Analyses of electrochemical impedance spectroscopy on thermally structurized polyacrylonitrile

Synthetic Metals, 41--43 (1991) 2953-2956

ANALYSES

OF

ELECTROCHEMICAL

STRUCTURIZED

O.

PAASCH,

DDR

IMPEDANCE

SPECTROSCOPY

ON

THErMAl t Y

POLYACRYLONITRILE

M.SCHWARZENBERG,

Zentra!institut PSF,

2953

fuer

- 8027

K.JOBST

arid L . S A W T S C H E N K O

Fe~.tkoerperph~sik

Dresder

u~d

Wet! s t o f f o r ~ c h ~ J n g ,

(F.R.G.)

ABSTRACT We

analysed

prepared Our

from

analysi~

including rent

impedance

spectroscopic

data

t h e r m a l ly

structurized

polacrylonitrile

uses

frequency

ascribed

several

especially

to

the

different

reduced

types

Z(i~

ranges.

Processes

elements

of

the

and

for

of

diagrams

Y/U)-

typical

p~rcJus e l e c ) r o d ~ - s (TSPAN) . i~

diagr~ms

f(~r o u r

petal]el

for

diffe-

material

resulting

equivalent

spectroscopy

(ErS)

c,r e

circuit.

INTRODUCTION Electrochemical established trodes

and

polymer of

for of

solid

electrodes

equivalent

[2~6].

for-

Here

arbitrariness

ments

of

specific

the for

electrochemical

electrolytes.

circuits

materials. the

impedance investigating

in

e.c.

But

one

(e.c.)

TSPAN

A!so

we

be

are

discuss

establishing can

results

should

which

an

were

avoid

an

I, n o w n

the

well elec ~n

uncritical

possibility

with

i~ at

published

well

appropriate

connected

[1,2]

processes

other

to

reducp

e.c.

processes

use

for

The

ele-

which

are

TSPAN.

MATERIAL Recently prepare

temperatures 800...1200 particle ter

of

a

special

TSPAN

with above

m2/g diameter

less

0379-6779/91/$3.50

than

thermal

high

700°C

is

obtained. 1...2 nm.

~m

The and

[7]

surface:

material

of 2~5

treatment

specific

with material

80%

of

Microscopically

the a

was For

developed

to

structurization

a

BET

is

a

pores

layered

surface

powder have

of

with a

structure

a

diamewith

© Elsevier Sequoia/Printed in The Netherlands

2954 three-dimensior~al 0.36

nm.

ture

Due

the

pared

In

surface

in

PC)

this

of

which

and

charge

[8].

The

TSPAN

[hart 5 w t %

a conductivity

results

PTFE

conductivity

are

into

the

reported

as

strucwith

were

about the

preagent.

I0 -I

S/cm

electrolyte

pores

on

about

devices

binding

of of

is

layered

electrodes

less

penetrates

the

storage

have the

distance

of

TSPAN

the

mate-

with

a

BET

in

the

m2/g.

IMPEDANCE

Fig.l.

surface for

than

paper

1100

ELECTROCHEMICAL In

with

interlayer

suited

F/cm 3

smaller

The

specific

well

electrodes

much

LiCIO 4

occurs.

high

is

compression

is

rial.

the

several

pressed

which (IM

of

by

dry

to

material

a capacity

The

]inks

a

typical

SPECTRUM EIS

Nyquist-Z- representation

(65

spectrum kl~z...l

for

TSPAN

mHz).

In

is

the

shown scale

used

in

-Z'?S1

"----t

160

~hf

80

Re ~IHz S

0 <~ R Fig.l.

EIS

~

i

,

BO R+Re spectrum

for

j _ 7'/i~-

TSPAN

Fig.l

one

electrolyte becomes

depressed For

lower

etc.

and

small.

a

Fig.2.

For

two

one

impedances

a

elements

we

also

requires

emphasize

ohmic

higher

as

known a steep

arrives Zlf

at

and

respectively.

two

resistance

further

frequencies Thus

behaviour,

lel.

identify

semi-circle

behaviour. with

can

a special

that

one

has

Re

the or

porous

for

the

analysis. to

use

R

in

curve

e.c.

low

and

behaviour As

several

since

with

the

with

text

leads,

for

~ IHz

resembles

fractal

indicates

overall

detailed

Fig.l.

connected

from

the

for

described

resistance

increase

I

Zif

e.c.

frequencies

Zhf

The

I R

elements

Z''

I'~

a

electrodes.

a

capacitive

shown

in

high

frequency

of

pointet diagrams

the out in

Fig.2

latter in

[9]

paral-

2955 MET~!ODICS (a)

We

assume

and

constar~t

or

serial

shows in

the

coni~ection

In(

curves

dependences

has

an

of

R,

Re (e)

Im

~ -I

of

since

a series

examples

HIGH

such

the the

the

an

hf

ranges.

fractality be

LOW

FREQUENCY

of

between

will

be

C and

shown

iT

one

has

to

Zlf,h f

or

One

Im ~

(Z'UJ I i n d i c a t e s

and

Characteri=

represent

Y'/OO~

CPE)

and

the

Z C p R.

Z'OO~

occurence Only

a

few

below.

values Yhf

=

Zex p one

(Zex p

plot

from

deduce

the

occur

three

obtains

- Re)-i which

according

- I/R.

Fig.~

according

hf-e.c,

shown

clearly

to

in

to shows

the

Fig.4.

distinct

preThis

frequency

Cdt

I

layer the with

Fig.4.

plot

confirm

this

e.c.

capacity. material

and

its

at

h~

Cdl

ZCPE, a

adsorption

Z CPE,o

Ca

O.b 5-- Y7"0"1

may

serial

the

-- e . c .

can

be

interpreted

arise

from

connection

extremely

with

large

as

porosity Ca

surface.

BEHAVIOUR frequencies

one

Ylf

Zlf I shows

=

Y'/~

to

are

(d)

ZCPE,o

plots

hence

Y'if/~

there

- Nyquist

connected

has

can

I

double

low

(c)

representation

combinations. way

two

diagram

~hf

- Y

or

For

(also

).

(C)

parallel

( Y~Yhf) !

can

as

IkH

Other

usual

= F(~ one

connection

Nyquist

one

since

i

Fig.3.

' )

in

worthful

Any

Nyquist

,Z'

appropriate

of

Y-

capacitie~

(b)

elements

Z ~- o r

only

such

analysis

//x

00

an

experimental

0.05 -Y211-I

the

in

,Z'

(R),

occur.

these

the

seen

Especially

admittance

possible

' , IZI

will

BEHAVIOUR

section

0.01

,Y'

of

in

different

corresponding

ceeding

two

often

(parallel)

of

From

,Y'

resistances

(ZcPEI

of

a maximum

FREQUENCY

Fig.2

IYI

alone.

ohmic

behaviour

are

overlap

substract Ylf,hf

only

elements

a different

stic

is

that

phase

Zlf

(Fig.5).

composition into

=

Zhf

Zex p -

is

large

(R + R e ) .

a characteristic This

curve

shows

compared The

behaviour a

to

R

(Fig.2)

corresponding which

two-peak

two c u r v e s c o r r e s p o n d i n g t o

is

best

structure.

Ci

-

and

admittance

ZCPE, i

seen Its

in de-

( i = l , 2)

2956

co/ Q

/ BmHz

f--3

Zw

0.2

II

Ztf 0.1

/',,, /

"-..lwl I

"~-

/I

1.6 ~/00

according series

f/mHz

decomposition

connections

The

already this

(maxima

resulting discussed

material

and

e.c.

in ~")

if

- e.c.

by

two

et

also

ionic

a diffusional

shows

in F i g . 6 .

al.

[4,5]

in T S P A N

relaxation

or

in

addition

the d i f f u s i o n a l

is s h o w n

by T a n g u y

therefore

characterized chains

Fig.6.

to F i g . 6 .

f r e q u e n c i e s the occurrence of Z W,

I -

"~

160

a~d i t s

II F-'3 C2 ZCpE,2

\ ~I~ -

16

Fig.5.

C ~ ZCPE, I

\

",,.

r---]

mass

that

polypyrrole.

doping

processes

transport

lowest

Warburg c o n t r i b u t i o n It r e s e m b l e s

for

the

at

process at

the

one

As

in

will

be

polymer

phenomenon.

REFRENCES 1

J.R.

Macdonald

Sons,

NY,

2

Electrochemical

3

N.

Mermilliod,

133

(1986)

First

4

Int.

and

5

J.

Tanguy

and

6

G.

7

8

Paasch,

K.

Jobst,

M. M. M.

in L.

and

F.

John

Wiley

&

Extended

Abstracts,

France,

22--26 M a y , 1 9 8 9 .

Petiot,

J.

Electrochem.

Sot.,

Hoclet,

E.

in

Sawtschenko

and

M.

Sawtschenko, R.

Wolf

Forum.

in

[2],

CI.8.

C8.15.

K.

Forum.

Brackmann,

Zoltowski,

[2],

Mat.Science

L.

Jobst,

preprint.

Schwarzenberg,

Forum.

P.

Spectroscopy,

Bombannes,

Tanguy

Slama,

K.

Mat.Science

9

J.

Mat. S c i e n c e

Paasch,

Spectroscopy,

1073.

Tanguy

publ.

Impedance

Impedance

Symposium,

J.

be

(Ed.),

1987.

Jobst

and

L.

Schwarzenberg

M. and

Sawtschenko,

, to

Schwarzenberg, D.

Fehrmann,

L.

be

to

publ.

in

Wucke],

8.

to be

publ.

in