Research On CuS And Cu₂S As Anode Materials For Lithium-ion Batteries

Owing to the merits of high energy density, high voltage output, long cycle life andenvironment friendly, lithium ion batteries have been widely used in electronic equipmentsand electric vehicles. Anode materials affect the electrochemical performance of lithium ionbatteries greatly. But the development of commercial anodes has been restrained by the lowtheoretical capacity and safety concerns. It is of great significance to develop anodematerials with excellent performance. Copper sulfides (CuxS, x=1,2) have attractedextensive attention due to natural abundance, high theoretical capacity and low cost,however, the poor cycleability limits the practical application as anode materials inlithium-ion batteries (LIBs). To solve these problems, CuS/MWCNTs composites andCu2S/C composites were synthesized respectively.Carbon nano tubes (CNTs) possess good electrical conductivity and structure stability.CNTs are introduced to active electrode materials to form conductive network, thus theconductivity can be effectively improved. The unique structure contributes to the storage andmove of Li+. Carbon coating is expected to be an effective strategy to improveelectrochemical performance. It is reported that carbon coating can alleviate the volumeexpansion, suppress the aggregation of active particles and increase the electronicconductivity of the electrodes. In this paper, the main research contents and results are asfollows:(1) CuS/MWCNTs composites were fabricated through hydrothermal method usingCu(NO3)2·3H2O and thiourea as raw materials. The SEM images show that the final productsare sphere morphology consisted of nanoplates. The diameter is around2-3μm. Altering theaddition of MWCNTs to obtain the composites with optimal electrochemical performance,and5%,10%,15%of MWCNTs were chose. The electrochemical tests indicate theCuS/MWCNTs-10%presents higher discharge capacity and better cycling performance thanpure CuS. The reversible capacity of the Cu2S/MWCNTs-10%composites is100.5mAh g-1after50circles at0.2C.(2) Cu2S/C composites as anode materials for LIBs were synthesized by a hydrothermalmethod and subsequent calcination at800°C for2h, and glucose was used as a carbonsource. The electrochemical performance of Cu2S/C composites was evaluated by cyclic voltammograms and galvanostatic discharge/charge testing. The Cu2S/C composites candeliver a discharge capacity of300mAh g-1after100cycles at a current density of100mAg-1; however, the discharge capacity of pure Cu2S is only30mAh g-1after100cycles.