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Ion transport in novel lithium-ion battery electrolytes: Harnessing polymerization-induced phase separation for hybrid systems
KTH, School of Engineering Sciences in Chemistry, Biotechnology and Health (CBH), Fibre- and Polymer Technology, Coating Technology.ORCID iD: 0000-0002-5075-6207
2024 (English)Doctoral thesis, comprehensive summary (Other academic)
Sustainable development
SDG 11: Sustainable cities and communities, SDG 9: Industry, innovation and infrastructure, SDG 12: Responsible consumption and production, SDG 7: Affordable and clean energy
Abstract [en]

Lithium-ion batteries have enabled the rapid adoption of consumer electronics and electromobility. In many next-generation lithium-based batteries, the development of high-performing and safe electrolytes is key. Although liquid electrolytes have high ionic conductivity, they suffer from stability and safety issues. Conversely, solid polymer electrolytes offer a safer and more stable alternative, but exhibit inherently low ionic conductivity. This thesis has focused on developing new hybrid liquid and polymer electrolyte systems. 

The first part focuses on understanding the ion transport in new liquid electrolytes and oligomers. Dicarbonate structures with varying spacer and end group were investigated and compared to traditional linear carbonate electrolytes. The dicarbonate electrolytes exhibit high thermal stabilities but simultaneously a non-ideal ion transport with extensive ion pairing. The effect of molecular weight (Mn) and end group on the ion transport in two polymers with different backbones were also investigated. The investigation elucidated the effect of coordination strength on the partial lithium ion transport. It also showed that when changing the molecular weight (Mn), distinct ion transport mechanism regimes did not exist.

The second part focuses on the development of hybrid polymer-liquid electrolytes (HEs) using polymerization-induced phase separation (PIPS). It was shown that both the monomer and porogen structure has a significant effect on thermomechanical and electrochemical properties of the HEs. Finally, the use of UV-initiated PIPS was investigated as an efficient technique to manufacture porous thermoset membranes as battery separators. A membrane with low ionic resistance and promising battery cycling performance was developed. Overall, this thesis shows that hybrid systems have a role to play in systems where multiple properties need to be fulfilled simultaneously and that PIPS is a promising tool to fabricate such materials. 

Abstract [sv]

Litiumjonbatterier har möjliggjort den breda tillgången av hemelektronik och elektromobilitet. En nyckel till utvecklingen av många nästagenerations litiumbaserade batterier är beroende av högpresterande och säkra elektrolyter. Även om vätskebaserade elektrolyter har hög jonledningsförmåga, lider de av stabilitets- och säkerhetsproblem. Samtidigt erbjuder fasta polymerelektrolyter ett säkrare och mer stabilt alternativ, men uppvisar låg jonledningsförmåga. Denna avhandling har fokuserat på att utveckla nya hybrida vätske- och polymerelektrolytsystem.

Den första delen fokuserar på att förstå jontransporten i nya vätskebaserade elektrolyter och oligomerer. Dikarbonatstrukturer med varierande ”spacer” och ändgrupp undersöktes och jämfördes med traditionella karbonatelektrolyter. Dikarbonatelektrolyterna uppvisar hög termisk stabilitet men samtidigt en icke-ideal jontransport med omfattande jonparning. Effekten av molekylvikt (Mn) och ändgrupp på jontransporten i två polymerer med olika kedjestruktur undersöktes också. Studien klargjorde effekten av koordinationsstyrka på den partiella litiumjontransporten. Det visade också att när man ändrade molekylvikten (Mn), förändrades inte jontransportmekanismer.

Den andra delen fokuserar på utvecklingen av hybrida vätske-polymerelektrolyter (HE) med hjälp av polymerisationsinducerad fasseparation (PIPS). Det visades att både monomer- och porogenstrukturen har en betydelsefull påverkan på termomekaniska och elektrokemiska egenskaper hos HE:erna. Slutligen undersöktes användningen av UV-initierad PIPS som en effektiv metod för att tillverka porösa härdplastmembran för att användas som batteriseparatorer. Ett membran med låg jonresistens och lovande battericyklingsprestanda utvecklades. Sammantaget visar denna avhandling att hybrida system har en roll att spela i system där flera egenskaper måste uppfyllas samtidigt och PIPS är ett lovande verktyg för att tillverka sådana material.

Place, publisher, year, edition, pages
Stockholm: KTH Royal Institute of Technology, 2024. , p. 69
Series
TRITA-CBH-FOU ; 2024:45
Keywords [en]
Lithium-ion, lithium metal, structural battery, hybrid electrolyte, oligomer, ion transport, molecular weight, polymerization-induced phase separation, separator
Keywords [sv]
Litiumjon, litiummetal, strukturella batterier, hybrida elektrolyter, oligomerer, jontransport, molekylvikt, polymerisationsinducerad fasseparation
National Category
Materials Chemistry Polymer Chemistry Energy Engineering
Research subject
Fibre and Polymer Science
Identifiers
URN: urn:nbn:se:kth:diva-354363ISBN: 978-91-8106-070-6 (print)OAI: oai:DiVA.org:kth-354363DiVA, id: diva2:1903437
Public defence
2024-11-01, F3 (Flodis), Lindstedtsvägen 26, https://kth-se.zoom.us/j/61354274681, Stockholm, 10:00 (English)
Opponent
Supervisors
Note

QC 20241008

Available from: 2024-10-08 Created: 2024-10-04 Last updated: 2024-10-14Bibliographically approved
List of papers
1. Understanding ion transport in alkyl dicarbonates: an experimental and computational study
Open this publication in new window or tab >>Understanding ion transport in alkyl dicarbonates: an experimental and computational study
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(English)Manuscript (preprint) (Other academic)
Abstract [en]

In an effort to improve safety and cycling stability of liquid electrolytes, the use of dicarbonates have been explored. In this study, four dicarbonate structures with varying end groups and spacers are investigated. The effect of these structural differences on the physical and ion transport properties is elucidated, showing that the end group has a significant influence on the ion transport. The solvation structure and ion transport in the dicarbonates are compared to the linear carbonates dimethyl carbonate (DMC) and diethyl carbonate (DEC). Although the carbonate coordination numbers (CN) are similar in the different systems, the CN from the anion is higher in the dicarbonate electrolytes. At low salt concentrations, rapid solvent exchange is observed in the DMC and DEC containing systems, transitioning to a more correlated ion transport at high salt concentration. In contrast, the exchange of solvents around lithium ions (Li+) is limited in the dicarbonate systems regardless of the salt concentration, with only one carbonate group from each molecule participating in the coordination. In addition, according to the molecular dynamics simulations, Li+ mainly moves together with coordinating dicarbonate molecules and anion(s).

National Category
Physical Chemistry
Identifiers
urn:nbn:se:kth:diva-354358 (URN)
Note

QC 20241004

Available from: 2024-10-04 Created: 2024-10-04 Last updated: 2024-10-04Bibliographically approved
2. Influence of Molecular Weight and End Groups on Ion Transport in Weakly and Strongly Coordinating Polymer Electrolytes
Open this publication in new window or tab >>Influence of Molecular Weight and End Groups on Ion Transport in Weakly and Strongly Coordinating Polymer Electrolytes
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2024 (English)In: ChemElectroChem, E-ISSN 2196-0216Article in journal (Refereed) Epub ahead of print
Abstract [en]

In the development of polymer electrolytes, the understanding of the complex interplay of factors that affect ion transport is of importance. In this study, the strongly coordinating and flexible poly (ethylene oxide) (PEO) is compared to the weakly coordinating and stiff poly (trimethylene carbonate) (PTMC) as opposing model systems. The effect of molecular weight (Mn) and end group chemistry on the physical properties: glass transition temperature (Tg) and viscosity (η) and ion transport properties: transference number (T+), ion coordination strength and ionic conductivities were investigated. The cation transference number (T+) showed the opposite dependence on Mn for PEO and PTMC, decreasing at low Mn for PTMC and increasing for PEO. This was shown to be highly dependent on the ion coordination strength of the system regardless of whether the end group was OH or if the chains were end-capped. Although the coordination is mainly of the cations in the systems, the differences in T+ were due to differences in anion rather than cation conductivity, with a similar Li+ conductivity across the polymer series when accounting for the differences in segmental mobility.

Place, publisher, year, edition, pages
Wiley, 2024
National Category
Chemical Sciences Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-354330 (URN)10.1002/celc.202400415 (DOI)
Note

QC 20241003

Available from: 2024-10-03 Created: 2024-10-03 Last updated: 2024-10-04Bibliographically approved
3. Exploring the use of oligomeric carbonates as porogens and ion-conductors in phase-separated structural electrolytes for Lithium-ion batteries
Open this publication in new window or tab >>Exploring the use of oligomeric carbonates as porogens and ion-conductors in phase-separated structural electrolytes for Lithium-ion batteries
2023 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 1873-3859, Vol. 449, article id 142176Article in journal (Refereed) Published
Abstract [en]

Phase-separated structural battery electrolytes (SBEs) have the potential to enhance the mechanical stability of the electrolyte while maintaining a high ion conduction. This can be achieved via polymerization-induced phase separation (PIPS), which creates a two-phase system with a liquid electrolyte percolating a mesoporous ther-moset. While previous studies have used commercially available liquid electrolytes, this study investigates the use of novel oligomeric carbonates to enhanced the safety of the SBEs. Increasing the carbonate chain length significantly enhances the thermal stability of the SBEs. Tuning the molecular structure of the liquid electrolyte has a significant effect on the PIPS process and SBE morphology. Using a combination of analyses on a series of wet and dried SBEs, the complex interplay between the phases is interpreted. When an increased pore size is achieved, it leads to a lower MacMullin number (NM). A conductivity of 2 x 10-5 S/cm with a NM=13 could be achieved, while maintaining a thermal stability up to 150 degrees C. The present study demonstrates a versatile approach to tailor this type of electrolyte.

Place, publisher, year, edition, pages
Elsevier BV, 2023
Keywords
Structural batteries, Polymer electrolyte, Polymerization-induced phase separation, Ionic conductivity, McMullin number, Carbonate oligomers, Lithium ion
National Category
Materials Chemistry
Identifiers
urn:nbn:se:kth:diva-326065 (URN)10.1016/j.electacta.2023.142176 (DOI)000957971600001 ()2-s2.0-85150247700 (Scopus ID)
Note

QC 20230425

Available from: 2023-04-25 Created: 2023-04-25 Last updated: 2024-10-04Bibliographically approved
4. Effect of monomer composition on the formation of hybrid polymer-liquid electrolytes for lithium-ion batteries
Open this publication in new window or tab >>Effect of monomer composition on the formation of hybrid polymer-liquid electrolytes for lithium-ion batteries
(English)Manuscript (preprint) (Other academic)
Abstract [en]

Hybrid polymer-liquid electrolytes (HEs) are suitable candidates for novel concepts of lithium-ion batteries (LIBs) and lithium-metal batteries (LMBs), where high ionic conductivity coupled with mechanical performance are required at the same time, thus giving such batteries the definition of multifunctional materials. HEs are produced through polymerization-induced phase separation (PIPS) of a monomer / liquid electrolyte mixture having suitable solubility parameters. This process allows for the formation of a two-phase system, where the domains develop a bicontinuous structure. Electrochemical performance and thermomechanical behavior can be tailored through several variables e.g., monomer and solvent chemistries, solvent concentration and curing conditions. The present study is focused on the chemical structure of the monomer where methacrylate and acrylate monomers are compared as homopolymers or copolymers. The number of ethylene oxide (EO) units in the backbone of the monomers are furthermore analyzed as a structural parameter. The results show that the monomer structure not only affects the electrochemical and thermomechanical properties, but also defines the morphology of the HE obtained, which can be in the form of a bicontinuous structure, a gel, or a mixture of the two, according to the kinetic and thermodynamic variables affecting the phase separation and the ultimate Tg of the polymer.

National Category
Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-354362 (URN)
Note

QC 20241004

Available from: 2024-10-04 Created: 2024-10-04 Last updated: 2024-10-04Bibliographically approved
5. Tuneable and efficient manufacturing of Li-ion battery separators using photopolymerization-induced phase separation
Open this publication in new window or tab >>Tuneable and efficient manufacturing of Li-ion battery separators using photopolymerization-induced phase separation
(English)Manuscript (preprint) (Other academic)
Abstract [en]

In an effort to increase the thermomechanical stability of lithium-ion battery separators, thermoset membranes (TM) are a viable alternative to commercial polyolefin separators. We present an efficient and scalable method to produce thin TMs via photopolymerization-induced phase separation (PIPS) in ambient conditions. The pore size is controllable and tuneable by varying the ratio between propylene carbonate (PC) and tetraethylene glycol (TEG) as porogens. The TMs maintain dimensional stability above 200 C and sufficient mechanical stiffness. By incorporating a small amount of a thiol monomer, the brittleness of the TMs was suppressed, and a high Young’s modulus is achieved (880 MPa). The ionic conductivity of the optimized TMs was around 1 mS cm-2, with a low MacMullin number, NM (4.9). In symmetrical Li/Li cells, the TMs behaved similar to the commercial PE reference, effectively suppressing short circuits for 1000+ hours although continuous overpotential build-up and electrolyte consumption eventually led to cell failure. In LiFePO4/Li half-cells, similar rate capabilities were achieved for the TMs compared to the reference showing its viability as a separator material.   

National Category
Energy Engineering Polymer Chemistry
Identifiers
urn:nbn:se:kth:diva-354393 (URN)
Note

QC 20241004

Available from: 2024-10-04 Created: 2024-10-04 Last updated: 2024-10-04Bibliographically approved

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Emilsson, Samuel

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