Preparation And Lithium Storage Performance Of Ferrite As Anode Material

Compared with conventional graphitic carbon anode materials for lithium ion batteries, the spinel Fe-based complex oxides have many merits, such as high specific capacity, safety and environmental protection, low cost and so on. This material has a recharging voltage platform of1.5V, can deliver over900mAh/g discharge specific capacity; however this material still have large intial capacity loss、 bad cycling and rate performance when used as anode materials, besides there still have a controversial on their charge/discharge mechanism.Hollow spherical MFe2O4(M=Fe, Zn) have been synthesized by a simple solvothermal process, firstly take Fe3O4for example, we find the reaction time、temperature and the molar ration of raw material have a great impact on their crystallinity、morphology and electrochemical performance, then we conclude the experimental condition of prepareing optimal size of this material according the above experiment. A novel formation mechanism of this hollow sphere material was proposed based on time-dependent experiment. The synthesis mechanism is the coupling mechanism between the chemically induced self-transformation and " Ostwald ripening process".Fe3O4hollow sphere synthesised under optimal experiment condition when used as anode material, a reversible specific capacities of984mAh/g even after70cycles at0.2C,620mAh/g at2C, and460mAh/g at5C, can be delivered, exhibit excellent cycling and rate performance.The EIS test showed that this electrode material has low resitance due to special hollow spherical structure, conductive the process of electrochemical reaction. Lithium insertion mechanisms are also proposed in terms of the charge/discharge curves、CV and ex situ XRD analysis of the electrodes after discharged and charged to certain voltages, and we firstly found the LixFe3O4phase during intial charge process.The content and type of conductive agent have an impact on their electrochemical performance. Take AB for example, appropriate increase the dosage is better able to improve the electrochemical performance of this material, when the dosage of AB is30%, correspond-ing electrode material show the best performance. The binary conductive additives containing granular (AB) and linear (CNTs) can take advantage of these two conductive agents, form an effective three-dimensional conductive network, help to improve the electrochemical performance of this material. Unique hollow ZnFe2O4spheres were prepared according to the above optimal experiment condition, with a spinel structure and500-600nm in diameter. The intial charge/discharge specific capacity are911and1254mAh/g at the current density of0.07C, after30cycles the value are830and841mAh/g respectively, the capacity retention is91.1%, better than the literature values.