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

2

Introduction IMERYS Graphite & Carbon

Bodio, Switzerland

Willebroek, Belgium

- IMERYS Graphite & Carbon supplies carbon-based

solutions for various technical applications.

- Supplier for mobile energy applications since the

early 1980ies: carbons for alkaline batteries.

- 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.

3

Electrochemical Cell – Lithium-Ion Battery

Li+

negative electrode (anode)

positive electrode (cathode)

e-

separator IMERYS Graphite & Carbon

products are inside the positive

and the negative electrode

electrolyte (in pores)

active material

graphite

carbon black

binder

electrolyte (in pores)

active material

graphite

carbon black

binder

Cu current collector

Al current collector

current collector

coating

Yoshino et al.: - polyacetylene/LiCoO2

(Asahi Kasei, - VGCF (vapor-phase-grown carbon fiber)/LiCoO2

1983-) early operational systems

Nishi et al.: - soft carbon (graphitizable carbon)/LiCoO2

(Sony, 1985-) 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

4

Carbon Anode Materials in Early Lithium-Ion Batteries

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.

5

Hard Carbon / Soft Carbon as Active Material

Hard

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).

- 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.

1st charge/

discharge

2nd charge/

discharge

6

Graphite as Active Material

- 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).

Synthetic

Graphite

7

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.

8

Synthetic Graphite Active Materials with Hydrophilic Surface

- 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.

C-NERGYTM ACTILION active material coated natural graphite

9

The Performance Triangle in Lithium-Ion Battery Design

10

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).

Important Unimportant

11

Carbon Anode Active Materials for Stationary Energy Storage

& Consumer Electronics Applications

Energy Cycle Life Fast

Charge

Safety Costs

Stationary

Energy

Storage

+ +++++ variable +++++ +++++

Consumer

Electronics +++++ + +++ +++ ++

- 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.

12

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.

13

Alloy-Based High Capacity Negative Active Materials

- Sony Nexelion battery launched in 2005: 30% increase of capacity vs. graphite-

based system, but limited cycling stability.

- Intensive industrial R&D efforts (patent applications) on alloy materials

produced using melt-spinning process.

Source: D. Foster et al., US Army Research Report,

ARL-TN-0319, 2008 Source: 3M

Cycling stability of Nexelion battery Alloy materials produced with melt-spinning process:

> 70% capacity

retention after 500 cycles

in fully optimized full cells,

alloy mixed with graphite.

Sn-Co alloy mixed

with graphite

>1000 mAh/g rev. capacity

ca. 15% 1st cycle irrev. losses

14

Conclusions

- Selection of appropriate carbon active material based on

application requirements.

- High energy active material in high demand for consumer

electronics and automotive applications.

15

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)