Preparation Of Modified SnO₂ Nanomaterials And Research On Its Electrochemical Performance

Lithium-ion batteries have a wide range of applicati ons in modern electronic devices and electric vehicles,and are one of the current research hotspots.Although graphite is widely used as a negative electrode material in commercial lithium-ion batteries,its low theoretical capacity limits its use in high capacity devices.With a theoretical capacity of 782 m Ah/g,SnO ₂ is considered to be one of the ideal anode materials for next-generation lithium-ion batteries.However,the traditional SnO ₂anode material has a volume expansion rate as high as 300%in th e process of lithium intercalation/delithiation,resulting in severe electrode smashing and severe capacity attenuation.At the same time,the low conductivity leads to poor rate performance,and solid forms continuously during the cycling process.The ele ctrolyte interface SEI film leads to poor cycling performance.To solve the above problems,one method is to prepare nanostructured SnO₂.Another method is to introduce different nanoparticles to form a nanocomposite material to alleviate the problem of ca pacity fade and stability degradation caused by volume expansion.Based on this,SnO₂ nanoparticles and nanowires were prepared by hydrothermal method.Then SnO₂ nanoparticles were modified by C coating,and SnO ₂ nanowires were modified by Co doping.The S EM,TEM,XRD and electrochemistry were used to modify the SnO₂ nanowires.The micro-morphology,phase and electrochemical properties of the samples were analyzed and the effects of morphology and relative electrochemical properties were investigated.Firstly,SnO₂ nanoparticles and nanowires were prepared by hydrothermal method,and their nanostructures were modified.Then the morphology,phase and electrochemical properties of SnO₂ nanoparticles and nanowires were analyzed by SEM,TEM,XRD and electrochemi cal tests.The results show that SnO ₂ nanoparticles discharge capacity is up to 680 m Ah/g for the first time,but then attenuate rapidly.After 20 cycles,the discharge specific capacity is only 205 m Ah/g,and the capacity retention rate is only 30.14%.Th e first discharge specific capacity of SnO ₂ nanowires was 257 m Ah/g.After 20 cycles,the discharge specific capacity was 203 m Ah/g,and the capacity retention rate was as high as 78.98%.It shows that the cycle stability of SnO₂ nanoparticles needs to be further improved,while SnO₂ nanowires need to improve the discharge specific capacity.On the basis of the above,the SnO ₂@C nanocomposite was prepared by hydrothermal method using a stable C material coated with modified SnO ₂nanoparticles.Compared with pure SnO₂ nanoparticles,SnO₂@C nanocomposites exhibited good cycle stability and high specific discharge capacity.The initial discharge specific capacity was as high as 1150 m Ah/g.After 20 cycles,the discharge specific capacity remained.At around 453 m Ah/g,the specific discharge capacity of pure SnO₂ nanoparticles is 253 m Ah/g higher.The capacity retention rate was 39.39%higher than that of pure SnO₂ nanoparticles.Finally,the SnO₂/Co CO₃ nanocomposites were prepared by the secondary hydrothermal method.The specific capacity of the SnO ₂ nanowires was increased by the high capacity of the Co-based materials.The first discharge of SnO ₂/Co CO₃nanocomposites reached 1608 m Ah/g.After 20 cycles,the discharge specific capacity of SnO₂/Co CO₃ nanocomposites was 623 m Ah/g,which was 420 m Ah/g higher than that after 20 times of pure SnO₂ nanowires.