Carbon-Based Negative Electrode Active Materials for Lithium-Ion Batteries
Past, Present and Trends towards the Future
Pirmin A. Ulmann
IMERYS Graphite & Carbon
Bodio TI, Switzerland
MAT4BAT Summer School at EIGSI La Rochelle, France
3.6.2015
Introduction IMERYS Graphite & Carbon
- IMERYS Graphite & Carbon supplies carbon-based
solutions for various technical applications.
- Supplier for mobile energy applications since the
early 1980ies: carbons for alkaline batteries.
Bodio, Switzerland
- Supplier of carbons for Li-ion batteries since the
early 1990ies.
- Supplier of carbons for fuel cell, lead-acid battery
and other mobile energy applications.
Willebroek, Belgium
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Electrochemical Cell – Lithium-Ion Battery
Cu current collector
electrolyte (in pores)
active material
negative electrode (anode)
graphite
carbon black
binder
separator
e-
IMERYS Graphite & Carbon
products are inside the positive
and the negative electrode
Li+
electrolyte (in pores)
active material
graphite
positive electrode (cathode)
current collector
coating
Al current collector
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carbon black
binder
Carbon Anode Materials in Early Lithium-Ion Batteries
Yoshino et al.: - polyacetylene/LiCoO2
(Asahi Kasei,
1983-)
- VGCF (vapor-phase-grown carbon fiber)/LiCoO2
 early operational systems
Nishi et al.:
(Sony, 1985-)
- soft carbon (graphitizable carbon)/LiCoO2
1st gen. battery 80 Wh kg-1, 200 Wh L-1
- hard carbon (non-graphitizable carbon)/LiCoO2
2nd gen. battery 120 Wh kg-1, 295 Wh L-1
- graphite/LiCoO2
 switch PC to EC-containing electrolyte
3rd gen. battery 155 Wh kg-1, 400 Wh L-1
A. Yoshino, Angew. Chem. Int. Ed. 2012, 51, 5798.
Y. Nishi, J. Power Sources 2001, 100, 101.
Y. Nishi, The Chemical Record 2001, 1, 406.
Stable Li-intercalation in graphite:
R. Yazami, Ph. Touzain, J. Power Sources 1983, 9, 365.
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Hard Carbon / Soft Carbon as Active Material
1st charge/
discharge
Hard
Carbon
2nd charge/
discharge
- Both soft and hard carbon exhibit a steeply sloping potential curve during Li-intercalation.
- Treatment at 1100-1200 °C (Sony)  typical industrially relevant capacities for
soft carbon ca. 200 mAh/g, for hard carbon ca. 300 mAh/g.
- Stability towards PC (propylene carbonate) because of disordered carbon structure.
- Hard carbon was initially more difficult to process than soft carbon.
Y. Nishi, The Chemical Record 2001, 1, 406. J. R. Dahn et al. Science 1995, 270, 590.
P. Novàk, D. Goers, M. E. Spahr, Carbon Materials in Li-Ion Batteries, in Carbons for Electrochemical Energy
Conversion Systems, F. Béguin, E. Frackowiak (Eds.), 263 (2010).
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Graphite as Active Material
Synthetic
Graphite
- Reversible capacity close to 370 mAh/g, plateau-shaped potential curve results in
favorable energy density. Irreversible capacity broadly correlates with BET surface area.
- Challenge 1: avoid exfoliation due to highly crystalline graphite
( use EC-containing electrolytes for favorable SEI-formation).
- Challenge 2: prevent Li-plating during charging because of flat potential curve
( control of microstructure and SEI-formation).
- Challenge 3: prevent unfavorable swelling/aging effects due to volume change during
cycling ( control of microstructure).
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Natural Graphite vs. Synthetic Graphite as Active Material
Natural
Graphite
Synthetic
Graphite
rounded particles
exhibit point-to-point
interactions:
may decontact
upon volume change
blocky particles
exhibit more robust
surface-to-surface
interactions.
T. Nishida,
AABC 2013, Pasadena
- Typical natural graphite active materials are rounded, exhibit large, highly oriented crystallites.
- Typical synthetic graphites exhibit a blocky shape, less oriented crystallites.
- Carbon coating is common to decrease surface reactivity.
- High performance synthetic graphites exhibit better cycle life and charge acceptance
vs. typical coated natural graphites.
- Stringent graphitization process control leads to safety advantage for synthetic graphite.
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Synthetic Graphite Active Materials with Hydrophilic Surface
C-NERGYTM ACTILION active material
coated natural graphite
- Synthetic graphite active materials from IMERYS Graphite & Carbon exhibit
advantageous charge acceptance due to optimized electrode-electrolyte interface.
- Hydrophilic surface leads to very favorable cycling stability.
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The Performance Triangle in Lithium-Ion Battery Design
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Carbon Anode Active Materials for Automotive Batteries
- Energy, cycle life and safety are crucial advantages for synthetic graphite
in EV (fully electric vehicles or plug-in electric vehicles).
- Due to power performance requirements, hard and soft carbons are
advantageous for HEV (hybrid electric vehicles).
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Carbon Anode Active Materials for Stationary Energy Storage
& Consumer Electronics Applications
Important
Energy
Stationary
Energy
Storage
Consumer
Electronics
Cycle Life
Fast
Charge
Unimportant
Safety
Costs
+
+++++
variable
+++++
+++++
+++++
+
+++
+++
++
- Cycle life, safety and costs are of key importance for stationary energy
storage  unclear yet if Li-ion batteries are most suitable system.
- Alternatives to graphite with higher reversible capacity are sought for in
consumer electronics applications.
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High Energy Anode Materials – Summary
Industrial requirements relate to several dimensions:
- Sufficient cycling stability in full cell (min. 80% after 500 cycles).
- Limited irreversible losses & limited BET surface area of active material
 safety considerations, avoid thermal runaway due to excessive SEI-growth.
- Sufficient electrode loading & density.
- Acceptable costs, environmental sustainability.
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Alloy-Based High Capacity Negative Active Materials
Cycling stability of Nexelion battery
Alloy materials produced with melt-spinning process:
Sn-Co alloy mixed
with graphite
> 70% capacity
retention after 500 cycles
in fully optimized full cells,
alloy mixed with graphite.
Source: D. Foster et al., US Army Research Report,
ARL-TN-0319, 2008
Source: 3M
>1000 mAh/g rev. capacity
ca. 15% 1st cycle irrev. losses
- Sony Nexelion battery launched in 2005: 30% increase of capacity vs. graphitebased system, but limited cycling stability.
- Intensive industrial R&D efforts (patent applications) on alloy materials
produced using melt-spinning process.
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Conclusions
- Selection of appropriate carbon active material based on
application requirements.
- High energy active material in high demand for consumer
electronics and automotive applications.
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Acknowledgements
- Michael Spahr, Michal Gulaš, Simone Zürcher, Dario Cericola,
Flavio Mornaghini, Thomas Hucke, Julie Michaud, Marlene Rodlert,
Antonio Leone, Salvatore Stallone, Francesco Matarise
- MAT4BAT Consortium Partners
- Funding: EU Commission (FP7) / Swiss Government (KTI)
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