Synthesis And Performances Of Doped Ferrous Carbonate And Bamboo Charcoal Based Composites As Anode Materials For Lithium-ion Batteries

Lithium ion batteries?LIBs?have become one of the preferred power sources for new energy vehicles due to its excellent properties,such as high energy density,good safety,environmental friendliness,low self-discharge rate and no memory effect.However,it is difficult for the tradition carbon anode materials to meet the high energy density and safety of power batteries,so development of new anode materials has become an important research.The Si-based materials,transition metal oxide and sulfide are concerned with the highly theoretical storage lithium capacity.However,the volume expansion of these materials is very serious during lithium ion extraction/insertion,which causes the materials to be pulverized from the current collector,thus affecting the cycle performance.For the above reasons,in this work,cockscomb-liked Mn_xFe_1-xCO₃ nanomaterials,Mn_0.2Fe_0.8CO₃/rGO composite,Fe₂O₃/bamboo charcoal,MoS₂/bamboo charcoal and Si/C composites derived from bamboo charcoal were prepared.Then,a series of characterization and performances test were used to analyze and study the morphology,structure and lithium storage properties of the as-prepared materials.Partial manganese substitution of iron in ferrous carbonate(Mn_xFe_1-xCO₃)is obtained via an one-step hydrothermal method.The results of XRD demonstrate that Mn-doping does not obviously influence the phase structure.Mn_xFe_1-xCO₃ possesses cockscomb-like and tunnel structures observed by SEM images.Meanwhile,the results of XPS further demonstrate the existence of Fe²⁺and Mn²⁺.Mn-Doped FeCO₃ samples remarkably improved the galvanostatic charge/discharge stability and rate capability as anode materials for lithium-ion batteries because of the synergistic behavior of Fe²⁺and Mn²⁺with cockscomb-like and tunnel structures.Mn_x Fe_1-xCO₃?x=0.2?as an anode material delivers an initial specific discharge capacity of 2400 mAh g^-1 at 200 mA g^-1,373 mAh g^-1 at 1600mA g^-1,and the discharge capacity of 904 mAh g^-1 over 100 cycles at 200 m A g^-1.Graphene oxide?GO?was prepared by modified Hummer method.Then,Mn_0.2Fe_0.8CO₃/rGO?MFCOG?material was synthesized via the one-step hydrothermal method.Effects of doping amounts of manganese ions and adding graphene on the electrochemical properties were investigated.From the SEM and TEM images,it can be observed that the transition metal carbonate nanopaticles are uniformly anchored on the graphene sheets.The results of electrochemical performance show that the MFCOG exhibited optimal electrochemical performance.The reversible capacity of 1223 mAh g^-1can be achieved after 120 cycles at 200 mA g^-1.Furthermore,MFCOG displayed a residual reversible capacity of 613 mAh g^-1 at 1600 mA g^-1.Through the high temperature solid state catalytic activation,surface modification and loading Fe₂O₃ nanoparticles.A series of as-prepared samples derived from bamboo charcoal were obtained.Seen from the image of scanning electron microscopy?SEM?,the bamboo charcoal emerged a hierarchical porous carbon-based microscopic structure and Fe₂O₃ nanoparticles uniformly anchored on the surface and in hole of carbon matrix with sizes ranging from 80 to 100 nm.The samples show a high specific surface area and exhibit excellent electrochemical property as anodes for lithium batteries.Especially,the concentrated nitric acid treated material displayed a reversible capacity of 327 mAh g^-1after 150 cycles at 200 mA g^-1 and retained a capacity of 278 mAh g^-1 at 1600 mA g^-1.When the modified bamboo charcoal incorporated with Fe₂O₃ nanoparticles,the composite delivered a specific capacity of 1094 mAh g^-1 over 150 cycles at 200 m A g^-1 and a high capacity of 765 mAh g^-1 even at 1600 mA g^-1.Therefore,the composite is a promising candidate for anode material of lithium-ion batteries.Through one-pot hydrothermal route,MoS₂ nanosheets were loaded on the surface of modified bamboo charcoal with ammonium molybdate and thiourea as raw materia.SEM and XRD results show that the microspheres formed by MoS₂ nanoflake were uniformly loaded on the surface of modified bamboo charcoal.In addition,the MS-2 composite shows the best electrochemical performance,which displays an initial specific discharge capacity of 1867 mAh g^-1 at the current density of 200 mA g^-1 and 672 mAh g^-1 over 200 cycles,even a reversible capacity of 581 mAh g^-1 at 1600 mA g^-1.Porous silicon was prepared from commercial bamboo charcoal by acid washing,high temperature calcination and magnesium thermal reduction.Then,a layer of amorphous carbon was coated on the surface of porous silicon by high-temperature calcination of polyacrylonitrile?PAN?coating.The content of porous silicon on the structure,and the electrochemical performance of the composite were also investigated.The electrochemical test results show that the amorphous carbon layer on the surface of porous silicon can effectively buffer the volume change of silicon and benefit to improve the cycle and rate performance.Especially,the SP15 sample shows the better electrochemical performance.It displays a reversible capacity of 603 mAh g^-1 over 200 cycles at 200 mA g^-1,even a reversible capacity of 360 mAh g^-1 at 1600 mA g^-1.