ZnF2-enabled preparation of Ti3C2Tx towards high-performance zinc-ion hybrid capacitors

Abstract

MXenes have become a popular research topic, owing to their two-dimensional structure and superior properties. To promote practical applications of MXenes, there is an urgent need for a facile and cost-effective synthesis method. In this work, a low-cost alternative to conventionally used LiF, namely ZnF2, is employed to prepare Ti3C2Tx. And organic intercalants are not required during the delamination of as-produced multilamellar Ti3C2Tx. In addition, such ZnF2-involved etching method demonstrates similar yield and quality of Ti3C2Tx compared to the LiF/HCl etching method. The Ti3C2Tx prepared by ZnF2 etchant is combined with nanocellulose to form self-supporting composite films, which are explored as the cathodes for rechargeable zinc-ion hybrid capacitors (ZHCs). Thanks to the synergistic effect of Ti3C2Tx and nanocellulose, the optimized composite film exhibits high tensile strength of 59.7 MPa, large electrical conductivity of 24,754 S m−1, good electrolyte wettability, and superior electrochemical performances for ZHCs, such as large specific capacitance of 250.6F g−1 at 0.5 A g−1 and large capacity retention of 83.2% after 20,000 cycles. Moreover, the assembled quasi-solid-state ZHC displays satisfactory specific capacity and good endurance to deformations. This work unveils new insights into MXene synthesis and highlights their potential for high-performance energy storage devices.