Study On The Influence Of The Outer Diameter And Length Of Graphitized Multi-walled Carbon Nanotubes On The Electrochemical Performance Of Aluminum Ion Batteries

At present,In recent years,multivalent ion batteries have attracted much attention,with aluminum ion batteries as the representative.Aluminum resources are relatively abundant,and it is the most abundant metal in the earth’s crust(accounting for 7.73%).Aluminum is often used as a negative electrode in batteries and is a high-energy carrier.Its theoretical specific capacity reaches 2980mAhg-1,and the mining volume is more than 1000 times that of metal lithium.Its low price,safe and stable characteristics make it recyclable and have low environmental pollution,so metal aluminum is the most ideal Battery negative electrode material.The most studied of aluminum ion batteries is the cathode material,but in addition to the batteries with graphite and graphene as the cathode material have better electrochemical performance,other aluminum ion batteries show poor performance due to the volume expansion and structural decomposition of the cathode material The electrochemical performance limits the practicality and commercialization of aluminum ion batteries.When one-dimensional graphitized multi-wall carbon tubes are used as cathode materials,aluminum-carbon tube batteries exhibit excellent electrochemical performance.In this paper,four kinds of graphitized multi-wall carbon nanotubes(MWCNT)with different outer diameters and lengths are used as the positive electrode,aluminum metal is the negative electrode,and aluminum chloride/1-ethyl-3-methylimidazole chloride(AlCl3/[EMIm]Cl)Ionic liquids are used as electrolytes,glass fibers are used as separators to prepare different aluminum ion batteries,and the electrochemical performance of aluminum ion batteries is studied in detail.The main research contents are as follows:(1)The positive electrode materials were characterized by scanning electron microscopy,transmission electron microscopy,X-ray diffraction spectroscopy,Raman spectroscopy,etc.,and the material composition and phase morphology of the materials with different sizes were analyzed.And the difference between the crystal structure and the like,the four MWCNTs all show a clear hollow tubular structure and a good graphite structure.(2)The electrochemical performance of aluminum ion batteries was compared and studied by charge and discharge test,impedance test,rate performance test and cyclic voltammetry test.Various batteries exhibit different electrochemical performance,and the results show that the outer diameter is small Graphitized multi-walled carbon nanotubes with a large length exhibit the highest specific capacity when used as a cathode material,that is,graphitized multi-walled carbon nanotubes with a high aspect ratio exhibit the highest specific capacity.(3)Through the processing of cyclic voltammetry data,the results show that the electrochemical process of the MWCNT positive electrode with high aspect ratio of aluminum ions is mainly determined by the insertion/deintercalation(battery)behavior rather than the adsorption/desorption(capacitor)behavior.Together with the material characterization and electrochemical performance of the MWCNT positive electrode,it was confirmed that the primary and secondary routes of AlCl4-embedded or adsorbed on the MWCNT are the defective basal plane and the edge planes at both ends.