Research On Preparation And Electrochemical Properties Of Fe₃O₄ And SnO₂ Nanoarray As Anode For Lithium-ion Battery

The theoretical specific capacity of transition metal oxide is 2 to 3 times that of commercial graphite anode,and its good safety is considered to be one of the anode materials with great application potential.Among the transition metal oxide anode materials,both Fe₃O₄ and SnO₂ have higher theoretical specific capacities,926 m Ah/g and 1494 m Ah/g,respectively.However,they will have a large volume change during the Li⁺insertion/extraction process.The volume expansion of Fe₃O₄ is 100%,while the volume change of SnO₂ is more drastic,up to 300%,which makes lithium-ion batteries unable to achieve long cycles and rapid Charging and discharging restrict their commercial application.The preparation of ordered Fe₃O₄ and SnO₂ one-dimensional nanostructures with gaps can not only provide enough buffer space for their severe volume changes in the electrochemical process,but also have a large specific surface area,an orderly electron transport channel and a short the advantages of lithium ion diffusion path and other advantages are expected to solve the application difficulties of Fe₃O₄ and SnO₂ anode materials and promote their commercial applications.It is of practical significance to prepare Fe₃O₄ and SnO₂ anode materials with nano-pillar array structure,and to explore their electrochemical performance.Based on this,the main research content and results of this thesis are as follows:(1)A highly ordered array of Fe₃O₄ and SnO₂ nanopillars was prepared using pulsed laser deposition technology combined with ultra-thin double-pass anodic aluminum oxide template.Using scanning electron microscope,X-ray diffraction,X-ray photoelectron spectroscopy and scanning transmission electron microscopy,the prepared Fe₃O₄ and SnO₂ anode materials were characterized in morphology,element composition and microstructure.The research results showed that the prepared nanometer The column arrangement is highly ordered,and the element composition is free of impurities other than Fe₃O₄ and SnO₂.In addition,the growth mode of nanopillars on the Cu foil current collector is epitaxial growth,with good crystal structure matching and clear interfaces.(2)The highly ordered Fe₃O₄ nanopillar array is used as the anode material of the lithium ion battery,and its electrochemical performance is analyzed.The research results show that the Fe₃O₄ nanopillar array anode material has stable long-cycle performance.Its specific discharge capacity can still be maintained at about 350 m Ah/g at the 400th cycle.In addition,it also has excellent rate performance.At an ultra-high current density of 60 C,its discharge specific capacity is about 312.5 m Ah/g,and when the current density is reduced by 2 C,the discharge specific capacity returns to about550.6 m Ah/g.Analysis believes that its good electrochemical performance can be attributed to the ordered nanopillar array structure and the close interface combination between the nanomaterial and the Cu foil current collector.(3)The highly ordered SnO₂ nanopillar array is used as the anode material of lithium-ion battery,and its electrochemical performance is studied.The results show that it not only has excellent long cycle performance,but also has excellent rate performance.In 2000-6500 cycles,its discharge specific capacity has been stable at about 313 m Ah/g,and there is no attenuation.In addition,at an ultra-high rate of 64 C,it still retains a specific discharge capacity of about 277.8 m Ah/g,and when the current density is reduced to 2 C,the specific discharge capacity can be restored to about 670m Ah/g.Studies believe that the highly ordered nanopillar array structure can effectively alleviate the huge volume expansion of SnO₂ during charge and discharge,maintain the integrity of the nanostructure,and greatly improve its electrochemical performance.