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“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,
& Helmholtz Institute Muenster;
Ionics in Energy Storage,
IEK-12 of Forschungszentrum Juelich
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)
