Flexible Asymmetric Supercapacitors using Mildly Etched Ti₃C₂Tx MXene for Powering Wearable Devices

The work proposes a novel and fast method to synthesize Ti 3 C 2 T x MXene with enhanced redox activity and improved structural, optical, and electronic properties by incorporating NaOH in the late etching stage. The technique eliminates the need for postetching delamination while maintaining the properties of delaminated MXene. Optimizing the concentration of NaOH leads to the removal of the unetched MAX phase from MXene in the mild in situ HF etching technique. The obtained ultrapure MXene is used as the negative electrode in an asymmetric supercapacitor device configuration. The MXene//RuO 2 asymmetric device showed superior electrochemical performance with a specific capacitance of 73.3 F g − 1 , energy density of 23 Wh kg − 1 , and power density of 796 W kg −1 , with potential extendable up to 1.5 volts. The device retained more than 90% of its performance at the end of 2000 cycles. The all‐solid‐state asymmetric supercapacitor device fabricated using PVA/H 2 SO 4 gel polymer as the electrolyte, and Na‐MX and RuO 2 as the electrodes gave a specific capacitance of 845 mF g −1 , energy density of 470 mWh kg −1 , and power density of 5000 mW kg −1 at a current density of 5 mA g −1 with an extendable voltage window up to 2 V, more than twice the window obtained using symmetric supercapacitor with MXene as electrode.