The Preparation And Modification Of High Capacity Transition Metal Oxide ZnMnO₃ Anode Materials And Their Lithium Storage Performance

Due to the special lithium storage mechanism,transition metal oxides have higher theoretical specific capacity.ZnMnO₃ has caused wide public concern for abundant resources,low-cost price,no pollution,and high capacity.However,as anode materials used in lithium-ion batteries,ZnMnO₃ materials show some inherent drawbacks,such as low conductivity,large irreversible capacity,high-speed rate of capacity fading.This thesis modifies ZnMnO₃materials by building special structure and morphology,compositing with good electrical conductivity of carbon materials and introducing new metal elements Ni.The porous ZnMnO₃ yolk–shell microspheres were prepared by soft template method combining with subsequent heat treatment,which composed of nano-sized primary particles interconnected to form secondary micro-sized spheres,and use as high performance anodes.The test results show that with the special structure of ZnMnO₃ microsphere has good cycle stability,which can be attributed to the structure of the special yolk-shell material.According to the type crystal structure evolution and the element valence change of the porous ZnMnO₃ yolk–shell microspheres in the process of charging and discharging,the transformation mechanism in the process of charging and discharging can be expressed,which suggests that the capacity of ZnMnO₃anode is supposed to be contributed by the oxidation/reduction between Mn?IV?and metallic Mn,while the material elements Zn no valence state change.This indicates that not all zinc-containing compound cathode materials will necessarily generate li-zn alloy during the charging and discharging process.Meanwhile,this also provides a new view for the research on the related reaction mechanism of lithium-ion batteries.The ZnMnO₃/C composite nanofibers were prepared by electrostatic spinning method and subsequent annealing,and used as high performance anodes in lithium-ion batteries.The test results showed that ZnMnO₃ materials with this special structure and morphology exhibited good electrochemical properties,which are mainly thanks to the special structure and morphology that are in favor of improving diffusion rate of Li⁺and increasing the reaction sites for lithium intercalation/deintercalation.Simultaneously,the introduction of carbon element enhanced the electrical conductivity of the material,which reflected excellent cycle stability.The new type of multicomponent transition metal oxides ZnNi_xMn_1-xO₃/C?x=0.1,0.2,0.3?were prepared by electrostatic spinning method and subsequent annealing,and used as high performance anodes in lithium-ion batteries.This work is based on further exploration in the previous work,which is by introducing transition metal element Ni who has multiple valence states to modify the ZnMnO₃/C composite nanofibers.The electrochemical performance tests show increasing initial coulombic efficiency and less irreversible capacity,which are mainly on account of the introduction of the metal element Ni.While the test results also suggest that in spite of the introduction of the metal elements Ni is an effective and efficient way to modify ZnMnO₃ materials,the amount of the introduction of metal elements Ni should be in moderation.