Study On The Controllable Preparation, Microstructure And Lithium Storage Performance Of Manganese-based Bimetallic Oxides

The demand for clean energy is increasing due to the serious environmental pollution caused by traditional energy sources.Lithium ion batteries?LIBs?,as one of green energy storage devices,have attracted widespread attention due to their environmental protection.The anode materials of LIBs are directly related to their electrochemical performance.However,the low theoretical specific capacity and small charge-discharge rate of the anode material in conventional commercial LIBs seriously limits its applications.Metal oxides have been widely investigated as anode materials for LIBs due to their high specific capacity,environmental friendliness,low cost and safety.However,the applications of LIBs in the charge-discharge process are severely limited by the volume expansion and poor cycling performance.Thus,the construction of high performance metal oxide anode materials has an important influence on LIBs.In this paper,the preparation,microstructure,electrochemical properties and lithium storage mechanism of ZnMn₂O₄ and ZnMn₂O₄/rGO micro-nano structures are systematically investigated.?1?The ZnMn₂O₄ with different morphologies were synthesized by solvothermal method under different solvent compositions.The effects of morphology on electrochemical properties were systematically investigated.When tesed as anode materials for LIBs,the ZnMn₂O₄ hollow spheres electrode has optimum cycle performance and rate performance.The excellent performance of ZnMn₂O₄ hollow spheres is attributed to the hollow structure.On the one hand,its porous structure and large specific surface area can not only contact with active material and electrolytes,but also adapt to the volume change during the repeated Li⁺insertion and extraction,which can improve the cycle stability.On the other hand,it can provide a short path for Li⁺and e^-diffusion to obtain excellent rate performance.?2?ZnMn₂O₄ nano-peanuts were successfully prepared by solvothermal under the condition of excessive cetyltrimethylammonium bromide.When tested as anode materials for LIBs,the as-synthesized ZnMn₂O₄ exhibits novel interconnected mesoporous hierarchical architecture,which possesses three advantages:special mesoporous structure,high specific surface and interconnected walls.On one hand,the interconnected structure can provide sufficient surface reaction sites to fully contact Li⁺with the electrolyte and improve Li⁺diffusion and electron transfer;On the other hand,the mesoporous hierarchical networks can buffer the volume change,accommodate or alleviate the strain during charge-discharge process,thus enhancing the conductivity and stability of the electrodes.?3?ZnMn₂O₄/rGO nanocomposites with three-dimensional network structured were fabricated by directionally adhering ZnMn₂O₄ nanoparticles on the surface of graphene oxide.When used as anode materials,the ZnMn₂O₄/rGO material shows superior cycling stability and rate capability at high current density.The excellent electrochemical properites are due to the synergistic effects of rGO and ZnMn₂O₄.ZnMn₂O₄ nanoparticles can adhere on the surface of rGO,and the attached ZnMn₂O₄ nanoparticles can effectively avoid the pile-up of adjacent rGO,which can provide enough space to buffer the volume expansion of ZnMn₂O₄ nanoparticles.Furthermore,rGO has good electrical conductivity,which can accelerate the diffusion of ions and electrons in the electrode and reduce the total resistance of the battery.