Study On Preparation Of Graphene Cathode Materials For Aluminum-ion Batteries

Aluminum-ion battery(AIB)is a novel electrochemical energy storage system with aluminum as anode and room temperature ionic liquid as electrolyte.Graphene is considered to be the most promising cathodic materials for aluminum-ion battery,which exhibits high specific capacity,long cycle life and outstanding rate performance.However,high cost and complexity of the current preparation process of high-quality graphene hinder its large-scale production and commercial applications.Therefore,it is necessary to explore a simple,green and low-cost method to prepare graphene used for cathodic material of AIBs.In this paper,we presented a facile electrochemical method for preparing exfoliated graphene(EE graphene)via one-step exfoliation in aqueous electrolytes.EE graphene paper was prepared by vacuum filtration of EE graphene suspension.The electrochemical performances of the graphene paper in the aluminum/graphene paper battery were investigated.The main conclusions were as follows:(1)Electrochemical exfoliation of graphite foil was carried out in nine electrolytes,respectively.The exfoliation can be successfully performed in Na2SO4,K2SO4,(NH4)2SO4 and H2SO4 solutions,respectively.Comparative analyses of XRD,Raman spectra,FT-IR,UV-vis indicated that the exfoliated product obtained in Na2SO4 solution possesses the least defects and the lowest oxidation degree.Only the product exfoliated from Na2SO4 solution can be stably dispersed in both N-methyl pyrrolidone and water media for more than 6 months.SEM and AFM analyses showed that the exfoliated product is graphene with 3-4 layers.(2)A novel approach to prepare graphene cathode materials for AIBs was established.Graphene dispersion is obtained by dispersing graphene into deionized water by ultrasonication;secondly,by vacuum filtration to obtain free-standing graphene paper(EE graphene paper)without binder;and then chemical reduction in HI acid and microwave reduction to prepare HI graphene paper and MW graphene paper cathodes,respectively.XRD,Raman spectra and XPS analyses showed that HI graphene paper has the lowest oxygen content.(3)In this paper,three kinds of graphene paper were used as the cathode to assemble aluminum-ion batteries.Al/HI graphene paper battery exhibits a high discharge specific capacity of 110 mAh g-1,and the capacity still maintains 92 mAh g-1 with a high coulomb efficiency of near 100%after 500 cycles.The battery has good rate performance and cycling stability.The charge/discharge mechanism is determined to be the intercalation/deintercalation process of AlCl4-in HI graphene paper cathode by XPS analysis.