Investigation of lithium extraction and insertion from LiCoPO4 by in situ X-ray and neutron diffract_图文

Investigation of lithium extraction and insertion from LiCoPO4 by in situ X-ray and neutron diffraction
4th International Forum on Li-Ion Battery Technology & Industrial Development

N.N. Bramnik, K. Nikolowski, A. Senyshyn, D.M. Trots, F. Scheiba, H. Ehrenberg

8-Jul-13

Leibniz-Institut für Festk?rper- & Werkstoffforschung
Leibniz Institute for Solid State and Materials Research

Situated in the heart of Europe (Dresden, Germany)

Leibniz-Institut für Festk?rper- & Werkstoffforschung
Leibniz Institute for Solid State and Materials Research

Leibniz-Institut für Festk?rper- & Werkstoffforschung
Leibniz Institute for Solid State and Materials Research

5 sub-institutes
Institute for Solid State Research Institute for Metallic Materials Institute for Complex Materials

Institute for Integrative Nanosciences
Institute for Theoretical Solid State Physics

Leibniz-Institut für Festk?rper- & Werkstoffforschung
Leibniz Institute for Solid State and Materials Research

Institute for Solid State Research Institute for Metallic Materials Institute for Complex Materials Functional Composite Materials Institute for Integrative Nanosciences Institute for Theoretical Solid State Physics

Leibniz-Institut für Festk?rper- & Werkstoffforschung
Leibniz Institute for Solid State and Materials Research

Functional Composite Materials Lithium Ion Batteries
Cathode materials
? ? ? ? ? LiCoPO4 LixMzMn2-zO4 High voltage materials LiAl – LiZn Al based metallic glases

Intermetallic Anodes

Magnetic Materials

Leibniz-Institut für Festk?rper- & Werkstoffforschung
Leibniz Institute for Solid State and Materials Research

Synchrotron facility DESY (Hamburg, Germany) Used for in-situ X-ray diffraction experiments

Leibniz-Institut für Festk?rper- & Werkstoffforschung
Leibniz Institute for Solid State and Materials Research

Neutron reactor FRM II (Munich, Germany) Used for neutron diffraction and tomography

Leibniz-Institut für Festk?rper- & Werkstoffforschung
Leibniz Institute for Solid State and Materials Research

Institute for Materials Science

Darmstadt

Tight collaboration with the structural research group at the Institute for Materials Science (Darmstadt)

Outline

Introduction
In-situ X-ray Diffraction In-situ Neutron Diffraction and Tomography

Characterization of LiCoPO4
Cycling behavior In-situ X-ray diffraction Neutron diffraction and magnetic measurements Thermal stability

Summary

The ‘black box’ problem

U, I I, U

There is some thing happening. But what?

In-situ probes

Structural probes that can be used in-situ: X-rays Neutrons

In-situ X-ray diffraction

~ 1/γ

High-energy radiation High intensity Low (vertical) divergence

Measurement of ?thick“ samples Time resolved measurements High resolution

In-situ X-ray diffraction
In-situ cell Detector
Linearmotor

Swagelok? housing Primary beam Copper

Aluminium

345 mm

Cathode-mix

Li-Anode

Sealings

Track

Optical ruler

Leak-tight up to 150 charge-discharge cycles Simple design (Swagelok? based)

180°detector Laser assisted optical read out Fast pattern acquisition
Knapp et al. NIM A (2004)

Nikolowski et al., J. Appl. Cryst. 38 (2005) 851

In-situ structural study of Li1-x(Ni0.75Co0.25)O2

charge discharge

Galvanostatic process
I = 0.34 mA C/15 charge

Nikolowski et al., J. Power Sources 2 (2007) 818

discharge

Structural Model for Li-(De)Insertion in Li1-x(Ni0.75Co0.25)O2

Reversible reflex broadening

Reversible reflex splitting

charge-/dischargeprocess
Partially incoherent X-ray domains

Domaines with different Li-content

? ?

particle do not break additional ?internal“ interface formation

Neutron Tomography of commercial ?18650“ Batteries

neutron absorption high low
ANTARES (Senyshyn, Mühlbauer)

In operando Neutron Diffraction and Tomography

Capacity: Size: Voltage:

2600 mAh (? x L) 18.4 mm x 65 mm 3.7 V

aged Δ=20?m

new

battery type “18650”

2θ/°

In operando Neutron Diffraction

discharged

λ = 1.5484(2) ?

charged

?

10 graphite anode LiCoO2 cathode

2θ/°

150 Cu current collector

10

2θ/° ? Crystal structure details ? Microstructure changes ? Rietveld refinement possible

150

Fe (bcc) housing

LiCoPO4 – A high voltage cathode material

LiCoPO4
A high voltage cathode material

LiMPO4 (M=Mn,Fe,Co,Ni) as Cathode Materials
Triphylite LiFePO4 (olivine structure) Heterosite FePO4

5.2 U/V vs. Li/Li+ 4.8 4.4 4.0 3.6

Ni3+/Ni2+

Co3+/Co2+

energy density

+30% Mn3+/Mn2+ Fe3+/Fe2+

LiCoPO4: electrochemical characterization
LiCoPO4
0.12 0.08 0.04 0 reduction 4.5 4.6 4.7 4.8 4.9 5.0 -0.4 3.2 3.4 3.6 2 steps! oxidation 0.4 oxidation 0.2 dQ/dE 0 reduction -0.2

LiFePO4
1st order phase transition LiFePO4 FePO4

dQ/dE

3.8

E, V vs Li/Li+

E, V vs Li/Li+

2 distict oxidation and reduction peaks not completely reversible

single oxidation and reduction peak high reversibility

N. Bramnik et al. J. Solid State Electrochem. 8 (2004) 558

LiCoPO4: electrochemical characterization

0.12 0.08 dQ/dE

1st cycle

4.87 0.04 4.79

Oxidation potentials during 1st cycle strongly differs from subsequent cycles

0
4.71

-0.04
4.5

4.78

4.6

4.7

4.8

4.9

5.0

E, V vs Li/Li+

LiCoPO4 – In situ X-ray diffraction
200 LixCoPO4 <x>~0.4 020 311

discharge
<x>~0

charge
<x>=1.0

5.2

2θ/°

5.6

9.0

2θ/°

10.0

3 phases with broad coexistence ranges
Phase 1: Phase 2: Phase 3: LiCoPO4 LizCoPO4 CoPO4 a=10.201(1)?, a=10.089(1)?, a= 9.581(1)?, b=5.923(1)?, b=5.845(1)?, b=5.789(1)?, c=4.700(1)?, V=284.0(1)?3 c=4.721(1)?, V=278.8(1)?3 c=4.769(1)?, V=264.5(1)?3 Bramnik et al., Chem. Mater. 5 (2007) 357

LiCoPO4 – In situ X-ray diffraction
LiCoPO4
x=1.0 100% ?0.7“ charge

Li0.7CoPO4
?0.2“

CoPO4

discharge

Phase ratio 0%

0

Diffraction pattern no.

40

Bramnik et al., Chem. Mater. 5 (2007) 357

LiCoPO4 – Neutron powder diffraction at RT
LiCoPO4 “Li0.7CoPO4“ “Li0.2CoPO4“

3 phases Slight Li deficiency (xLi=92(1)%) even in pristine material From ICP-OES: 1.003(4):1.000(3):0.998(3) 2nd phase: LizCoPO4 LiCoPO4 : Li0.6CoPO4 : CoPO4 14(3):43(7):43(7)% (w/w) Average calculated Li-content: 0.40 per formular unit z=0.6(1) 60(5)% (w/w)

Li enriched in grain boundaries or Li rich amorphous phase

Second phase is Li0.6CoPO4

CoPO4 is very unstable, may become partially amorphous

LiCoPO4 – Magnetic structure
Magnetic structure refinement of “Li0.2CoPO4” Temperature dependence of the inverse magnetic susceptibility

LiCoPO4 – Magnetic structures of LiCoPO4 and CoPO4

[CoO6] [PO4]

[LiO6]

LiCoPO4 colinear antiferromagnetic

CoPO4
?x=3.1(1)?B, ?z=0.1(7)?B

[VLiO6]

weak ferromagnetic z-component

?x=3.2(1)?B, ?z=0.2(7)?B

Co3+ in CoPO4 must be in high-spin state, as suggested by Zhou et al. (Phys. Rev. B 70 (2004) 235121) instability of the charged state

LiCoPO4 – Thermal instability of delithiated LixCoPO4

LiCoPO4 Intensity, a.u.

LizCoPO4

LiCoPO4 LizCoPO4

?Li0.7CoPO4“

5.4 LiCoPO4 Intensity, a.u.

2θ, ° LizCoPO4 CoPO4

5.7

9.4 LiCoPO4

2θ, ° LizCoPO4

9.7

?Li0.2CoPO4“

CoPO4

5.4

2θ, °

6.0

9.4

2θ, °

9.9 XRD, Mo-Kα1

LiCoPO4 – Thermal instability of delithiated LixCoPO4
T > 200 °C
?Li0.7CoPO4“
LiCoPO4 Intensity, a.u. LizCoPO4 XRD, Mo-Kα1

?Li0.2CoPO4“
Co2P2O7 LiCoPO4 Li CoPO z 4

CoPO4

Co2P2O7

9.2

2θ, °

9.8

9.2

2θ, °

9.8

The crystallization of Co2P2O7 takes place after decomposition of the Li-poor phases and is not accompanied by a decrease of the LiCoPO4 reflections.

LiCoPO4 – Mechanism of LixCoPO4 degradation

T ≤ 200°C: LizCoPO4

zLiCoPO4

+ (1-z)CoPO4 (amorph.)

CoPO4(cryst.) or

CoPO4(amorph.) Co2P2O7(amorph.) + ?O2

T ≥ 200°C: 2CoPO4(amorph.) Co2P2O7(cryst.) + ?O2

can react to CO2 with carbon

LiCoPO4 – Summary

High voltage material (~ 4.7 V)
High theoretical capacity Even lower cost per Wh when compared to LiFePO4

3-phase mechanism on charge/discharge Intermediate Li0.6CoPO4 phase

Rather unstable CoPO4 phase is formed
Co3+ in high-spin configuration Fast capacity fading in cycling test

Significant progress in understanding instabilities

Decomposition may lead to gas evolution Instability of the electrolyte at > 4.7 V
High self-discharge rate

strategies for materials improvement

Acknowledgement

Natalya Bramnik Wolfram Jaegermann Bhuvana Sivakumar J?rg Schneider Kristian Nikolowski Anatoliy Senyshyn Carsten Baehtz (→FZ Dresden-Rossendorf)
Materials Science TU Darmstadt VH-VI-102

Thorsten Buhrmester (→Chemetall)
Michael Knapp (→CELLS, Barcelona) Hartmut Fuess

SPODI@FRM II HRPDHE@PETRA III

Jürgen Eckert

SFB 595 (Electrical Fatigue) SPP 1181 (NanoMat) PAK 177 (High-power batteries)


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