Construction Of Iron-Based Oxygen/Sulfide Heterojunction And Its Sodium Ion Battery Anode Performance Study

Sodium-ion batteries(SIBs)is an auspicious alternative for lithium-ion batteries as a new type of energy storage device which plays a significant role in energy storage field owing to its low cost,high specific capacity and long cycle life.Furthermore,as anode materials for sodium ion batteries,the iron-based oxygen/sulfide combine virtues of high theoretical specific capacity,low price and safety,delivering an enormous development prospect.However,its poor electrical conductivity and large volume change during cycling severely inhibit the further development of its rate capability and cycling stability.In this paper,Fe3O4/FeS/Fe three-phase heterogeneous catalytic N-carbon nanotubes and graphite acetylene loaded sulfur-doped Fe2O3 hollow nanoparticles was developed via the design of material morphological structure,heteroatom composite and the construction of heterojunction strategy.We prepared the anode materials of recycled waste facial cleansing towel loaded Fe3O4/FeS2 self-supported carbon film for SIBs which can effectively alleviate the volume expansion and promote electron/ion kinetic transport,thus improving reversible redox reactions.The effects of different material composites,morphological configurations and heterogeneous interface modulation on the electrochemical performance were explored,and the energy storage mechanism was investigated in detail.1.The Fe3O4/FeS2 heterojunction encapsulated in carbon membrane(FOSM)as freestanding anode for SIBs through dipping a washcloth into FeCl3 aqueous followed by calcination at 650℃(FOSM-650).The inner porous carbon fiber skeleton can support the outer Fe3O4/FeS2 heterojunction to cast outstanding flexibility,provide a bridge for electron transfer,and alleviate the volume expansion during charging/discharging.Meanwhile,direct contact of the outer Fe3O4/FeS2 with the electrolyte can shorten Na+diffusion path,combining with fast electron diffusion to promote the rapid and reversible electrochemical reaction.Therefore,as a freestanding anode for SIBs,FOSM-650 displays superior electrochemical performance in a half-cell system.It exhibits a high specific capacity of 1.25 mAh cm-2 at a current density of 0.5 A cm-2 and still possesses 0.47 mAh cm-2 after 1000 cycles even increasing the current density of 2.0 A cm-2.In particular,in the FOSM-650//NVP@C full-cell system,at a current density of 2.0 A cm-2,the specific capacity after 10 FOSM-650 has high specific capacity,excellent cycle stability and cycle multiplier performance.This work not only provides a feasible and high value-added approaches that recycle waste cleansing wipes to alleviate environmental pollution,but also promotes the development of iron-based freestanding materials with high energy density.2.The Fe3O4/Fe/FeS tri-heterojunction node spawned N-carbon nanotube scaffold structure(FHNCS)was constructed by using the modified MIL-88B as template followed catalytic growth and sulfidation process.The unique scaffolding structure provides multichannel for permeation of electrolyte,which offers more active sites and shortens Na+diffusion path.Meanwhile,the structure exhibits excellent mechanical stability to effectively alleviate the volume expansion during circulation.Furthermore,the Fe in Fe3O4/Fe heterojunction can adjust the D-band center of Fe3O4 and enhance the adsorption between Fe3O4 and NaS2,which restrains the shuttle effect.As a result,the FHNCS exhibits a high specific capacity of 436 mAh g-1 at a current density of 0.5 A g-1,and 84.7%and 73.4%of the initial capacity are maintained after 100 cycles at a current density of 0.5 A g-1 and 1000 cycles at a high current density of 1 A g-1,exhibits outstanding cycle stability.In addition,the full SIBs based on FHNCS anode cathode and NVP@C cathode exhibits excellent full-cell performance.This work provides a research direction for the development of anode materials for SIBs.3.This work prepared high-performance SIBs anode material(GDY-Fe-1)by using graphitylene as substrate and then loading sulfur-doped Fe2O3 hollow nanoparticles.GDY consists of two hybrid orbital conjugate structures,sp and sp2,in which the vertex of GDY cavity triangle(benzene ring)has the strongest electronegativity,which can adsorb and aggregate Fe3+.In the hydrothermal process,Fe3+ was hydrolyzed and crystallized to nucleate and grow into Fe2O3 nanoparticles,and then through Oswald Ripening the homogeneous hollow Fe2O3 loaded GDY composite was constructed.After vulcanization,a kind of hollow Fe2O3 nanoparticles(GDY-Fe-1)with sulphide layers on the surface was synthesized.GDY has excellent electrical conductivity and can promote the rapid transfer of electrons.Due to the Fe2O3 hollow nanoparticle structure that effectively mitigates the volume expansion during the charging/discharging process,and a high specific capacity can be attributed to the sulfide layer on its surface.GDY-Fe-1 exhibits excellent electrochemical performance with a high specific capacity of 511.8 mAh g-1 was obtained after 100 cycles at a voltage window of 0.01-2.8 V and a current density of 0.1 A g-1.Meanwhile,it still delivers a specific capacity of 423.6 mAh g_-after 750 cycles at a high current density of 1.0 A g-1.Therefore,GDY-Fe-1 can be used as a high-performance anode material for SIBs further promote the rapid development of SIBs.