Preparation And Electrochemical Study Of High Performance Nanomaterials

Electrospinning,as a unique method to prepare micro/nano-structured fiber membranes,has developed rapidly in recent years.Electrostatic spinning technology has the advantages of low cost,flexible and controllable,easy operation,and is widely used in porous electrodes,flexible devices,high-efficiency catalysis and other fields.By adjusting the parameters in the spinning process,various structures can be flexibly designed and manufactured,such as core-shell fiber,hollow fiber,porous fiber,etc.The nanofiber thin film prepared by electrospinning is applied to the electrode,and its large specific surface area can increase the contact area between the active substance and the electrolyte,and provide a large number of active sites,thus improving the performance of the electrode material.Lithium-ion battery（LIBs）has attracted much attention due to its high energy density and long cycle performance.However,due to the lithium content（about 0.0017%in the Earth’s crust）and high mining and refining costs,further development of lithium-ion batteries is severely hampered.Therefore,a resource-rich and low-cost energy source is urgently needed as an alternative.Potassium ion batteries（PIBs）have broad development prospects.Potassium,as the seventh element（about 2.09%in the crust）,is about 1229 times the content of lithium,and its relative reserves are abundant.Compared with lithium,which is mostly concentrated in South America,potassium is widely distributed and not subject to regional restrictions.Secondly,the metals,carbonates and layered oxides of potassium are all cheaper than the corresponding metals and compounds of lithium.In addition,the REDOX potential of potassium ions is close to that of lithium ions,making it possible to achieve high energy density and operating voltage.Firstly,The effects of technological parameters on the morphology of nanofibers prepared by electrospinning were studied using PVP as raw material.In coaxial electrostatic spinning,the factors affecting fiber morphology can be divided into solution parameters,process parameters and environmental parameters.The solution parameters include the mass fraction of the solute,the conductivity of the solution,the surface tension and the type of solvent.Process parameters can be divided into spinning voltage,injection speed,receiving distance,etc.In order to prepare core-shell carbon nanofibers,it is also necessary to control the injection velocity ratio between injection A and injection B,and at the same time,there are certain requirements for environmental humidity and sintering temperature.Secondly,tin sulfide（Sn S₂）is a promising anode material for potassium ion batteries due to its layered structure and high theoretical capacity.However,its further development is limited by slow kinetics,excessive volume expansion and polysulfide intermediates dissolution.In order to solve these problems,a kind of core-shell beads mixed fiber with item chain structure was designed as high performance anode materials for potassium ion batteries.The core of the bead is assembled from Sn S₂nanocrystals embedded in the N,S codoped carbon（NSC）matrix,which is then encapsulated in the shell of the NSC to form a core-shell structure of the bead inside the mixed fiber（CSN fiber）.Sn S₂@NSC CSN fiber’s carbon matrix provides a channel for rapid ion/electron transport,which helps reduce particle aggregation.At the same time,N,S co-doping structure is beneficial to capture polysulfide intermediates and reduce sulfur loss during the cycle.In addition,the void inside the bead can accommodate large volume changes.The experimental results show that the capacity decay rate is 0.013%after 2000 cycles at the current density of 2 A·g^-1.In summary,Sn S₂@NSC CSN fiber has excellent rate performance and stable cycling performance,which also provides a new idea for the design of high performance potassium storage electrode.