Ni foam supported quasi-core-shell structure of ultrathin Ti₃C₂ nanosheets through electrostatic layer-by-layer self-assembly as high rate-performance electrodes of supercapacitors

Supercapacitor, as an important energy storage device, is a critical component for next generation electric power system, due to its high power density and long cycle life. In this study, a novel electrode material with quasi-core-shell structure, consisting of negatively charged few layer Ti₃C₂ nanosheets (FL-Ti₃C₂) and positively charged polyethyleneimine as building blocks, has been prepared by using an electrostatic layer-by-layer self-assembly method, with highly conductive Ni foam to be used as the skeleton. The unique quasi-core-shell structured ultrathin Ti₃C₂ nanosheets provide an excellent electron channel, ion transport channel and large effective contact area, thus leading to a great improvement in electrochemical performance of the material. The specific capacitance of the binder-free FL-Ti₃C₂@Ni foam electrodes reaches 370 F g⁻¹ at the scan rate of 2 mV s⁻¹ and a specific capacitance of 117 F g⁻¹ is obtained even at the scan rate of 1000 mV s⁻¹ in the electrolyte of Li₂SO₄, indicating a high rate performance. In addition, this electrode shows a long-term cyclic stability with a loss of only 13.7% after 10,000 circles. Furthermore, quantitative analysis has been conducted to ensure the relationship between the capacitive contribution and the rate performance of the as-fabricated electrode.