AN INDUSTRIAL PERSPECTIVE ON SUPERCAPACITOR...

AN INDUSTRIAL PERSPECTIVE ON SUPERCAPACITOR

CARBONS**

**Disclaimer: The views and opinions of the authors expressed herein do not state or reflect those of their employers

Lawrence Weinstein1 and Ranjan Dash2

1FlexEl LLC, 4505 Campus Drive, College Park, MD 207402SABIC, 475 Creamery Way, Exton, PA 19341

[email protected]

No. 1

ENERGY STORAGE MECHANISM:LIB vs. LIC vs. SUPERCAPACITOR

Faradaic

Current collector(Copper)

Anode(Graphite)

Cathode(LCO, NMC, etc.)

Electrolyte(LiPF6 in EC/DMC)

- +

LITHIUM ION BATTERY (LIB)

Li+

Current collector(Aluminum)

- +Li+

Dis

charg

eC

harg

e

Used in energydemanding applications

+-

Anode(Activated carbon)

Cathode(Activated carbon)

Electrolyte(TEATFB in AN)


SUPERCAPACITOR

NEt4+ BF4

-


+- NEt4+ BF4

-

v

Non-Faradaic

Used in power hungry

applications

+- Li+ PF6-

v

Cathode(Activated carbon)

+- Li+ PF6-

LITHIUM ION CAPACITOR (LIC)

Anode(Li pre-doped

graphite)

Electrolyte(LiPF6 in EC/DMC)

LIC combines Faradaic and

non-Faradaic reaction in a unit

electrochemical cell.

No. 2

CHARGE DISCHARGE PROFILE:LIB vs. LIC vs. SUPERCAPACITOR

LIB LIC Supercapacitor

Max. rated voltage 4.2 V 3.8 V 3.0 V(2.85 V for most cases)

Min. usable voltage (for most practical purposes)

3-3.3 V 2.2 V ~1.1 V

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Vo

ltag

e, V

Capacity / Time

Anode

Cathode

Cell

LITHIUM ION CAPACITOR

Usable Vmax

Usable Vmin

DischargeCharge

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Vo

ltag

e, V

Capacity / Time

Anode

Cell

LITHIUM ION BATTERY

Cathode

Rated voltage

DischargeCharge

0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

4.0

4.5

Vo

ltag

e, V

Capacity / Time

Cathode

Anode

Cell

SUPERCAPACITOR

Usable Vmin

DischargeCharge

Usable Vmax

No. 3

TYPICAL PERFORMANCE CHARACTERISTICS:SUPERCAPACITORS vs. LIBs & LICs

• Supercapacitors provide higher power than LIBs & LICs.

• Supercapacitors and LICs provide longer life than LIBs.

• Supercapacitors & LICs are safer than LIBs.

Characteristics vs. LIBs vs. LICs

Energy density

Max. rated voltage ~30% ~30%

Min. usable voltage (for most practical purposes)

~100% ~100%

Cell capacity

Energy density

Power density (max.)

Cycle life ~

Self discharge

Operating temperature range ~

Safety ~

No. 4

APPLICATIONS – SUPERCAPACITORS

Functionality

CE

Po

we

r to

ols

Sm

art

me

ters

Cra

nes

Win

dm

ill

bla

de

co

ntr

ol s

ys

Au

tom

ob

ile

s

(sto

p-s

tart

,

reg

en

era

tive

bra

kin

g, e

tc.)

Ra

ilw

ays

Pulse power

Energy backup

Energy harvesting

Fast charging

Consumer electronics Industrial Transportation

Supercapacitors have two sets of applications

• Long cycle life, high reliability – energy/power backups

• Quick charge-discharge - energy recovery/harvesting, pulse power, fast charging

No. 5

MARKET: LIBs vs. LICs vs. SUPERCAPACITORS

Lithium ion batteries

(LIBs)

Lithium ion capacitors

(LICs)

Supercapacitors

Market size (2015) ~$15 B <$ 0.1 B? <$0.5 B

CAGR (2010-2025) 10+% Aggressive growth expected. 10+%

No. of manufacturers High; >20 Low; <10 High; >30; too many players

Cost (cell level) $200-$300/kW-h High>$10,000/kW-h,

~$0.01/Farad

Geography

Mostly in Japan, China &

Korea; US gaining

momentum – Gigafactory

Mostly in Japan; Few

companies in US entering

market

Many countries/geography –

Japan, US, China, Europe

Market/applications

Today: mostly consumer

electronics (CE); Future:

aggressive growth in EVs

Today: mostly CE; Future:

CE, industrial and automotive

CE, industrial and automotive

• Supercapacitor sales are < 4% of LIBs today. LIBs still overwhelmingly dominant. Market of LIBs

predicted to grow aggressively – primarily because of EVs. "Electric vehicles to be 35% of global new car sales by

2040." - Bloomberg New Energy Finance, 2016.

• In the past 2 decades, the number of supercapacitor manufacturers increased at a rate much higher

than size of market (1998 – 4 manufacturers).

• LIC in market - taking market share from supercapacitors due to lower self discharge, higher energy

density and may take market share from batteries in niche applications

• Cost of LIC is currently higher than supercaps on cell level– largely due to manufacturing costs

References: Dennis M. Zogbi, Paumanok Publications, Inc, 2013 (www.ttiinc.com/object/me-zogbi-20130403.html); Christophe Pillot,

Avicenne Energy, Batteries 2014; Marc Reisch, C&EN, 2015

No. 6

PRELITHIATION PROCESSES: ELECTROCHEMICAL, CHEMICAL LITHIATION

• Ex situ electrochemical lithiation (not shown)

impractical due to handling issues

• Lithium metal main source of lithium, challenging

to work with• Need to limit amount of lithium in cell

• Thin lithium foil difficult to handle mechanically—

increases processing cost

• Lithium powder processing scaling may be expensive

• Chemically reactive—needs dry room

• Kinetics of lithiation, regardless of source, an issue for

production—WIP (Work in progress)

• Alternatives to lithium metal possible• Kinetics still potential issue

• Residue from precursor, voids in cathode possible

In situ electrochemical lithiation (auxiliary lithium

electrode)—most common todayIn situ electrochemical lithiation (other

source of lithium in cathode)

+- Li+ PF6- +Li+ PF6

-

+- Li+ PF6- +- Li+ PF6

-

Lithiated anodeLithium foil

Carbon anode

Chemical lithiation:

Lithium foilChemical lithiation:

Lithium powder

References: Yakovleva, IBA2013, Barcelona; W. Cao et al., J. Electrochem. Soc. 2017; Jeżowski et al. PRIME 2016, Honolulu

Lithium powder

No. 7

LIMITATIONS ON PERFORMANCE FOR LITHIUM ION CAPACITORS

Cathode(Porous carbon)

Limits energy

Anode(Lithiated

graphite)

Limits power

Lithiated graphite has a

much higher specific

capacity than activated

carbon. High energy

density porous carbons

have been developed for

supercapacitors in the

past.

No. 8

TYPES OF CARBONS EXPLORED FOR USE IN SUPERCAPACITORS

Endohedral

carbonsPlanar

Graphene

Exohedral

carbons

Carbon nanofibers

Carbon nanotubes

Carbon onions

Activated carbons

Activated carbon fibers

Carbide derived carbons

Polymer derived carbons

Templated carbons

Carbide derived carbon

10 nm

10 µm

References: Liu et al, Nano Lett. 2010; Singh et al, Scientific Reports, 2015; Dash et al, Micro. Meso. Matls., 2005

Carbon nanotubes

Despite over 15 years of active R&D, specialized (“advanced”) carbons have had limited commercial

success. Even today, most commercial supercapacitors use coconut shell activated carbon.

No. 9

VOLUMETRIC CAPACITANCE (Farads per cm3) IS MORE IMPORTANT THAN GRAVIMETRIC CAPACITANCE (Farads per gram)

Volume occupied by 2 different carbons having same

mass and surface area (~1,500 m2/g)

• Much research still focuses on gravimetric energy

density – weight easier to measure than volume

• Device capacity scales with volumetric capacity

• Combination of high bulk density and high porosity

(high surface area, microporous) is required for high

volumetric capacitance.

• Bulk density of carbons comes from dense carbon (skeletal)

structures.

• Coconut shells have higher bulk density than most other carbons

made from natural precursor.

• Carbide derived carbons provide higher porosity and also higher

bulk density, thereby leading to high volumetric capacitance (100

F/cc).

• Most graphene materials (not all) have low bulk density and thus

provides higher gravimetric but lower volumetric capacitance.

• To date, roughly maximum of roughly 2x performance

of coconut shell carbon seen for ‘advanced’ carbons on

a volumetric basis

References: Weinstein et al, Supercapacitor carbons, Materials Today, 2013; Dash et al, Batteries International, 2013

No. 10

Gantry crane

SIZE OF SUPERCAPACITORS vs. SIZE OF DEVICE IT POWERS

Sources: https://www.tecategroup.com/store/index.php?main_page=product_info&products_id=1226; Miller et al, Interface (2008);

http://evworld.com/focus.cfm?cid=255

Smart meters

Supercapacitor

size (approx.): 15 x

25 x 5 mm

Device size

(approx.): Ø6” x 1”

Start-stop application

Supercapacitor

In most applications,

supercapacitors are small

compared to what they power,

giving little incentive to reduce

supercapacitor size and

weight while increasing cost.

Lithium ion capacitor

advantages including

low self discharge provide

benefits beyond simply

increasing energy density.

No. 11

WHY “ADVANCED” CARBONS HAVE FAILED TO IMPACT THE MARKET

15%

10%

10%

65%

Cost of

Goods Sold

(COGS)

Sales &

Marketing

General &

Administration

Earning Before

Tax

0%

10%

20%

30%

40%

50%

60%

70%

20%

20% Carbon

5% Depreciation

15% Structural costs (labor,

maintenance, etc.)

45% Raw

material cost

Typical cost structure – supercapacitor manufacturer

Carbon represents ~20% of supercapacitor cost. Carbon’s cost contribution in supercapacitors is

higher than active material's cost contribution in LIBs.

The majority of commercial supercapacitors use purified coconut shell activated

carbon – price: $15 to $30/kg.• ‘Advanced’ carbons at best provide 2X performance (volumetric capacity) of coconut shell activated

carbon - price: $50/kg - $200/kg.

• An increase in capacitance is not linearly proportional to increase in acceptable selling price. A 2X

performance can justify a maximum of 30% increase in price except for markets that demand

premium performance.

• Cost comparable, higher performing (>2X) carbons will lead to decreased manufacturing costs and

may address markets that are currently served by alternate energy storage technologies.


25% Other materials

(separator, electrolyte,

current collector, etc.)

No. 12

COMMODITY ACTIVATED CARBONS VS. SUPERCAPACITOR CARBONS

Commodity activated carbons

• 200+ manufacturers. Known for

3,000+ years

• Market: ~$4 B; growing at 10%

CAGR

• Typical applications: water

purification, waste water

treatment, air purification.

Commodity activated

carbons

Supercapacitor

carbons

Raw material Coconut shells, wood,

nutshells, peat, lignite,

coal, resin, etc.

Coconut shells

Manufacturing

process

Control activation of raw

material. Well known

technology.

Proprietary process.

Process enables high

surface area and high

purity carbons.

Purity > 2 wt. % ash, can be as

high as 10 wt.%.

0.5 wt.% ash (Fe and

halogen content less

than 100 ppm)

BET surface

area

700 – 1200 m2/g >1,500 m2/g

Particle size Granular; > 300 µm Fine powder; < 44 µm

Pore size Micro (< 2 nm), meso (2-

50 nm) or macro (>50 nm)

– depends on precursor,

processing

Mostly microporous (< 2

nm)

Price <$4/kg. Depends on

market demand.

$15-$30/kg.

Supercapacitor carbon powders are highly porous (> 1,500 m2/g) and pure (≤0.5 wt.%

ash), with pore size under 2 nm.


No. 13

THINGS TO CONSIDER FOR NEW SUPERCAPACITOR CARBONS

Cost, cost, cost!!

• The supercapacitor carbon market is extremely cost sensitive. Limited market exists

for expensive carbons (>$50/kg) with small (<2X) performance improvement.

Natural vs. synthetic precursor

• Natural precursors are cheap. But it is not easy to control carbon properties and to

deliver high purity material. Purification process required.

• Cheap synthetic precursors (e.g. sugar) can be an attractive option.

• Consider raw material to final yield. Yield depends on various factors - precursor,

activation agent, activation conditions, etc.

Production technology

• Some preliminary cost estimates only include precursor costs. Equipment and tooling

costs can be much larger, but are harder to estimate for new processes.

• Scaling up a new manufacturing process can take 3-5 years. Leveraging existing

manufacturing processes can reduce risk.

• Consider technologies that can make materials with consistent properties.


An opportunity exists for cost-comparable alternatives. At $15/kg, supercapacitor grade

coconut shell activated carbons are 4 - 5X the price of commodity activated carbon.

LICs are currently using supercapacitor grade carbons. Need exists for tailored carbon

materials for LICs.

No. 14

POWER SOURCES FOR INTERNET OF THINGS

• Supercapacitors, lithium-ion capacitors attracting interest for internet of things. Integration with energy

harvesting, low power

• Competing with conventional chemistries. Primary lithium batteries used in long life devices where low

amounts of power over a long time are needed (e.g. toll tags) Primary batteries last the life of the device.

• Lithium ion, lithium primary nickel metal hydride batteries well established for small form factor cells-Supercapacitors, lithium ion capacitors high cost, low energy density devices, less familiar to electronics designers

• Initial entry of LIC, supercaps in Internet of Things will be into niche markets

Chemistry

Calendar

Life

(years)

Energy

density

Power

densityCycle Life

Self

Discharge

(Lower)

SafetyCost

(Higher)

Carbon-zinc 3 ●●◖ N/A N/A ●●●● ●

Alkaline 10 ●●● ●◖ N/A N/A ●●◖ ●◖

Lithium (primary) 10-20 ●●●● ●●● N/A N/A ●● ●●

Nickel-metal hydride 5-10+ ●●● ●●◖ ●● ●●●●* ●●◖ ●●●

Lithium-Ion 3-10+ ●●●◖ ●●● ●● ●●● ●◖ ●●●

Thin film lithium 10+ ●●● ◖ ●●●● ●●●● ●●●● ●●●●●

Supercapacitor 10-20 ● ●●●● ●●●● ◖ ●●◖ ●●●●

Lithium ion capacitor 10-20?? ●◖ ●●●◖ ●●●● ●●●◖ ●●◖ ●●●●◖

*For low self discharge nickel metal hydride cells

References: Zhan et al, J Mater. Chem. C, 2014; L. Reese, http://www.mouser.com/applications/supercapacitors-hero-automotive/

No. 15

POSSIBLE INITIAL NICHE—FLEXIBLE REPLACING FLEXIBLE BATTERIES

Flexible electronics have stringent safety

requirements

• Alkaline chemistries very hard to seal

without creep—cannot use here

• Supercapacitors, LICs seen as safer

than lithium-ion, lithium batteries.

• Drawbacks- lower energy density,

higher cost.

• Carbon-zinc often used for safety, but

limited to primary applications

Low power required for many applications, such

as sensing, wearables

• Enables supercapacitors, LICs as

viable power source.

Reference: Marc Reisch, C&EN, 2015; http://www.addisonmagazine.com/2015/09/tech-chic-wearable-technology/;

http://www.bluesparktechnologies.com/index.php/products-and-services/temptraq

Flexible and printed supercapacitors and LICs may

open up need for alternate carbons.

No. 16

CONCLUSIONS

• Supercapacitors, lithium ion capacitors, and batteries will continue to compete for market share.

• Despite over 15 years of active R&D, specialized (“advanced”) carbon have had limited

commercial use in double layer capacitors because of their high cost.

• Volumetric capacitance (Farads per cm3) is more important than gravimetric capacitance (Farads

per gram).

• In most applications, supercapacitors are small compared to what they power, giving little

incentive to reduce supercapacitor size and weight while increasing cost. The other major

advantage of lithium ion capacitor (low self discharge) will be important in determining the market

entry for ltihium ion capacitors.

• There is an opportunity in existing applications for lower cost supercapacitor carbons with similar

performance to today’s carbons. Cost comparable, high performing (>2X) carbons will lead to a

decrease in manufacturing cost and therefore can address markets that are currently served by

alternate energy storage technologies.

• Lithium ion capacitors provide higher energy density than traditional symmetric supercapacitors,

and lower self discharge. This comes at the expense of fabrication complexity due to the need to

lithiate the anode. Cost is a “moving target” due to potential manufacturing improvements.

• Flexible supercapacitors and LICs for the Internet of Things may increase the need for new

carbons and justify their higher cost

AN INDUSTRIAL PERSPECTIVE ON SUPERCAPACITOR...

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