New Polymeric Proton Conductors for

High Temperature Applications

John Kerr, Xiao-Guang Sun, Gao Liu, Jiangbing Xie and Craig Reeder

Lawrence Berkeley National Laboratory,MS 62R0203, 1 Cyclotron Road,

Berkeley CA, 94720jbkerr@lbl.gov

Outline

• Background– Solid Polymer vs. Gel Polymer Ion Transport– Lithium ion transport vs. Proton transport.– Common features for Lithium Polymer batteries

and PEMFC’s.• Polymer design & Synthesis.• Preliminary Results• Future schedule and testing development

Liquids vs. Gels vs. Dry PolymersTransport mechanisms differ

(blue: polymer chain; red: cross-linker; black: solvent)

Li+

Li+

Li+

X-

X-

X-

One or both ions are solvated by polymer.Ions move due to segmental motion ofpolymer. Need 850C for EV performance

Dry Polymer – Li Metal/polymer &Fuel Cells –High Temp PEM (1500C)Gel Polymer – Li Ion and Fuel Cell

Li+

Li+

Li+

X-

X- X-

Network Backbone may be polymer or inorganic. Free liquid moves with ions. Operates at ambient temp.

Anions may be tethered to polymer backbone by means of side chains.Molecular structure determines morphology and properties.

Fuel Cell MembranesMicroscopic to Macroscopic

Anions tethered to polymer. Cations (H+, Na+)are mobile and solvated by water. Molecular structure determines morphology and formation of ionic, water-rich clusters.

Fuel Cell Composite Electrodes.

O2

Current collector

X-

X-

X-

X-

X-

X-

X-

X- X-

H+

H+

H+

H+

H+

H+

Nafionmembrane

O2H+

Carbon electrode particles

= conductingcarbon particle

Gas Phase •Transport of gases and ions through crowdedpolymer-solid interfaceswhere the electrolyte mobility is restricted.• Polyelectrolytes close to glassy phase in presence of electrode surfaces.•Poor ion transport and dis-bondment.•Ion activity?

Composite Electrodes in Li Ion CellsLithium ions in crowded neighborhoods

Cur

rent

col

lect

or

Carbon/graphiteparticles for intercalation

Li+

Li+

Li+

Li+

Li+Li+

Li+

Li+

Li+X-

X-

X-

X-X-

X-

Cur

rent

col

lect

or

separatorAnode Cathode

Ions plus solvent (EC/DMC, DME) – Unstable!Leads to gas generation and polymer formation

= cathode particle= Conducting carbon particle

Mechanisms of Ion Mobility in “Dry”Polymers - Amorphous Phase

O

O O

O

OO

O

O Li+Li+

Arrhenius Control-related tosolvation

O

Controlled by Segmental Motion- related to glass transition temperature, Tg

New Polymer Architectures for ImidazoleSolvating groups, Anion Mobility and

Flexibility

O

F2C

SO2

N

SO2

F3C

O O

O

N

N

O

O

N

N

O

O

n

bdo

n

pdo

nn

pdo bdo

Imidazole H+ solvating group

Imide Anion

H+

•Attach anions and solvatinggroups by grafting –control nature and concentration.•Use nature (pdo/bdo) and length of side chainto control chain mobility.•Backbone (PE, polystyrene,polysiloxane) and cross-linkdensity to control mechanical & morphological properties.•Degradation results in Release of small fragments- facilitates failure analysis.

Imidazole Proton Conductivity

Grotthus Proton Transfer?

Oxygen Separation Membraneexhibits stability to (per)oxygen

•Vinyl Imidazole used rather than vinyl pyridine.•PolyvinylImidazole has highTg. Membrane is very selectivefor O2 over N2.

Hiroyuki Nishide,* Yukihiro Tsukahara, and Eishun Tsuchida, J. Phys. Chem. B, 102 (44), 8766 -8770, 1998.

Hydrosilylation Chemistry Allows Grafting of Functions (Anions or Imidazoles) and Cross-

linking for Mechanical Properties.O

O

O

x yX-link catalyst

OO

O

x y

X

OO

O

y x

Graft Reaction

X O

C(SO2CF3)2

Li

OO

O

x y

Single-Ion ConductorX-Linked Network- may link different polymers to stabilize blends for cost savings

X OC(SO2CF3)2

Li

))))

))

))

((( (

((

((

-allyl groups are reactive centers in this chemistry.-Hydrosilation is reproducible, provides better uniformity and leaves no residues. -Allyl groups do not react with radical initiators

HSi Si

HX =

Prepolymers and Salts

OB

O

O

OO O

OO

Li+

SO2CF3

SO2CF3Li +

OSO3Li+

F F

FFFF

F F

Salt I

Salt II

Salt III

*O

O*

O

O

O

O

O

O

O

O

x

Prepolymer

OO SO3Li+

OO

OO

SO3Li

O O SO3Li

Salt IV

Salt V

Salt VI

y

CH2=CH-CH2-O-CF2-CFH-O-CF2-CF2-SO2N(Li)SO2CF3

CH2=CH-CH2-O-CF2-CFH-O-CF2-CF2-SO3(Li)

New salts arriving from DesMarteau Group (Clemson)

Conductivity of Li+

Polyelectrolytes

-9

-8

-7

-6

-5

-4

2.6 2.8 3 3.2 3.4 3.6 3.8 4

Ionic Conductivity of Comb-branch SIC as a Function of Temperature

SIC-25SIC-45SIC-80

1000/T (K-1)

•Theoretical modelspredict optimumion concentrationto be half the optimum for binarysalts.(Ratner JES 148,A858 (2001))

•Low salt concn. giveslower cost pathway.•Lower Tg at higherion concn. wanted forhigh conductivity. •Side chain lengths and flexibility not optimized.Tg: 80 = -54oC; 45 = -53oC; 25 = -35oC

Synthesis of Prepolymers & SaltsCl O

OO OH O O OOa

b

O O OHO O OO2

O O OH2

b

Cl OO

a

Cl OO

aO O O

O3

b

O O OH3

Cl

cO O4

O O2O OH

2

Cl

c

O O4

O O2

+K tert-Butoxide

OO

O

O

O

O

O

O

O

O

x

PETMO4

Note: a. NaOH/H2O (50/50), tetrabutylammonium hydrogen sulfate (THS), Toluene b. Methanol, H2O, HCl c. NaOH/H2O (50/50), THS

65oC

ICF2CF2OCF2CF2SO2F O

O+

Benzoyl peroxide

O

O

IO

SO2F

F F

F F F F

F F

Zn

OSO2F

F F

F F F F

F F OSO3Li

F F

F F F F

F F

LiOH

Salt III

OOH

Cl OO

OO

O O

H+

OO

OHOO

ClSOCl2

Na2SO3

OO

SO3Na OO

SO3Li

Salt IV

1. Ion exchange

2. LiOH

NaOH/H2O, catalyst

Conductivities of Lithium Polyelectrolytes

2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4-9.5

-9.0

-8.5

-8.0

-7.5

-7.0

-6.5

-6.0

-5.5

-5.0

-4.5

100oC 25oC

Log σ

/ S.c

m-1

1000 / T ( K -1)

Methide LiBAMB C2F4OC2F4SO3Li E4SO3Li E2SO3Li TMO2SO3Li

2.4 2.6 2.8 3.0 3.2 3.4 3.6 3.8 4.0 4.2 4.4

-9.5

-9.0

-8.5

-8.0

-7.5

-7.0

-6.5

-6.0

-5.5

-5.0

-4.5

DSC results of PETMO4 based single ion conductors

-79.0154C2F4OC2F4SO3LiPETMO4-40

-78.0652MethidePETMO4-40

-79.5954TMO2SO3LiPETMO4-40

-78.7256E4SO3LiPETMO4-40

-79.0754E2SO3LiPETMO4-40

-86.770----PETMO4-40

-78.5348LiBAMBPETMO4-20

-85.660---PETMO4-20

Tg/oCO/LiSaltPrepolymer

Uniformity of the Membrane is Critical!Rheology(DMTA) and AFM probe Membrane Properties and Uniformity – PEPE3+ 10% AGE

-100.0 -50.0 0.0 50.0 100.0 150.0105

106

107

108

109

10-2

10-1

100

101

Temp [°C]

E

' ()

[dy

n/cm

2 ]

E"

()

[dy

n/cm

2 ]

tan_delta ()

[ ]

PEPE3_Silane-X_Tg_third

2nd Tg

Tg

Rapid growth of dendrites observed in Li/Li cells – due to thick membrane (400µm), high x-link density that degrades

transport properties and non-uniformity from non-random polymer

Comb Structures allow Increase of Mechanical strength without Loss of Ion transport Properties?

PEPE3 (no salt) with different amount of crosslinker

-120.0 -104.0 -88.0 -72.0 -56.0 -40.0 -24.0 -8.0 8.0 24.0 40.00.0

0.5

1.0

1.5

2.0

2.5

Temp [°C]

tan

_del

ta (

)

[ ]

-120.0 -104.0 -88.0 -72.0 -56.0 -40.0 -24.0 -8.0 8.0 24.0 40.0104

105

106

107

108

109

1010

Temp [°C]

E

' ()

[dy

n/cm

2 ]

Increase crosslinker

Increase crosslinker

Increase of X-link agent leaves fewer free allyl groups available to alter polymer morphology

PEPE3/LiTFSI 20:1 with different amounts of hydrophobic SiO2 R805 filler

-100 -80 -60 -40 -20 0 20 40 60 80 1000

2

tan

delta

Temperature (oC)

Increasing SiO2: 0, 5, 10, 20%

-100 -80 -60 -40 -20 0 20 40 60 80 100

0

2

tan

delta

Temperature ( oC)

Combine X-link Chemistry with fillers for Increased Mechanical Properties

Different Surface Interactions influence Polymer Mobility (Temperature Sweep in Compression (10Hz))Fumed SiO2 -A200 –OH hydrophilic groups

R805 – Octyl hydrophobic groups

-80.0 -53.333 -26.667 0.0 26.667 53.333 80.00.0

0.2857

0.5714

0.8571

1.1429

1.4286

1.7143

2.0

Temp [°C]

tan

_del

ta (

)

[ ]

X-PEPE3_LITFSI (20:1)

tan_delta no filler 5% hydrophobilc SiO210% hydrophobic SiO210% hydrophilic SiO2

-80.0 -53.333 -26.667 0.0 26.667 53.333 80.0104

105

106

107

108

109

1010

Temp [°C]

E

' ()

[dy

n/cm

2 ]

X-PEPE3_LITFSI (20:1)

E' no filler 5% hydrophobic SiO210% hydrophobic SiO210% hydrophilic SiO2

PEPE3copolymer with 20% AGE-LiTFSI (20:1). X-linked to 10% density.Note increase in Tg due to presence of salt (cf. X-link with no salt).

Single-ion Conductor Gels.Add solvent to increase Ion transport to

Useful Levels.

-12

-10

-8

-6

-4

-2

2.5 3 3.5 4

Ionic conductivity for PAE8.66

based single ion conductors

before and after plasticized with PC/EMC (1/1, v/v)

PAE8.66-g-E2SO3NaPAE8.66-g-E2SO3LiPAE8.66-g-E3SO3NaPAE8.66-g-E3SO3LiPlasticized PAE8.66-g-E2SO3NaPlasticized PAE8.66-g-E2SO3LiPlasticized PAE8.66-g-E3SO3NaPlasticized PAE8.66-g-E3SO3Li

Log σ/

S.cm

-1

1000/T (K-1)

25oC

-10

-9

-8

-7

-6

-5

-4

-3

-2

2.5 3 3.5 4

Ionic conductivity for PEPE3 based single ion conductorsbefore and after plasticized with PC/EMS (1/1, v/v)

PEPE3-g-E2SO3NaPEPE3-g-E2SO3LiPEPE3-g-E3SO3LiPEPE3-g-E3SO3NaPlasticized PEPE3-g-E2SO3NaPlasticized PEPE3-g-E2SO3LiPlasticized PEPE3-g-E3SO3NaPlasticized PEPE3-g-E3SO3Li

Log σ/

S.cm

-1

1000/T (K-1)

25oC

Imidazoles and Long Tethers good for Hydrogels- Heller

Imidazole provides stabilityand faster kinetics.Long tether provides faster diffusionand leads to order of magnitudeIncreas in current.

Hydrogels used for bionsensors,medical applications, etc.

New Opportunities for Old Technologies?

Organic &Polymer

ElectrochemistryLithium Batteries

FuelCell

Membranes

LED flat panelDisplays

IonExchange materials

biomembranes &biocatalysis

Environmental preservation &

remediation

Gasseparation

Biotechnology bioprocessing

sensors

Electric Vehicles- Transportation

Energy generation

Photo-voltaics

Electrochemi-luminescence

chemical manufacturing

Selective ChemicalSynthesis

Selective Membranes

Pharmaceuticals &Intermediates

Electro-chromic devices

SmartWindows -EnergyEfficiency

Ozone/peroxidegeneration

Biotechnologyfor the

Environment

New

EETD/LB

NL O

pportunitiesEs

tabl

ishe

d EE

TD/L

BN

L Pr

ogra

ms

Next Steps

• Prepare polyelectrolyte acid forms (usually from Na+ form)

• Measure “dry” conductivity, Tg-values and mechanical properties.

• Dope with imidazole, pyridine and water.– Measure conductivity, Tg and rheology.

• Examine polymer stability.• Attach Imidazole to polyelectrolyte and

measure properties.

Next Phase

• Optimize polyelectrolyte structure for transport– Concentration of imidazole, anions– Tether length and flexibility– Backbone and cross-linking

• Examine material properties with carbon filler for potential MEA construction.

• Develop more stability data.• Initiate development of structure-function

relationships

Acknowledgements

• DOE-LANL• NASA PERS program (Glenn Research

Center).• DOE Office of FreedomCAR and Vehicle

Technologies