Preparation And Energy Storage Properties Of Fe₂O₃/Multilayer Graphene

Nano iron oxide is an important anode material for lithium-ion batteries and supercapacitors.However,the low conductivity of iron oxide itself and the volumetric effect during charging and discharging can cause damage to the electrodes,affecting their multiplicity and cycling performance.The preparation of iron oxide nanocomposites with graphene is an important solution,however,existing studies have mainly used graphene oxide substrates,which are not only expensive to prepare,but the breakage of carbon rings also deteriorates the electrical conductivity.The multilayer graphene prepared by ultrasonication is simple to prepare,has an intact carbon structure on the surface,and its good electrical conductivity can provide a good substrate for iron oxide nanoparticles.However,the low chemical activity of its surface due to the absence of reactive groups leads to the difficulty of preparing the composite masses by chemical methods.This thesis investigates new preparation methods to obtain uniformly distributed iron oxide nanoparticles,amorphous iron oxide nanoparticles and flaky hydroxy iron oxide on the surface of multilayer graphene,and investigates their performance in lithiumion batteries and supercapacitors.Details of the research for the thesis are as follows.(1)Uniformly distributed iron oxide nanoparticles with a particle diameter of less than 10 nm were prepared on the surface of multilayer graphene using a one-step water bath method.The electrochemical performance of lithium-ion battery cathode with the composite was tested and the results show that it has excellent lithium storage performance,with the discharge specific capacity remaining at 1071 mAh g-1(0.1 C)after 100 cycles.The microstructure and electrochemical properties of the composites were compared with those prepared using graphene oxide and reduced graphene as substrates.The results show that the multilayer graphene-based composites have a more uniform distribution of iron oxide nanoparticles and better electrochemical properties.(2)Uniformly distributed amorphous iron oxide nanoparticles were prepared on the surface of multilayer graphene by the addition of disodium ethylenediaminetetraacetate(EDTA-2Na)using a one-step water bath method.The paper investigates the effect of EDTA2Na addition on the microscopic morphology and lithium storage properties of the composites.Studies have shown that EDTA-2Na enables the formation of amorphous iron oxides,but excessive additions cause the iron oxides to form larger particles and reduce the amount of iron oxide produced.At an EDTA-2Na addition of 10 mg,the composite has the best cycle performance(1067.2 mAh g-1 at 100 mA g-1 for 100 cycles)and rate performance(524 mAh g-1 at 2000 mA g-1).(3)Flaky hydroxyiron oxide was prepared on the surface of multilayer graphene by the simultaneous addition of EDTA-2Na and sodium acetate(CH3COONa)using a one-step water bath method.The electrochemical performance of the composite as a supercapacitor electrode material was tested using a three-electrode test system.The results show that the composite has a discharge specific capacity of 860.9 F g-1 and 376.2 F g-1 at 2 A g-1 and 10 A g-1,Its specific capacity and multiplicative properties are superior to those of iron oxide nanoparticles/multilayer graphene and amorphous iron oxide/multilayer graphene.