Introduction to the field of Introduction to the field of polymer ionics: polymer ionics:

Definitions and historical developmentDefinitions and historical development

Prof. Dr. Agnieszka PawlickaProf. Dr. Agnieszka Pawlicka

SummarySummary

1.1. Introduction to the field of polymer ionicsIntroduction to the field of polymer ionics

1.1.1.1. Definition of polymers and conductivity Definition of polymers and conductivity 1.2. Definition of polyelectrolytes, polymer electrolytes, 1.2. Definition of polyelectrolytes, polymer electrolytes,

polymeric gelspolymeric gels1.3.1.3. Historical development Historical development1.4.1.4. Current state of art in the field of polymer Current state of art in the field of polymer

electrolyteselectrolytesPoly(ethylene oxide) systems, grafted, crosslinked, Poly(ethylene oxide) systems, grafted, crosslinked,

plasticized and composite systems;plasticized and composite systems;

1.5.1.5. Advantages and disadvantages of different Advantages and disadvantages of different systemssystems

What are polymers ?

Polymers are composts formed by an almost regular repetition of units (atomic groups) connected by chemical bonds which to form linear long chains or branched, or three-dimensional net (polymerization) .

Monomer

What is a polymer?What is a polymer?

What is a conduction?What is a conduction?

Conduction is the movement of Conduction is the movement of electrically chargedelectrically charged particles through a particles through a transmission mediumtransmission medium ( (electrical conductorelectrical conductor). ).

The movement of charge constitutes an The movement of charge constitutes an electric currentelectric current. .

The charge transport may result as a response to an The charge transport may result as a response to an electric fieldelectric field, or as , or as a result of a concentration gradient in carrier density, that is, by a result of a concentration gradient in carrier density, that is, by diffusiondiffusion. .

The physical parameters governing this transport depend upon the The physical parameters governing this transport depend upon the material.material.

Electrical conduction

Heat conduction or thermal conduction is the spontaneous transfer of thermal energy through matter, from a region of higher temperature to a region of lower temperature, and hence acts to even out temperature differences.

Topics to cover Topics to cover Metals, semiconductors, and insulators.Metals, semiconductors, and insulators.Band structure & electron conduction.Band structure & electron conduction.Electrical conductivity in metals.Electrical conductivity in metals.Semiconducting materials.Semiconducting materials.Conducting polymers.Conducting polymers. Ionic conduction & polymer electrolytes.Ionic conduction & polymer electrolytes.

Electrical Conductivity in MaterialsElectrical Conductivity in Materials

Metals: Metals: good conductors with electrical conductivity on the order of 10good conductors with electrical conductivity on the order of 1077 ΩΩ-1-1mm-1 -1 (10(105 5 S/cm) S/cm) Metallic bonding leads to a “sea” of electrons that are free to move around.Metallic bonding leads to a “sea” of electrons that are free to move around.

Insulators: Insulators: electricalelectrical conductivity ~ 10conductivity ~ 10-10-10 to 10 to 10-20-20 ΩΩ-1-1mm-1-1. . Ionic or strong covalent bonds where valence electrons are tightly bound Ionic or strong covalent bonds where valence electrons are tightly bound

(localized).(localized).

Semiconductors: Semiconductors: electricalelectrical conductivity ~ 10conductivity ~ 10-6-6 to 10 to 1044 ΩΩ-1-1mm-1-1. . Covalent (or predominantly covalent) bonds that are relatively weak Covalent (or predominantly covalent) bonds that are relatively weak

(valence electrons are not as tightly bound as in insulators).(valence electrons are not as tightly bound as in insulators).

Types of conductivity Types of conductivity electronic conductionelectronic conduction: motion of electrons and/or holes (in most solid : motion of electrons and/or holes (in most solid

materials).materials). ionic conductionionic conduction: motion of charged atoms and/or molecules.: motion of charged atoms and/or molecules.

Metals, Semiconductors and InsulatorsMetals, Semiconductors and Insulators

Electrical ConductionElectrical Conduction

Free electrons needed for electrical conduction (applied electric field is sufficient to generate large number of free electrons).

METALS

SEMICONDUCTORS OR INSULATORSDue to the band gap, much more energy input is necessary to create charge carriers (electrons in conduction band or holes in valence band).

Fermi levelFermi level Fermi level" is the term used to describe the top of the Fermi level" is the term used to describe the top of the

collection of electron energy levels at absolute zero collection of electron energy levels at absolute zero temperature. temperature.

This concept comes from This concept comes from Fermi-Fermi-DiracDirac statistics statistics. . Electrons are Electrons are fermionsfermions and by the and by the PauliPauli exclusion principle exclusion principle cannot exist in identical energy cannot exist in identical energy states. So at absolute zero they pack into the lowest states. So at absolute zero they pack into the lowest available energy states and build up a "Fermi sea" of available energy states and build up a "Fermi sea" of electron energy states. electron energy states.

The Fermi level is the surface of that sea at absolute The Fermi level is the surface of that sea at absolute zero where no electrons will have enough energy to zero where no electrons will have enough energy to rise above the surface. The concept of the Fermi rise above the surface. The concept of the Fermi energy is a crucially important concept for the energy is a crucially important concept for the understanding of the electrical and thermal properties understanding of the electrical and thermal properties of solids. of solids.

Both ordinary electrical and thermal processes involve Both ordinary electrical and thermal processes involve energies of a small fraction of an electron volt. But the energies of a small fraction of an electron volt. But the Fermi energies of metals are on the order of electron Fermi energies of metals are on the order of electron volts. volts.

This implies that the vast majority of the electrons This implies that the vast majority of the electrons cannot receive energy from those processes because cannot receive energy from those processes because there are no available energy states for them to go to there are no available energy states for them to go to within a fraction of an electron volt of their present within a fraction of an electron volt of their present energy. Limited to a tiny depth of energy, these energy. Limited to a tiny depth of energy, these interactions are limited to "interactions are limited to "ripples on the Fermi searipples on the Fermi sea". ".

Although the Fermi function has a finite value in the gap, there is no Although the Fermi function has a finite value in the gap, there is no electron population at those energies (that's what you mean by a electron population at those energies (that's what you mean by a gap). The population depends upon the product of the Fermi function gap). The population depends upon the product of the Fermi function and the and the electronelectron densitydensity ofof states states. So in the gap there are no . So in the gap there are no electrons because the density of states is zero. In the conduction electrons because the density of states is zero. In the conduction band at 0K, there are no electrons even though there are plenty of band at 0K, there are no electrons even though there are plenty of available states, but the Fermi function is zero. At high temperatures, available states, but the Fermi function is zero. At high temperatures, both the density of states and the Fermi function have finite values in both the density of states and the Fermi function have finite values in the conduction band, so there is a finite the conduction band, so there is a finite conductingconducting populationpopulation. .

The Fermi function f(E) gives the probability that a given available electron energy state will be occupied at a given temperature. The Fermi function comes from Fermi-Dirac statistics and has the form

Electrical conduction in Electrical conduction in SemiconductorsSemiconductors

Bonding and band gap

StructureStructure m.p. (K)m.p. (K) EEgg (eV) (eV)

C (Diamond)C (Diamond) DiamondDiamond 37733773 5.55.5

SiSi DiamondDiamond 16831683 1.11.1

GeGe DiamondDiamond 12101210 0.70.7

•Need to create free electrons (or holes) for electrical conduction.• The smaller the band gap, the less energy is required to create charge carriers.

Conductivity of “intrinsic” (undoped) semiconductors:

kT

Egexp Conductivity increases with T.

What is a conducting polymer?What is a conducting polymer?

•Conjugated polymers: long π conjugated systems; •Energy states related with structural defects •Defects are caused by alterations in the molecular geometry and in the charges distribution.

What are conducting polymers ?

Quasi-particles doping

Delocalization

OBS: The carriers not are electrons neither holes localized in the interior of bands but are charged defects, localized long the polymeric chain.

Conjugated Polymers: Organic semiconductors with -bonds delocalizing along the polymer chain

“Conjugated Polymers”“Synthetic Metals”

go

QuasiQuasi-particles-particles The use of term quasiparticle seems to be ambiguous. The use of term quasiparticle seems to be ambiguous.

Some authors use the term in order to distinguish them from real particles, others to Some authors use the term in order to distinguish them from real particles, others to describe an excitation similar to a single particle excitation as opposed to a collective describe an excitation similar to a single particle excitation as opposed to a collective excitation. excitation.

Both definitions mutually exclude each other as with the former definition collective Both definitions mutually exclude each other as with the former definition collective excitations which are no "real" particles are considered to be quasiparticles. The problems excitations which are no "real" particles are considered to be quasiparticles. The problems arising from the collective nature of quasiparticles have also been discussed within the arising from the collective nature of quasiparticles have also been discussed within the philosophy of science, notably in relation to the identity conditions of quasiparticles and philosophy of science, notably in relation to the identity conditions of quasiparticles and whether or not they should be considered "real" by the standards of, for example, whether or not they should be considered "real" by the standards of, for example, entity realismentity realism..

Phonons are the quanta of classical sound waves and sound waves do not need the Phonons are the quanta of classical sound waves and sound waves do not need the notion of atoms. notion of atoms.

MagnonsMagnons are the quanta of classical spinwaves, which also do not need elementary are the quanta of classical spinwaves, which also do not need elementary spins. spins.

PhotonsPhotons inside an isolator are the quanta of classical dressed electromagnetic waves inside an isolator are the quanta of classical dressed electromagnetic waves and do not need the notion of electrons for the definition of the refractive index. and do not need the notion of electrons for the definition of the refractive index. PlasmonsPlasmons are the quanta of the are the quanta of the plasma oscillationsplasma oscillations and they only need charge and they only need charge density and mass density and no electrons or ions. density and mass density and no electrons or ions.

PolaronsPolarons are the quanta of the oscillating polarization in a lightly doped are the quanta of the oscillating polarization in a lightly doped semiconductor and also do not need elementary charge or mass.semiconductor and also do not need elementary charge or mass.

eParticles in physics

Elementary particlesFermions:  Quarks: u · d · c · s · t · b • Leptons: e- · e+ · μ- · μ+ · τ- · τ+ · νe · νμ · ντ

Bosons:  Gauge bosons: γ · g · W± · Z0 

Other:  Ghosts 

Composite particlesHadrons:  Baryons(list)/Hyperons/Nucleons: p · n · Δ · Λ · Σ · Ξ · Ω · Ξb • Mesons(list)/Quarkonia: π · K · ρ

· J/ψ · ΥOther:  Atomic nuclei • Atoms • Exotic atoms: Positronium • Molecules

Hypothetical elementary particles

Superpartners: Axino · Dilatino · Chargino · Gluino · Gravitino · Higgsino · Neutralino · Sfermion · Slepton · SquarkOther: Axion · Dilaton · Goldstone boson · Graviton · Higgs boson · Tachyon · X · Y · W' · Z'

Hypothetical composite particles

Exotic hadrons:  Exotic baryons: Pentaquark • Exotic mesons: Glueball · TetraquarkOther:  Mesonic molecule

Quasiparticles Davydov soliton · Exciton · Magnon · Phonon · Plasmon · Polariton · Polaron

How good is the conductivity ofHow good is the conductivity ofpolymers, compared to metalspolymers, compared to metals

Electrolytes Electrolytes – short description– short description

Ionic conducting electrolytes with low Ionic conducting electrolytes with low electronic conductivityelectronic conductivity

Solids, liquids or elastomersSolids, liquids or elastomers

Liquid electrolytes – are preferred Liquid electrolytes – are preferred liquids with high viscosity due to the liquids with high viscosity due to the convenience or security convenience or security

Liquid ElectrolytesLiquid Electrolytes

Electric currents in Electric currents in electrolyteselectrolytes are flows of electrically charged are flows of electrically charged

atomsatoms ( (ionsions). ).

Classical example of NaClClassical example of NaCl if an electric field is placed across a solution of if an electric field is placed across a solution of NaNa++ and and ClCl––, the sodium ions , the sodium ions

will move constantly towards the negative electrode (anode), while the will move constantly towards the negative electrode (anode), while the

chloride ions will move towards the positive electrode (cathode). chloride ions will move towards the positive electrode (cathode).

If the conditions are right, If the conditions are right, redoxredox reactions will take place at the reactions will take place at the

electrode surfaces, releasing electrons from the chloride, and allow electrode surfaces, releasing electrons from the chloride, and allow

electrons to be absorbed into the sodium.electrons to be absorbed into the sodium.

Liquid electrolytesLiquid electrolytes Ionic charged species should be near the electrodes Ionic charged species should be near the electrodes

Desirable non reactive salts, whichDesirable non reactive salts, which

- easily form ions in the adequate solvents- easily form ions in the adequate solvents

- does not precipitate over the electrodes- does not precipitate over the electrodes

- stable during the photolise process- stable during the photolise process

For polymeric electrolytes are generally used PC with For polymeric electrolytes are generally used PC with LiClOLiClO44 (explosive during drying) which can be substituted (explosive during drying) which can be substituted

by LiBFby LiBF44

Choose of the electrolyte depend on the electrochemical Choose of the electrolyte depend on the electrochemical systemsystem

Classification of Solid ElectrolytesClassification of Solid Electrolytes

Solid Electrolytes

organic inorganic

Polymeric electrolytes

Polyelectrolytes

Macromolecules(PEO or PPO)with Li+ salts

Molecular masslow - liquids

intermediary - viscous liquidshigh – solidsalmost rigid

Polymers with ionic groups which

can give cations or receive cations

(PolyAMPS)have a groups

regular distributed along the chain

that give the protons

Different oxides(Cr2O3, Ta2O5);

Protonic andAnionic conduction

(high for H+

good for Li+)Better than organicdue to the stability

for fotolitic degradation

Inorganic Solid ElectrolytesInorganic Solid Electrolytes

P.M.S. Monk, R.J. Mortimer, D.R. Rosseinsky, Electrochromism:Fundamentals and Applications, VCH, Weinheim, 1995.

Inorganic electrolytesInorganic electrolytes

Significant resistance to the interphase Significant resistance to the interphase contact – problems with contactscontact – problems with contacts

Solution:Solution:

prototype of ECD with WOprototype of ECD with WO33

Subsequent evaporation (sputtering) of the thin Subsequent evaporation (sputtering) of the thin films one on the other films one on the other

ITO/counter electrode film/solid electrolyte/electrochromic film/ITOITO/counter electrode film/solid electrolyte/electrochromic film/ITO

- inconvenience – high price of the production- inconvenience – high price of the production

Other deficienciesOther deficiencies

Relative fragility – easy to brokenRelative fragility – easy to broken

Disintegration of the coatings due to the expansion Disintegration of the coatings due to the expansion and contraction of the electrode films during the and contraction of the electrode films during the

insertion and desinsertion of the ionsinsertion and desinsertion of the ions

Classification of Solid ElectrolytesClassification of Solid Electrolytes

Solid Electrolytes

organic inorganic

Polymeric electrolytes

Polyelectrolytes

Macromolecules(PEO or PPO)with Li+ salts

Molecular masslow - liquids

intermediary - viscous liquidshigh – solidsalmost rigid

Polymers with ionic groups which

can give cations or receive cations

(PolyAMPS)have a groups

regular distributed along the chain

that give the protons

Different oxides(Cr2O3, Ta2O5);

Protonic andAnionic conduction

(high for H+

good for Li+)Better than organicdue to the stability

for fotolitic degradation

PolyelectrolytesPolyelectrolytes

Chitosan is obtained from chitin (structural element in the exoskeleton of crustaceans (shrimps, crabs, etc.)

At least 50% of amino groups.

Chitosan is positively charged and soluble in Low acidic solution.

Biodegradable and biocompatible.

Classification of Solid ElectrolytesClassification of Solid Electrolytes

Solid Electrolytes

organic inorganic

Polymeric electrolytes

Polyelectrolytes

Macromolecules(PEO or PPO)with Li+ salts

Molecular masslow - liquids

intermediary - viscous liquidshigh – solidsalmost rigid

Polymers with ionic groups which

can give cations or receive cations

(PolyAMPS)have a groups

regular distributed along the chain

that give the protons

Different oxides(Cr2O3, Ta2O5);

Protonic andAnionic conduction

(high for H+

good for Li+)Better than organicdue to the stability

for fotolitic degradation

AdvantagesAdvantages Polymeric electrolytes can be formed in the form of Polymeric electrolytes can be formed in the form of

very thin films of large surface area giving high very thin films of large surface area giving high power levels (>100 Wdmpower levels (>100 Wdm-3-3))

Fiona M. Gray “Solid Polymer Electrolytes, Fundamentals and technological applications”VCH Publishers, 1991.

Solid Organic ElectrolytesSolid Organic Electrolytes

P.M.S. Monk, R.J. Mortimer, D.R. Rosseinsky, Electrochromism:Fundamentals and Applications, VCH, Weinheim, 1995.

NafionNafion Nafion® is a sulfonated tetrafluorethylene copolymer discovered in the late 1960s by

Walther Grot of DuPont de Nemours. It is the first of a class of synthetic polymers with ionic properties which are called ionomers. Nafion's unique ionic properties are a result of incorporating perfluorovinyl ether groups terminated with sulfonate groups onto a tetrafluoroethylene (Teflon) backbone. Nafion has received a considerable amount of attention as a proton conductor for proton exchange membrane (PEM) fuel cells because of its excellent thermal and mechanical stability.

The chemical basis of Nafion's superior conductive properties remain a focus of research. Protons on the SO3H (sulfonic acid) groups "hop" from one acid site to another. Pores allow movement of cations but the membranes do not conduct anions or electrons. Nafion can be manufactured with various cationic conductivities.

History of PE researchHistory of PE research

It was already established that It was already established that

polyethers can interract with polyethers can interract with

various salts and this properties various salts and this properties

was largely used in organometallic was largely used in organometallic

chemistrychemistry

In 1973 - dr. P.V.Wright described In 1973 - dr. P.V.Wright described

conducting properties of conducting properties of

poly(ethylene oxide)-salt systems poly(ethylene oxide)-salt systems

““without solventwithout solvent”.”.

Photos during - ISPE-2006, Foz do Iguaçú, BrazilPhotos during - ISPE-2006, Foz do Iguaçú, Brazil

Photos during - ISPE-2006Photos during - ISPE-2006Foz do IguaçúFoz do Iguaçú

Brazil Brazil

“The latter workers also observed that the dissolution of potassium iodide in poly(ethylene oxide) disrupts the crystallinity of the polymer producing an elastomeric material at room temperature.”

“We wish to report the preparation of crystalline complexes of sodium and potassium salts with poly(ethyleneoxide).”

Important observationImportant observation

“The work of Iwamoto et al. and the extensive studies

of alkali metal ion-cyclic ether complexes, indicate that

the ether oxygen atoms interact directly with the

cations and not with the anions as suggested by

Lundberg et al. in their solution study. Similarities in

the infra-red spectra of the poly(ethylene oxide)

complexes and the cyclic ether complexes suggest

that the cations may be similarly disposed towards the

oxygen atoms.”

P.V. Wright et al. POLYMER, 1973, Vol 14, November 589

Photos during Photos during ISPE-2004ISPE-2004MragowoMragowoPolandPoland

a.c. and d.c. a.c. and d.c. conductivity resultsconductivity results

1 cal = 4.186 J

ISPE-2004ISPE-2004Mragowo-Mragowo-

PolandPoland

M.B. Armand, in: Fast Ion transport in Solids, ed. W. Van Gool (North-Holland, Amsterdam, 1973)p. 665.

" ...but it is realistic to expect that in a near future a whole set of electrolytes will be available for either Li, Na or K. Especially thin film polymers will be suitable for an all solid state system, as a good contact is easily achieved with soft materials..."

In 1978 Prof. M. Armand showed the technological importance In 1978 Prof. M. Armand showed the technological importance of these new materials for storage energy devices.of these new materials for storage energy devices.

Interesting due to the reserach on lithium rechargeables Interesting due to the reserach on lithium rechargeables bateries, which can contain different films, also polymeric. bateries, which can contain different films, also polymeric. Others applications also can be possible.Others applications also can be possible.

Use of the alternative sources of energy as solar energy and Use of the alternative sources of energy as solar energy and wind, which generate the electricity. These need the low price wind, which generate the electricity. These need the low price and high eficiency energy storage systems.and high eficiency energy storage systems.

Photos during Photos during ISPE-2004ISPE-2004MragowoMragowoPolandPoland

Polymeric electrolytes historyPolymeric electrolytes history

D.Fauteux et al. Electrochim Acta, 40 (1995) 2185

New class of materialsNew class of materials

Polymeric electrolytes (solid polymeric electrolytes; Polymeric electrolytes (solid polymeric electrolytes; SPEs) are new class of solid state ionicsSPEs) are new class of solid state ionics

Differences between polymeric electrolytes and ionic Differences between polymeric electrolytes and ionic conducting materials as ceramics, glass, inorganic conducting materials as ceramics, glass, inorganic crystals:crystals:

a) Charge transport - below a) Charge transport - below TgTg

b) Conductivity values – 100-1000 times lower than b) Conductivity values – 100-1000 times lower than other materialsother materials

Flexibility of SPEsFlexibility of SPEs

Important due to the volume change Important due to the volume change

during the electrochemical cycling,during the electrochemical cycling,

Accommodation without physical Accommodation without physical

degradation of the interfacial contacts – degradation of the interfacial contacts –

frequently observed in crystalline or frequently observed in crystalline or

vitreous solid electrolytesvitreous solid electrolytes

Polymeric gelsPolymeric gels

Polymeric gels may exist in two distinct phases, swollen and collapsed states - the volume of gels can decrease as much as 1000 times.

Volume transition of gels occurs when the gels are stimulated by change of chemical or physical factors such as

temperature, solvent composition, pH, and electric field .

The ability of gels to undergo such significant but reversible changes in volume in response to a precisely programmed stimulus allows unique new systems to be made.

The number of applications based on volume phase transitions of polymeric gel increases continuously.

Applications include temperature-sensitive gels and glucosesensitive gels for controlled delivery insulin

systems [6], light triggered optical shutter [7], chemical sensors [8], and even an artificial pancreas [9].

In such application, the knowledge of the diffusion coefficient of ions and molecules as a fundamental measure of molecular mobility and electrostatic interactions is of great importance.

Physical Properties of Polymeric GelsJ. P. Cohen Addad (Editor) ISBN: 978-0-471-93971-9Hardcover324 pagesDecember 1995

Gel electrolytesGel electrolytes

Polymers containing a low-molecular-Polymers containing a low-molecular-weight fraction that assist ionic transport. weight fraction that assist ionic transport.

Current state of art in the field of Current state of art in the field of polymer electrolytespolymer electrolytes

PEO-based polymeric electrolytesPEO-based polymeric electrolytesModification of PEOModification of PEOOther polymers with PEOOther polymers with PEOConductivity of 10Conductivity of 10-2-2 S/cm S/cmTransparencyTransparencyGood adhesion to glass propertiesGood adhesion to glass propertiesNew saltsNew salts

Chemical and Physical Chemical and Physical modificationsmodifications

Grafted systemsGrafted systems PEO with other polymersPEO with other polymers PEO on other polymersPEO on other polymers

Plasticized systemsPlasticized systems Addition of plasticizersAddition of plasticizers PVA, Glycerol, Ethylene glycol, etc.PVA, Glycerol, Ethylene glycol, etc.

Composites-based systemComposites-based system Addition of nanoparticles of AlAddition of nanoparticles of Al22OO33, TiO, TiO22, SiO, SiO22 etc. etc. Addition of carbon nanotubesAddition of carbon nanotubes

Advantages and DisadvantagesAdvantages and Disadvantages

Low crystallinityLow crystallinityHigh conductivityHigh conductivityGood stabilityGood stabilityLow glass transition temperatureLow glass transition temperatureTransparencyTransparency