respectively. In addition, long cycle durability with a capacity retention of 91.7% at 1 A g^-1 after 3000 cycles with a 0.00277% decay per cycle was achieved, endowing T-MXene@C capability to serve as a prospective hybrid for the energy applications.