The Prepatation And Capacitive Performances Of Flexible MXene Based Film Electrodes

Supercapacitors are new energy storage devices with excellent power density and cycle stability,combining the advantages of traditional capacitors and batteries.With the rapid development of portable and wearable electronic devices,micro supercapacitors have received increasing attention,for which volume energy density is a very important performance.However,many electrode materials cannot achieve ideal energy densities due to lowe conductivity or lowe density.A new kind of two-dimensional transition metal carbides and nitrdes?MXene?have great application prospects in the fields of energy storage devices used in portable and wearable electronic for its excellent theoretical specific capacitance,conductivity and mechanical properties.However,similar to other two-dimensional materials,the self-restacking caused by strong van der Waals interactions between the layers leads to insufficient access to allow the electrolyte ions to contact the active material,resulting in sluggish electrode kinetics and poor rate performance.In terms of this issue,the MXene/AQ-CNT composite membrane electrode was fabricated by intercalating MXene with 1,5-dihydroxyanthraquinone-functionalized carbon nanotubes?AQ-CNT?.The introduced AQ-CNT can not only effectively alleviate the self-restacking but also bring about extra pseudocapacitance thus a improved specific capacitance of the film electrode could be achieved.By optimizing the added amount of AQ-CNT,we can know that the film electrode with2 mg of AQ-CNT has the most excellent capacitance performance.At the current density of 1 A g^-1,the specific capacitance of MXene/AQ-CNT is 337.8 F g^-1,which is about 10%higher than that of pure MXene.Furthermore,the addition of AQ-CNT can significantly improve the hydrophilicity and tensile strength of film electrode,whose initial contact angle with water was shifted from 43.6^o to 18.9^o and tensile stress was also increased by almost three times.In addition,compared with pure MXene film electrode,MXene/AQ-CNT exhibit more excellent capacitance and rate performances as the thickness of film increases.indicating that AQ-CNT can effectively improve the electrochemiacal performance.In order to further develop the capacitance performance of MXene,the f-MXene film electrode was prepared by freeze-drying method without the aid of other spacers.During the process of freeze-drying,moisture between MXene layers was removed through sublimation in the state of ice,so that the original structure between the MXene sheets can be maintained as much as possible.The specific capacitance of f-MXene film electrode is 341 F g^-1 at the current density of 1 A g^-1,and when the current density increased to 10 A g^-1,the specific capacitance of 206.2F g^-1 can still be achieved,indicating its excellent rate performance.Compared with the film electrodes of different thickness,it was found that the freeze-drying could still effectively improve the capacitive properties of MXene.