Graphite Powder Processing
A Key Element for High Performance Lithium-Ion Batteries
Bernt Ketterer, Ulrich Bosch, Oswin Öttinger, DKG-AKK Herbsttagung, 7th November 2014
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Graphite Powder Processing for High Performance Lithium-Ion Batteries Outline
SGL Proprietary Information
1. Graphite Anode Materials: Position of SGL & Market Perspectives
2. Anode Materials for Lithium Batteries: Basic Requirements
3. Powder Design for High Performance Graphite Anodes, Influences of: • BET Surface Area • Particle Size • Particle Shape
4. Summary
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LIB Anode Materials Overview Material Share – Status 2012
Source: SGL, Avicenne, Battery Market Development 2012-2025
- Artificial and natural graphite biggest share (total >90%)
- Next generation high capacity materials (silicon and tin based) enter the market
- Fast growing market for graphite anodes in 3C and electromobility
Total Volume in 2012: ~32000t
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Graphite Anode Materials Joint Forces for Best Solutions
World Largest Synthetic Graphite Anode Production & Leading Edge Technology Know How
More than 10 Years Cooperation
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Graphite Powder Processing for High Performance Lithium-Ion Batteries Outline
SGL Proprietary Information
1. Graphite Anode Materials: Position of SGL & Market Perspectives
2. Anode Materials for Lithium Batteries: Basic Requirements
3. Powder Design for High Performance Graphite Anodes, Influences of: • BET Surface Area • Particle Size • Particle Shape
4. Summary
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electrons flow
Graphite-Anode
Al –
cu
rren
t co
llect
or C
u – cu
rrent co
llector Cathode
Charge Li+ ions flow
Li+ ions
electrons flow
Al –
cu
rren
t co
llect
or C
u – cu
rrent co
llector
Li+ ions flow
Cathode Graphite-Anode
sepa
rato
r
Discharge
Li+ ions
Lithium Ion Battery: Basic Working Principle
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sepa
rato
r
Electrolyte
Electrolyte
Graphite Polymeric
Binder
Conductive additive
Cu-foil current collector
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Li-Ion Battery - Graphite as Anode Material Solid Electrolyte Interface - SEI
Source: TEM: F. Orsini, L. Dupont, B. Beaudoin, S. Grugeon, J.-M. Tarascon, Int. J. Inorg. Mater. 2 (2000), 701 AND E. Peled, D. Golodnitsky and G. Ardel, J. Electrochem. Soc. 144 (1997), L208.
TEM of Solid Electrolyte Interphase Schematic drawing of the composition of the SEI
First Cycle: Carbon/graphite + Electrolyte Solid Electrolyte Interphase
Solid Electrolyte Interphase (SEI)
Carbon/ Graphite
Li2O
LiF
LiF
LiF
Li2O
Li2O
Li2O
Li2CO3
LiF
Li2O
Li2O
Li2CO3
Li2CO3
Electrolyte (LiPF
6 , Carbonates,etc.)
Polyolephines
Semicar bonates
Polyole phines
The SEI protects the graphite from solvent co-intercalation Graphite would not work without SEI
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SEI formation consumes Lithium!
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Key Parameters of Electrode Materials: Capacity and Efficiency
Capacity loss (1st Cycle Efficiency): How much lithium contributes to SEI-formation? Depending on:
• specific surface (e.g. BET)
• particle size and shape
Capacity: How much lithium is intercalated in graphite? Depending on:
•How many defects are in the graphite?
• Degree of graphitization
Surface –Electrolyte Interphase Layer (‚SEI‘ ): Passivating layer formed on the graphite particle surface
Li Graphite Particle
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1µm
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Specific Capacity (mAh/g)
Voltage Level
1st Cycle Efficiency
Electrode Loading (mAh/cm²)
% Inactive Material
Film Swelling
Material & Film Density (g/cm³)
Rate Capability (Temperature-Dependence)
Particle Size / BET
Purity
Cycle Stability
Graphite Anode Materials: Basic Requirements
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Gravimetric Energy Density
Wh/kg Volumetric Energy Density
Wh/l
Safety
Directly Influenced by Graphite Particle
Properties
Lightweight Battery
Small Battery
Power Density W/kg or W/l
Battery Level Material Level
Acceleration
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Graphite Powder Processing for High Performance Lithium-Ion Batteries Outline
SGL Proprietary Information
1. Graphite Anode Materials: Position of SGL & Market Perspectives
2. Anode Materials for Lithium Batteries: Basic Requirements
3. Powder Design for High Performance Graphite Anodes, Influences of: • BET Surface Area • Particle Size • Particle Shape
4. Summary
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Lower BET Surface Area: Optimized Battery 1st Cycle Efficiency
Surface Area (m 2 /g) 0
89
90
91
92
93
94
95
96
Surface Area (m 2 /g)
Cou
lum
bic
Effic
ienc
y (%
) C
oulu
mbi
c Ef
ficie
ncy
(%)
1 2 3 4 5
A low BET surface is crucial for: • 1st cycle Efficiency (low Li losses) • Energy density • Safety • Cycle life • Binder demand …
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Lower the BET Surface Area: Influence of the milling device
Milling type & milling & spheroidisation equipment configuration influence significantly the particle shape / BET and therefore also the battery performance
Additionally milling & rounding yield is the key element for commercial success
Different Milling Devices
BET
Surf
ace
(r
elat
ive
num
bers
) d50 = const.
Examples from Different Milling Devices
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Lower the BET Surface Area: Influence of rounding and the coating
2 nm
Graphite
Carbon coating layer
10 µm 10 µm
Rounding Coating
Graphite powder Engineered anode material
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Lower BET Suface
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Quicker Charge/Discharge: Influence of the Particle Size
Li+
Li+
Graphite with medium
particle size
Graphite with very small
particle size
Li+
Li+
d50 between 10 and 30 µm d90< 70 µm Low amount of fine particle fraction
Particle size distribution and shape
0 25
75
125
175
225
275
325
375
Spec
ific
Cap
acit
y in
mA
h/g
High Energy
slow quick Log (Dis. - )/Charging Time
very small D 50 value ( i.e . 10 µ m)
Medium D 50 Value ( i.e . 20 µ m)
Smaller anode particle size distribution is beneficial for quicker LIB charging. However… Formation of higher surface area
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High Power
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Quicker Charge/Discharge: Influence of the Particle Shape
How fast is lithium intercalated in graphite? Depending on particle orientation in the electrode
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Cu-current collector
x ‘Flaky’ Graphite Particles
Potato Shaped Graphite Particles
Li+
Li+
Flaky
Potato
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High Film Density for Improved Energy Density: Influence of Particle Shape & Particle Size Distribution
„Potato shape“ particle generates higher film packing density at lower compaction pressures
Bimodal / “broader” particle size distribution can generate higher film
packing densities. However, BET need to be kept low, otherwise efficiency loss
Compaction Pressure
Elec
trod
e Fi
lm D
ensi
ty
high Low
high
“Potato”particle shape
“Flaky”particle shape
0,1 1 10 0,1 1 10
Elec
trod
e Fi
lm D
ensi
ty
Density + 20%
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Particle Size Particle Size
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Graphite Powder Processing for High Performance Lithium-Ion Batteries Outline
SGL Proprietary Information
1. Graphite Anode Materials: Position of SGL & Market Perspectives
2. Anode Materials for Lithium Batteries: Basic Requirements
3. Powder Design for High Performance Graphite Anodes, Influences of: • BET Surface Area • Particle Size • Particle Shape
4. Summary
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Graphite Powder Processing for High Performance Lithium-Ion Batteries Key Elements - Summary
Energy Density
1st Cycle Efficiency
Quick Charge
Cycle Life
Particle Size
Particle Surface
(coating)
Particle Shape (BET)
Particle Size Distribution
Yield Costs
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© Copyright SGL CARBON SE Registered trademarks of SGL CARBON SE ®
Thank you for your attention!
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Important note: This presentation may contain forward-looking statements based on the information currently available to us and on our current projections and assumptions. By nature, forward-looking statements involve known and unknown risks and uncertainties, as a consequence of which actual developments and results can deviate significantly from these forward-looking statements. Forward-looking statements are not to be understood as guarantees. Rather, future developments and results depend on a number of factors; they entail various risks and unanticipated circumstances and are based on assumptions which may prove to be inaccurate. These risks and uncertainties include, for example, unforeseeable changes in political, economic, legal, and business conditions, particularly relating to our main customer industries, such as electric steel production, to the competitive environment, to interest rate and exchange rate fluctuations, to technological developments, and to other risks and unanticipated circumstances. Other risks that in our opinion may arise include price developments, unexpected developments connected with acquisitions and subsidiaries, and unforeseen risks associated with ongoing cost savings programs. SGL Group does not intend or assume any responsibility to revise or otherwise update these forward-looking statements.
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