Preparation And Properties Of Flexible Electrode Materials By Needle-free Electrospinning

Smart wearable is an application field of seamless combination of textiles and microelectronic devices,which has huge development potential.However,the size and stiffness of sensors,power supplies,circuit boards,wireless transmission and other devices in smart wearable equipment affect its wearing comfort and portability.As a result,flexible devices adapted to smart wearable products have become the research focus of researchers.Among them,the energy equipment of flexible electronic products has become one of the first key issues to be solved.Lithium-ion battery（LIBs）is the main power supply for lots of electronic products,but its application in smart wearable textiles is restricted by its features such as large rigidity,large volume,unbending and so on.Therefore,it is of great significance to realize flexible,lightweight and advanced flexible self-supporting batteries.In this paper,taking the flexible anode material of lithium-ion battery as the research object.The self-supporting flexible skeleton of carbon fiber with uniform texture and bendable was prepared by needle-free electrospinning equipment.The preparation process of electrospun film was determined through the optimization scheme.The controllable preparation of in-situ Mo O₂/C nanocomposites and hydrothermal Mo S₂@C nanocomposites were investigated.Their electrochemical properties as LIBs negative electrodes were tested and the lithium storage mechanism of each composite was explained.The main results are as follows:（1）The appropriate polymer and electrospinning process parameters are determined by factor analysis to prepare high-quality precursors of carbon fiber supporting skeleton.In a suitable environment,the polyacrylonitrile（PAN）electrospinning film with uniform texture and few defects was obtained by using 12%PAN solution under the condition of electrostatic pressure 20 k V,the receiving distance of 18 cm and the reciprocating rate of50 mm s^-1.After the electrospun membrane is pre-oxidized at 200℃and carbonized at600℃,a flexible carbon fiber support skeleton with extremely low bending stiffness and bendable can be obtained.This material has the potential to be used as a fiber framework for flexible electrodes in energy storage devices.（2）The flexible Mo O₂/C nanocomposites with network structure is obtained through needle-free electrospinning,pre-oxidation and carbonization.Mo O₂ nanoparticles are uniformly doped in the fiber.This special coating structure can effectively alleviate the volume expansion in the process of charge and discharge and prolong the service life of the electrode.At the same time,Mo O₂/C nanocomposites have excellent flexibility and self-supporting properties,giving them good structural stability.In addition,Mo O₂/C composite electrode exhibits excellent cycle performance,rate performance and specific capacity.Under the current density of 200 m A g^-1,the reversible specific capacity is 750 m Ah g^-1after 200 cycles,and the capacity retention is as high as 94%.（3）The Mo S₂@C nanocomposites with core-shell structure was prepared by hydrothermal method using PAN-based carbon fiber support skeleton as substrate.The carbon fiber support skeleton provides electrical conductivity and structural support.Mo S₂nanocrystals grow uniformly on the surface of the carbon fiber in the form of petals,which greatly shortens the diffusion path of Li⁺.Mo S₂@C composite material exhibits excellent flexibility and structural stability.In addition,the electrochemical test showed that the reversible specific capacity is still 290 m Ah g^-1 and the capacity retention rate reaches 93.5%at a current density of 1 A g^-1 for 1000 cycles,showing excellent cycle stability and cycle life.