Study On Preparation And Performance Of Bimetallic Oxide For Lithium-ion Batteries

Nowadays,the main source of global energy consumption is fossil fuels which are not renewable or not distributed homogeneously.It has been a major concern for most countries whether energy can be cleanly and efficiently used.In line with the social needs,rechargeable batteries have emerged.Because rechargeable batteries store electricity efficiently in a chemical form,they have attracted much attention in the reserve of renewable energy（such as solar,tidal,wind,etc.）,and they also play a crucial role in electric vehicles（EVs）.Currently,there is no doubt that lithium-ion batteries（LIBs）dominate the electrochemical energy storage（EES）market due to their irreplaceable advantages over other types of rechargeable batteries in terms of energy density.However,the theoretical specific capacity（372 m Ah/g）of commercial graphite-based materials as LIB anodes is limited,and the Li⁺diffusion rate is poor.Therefore,it has realistic significance to seek a next-generation LIB anode material with high capacity.In recent years,bimetallic oxides（such as Zn Mn₂O₄,ZnFe₂O₄,and Zn Co₂O₄）have received more and more attention due to their high specific capacity.Unfortunately,when it is used as an electrode for charging and discharging,it is easily crushed and the capacity decays quickly because of their poor conductivity and large volume changes.To get around this phenomenon,researchers improve the electrochemical performance of bimetallic oxides by enhancing the electrical conductivity of the material and alleviating the volume change caused during charging and discharging.Effective methods include preparing nano-level bimetallic oxides,compounding with high-conductivity materials（carbon）or designing bimetallic oxides with 3D porous structures.In response to these situations,this thesis uses different methods to synthesize several bimetallic oxides.At the same time,its morphology and electrochemical performance were characterized.This paper mainly includes the following contents:1:ZnO/ZnFe₂O₄@reduced graphene oxide（RGO）nanocomposites have been successfully synthesized through annealing treatment of Zn/Fe MOF-5@GO precursor.The ZnO/ZnFe₂O₄@RGO electrode show rate capacity of 655 m Ah/g after 200 cycles at 0.2 A/g and excellent cycle stability.The unique structure of ZnO/ZnFe₂O₄@RGO nanocomposites can inhibit the aggregation of ZnO/ZnFe₂O₄,adapt to volume expansion and enhance the conductivity in the charge/discharge cycle,so the ZnO/ZnFe₂O₄@RGO electrode exhibits excellent electrochemical performance.2:Three-dimensional（3D）porous Ni O-Ni Co₂O₄film on Ni foam substrate was fabricated through the electrostatic spray deposition（ESD）technique followed by annealing in Ar atmosphere for lithium ion battery anodes.The Ni O-Ni Co₂O₄electrode as a binder-free anode exhibits stable cycling performance with a reversible capacity of over 1466 m Ah/g after 100cycles at a current density of 400 m A/g.The superior lithium storage performance of the Ni O-Ni Co₂O₄electrode is attributed to the unique porous Ni O-Ni Co₂O₄structures directly deposited on Ni foam,which could provide more effective void space for the volume change,make the electrolyte fully contact the electrode,and improve the electron transport.3:Porous Ni-Mn-oxide film on Ni foam was designed through electrostatic spray deposition（ESD）and subsequently calcination under Argon atmosphere.The porous Ni-Mn-oxide architecture was composed of Mn₂O₃and Ni Mn O₃composite structure.When unitized as lithium-ion battery（LIB）anode,the Ni-Mn-oxide electrode demonstrates superior cycleability（902 m Ah/g after 100 cycles）,fully demonstrating the excellent electrochemical performance.The unique 3D porous structure of the porous nickel-manganese oxide film on the surface of the foamed nickel provides sufficient buffer space for the volume change caused by the insertion and extraction of lithium ions..