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Lithium Ion Conductive Membranes Based on Co-continuous Polymer Blends

Munch Elmér, Anette LU (2005)
Abstract (Swedish)
Popular Abstract in Swedish

Polymerer är samlingsnamnet på långa molekylkedjor. Runt omkring oss i vårt dagliga liv är vi omgärdade av polymerer så som plaster, lim, fibrer och proteiner. Utvecklingen av många högteknologiska produkter är starkt beroende av polymera material. Grundläggande kunskaper om dem och deras egenskaper är därför viktigt.



I ett batteri kan många fördelar erhållas då den konventionella vätskeelektrolyten ersätts av en polymerelektrolyt. Exempelvis kan läckage undvikas och en unik frihet i designen av batteriets utformning erbjudas. Dessa elektrolyter har främst potentiell användning i litiumbatterier då vissa polymerer med elektrondonerande egenskaper effektivt kan lösa litiumsalter... (More)
Popular Abstract in Swedish

Polymerer är samlingsnamnet på långa molekylkedjor. Runt omkring oss i vårt dagliga liv är vi omgärdade av polymerer så som plaster, lim, fibrer och proteiner. Utvecklingen av många högteknologiska produkter är starkt beroende av polymera material. Grundläggande kunskaper om dem och deras egenskaper är därför viktigt.



I ett batteri kan många fördelar erhållas då den konventionella vätskeelektrolyten ersätts av en polymerelektrolyt. Exempelvis kan läckage undvikas och en unik frihet i designen av batteriets utformning erbjudas. Dessa elektrolyter har främst potentiell användning i litiumbatterier då vissa polymerer med elektrondonerande egenskaper effektivt kan lösa litiumsalter och transportera dess katjoner. Jontransporten underlättas av mikroviskösa rörelser som polymerkedjorna genomgår vid temperaturer över materialets glasövergångstemperatur. Av denna anledning är det fördelaktigt med ett mjukt material. Samtidigt har en polymerelektrolyt en dubbel uppgift i batteriet, nämligen att transportera litiumjonerna och att separera elektroderna fysiskt så att kortslutning kan undvikas. En ideal polymerelektrolyt bör således utöva en vätskas jonledningsförmåga samt den mekaniska stabiliteten av ett fast material. Detta är egenskaper som av naturen motsäger varandra och ett talande exempel på de multifunktionella egenskaper som kan krävas av ett polymert material i en industriell tillämpning.



I denna avhandling behandlas konceptet att använda samkontinuerliga polymerblandningar för att erhålla polymerelektrolytmembran som kombinerar jonledningsförmåga med mekanisk stabilitet. Arbetet beskriver preparering, karakterisering och egenskaperna hos tre olika system av litium-jonledande membran. Samtliga av dessa tre olika system framställdes från två olika polymera komponenter som dopats med ett litiumsalt. Den dominerade komponenten var ett saltlösande nätverk av polymetakrylat ympat med sidokedjor av polyeter eller polyeterkarbonat



Två olika typer av metakrylatmakromonomerer användes för att bilda det jonledande nätverket. I två av systemen användes poly(etylenglykol)metakrylat. Till det tredje systemet syntetiserades det en ny makromonomer, poly(etylenkarbonat-etylenoxid)metakrylat. Den andra komponenten i membranen var en linjär och mekaniskt stabil polymer som garanterade den dimensionella stabiliteten hos membranen. Två polymerer användes för denna funktion, en fluorerad semikristallin polymer, poly(vinylidenefluoride-hexafluoropropylen) samt poly(metylmetakrylat), en amorf polymer med en glasövergångstemperatur på 105 °C. Membranen framställdes i en procedur som involverade två steg. Först preparerades filmer från acetonlösningar av makromonomerer, linjär polymer, litiumsalt och en UV-aktivator. Detta följdes av polymerisation av makromonomererna genom belysning med UV-ljus.



Membranen hade en fasseparerad morfologi som gjorde att blandningskomponenternas egenskaper kunde kombineras effektivt. De fasta membranen nådde en jonledning strax över 10-5 S?cm-1 vid rumstemperatur och hade en önskvärd mekanisk stabilitet. När så kallade gelelektrolytmembran preparerades genom att inkorporera en vätskeelektrolyt i ett av membransystemet blev resultatet elastiska gelelektrolyter med en konduktivitet runt 10-3 S?cm-1 vid rumstemperatur.



De studerade membranen kan potentiellt användas som elektrolyter i olika elektrokemiska tillämpningar så som batterier, elektrokromiska fönster eller kemiska sensorer. Vidare erbjuder prepareringsmetoden en stor valfrihet för att preparera membran med kontrollerade egenskaper, tex. optisk klarhet, mekanisk stabilitet. En valfrihet som med fördel kan användas för andra typer av multifunktionella polymermembran. (Less)
Abstract
There is a growing need for multifunctional polymeric materials for the development of several important energy conversion technologies. For example, the polymer electrolyte is a key component in lithium polymer batteries. The basic functions of this electrolyte are to efficiently conduct the lithium ions and physically separate the electrodes. Consequently, these electrolytes should ideally possess the ionic conductivity of a liquid while retaining the mechanical stability of a solid.



In this thesis the concept of using polymer blends to obtain electrolyte membranes which combine ion conductivity and mechanical stability has been explored. The work comprises the preparation, characterisation and properties of three... (More)
There is a growing need for multifunctional polymeric materials for the development of several important energy conversion technologies. For example, the polymer electrolyte is a key component in lithium polymer batteries. The basic functions of this electrolyte are to efficiently conduct the lithium ions and physically separate the electrodes. Consequently, these electrolytes should ideally possess the ionic conductivity of a liquid while retaining the mechanical stability of a solid.



In this thesis the concept of using polymer blends to obtain electrolyte membranes which combine ion conductivity and mechanical stability has been explored. The work comprises the preparation, characterisation and properties of three different lithium ion conductive membranes based on co-continuous polymer blend systems. The blend systems were all prepared from two polymeric components which were doped with a lithium salt. The main component was a salt-dissolving polymethacrylate network grafted with polyether or polyethercarbonate side chains.



Two different kinds of methacrylate macromonomers were used in order to build up the graft copolymer structures. In two of the studied membrane types, poly(ethylene glycol) methacrylate macromonomers were used. In the third type, new polymeric building blocks, i.e., poly(ethylene carbonate-co-ethylene oxide) methacrylate macromonomers, were successfully synthesised via the anionic ring-opening polymerisation of ethylene carbonate. The macromonomers carried 30 mol% carbonate units in their structure. The minor component of the blends was a linear mechanically stable thermoplastic polymer which provided the dimensional stability. Poly(vinylidene fluoride-co-hexafluoropropylene) and poly(methyl methacrylate) were both investigated in this function. The electrolyte membranes were prepared by a two-step procedure, beginning with the solution casting of films of macromonomer, thermoplastic polymer, lithium salt and UV-activator. The methacrylate macromonomers were subsequently polymerised in-situ by UV-irradiation. The membranes were characterised by electron microscopy techniques, differential scanning calorimetry, Fourier transformation IR-spectroscopy, dynamic mechanical analysis, and electrochemical impedance spectroscopy to investigate the chemical composition, morphology, and the thermal, mechanical and conductive properties



The membranes exhibited different phase separated morphologies, which depended on the level of salt content and crosslinking, as well as on the nature of the blend components. The strategy of blending polymeric materials to combine ionic conductivity with dimensional stability proved effective. The solid polymer electrolytes reached conductivities just above 10-5 S?cm-1 at room temperature while exhibiting a satisfying mechanical stability. Subsequent gelling of the solid membranes, by incorporating a liquid electrolyte of lithium salt dissolved in gamma-butyrolactone, gave elastic polymer gel electrolytes which reached conductivities of 10-3 S?cm-1 at room temperature.



The studied membranes may potentially be used as electrolytes in different electrochemical devices such as lithium polymer batteries, electrochromic windows, and sensors. Applications which require different levels of, e.g., ionic conductivity, mechanical properties, and optical clarity, can take advantage of the quick and straight-forward membrane preparation process. It offers a platform to tailor membranes for different applications, including ion conductive membranes as well as other multifunctional materials. (Less)
Please use this url to cite or link to this publication:
author
supervisor
opponent
  • Professor Coqueret, Xavier, Laboratoire de Chimie Macromoléculaire, France
organization
publishing date
type
Thesis
publication status
published
subject
keywords
Polymerteknik, Polymer technology, biopolymers, conductivity measurements, in-situ UV-polymerisation, solution casting, poly(methyl methacrylate), vinylidene fluoride copolymers, poly(ethylene carbonate-co-ethylene oxide)methacrylate, PEG methacrylate macromonomers, heterogeneous polymer blends, polymer electrolyte membranes, lithium salt containing gels
pages
143 pages
publisher
Department of Polymer Science & Engineering, Lund University
defense location
Lecture Hall K:B the Centre for Chemistry and Chemical Engineering Getingevägen 60 Lund Institute of Technology
defense date
2005-11-30 10:30
ISBN
91-7422-097-7
language
English
LU publication?
yes
id
6aece074-3222-4bdd-8416-1cfe8ec40a37 (old id 545651)
date added to LUP
2007-10-13 12:47:34
date last changed
2016-09-19 08:45:12
@misc{6aece074-3222-4bdd-8416-1cfe8ec40a37,
  abstract     = {There is a growing need for multifunctional polymeric materials for the development of several important energy conversion technologies. For example, the polymer electrolyte is a key component in lithium polymer batteries. The basic functions of this electrolyte are to efficiently conduct the lithium ions and physically separate the electrodes. Consequently, these electrolytes should ideally possess the ionic conductivity of a liquid while retaining the mechanical stability of a solid.<br/><br>
<br/><br>
In this thesis the concept of using polymer blends to obtain electrolyte membranes which combine ion conductivity and mechanical stability has been explored. The work comprises the preparation, characterisation and properties of three different lithium ion conductive membranes based on co-continuous polymer blend systems. The blend systems were all prepared from two polymeric components which were doped with a lithium salt. The main component was a salt-dissolving polymethacrylate network grafted with polyether or polyethercarbonate side chains.<br/><br>
<br/><br>
Two different kinds of methacrylate macromonomers were used in order to build up the graft copolymer structures. In two of the studied membrane types, poly(ethylene glycol) methacrylate macromonomers were used. In the third type, new polymeric building blocks, i.e., poly(ethylene carbonate-co-ethylene oxide) methacrylate macromonomers, were successfully synthesised via the anionic ring-opening polymerisation of ethylene carbonate. The macromonomers carried 30 mol% carbonate units in their structure. The minor component of the blends was a linear mechanically stable thermoplastic polymer which provided the dimensional stability. Poly(vinylidene fluoride-co-hexafluoropropylene) and poly(methyl methacrylate) were both investigated in this function. The electrolyte membranes were prepared by a two-step procedure, beginning with the solution casting of films of macromonomer, thermoplastic polymer, lithium salt and UV-activator. The methacrylate macromonomers were subsequently polymerised in-situ by UV-irradiation. The membranes were characterised by electron microscopy techniques, differential scanning calorimetry, Fourier transformation IR-spectroscopy, dynamic mechanical analysis, and electrochemical impedance spectroscopy to investigate the chemical composition, morphology, and the thermal, mechanical and conductive properties<br/><br>
<br/><br>
The membranes exhibited different phase separated morphologies, which depended on the level of salt content and crosslinking, as well as on the nature of the blend components. The strategy of blending polymeric materials to combine ionic conductivity with dimensional stability proved effective. The solid polymer electrolytes reached conductivities just above 10-5 S?cm-1 at room temperature while exhibiting a satisfying mechanical stability. Subsequent gelling of the solid membranes, by incorporating a liquid electrolyte of lithium salt dissolved in gamma-butyrolactone, gave elastic polymer gel electrolytes which reached conductivities of 10-3 S?cm-1 at room temperature.<br/><br>
<br/><br>
The studied membranes may potentially be used as electrolytes in different electrochemical devices such as lithium polymer batteries, electrochromic windows, and sensors. Applications which require different levels of, e.g., ionic conductivity, mechanical properties, and optical clarity, can take advantage of the quick and straight-forward membrane preparation process. It offers a platform to tailor membranes for different applications, including ion conductive membranes as well as other multifunctional materials.},
  author       = {Munch Elmér, Anette},
  isbn         = {91-7422-097-7},
  keyword      = {Polymerteknik,Polymer technology,biopolymers,conductivity measurements,in-situ UV-polymerisation,solution casting,poly(methyl methacrylate),vinylidene fluoride copolymers,poly(ethylene carbonate-co-ethylene oxide)methacrylate,PEG methacrylate macromonomers,heterogeneous polymer blends,polymer electrolyte membranes,lithium salt containing gels},
  language     = {eng},
  pages        = {143},
  publisher    = {ARRAY(0x7eee230)},
  title        = {Lithium Ion Conductive Membranes Based on Co-continuous Polymer Blends},
  year         = {2005},
}