Lecture 12 Fast Ionic Conduction in Chalcogenide Glasses · PDF fileIonic Conduction in Chalcogenide Glasses Steve W. Martin Depp&ggartment of Materials Science & Engineering Iowa

L 12 I i li i 1 M d l fLecture 12 - Ionics applications 1: Models of Ionic Conduction in Chalcogenide Glasses

Steve W. MartinDepartment of Materials Science & Engineeringp & g gIowa State University of Science & TechnologyAmes, IA 50011

[email protected]

Ion Conduction in GlassI ti ( d ti ) i t i ll li it d i id l

100101 16

0014

0012

0010

0080

060

0

400

200

0Temperature (oC)

Glassy

Ion motion (conduction) is typically very limited in oxide glasses

10-410-310-210-110

Lithium battery operationTg

35Li2 O-30Li

2 SO4 -10(1

10-810-710-610-510 4 10(LiCl)

2 -12.5SiO2 -12.5B

2 O3

25Li2 O-25Al

2 O25L

dc (

-cm

)-

10-1210-1110-1010-910 2 O

3 -50SiO2

5Li2 O -75B

2 O3

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.010-1510-1410-1310

[email protected] Lecture 12: Models of Ionic Conduction in Glass 2

1000 / T (K-1)

Fast Ion Conduction in Glass

0

101 1600

1400

1200

1000

800

600

400

200

0Temperature (oC)

GlassyCrystallineTgTm-AgIFIC glasses can be

10-1

100 TgTmg

RbAg4I529.8Ag

2O-40.4(AgI

-NaAl11O1735LZ)-1

gmore than 1 million times more conductive!

10-3

10-2

4(AgI)2-29.8P

2O5

28.6Ag2O-42.8(AgI)

2-28.6MoO3

50Ag2 S-5GeS-45G

5Li2 O-30Li

2 SO4 -10(LiCl)

Li4 B

7 O12 Cl26.9L

25Li2 O-25A

ZrO2 -9%

Y2 O

3

dc (

-cm

5

10-4

0 GeS2

Cl)2 -12.5SiO

2 -12.5B2 O

3

9Li2 O-9(LiCl)

2 -64.1B2 O

LiAlSiO4

5Al2 O

3 -50SiO2

25Li2 O -75B

2 O

LiNbO3

0 5 1 0 1 5 2 0 2 5 3 0 3 5 4 010-6

10-5

3

O3

42 O3

3

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.01000 / T (K-1)

[email protected] 3Lecture 12: Models of Ionic Conduction in Glass

Li-ion Battery: The Most Common Li battery

C6 is a common anode t i l f Li i b tt i

e-

material for Li-ion batteries

The maximum capacity of graphite (LiC ): ~350Ah/kg

Li+e-

e-

graphite (LiC6): ~350Ah/kg

Li: ~ 4000 Ah/kgLi+

Li+e-

e-

e-

-

Li C6 Li CoOLi+ conducting C6 has good cycle-life,

e e-

LixC6 Li1-xCoO2co duct g

electrolyteAnode: LixC6 xLi+ + xe- + C6

Cathode: Li CoO + xLi+ + xe- LiCoO

But low capacity for new portable devices

Cathode: Li1-xCoO2 + xLi+ + xe LiCoO2


Anode and Cathode Combinations Determine the Energy Density of Lithium Batteries

Cathodes

Density of Lithium Batteries

Anodes

J.M. Tarascon, M. Armand, Nature, 414, 15 (2001) 359


Lithium Dendrite Formation in Li ion Batteries

Li metal

Non-epitaxial deposition of lithium after each cycle leads to the growth of uneven “fingers” or dendrites of lithiumuneven fingers or dendrites of lithium

Internal dendrites result in short circuits of the battery – heat and fire

[email protected] 6

M. Dolle et al. Electrochemical and Solid-State Letters, 5(12) (2002)A286

Lecture 12: Models of Ionic Conduction in Glass

Fast Ion Conduction in Glass

Can highly conducting glasses be used in Lithium g y g gbatteries To increase safety?

By mitigating lithium dendrite formation

To increase energy density? By enabling lithium metal (or similar high activity) anodes By enabling lithium metal (or similar high activity) anodes

To reduce cost? By simplifying design and using lower cost materials


Fast Ion (Li+) Conducting Sulfide Glasses-Ioni Ch l ogenide Gl ssesIonic Chalcogenide GlassesCharge Compensated Chalcogenide Glasses

Typical glass compositions Lithium salt + + glass former + additives

Lithium modifierLithium modifier

Mobile cations Glass structure Chemical/mechanical/Mobile cations Glass structure Chemical/mechanical/electrochemical durability

LiI + Li2S + SiS2 B2S3 GeS2 LiI + Li2S + SiS2, B2S3, GeS2 … LiI + Li2S + GeS2+ Ga2S3, La2S3, ZrS2…


Example: Structures of xLi2S +(1-x)GeS2 Glasses

385

340s (Ge-S-)s (Ge-S-Ge)

Raman

xLi2S + (1-x)GeS2

415374 (Ge-S-Ge)

(Ge-S-)IR

454

415340

0.5

0.55

x = 0.6

tens

ity (a

.u.)

446

0.55

x = 0.6

sorb

ance

(a.u

.)

0.0

0.3

0.40.45In

t

200 300 400 500 600 700

0.00.30.4

0.450.5A

bs

200 300 400 500 600 700Wavenumber (cm-1)

200 300 400 500 600 700

Wavenumber (cm-1)

Ge S

S

S

Ge S

S

S

S

Li+

Li+Ge

S-

S Ge SS

S-

S- S-

Li+ Li+

Ge

S-

S S-

S-

Li+

Li+

Li+Ge S

S-

S-

Li+

Li+

-SLi+

[email protected] 9

GeS4/2 (GeS3/2S)-

S SLi+ Li+

(GeS2/2S2)2-

Li Li

(GeS1/2S2)3-


Arrhenius Ionic Conductivity

100

101 1600

1400

1200

1000

800

600

400

200

0Temperature (oC)

GlassyCrystallineTgTm-AgI

10-1

10RbAg4I5

29.8Ag2O-40.4(AgI)

2-29 8P

-NaAl11O17

2

35Li2 O

ZrOm)-1

10-3

10-22 29.8P

2O5

28.6Ag2O-42.8(AgI)

2-28.6MoO3

50Ag2 S-5GeS-45GeS

2

2 O-30Li2 SO

4 -10(LiCl)2 -12 5

Li4 B

7 O12 Cl26.9Li

2 O-9

25Li2 O-25Al

2 O

O2 -9%

Y2 O

3

dc (

-cm

10-5

10-4

22.5SiO2 -12.5B

2 O3

-9(LiCl)2 -64.1B

2 O3

LiAlSiO4

2 O3 -50SiO

2

25Li2 O -75B

2 O3

LiNbO3

0.5 1.0 1.5 2.0 2.5 3.0 3.5 4.010-6

1000 / T (K-1)000 / ( )


Raman Spectra of NaI doped glasses

1-NBS451

yNaI+(1-y)[0.3Na2S+0.7(0.1Ga2S3+0.9GeS2)]

U ll lk li451

y=0.1

y=0.2

a.u.

)

Usually, alkali iodide (MI) resides in the

3740-NBS

331

y=0

0 2nten

sity

(a interstitials of glass structure network and

3-NBS390

y=0.1

y=0.2

y=0

yNaI+(1 y)[0 6Na S+0 4(0 1Ga S +0 9GeS )]

In network and causes no change in the glass

t k t t150 200 250 300 350 400 450 500 550

yNaI+(1-y)[0.6Na2S+0.4(0.1Ga2S3+0.9GeS2)]

Wavenumber (cm-1)

network structure

[email protected] Lecture 12: Models of Ionic Conduction in Glass

Relation of glass structure to ionic conduction

xNa2O + (1-x)SiO2Glass in 2-D

+ +

+

|E|+ +

++ +

BO

++

ergy

- +

NBO NBO

BO

-++1/rn

Es = Strain EnergyEc = Coulomb Energy

Ene Eact s Ec

r r

EC

ES

-e2/r


Ionic Conduction in Glass

= neZ N is the number density

eZ is the charge +1 most of

Calculation: Take:

22 3 eZ is the charge, +1 most of the time

is the mobility

n ~ 1022 M+/cm3

A-M Universities… ~ 10-9 (cm)-1 Oxide glass

Estimation: What are the units of n? What is the approximate

What is ? N-Z Universities… ~ 10-3 (cm)-1 Sulfide glassat s t e app o ate

magnitude of n for a glass? What are the units of eZ? What is it magnitude for Li+?

10 (cm) Sulfide glass What is ?

Compare Si What is it magnitude for Li ? What are the units of ?

What is the conductivity of a typical n doped Si?

What is ?


DC ion conductivity in glass

Arrhenius temperature dependence

xLi2O + (1-x)P2O5

Creation of non-bridging oxygens

“Mobile” lithium ions The higher the

concentration of Li2O, 2 ,the higher the conductivity Lower resistivity

Activation energy decreases with Li2Ocontent


S. Martin, C.A. Angell JNCS ’83

Chalcogenide Glasses have significantly higher conductivities

Salt doped lithium phosphate and thiophosphate glasses dc act


Relation of Glass Structure to Ionic Conduction

xNa2O + (1-x)SiO2Glass in 2-D

+ +

+

|E|+ +

++ +

BO

++

ergy

- +

NBO NBO

BO

-++1/rn

Es = Strain EnergyEc = Coulomb Energy

Ene Eact s Ec

r r

EC

ES

-e2/r


Mobility and Number Dependence of the Conductivity

RT

ET

TeZTnT actc exp)()()( 0

RT

EnTn c

o exp)( RT

ET sexp)( 0

RTT

T exp)(

EEenZ

Question: What are the magnitudes of E and E ?

RT

EET

enZT scc exp)( 00

[email protected] 17

Question: What are the magnitudes of ES(M) and EC ?


Short Range Order Models

Anderson-Stuart Model Assignment of Coulombic and Strain energy terms, EC + Es

“Creation” or Concentration versus Migration energy terms, EC + Es

Coulomb energy term, EC attractive force between cation and anion

2)(

1)(2/

2.

22.

ac

acstruct

ac

acacstruct

rreZZC

rreZZeZZC

For Li+ in a oxide and sulfide glass Homework, Take Cstruct / ~ 1

What are the approximate values of rc, rd, and ? What is the approximate magnitude of EC?


Short Range Order Models

Strain energy term - Es

“Work” required to “dilate” the network so large cations i tcan migrate

E G r rS c d ( ) /2 2

G Sh d l

Cation size affect on Strain Energy

40

50

G Shear modulusrc Cation radiusrd Interstitial site radius

10

20

30

40

E s

(kca

l/mol

e)

Jump distance0

10

0 0.04 0.08 0.12 0.16 0.2

Cation Radius (nm)

For Li+ in an oxide and sulfide glass Homework What are the approximate values of rc, rd, and ?What are the approximate values of rc, rd, and ? What is the approximate magnitude of [email protected] Lecture 12: Models of Ionic Conduction in Glass 19

Ion Conduction in Glass: Coulombically or Structurally Constrained?Constrained? Oxide glasses, Eact ~100 kcal/mole Sulfide glasses E t ~10 kcal/mole Sulfide glasses, Eact 10 kcal/mole Eact Es Ec

Are alkali cations coulombically, Ec , constrained?y c Weak Electrolytes like HOAc, kA ~ 1 x 10-5 ? Cations are only weakly dissociated

Are alkali cations structurally E constrained? Are alkali cations structurally, Es, constrained? Strong electrolytes like NaCl? Completely dissociated, Na+ Cl- ?


Models of the Activation Energy Both activation energies appear to be non-zero and contribute to the

total activation energy Anderson-Stuart1 model calculation

2/)( 2 dcS rrGE

2

)(12

.

ac

acstructC rr

eZZCE

x Na2O + (1-x)SiO2 Es (calc)kcal/mole

Ec (calc)kcal/mole

Eact(calc)kcal/mole

Eact2

kcal/mole11 8 11 7 66 9 78 6 68 111.8 11.7 66.9 78.6 68.119.2 10.9 62.3 73.2 63.729.7 10.0 56.1 66.1 59.7

Calculation shows that the Ec term is the larger of the two energy barriers.

Coulombically constrained?1 Anderson Stuart J Amer Cer Soc 1954


1 Anderson, Stuart, J. Amer. Cer. Soc., 19542 SciGlass 5.5, Average of many glasses


Alkali Radii Dependence of Strain and Coulomb Activation EnergiesActivation Energies

E 2

Es

Ec

(?)

?)

Ec ~ 1/rcEm ~ rc

2

A.U

.)

c

dom

inat

ed

omin

ated

(?

E s ,

E c (A

Es d

Ec d

o

0.0 0.5 1.0 1.5 2.0 2.5 3.0

Na+H+ (?) Cs+K+

Li+


rcation ()


Strong and Weak Electrolyte models

“Strong electrolyte” model suggests allcations are equally available for conductionconduction. Each cation experiences an energy

barrier which governs the rate at which it hops

“Weak electrolyte” model suggests only those dissociated cations are available for conduction

Dissociation creates mobile carriers Dissociation creates mobile carriers available for conduction

SE models suggests that EC + Esboth contribute, one could be larger or , gsmaller than the other

WE model suggests that Ec is the dominant term


Thermodynamic Models of Ionic Transport

Glass is considered as a solvent into which salt is dissolved

If dissolved salt dissociates strongly then glass is If dissolved salt dissociates strongly, then glass is considered a strong electrolyte

If dissolved salt dissociates weakly, then glass is considered a weak electrolyteconsidered a weak electrolyte

Coulomb energy term calculations suggest that the salts are only weakly dissociated, largest of the two energy terms

Migration energy term is taken to be minor and weaker function of compositionp

Dissociation constant then determines the number of mobile cations available for conduction, dissociation limited conductionlimited conduction


Weak Electrolyte Model, Ravaine & Souquet ‘80

1/2M2O + SiO4/2 3/2O-Si-O-M+ 3/2O-Si-O- …… M+

(U t d) (R t d b t U di i t d) (Di i t d)(Unreacted) (Reacted but Undissociated) (Dissociated)Kdiss = aM+ aOM- / aM2O

~ [M+][OM-]/aM2O = [M+]2/ aM2O [M ][OM ]/aM2O [M ] / aM2O

[M+] ~ Kdiss1/2aM2O

1/2 n

= zen zeKdiss1/2aM2O

1/2 ~ C aM2O1/2

l K N 2RT/4 + )log Kdiss ~ -Ne2RT/4 r+ + r-)

As r+, r- increase, Kdiss increases


As increases, Kdiss increases

AC versus DC Ionic Conductivity

> 1

10(

a.c.)

+

|E|

0 2 4 6 8 10103K/T

2 4 6 8 10 12log10(f/Hz)

log 1

+

Ener

gy y

x

10 K/T log10(f/Hz)

+

D.C. Conductivity A.C. Conductivity

r

Charles - Polarization/Diffusion Jonscher - Universal ResponseAnderson/Stuart - Coulomb & Strain Energies Ngai - Coupling TheoryMoynihan/Macedo - Debeye & Faulkenhagen Theory Moynihan - ModulusRavaine/Souquet Weak Electrolyte Dyre Power Law

Lecture 12: Models of Ionic Conduction in Glass 26

Ravaine/Souquet - Weak Electrolyte Dyre - Power LawMalugani- AgI Micro domains Funke - Jump Relaxation

[email protected]

AC ionic Conductivity in Glass

Connection to Far-IR vibrational modes Angell ‘83


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Lecture 12 Fast Ionic Conduction in Chalcogenide Glasses · PDF fileIonic Conduction in Chalcogenide Glasses Steve W. Martin Depp&ggartment of Materials Science & Engineering Iowa