Metal oxide based electrode for electrochemical energy storage

1. Metal oxide based electrode for electrochemical energy storage ZeWei Fang 2012/11/23

2. Research Background 1 Research Content 2 Experimental Design 3 Reference 4 Contents

3. 20世纪60-70年代 石油危机！！ 寻找新能源 电压高 干电池：1.5V； 锂原电池：3.9V以上 工作温度范围宽，放电平稳 金属Li很轻 锂离子电池 比能量高，传统锌负极电池的2-5倍 比功率大，可大电流充放电 Hot Tip

4. Electric apparatus Solar power generation electric bicycle Wind power generation communication aerospace electric car Electric battery Stored energy Compact battery upsizing Application of Lithium ion battery Lithium ion battery Development tendency Tradition field

5. Application

6. graphite Si-based composites metal oxide Nitrides LiMxNy Carbon-based Anode of lithium ion battery The most portion

7. Mechanism Iron oxides , such as hematite(Fe2O3)and magnetite(Fe3O4),are attractive anode materials for rechargeable lithium-ion batteries because they can store six and eight Li per formula unit via conversion reactions , resulting in high theoretical capacities of about 1007 mAh·g-1and 926 mAh·g-1，respectively. During the charge/discharge process,Fe2O3-based anodes have the following possible reactions: Fe2O3+0.6Li++0.6e- Li0.6 Fe2O3 (theoretically at 1.1V ）(1) Fe2O3+1.8Li++1.8e- Li 1.8Fe2O3 (theoretically at 0.9V) (2) Fe2O3 + Li+ + e- LixFe2O3 (x=others , at 0.65 V) (3) Among these reactions , Reaction 3 is irreversible because it is usually followed by the decomposition and destruction of the crystal structure . However, in Reaction (2), Li1.8Fe2O3 can further react with Li+ and e-to form Fe and Li2O by following: Li1.8Fe2O3 + 4.2Li+ +4.2 e- 2Fe +3Li2O(4) The total reaction is: Fe2O3+6Li 3Li2O+2Fe Fe3O4+8Li 4Li2O+3Fe

8. Easy change to nanostructure and controllable to synthesis ex Text Extensive resource and environment friendly t Advantage and disadvantage Lower cycle performance advantage disadvantage Higher irreversible Ratio performance remains to be further improved Higher theorical capacity and better rate performance

9. 2 3 1 4 Determining Factor Due to the large volume change of oxide materials during the charge/discharge process , as-formed electrical conductive networks may be destroyed easily metal oxides generally possess low electrical and ion conductivities , which unavoidably results in the low-rate performance. The rate performance of an electrode is determined by the rate of electron and ion transport the cycling stability will be determined by the durability of such transport networks

10. Low dimension Core/shell composites hollow Porous Design and Improvement How Designment

11. Low dimension nanowires high interfacial contact area with the electrolyte and better accommodation of strain and volume change without any structural change or fracture.(cycle performance) it facilitates better electron and lithium ion transport(rate performance) nanorods nanotubes

12. hollow large surface area and the sufficient contact of active material/ electrolyte, and the short diffusion length of Li+. In well-designed nanostructures , not only the Li+ diffusion is much easier, but also the strain associated with Li+ intercalation and the volume expansion of active materials are often better accommodated , resulting in significantly improved electrochemical performance.

13. Porous Structure Porous nanomaterials with large surface will absorb more electrolyte, provide more reaction active sites , even reduce the recombination of electrons and holes , and thus improve the degradation rate.

14. Carbon-metal oxide composites 1.Carbon nanotube-based composites 2. Graphene-based composites 3. Ordered mesoporous carbon-based composites 4.Carbon nanofiber-based composites 5. amorphous carbon-based composites Nanoscaled iron oxide materials and dispersing these nanostructures into carbon matrixes can potentially overcome the problems of their bulk counterparts. The carbon matrix can help enhance the electrical contact of the electrodes and endure the huge stresses occurred during continuous cycling. In addition, the incorporation of Li-active nanoscaled iron oxide into the carbon matrix can reduce the initial irreversible capacity and improve the Columbic efficiency

15. Synthetic route optimum condition Controllable growth mechanism Electrochemical Application Research Content

16. Difficult and Innovation Quantity of aniline Precursor concentration Optimum parameters Carbonization time Hydrolysis Time Carbonization Temperature Hydrolysis Temperature

17. Schedule

18. Experiment Design Preparation Acided-MWCNT Fe3+溶液 N2保护 aniline 常温聚合反应 超声 水浴反应

19. Washing product Water and ethanol Dry in vacuum Repeating for 5times 60℃ Overnight Standing for 30min 3000r/min Extract the supernatant fluid centrifuge 10min Precipitation

20. Carbonization N2保护 热电偶 500ºC carbonization for 3h Product

21. Next step work Electrochemical testing Preparation Characterization galvanostatic charge-discharge cyclic voltammetry electrochemical impedance SEM TEM XRD Thermogravimetry analysis N2 Adsorption analysis Hydrolysis Polymerization Carbonization

22. Innovation 1. A facile , economical, and scalable method for synthesizing 2. A carbon , precursor , aniline, was easily introduced in the middle of an ongoing reaction without any additional separation or purification steps . 3. The synthesized nanocomposite particles have carbon-coated carbon nanotubes-supported Fe3O4 structures that consist of a nanoporous interior with densely packed nanometer subunits on the surface . 4. Due to the characteristic nanostructure and carbon coating , these nanocomposite particles,I think ,exhibit excellent capacity, cycle stability , and rate performance.

23. Thank You !