Natural Graphite versus Synthetic, Silicon and Others in Lithium Ion

Battery Anodes

George C Hawley President

George C Hawley & Associates Supermin123@hotmail.ca

Biography George C. Hawley & Associates was established in 1971 as a consulting practice for industrial mineral producers and consumers, world -wide. He was R&D/QC Chemist at Morgan Crucible (Morganite Carbon) researching polymer impregnated graphite brushes, electrodes, friction materials, sealing rings, nuclear graphite, rocket nozzles and chemical graphite. As R&D/QC Chemist at the Chloride Group, he worked on high porosity plastic separators, cases, and anodes and cathodes for lead-acid batteries. Since 2002, he has returned to graphite R & D and Market Research and Development, as a consultant to Quinto Mining, and Industrial Minerals Inc. (now Northern Graphite Corporation). Achievements have been the development of lithium-ion anode grade products based on NGC concentrate, including novel purification technology to increase purity of this and flake graphite to 99.95+%. G.C. Hawley has published over 50 papers on technical and marketing topics of industrial minerals and mineral-based products, including chapters in 3 handbooks.

Abstract Lithium battery production continues to grow at about 10% per year, based on their unrivalled properties. Lithium metal would be the best anode and it is used in primary (non-rechargeable) cells. But lithium metal reacts violently with both air and water and grows dendrites which tend to short out the electrodes The solution is to have lithium present in the anode in the form of non-explosive ions. These ions are intercalated between the layers of the graphite crystal. Both synthetic and natural graphite fine powders are use in the anodes. These two types compete actively in price and performance. The specific capacity of graphite is low in comparison with metals that can take up lithium by alloying, in amounts up to ten times more. But all these metals – silicon, germanium, tin etc.- have severe problems. These include large expansion on alloying – up to 410% for silicon; restricted life span; complicated production methods; high cost and uncertain safety.

Processing of Natural Graphite for Use in Lithium Ion Cell Anodes

Mining

Flotation

Drying

Classification

Pulverisation 10 – 50 microns

Spheronisation

Purification 99.9-99.99%

Coating

Synthetic graphite from needle coke

Production of Synthetic Graphite for Use in Lithium Ion Cell Anodes

Extraction Oil from Ground (Wells or oil sands/shale)

Refining of oil

Recovery of still bottoms

Calcination in coking drum (450 deg C)

Graphitization to 99.9% (2800+ deg C)

Or 99.98% (3100 degrees C)

Pulverisation (10-50 microns)

Coating

Lithium ion versus other secondary cells

Voltage, volts Specific Energy, MJ/kg

Lithium ion 3.6 0.46 NiMH 1.2 0.36 NiCd 1.2 0.14 Lead acid 2.1 0.14

Cathode Material

Theoretical

Capacity

mAhr/g

Voltage

versus

Lithium

Expansion

% Safety Toxicity Cost

Cobalt Oxide 273 3.6 Poor Med High

NiCo Oxide 240 3.5 Good Med Med

Layered Mn Oxide 285 3.8 Very

Good Low Low

Iron Phosphate 170 3.2 Very

Good Low Low

Lithium Sulfide 1600 2.3 Poor Low Low

Comparison of Specific Capacity of Cathodes and Anodes

Lithium Anode Materials

Material

Theoretical

Capacity ,

mAhr/g

Expansion on

charging,%

Resistivity,

Ohm.m Cost,$/kg

Lithium metal 3860 na 9.28 x 10-8 ?

Graphite -

basal plane 372 10 2.5 – 5.0 x 10-6

Natural 10 Synthetic 20-40

Graphite –

Perpendicular

to basal plane

372 10 3.0 x 10-3 Natural 10

Synthetic 20-40

Silicon 4200 410 640 53

Tin 1500 260 1.09 x 10-7 20.40

Germanium 1600 300-400 0.46 1700

Aluminum 2234 90 2.82 x 10 -8 2.64

Comparison of Cathode and Anode Materials

High Energy Cell 100 A-

hr High Power Cell

10

A-hr

Material Price

$/kg Qty, g.

Cost/cell

$

% of

cost Qty, g.

Cost/cell

$

% of

cost

Cathode 55 1,408.6 77.47 48.8 64.8 3.56 28.2

Separator 180 60.5 10.89 6.9 16.4 2.95 23.3

Electrolyte 60 618.0 37.08 23.4 44.0 2.64 20.0

Graphite 30 563.6 16.91 10.7 12.7 0.38 3.0

Can & Vent 291.0 3.20 2.0 70.0 0.77 6.1

Binder 45 162.6 7.32 4.6 8.8 0.40 3.1

Copper 15 151.9 2.28 1.4 41.6 0.62 4.9

Aluminum 20 63.0 1.26 0.8 19.4 0.39 3.1

Carbon 20 46.4 0.93 0.6 2.2 0.04 0.3

Other 20 67.1 1.34 0.8 44.8 0.90 7.1

Total 3,432.7 158.68 100 324.7 12.66 100

Material Costs for Lithium Ion Cells (Argonne National Lab. ESD-2 May 2000)

Rough Estimate of 18650 Cell Manufacturing Costs (Argonne National Lab. ESD-2 May 2000)

Item Cost,$

Materials

Lithium cobaltate cathode 0.62

Separator 0.14

Electrolyte 0.30

Anode 0.24

Materials sub total 1.28

Overhead 0.15-0.25

Direct Labor 0.18-0.24

Total Manufacturing Cost 1.70 +/-

Targray’s Portfolio of Graphite Anode Active Battery Materials.

Product Series Characteristics

Discharge

Capacity

First

Efficiency

Design

Capacity/Fu

ll Cell

D50 BET Tap Density Compresse

d Density Applicable

System

mAh/g % mAh/g um m2/g g/cm3 g/cm3

High

performance

anode material

Compound natural

graphite, high

capacity, high first

efficiency, good

machinability

PGPT100 365.2 95.1 345-355 18-21 1.68 ≥1.15 1.60-1.65 SBR/PVDF

High performance

artificial graphite,

high capacity, high

rate capability,

good cycle/ safety

performance

PGPT200 338.52 94.5 325-335 23-27 0.92 ≥1.08 1.55-1.60 SBR/PVDF

PGPT202 340.3 94.5 325-335 13-17 2 ≥0.95 1.45-1.55 SBR/PVDF

Anode material for

power cell

High rate

capability material

PGPT300 343.1 93.9 325-330 20-24 1.68 ≥1.05 1.40-1.45 SBR/PVDF

PGPT301 343.2 93 320-325 13-17 2.09 ≥0.90 1.45-1.48 SBR/PVDF

Capacity-type

anode material for

power cell

PGPT350 327 90.2 295-305 22-26 4.8 ≥1.15 1.50-1.55 SBR/PVDF

PGPT351 342.4 90.8 320.33 21-25 5.2 ≥0.90 1.55-1.60 SBR/PVDF

Anode material

Modified natural

graphite, high

capacity, good

machinability

PGPT400 361.6 94.2 340-345 18-20 1.86 ≥1.10 1.58-1.62 SBR/PVDF

PGPT405 >355.3 >92.1 342-350 10.0-14.0 <3.0 >1.1 1.55-1.60 SBR/PVDF

Graphite

conductive

additives

PGPT501 350 83 3 9 20 10.8 0.4

Synthetic versus Natural Graphite as Anode

http://www.cpreme.com/EN/Pages/index.aspx

CPreme Product Selection Chart

Proposed Graphite Substitutes

The theoretical specific and volumetric capacities of various fully lithiated phases of electrochemically active metal elements. The volumetric capacity is calculated using the fully lithiated volume.

Notice that graphite compares poorly with all the alloying metals.

Proposed Graphite Substitutes In all this work, the effectiveness of the metal is diluted by the necessity for a carbon-based carrier and for the expansion chambers necessary to allow the metal to expand. The photomicrograph shows one such structure. Note the high void content.

Conclusions Graphite is the only viable anode material for lithium ion cells. Whether natural or synthetic is used will depend mainly on price. All alloying metals are too expensive and expansive and may not be available in sufficient supply to meet demands if EV production takes off as estimated