Cu_(2)Se@C thin film with three-dimensional braided structure as a cathode material for enhanced Cu^(2+) storage

In the face of multiple challenges brought by the changes of global climate and environment,developing clean energy and updating green energy storage equipment are important ways to achieve carbon peak and carbon neutrality.Aqueous batteries have become a research hotspot due to their advantages of using the multivalent charge carrier,high ionic conductivity,environmental friendliness and cost effectiveness.In this work,the Cu_(2)Se@C(Cu_(2)Se coated on carbon clothes)thin film with a three-dimensional braided structure is fabricated by a simple electrochemical deposition method for Cu^(2+)storage for the first time.Compared with the commercial Cu_(2)Se powder,the well-designed Cu_(2)Se@C film shows enhanced specific capacity(640 mAh/g at 0.5 A/g)and rate performance(542 mAh/g at 5 A/g)as well as superior cycling stability(82.7%capacity retention after 1000 cycles at 1 A/g).The Cu^(2+)storage mechanism of the Cu_(2)Se@C electrode is based on a reversible phase transition process of Cu_(2)Se←→Cu_(2-x)Se←→CuSe←→CuSe_(2).In kinetic characteristic analysis,the Cu_(2)Se@C electrode demonstrates faster Cu^(2+)diffusion in discharge process than charge process resulting from the phase transition and the variation of interplanar spacing.This work highlights a facile one-piece design strategy and opens a new gateway for the exploration of advanced aqueous energy storage systems.