Preparation And Lithium Storage Of Metal/Metal Oxide Electrode Materials Based On Electrospinning

Lithium-ion secondary battery(LIBs)has shown many advantages since its appearance,such as high specific capacity,low self-discharge rate,no memory effect,less pollution to the environment,so it is favored by people.However,commercial lithium-ion secondary batteries have some problems such as high current resistance and low specific capacity,so there is much room for improvement.As a possible replacement material,Metal/metal oxides have large theoretical capacity,good safety and abundant reserves.The metal/metal oxides and carbon materials are prepared into composite materials through a certain process,and the composite material is designed as micron/nano size,in order to effectively restrain the volume strain of the electrode in the process of charge/discharge,improve the transfer rate of Li⁺,so as to improve the performance of lithium-ion battery.In this thesis,we design and synthesize metal/metal oxide electrode materials bonded with carbon at micro and nano scale,so that the micro-nano electrode material has more abundant e/Li⁺transport channels,more active reaction sites,high specific capacity,long cycle life,better rate performance and other advantages.This paper mainly introduces the following work:(1)Firstly,we prepared Sn O₂@C microstrip composites by using static spinning,heat treatment and polymer carbon coating technology.Due to the synergistic effect of carbon coating and Sn O₂ microbelt structure design,the specific capacity of the composite electrode remains at 504 m Ah g^-1 after 100 cycles at the current density of0.2 A g^-1,which shows a good lithium storage performance.(2)In the second work,we improved the way of recombination of the active material and carbon,and prepared ultrafine antimony nanoparticles encapsulated in a three-dimensional carbon fiber frame composite material(U-Sb-NPs@CMF)using electrospinning technology and subsequent heat treatment process.This preparation strategy makes the composite of Sb particles and carbon more sufficient and uniform,effectively avoids the volume strain of Sb anode in the process of charge/discharge,and provides a fast 3D transport path for e/Li⁺.Benefit from this novel structural design,the composite material show excellent electrochemical performance:the specific capacity of the electrode can reach 622 m Ah g^-1 after 200 cycles at a density of 1 A g^-1,and 507m Ah g^-1 after 2000 cycles at a density of 2 A g^-1.Even at a high current density of 5 A g^-1,the capacity can be maintained at about 350 m Ah g^-1 after 5000 long-term cycles.These excellent charge-discharge properties indicate that U-Sb-NPs@CMF has a good application prospect.(3)Amorphous Ge O₂/C nanofibers were prepared as anode materials for high rate and long cycle lithium-ion batteries.Due to the existence of Ge O₂ in amorphous form and the supporting effect of C frame on Ge O₂,the composite electrode has excellent cycling stability.At the current density of 0.2A g^-1,the capacity of the composite electrode can reach 1081 m Ah g^-1 after 1000 cycles.The electrode also exhibits excellent rate performance,with minimal capacity attenuation as the current density gradually doubles,even at a high current of 5 A g^-1,the capacity of the electrode can still reach 453m Ah g^-1,and when the current returns to 0.2 A g^-1,the specific capacity can be restored to 1150 m Ah g^-1,and can be maintained for a long cycle number.