A high-voltage and high-capacity Ti₃C₂T_x/BiCuS_2.5 heterostructure to boost up the energy density and recyclability of zinc-ion-hybrid capacitors

In this paper, a brand-new amorphous Ti₃C₂T_x/BiCuS_2.5 electrode material was first invented by a facile in-situ deposition strategy, whose workable voltage window was enlarged up to 2.0 V (−1.4 V~0.6 V) with an improved capacity to 840 C g⁻¹ at 1 A g⁻¹ due to a “baton relay” mechanism. When the Ti₃C₂T_x/BiCuS_2.5 electrode material was assembled for an aqueous symmetrical supercapacitor, the device exhibited a maximum energy density of 56.1 Wh kg⁻¹ at a power density of 15.3 kW kg⁻¹. After 10,000 cycles, the energy density was even elevated to 63.325 Wh kg⁻¹. When the Ti₃C₂T_x/BiCuS_2.5 material was used for a zinc-ion capacitor cathode, the device exhibited an energy density of 298.4 Wh kg⁻¹ at a power density of 7200 W kg⁻¹. The energy density retention of 95% after 7000 cycles and 82% after 10000 cycles clearly proved the good recyclability of Ti₃C₂T_x/BiCuS_2.5 electrode. Based on the attentive DFT simulation and XPS analysis, the energy storage mechanism was ascribed to the co-existence of intercalation and redox battery-type capacity. This work opens a new direction with new electrode materials workable at a high voltage range for the construction of high specific energy supercapacitors.