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

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

Applications of Li-ion batteries

Lithium ions intercalation and de-intercalation process 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 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

Comparison Conventional electrode materials Volumetric capacities Volumetric capacities Stable cycleability Stable cycleability 3DOM electrode materials 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 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.

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

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

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

Template removal technique Polymer templates Calcination simultaneously with conversion of the precursor to a solid in the desired phase. 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. 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., A

LiCoO 2 with 3DOM 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 LiCoO2 Better charge/discharge cycleabilities Poor rate capacity 3DOM LiCoO 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 LiCoO 2 ” 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, 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, 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.