Study On The Modification And Performance Of Mxene For The Cathode Material Of Rechargeable Aluminum-ion Batteries

As the most optimal candidate for a next-generation of large-scale grid energy storage equipment,aluminum-ion batteries have the characteristics of low cost,abundant resources,and high theoretical capacity.For now,the research on aluminum-ion batteries is still in its infancy and cannot meet the criteria of large-scale energy storage,especially in terms of cathode materials.The Ti₃C₂T_x material,which has been studied in two-dimensional MXene,can be used as a base material to composite with other electrochemically active materials due to its good electrical conductivity,hydrophilicity,and mechanical properties,in order to solve the shortcomings of insufficient performance of a single material.In the present work,Ti₃C₂T_x material is used to modify the cathode material of aluminum-ion battery and explore its electrochemical performance in aluminum-ion battery.Firstly,a simple hydrothermal method is used to"anchor"CoS₂ on the Ti₃C₂T_xlayer to prepare a CoS₂@MXene composite with good crystallinity.After the material is modified by MXene,as compared with pure CoS₂ particles,the particles are significantly refined and the specific surface area is increased.When CoS₂@MXene composite material is used as a cathode material for aluminum-ion batteries,the maximum discharge specific capacity is?175 m Ah/g at a current density of 100 m A/g,and the capacity decreases by about 11%,which is half of that of CoS₂ battery.MXene in the composite material serves as a conductive substrate,providing abundant active sites,shortening the ion/electron migration path,and obtaining excellent electrochemical performance.Secondly,the above-mentioned CoS₂@MXene composite material is prepared by adding carbon nanotubes to prepare an adhesive-free self-supporting electrode with good mechanical properties and flexibility.Compared with CoS₂/CNT,CoS₂@MXene/CNT battery has a higher specific discharge capacity of?185 m Ah/g and the capacity remains at about 90 m Ah/g after 500 cycles.The preparation of the flexible electrode does not require adhesives and conductive carbon,which reduces the use of inactive materials and reduces the cost of the battery.As compared with the traditional preparation,the binder-free battery improves the cycle life and coulomb efficiency of the battery.The addition of MXene improves the conductivity and the combination of CoS₂ and carbon nanotubes,thereby improving battery capacity and cycle performance.Finally,by controlling the reaction time and the molar ratio of aniline monomer and ammonium persulfate,three polyanilines with different morphologies,PANI-1,PANI-2 and PANI-3,were prepared.Through a simple comparison of the discharge specific capacity,it is found that the elongated PANI-3 shows better performance.PANI-3/MXene and PANI-3/MXene'were prepared by in-situ polymerization and mechanical mixing methods,and their electrochemical performance in aluminum ion batteries was tested.The specific discharge capacity of the PANI-3/MXene battery is about 105 m Ah/g,and the capacity retention rate of the battery after 800 cycles is higher than that of the PANI-3/MXene'.In the in-situ polymerized PANI-3/MXene composite,good binding force between MXene and PANI-3 and the good electronic conduction of MXene gives the composite more excellent electrochemical performance.In a word,the high conductivity and excellent mechanical properties of Ti₃C₂T_xMXene material have great potential in the modification of cathode materials in aluminum-ion battery.CoS₂@MXene composite materials,CoS₂@MXene/CNT flexible films and PANI-3/MXene composite materials all have pretty good electrochemical properties,and have potentia in the practical application of aluminum-ion batteries.