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

Principle of Na-ion battery

8 Yabuuchi et al. Chem. Rev., 2014, 114, 11636-11682

+

• 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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Which materials?

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Significantly different material’s landscape from that of Li-ion batteries

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?

Yolk shell coating for Li/Na

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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

8/12/2014 31

Polytype, Fribourg

IMERYS for carbonaceous materials

EKZ

Swiss National Science Foundation

Thanks to all of you for your attention