Investigation of electrode materials with 3DOM structures

1. Investigation of electrode materials with 3DOM structures Antony Han Chem 750/7530

2. Outline • Introduction of Lithium-ion batteries and 3DOM materials • Objects of the project • Synthetic technique • Preliminary result on electrode materials with 3DOM structure • Reference

3. Applications of Li-ion batteries

4. Lithium ions intercalation and de-intercalation process

5. Parameters to evaluate electrode materials • First charge/discharge capacities • Irreversible capacities between each charge/discharge cycle • Charge/discharge cycleabilities • Charge/discharge rate capacity • Volumetric charge/discharge capacities • Electrical conductivities

6. What is 3DOM? • 3DOM structure = 3 dimensional ordered macroporous structure • Replicas of their colloidal-crystal templates • Nanometer-sized walls • Well-interconnected close-packed spherical voids with sub-micron diameters • Both cathode and anode materials can be fabricated into 3DOM structure

7. Comparison • Conventional electrode materials • Volumetric capacities • Stable cycleability • 3DOM electrode materials • Solid-state diffusion distance • Electrode–electrolyte interface and Li-ion conduction through the electrolyte.

8. Objects of the project • Preparation of the colloidal crystal templates used for the generation of 3DOM materials; • Methods of integration of the precursors of electrode materials into the colloidal crystal templates; • Methods of removal of the colloidal crystal templates according to the different properties of electrode materials; • Electrochemistry performance of these as-prepared 3DOM electrode materials.

9. Synthesis route Current Opinion in Solid State and Materials Science 5 (2001) 553–564

10. Template • Desired properties • Easier template removal • Possibility of providing additional functionality • Max the precursor loading (easy access of the voids) • Preparation methods • Gravity sedimentation • Centrifugation • Vertical deposition • Templated deposition • Electrophoresis • Patterning • Controlled drying

11. Loading technique • Methods to load the fluid precursors • Sol-gel chemistry • Polymerization • Salt-precipitation and chemical conversion • Chemical vapour deposition (CVD) • Spraying techniques • Nanocrystal deposition and sintering • Oxide and salt reduction • Electrodeposition • Electroless deposition,

12. Template removal technique • Polymer templates • Calcination simultaneously with conversion of the precursor to a solid in the desired phase. • If the solidification is feasible at low temperatures, spheres can also be extracted with appropriate solvents, such as toluene or tetrahydrofuran (THF)/acetone mixtures. • Silica sphere templates are removed by dissolution in aqueous HF solutions.

13. Characterization • Powder X-ray diffractometer (PXRD) • Scanning electron microscope (SEM) • Brunauer-Emmett-Teller (BET) • Energy dispersive spectroscopy (EDS) • Electrochemical characterization (coin cell type batteries)

14. Some of preliminary results J. of Electro. Soc., 152 10 A1989 2005

15. LiCoO2 with 3DOM structures Co3O4 impurity exists-high surface area

16. Optimize synthesis conditions • 1.3 Li composition • minimum impurity • maintain the structure

17. Size control • PEG doped • Grain size still grew • Pt doped • Much smaller size

18. Electrochemistry • Bulk LiCoO2 • Better charge/discharge cycleabilities • Poor rate capacity • 3DOM LiCoO2 • Relatively poor cycleabilities • Capacity still remains at very high charge/discharge rate

19. Reference • Ergang, N. S.; Lytle, J. C.; Yan, H.; Stein, A.; “The Effect of a Macropore Structure on Cycling Rates of LiCoO2” J. Electrochem. Soc. 2005, 152, A1989-A1995. • Lee, K. T.; Lytle, J. C.; Ergang, N. S.; Oh, S. M.; Stein, A.; “Synthesis and Rate Performance of Monolithic Macroporous Carbon Electrodes for Lithium Secondary Batteries”, Adv. Funct. Mater. 2005, 15, 547-556. • Lytle, J. C.; Yan, H.; Ergang, N. S.; Smyrl, W. H.; Stein, A.; “Structural and electrochemical properties of three-dimensionally ordered macroporous tin(IV) oxide films”, J. Mater. Chem. 2004, 14, 1616-1622. • Yan, H.; Sokolov, S.; Lytle, J. C.; Stein, A.; Zhang, F.; Smyrl, W. H.; "Colloidal-Crystal-Templated Synthesis of Ordered Macroporous Electrode Materials for Lithium Secondary Batteries", J. Electrochem. Soc. 2003, 150, A1102-A1107.