Electrode and Molecular Architectures for Iron based Multivalent Systems

Transcription

1 Electrode and Molecular Architectures for Iron based Multivalent Systems Jagjit Nanda Materials Science and Technology Division 2 nd MRES, North Eastern University August 20 th 2014 Collaborators S. K. Martha, Hui Zhou, Rose Ruther Frank Delnick, Junjie Wang, Paul Braun Sreekanth Pannala, S. Dai and N. J. Dudney

2 Outline Iron based high capacity conversion compound (i) Role of electrode architecture in improving the electrochemical performance and capacity retention (ii) Molecular Architecture : Tuning the ionicity of metal-fluoride bonds Possible application of high capacity conversion and alloy compositions in non-aqueous flow cells Anion radical mediated flow battery system. 2 Managed by UT-Battelle

3 Battery is a complex multiscale device Time scale Years Minutes Milliseconds Microseconds Nanoseconds Femtoseconds Battery Pack and Full Vehicle Full Cell Secondary Particle SEM, SEM-EDAX, XPS, TOF-SIMS, NMR In situ TEM; Raman- FTIR, NMR, Microcalorimetry, OCV, Potential Micro- Raman DSC, ARC PITT / GITT Charge/discharge I/V Profiles, Impedance Spectroscopy, FLIR Mesoscale and thermochemistry (poly-crystal level) Interfacial chem/transport (single crystal level) Electrode potential and OCV (atomic level) 3 Managed by UT-Battelle Length scale (m) Multiscale characterization can be applied to other complex energy systems (PV, Fuel Cells, Catalysis, etc.) Courtesy: Dr. Sreekanth Pannala, ORNL

4 Energy Storage Landscape Where we are and where we need to go! Required Direction 4 Managed by UT-Battelle

5 Need for new materials and electrode design Materials Design High capacity and voltage multivalent red-ox couples Fast transport and diffusion kinetics Structural stability with respect to multivalent red-ox transition Li 2 MnSiO 4 Electrode Design 3D electrode architecture Large surface area Thin film of active materials FeF3 REDUCE TRANSPORT LENGTHS Carbon Coating Nanostructure Nature 2009, 458, 190 Nature NT, 2008, 3, 31 5 Managed by UT-Battelle Chemical Society Reviews, 2009, 38, 226

6 Conversion Mechanism nli + + ne - + Me n+ X Li n X + Me 0 Courtesy J-M- Tarascon et. al Example FeF 3 + Li LiFeF 3 ( V) LiFeF 3 + 2Li Fe 0 + 3LiF ( V) 6 Managed by UT-Battelle

7 Possible High Energy Chemistries 7 Managed by UT-Battelle Material Potential (V) Specific capacity (Ah/kg) Energy (Wh/kg) LiCoO LiMn 2 O FeF FeF FeO x F 2-2x BiF MnF CuF LiFePO LiMnPO LiCoPO LiNiPO Li 2 FeSiO Li 2 MnSiO Li 2 CoSiO Li 2 NiSiO Intrinsic materials issues limit the performance of multivalent conversion electrodes Inherently poor transport kinetics of the material phases Poor reversibility of conversion phases Low electronic and ionic pathways

8 Performance of FeF 3 without Electrode Architecture Capacity (mahg -1 ) Capacity (mahg -1 ) Voltage (V) vs. Li/Li FeF FeF Fe 2+ Fe electron capacity Fe 3+ Fe 2+ 2V 1 Capacity (mahg -1 ) Voltage (V) vs. Li/Li Fe 2+ Fe electron capacity Capacity (mahg -1 ) Managed by UT-Battelle 0 Charge Discharge FeF Cycle number % FeF 3 & FeF % multilayer graphene + 10% binder (PVDF) FeF 2 Charge Discharge Cycle number

9 Approach-I :3D Carbon-fiber Based Architecture: Synthesis and Fabrication Annealing C in Argon Mixing FeF 3 (1-2 µm) FeF 3 (1-2 µm) Graphene (<50 nm) MLG (<50 nm) Drying C in Argon 9 Managed by UT-Battelle S. K. Martha, RSC Adv., 2014, 4, Carbonization (Annealing)

10 Carbon fiber 3D network reduces hysteresis and improves cycling performance Electrode: FeF 3 (75%) Graphene (20%)- Pitch 5% on carbon fibers Capacity (mahg -1 ) 3 Li + FeF 3 3 LiF + Fe Voltage (V) vs. Li/Li Managed by UT-Battelle Fe 3+ Fe 2+ (insertion) 25 ~1V Fe 2+ Fe (conversion) Capacity (mahg -1 ) Charge Discharge C/ Cycle number Electrochemical tests: 2 electrode coin type cell, Li foil as counter electrode Electrolyte: EC:DMC (1:2)/1.2 M LiPF 6 The electrodes are cycled between 1.5V and 4.5V. Electrodes are annealed at 450 o C. Hysteresis is ~ 1 V. S. K. Martha, RSC Adv., 2014, 4,

11 Capacity (mah/g) Cycling at 60 o C : Role of Reaction Kinetics Charge Discharge Voltage (V) vs. Li/Li Cycle number SUR-414A1-FEF3-60C-1-5V Capacity (mah g -1 ) Voltage (V) vs. Li/Li Electrode: FeF 3 75%-Graphene-20%- Pitch 5%- on CF FeF 3-60 o C; Operating voltage V Managed by UT-Battelle Capacity / mah g -1 S. K. Martha, RSC Adv., 2014, 4,

12 Capacity (mah/g) High C-rate for carbon fiber based FeF 3 electrodes 700 C/86 C/ C/10 C/5 Voltage (V) vs. Li/Li C/ Charge Discharge 1C 5C 10C Cycle number C 5C C/2 C/5 C/ C Capacity (mah/g) C/86 C/20 12 Managed by UT-Battelle S. K. Martha, RSC Adv., 2014, 4,

13 Approach II : Soft Matter 3D Template Templating leads to ordered pore volumes which minimize tortuosity and enhance mass transfer throughout the electrode volume 13 Managed by UT-Battelle Paul Braun, Nature Nanotechnology 6, 277 (2011)

14 Bicontinuos architecture for conversion electrodes: Fe 2 O 3 Method : Electrodeposition On Ni inverse opal, the size of nanoparticles is about 30-50nm and the thickness is about 30nm 14 Managed by UT-Battelle Collaboration with Prof. Paul Braun, University of Illinois, Urbana-Champaign

15 Thicker Inverse Opal Fe 2 O 3 Electrode Top Bottom Middle 15 Managed by UT-Battelle Wang, Braun, Hui and Nanda, Small (under review 2014)

16 Good cycle life and capacity utilization demonstrated for 3D Fe 2 O 3 Electrodes Wang, Braun, Hui and Nanda, Small (under review 2014) 16 Managed by UT-Battelle 16

17 Approach III: Molecular architecture Direct Fluorination with F 2 gas in a fluidized bed reactor FBR Tube Goal To convert iron oxide into oxyfluorides Furnace He F 2 Mixing Device Degree of fluorination controlled by (i) Partial pressure of F 2 (ii) Duration of fluorination (iii) Fluorination temperature 17 Managed by UT-Battelle Hui Zhou et al. J.Phys.Chem. Lett Hui Zhou et. al. ACS Nano (submitted) 2014

18 Mechanism of fluorination : Fe 3 O 4 Form of oxyfluoride with further increased T and C F2 At low T, F atoms get adsorbed on the surface and displace the O, get Fe 3 O 4-x F x. Higher T, two F atoms substitutes one O to get the composition of Fe 3 O 4-x F 2x Characterized by x-ray photoelectron spectroscopy, x-ray diffraction and electron microscopy 18 Managed by UT-Battelle Hui Zhou et al. J. Phys. Chem. Lett. 2013, 4, Hui Zhou et. al. ACS Nano (submitted) 2014

19 Improved electrochemical performance on fluorination Higher capacity utilization in oxyfluoride composition (> 2 Li) Increased intercalation potential Redox plateau corresponding of FeOF J. Phys. Chem. Lett. 2013, 4, Managed by UT-Battelle

20 Conclusion : Iron based conversion compounds From a kinetics point of view each reaction event is described in terms of its overpotential. Charge transfer, mass transfer, adsorption, nucleation, growth etc.. The polarization or overpotential can be summed up as η = η electron transport + η mass/ion transport + η intrinsic Approaches (i) carbon fiber or electronic backbone (ii) Particle size, doping Approaches (i) Inverse opal bicontinuous architecture (ii) Temperature (iii) Particle size Specific to material system 20 Managed by UT-Battelle

21 Acknowledgements Office of Vehicle Technologies 21 Managed by UT-Battelle 21