The Study Of Lithium-ion Battery Silica Anode Materials

Lithium ion batteries?LIBs?havebeen widely applied to electric vehicles and energy storage systemsas promising energy sources for theirhigh energy density,high operating voltage,long cyclelife,lowself-discharge,excellent rate capability and no memory effect.Alternatively,silica?SiO₂?has become a promising electrode material for LIBs because ofthe lowoperates voltage,high theoretical capacity,environmental safety and low price.However,anunsatisfying electrochemical performance is presented because its dramatic volume variation duringthelithiation/delithiation process and the capacity decayingrapidlyA new routing is introduced that SiO₂ nanotubes was synthesizedfromhalloysite with a simple and green method.Then thesucrosewas used as the carbon precursor,calcining at 900°C in argon atmosphere for 3 hours to forming a carbon layer on the surface of the SiO2 nanotubes.In this way,the SiO2/C nanotubes composite could be synthesized successfully.In this paper,the morphology,structure and composition of synthesized materialswere characterized by X-ray diffraction?XRD?,scanning electron microscope?SEM?,transmission electron microscopy?TEM?,fourier transform infrared spectroscopy?FTIR?and thermogravimetry-diffenential thermal analysis?TG-DTA?.The reaction mechanismand electrochemical performance were analyzed by cyclic violtammetry?CV?,electrochemical impedance spectroscopy?EIS?and charge-discharge tests.The sucrose as a carbon sourcewas incorporated into SiO₂ and calcining at 900°C in argon atmosphere,thecomposite materialspecific irreversible capacity for the first time is911mAh/g,coulombic efficiency is 70.6%.Compared with SiO_2,the irreversiblecapacityat first cycle is150mAh/g.After carbon coating,the performance of the composite material has agreatimprovement.Aftersynthesize SiO₂/C composite material,graphene oxideis?GO?incorporate into SiO₂/C,calcining at 900°C in argon atmosphere for 3 hours.In this way,the silica/carbon/graphene?SiO₂/C/G?compositecould be synthesized successfully.The first cycle charge and discharge capacity of SiO₂/C/G is 841mAh/g,1341mAh/g.Then replace the graphene oxide withcarbon nanotubes?CNTs?.It delivers the initial specific capacity of 928mAh/gat 100mA/g.When the current densities change constantly,the electrode performance also indicate the different capacityof1041mAh/g at 100mA,773mAh/g at 200mA,678mAh/g at 300mA,599mAh/g at500mA,504mAh/g at 1000mA,432mAh/g at 1500mA.When the current density returned to 100mA again,the capacity also returned to 725mAh/g.At last,decided to choose dopamine as carbon source coating on the surface of SiO₂.After first cycle,the charge and discharge specific capacity is 540mAh/g and947mAh/g.In summary,the SiO₂/C/X?G?CNTs?composite material can be synthesized successfully from the halloysite with a very simple way,and it can demonstrate a very high reversible capacity at different current.The pretty electrochemical performance may be due to the unique hollow nanotubes structure,in which could prevent the volume expansion and contribute to maintain the primary morphology.After 100 cycles,the half-cell battery has not showed the obvious capacities fade.