Syntheses Of Carbon Based Composites And Their Electrochemical Performances For Lithium/Sodium Rechargeable Batteries

The ever-growing demand for green and portable energy storage,academic and industrial fields have been pursuing for the more potential,higher electrochemical performance of lithium secondary batteries.It is well known that the electrochemical properties of high performance of lithium secondary batteries are highly dependent on their electrode materials,and the electrochemical properties of the electrode materials associate with the composition,structural and functional properties of the electrode material.On the other hand,rechargeable sodium ion batteries have been generally considered as a kind of energy storage devices because of the larger reserves,uniform distribution on the earth,environnent-friendly and good security of sodium At present,sodium ion battery is in the primary state of its development,especially the development and utilization of the high sodium storage performance of anode material.Herein,earbon-based composite electrode materials are designed and fabrication by carbon-based and as-made electrode materials,and used for the electrode material of lithium/sodium secondary battery to study their electrochemical properties,including the following contents:?1?Free-standing MnO₂/RGO composite papers are successfully fabricated using the different mass ratios between MnO₂ nanotubes and GO by fecile vacuum filtration and subsequent thermal reduction route.By using the MnO₂/RGO membranes directly as anode materials for lithium batteries,the membranes for half LIBs show superb electroehemical perforlance.Importantly,the electrochemical performances of MnO₂/RGO membranes show a strong dependence on the MnO₂ nano tube contents in the hybrids.In addition,the lithium-ion full batteries are febricated by using MnO₂/RGO membrane as anode and LiCoO₂ as cathode,and also exhibit electrochemical performance in full batteries system,showing the advantages of preparation of electrode preparation and fabrication of batteries.?2?The free-standing ternary CoSnO3 nanacube/graphene/carbon nanotubes?CoSnO3 nanocube/GN/CNTs?and CoSnO3 nanobox/GN/CNTs composite papers have been fabricated by a simple filtration method together with a post-heat-treatment method for the first time,in which two different structures of CoSn?OH?6 nanoparticeks,GO and CNTs as precursors.In this unique composite structure,amorphous CoSnO3 nanoparticles very homogeneously and tightly lie on the layer-by-layer of 3D GN/CNTs scaffold.The 3D GN/CNTs network has excellent electrical conductivity and can further buffer the volume expansion of CoSnO3 during discharge.When used directly as binder-and conductive agent-free anodes for lithium-ion batteries,the electrochemical performances of the conleposite paper anodes are much better than those of pure CoSnO3 nanoparticles anode.Also,the hollow structure materials anodes show superior cyclic performances and excellent rate capability compare to those of the solid structural material anodes.?3?The porous 3D-graphene materials are synthesized by the traditional organic sol-gel chemistry and subsequent thermal-treatment using SiO₂ nanoparticles,GO,graphene,phenol and formaldehyde as precursors.Then,Fe3O4/3D-graphene composites are prepared by simple hydrothermal method.In this unique 3D composite structure,the 3D-graphene porous material with good electrical conductivity and high specific surface area can enhance the cond-uctivity of Fe3O4 nanoparticles and alleviate its volumetric expansion.Therefore,Fe3O4/3D-graphene composites still have the reversible specific capacity of 907.7 mAh g-1 after 300 cycles of current at 0.25 A g-1.?4?The hierarchical 3D-NCNT@MoS2 composites have been rational designed and synthesized by a one-pot hydrothermal reaction and subsequent post-heat-treatment method,in which Na2MoO4·2H2O,L-cysteine and polypyrrole?PPy?are employed as precursors.In this architecture,thelD NCNTs can effectively alleviate the volume changes,improve the electronic conductivity,and maximize the loading of MoS2 nanosheets,thereby providing unique advantages over the traditional bulk materials.With these inspiring merits,this novel 3D-NCNT@MoS2 composites offer multiple attractive features as anode material in LIBs and SIBs.As a consequence,the as-prepared hierarchical 3D-NCNT@MoS2 manifests remarkable electrochemical performance in LIBs and SIBs.?5?The 3D ternary hierarchical porous rGO/MnO₂-S aerogel?rGM-SA?composites are designed and fabricated by a simple and environmentally-benign hydrothermal method using ultrathin MnO₂ nanosheets,GO and S as precursors.In the rGM-SA composites,ultrathin MnO₂ nanosheets?MnO₂ NSs?are anchored into rGO to form a carbon/inorganic matrix to host nanosized sulfur that is the active component for energy storage.Furthermore,the 3D ternary hierarchical porous rGM-SA materials have the high specific surface area to facilitate transportation of the electrolyte ion and electron and accommodate generated insoluble sulfur active materials from the cathode and volumetric expansion of sulfur to Li2S during charge/discharge process.As expected,the 3D ternary porous rGM-SA composites exhibit high specific capacity,rate capability,and cycling stability.