Design And Performance Of One-dimensional Structure Of Anode Material For Lithium-ion Battery

Lithium ion battery is an important energy storage device,which has been paid more and more attention in science,industry and people’s daily life.With the development of portable electronic devices and new energy vehicles,the electrochemical performance of batteries playsan important role.The key to improve the performance of battery is to design electrode materials.In order to meet the requirements of lithium-ion batteries,the exploration of new anode materials with good energy density and high performance had attracted widespread attention from researchers.One-dimensional nanomaterials with a unique three-dimensional network structure and high specific surface area,which are fully exposed to the electrolyte,can provide a chanel for electronic transmission.The internal stress in anode can be relieved and the anode structure remain consistent because of the intercalation characteristics of lithium ion in One-dimensional anode materials.Therefore the electrochemical performance would be improved.In this work,two kinds of one-dimensional multi-component nanomaterials were designed as anode materials.The electron transfer rate can be improved by the increase of conductivity on anode surface.The sufficient contact between the negative electrode material and the electrolyte were achieved by increasing the specific surface area,which can provide more active sites.Tin oxide（SnO₂）,zinc oxide（ZnO）and silica（SiO₂）aerogel with higher theoretical capacity were selected as the active material in the anode materials.And the research was focused on the influencesof their microstructure on the physical and the electrochemical properties.The main researches are as follows:（1）SnO₂/ZnO hollow nanotubes were prepared from two different molecular weight polyvinylpyrrolidone（PVP）by electrospinning and heat treatment.The morphology and electrochemical properties of the hollow nanotubes prepared by PVP with different molecular weight were different.The mechanism study showed that different morphologies of hollow nanotubes can be controlled by changing the molecular weight of PVP.The surface structure of SnO₂/ZnO nanotubes（SnO₂/ZnO-L）with low molecular weight PVP as precursor was loose,and the phenomenon of collapse and agglomeration occured.The SnO₂/ZnO nanotubes（SnO₂/ZnO-H）with high molecular weight PVP as precursor had smaller diameter,denser structure and higher electrochemical performance.By in-situ polymerization in ice water bath,polypyrrole（PPy）was coated on the surface of SnO₂/ZnO-H,which further improved the conductivity and stability of SnO₂/ZnO-H.SnO₂/ZnO@PPy inhibited the volume expansion of metal oxides during charging and discharging,and improved the reversible capacity of the anode.After 100 cycles at 0.2 C,the discharge capacity of SnO₂/ZnO@PPy was 626.1 m Ah g^-1 with stable cycle performance,excellent rate performance and outstanding structural stability.（2）Porous SiO₂ aerogels/carbon nanofibers（SA/CNF）flexible anode materials were prepared by electrospinning and heat treatment.Polyacrylonitrile（PAN）was used as carbonized polymer and porous structures were obtained by decomposing PMMA.In addition,SiO₂ aerogels with abundant porosity were introduced into the carbon nanofibers,resulting in higher specific surface area.When the SiO₂ aerogel content reached 2 wt%（SA-2/CNF）,the electrochemical performance was the best.At 0.2 C,the capacity of the 100cycle was as high as 709.1 m Ah g^-1.The capacity was maintained at 454.4 m Ah g^-1 at 2 C after 600 cycles.All the samples showed outstanding structural stability and superior rate performance.The highlightwas that the SA-2/CNF flexible electrode could be used directlywithout any adhesive or conductive agent.This research provided a simple method for the preparation of high-performance flexible electrodes.