“a tidy laboratory means a lazy chemist” jöns jacob berzelius (swedish chemist ... ·...

“A tidy laboratory means a lazy chemist”

Jöns Jacob Berzelius (Swedish chemist,1779-1848)

Vernachlässigt, vergessen oder unwichtig? -

Inaktivmaterialien für Lithium-Ionen Batterien

B. Streipert, E. Krämer, L. Terborg, V. Kraft, J. Menzel, D. Gallus,

I. Cekic-Laskovic, S. Nowak, T. Placke und M. Winter

6. SEC-Jahrestreffen, 18. - 20. Mai 2016 in Münster (GER)

MEET Battery Research Center,

Institute of Physical Chemistry,

Univ. of Muenster, GER,

martin.winter@uni-muenster.de

& Helmholtz Institute Muenster;

Ionics in Energy Storage,

IEK-12 of Forschungszentrum Juelich

m.winter@fz-juelich.de

Acknowledgements

(General)

Federal Ministry of Economics and Technology (BMWi)

Federal Ministry for the Environment, Nature Conservation & Nuclear Safety (BMU)

Federal Ministry of Education and Research (BMBF)

North-Rhine-Westphalia (NRW)

University of Muenster (WWU)

Helmholtz Association (HGF) and Forschungszentrum Jülich

German Ministry of Education and Research (BMBF)

within the project “Elektrolytlabor 4E”

Cabot Corporation

Acknowledgements

(Specific)

Acknowledgements

None of us is as smart as all of us

Lithium Ion Battery (LIB):

Active and Inactive Materials Have FunctionsActive Anode and Cathode Materials:

Determine capacity and voltage ⇒ energy

Inactive Materials:

Additional mass + volume ⇒ decrease energy

�Electrolyte: “inside” ion conduction, interfaces

�Separator: safety, electrode separation

Inactive cell and electrode components:

�Can/Pouch, Headers, Terminals, Vents, etc.

�Current collector: electron conduction,

connection to the “outside”

�Conductive additive: porosity,

“inside” electron current distribution

�Binder: The “glue”, that holds everything together

�Processing solvents (often disregarded)

From the Beginning: Inactive Materials Determine

Performance: Volta-Pile (1791);

Zn/Cu; NaClaq as Electrolyte

Volta-Cell (open to O2 from air)O2 reacts with Cu forming CuO at the surface.

(Volta-Pile is a kind of Zinc/Air Battery)

Salt water electrolyte @ 1.1 V:

(Anode) Zn � Zn2+ + 2 e-

(Cathode) CuO + 2H+ + 2e- � Cu + H2OCu reacts with O2, regen. CuO

Closed Cell @ 0.76V

(Anode) Zn � Zn2+ + 2e-

(Cathode) 2 H+ + 2e- � H2on inert Cu

Failure mechanism of the Volta-Pile: Drying out, because of H2O evaporation

Technology progress: Pile ⇒ Electrolyte reservoirs or “crown of cups”

Lithium Ion Battery

� Name given by Mr. Keizaburo TOZAWA,

Chief Executive Officer, Sony Energytec, Inc.

� Based on intercalation research in Europe/US.#

� Realized by Sony, 1990/1991*:

I. Use coating technique: audio/video tapes

II. Assemble cell in the discharge state and

then do “formation“

III. “Right“ electrolyte

IV. LiPF6 as HF-Generator for Al passivation#

V. Microporous PE-separator#

� Impresses by an “infinite” variety of materials,

designs and applications

⇒ The established “Allrounder”

#Personal discussions with pioneering scientists

*T. Nagaura, Progress in Batteries & Solar Cells, 10, 218 (1991)

Active and Inactive Materials in LIB

�Parallel electron & lithium ion movement

�Active Materials: Host electrodes

(i) Graphite at the negative electrode

(ii) LiMO2 or LiMPO4 (M = Co, Ni, Mn,

Fe, etc.) at the positive electrode

= Li+-packaging materials

�Per Li+: Two electrode sites are needed

(= double electrode packaging

per charge)

�Inactive Materials necessary for cell

reaction: electrolyte, separator

�and electrode formulation:

additives, binders, collectors

�Inactive materials: Packaging, vents, etc.

*

*Winter, M.; Besenhard, J. O.

Chemie in unserer Zeit 1999, 33, 320-332

18650: The Standard Cylindrical Cell:

Notebook Computers and Power Tools

-

+

65 mm

18.0 mm

Anode

Cathode

Separator

617 mm

60 mm

57 mm

2 x 600 mm = 1200 mm

57 mm

Depending on chemistry and

technology: 30 to >50 grams

Case typically: stainless steel, Al

Mass Distribution in an 18650 cell:

5 Main Groups of Components

18650 cell: 45g;

based on graphite anode

and lithium iron phosphate

(LiFePO4) cathode0.0

7.5

15.0

22.5

30.0

37.5

45.0

10.09

2.002.20

18.46

12.25

Weight / g

Anode Total

Cathode Total

Electrolyte

Separator

Case, Vents, etc.

0.0

7.5

15.0

22.5

30.0

37.5

45.0

10.09

2.002.20

14.22

1.130.812.30

8.15

0.450.45

3.20

Weight / g

Current Collector (Cu)

Binder (Anode)

Conductive Agent (Anode)

Graphite

Current Collector (Al)

Binder (Cathode)

Conductive Agent (Cathode)

LiFePO4

Electrolyte

Separator

Case, Vents, etc.

Mass Distribution in an 18650 cell:

Component Details

18650 cell: 45g;

based on graphite anode

and lithium iron

phosphate

(LiFePO4) cathode

0.0

7.5

15.0

22.5

30.0

37.5

45.0

22.63

8.15

14.22

Weight / g

Cathode Act. Mat.

Anode Act. Mat.

Inactive

Mass Distribution in an 18650 cell:

Summary: Active vs. Inactive Materials

18650 cell: 45g;based on graphite anode and lithium iron phosphate (LiFePO4) cathode

49.71 wt.% Active Mat.

50.29 wt.% Inactive

Mass Distribution in an 18650 cell:

Lithium Ion Battery is Sham

♦Li Active: 0.52g (= 1.16 wt.%): mobile Li from Cathode Material

♦Li Inactive: 0.21g (= 0.27 wt.%): Li Loss from Cathode Material

+ Li in Electrolyte

♦Rest: 44.37g (= 98.57 wt.%)

18650 cell: 45g;

based on graphite anode

and lithium iron phosphate

(LiFePO4) cathode

4.5 Ah 20700 Cylindrical Cell:

Material Costs*

*Source: Total Battery Consulting, 2015

Material costs

on cell level:

Active: 61.8%

Inactive: 38.2%

*Source: Total Battery Consulting, 2015

42 Ah Pouch EV Cell

Material Costs*

Material costs

on cell level:

Active: 55.2%

Inactive: 44.8%

*Source: Total Battery Consulting, 2015

Material costs

on cell level:

Active: 46.9%

Inactive: 53.1%

34 Ah Metal can EV Cell

Material Costs*

5 Ah HEV Cell, 200k Packs per Year

Material Costs*

5-Ah, 500-W HEV Cell

Units Amount $/unit $/cell

kg 0.039 30 1.18

kg 0.022 18 0.40

kg 0.025 20 0.51

m2 0.563 1.8 1.01

kg 0.020 17 0.33

cell 1 1.75 1.75

cell 1 1.0 1.00

6.18

339

12.4

Other

Separator

Copper Foil

Total Materials

NMC/graphite, Metal Can, 12 Million HEV Cells / year

Can, Headers & Terminals

Cathode Active Materials

Anode Active Materials

Electrolyte

Per kWh

Per kW

Material costs

on cell level:

Active: 25.6%

Inactive: 74.4 %

*Source: Total Battery Consulting

216 MWh Plant

The Electrolyte Salt LiPF6:

Unwanted, but Indispensable

• Typical range of LiPF6 in non-aqu. electrolyte is 0.8 to 1.2 molar (10 - 15% by weight)

• 80 – 90 wt. %: organic carbonate solvents + eventual electrolyte additives

• Electrolyte contributes ca. 5 to 10 % to the overall lithium ion battery material costs.

With a mass fraction of <15%, the LiPF6 costs are up to 90% of the electrolyte costs.

• Pros: Instability ⇒ SEI passivation film forming agent

⇒ Al current collector protection (!!!)

• Cons: Instability ⇒ Thermal and chemical (hydrolysis)

� HF and other toxic compounds (fluorophosphates and organophosphates)

� HF promotes cathode dissolution

• LiPF6 is the worst electrolyte salt you can imagine, …

• ...except for all the others.

An Example for an “Inactive”, but not “Passive” Material:

Current Collectors:

Requirements for LIB*

Excellent electronic conductivity: Ag, Cu, Au, Al,…

Low cost: Ag, Cu, Au, Al

Electrochemically stable within the electrode operation potentials:

Processing to thin foils (in the 10-20 µm range) possible √Rel. light weight √Chemically and thermally stable/inert √

X

He

B C N O F Ne

Al Si P S Cl Ar

Fe Co Ni Cu Zn Gaa

Ge As Se Br Kr

Ru Rh Pd Ag Cd In Sn Sb Te I Xe

Os Ir Pt Au Hg Tl Pb Bi Po At Rn

Al alloys with Li at carbon anode potentials

Cu is oxidized at >∼3.5V vs. Li/Li+

(= cathode potentials), surface impurities

⇒ Cu → anode, Al (!) → cathode

(LiPF6 necessary!)

Metals that

alloy with Li

*Considerations are valid for lithium ion cells

with carbonaceous anode and 4-V cathode!

X

Al

Al2O3

AlzOyFz

PF6-

Solvated PF6-

PF5

HF

Al: Anodic Oxidation Dissolution Mechanisms

in the Presence of LiPF6 vs. LiTFSI*

Al

Al2O3

TFSI-

Solvated TFSI-

Al3+

TFSI- = N(SO2CF3)2-

*E. Krämer, MW, et al., J. Electrochem. Soc. 2013, 160 (2), A356-A360; E. Krämer, MW, et al., ECS Lett., 2012, 1(5), C1 - C3;

1 µm

200 µm

after 3 cycles

after 1,000 cycles

Oxidation

Oxidation

Static electricity: Several 10,000 Volts

Humans: Up to 30.000 Volts

High voltage grid: Several 100.000 Volts

Lightning: Several 10.000.000 Volts

*(in acidic solution)

-4.1 -3.040 0.0 3.070* 3.294* E / V vs. SHE

Sr/Sr+ Li/Li+ SHE F2/HF OF2

Batteries:

Possible: <8V

Practical: <5 V

Typical: 1.2 – 4V

“High Voltage” is Relative

“High Voltage” LIB

Towards High Energy Density LIB

with High Voltage (HV) Cathodes

• Energy density can be elevated by:

higher specific capacity

and higher cell voltage

(via cathode potential increase)

• The use of high voltage cathodes

materials presents a major

challenge to the oxidation stability

of the electrolyte

e.g., organic carbonate solvents:

> 4.2 - 4.3 V

E = C · V

Graphite

Anode

Cathode

0 V

NMC

1 V

2 V

3 V

4 V

5 V

Po

ten

tia

l v

s. L

i/Li

+

HV

Cathodes?

NMC

at HV

Cathode

• NMC can be charged to different

upper cut-off potentials

• Higher cut-off potential

⇒ HV application

⇒ higher specific energy

LiNi0.33Mn0.33Co0.33O2 (“1/3-NMC”) at HV:Enhanced Potential and Capacity

B. Xu, D. Qian, Z. Wang, Y.S. Meng, Materials Science and Engineering: R: Reports 2012, 73, 51-65

48%

Li+

68%

Li+

3.0 3.5 4.0 4.5

0

500

1000

1500

2000

Con

cent

ratio

n / µ

g L-1

Electrode potential vs. Li/Li+ / V

Ni Co Mn

• Enhanced average discharge potential

• Higher specific capacity

• Lower Coulombic Efficiency

• Insufficient cycle life

High Voltage Application of NMCUse of LiPF6 in Electrolyte at HV

� Metal Dissolution (Promoted by HF)

D.R. Gallus, MW, et al., Electrochimica Acta, 134 (2014) 393-398.

• Electrolyte: 1M LiPF6 in EC/DMC (1:1)

• Ni, Co, and Mn dissolution

• Large dissolution at 4.6 V vs. Li/Li+

NMC storage in

electrolyte

for 28 days

WE: NMC, CE, RE: Li

LiPF6

0 10 20 30 40 5080

100

120

140

160

180

Upper cut-off potential vs. Li/Li+

4.2 V4.4 V4.6 V

Sp

ecifi

c ca

pac

ity /

mA

h g-1

Cycle number

3.0 3.5 4.0 4.5 5.0 5.5 6.0

0.0

0.2

0.4

0.6

Cu

rre

nt d

ensi

ty /

mA

cm

-2

Potential vs. Li/Li+ / V

1 M LiPF6 in EC/DMC (1/1)

+ 1 wt% TMS diethylamine

0

400

800

1200

1600

Mn

conc

entr

atio

n / µ

g L-1

NMC storage at

4.6V vs. Li/Li+

for 28 days**

1/100

1M LiPF6 in EC/DMC + 1wt% TMS diethylamine

WE: LMO; CE, RE: Li

Scan rate: 0.1 mV s-1

• Patent Claim by Saidi et al.*: TMS diethylamine can reduce HF induced

transition metal dissolution*

• Proposal of mechanism by Zhang**

• Diethylamine = Leaving group (LG)

• However: Not stable at high cathode potentials

New HF (and H2O) Scavenging Electrolyte

Additives: TMS (Trimethylsilyl-) Based

**Mechanism S.S. Zhang, J Power Sources, 162 (2006) 1379-

1394

*M.Y. Saidi, F. Gao, J. Barker, C. Scordilis-Kelley, U.S. Patent 5,846,673 (1998)

TMS diethyl amine:

• Better capacity retention

•Low Coulombic efficiency

•Oxid. decomposition during cycling

0 10 20 30 40 500

40

80

120

160

200

240

1M LiPF6 in EC/DMC (1/1)

+ 1wt-% TMS diethylamine+ 1wt-% TMS trifluoroacetate

Spe

cific

cap

acity

/ m

Ah

g-1

Cycle number0 10 20 30 40 50

80

85

90

95

100

105

1M LiPF6 in EC/DMC (1/1)

+ 1wt-% TMS diethylamine+ 1wt-% TMS trifluoroacetate

Cou

lom

bic

eff

icie

ncy

/ %

Cycle number

TMS trifluoro acetate:

• Better capacity retention

•Higher Coulombic efficiency

•Enables HV application

Effect of TMS Additives on

NMC Cycling at HV*

WE: NMC; CE, RE: Li; 3.0-4.6V vs. Li

1st -3rd cycle: 0.2C; 4th-50th cycle: 1C

*D. Gallus, MW, et al., Electrochimica Acta, 2015, 184, 410-416

• Sufficient amounts of HF in the electrolyte are

beneficial in order to passivate the Al current

collector*

• TMS reduces amount of HF in the electrolyte

Al Passivation in TMS Electrolyte

in the Presence of Smaller HF Amounts

SEM of Al foils after polarization to 4.6 V vs. Li/Li+ for 24 h

a.) 1M LiPF6 in EC/DMC, b.) + 1 wt.-% TMS trifluoro acetate, c.) 1M LiTFSI in EC/DMC

Al : Constant voltage

@ 4.6 V vs. Li/Li+, 24 h

a b c

*E. Krämer, et al., J. Electrochem. Soc. 2013, 160 (2), A356-A360

E. Krämer, et al., ECS Lett., 2012, 1(5), C1 - C3.

Page 29

C Xn

)negativeelectrode

positiveelectrode

-electrolyte

+

discharge

charge

C Xn

Cn

C X2nC X2n

*W. Rüdorff, U. Hofmann, Z. Anorg. Allg. Chem., 238 (1938) 1.

The Ancestor of Li+ Ion Transfer Cells:

The HSO4- Ion Transfer Cell*

Spherical paracrystalline carbon (10~100 nm) with concentrically oriented

graphitic domains.

*R.D. Heidenreich, W.M. Hess, L.L. Ban, J. Appl. Cryst. 1968, 1, 1-19.

[*]

Carbon Black:

Small Amount, but Influential

Carbon black:

�High contact surface area

�High electronic conductivity

�High thermal conductivity

Thermal Treatment to Remove

Surface GroupsCB-N: non-treated

CB-SG: 1500 °C in Ar (slightly graphitized)

CB-HG: 2000 °C in Ar (highly graphitized)

2. Cyclic voltammetry

Potential range: 2.5-5.2 V vs. Li/Li+

Scan rate: 20 mV s-1

CB Graphitization Degree:� Anion intercalation into CB

1. Constant current cycling

Specific current 10 mA g-1

WE: 80 wt.% CB, 20 wt.% PVdF binder; CE/RE: Li

Electrolyte: 1M LiPF6 in EC/DMC (1:1)

• Balancing of cathode and anode capacity is crucial for safety and life

• “Extra” capacity at the cathode has to be considered

when balancing the anode capacity

• Anion intercalation may damage the electrolyte and the conductive additive

[1] X. Qi, B. Blizanac, A. DuPasquier, P. Meister, T. Placke, M. Oljaca, J. Li, M. Winter, Phys. Chem.

Chem. Phys., 2014, 16, 25306.

Anion Intercalation into Carbon Black Leads

to Extra Capacity

[1]

Dual-Ion Cell

Example: Metallic Li-Electrode

Negative Electrode Positive Electrode

Li+

Li+

X-

X-

X-

X-

Li+

Li+

Li+

X-

e-

CHARGE

Li+

Li+X-

X-

DISCHARGE

Electrolyte

Metallic Lithium Graphite

Lithium

metal

Placke, T.; Bieker, P.; Lux, S.F.; Fromm, O.; Meyer, H.-W.; Passerini, S.; Winter, M.;

Zeitschrift für Physikalische Chemie, 2012, 226, 391-407

Long-Term Cycling Stability:

Effect of Temperature*

Li vs. KS6; CMC

Pyr14TFSI, 0.3M LiTFSI

Cut-off: 3.4V – 5.0V

Current: 50mA/g

0 100 200 300 400 5000

20

40

60

80

100

120

140

20 °C 40 °C 60 °C

met. Li vs. KS6 graphite; Cut-off: 5.0 V

disc

harg

e ca

paci

ty /

mA

h g-1

cycle number

*Placke, T.; Fromm, O.; Lux, S.F.; Bieker, P.; Rothermel, S.;

Meyer, H.-W.; Passerini, S.; Winter, M.

Journal of the Electrochemical Society, 159, 2012, A1755-A1765.*

� LiPF6 is a “good” inactive material, as the reaction products with water and

protons (H+) allow to combine an Al collector with org. carbonate solvents.

� Alternative electrolyte salts such as LiTFSI (= LiN(SO2CF3)2) � Al dissolution.

� LiPF6 is an essential electrolyte component.

� LiPF6 is a “bad” inactive material, as the reaction products with water and

protons (H+) induce the formation of (hopefully not ?) highly toxic compounds.

� In any case, reducing the amount of inactive materials will reduce

the amount of dead mass and dead volume of the cell.

� The wish: A cell chemistry without any inactive materials.

Summary

Slide 35

0.0

7.5

15.0

22.5

30.0

37.5

45.0

10.09

2.002.20

14.22

1.130.812.30

8.15

0.450.45

3.20

Weight / g

Current Collector (Cu)

Binder (Anode)

Conductive Agent (Anode)

Graphite

Current Collector (Al)

Binder (Cathode)

Conductive Agent (Cathode)

LiFePO4

Electrolyte

Separator

Case, Vents, etc.

Inactive Materials:

Even Small Amounts Make a Big Difference

18650 cell: 45g; graphite anode

and lithium iron phosphate

(LiFePO4) cathode

Total cost per 18650 cell: 1.4 - 1.8 €

Total amount of CB: 1.58 g

Costs of CB/cell: 0.0158 € (10 € kg-1)

85 wt.% LiNi0.5Mn1.5O4;

10 wt.% CB; 5 wt.% PVdF

“An investment in knowledge pays the best interest.“

---Benjamin Franklin (American Publisher, Inventor and Scientist, 1706-1790)