Ultrahigh gravimetric and volumetric capacitance in Ti3C2Tx MXene negative electrode enabled by surface modification and in-situ intercalation

Two-dimensional titanium carbide (MXene) has attracted significant attentions in supercapacitors owing to its high metallic conductivity and excellent chemical properties. However, the inherent restacking issue and -F surface termination severely limit the energy storage. Here, an effective strategy to construct high-performance Ti3C2Tx MXene (A-Ti3C2Tx /PANI) based on the synergistic effect of modified surface termination, expanded interlayer spacing and three-dimensional structure is reported. Benefiting from the interconnected structure, enhanced electrochemical activity and efficient ion/electron transport layer, the prepared negative electrode demonstrates an outstanding specific capacitance of 652.3 F g(-1) at 1 A g(-1) (similar to 3 times of the pristine MXene), an impressive rate capability with 81% capacitance retention at 50 A g(-1), and excellent cycling stability with above 99% capacitance retention after 10, 000 cycles. In addition, a symmetric supercapacitor is fabricated using A-Ti3C2Tx/PANI, and it delivers a high energy density of 20.3 Wh kg(-1). Furthermore, the prepared free-stranding film electrode based on A-Ti3C2Tx /PANI shows a high volumetric capacitance of 2368 F cm(-3). The improved gravimetric and volumetric capacitances surpass almost all the reported MXene-based electrodes. This study demonstrates a new strategy to enhance the electrochemical performance of Ti3C2Tx electrode and could be a universal way applicable to other MXenes.

Automated summary

A high-performance Ti3C2Tx MXene based on modified surface termination, expanded interlayer spacing, and three-dimensional structure is successfully synthesized. The prepared negative electrode exhibits outstanding specific capacitance, rate capability, and cycling stability. Furthermore, a symmetric supercapacitor using the MXene material shows a high energy density. This study provides a new strategy for enhancing the electrochemical performance of MXene electrodes.