Simplified Synthesis of Fluoride-Free Ti3C2Tx via Electrochemical Etching toward High- Performance Electrochemical Capacitors

MXenes have been intensively studied for electrochemical energy storage and other applications. However, time-consuming multistep procedures involving hypertoxic HF or alike are utilized in conventional synthesis methods of MXenes. Besides, -F terminal functional groups inevitably exist in these MXenes, detrimental to supercapacitor and battery performances. Herein, we develop a facile and time-saving electrochemical etching method to synthesize F-free and Cl-containing Ti3C2Tx in a mixed LiOH and LiCl aqueous solution with an etching efficiency of 92.2%. During the synthesis, sonification alone is able to delaminate Ti3C2Tx without using any hazardous organic intercalant. The obtained delaminated Ti3C2Tx flakes are similar to 3.8 mu m in lateral size and similar to 3.9 nm in thickness, and can be stable in an aqueous dispersion for at least 15 days. The filtrated Ti(3)C(2)T(x )film is 20.5 MPa in tensile strength, 13.4 GPa in Young's modulus, and 1663 S cm(-1) in electrical conductivity, and exhibits specific capacitances of 323.7 F g(-1), 1.39 F cm(-2), and 1160 F cm(-3) for supercapacitors. Also, a flexible zinc-ion hybrid capacitor with energy density values of 20.8 mWh cm(-3) and 249.9 mu Wh cm(-2) is assembled by using the Ti3C2Tx film as the cathode, and can maintain almost all its capacity under bending.

Automated summary

A facile and time-saving electrochemical etching method is developed to synthesize F-free and Cl-containing Ti3C2Tx. Sonification alone is able to delaminate Ti3C2Tx without using any hazardous organic intercalant. The obtained Ti3C2Tx flakes exhibit suitable size and stability, and show excellent performance in supercapacitors and hybrid capacitors.