Synthesis Of Multiple Metal Oxides For Lithium Ion Battery And Investigation Of Its Properties

Lithium ion batteries?LIBs?are extensively used in portable electronic devices such as mobile phone,laptop and wearable devices due to their excellent electrochemical performance and less environmental problems.However,with the requirement of high power and rate performance of electronic devices,the traditional LIBs don't meet the demands of these devices owing to their low theoretical capacities,low power densities and short cycling life.It seems urgent to develop LIBs with improved capacity and enhanced rate performance as well as long cycle life.As one of the most important part,the development of new materials used as anode is an effective way to achieve the target.In this thesis,we designed and synthesized novel materials for electrodes based on the multiple metal oxides according to the different theory of lithium storage in metal oxides.Then,we investigated their electrochemical performance and studied the relationship between structure and their properties.The major research contents are as follows:1.Firstly we synthesized FeMnO₃ with Fe and Mn atomic ratio of 1:1by co-precipitation and solid calcination,then we made the FeMnO₃/RGO composite by hydrothermal method.Tests results show that graphene increases the electric conductivity and specific surface area of the composite,improves the diffusivity of lithium ion and anchors FeMnO₃particles on graphene sheets by chemical bonding.The composite obtains specific capacity of 1569.2 and 1155.3 mAh g^-1 at the current density of200 mA g^-1 in the first and 300th cycle,respectively.And it remains the capacity of 851.7 mAh g^-1 at the high rate current density of 3200 mA g^-1.2.Secondly,we used bagasse as the bio-template to synthesize the hierarchical porous Li₄Ti₅O₁₂.SEM images of carbon skeleton of bagasse showed that bagasse had hierarchical porous structure.The synthesized Li₄Ti₅O₁₂ has hierarchical porous structure with the pore size of 5-100 nm through the analysis of BET results.When used as an anode in LIBs,the electrode has a capacity of 170.7 mAh g^-1 at current density of 1 A g^-1.Even at the high current density of 10 A g^-1,it retains a reversible capacity of 91.2 mAh g^-1.It is believed that the hierarchical porous structure alleviates the damage from volume change in the charge/discharge process and increases the specific surface area of Li₄Ti₅O₁₂.