The Research Of Copper Sulphide And Its Composite As The Electrode Of Lithium-ion Battery

The increasingly emerging energy and environmental issues have constantly inspiredenormous amount of research interest in advanced energy conversion and storage (ECS)device. The performance of these devices depends intimately on the properties of theirmaterials.Due to the unique physical and chemical properties, copper sulfide is widely usedin energy storage and conversion, such as a lithium-ion battery, photocatalysis, supercapacitors, and so on.In this article, copper sulfide nanowire bundles (CuSNWs) are synthesized by atemplate-and surfactant-free method in a dimethylsulfoxide (DMSO)-ethyl glycol (EG)mixed solvent. It is noteworthy that the precursor plays a crucial role in the formation of thenanocomposites structure. XRD, Raman, SEM and TEM are used to investigate themorphology and structure of CuSnanowire bundles. The resulting CuS nanowire bundlesexhibit high capacity andgood cycle stabilityas acathode material for lithium-ion batteries.Itretains a high capacity of540mA h g-1after80cycles at0.1C. The good electrochemicalperformance is attributed to unique one-dimensional structure, which offers such as manyactive sites for electrode reactions, a fast way for both ion and electron transport in axialdirection, and a robust structure for durability.On the base of CuS nanowire bundles, Copper sulfide nanowires/reduced grapheneoxide (CuSNWs/rGO) nanocompsites are successfully synthesized via a facile one-potmethod by introducing graphene oxide to the mixed solvent. The results of XRD, Raman,FT-IR, SEM prove that the graphene oxide are reduced when the CuS nanowires areforming. The as-fabricated CuSNWs/rGO nanocompsites show remarkably improvedLi-storage performance, excellent cycling stability as well as high-rate capability comparedwith pristine CuS nanowires. It obtains a reversible capacity of620mA h g-1at0.5C(1C=560mA g-1) after100cycles and320mA h g-1at a high current rate of4C even after500cycles. The excellent lithium storage performance is ascribed to two main aspects. Onthe one hand, the as-formed CuSNWs/rGO nanocomposites can effectively accommodatelarge volume changes during the process of Li+inser or extract; on the other hand, rGOnanosheets supply a2D conducting network and trap the polysulfides generated during theconversion reaction of CuS. Besides, CuSNWs/rGO nanocomposites exhibit goodphotocatalytic activity for degrading methylene blue. Compared with CuS nanowires, the UV-vis spectra of CuSNWs/rGO occurs a certain degree of red shift, which is better for theactivity of optical excitation. When using CuSNWs/rGO as catalyst,94%methylene blue(MB) has been decomposed after30min. More importantly, the material also exhibits goodcatalytic performance in the absence of light. The reason leading to excellent photocatalyticactivity of nanocomposite is as follows:(1) The introduction of rGO increasing the surfacearea which is better for the absorbency to MB.(2) The super conductive ability of rGO canprolong the lifetime of photogenerated electron and hole pairs.