| Giant success has been achieved in lithium ion batteries(LIBs)among the past few decades,however,the rapidly popularized portable devises and electric vehicles have also risen the demand of high energy density and stable cycle performance to an ever-high level.Moreover,the short abundance of lithium element on earth makes it a hot issue to find a possible alternative of LIBs,and sodium ion batteries(SIBs)become a promising solution.Among the researches of electrodes materials for both LIBs and SIBs,iron sulfides have drawn much attention due to their relatively high specific capacity(600-1000 mAh g-1,compared to commercial graphene:372mAh g-1),non-toxic or pollution and the wide distribution of iron elements in nature.Sadly,the poor conductivity,severe volume expansion during repeatedly discharge/charge process,which may lead to the electrode pulverization,hinder the further application of iron sulfides.Under this circumstance,we reported,in this paper,two kinds of methods to combine iron sulfides with carbon materials so as to better shelter Li+/Na+with the hope to get an enhanced electrochemical performance,besides,we also made some simple explorations of silicon/silica materials obtained from industrial wastes.The details are as follows:1)We used two kinds of carbon templates(carbon nanotubes and microspheres)as bases,and then Fe3+ ions were coated outside via a hydro-thermal method.After the annealing process,we got carbon/iron sulfide composites.From the various characterization results,we found these composites with uniform distribution,hollow and core-shell structure.Benefiting from the advantages,the composites delivered high and stable cycle capacity(1000mAh g-1 after 100cycles)and good rate performance(500mAh g-1 at a high current density of 20C),2)We fabricated carbon/iron selenides composites via a similar method,and found a similar hollow and core-shell structure along with a high specific surface area.When applied as LIBs anodes,these materials delivered a high capacity,stable rate performance,and a steady charge/discharge platform,indicating a good prospect.3)The Fe1-xS/C products were prepared through a bottom-up method.The sulfur hollow spheres were initially obtained and then functioned as both a hollow template and a sulfur source for the following synthesis process.Then iron ions(Fe3+)were coated onto the sulfur spheres.A PDA layer was additionally added too.Iron sulfides spheres/carbon composite materials with a hollow structure could be obtained after annealing and this structure could be proved.Consequently,these iron sulfides/carbon materials exhibited excellent electrochemical performance(420mAh g-1 at 200mA g-1 after 200 cycles and the capacity retention reached 50%at 20 A g-1 during the rate test)as the anode materials in SIBs.4)The work in this chapter was based on actual production applications.The effects of different silicon sources and binder systems on battery performance were briefly explored.First,through the lateral comparison between single crystal silicon,polycrystalline silicon and amorphous silicon,which were derived from different crystallinity sources of industrial trim,the optimal choice of silicon source was preferred.The last task was to reduce the silica industrial waste to the silicon oxides material using a magnesium thermal reaction and apply it to a lithium ion battery. |
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