MXene-encapsulated titanium-niobium oxide microspheres for fast and stable lithium storage

To address the inherently poor electronic and ionic conductivity of titanium-niobium oxide materials and to improve their suitability for use at high current densities, we designed and synthesized Ti2Nb10O29 (TNO) microspheres with diameters of 1 to 3 μm by a simple solvothermal method. Then, MXene, a highly conductive two-dimensional material, was introduced and perfectly coated onto the microsphere surface by electrostatic forces and chemical bonding. The MXene nanosheets not only improve the overall conductivity but also protect the TNO microspheres and reduce the electrochemical polarization at high current densities. Thus, the composite anode electrode shows outstanding reversible specific capacity and stability at high currents and long cycles. Specifically, at 20 C, the initial reversible specific capacity of the TNO@MXene electrode was 200.3 mAh.g−1 with a coulomb efficiency of 94.4%. The reversible specific capacity remained at 131.2 mAh.g−1 even after 1400 cycles with an average capacity loss rate of only 0.02%. In addition, the outstanding pseudo-capacitance property of TNO@MXene ensures its fast charging and discharging capability and capacity at a high rate.