“in-operando” neutron scattering studies on commercial li

Technische Universität München

A. Senyshyn, M.J. Mühlbauer, O. Dolotko, H. Ehrenberg

Forschungsneutronenquelle

Heinz Maier-Leibnitz (FRMII)

A. Senyshyn, M.J. Mühlbauer, O. Dolotko, H. Ehrenberg

“In-operando” neutron scattering studies on

commercial Li-ion batteries

“In-operando” neutron scattering studies on

commercial Li-ion batteries

„Energy Challenges

Germany 2050“ 28 June 2012 1




4C Market

Electromobility

Local storage of renewable energy

Why lithium?


Germany 2050“ 28 June 2012 2




1. Specific energy – amount of energy per unit mass (C/3, 150Wh/kg);

2. Energy density – amount of energy per unit volume (C/3, 230Wh/l);

2. Calender life – (10 15 years);

3. Operating temperature range – (-40oC 50oC) ;

4. Selling price – (150$/kWh);

5. Safety – serious hazards have been reported.

Major challenges of Li-ion battery technology

Ways to improve: 1. Use of new materials;

2. Optimisation of the battery design

and processing;

3. Understanding of the fatigue

processes;

4. Enhancement of thermal stability;

Studies of the battery „in-operando“.

New non-destructive technique of studies is needed


Germany 2050“ 28 June 2012 3




Advantages of neutron scattering

The energy of thermal neutrons is

in range of meV

Neutrons are highly penetrating

into the matter

Neutrons interact with nucleous.

The wavelength of thermal

neutrons is similar to interatomic

spacings.

Neutrons weakly perturb the

experimental system, i.e. non-

destructive.

Studies of bulk processes under

realistic conditions (in complex

environments).

Neutrons can localize light atoms

(e.g. hydrogen, lithium) in the

presence of heavier ones and to

distinguish neighboring elements

from Periodic Table and isotopes.

Details of the crystal structure.


Germany 2050“ 28 June 2012 4




l

PSD collimated

neutron beam

L

sample pinhole

diaphragm

D n

Radiography: a principle (µm resolution)

© F. Piegsa, PSI


Germany 2050“ 28 June 2012 5




ANTARES - Neutron radiography and tomography

Cylindrical cells (18650-type, 2600 mAh, 3.0-

4.2 V window); Electrodes: LiCoO2, graphite

Collimation ratio L/D=800,

Field of view 100x100 mm2 ~ 100 µm pixel resolution


Germany 2050“ 28 June 2012 6




Tomography: a principle

Inverse Radon transformation;

filtered back projection algorithm;

number of projections 600;

Assignment of Absorption Levels

to a chosen color scheme


Germany 2050“ 28 June 2012 7




Tomography reconstruction on 18650-type battery

Photo 3D model Sketch


Germany 2050“ 28 June 2012 8




Tomography reconstruction on 18650-type battery

Polychromatic beam Monochromatic beam*

*=1.5482 Å


Germany 2050“ 28 June 2012 9




Single crystal

Polycrystal

Diffraction from crystalline materials (pm resolution) High resolution neutron powder

diffractometer SPODI at FRM-II

Transmission mode, Take-off 155o


Germany 2050“ 28 June 2012 10




© R. Dinnebier, MPI FKF


Germany 2050“ 28 June 2012 11




20

40

60

80

100

20 40 60 80 100 120 140-12

0

12

observed

calculated

difference

Bragg position

6)5)4) 3)2)

2 (degs.)

No

rma

lise

d in

ten

sity (

%)

1)

"fresh" Li-ion battery

(charged to 4.10V)

=1.5482(1) Е

LiCoO2 (1) Cu (2) Fe (3)

LiC12 (4) LiC6 (5)

Al (6)

Rietveld refinement of typical diffraction pattern

for 18650 Li-ion battery Beam dimensions:

40x15 mm2

Profile function:

Pseudo-Voight (TCH)

Contributions

- Cathode material LiCoO2;

- Anode material (graphite

and Li-intercalated carbons);

- Steel housing + centre pin;

- Copper and aluminum

current collectors;

A. Senyshyn et al., J. Power Sources 203 (2012)

126-129.


Germany 2050“ 28 June 2012 12




Fatigue of battery: introduction Two batches of Li-ion cells purposefully cycled (CCCV, 1C) at 25oC

and 50oC for 200, 400, 600, 800 and 1000 times

0 200 400 600 800 1000 1200 14001900

2000

2100

2200

2300

2400

2500

2600

21

.9 %

cycled at 25oC

cycled at 50oCD

ischa

rge

capa

city, m

Ah

Cycles number12

.8 %


Germany 2050“ 28 June 2012 13




Fatigue of battery: crystal structure

Effect on Li-concentration cathode anode

0 200 400 600 800 1000 1200 140030

40

50

70

80

90

100

~2

1.0

%

21

.0 %

25oC

50oC

25oC

50oC

discharge

Li occup

atio

n in

LiC

oO

2, %

Cycle number

charge

10

.6 %

0 200 400 600 800 1000 1200 140070

75

80

85

90

95

100

cycled at 25oC

cycled at 50oC

Re

lative

Li a

mm

ou

nt in

an

od

e, %

cycles number

15

.7 %

26

.8 %

By the fatigue introduced the system looses free (transport) lithium;

Lithium loss correlate to the reduction of discharge capacity;

Possible reasons: Li-plating (dendrite growth), microcracks formation in

electrodes; oxidation processes and phase transformations; SEI

growth/electrolyte decomposition


Germany 2050“ 28 June 2012 14




Evolution of diffraction data vs.

Electrochemical treatment (Cathode, SPODI, =2.536 Å)

14.05

14.10

14.15

14.20

14.25

14.30

14.35

14.40

14.45

3.0 3.2 3.4 3.6 3.8 4.0 4.2

2.808

2.809

2.810

2.811

2.812

2.813

2.814

2.815

2.816

La

ttic

e p

ara

me

ter

c, A

La

ttic

e p

ara

me

ter

a, A

Cell potential, V


Germany 2050“ 28 June 2012 15




Evolution of diffraction data vs.

Electrochemical treatment (Anode, SPODI, =2.536 Å)


Germany 2050“ 28 June 2012 16


Phase diagram of Li-intercalated carbons

0.0 0.1 0.2 0.3 0.4 0.5

1.68

1.70

1.72

1.74

1.76

0.1 0.2 0.3 0.4 0.5

1.68

1.70

1.72

1.74

1.76



0.0 0.1 0.2 0.3 0.4 0.51.68

1.69

1.70

1.71

1.72

1.73

1.74

1.75

1.76

1.77

0.0 0.1 0.2 0.3 0.4 0.5

1.69

1.70

1.71

1.72

1.73

1.74

1.75

1.76

1.77

discharge

charge

J.R. Dahn, Phase diagram of LixC6, Phys. Rev. B

44(17) 9170-9177 (1991).

T. Ohzuku, Y. Iwakoshi, K. Sawai, Formation of

Lithium-Graphite Intercalation Compounds in

Nonaqueous Electrolytes and Their Application

as a Negative Electrode for a Lithium Ion

(Shuttlecock) Cell , J. Electrochem. Soc., 140(9)

2490-2498 (1993).


Germany 2050“ 28 June 2012 17

“in-operando” neutron scattering studies on commercial li

Documents