Electrochemical Performance Of Si@void@C Anode Material For Lithium Ion Battery

The development of science and technology is changing with each passing day,and the speed of updating electronic devices is increasing.With the popularity and diversification of electronic devices,power consumption is increasing.Therefore,it is urgent to update the supporting energy storage equipment.Lithium-ion batteries have attracted much attention as high-energy density and low-cost energy storage devices.Unbalanced resources in areas such as hydropower and wind power require storage and transportation of large-capacity energy storage equipment.The development of portable electronic equipment requires batteries with higher energy density.Silicon-based materials stand out from a wide range of negative electrode materials with a theoretical specific capacity of 4200 mAh/g.Compared with the current anode materials on the market,the theoretical specific capacity of silicon is more than8 times higher.As a negative electrode material for lithium ion batteries,silicon-based materials can undergo redox reaction with lithium to form alloy-type products.The silicon atoms are connected to each other by covalent bonds,and the bulk of the material expands greatly with the intercalation of lithium ions.Volume expansion causes the material to pulverize and peel off from the substrate,which affects its stability.In addition,silicon is a semiconductor material with low intrinsic conductivity and low ion transport rate.In view of several problems faced by silicon-based materials,this paper uses structural modification to solve.This paper intends to introduce carbon materials as a buffer structure to alleviate volume changes.The carbon material can improve the overall conductivity of the material,provide a path for lithium ion transport,and the carbon material itself has a capacity to reduce the capacity reduction caused by the introduction of the buffer medium.Since C and Si are easy to form Si_xC at high temperature carbonization,resulting in capacity loss,Si and C are isolated by using a SiO₂ cladding layer.In this paper,tetraethylorthosilicate?TEOS?was used as the precursor of SiO₂,and then dopamine hydrochloride?DA?was coated on the surface.After high temperature carbonization,SiO₂ was etched away by HF acid,and the remaining sample was Si@void@C.First,the sample structure was characterized by means of material testing.XRD can analyze the sample phase composition;Raman spectroscopy to analyze the surface carbon shell morphology;TGA analysis material C element content;infrared analysis of sample chemical bond vibration;SEM observation sample surface morphology,test element content,element distribution;TEM observation material microstructure.Electrochemical tests have shown that this structure can effectively improve the cycle performance of the battery.The data show that at different current densities,the initial capacity of the material is much higher than the theoretical specific capacity of graphite;and the capacity keeps rising.At 500 mA/g current density,after 386 charge and discharge the capacity exceeds 550 mAh/g;at 200 mA/g current density,after 260 cycles,capacity reaches900 mAh/g,and still maintains an upward trend;At the 800 mA/g,1000 mA/g current density,after 500 cycles the reversible capacity still keeps rising.