“A tidy laboratory means a lazy chemist” Jöns Jacob Berzelius

“A tidy laboratory means a lazy chemist” Jöns Jacob Berzelius

“A tidy laboratory means a lazy chemist”
Jöns Jacob Berzelius (Swedish chemist,1779-1848)
6. SEC-Jahrestreffen, 18. - 20. Mai 2016 in Münster (GER)
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
MEET Battery Research Center,
Institute of Physical Chemistry,
Univ. of Muenster, GER,
[email protected]
& Helmholtz Institute Muenster;
Ionics in Energy Storage,
IEK-12 of Forschungszentrum Juelich
[email protected]
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
Acknowledgements
(Specific)
German Ministry of Education and Research (BMBF)
within the project “Elektrolytlabor 4E”
Cabot Corporation
Acknowledgements
None of us is as smart as all of us
Lithium Ion Battery (LIB):
Active and Inactive Materials Have Functions
Active 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)
(Cathode)
Zn
Zn2+ + 2 eCuO + 2H+ + 2e- Cu + H2O
Cu reacts with O2, regen. CuO
Closed Cell @ 0.76V
(Anode)
(Cathode)
Zn
Zn2+ + 2e2 H+ + 2e- H2
on 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)
*
*Winter, M.; Besenhard, J. O.
Chemie in unserer Zeit 1999, 33, 320-332
Inactive Materials necessary for cell
reaction: electrolyte, separator
and electrode formulation:
additives, binders, collectors
Inactive materials: Packaging, vents, etc.
18650: The Standard Cylindrical Cell:
Notebook Computers and Power Tools
+
Depending on chemistry and
technology: 30 to >50 grams
Case typically: stainless steel, Al
65 mm
18.0 mm
617 mm
Anode
60 mm
Cathode
57 mm
Separator
2 x 600 mm = 1200 mm
57 mm
-
Mass Distribution in an 18650 cell:
5 Main Groups of Components
Anode Total
45.0
12.25
37.5
g
/ 30.0
t
h
gi
e 22.5
W
Electrolyte
18.46
Separator
Case, Vents, etc.
15.0
2.20
2.00
7.5
10.09
0.0
Cathode Total
18650 cell: 45g;
based on graphite anode
and lithium iron phosphate
(LiFePO4) cathode
Mass Distribution in an 18650 cell:
Component Details
Current Collector (Cu)
45.0
37.5
g
/ 30.0
t
h
gi
e 22.5
W
15.0
18650 cell: 45g;
based on graphite anode
and lithium iron
phosphate
(LiFePO4) cathode
3.200.45
0.45
8.15
2.30
0.81 1.13
14.22
Binder (Anode)
Conductive Agent (Anode)
Graphite
Current Collector (Al)
Binder (Cathode)
Conductive Agent (Cathode)
2.20
2.00
LiFePO4
Electrolyte
7.5
0.0
10.09
Separator
Case, Vents, etc.
Mass Distribution in an 18650 cell:
Summary: Active vs. Inactive Materials
49.71 wt.% Active Mat.
45.0
14.22
37.5
g
/ 30.0
t
h
gi
e 22.5
W
15.0
7.5
0.0
Cathode Act. Mat.
Anode Act. Mat.
8.15
Inactive
22.63
50.29 wt.% Inactive
18650 cell: 45g;
based on graphite anode
and lithium iron phosphate
(LiFePO4) cathode
Mass Distribution in an 18650 cell:
Lithium Ion Battery is Sham
♦Li Active:
♦Li Inactive:
♦Rest:
0.52g (= 1.16 wt.%): mobile Li from Cathode Material
0.21g (= 0.27 wt.%): Li Loss from Cathode Material
+ Li in Electrolyte
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*
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
34 Ah Metal can EV Cell
Material Costs*
Material costs
on cell level:
Active: 46.9%
Inactive: 53.1%
*Source: Total Battery Consulting, 2015
5 Ah HEV Cell, 200k Packs per Year
Material Costs*
216 MWh Plant
5-Ah, 500-W HEV Cell
NMC/graphite, Metal Can, 12 Million HEV Cells / year
Units
Amount
$/unit
$/cell
Cathode Active Materials
kg
0.039
30
1.18
Anode Active Materials
kg
0.022
18
0.40
Electrolyte
kg
0.025
20
0.51
Separator
m
2
0.563
1.8
1.01
Copper Foil
kg
0.020
17
0.33
Can, Headers & Terminals
cell
1
1.75
1.75
Other
cell
1
1.0
1.00
Total Materials
6.18
Per kWh
339
Per kW
12.4
Material costs
on cell level:
Active: 25.6%
Inactive: 74.4 %
*Source: Total Battery Consulting
An Example for an “Inactive”, but not “Passive” Material:
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.
Current Collectors:
Requirements for LIB*
Excellent electronic conductivity:
Ag, Cu, Au, Al,…
Low cost:
Ag,
X Cu, Au,
X Al
Electrochemically stable within the electrode operation potentials:
Metals that
alloy with Li
He
Al alloys with Li at carbon anode potentials
Cu is oxidized at >∼3.5V vs. Li/Li+
B
C
N
O
F
Ne
Al
Si
P
S
Cl
Ar
Cu Zn Ga Ge As Se
a
Ru Rh Pd Ag Cd In Sn Sb Te
Br
Kr
I
Xe
Os
At
Rn
Fe Co
Ir
Ni
Pt
Au Hg
Tl
Pb
Bi
Po
(= cathode potentials), surface impurities
⇒ Cu → anode, Al (!) → cathode
(LiPF6 necessary!)
Processing to thin foils (in the 10-20 µm range) possible √
Rel. light weight √
Chemically and thermally stable/inert √
*Considerations are valid for lithium ion cells
with carbonaceous anode and 4-V cathode!
Al: Anodic Oxidation Dissolution Mechanisms
in the Presence of LiPF6 vs. LiTFSI*
Al
Al2O3
AlzOyFz
PF6-
PF5
Solvated PF6-
HF
1 µm
after 1,000 cycles
Oxidation
Al
Al2O3
Al3+
TFSI-
TFSI- = N(SO2CF3)2-
Solvated TFSI200 µm
Oxidation
after 3 cycles
*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;
“High Voltage” LIB
“High Voltage” is Relative
Lightning: Several 10.000.000 Volts
High voltage grid: Several 100.000 Volts
Static electricity: Several 10,000 Volts
Humans: Up to 30.000 Volts
Sr/Sr+ Li/Li+
SHE
F2/HF OF2
-4.1 -3.040
0.0
3.070* 3.294*
E / V vs. SHE
*(in acidic solution)
Batteries:
Possible: <8V
Practical: <5 V
Typical: 1.2 – 4V
Towards High Energy Density LIB
with High Voltage (HV) Cathodes
E=C·V
5V
Potential vs. Li/Li+
4V
?
HV
Cathodes
NMC
at
HV
NMC
Cathode
Cathode
• 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
3V
2V
1V
Graphite
0V
• Energy density can be elevated by:
higher specific capacity
and higher cell voltage
(via cathode potential increase)
Anode
LiNi0.33Mn0.33Co0.33O2 (“1/3-NMC”) at HV:
Enhanced Potential and Capacity
• NMC can be charged to different
upper cut-off potentials
• Higher cut-off potential
⇒ HV application
⇒ higher specific energy
B. Xu, D. Qian, Z. Wang, Y.S. Meng, Materials Science and Engineering: R: Reports 2012, 73, 51-65
48%
Li+
68%
Li+
High Voltage Application of NMC
Use of LiPF6 in Electrolyte at HV
Metal Dissolution (Promoted by HF)
180
-1
WE: NMC, CE, RE: Li
LiPF6
160
1000
140
120
Upper cut-off potential vs. Li/Li
4.2 V
4.4 V
4.6 V
100
80
1500
Concentration / µg L
Specific capacity / mAh g
-1
2000
0
10
20
30
+
500
Ni
Co
Mn
NMC storage in
electrolyte
for 28 days
0
40
50
3.0
Cycle number
3.5
4.0
4.5
+
Electrode potential vs. Li/Li / V
•
Enhanced average discharge potential
•
Electrolyte: 1M LiPF6 in EC/DMC (1:1)
•
Higher specific capacity
•
Ni, Co, and Mn dissolution
•
Lower Coulombic Efficiency
•
Large dissolution at 4.6 V vs. Li/Li+
•
Insufficient cycle life
D.R. Gallus, MW, et al., Electrochimica Acta, 134 (2014) 393-398.
New HF (and H2O) Scavenging Electrolyte
Additives: TMS (Trimethylsilyl-) Based
•
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
1600
1200
800
NMC storage at
4.6V vs. Li/Li+
for 28 days**
1/
10
0
400
0
1M LiPF6 in EC/DMC + 1wt% TMS diethylamine
Current density / mA cm
Mn concentration / µg L
-1
-2
**Mechanism S.S. Zhang, J Power Sources, 162 (2006) 13791394
1 M LiPF6 in EC/DMC (1/1)
0.6
+ 1 wt% TMS diethylamine
0.4
0.2
WE: LMO; CE, RE: Li
Scan rate: 0.1 mV s-1
0.0
3.0
3.5
4.0
4.5
5.0
5.5
+
Potential vs. Li/Li / V
*M.Y. Saidi, F. Gao, J. Barker, C. Scordilis-Kelley, U.S. Patent 5,846,673 (1998)
6.0
Effect of TMS Additives on
NMC Cycling at HV*
1 05
WE: NMC; CE, RE: Li; 3.0-4.6V vs. Li
1st -3rd cycle: 0.2C; 4th-50th cycle: 1C
2 00
Coulombic efficiency / %
Specific capacity / mAh g
-1
2 40
1 00
1 60
1 20
80
1M LiPF6 in EC/DMC (1/1)
+ 1wt-% TMS diethylamine
+ 1wt-% TMS trifluoroacetate
40
0
0
10
20
30
40
50
95
90
1M LiPF6 in EC/DMC (1/1)
85
80
Cycle number
+ 1wt-% TMS diethylamine
+ 1wt-% TMS trifluoroacetate
0
10
20
30
40
Cycle number
TMS diethyl amine:
TMS trifluoro acetate:
•
•
Better capacity retention
Better capacity retention
•Low Coulombic efficiency
•Higher Coulombic efficiency
•Oxid. decomposition during cycling
•Enables HV application
*D. Gallus, MW, et al., Electrochimica Acta, 2015, 184, 410-416
50
Al Passivation in TMS Electrolyte
in the Presence of Smaller HF Amounts
• Sufficient amounts of HF in the electrolyte are
beneficial in order to passivate the Al current
collector*
Al : Constant voltage
@ 4.6 V vs. Li/Li+, 24 h
• TMS reduces amount of HF in the electrolyte
a
b
c
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
*E. Krämer, et al., J. Electrochem. Soc. 2013, 160 (2), A356-A360
E. Krämer, et al., ECS Lett., 2012, 1(5), C1 - C3.
The Ancestor of Li+ Ion Transfer Cells:
The HSO4- Ion Transfer Cell*
)
-
negative
electrode
C 2n X
+
electrolyte
discharge
positive
electrode
C 2n X
charge
Cn
C nX
*W. Rüdorff, U. Hofmann, Z. Anorg. Allg. Chem., 238 (1938) 1.
Page 29
Carbon Black:
Small Amount, but Influential
Spherical paracrystalline carbon (10~100 nm) with concentrically oriented
graphitic domains.
[*]
Carbon black:
High contact surface area
High electronic conductivity
High thermal conductivity
Thermal Treatment to Remove
Surface Groups
CB-N: non-treated
CB-SG: 1500 °C in Ar (slightly graphitized)
CB-HG: 2000 °C in Ar (highly graphitized)
*R.D. Heidenreich, W.M. Hess, L.L. Ban, J. Appl. Cryst. 1968, 1, 1-19.
CB Graphitization Degree:
Anion intercalation into CB
WE: 80 wt.% CB, 20 wt.% PVdF binder;
CE/RE: Li
Electrolyte: 1M LiPF6 in EC/DMC (1:1)
1. Constant current cycling
Specific current 10 mA g-1
2. Cyclic voltammetry
Potential range: 2.5-5.2 V vs. Li/Li+
Scan rate: 20 mV s-1
Anion Intercalation into Carbon Black Leads
to Extra Capacity
[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.
Dual-Ion Cell
Example: Metallic Li-Electrode
Metallic Lithium
CHARGE
DISCHARGE
Li+
X-
X-
Li+
Lithium
metal
Li+
X-
eLi+
X-
XLi+
XLi+
Negative Electrode
Graphite
Li+
X-
Electrolyte
Positive Electrode
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*
met. Li vs. KS6 graphite; Cut-off: 5.0 V
discharge capacity / mAh g
-1
140
120
100
80
60
40
20 °C
40 °C
60 °C
20
Li vs. KS6; CMC
Pyr14TFSI, 0.3M LiTFSI
Cut-off: 3.4V – 5.0V
Current: 50mA/g
0
0
100
200
300
400
500
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.*
Summary
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.
Slide 35
Inactive Materials:
Even Small Amounts Make a Big Difference
Current Collector (Cu)
45.0
37.5
g
/ 30.0
t
h
gi
e 22.5
W
15.0
3.20
0.45
0.45
8.15
2.30
0.81 1.13
14.22
Binder (Anode)
Conductive Agent (Anode)
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)
Graphite
Current Collector (Al)
Binder (Cathode)
Conductive Agent (Cathode)
2.20
2.00
LiFePO4
Electrolyte
7.5
0.0
10.09
Separator
Case, Vents, etc.
18650 cell: 45g; graphite anode
and lithium iron phosphate
(LiFePO4) cathode
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)