Preparation And Electrochemical Performance Of Cu₂S Composite Electrode Materials Based On Cu₂O Template

The exploitation and utilization of renewable green energy have been deliberated in response to the consumption of fossil fuels and the deterioration of environmental pollution.As the renewable energy sources exhibit limitations in the process of transportation and supply,supercapacitors,which show unique benefits in charge capacity and operating life,are expected to be an important contributor to the transformation of the energy system.When optimizing the energy storage characteristics of supercapacitors,the selection and design of the electrode materials are the main entry points.In order to cope with the low conductivity and poor stability of copper sulfide in the practical energy storage,Cu₂S@C and Cu₂S@NC,were fabricated based on copper sulfide with different carbon sources.By adjusting the preparation conditions and making full use of the synergy between different components and the desig n of the hollow structure,the electrochemical performance of the materials have been optimized.On this basis,the results of characterization and electrochemical tests are integrated to systematically elucidate the morphological evolution of the composites,and to explore the energy storage mechanism of the el ectrodes made of the two composites in aqueous electrolyte,so that they can have a certain basis for application.The main research contents are as follows:（1）To cope with the current defect of poor stability when copper-based compounds are used as negative materials,an experimental method based on the dual design of material composition and structure was proposed to synthesize hollow-structured Cu₂S@C composites.The core-shell structure Cu₂O@Cu₂S with cubic Cu₂O as a template was used as the precursor,and the trimesic acid was used as the etching agent and ligand.Then the HKUST-1 was then grown in situ on Cu₂O@Cu₂S.After calcined carbonization and etching treatment,the composi te material with hollow cubic structure composed of carbon shell and Cu₂S was finally obtained.In this process,the optimal synthesis path was determined by systematically regulating the synthesis conditions such as the dosage of vulcanizing agent,water bath reaction time and calcination temperature.In accordance with the characterization and electrochemical test findings of the produced Cu₂S@C,the structural composition,synthesis process and energy storage mechanism of the prepared materials were also investigated in detail in this study.（2）In order to solve the problem of insufficient stability of copper sulfides for negative electrode applications,dopamine（DA）,which can achieve self-doping of nitrogen atoms,was selected as the carbon source to prepare Cu₂S@NC with graded hollow cubic structure,and eventually achieved the goal of performance optimization based on components and structure.Using the mechanism of oxidation self-polymerization reaction of DA under specific conditions,it is polymerized and coated on the Cu₂O template.After high temperature carbonization,vulcanization and etching treatment,nitrogen atom-doped Cu₂S@NC composites were prepared.In this process,the optimal synthesis route of the Cu₂S@NC composites was designed by regulating the experimental conditions such as the dopamine hydrochloride dosage,calcination conditions and vulcanizing agent dosage.At the same time,characterization and electrochemical evaluation of the fabricated materials were carried out,and on this basis,the composition,morphology and synthesis mechanism were analyzed.（3）The electrochemical properties of Cu₂S@C and Cu₂S@NC were tested to explore the relationship between the composition and structure of the materials and the electrochemical energy storage characteristics.In terms of composition,Cu₂S and the tightly wrapped carbon shell guarantee the electrochemical reactivity,energy storage kinetics and stability of the material.Besides,the structural hollow cube can effectively mitigate the effect of volume shrinkage and expansion on the overall morphological structure during repeated energy storage,and improve the stability of the materials.Specifically,the specific capacitance of Cu₂S@C and Cu₂S@NC electrode materials are much higher than that of conventional carbon-based materials at the current density of 1A·g^-1,which is 1261.3 F·g^-1 and 1257.5 F·g^-1,respectively.When the current density increases to 10 A·g^-1,Cu₂S@C and Cu₂S@NC composites still exhibited capacitance performance of 737.5 F·g^-1 and 685.0 F·g^-1,respectively.The initial specific capacitance of the above two composites maintained at 78.1%and 56.3%after 3000 cycles at a high current density(7 A·g^-1),which was obviously superior to that of the single Cu₂S（19.52%）.