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Tailor Made
Carbon and Graphite Based Anode Materials
for Lithium Ion Batteries
Heribert Walter, Battery+Storage 2013
Page 2
Agenda
SGL Group at a Glance
Anode Materials Overview
Material Synthesis and Modification
New Generation Anodes: Carbon/Graphite composites
Summary
Page 3
Company Profile
• SGL Group is one of the world’s largest
manufacturers of carbon-based products
• Comprehensive portfolio ranging from
carbon and graphite products to carbon
fibers and composites
• 47 production sites worldwide
• Service network covering more than 100
countries
• Sales of ~€ 1.7 bn in 2012
• Head office in Wiesbaden/Germany
• Approx. 6,700 employees worldwide
• Listed on MDAX
Page 4
Light Weight & Energy Systems – SGL’s Contribution to E-Mobility
Electro-
Mobility
Light Weight with Carbon Fiber Composites
Plus
Energy Systems – Li-Ion Batteries & Fuel Cells
Source: BMW
10 µm
graphite
C-coating
Plus
Gas Diffusion Layer Anode graphite
C- Fiber CF- Fabric
Page 5
Joint Forces for Best Solutions
More than 10 Years
Cooperation
World Largest Anode Production & Leading Edge
Technology Know How
Page 6
Anode Material Requirements
Success of Carbon Based Anodes
Low cost material
Good cycling stability (SEI, excellent reversible
capacity theoretical 372 mAh/g)
Lightweight
Electrochemical potential close to metallic Li
Reason of commercial success of C-based anode:
Technical Requirements of a good anode material:
Large reversible capacity
Small irreversible capacity
High rate capability
Safety
Compatibility with electrolyte and binders
Natural graphite
Artificial graphite Carbon based LTO
LIB anode material world market size
Yano Research Institute, 2012
Page 7
Carbon and Graphite Based Anode Materials
Overview
Graphite Amorphous Carbon
Natural Artificial
Spheroidized
graphite
Carbon coated
graphite
Hard Carbon Soft Carbon
Si/Sn- carbon
composites
Mesophase
Other carbon based materials
like carbon fibers, expanded
graphite, graphene, graphite
foils
Page 8
Typical Production Processes
Raw Material
Raw material Heat
treatment
Milling
and
rounding
Carbon
coating
XRD turbostratic disorder,
amount of rhombohedral
graphite,stacking faults,
crystallite dimension
Order and disorder
Raman R=ID / IG
C-rate, cycling stability, capacity
0
10
20
30
40
50
60
70
80
90
100
180 200 220 240 260 280 300 320 340 360 380
First cycle discharge capacity (mAh/g)
Fir
st
cyc
le e
ffic
ien
cy (
%)
Graphite (i.e. Coke)
Hard Carbon Hard Carbon
(i.e. Resin) (i.e. Resin)
Natural Graphite
Soft Carbon Soft Carbon
(i.e. Pitch) (i.e. Pitch)
Page 9
800 ° C
1200 ° C
1400 ° C
2200 ° C
>2400 ° C
Carbon
Graphite
800 ° C
1200 ° C
1400 ° C
2200 ° C
>2400 ° C
Carbon
Temperature
Graphite
Raw material Heat
treatment
Milling
and
rounding
Carbon
coating
Amorphous
Graphitization degree is determined via raw material and process temperature
Graphitization Degree (%)
Dis
ch
arg
e C
ap
ac
ity (m
Ah
/g)
100 78 80 82 84 86 88 90 92 94 96 98 300
310
320
330
340
350
360
370
Natural graphite
Typical Production Processes
Heat Treatment
Theoretical limit
Page 10
Lithium Storage in Amorphous Carbons
Disordered Structure
Amorphous Carbon Structure ‘Intercalation’ or ‘adsorption’ of Li+ Ions
Only intercalation type used for real
applications, typical capacities < 300 mAh/g
soft carbon hard carbon
Carbonization temperature <2500°C
Page 11
Lithium Intercalation into Graphite
Ordered Structure
Crystal hexagonal graphite
structure Li+ ‘intercalation’ into the graphite planes
Theoretical capacity 372 mAh/g
Typical capacity 330-360 mAh/g
Graphitization temperature
>2500°C
Basal Plane Surface
Pris
ma
tic S
urfa
ce
Page 12
Typical Production Process
Milling and Rounding
Li+
Li+
Graphite with medium
particle size
Graphite with very small
particle size
Raw material Heat
treatment
Milling
and
rounding
Carbon
coating Li+
Li+
d50 between 10 and 30 µm
d90< 70 µm
avoid large amount of fine particle fraction
Particle size distribution and
shape 0
25
75
125
175
225
275
325
375
1
Sp
ec
ific
Ca
pa
cit
y i
n m
Ah
/g
Consumer HEV EV
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)
Page 13
Raw material Heat
treatment
Milling
and
rounding
Carbon
coating
Surface Area
BET specific surfare area and active
surface area
Irreversible capacity, rate capability
Source: Hitachi Chemicals
Surface Area (m 2 /g)
Co
ulu
mb
ic E
ffic
ien
cy (
%)
0 89
90
91
92
93
94
95
96
Surface Area (m 2 /g)
Co
ulu
mb
ic E
ffic
ien
cy (
%)
Typical Production Process
Carbon Coating
1 2 3 4 5
Page 14
From Process to Properties
Process Overview
Raw materials
• Coke base
Pre-treatment
• Grinding and crushing
Graphitisation process
• Procedure / Furnace
• Temp. and duration
Post-treatment
• Grinding and crushing
• Morphology tailoring
• Chemical modification
• Coating
• Reversible capacity
• Irreversible capacity
• Cycling stability
• Rate capability
• PC tolerance
• Ageing behaviour
• Self-Discharge
• Electrode Processability
• Safety
Structure
• 2H/3R ratio
• Turbostratic disorder
• Lattice defects
Morphology
• Particle shape
• Particle size
• Particle size distribution
• BET surface area
• Porosity
Chemistry
• Surface chemistry
• Lattice doping
Materials and
Tools
Materials
Properties
Electrochemical
Performance
Page 15
Anode Material for Automotive Application
Comparison of Different Material
Energy Life Power Safety Cost BPEV HEV
Artificial graphite
(MAG) ++ + - + - -
Artificial Graphite
(Low Cost) + + + + +
Natural Graphite
(w/ coating) + -- + - ++
Meso carbon - ++ ++ ++ - -
Hard Carbon
(Amorphous) - - ++ ++ ++ -
Soft Carbon
(Amorphous) - - + ++ ++ +
Material
Item
Source Hitachi
Page 16
80
90
100
110
120
130
140
150
160
0 500 1000 1500 2000 2500 3000 3500 4000
Anode Capacity (mAh/g)
Th
eo
reti
cal
Cell
Cap
acit
y (
mA
h/g
)
Graphite
Carbon
Sn-M-C Composites
Sn C-Si
Composites
Li-Metal
LTO
1000 2000 3000 Capacity (mAh/g)
Po
ten
tia
l vs
. L
i/L
i+
.
.
KathAnode
KathAnodeZelle
KapKap
KapKapKap
e.g. cathode: LiCoO2 Need for high capacity
anodes to improve the
overall cell capacity
Carbon-Silicon Composites
Adopted from: A. Lamm, Ausblick Batterie-und zelltechnologie Li-Ionen aus Sicht der Automobilindustrie, 26.09.2012
Silicon-Carbon Composites
are promising next generation
anode materials
Si
Highest benefit to cell capacity is for anode
material up to 1000 mAh/g with the actual
cathodes higher than 80% carbon
Lithium Ion Batteries, N. Dimov, Saga University
Page 17
Extreme volume expansion during lithiation/delithiation of about 300% (graphite 6-10%)
leads to cracking of Si particles and electrode
Poor Cycling stability
• Compensate the volume expansions of silicon
• Good electronic and ionic conductivity
• Protect the silicon from contact with the electrolyte
Carbon-Silicon Composites
C/Si-Composites: Silicon nanoparticles within a carbon matrix Carbon
Nano-Si
Advantage of Carbon-Silicon Composite Anodes
Drawback of pure silicon anodes:
Page 18
Summary
Graphite anode accounts for over 95% of current anode market (Yano
report)
Carbon and Graphite properties can be tailored to meet battery
requirements by adapting the raw materials and production processes
Next generation anodes are most likely C-Si based. The carbonaceous
material (80C / 20 Si) to guarantee overall electrode performances
To get optimum cell capacity the target anode capacity is <1000 mAh/g.
Thus amorphous carbon will be the dominant element in composites
Carbon and graphite are the anodes of today,
tomorrow
and the day after tomorrow!
Take away:
