Preparation And Electrochemical Performance Of Silver Nanowires-Silicon Carbon Composite Anode Materials

Silicon-based materials are considered to be one of the most promising anode materials for lithium-ion batteries due to their high theoretical specific capacity,low self-discharge efficiency,environmental friendliness,and abundant natural reserves.Therefore,after further exploration,it has been found that compounding silicon carbon as a anode electrode material for lithium batteries can relieve the volume expansion of silicon to a certain extent and ensure the carbon content in the composite material,so that the anode electrode of lithium batteries has better electrochemical performance.Based on the silver nanowires?AgNWs?,silver nanowires-silicon-carbon?AgNWs@Si@C?composite lithium ion battery anode materials with different structures were prepared by the methods of ethyl orthosilicate hydrolysis-magnesium thermal reduction and carbon layer coating.The microstructure,electrochemical properties and energy storage properties of AgNWs@SiO₂,AgNWs@Si,AgNWs@Si@C and AgNWs@Si@GO composite anode materials as well as silicon content,carbon source content and preparation temperature some process parameters affect the law and mechanism of the composite anode materials electrochemistry.Such a preparation method is not only simple and safe to operate,but also has a high specific capacity of the prepared composite material.Silver nanowires with better long diameter were prepared by polyol method.Using ethylene glycol as the reducing agent,silver nanowires with a length of 20?m,a diameter of 50 nm,and an aspect ratio of more than 400 was synthesized by controlling the temperature,the content of different molecular weight PVP,the concentration of FeCl₃·6H₂O,and the content of other salt solutions.Experiments show that when the preparation temperature is 160?,the concentration of FeCl₃·6H₂O is 0.225 mM,and the mass ratio of PVP-1300000:PVP-K-30 is 2:1,the synthesized silver nanowires have a uniform morphology and an aspect ratio greater than 700.The silver nanowires were coated with TEOS.The thickness of the silica coating layer is adjusted by controlling the amount of TEOS.The results show that when the stirring time is 24 h,the volume of ammonia is 4 mL,and the amount of TEOS is 20?L,it can be obtained that contains only a small amount of self-generated silica balls and the specific capacity is finally stabilized at about 130 mAh/g after a long cycle about AgNWs@SiO₂ composite material.The magnesium oxide reduction method is used to directly reduce the silicon dioxide layer on the surface of the AgNWs@SiO₂ composite material to silicon to prepare AgNWs@Si.The results show that the cycle electrochemical performance of the prepared AgNWs@Si composite material is relatively good when the magnesium thermal reduction and the temperature in the intermediate temperature furnace are650?.The composite material was charged and discharged at 0.1 C,the specific discharge capacity was about 681.8 mAh/g for the first time.After 50 Coulomb cycles,the capacity retention rate was 20%.The AgNWs@Si composite material was reacted with graphene oxide and dopamine by a one-pot method to obtain AgNWs@Si@C type composite material.The addition of carbon layer improved the cyclic electrochemical performance of the composite material to a certain extent.The results show that when the reaction mass ratio of AgNWs@Si to graphene oxide is 1:1,the first cycle electrochemical performance of AgNWs@Si@GO is the better,and the charge and discharge are performed at a current density of 0.2 C.The first coulomb efficiency is about 95.4%,the specific capacity of the first discharge is 1384.8 mAh/g,and the capacity retention rate is about 72%after 60 cycles.The AgNWs@Si@C composite material obtained by dopamine coating had a specific discharge capacity of 1138.4 mAh/g for the first time,a specific capacity of 1027.9 mAh/g after 60 cycles,and a capacity retention rate of 90%.