Investigation of electrode materials with 3 DOM structures

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

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

Applications of Li-ion batteries

Lithium ions intercalation and de-intercalation process

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

What is 3 DOM? 3 DOM 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 3 DOM structure

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

Objects of the project Preparation of the colloidal crystal templates used for the generation of 3 DOM 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 asprepared 3 DOM electrode materials.

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

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

Loading technique Methods to load the fluid precursors n n n n n 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,

Template removal technique Polymer templates n n 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.

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

Some of preliminary results J. of Electro. Soc. , 152 10 A 1989 2005

Li. Co. O 2 with 3 DOM structures Co 3 O 4 impurity exists-high surface area

Optimize synthesis conditions 1. 3 Li composition • minimum impurity • maintain the structure

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

Electrochemistry • Bulk Li. Co. O 2 • Better charge/discharge cycleabilities • Poor rate capacity • 3 DOM Li. Co. O 2 • Relatively poor cycleabilities • Capacity still remains at very high charge/discharge rate

Reference Ergang, N. S. ; Lytle, J. C. ; Yan, H. ; Stein, A. ; “The Effect of a Macropore Structure on Cycling Rates of Li. Co. O 2” J. Electrochem. Soc. 2005, 152, A 1989 -A 1995. 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, 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, A 1102 -A 1107.