Challenges of Lithium‐Sulfur and Lithium‐Air Cells: Old Chemistry New Advances Old Chemistry, New Advances David X. Ji, Kyu Tae Lee, and LF. Nazar Dept of Chemistry; Waterloo Institute for Sustainable Energy (WISE) D t f Ch i t W t l I tit t f S t i bl E (WISE) Waterloo Institute for Nanotechnology (WIN) University of Waterloo, Ontario, Canada Professor Linda Nazar ([email protected]) IBM‐500 Mesoporous Carbon/Sulfur Composites : Outline OVERVIEW From Li – ion intercalation to integration MESOPOROUS CARBON/SULFUR COMPOSITES Advances with nanostructured materials COMPARISON WITH Li‐AIR The positives (and negatives) CONCLUSIONS Li‐ion Battery at Present: Intercalation Chemistry Recent Intercalation Cathodes: 5 eV a) LiFePO4 Æ FePO4 + 1.0e- + 1.0Li+ Li1-xMO2 + 4 eV Æ Li MO + 0.7e- + 0.7Li+ b) LiMO 2 0.7 2 MLiMO = Ni,2Co, Mn 3 eV 2 eV V - 1 eV graphite 0 Specific p (a) ( ) and (b) ( ) between 0 capacities eVp Li+/Lifor 155 – 185 mA•h/g, energy density limited J. Goodenough, et. al, J. Electrochem Soc.,. 1997 “Green Energy” Needs Large Scale Energy Storage Systems new demands for batteries R Renewables bl Portable High‐Energy Demand Devices larger g scale Electric automotive i‐MIEV LiCoO2 LiCoO2 implemented 1987 1991 LiFePO4 1997 Li[Ni,Co, Mn]O2, LiFePO4 implemented 2007 Future Batteries Q = 180 mAh/g Q = 130 mAh/g Q= n•F Mw• 3.6 36 (mAh/g) Integrated systems Bolivia holds key to electric car future y Sunday, 9 November 2008 Damian Kahya BBC News, Salar de Uyuni, Bolivia Mitsubishi, which plans to release its own electric car soon, estimates that the demand for lithium will outstrip supply in less than 10 years unless new sources are found. Beyond Li‐ion Batteries: Na2FePO4F A2 A1 Na2FeIIPO4F Vol = 852Å3 Fe c a Reduction b Oxidation 3.7% vol change NaFeIIIPO4F Vol = 820Å3 Two – dimensional ion t transport t Low strain material on redox Ellis, Nazar et al., Nature Mater., 2007 Effect of Nano-Sizing 5 b) Voltage (V) 4.5 Nano: 87% capacity av 50x50x500 nm 4 a 3.5 3 2.5 400 nm: 36% capacity 500 nm 2 0 02 0.2 04 0.4 06 0.6 08 0.8 1 x in Li F x in Na xNaFePO xNaFePO44F d) Unusual “solid solution” behavior c Li/Na exchange Æ function of Æ also substituted : (Na,Li)2[Fe, Co]PO4F Stable cycling as LiFePO4 500 nm Ellis, Nazar et al., Chem Mater., in press b 0 Rate Capability 120 4.5 Voltage ((V) Capacity (mAh//g) a 100 4 80 60 40 20 35 3.5 Galvanostatic C/10 0 1 2 3 4 5 6 7 8 9 10 11 12 Cycle Number 3 C/10 2C 2.5 10C 1C 5C 2 c 0 20 40 60 80 Capacity (mAh/g) b 100 120 Interconversion of (Na,Li) FePO4F Li2FeIIPO4F ion red Na2FeIIPO4F ion g xchange g xchange NaLiFeIIPO4F LiI ox NaFeIIIPO4F (Na,Li)FeIIIPO4F LiFeIIIPO4F Multifunctional: use either in Li or Na cell - lower cost, less utilization of Li (electrolyte only) - can be used as a Na-ion Na ion battery for load levelling on large scale Next Generation Battery: Integration Chemistry LiyX: High specific capacity Goal: Higher energy density L Larger scale l 4 eV Low cost Challenges: Kinetics + Safer and environment friendly 3 V 3 eV yLi + X •Mass transport issues 2 eV 2 eV LiyX •Poor reversibility with bulk materials 1 eV 0 eV ‐ •Contact of reactants/products and /p contact with current collector problematic Li+/Li0 Î polarization, poor cycle life l l lf Next Generation Battery: Integration Chemistry LiyX: High specific capacity Examples: 2 Li+//e‐ + O2 ↔ Li2O2 4 eV 4 eV + 3 eV 2 eV yLi + X LiyX ‐ 1 eV 0 eV 16 Li 16 Li+/e‐ + S + S8 ↔ Li ↔ Li2S S Li+/Li0 Offer 3 ‐5 times energy density of traditional intercalation materials (max 220 mAh/g storage capacity ; 100 ‐200 Wh/kg energy density) Comparative Capacities (Beattie et al, JECS 2009) a c Unrealistic! b Batteries and Li‐Air Cells: Simple Comparison ‐ + ((+)) Current collector Current collector Positive electrode (LiMO2) Electrolyte (alkyl carbonates, etc..) Separator (new ceramic blended) Separator (new ceramic blended) Negative electrode (graphite) (‐) Current collector a Li ion Battery Li‐ion Battery S2 + 4 Li+/e‐ ↔ 2Li2S O2 + 4 H+/e‐ ↔ 2H2O O2 + 2 Li+/e‐ ↔ Li2O2 oxygen oxygen fuel c a a Li‐S Battery Li S B tt product: Li2S stored in carbon cathodeb a Li‐Air Battery Li Ai B tt product: Li2O2 stored in carbon cathode FFuel Cell l C ll Product: H2O eliminated Motivation for the Li‐S battery Studied for several decades S di d f ld d 2Li + S ÍÎ Li2S LiMO2/C battery (M = Ni, Mn, Co) Li/S battery OCV: 3.9 V OCV: 2.1 V 440 Wh/kg 180 mAh/g 2500 Wh/kg 1675 mAh/g Electrochemistry of the Sulfur Cathode charge charge I II S8 Li2S8 Li2S4 0% 12.5% 25% discharge III Li2S2 50% Depth of discharge I: conversion of solid sulfur to soluble polysulfides p y II: polysulfides to solid Li2S2 III: solid Li2S2 to solid Li2S Li2S Example of integration chemistry: The Li‐S Battery 2Li + S ÍÎ 2Li + S ÍÎ Li2S theoretical capacity 1675 mAh/g S theoretical capacity 1675 mAh/g typical Li‐S capacity: 500 mAh/g ¾ Low conductivity ¾ capacity fading — i f di lloss of active mass f i Di h Discharge e‐ e‐ Charge Polysulfide shuttle a(Li2S6) + b(Li2S4) Li+ Li+ Lithium Li2S8 Separato or 2 Li+ (Li2S2)/ (Li2S) Li2S inactivated Li2Sx • internal “short circuit” SEI Li2Sx/2 Li‐S Diametric Approaches: Contain or Let Free Catholyte Contained Cathode ‐ + ‐ + a c c a a Insoluble product: Li2S stored in carbon cathode a b b a Soluble product: Li2Sn stored in electrolyte Li‐S Battery for Unmanned Aerial Vehicles a c Zehyr UAV ‐ Qinetiq Powered at night by a SionPower Li‐S cell Record of 82 hours of continuous flight Record of 82 hours of continuous flight b Progress towards improving the sulphur cathode 1) Adding absorbents, mixing porous carbon with sulphur Disordered porous carbon CNT Wang, et al. Carbon 2008, 46, 22 Zheng et al. Electrochimica et al. Electrochimica 2006, 51, 1330 2006, 51, 1330 Î Lack of encapsulation, extensive precipitation of inactive Li2S on absorbent 2) Conducting polymer + sulphur: Low surface area of polymer (low active mass) high polarization – lower working potential p Wang, et al. Adv. Funct. Mat. 2003, 13, 487 3) Innovations re Li negative electrode and electrolyte 3) Innovations re Li negative electrode and electrolyte Solubilization of polysulphides – large electrolyte volume/low volumetric density Sion Power Stabilized capacity > 1000 mA h/g at practical rates rarely achieved Mesoporous Carbon Encapsulation Strategy Porous ‐ structured ‐ controllable Interconnected Channel structure: CMK-3 3D structure: CMK-8 Controllable morphology Symmetry: P6mm Symmetry: Ia3d Tailoring Mesoporous Carbon Hosts Surfactant free Nucleation Cooperative assembly control 100 nm Ji, Nazar Chem. Comm. 4288, (2008) In situ CVD Metal phthalocyanine + SBA-15 I it In situ carbonization b i ti G raphitic carbon Intensity/ A.U. A l holder NiPc 900 o C 20h NiPc 900 o C 3h o N iPc 800 C 20h o Sucrose 900 C 20h 10 15 20 25 30 35 40 2θ/ degree Ji, Nazar et al, Chem. Mater 19, 374 (2007) Lee, Nazar et al., Angew Chemie, 48, 5661, (2009) Encapsulation of Sulphur Sulfur map Empty channels in CMK-3 30 nm Channels filled with S Carbon map CMK‐3—Conductive Nano‐chamber Reactor Assembly for Sulfur Active Mass Increases electrical conductivity Î Intimate 3 Intimate 3‐dimensional dimensional, multi electronic contacts multi electronic contacts Allows egress of electrolyte to aid ionic conductivity through free space in channels C t l Controls sulfur particle size to nano dimensions lf ti l i t di i Inhibits soluble polysulfides from diffusing away from cathode Encapsulation Effect on Electrochemistry All at 168mA/g Mixture: 25°C Partial imbibition With increase in contact in contact temperature: Complete imbibition 9 > doubled > doubled capacity 9 no overcharge, irreversibilityy 9 reduced polarization Conductivity Ensured Electrical Conductivity: CMK‐3: 0.25 S/cm El t i l C d ti it CMK 3 0 25 S/ CMK‐3/S: 0.21 S/cm Ionic Conductivity: • Space is precisely tuned to accommodate swelling of S to Li2S Molten S within pores p Solidificaton ( incomplete Filling) Li2S formation S formation C/S – 70 wt% Mesoporous carbon Characteristics Only very small shuttle process after p equilibration at 55°C Quasi-equilibrium C/10 (0.19 mA/cm-2) Promising rate behavior C/5 (0.36 mA/cm-2) CMK‐3/S/Hydrophilic Polymer Surface Modifier Black: PEG modified Red: no polymer PEG = polyethylene glycol (Mw = 4600) PEG = polyethylene glycol (Mw = 4600) 80% utili. Discharge capacity Surface‐bound PEG provides hydrophilic gradient to partition polysulfide ions For 1000 mAh/g capacity: Î1400 Wh/kg based on total mass Î1400 Wh/kg based on total mass of cathode (S + carbon + binder) Black: PEG modified Red: no polymer Black: Polymer decorated Red: no polymer d l Î2330 Wh/l volumetric for cathode Î 600 – 800 Wh/kg for a full cell D. Ji, K T Lee, L.F. Nazar , Nature Mater., 8, 500 (2009) Role of the Surface Modifier • Increases the absorbing capacity of mesoporous carbon by increasing Increases the absorbing capacity of mesoporous carbon by increasing hydrophilicity • Improves the ionic permeability of the composite • Inhibits Li I hibi Li2S precipitation on external surface of mesoporous carbon S i i i l f f b CMK‐3/S / P‐CMK‐3/S 30th charge 30th charge Summary: Tailored Nanostructured S/C Nanocomposites ÎAchieve stable energy density of a full cell between 550 – 650 Wh/kg ÎFactor of 3‐5 over any conventional Li‐ion cell cell (100‐200 Wh/kg) ÎSion Power: guarantees 350 Wh/kg for 50 cycles for Li‐S cell Î Other cell configurations possible with cathode nanostructure: Î protected metallic Li negative electrodes Î non –Li metal, high capacity negative electrodes Î other surface modifiers and coatings… Î polymer electrolytes…. Mesoporous Materials made Nano Nano‐mesoporous silicate Nano‐mesoporous carbon Ji, Nazar Chem. Comm. 4288, (2008) Bulk‐mesoporous silicate Bulk‐mesoporous carbon Agitation‐Friction Loading of S into Nano CMK‐3 a c b Comparison with Li‐Air Cells Comparison with Li‐Air Cells Li – S vs Li‐air S2 + 4 Li + 4 Li+/e‐ ↔ 2Li ↔ 2Li2S S O2 + 2 Li + 2 Li+/e‐ ↔ Li ↔ Li2O2 O2 c aa Li‐S Battery Rx of S within cathode with Li to f S i hi h d ih i form Li2S in carbon cathode a Li‐Air Battery Rx of external O f l 2 with Li to form h f Li2O2 housed in carbon cathode Role of carbon (or other) framework R l f b b( th ) f k • electronic contact to S/Li2S ‐ opt pore size ~ 4‐15 nm • trap polysulfides Î Li2S ‐ tortuous pathway, sorbtive • current delivery system to O2/Li2O2 ‐ opt pore size? Pore clogging? • plus polymer binder: houses Li2O2 ‐ high pore volume > 2‐3 cc/g • support for CATALYST c Volumetricc energy density (Wh/L) a Gravimetric energy de ensity (Wh/kg g) Comparison of Cell ED (Hypothetical) 1600 1400 1200 1000 800 Calc’s for Li-S based on Li2S cathode Commercialized Graphite Li (130%) Si (9:1) Si (5:5) 600 400 200 0 NMC Li-S Li-air Zn-air 3000 2500 2000 1500 for Li-S for OUR cathode: 1340 Wh/l with Si 1025 Wh/l for 2x Li excess 1000 500 0 b NMC Li-S Li-air Zn-air Commercialized Graphite Li (130%) Si (9:1) Si (5:5) Calculation conditions 1. Cathode Thickness: 100 μm Electrode porosity: 20 vol.% Volume ratio of active material: carbon+binder = 9:1 for LiCoO2 (72 vol.% of LiCoO2 in total) = 8:2 for Li-S & Li-Air (64 vol.% of Li2S or Li2O2 in total) 2 A 2. Anode d Electrode porosity: 20 vol.% Volume ratio of active material: carbon+binder = 9:1 for graphite = 9:1 for Si (9:1) = 5:5 for Si (5:5) 3. Separator 15 μm, Al & Cu current collectors: each 10 μm c Volumetricc energy density (Wh/L) a Gravimetric energy de ensity (Wh/kg g) Comparison of Cell ED (Hypothetical) 1600 Calc for Li-S based on S cathode 1400 1200 1000 800 600 Commercialized Graphite Li Si 400 200 0 NMC Li-S Li-air Zn-air 3000 2500 Anode 2000 Commercialized Graphite Li Si 1500 1000 500 0 b NMC Li-S Li-air Zn-air Conclusions Increasing Complexity of Demands – and Materials SONY Nexelion SONY Nexelion Sn/C/Co nanocomposite Sn/C/Co nanocomposite negative electrode Nano LiFePO4 for the positive AltairNano: nano Li4Ti5O12 for negative AltairNano: nano Li for negative COMMERCIAL LiCoO2 Bulk‐intercalation LiFePO4, Na,LiMPOxFy Li4Ti5O12, TiO2(B) Nano‐intercalation Li/ C‐Sulfur Nano‐integration systems ACADEMIC Lithium – Air Li + O2 ↔ Li2O2 Nano‐meso‐micro Old Ideas Revisited Fire and Brimstone: feu grégeois “A A sulfur sulfur-and-carbon and carbon pitch pitch-based based compound (the exact composition of which was a closely guarded secret and is still a mystery today) - the napalm of the Middle Ages” - was hurled at the Crusaders ~ 1090 to unavail,, leading g to the overtaking g of Jerusalem Sulfur Tower, Jerusalem Feu grégeois tel que décrit dans le manuscrit (Madrid) Funding and Acknowledgments Funding: F di NSERC (Discovery & Strategic) NSERC Canada Research Chair i Solid in lid State M Materials i l GM Canada/USA Toyota USA/Japan Auto211 Research Team Dr. Kyu Tae Lee Dr. Prakash Badi Dr. Katya Pomeransteva Dr. T. N Ramesh Collaborators C ll b t Dr. Neil Coombs (U Toronto) Prf. Gianluigi Botton (U McMaster) NRC F Fuell C Cell ll I Institute i Prf. A. Sazanov (UW, ECE) Prf. M. Wagemaker (TU Delft) P f Thomas Prf. h Bein B (LMU, ( Germany) G ) David Ji Brian Ellis Robert Black Scott Evers Guang He Si Hyoung Oh Rajesh Tripathi Hey Woong Park Guang He