Nanoscale Interface Control of High-Quality Electrode Materials for Li-Ion Battery and Fuel Cell Byungwoo Park Department of Materials Science and Engineering http://ep.snu.ac.kr 1
Nanoscale Control for High-Technology Electronics Equipment Mobile Phone PDA Laptop Computer MP3 Player Digital Camera PMP 2
Global Warming TIME (26) 3
Electrode Materials for the 2nd Generation Li-Ion Battery Discharge (Lithiation) e + CATHODE ANODE - Li + e e e e Li + Li + e e e e Li 1-x CoO 2 Electrolyte Carbon - Capacity - Cycle Life - Safety Solution? 4
Mechanisms of Capacity Fading and Safety Cobalt Loss from Li 1-x CoO 2 Structural Instability Co Dissolution (ppm) 8 6 4 2 After one week at 25 C B. Park s Group (SNU) Bare SiO 2 B 2 O 3 TiO 2 Al 2 O 3 ZrO 2 4.4 4.6 4.8 Voltage (V) Y.-M. Chiang s Group (MIT) Oxygen Loss from Li 1-x CoO 2-δ Exothermic Reaction with Electrolyte 2. Oxygen Content (2-δ) 1.9 1.8 1.7..2.4.6.8 1. Lithium Content (1-x) A. Manthiram s Group (Univ. Texas, Austin) http://www.citynews.ca 5
The Effect of Al 2 O 3 Coating in Thin-Film LiCoO 2 Cathodes Y. J. Kim, H. Kim, B. Kim, D. Ahn, J.-G. Lee, T.-J. Kim, D. Son, J. Cho, Y.-W. Kim, and B. Park Chem. Mater. 15, 155 (23). Y. J. Kim, E.-K. Lee, H. Kim, J. Cho, Y. W. Cho, B. Park, S. M. Oh, and J. K. Yoon J. Electrochem. Soc. 151, A163 (24). J. Cho, Y. J. Kim, T.-J. Kim, and B. Park Angew. Chem. Int. Ed. 4, 3367 (21). 6
Capacity Retention of Metal-Oxide-Coated LiCoO 2 18 Li/Metal-Oxide-Coated LiCoO 2 ZrO 2 Discharge Capacity (mah/g) 15 12 SiO 2 Bare B 2 O 3 Al 2 O 3 TiO 2 4.4 V - 2.75 V C rate =.5 C Moderate Metal-Oxide Coating on Cathode Enhanced Capacity Retention by Protection of Surface 2 4 6 Cycle Number J. Cho, Y. J. Kim, T.-J. Kim, and B. Park Angew. Chem. Int. Ed. 4, 3367 (21). 7
Galvanostatic Charge-Discharge Experiments Uncoated LiCoO 2 Thin Film Al 2 O 3 -Coated LiCoO 2 Thin Film 6 6 6 5 Bare LiCoO 2 5 4 3 5 3 nm Coating 5 4 3 Capacity (µah/cm 2 ) 4 3 2 1.2 ma/cm 2 ( 6 C) 2 1 2 4 6 8 1 Discharge Capacity Charge Capacity Capacity (µah/cm 2 ) 4 3 2 1.2 ma/cm 2 ( 6 C) 2 1 2 4 6 8 1 Discharge Capacity Charge Capacity 2 4 6 8 1 Cycle Number The charge capacity (for Li deintercalation) showed faster deterioration than the discharge capacity (for Li intercalation). 2 4 6 8 1 Cycle Number Cell voltage : 4.4 V - 2.75 V Current rates :.1 -.8 ma/cm 2 Half-cells (Li/LiCoO 2 ), 1 M LiPF 6 in EC/DEC At each cutoff step, the voltage was potentiostated until the current decreased to 1%. 8
Al 2 O 3 Coating Layer as a Solid Electrolyte Capacity Retention (%) Initial Discharge Capacity (µah/cm 2 ) 5 45 4 35 3 25 2 1 8 6 4 2 Initial Discharge Capacity Capacity Retention.2 ma/cm 2.4 ma/cm 2 After 1 cycles 4 8 12 3 Al 2 O 3 Thickness (nm) Li + LiPF 6 in EC/DEC Li-Al-O Li 1-x CoO 2 e - e - Pt SiO 2 /Si (1) Li + Oxidation/reduction reaction occurs at the Li-Al-O / LiCoO 2 interface. Composition of Li-Al-O needs to be determined. Liquid Electrolyte Solid Electrolyte Cathode Current Collector Substrate Ex).7Li 2 O-.3Al 2 O 3 : ~1-7 S/cm at 23 C A. M. Glass et al., J. Appl. Phys. (198). 9
Li Diffusivity during Li Deintercalation (Charging) Uncoated LiCoO 2 Thin Film Al 2 O 3 -Coated LiCoO 2 Thin Film Bare LiCoO 2 3 nm-coated LiCoO 2 Lithium Diffusivity (cm 2 /sec) 1-1 1-11 1-12 2 4 6 8 During Li Deintercalation Lithium Diffusivity (cm 2 /sec) 1-1 1-11 1-12 Before Cycling After 2 Cycles After 4 Cycles After 6 Cycles After 8 Cycles 4 2 6 8 3.9 4. 4.1 4.2 4.3 Cell Potential (V) 3.9 4. 4.1 4.2 4.3 Cell Potential (V) Clearly enhanced by 3 nm-thick Al 2 O 3 coating. Maxima at ~4.13 V, corresponding to the monoclinic phase. Two minima at the cell potential, corresponding to the phase transition between a hexagonal and monoclinic phase. 1
Cobalt Dissolution from Thin-Film LiCoO 2 Cathodes 1 ~3 nm Al Liquid 2 O 3 Electrolyte ~3 nm Al 2 O 3 Cobalt Dissolution (ppm) 8 6 4 2 Thin Film LiCoO 2 Li Co O Bare LiCoO 2 Al 2 O 3 -Coated LiCoO 2 ICP-MS after floating for 12 days Al 2 O 3 coating can effectively suppress the Co dissolution 4.2 4.3 4.4 4.5 4.6 4.7 Voltage (V) Y. J. Kim, H. Kim, B. Kim, D. Ahn, J.-G. Lee, T.-J. Kim, D. Son, J. Cho, Y.-W. Kim, and B. Park, Chem. Mater. 15, 155 (23). 11
AlPO 4 -Nanoparticle-Coated LiCoO 2 Cathode Materials J. Cho, Y.-W. Kim, B. Kim, J.-G. Lee, and B. Park Angew. Chem. Int. Ed. 42, 1618 (23). J.-G. Lee, B. Kim, J. Cho, Y.-W. Kim, and B. Park J. Electrochem. Soc. 151, A81 (24). B. Kim, C. Kim, D. Ahn, T. Moon, J. Ahn, Y. Park, and B. Park Electrochem. Solid-State Lett. 1, A32 (27). 12
Breakthrough in the Safety Hazard of Li-Ion Battery Cell Voltage (V) Bare LiCoO 2 14 12 ~5 C 5 1 4 8 3 6 Voltage 2 4 2 Temperature 1 2 4 6 8 1 12 14 16 Time (min) Temperature ( o C) Cell Voltage (V) AlPO 4 -Coated LiCoO 2 14 1 12 8 1 8 Voltage ~6 C 6 6 4 Temperature 4 2 2 2 4 6 8 1 12 14 16 Time (min) Temperature ( o C) Short Circuit & Temperature Uprise Temperature only ~6 C Cell Fired and Exploded Excellent Thermal Stability 13
TEM Image of AlPO 4 Nanoparticle-Coated LiCoO 2 EDS confirms the Al and P components in the nanoscale-coating layer. AlPO 4 nanoparticles (~3 nm) embedded in the coating layer (~15 nm). 14
Charge-Discharge Tests 25 4.6 V Charge Cutoff 4.8 V Charge Cutoff 25 Discharge Capacity (mah/g) 2 15 1 5 1 C Al 2 O 3 -Coated LiCoO 2 AlPO 4 -Coated LiCoO 2 Bare LiCoO 2 Discharge Capacity (mah/g) 2 15 1 5 1 C AlPO 4 -Coated LiCoO 2 Al 2 O 3 -Coated LiCoO 2 5 1 15 2 25 3 35 4 45 5 Cycle Number Bare LiCoO 2 5 1 15 2 25 3 35 4 45 5 Cycle Number AlPO 4 -coated LiCoO 2 is very stable at the high-charged state. J. Cho, T.-G. Kim, C. Kim, J.-G. Lee, Y.-W. Kim, and B. Park J. Power Sources 146, 58 (25). 15
12 V Overcharge Test at 1 C Rate 14 6 Cell Voltage (V) 12 1 8 6 4 2 12 1 8 6 4 2 12 AlPO 4 -Coated LiCoO 2 1 8 6 4 2 Bare LiCoO 2 Voltage Al 2 O 3 -Coated LiCoO 2 Voltage Voltage ~5 C Temperature ~6 C Temperature ~6 C Temperature 5 4 3 2 1 5 4 3 2 1 1 8 6 4 2 Cell Temperature ( C) Short Circuit at 12 V - Direct contact between the anode and cathode as a result of separator shrinkage. - Thermal runaway with exothermic heat release. Bare and Al 2 O 3 -Coated LiCoO 2 - Rapid temperature upsurge above 5 C. - Firing and explosion. AlPO 4 -Coated LiCoO 2 - Temperature increases to only ~6 C. 2 4 6 8 1 Time (min) 16
Spin Coating of AlPO 4 Nanoparticles with Various Nanostructures Glue 4 4 C Annealing AlPO 4 LiCoO 2 Charge Capacity (µah/cm 2 ) 35 3 25 2 15 1 4 µa/cm 2 (= 12 C) 4.4 V 2.75 V 4 µa/cm 2 2.75 V - 4.4 V Amorphous Tridymite Amorphous 5 Bare Cristobalite Pt/TiO 2 SiO 2 Si 2 nm TEM confirms the uniform coating layer on LiCoO 2 thin film. Bare LiCoO 2 2 4 6 8 1 Cycle Number - Cycle-life performances with various nanostructures - Optimum performance with amorphous coating layer 17
Development of High-Efficient Anode Nanomaterials E. Kim, D. Son, T.-G. Kim, J. Cho, B. Park, K.-S. Ryu, and S.-H. Chang Angew. Chem. Int. Ed. 43, 5987 (24). C. Kim, M. Noh, M. Choi, J. Cho, and B. Park Chem. Mater. 17, 3297 (25). T. Moon, C. Kim, S.-T. Hwang, and B. Park Electrochem. Solid-State Lett. 9, A48 (26). 18
Mesoporous Tin Phosphates SnF 2 and H 3 PO 4 dissolved in distilled water + CTAB (CH 3 (CH 2 ) 15 N(CH 3 ) 3 Br) (1) Intensity SnHPO 4 9 C Aging d = 4. ±.2 nm Intensity (arb. unit) (1) Intensity (11) (2) d = 3.5 ±.3 nm 1 2 3 4 5 2θ (degree) 1 2 3 4 5 2θ (degree) Sn 2 P 2 O 7 As Synthesized Mesoporous Tin Phosphate / SnHPO 4 4 C Calcination Mesoporous Tin Phosphate / Sn 2 P 2 O 7 (11) (2) 2 3 4 5 6 Scattering Angle 2θ (degree) E. Kim, D. Son, T.-G. Kim, J. Cho, B. Park, K.-S. Ryu, and S.-H. Chang Angew. Chem. Int. Ed. 43, 5987 (24). 19
Mesoporous Tin Phosphates TEM Image Electrochemical Properties 2.5 2. 3 2 1 5 2 1 1.5 Cell Potential (V) 1..5. 2. 1.5 3 2 1 5 2 1 c-sn 2 P 2 O 7 1. Mesopores.5 mesoporous/sn 2 P 2 O 7. 2 4 6 8 1 12 Capacity (mah/g) Novel Mesoporous/Crystalline Composite: - Highest initial charge capacity (721 mah/g) - Excellent cycling stability (among the tin-based anodes) 2
SnO 2 Nanoparticles: Mechanisms and Synthesis Problems of SnO 2 Electrode Severe capacity loss by volume change between Li x Sn and Sn phases (~3%). Particles become detached and electrically inactive. SnO 2 Nanoparticles: Effective Solution Cell Potential (V) 2.5 2. 1.5 1. Capacity Fading 2 nd Delithiation Irreversible Capacity 1 st Delithiation.5 2 nd 1 st. Lithiation Lithiation 2 4 6 8 1 12 14 16 Capacity (mah/g) Voltage Profile of ~1 μm SnO 2 SnCl 4 TEDA (C 6 H 12 N 2 ) Distilled Water Magnetic Stirring 11 C 2 C ~4 h Autoclave ~3 nm or ~8 nm SnO 2 Nanoparticles T.-J. Kim, D. Son, J. Cho, B. Park, and H. Yang Electrochim. Acta 49, 445 (24). 1 st Lithiation: 8.4Li + SnO 2 2Li 2 O + Li 4.4 Sn ~149 mah/g 1 st Delithiation: 4.4Li + Sn Li 4.4 Sn ~78 mah/g 21
SnO 2 -Nanoparticle Anode with Different Particle Sizes 2.5 SnO 2 (11) 2. 1.5 1. 32121 ~3 nm SnO 2 (11 C) SnO 2 (11) SnO 2 (11) SnO 2 (11) Cell Potential (V).5. 2. 1.5 1. 3 2 1 21 2 3 1 ~8 nm SnO 2 (2 C).5 3 1 2. 5 1 15 2 Capacity (mah/g) C. Kim, M. Noh, M. Choi, J. Cho, and B. Park Chem. Mater. 17, 3297 (25). 1 22
Carbon-Coated SnO 2 Nanoparticles: Synthesis Intensity (arb. unit) Intensity (arb. unit) (11) (11) (2) (111) 2 3 4 5 6 C-coated D Band (disorderd carbon) 69.9% (21) C-coated uncoated Scattering Angle 2θ (degree) 3.1% 1 125 15 175 2 Raman Shift (cm -1 ) (211) (22) G Band (crystalline graphite) Disordered-carbon-coated SnO 2 nanoparticles (2) SnCl 4 5 C Carbonization C-coated uncoated C-coated uncoated Ethylene Glycol (C 2 H 6 O 2 ) Size 8.8 ±.9 nm 13.2 ± 1.1 nm SnO 2 (wt. %) 9 97 C (wt. %) 4.9.61 Glucose (C 6 H 12 O 6 ) 18 C Autoclave Carbon-Coated SnO 2 Nanoparticles Local Strain.59 ±.13%.13 ±.8% H (wt. %).35.74 by ICP 23
Carbon-Coated SnO 2 Nanoparticles 18 Discharge Capacity (mah/g) 16 8 6 4 2 C-coated uncoated carbon 1 2 3 4 5 Cycle Number T. Moon, C. Kim, S.-T. Hwang, and B. Park Electrochem. Solid-State Lett. 9, A48 (26). Most of the nanoparticles are well dispersed. SnO 2 nanoparticles are surrounded by disordered carbon. (graphite-interlayer spacing.35 nm) Capacity contribution of disordered carbon is ~1 mah/g. 24
Nanostructured Pt-FePO 4 Thin-Film Electrodes for Methanol Oxidation B. Lee, C. Kim, Y. Park, T.-G. Kim, and B. Park Electrochem. Solid-State Lett. 9, E27 (26). C. Kim, B. Lee, Y. Park, J. Lee, H. Kim, and B. Park Appl. Phys. Lett. (submitted). 25
Direct Methanol Fuel Cell 1.18 V e - e - H + Methanol + Water H + Oxygen Carbon Dioxide H + Water Anode CH 3 OH + H 2 O CO 2 + 6H + + 6e - E a =.5 V (Methanol Oxidation) Electrolyte Cathode 3/2 O 2 + 6H + + 6e - 3H 2 O E c = 1.23 V (Oxygen Reduction) Goals: Goals: --Catalytic Activity --Stability Nanocomposite Materials 26
Nanostructured Pt-FePO 4 Thin-Film Electrode Co-Sputtering System (a) Fe/Pt =.12 Pt (111) Pt FePO 4 Pt (2) FePO 4 Pt (111) 5 nm (b) Fe/Pt =.27 (111) (2) ITO-Coated Glass FePO 4 Pt (111) (22) (311) Pt (2) Metal/Metal-Phosphate Nanocomposites Control of Nanostructures (111) (22) (2) (311) Pt (111) 5 nm 27
Increased Active Surface Area E (V) vs. SCE -.2..2.4.6.8 Current Density (ma/cm 2 ).3. -.3 I (µa/cm 2 )..4.8 Potential (V) vs. SCE 4-4 FePO 4 Pt-FePO 4 (Fe/Pt =.27) Pt-FePO 4 (Fe/Pt =.12) Pt Cyclic voltammograms in.5 M H 2 SO 4 (-.2 and.8 V at 5 mv/s) Shaded Area: Oxidation of hydrogen adsorbed on Pt 28
Enhanced Methanol Oxidation Current Density (ma/cm 2 ).6.4.2. Pt-FePO 4 (Fe/Pt =.27) Pt-FePO 4 (Fe/Pt =.12) Pt Increased Activity as FePO 4 /Pt Ratio.1.2.3.4 Potential (V) vs. SCE Pt-FePO 4 nanocomposite 4 electrodes: --Higher current density for for methanol oxidation Increased active surface area area of of Pt Pt nanophases Enhanced activity of of Pt Pt by by the the possible ability of of FePO 4 matrix 4 29
Steady-State Activities Current Density (ma/cm 2 ).12.6. Pt-FePO 4 (Fe/Pt =.27) Pt-FePO 4 (Fe/Pt =.12) Pt 1 2 3 Summary Time (sec) Pt-FePO 4 Nanocomposites: 4 --High High steady-state activity --Low Low decay decay rate rate As As the the atomic ratio ratio (Fe/Pt) increases, the the steady-state activity is is enhanced. Effective transfer of of protons Improved CO CO oxidation Electrode Active surface area Current density at.3 V Current density at.3 V at 3 sec Pt-FePO 4 (Fe/Pt =.27) 5.7 cm 2 14 μa/cm 2 53 μa/cm 2 Pt-FePO 4 (Fe/Pt =.12) 3.6 cm 2 7 μa/cm 2 13 μa/cm 2 Pt 2.5 cm 2 35 μa/cm 2 2 μa/cm 2 3
Conclusions Nanoscale Interface Control - Nanostructures? - Compositions? - Mechanisms? http://ep.snu.ac.kr 31
Current and Former Members 32
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Structure of LiCoO 2 C B Li + Co 3+ O 2- Li 1-x CoO 2 for <x<.5 c A C B - Space group: R3m a = 2.81 Å and c = 14.8 Å A a 34
Synthesis/Control of Nanostructures for Desirable Applications Mesoporous Structure Oxide Nanoparticles Metal Nanoparticles Nanowires Nanocomposites Nanoscale Coating 35
Cross-Sectional TEM Co LiCoO 2 Al 2 O 3 2 nm Glue Al 2 nm TEM image shows continuous Al 2 O 3 -coating layer on LiCoO 2 thin film. EDS shows Al components in the coating layer. 36
Sample Preparation Metal-Oxide Coating M(OOC 8 H 15 ) 2 (OC 3 H 7 ) 2 AlPO 4 -Nanoparticle Coating Al(NO 3 ) 3 9H 2 O + (NH 4 ) 2 HPO 4 AlPO 4 -Nanoparticle 4 Solution Isopropanol (Flammable) Distilled Water Mixing with LiCoO 2 Powders (~1 µm in diameter) 2 nm Drying at 13 Cand firing at 7 C for 5 h AlPO 4 -Nanoparticle Coating - Continuous Coating Layer - Easy Control (shape, size, coating thickness) 37
DSC Scans of 4.3 V-Charged Cathodes 2. OCV = 4.3 V Bare LiCoO 2 Heat Flow (W/g) 1.5 1..5 Al 2 O 3 -Coated LiCoO 2 AlPO 4 -Coated LiCoO 2 Bare LiCoO 2 Al 2 O 3 -Coated Onset Temp. ~17 C ~19 C. 12 14 16 18 2 22 24 26 28 Temperature ( C) Exothermic Heat ~65 J/g ~55 J/g AlPO 4 -coating layer effectively retards the initiation of oxygen generation. AlPO 4 -Coated ~23 C ~1 J/g 38
Mesoporous Tin Phosphates The Corresponding d Spacing Reaction Mechanisms Cell Potential (V) d Spacing (nm) 2.5 2. 1.5 1..5 3.8 3.7 3.6 Intensity (arb. unit).7 V 2. 2.2 2.4 2.6 2.8 3. Scattering Angle 2θ (degree) 3.5 4 8 12 16 1.1 V Capacity (mah/g) 12.8 Li + Sn 2 P 2 O 7 2 Li 4.4 Sn + Li 3 PO 4 + LiPO 3 8.8 Li + 2 Sn + Li 3 PO 4 + LiPO 3 The d spacing expands and shrinks with Li alloying/dealloying. The mesopores do not collapse during discharge and charge. 39