work package 1: advanced batteries and battery materials · battery work package 1: advanced...
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Battery
Work Package 1: Advanced batteries and battery materials
WP Leader: Prof. Petr Novák, PSI WP1.1: Prof. Maksym V. Kovalenko, ETH Zürich & EMPA WP1.2: Dr. Claire Villevieille, PSI WP1.3: Prof. Katharina Fromm, University of Fribourg
WP1 structure as of 2014
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WP1.1 Li-ion batteries Prof. Maksym
Kovalenko (ETHZ and EMPA)
WP1.2 Na-ion batteries
Dr. Claire Villevieille (PSI)
WP1.3 Post Li-ion batteries
Prof. Katharina Fromm
(Univ. Fribourg)
Optimized WP1 2015
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Three different groups expert in: • Synthesis of electroactive materials • Characterizations of those new materials • Electrochemical analysis of new type of electrodes • Understanding of reaction mechanisms
WP1.1 Kovalenko
WP1.3 Fromm
WP1.2 Villevieille
Synthesis/coating specialists
Electrochemistry specialist
TARGET Better batteries
(Li/Na/Mg)
Common approach for batteries
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Synthesis of anode materials done by Kovalenko’s group (ETHZ & EMPA) Synthesis of cathode materials done by Fromm’s group (Uni Fribourg) Improvement of electroactive materials by Fromm’s group (Uni Fribourg)
• Core-shell synthesis • Special carbon coating • Voids etc.,
Rough electrochemical screening done by Kovalenko and Fromm’s groups In situ/operando electrochemical analysis done by Villevieille’s group (PSI) Advanced electrochemical tests done by Villevieille’s group (PSI) Demonstration of full-cell batteries done by Villevieille’s group (PSI)
New synergetic approaches for Li/Na batteries
Battery
Na-ion Batteries – New Challenges
Joint work between Prof. K. Fromm (University Fribourg), Prof. M. Kovalenko (ETHZ & EMPA), Dr. C. Villevieille (PSI), and co-workers
Li-ion or Na-ion?
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Na+ Li+
Properties Lithium Sodium Ionic radius (Å) 0.69 0.98
Molecular weight (g mol-1) 6.94 22.99 Potential vs. S.H.E. (V) -3.045 -2.714
Theoretical capacity (mAh g-1) 3861 1165
Commodities and Statistics. MineralsUK – British Geological Survey Center
Does size matter?
Li- and Na-ion facts
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Na+ Li+
Property Lithium Sodium Crustal abundance (ppm) 20 23600
Cost (USD/t) 24000 500 Anode Current Collector Cu Al BGS Supply risk index*
(1 = very low; 10 = very high) 6.7 -
Property Lithium Sodium Ionic radius (Å) 0.69 0.98
Molar mass (g mol-1) 6.94 22.99 Voltage vs. S.H.E. (V) -3.045 -2.714
Theo. Capacity (mAh g-1) 3861 1165
Commodities and Statistics. MineralsUK – British Geological Survey Center
*British Geological Society Supply Risk Index: Factors considered include scarcity, production concentration, reserve distribution, recyclability, substitutability, political stability
• Electrode engineering
• Electrodes selection
• Negative electrodes based on alloy materials
• Sn-based
• Positive electrodes based on oxides
• NaxCoO2
• Full-cells
• NaxCoO2 vs CoSn2
Outline
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Standard electrode formulation 80% active material, 10% conductive additive (Super P), 10% poly(vinylidene) difluoride (PVDF) binder
Differences Li-ion / Na-ion batteries
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Sn electrode (PVDF binder) Sn electrode (CMC binder)
Know-how of LIBs cannot be applied to NIBs
Standard electrolyte formulation For Li-ion batteries : 1 M LiPF6 in ethylene carbonate (EC): dimethyl carbonate (DMC) 1:1 For Na-ion batteries: 1 M NaPF6 in EC:DMC 1:1 Not soluble
Differences Li-ion / Na-ion batteries
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In literature: 1 M NaClO4 in propylene carbonate (PC) with/without fluoroethylene carbonate (FEC)
What is the consequence on the electrodes’ interface of NIBs??
Post mortem XPS
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1 M NaClO4 in PC without additive
Inte
nsity
[a.u
.]
Binding Energy [eV]
692 688 684
NaF
PVDF CF 2
Binding Energy [eV]
Inte
nsity
[a.u
.]
692 688 684
PVDF CF 2
NaF CFx
1 M NaClO4 in PC + 5% FEC
Pristine
0.55V
0.3V
5mV
0.75V
- PVDF contribution
- NaF formation
- NaF
- Thick SEI - PVDF decomposition
- NaF decreased - PVDF decomposition
- NaF (FEC decomp.) - CFx (x>2)
- NaF (FEC decomp.) - CFx (x>2)
- NaF (FEC decomp.) - CFx (x>2)
- NaF (FEC decomp.) - CFx (x>2)
PVDF decomposes in NIBs, FEC prevents it
Bulk reaction mechanism of Sn
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Sn
NaSnx
NaSn
Na15Sn4
Na9Sn4
56% expansion (NaSn)
420% expansion (Na15Sn4)
252% expansion (Na9Sn4)
No expansion (Sn)
Similar results with and without FEC
????
Inten
sity [
a.u]
Tremendous Volume Expansion
Volume expansion problem
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Underlying Problem:
Pulverisation of Electrode
Loss of electronic contact
Dead weight material
Alternative Alloy materials such as MSn2
Buffer volume changes by alloying active metal with inactive metal (Sn) (M = Co, Fe, Mn) Na15Sn4 alloy Don’t alloy with Na
MSn2 family: synthesis & properties
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Synthesis performed by ball-milling Wide particle size distribution Small particles size (<μm)
2μm
+ Fast synthesis way + Transferable to industry + Single phase detected by XRD - Wide particles size distribution
Electrochemistry of MSn2
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FeSn2
MnSn2
CoSn2
Constant increase of the specific charge Possible “activation” mechanism?
Sodiation Desodiation
Electrochemistry of MSn2
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1st cycle
20th cycle
Visible differences during 1st sodiation Almost no difference in desodiation ?
Is the transition metal extruded and inactive after 1st sodiation?
Why is there still differences in the 20th sodiation
To be continued….
Electrochemistry of nanomaterials
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Excellent performance for Na-ion anode
material
Kovalenko et al., Nano Letters 2014, 14, 1255-1262
Sb
Na3Sb (ΔV≈400%)
+Na
Apply the same concept to alloy materials of MSn2 family
Electrochemistry of CoSn2/FeSn2
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FeSn2
CoSn2
Bulk Increases of specific charge Nano Low specific charge
Preliminary conclusions on Nano
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Synthesis of Sn-based materials in nanoshape successful Specific charge low with a strong fading in NIBs but not in LIBs Is there a surface layer that hinders the cycling of Na-ion batteries?
Preliminary results on yolk-shell
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Almost no specific charge Is the coating too thick for Na/Li diffusion? Improvement in progress…to be continued
Conclusion of negative electrodes
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Engineering of the Na-ion batteries need to be improved • Binder • Electrolyte
Successful syntheses of Sn-based materials by ball-milling
• FeSn2 • MnSn2 • CoSn2
Specific charge above 300 mAh/g (better than hard carbon ca.170 mAh/g) Investigation of the role of the transition metal (XRD, XAS, etc…) Problem of volume change Going to nanoparticles Development of yolk-shell coating to prevent volume change
Primary target for the next months…
Specific energy = Specific charge * Voltage
Target full-cell Energy density
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Poten
tial [V
] vs.
Na+ /N
a Positive Negative
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Na0.74CoO2
Cathode materials for Na-ion batteries
Selection of 2 cathodes described in literature
Na3V2(PO4)3
Solid state synthesis Big particles size Reaction mechanisms based on insertion reaction
2μm
• Single phase • High crystallinity
• At least 2 impurities detected • High crystallinity
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Cathode materials for Na-ion batteries
• High specific charge for Na-ion cathode • Large potential window
Na0.74CoO2
Na3V2(PO4)3
• Narrow potential window at high potential • Impurities lowering the specific charge
Concept of Na-ion full-cells
28 Yabuuchi et al. Chem. Rev., 2014, 114, 11636-11682
Na-ion extracted on the cathode ~ Na-ion reacting at the anode Need «equivalent» specific charge on both side of the electrode Optimization required to solve «extra consumption» of Na ion (SEI, moisture, etc….) CoSn2
NaCoO2 Na3V2(PO4)3
+
Na-ion full-cells
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Na3V2(PO4)3 vs. CoSn2 Na0.74CoO2 vs. CoSn2
Concept is working
Improvement needed: • Balancing • Potential window • Electrode formulation • Electrolyte • Etc…
Conclusion and outlook
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Engineering of the Na-ion batteries needs to be improved
Successful syntheses of Sn-based materials Specific charge above 300 mAh/g for anode materials Role of the transition metal under investigation (XRD, XAS) Need to understand why nano is not properly working in Na Surface? Cathode development in progress (specific charge rather low ca. 100 mAh/g) Full-cells prototype demonstrated 100 mAh/g without any engineering
SNF Synergia application was submitted to strengthen the link between groups in work package 1