Electrospinning hollow nanofibers. For this purpose, the fabrication of new anode materials from composite nanofibers was carried out and the electrochemical performances of the obtained anodes were analyzed in detail. In the first of the studies to develop a high-capacity anode for lithium-ion batteries, experimental studies were conducted to obtain the anode material composed of composite SnO2/porous carbon nanofibers whose outer surface was covered with amorphous nanofibers (10nm) covered is carbon.
First, porous carbon nanofibers were produced using electrospinning and carbonization processes. It aims to form a large-capacity anode by coating the surface of porous carbon nanofibers obtained by an electroplating method with SnO2 nanoparticles. The porous structure of the carbon nanofibers used for the electroplating process made it possible to coat more SnO2 on the surface of the fibers and consequently obtain a larger anode capacity. The outer surface of the SnO2/carbon composite nanofibers obtained as a result of the electroplating process is finally coated with nano-sized amorphous carbon by the chemical vapor deposition (CVD) method to create a long anode lifetime along here. Experimental studies were conducted on using the directly fabricated composite nanofibers as an anode material for lithium-ion batteries without the use of binding chemicals and current collectors. According to the results of electrochemical tests, it was observed that higher anode capacity was obtained when carbon nanofibers having a porous structure were used. Furthermore, structural characterization studies demonstrated that more SnO2 nanoparticles are coated on the surface of porous carbon nanofibers. Furthermore, according to the results obtained from the electrochemical tests, it was found that the SnO2/carbon composite nanofibers coated with amorphous carbon exhibited a much longer anode life than those with no amorphous carbon coating.
Electrospinning hollow nanofibers
Nanofibers are fibers with a diameter of about one nanometer. Nanofibers can be made from different polymers and thus have different physical properties and application potential. Examples of natural polymers are collagen, cellulose, silk fibroin, keratin, gelatin, and polysaccharides such as chitosan and alginate. [1][2] Examples of synthetic polymers include poly(lactic acid) (PLA), polycaprolactone (PCL), polyurethane (PU), poly(lactic-co-glycolic acid) (PLGA), poly(3-hydroxybutyrate-co -3 -Hydroxyvalerate (PHBV) and poly(ethylene-co-vinyl acetate) (PEVA) [1] [2] The polymer chains are linked by covalent bonds [3] The diameter of the nanofibers depends on the type of polymer used and the manufacturing process.[ 4] All polymeric nanofibers are unique due to their high surface area-to-volume ratio, high porosity, significant mechanical strength, and functional flexibility compared to their microfiber counterparts.
An example of a cellulose nanofiber network.
There are several methods to fabricate nanofibers, including drawing, electrospinning, self-assembly, template synthesis, and thermally induced phase separation. Electrospinning is the most widely used method to produce nanofibers due to its simple structure, ability to mass-produce continuous nanofibers from all types of polymers, and ability to produce very fine fibers with controllable diameter, composition, and direction. [5] This flexibility allows the shape and arrangement of the fibers to be controlled to create different structures (i.e., hollow, planar, and ribbon-like) depending on the intended application. Scientists and engineers from the University of Minnesota succeeded in producing nanofibers with a thickness of 36 nm using an innovative melt-processing method suitable for industrial mass production.
It was observed that the amorphous carbon coated SnO2/porous carbon nanofiber anodes obtained as a result of the study retained 78% of their original capacity and the Columbia efficiency 99.8% as a result of 100 times charge-discharge process fraud. In another study to develop high-capacity anodes, research was conducted on the development of an anode material composed of silicon/silica/carbon (Si/SiO2/Carbon) composite nanofibers coated with nanometer-scale (10 nm) amorphous carbon . In a first step, composite Si/SiO2/PVA nanofibers were produced from Si nanoparticles, a sol-gel solution of tetraethylorthosilicate (TEOS) and a solution obtained from alcohol polyvinyl (PVA) by electrospinning. The obtained nanofibers were transformed into Si/SiO2/Carbon composite nanofibers after the applied carbonization process. Battery tests were conducted on the use of Si/SiO2/Carbon composite nanofibers, which as a result of the carbonization process are used directly as an anode material for lithium-ion batteries without the need for chemical binders and collectors. The silicon in the structure of the formed Si/SiO2/Carbon composite nanofibers was used to provide high anode capacitance.