Preparation And Electrochemical Performance Of Silica-based Nanowire Arrays For Anode Materials Of Lithium Ion Batteries

Due to its low discharge potential and high theoretical specific capacity(1965 mAh g^-1),nano-silica?SiO₂?is one of the most abundant minerals on the planet,low in price and environmentally friendly.It is expected to be further commercialized as a lithium battery.Furthermore,during the initial lithiation of SiO₂,the formation of nano-Si and inert Li₄SiO₄ or Li₂O species helps to maintain the mechanical integrity of the electrode,thereby improving battery cycle performance.However,as a negative electrode material for lithium ion batteries,SiO₂ nanostructures are hindered by their inherent inconsistent conductivity and large volume change during repeated charge-discharge processes,resulting in low utilization of active materials and low structural stability.And low rate performance.In this paper,SiO₂ nanowire arrays and SiO₂@PEO composite nanoarrays were prepared by anodized aluminum oxide?AAO?template method.The morphology and structure of SiO₂-based nanowire arrays were characterized by field emission scanning electron microscopy?SEM?,transmission electron microscopy?TEM?,X-ray diffraction?XRD?,and Fourier transform infrared spectroscopy?FTIR?.Cyclic voltammetry?CV?,charge and discharge test,and electrochemical impedance spectroscopy?EIS?were used to study the electrochemical activity of SiO₂-based nanowire arrays as anode materials for lithium ion batteries.SiO₂ nanowire arrays were prepared by sol-gel method in the pores of AAO template.The results of SEM and TEM showed that the nanowires were about 100 nm in diameter and 30?m in length,and they grew evenly and densely.The nanowires prepared by ultrasonic assisted in the early stage of soaking and immersed for 24 hours at room temperature have the best morphology.XRD and FTIR confirmed that the prepared sample was amorphous SiO₂.Electrochemical tests show that the SiO₂ nanowire arrays have a first discharge specific capacity of 2252.6 mAh g^-1 and a Coulombic efficiency of60.7%at a current density of 200 mA g^-1.Even after about 400 cycles,the initial specific capacity of 97.5%was maintained.In addition,when the current density is increased to2500 mA g^-1,the high specific capacity of 315 mAh g^-1 can still be exhibited.Based on the amorphous SiO₂ nanowire arrays,an ultrathin polyoxyethylene PEO film-coated composite nanowire arrays SiO₂@PEO were prepared by simple infiltration method.The test results show that the composite nano-array SiO₂@PEO electrode exhibits a reversible capacity of 1225 mAh g^-1 after circulating about 200 cycles at a current density of 200 mA g^-1 compared with the amorphous SiO₂ nanowire arrays electrode.The Coulombic efficiency is maintained at 96%and the capacity is increased by 145%.In addition,the specific capacity of 360 mAh g^-1 is achieved at a high current density of 2500mA g^-1,which shows superior cycle and rate performance overall.This is due to the fact that the ultra-thin PEO cladding layer not only improves the electrical conductivity of the electrode material,but also has a better mitigation effect on the volume expansion of the electrode during charge and discharge,and the structural stability is enhanced.