Energy storage mechanism of MXene-Based sodium/potassium titanate for high performance electrode

K+/Na+ ion electrochemical capacitors have been studied for energy storage because of their abundant resources and higher theoretical energy density. However, the origin of the storage mechanism and low structural stability still remain elusive due to the large radius of Na+ and K+. Thus, the novel of NaTiO2/Ti3C2 and KTiO2/Ti3C2 electrodes are prepared by a simple hydrothermal self-growth. As a comparison, the reversible capacity of the two electrodes reach 307.43 F g−1 and 261.3 F g−1 at 0.5 A g−1, respectively. Further tests show that their capacitance retention achieve 82.4% and 85.7% after 3000 cycles at 2.0 A g−1, respectively. The good energy storage performance is based on the interlayer structure of Ti3C2 MXene retained by the prepared NaTiO2/Ti3C2 and KTiO2/Ti3C2 anode. Furthermore, the excellent electrochemical performance is mainly attributable to the TiO2 nanoribbons generated in-situ not only extended the interlayer spacing, but accelerated the cation transmission between the communication layers. By building a conductive network between the layers, Na+/K+ and F− form a strong covalent bonds between the MXene layers, which provides additional pseudocapacitance properties. This work provides a new way for the preparation of high-performance Na+/K+ electrochemical capacitors.