The Preparation Of Nanomaterials Based On The Composite Of GO And Antimony (or Tin)-based Compounds And The Performance Of Sodium Ion Batteries

Antimony(Sb)and tin(Sn)compounds have been widely regarded as ideal anodic materials in advanced sodium-ion batteries(SIBs)because of their abundant reserve,relatively low cost and high theoretical capacity.However,these substances intrinsic conduction ability are poor and they usually suffer from huge volume change during charging and discharging processes,leading to rapid capacity fading,which greatly hamper their practical application.At present,people propose many effective modification methods to improve the electrochemical performance of these substances,composite material with a variety of carbon is one of them.Among various kinds of carbon materials,graphene is an important category.Composing a carbonaceous matrix is a facile and effective way to improve the electrochemical performance,especially composing graphene or grapheme oxide has been a hot research.Graphene carbon materials with large specific surface area not only facilitates contact with electrolytes and shortens the transmission distance of sodium ion,but also improves the electrical conductivity and buffers volume expansion,resulting in improved cycling stability and rate capability.However,the synthetic process of antimony(or tin)compounds-graphene composites is often multiple,time-consuming,costly and pollutional.In this thesis,we present a general synthesis methods named room temperature solid state reaction method,this method is very simple,cost-effective and environmentally friendly.Antimony(or tin)compounds-graphene composites were prepared by using this method,graphene oxide(GO)or reduced graphene oxide(rGO)and antimony(or tin)compounds in situ recombined.These materials show excellent electrochemical performance as anode materials for SIBs.The main researches are as follows:(1)Sb4O5Cl2/GO precursor is quickly obtained by directly grinding antimony chloride and sodium hydroxide together at room temperature in the presence of graphene oxide(GO),and after subsequent room temperature solid reduction by NaBH4,the Sb/rGO composite is successfully obtained.The Sb/rGO composite exhibits enhanced sodium-storage performance in comparison with pure Sb particles,which were fabricated by the same process just without addition of GO.The discharge and charge capacities for the Sb/rGO composite in the 1st cycle is 992 and 527 mA h g-1,respectively,with a 53.1%of coulombic efficiency at a current density of 100 mA g-1.As the cycling continues,it can deliver a high charge capacity of 427 mA h g-1 at a current density of 100 mA g-1 after 45 cycles and has a capacity retention of 81%.As the cycling continues from the 5th cycle,coulombic efficiency maintains thereafter exceeding 98%.Nevertheless,the reversible discharge capacity of pure Sb particles decrease sharply from 233 mA h g-1(7.2%CE)for the 1st cycle to 16.8 mA h g-1 for the 2nd cycle,suggesting that the pure Sb particle electrode possesses an inferior cyclability.(2)Amorphous Sb2S3/GO composite(notes for a-Sb2S3/GO)is prepared by directly grinding antimony chloride and nine hydrated sodium sulfide together at room temperature in the presence of GO.Meanwhile,we explores the effect of different molecular weight of PEG as surfactant on sodium-storage performance.The results showed that the a-Sb2S3/GO-1 is obtained when we add small molecular weight of PEG(PEG200)and it exhibits optimal sodium-storage performance in terms of cycle stability and rate capability.The discharge and charge capacities for the a-Sb2S3/GO-1 composite in the 1st cycle are 870.5 and 612.9 mAh g-1,respectively,with a 70.4%of coulombic efficiency at a current density of 100 mA g-1.It can deliver a high reversible charge capacity of 405.1 mAh g-1 after 100 cycles at 100 mA g-1,which shows a good cycle stability.Evenly,it exhibits an outstanding rate performance with reversible charge capacity of 442.9 mA h g-1 at 5 A g-1,which shows tempting large current density performance.(3)SnO2/GO composite consists of uniform and ultrasmall SnO2 nanoparticles which have been protected and wrapped by the GO matrices,prepared by directly grinding stannic chloride pentahydrate and sodium hydroxide together at room temperature in the presence of GO.Menwhile,we also explores the effect of different molecular weight of PEG as surfactant on sodium-storage performance as well.The results show that the SnO2/GO-1 is obtained when we add small molecular weight of PEG(PEG200)and it exhibits optimal sodium-storage performance.Especially,it can deliver a high reversible charge capacity of 227.9 mA h g-1 after 200 cycles at 100 mA g-1 and an outstanding rate performance with reversible charge capacity of 196.7 mA h g-1 at 1A g-1.