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## Synthesis and characterization of a new complex lithium salt for application in lithium-ion batteries

### Sandra Agnieszka Młynarska

#### Abstract

Introduction It is hard to imagine today's reality without rechargeable batteries. There is a great need to improve the known technologies to improve the performance of such devices. Currently, research focuses on lithium-ion batteries, and among them a large attention is paid to the materials used as electrolytes fulfilling the role of electrodes’ separators and electrical charge carriers. Widely used as an electrolyte is salt LiPF6. This salt provides high ionic conductivity, but has several disadvantages, which include thermal and hydrolytic instability. That is why search for new lithium-ion compounds to replace it continues. Research on new lithium salts, out of which a very promising group are borate salts, both in monomeric form as well as of oligomeric or polymeric structure is being carried out. According to previous studies in the Department of Chemistry and Polymer Technology of Warsaw University of Technology, borate salts can be obtained by complexation reactions of salts of carboxylic acids using boron fluoride. The best results are obtained for the borate derivatives containing oligomeric oxyethylene groups. Results and discussion My work is devoted to the synthesis of carboxyborate lithium salt poly(oxyethylene glycol) bis(carboxymethyl) ether acid of molecular mass Mn = 600. The aim of the research was to select the conditions for the synthesis and purifying of the received salt in terms of its efficiency and cleanliness. The synthesis consists of two stages: the first one was the reaction of poly(oxyethylene glycol) bis(carboxymethyl) ether acid of molecular mass Mn = 600 with n-butyllithium. The product was the lithium salt of the acid. The second stage of the synthesis was the reaction of the received lithium salt with BF3, which product was the carboxyborate lithium salt. I have conducted spectral characteristics of the obtained carboxyborate lithium salt poly(oxyethylene glycol) bis(carboxymethyl) ether acid. I have made FTIR, DSC, MALDI-ToF, 1H NMR, 11B NMR and 19F NMR analyzes of samples of this salt. I have tested the impact of different solvents for the salt. I have also tested the impact of n-butyllithium for this salt and the salt of analogous structure, but a smaller number of oxyethylene groups in the polymer chain - carboxyborate lithium salt poly(oxyethylene glycol) bis(carboxymethyl) ether acid of molecular mass Mn = 250. I have also made polymer electrolytes consisting of carboxyborate lithium salt and poly(ethylene oxide) with different molar ratio. I have made DSC analysis of prepared electrolytes and compared their ion conductivity in the temperature range 10 - 80 °C. Conclusions The reaction of poly(oxyethylene glycol) bis(carboxymethyl) ether acid of molecular mass Mn600 with n-butyllithium gives the lithium salt of this acid. In the reaction of this salt with BF3, the carboxyborate lithium salt poly(oxyethylene glycol) bis(carboxymethyl) ether acid is obtained. The form of this salt is amorphous. It contains an average of 11.2 oxyethylene groups in the polymer chain. The glass transition temperature Tg is -16.13 ° C. Undergoes hydrolysis, decomposing into acid, from which it was created. In the reaction of carboxyborate lithium salt with n-butyllithium, the synthesis reaction of this salt has been reversed with recreating the lithium salt – for both reactions of salts of acid of molecular mass Mn = 600 and Mn = 250. The resistance measurements of polymer electrolytes, with the usage of impedance spectroscopy, showed ionic conductivity characteristics of PEO complexes with a high degree of crystallinity. The highest ion conductivity in the temperature range 10 - 70 °C has shown the electrolyte of 1:1 molar ratio of the number of lithium ions to ethylene oxide, it means the one with the highest carboxyborate lithium salt content relative to PEO. At room temperature the conductivity is of the order of 10-6 S cm-1.
Diploma type
Engineer's / Bachelor of Science
Diploma type
Engineer's thesis
Author
Sandra Agnieszka Młynarska (FC) Sandra Agnieszka Młynarska,, Faculty of Chemistry (FC)
Title in Polish
Synteza i badanie właściwości nowej kompleksowej soli litu do zastosowania w bateriach litowo-jonowych
Supervisor
Ireneusz Wielgus (FC/CPCT) Ireneusz Wielgus,, Chair Of Polymer Chemistry And Technology (FC/CPCT)Faculty of Chemistry (FC)
Certifying unit
Faculty of Chemistry (FC)
Affiliation unit
Chair Of Polymer Chemistry And Technology (FC/CPCT)
Study subject / specialization
, Technologia Chemiczna
Language
(pl) Polish
Status
Finished
Defense Date
08-02-2016
Issue date (year)
2016
Reviewers
Ireneusz Wielgus (FC/CPCT) Ireneusz Wielgus,, Chair Of Polymer Chemistry And Technology (FC/CPCT)Faculty of Chemistry (FC) Wanda Ziemkowska (FC/DCOC) Wanda Ziemkowska,, Department Of Catalysis And Organometallic Chemistry (FC/DCOC)Faculty of Chemistry (FC)
Keywords in Polish
trifluorek boru (BF3), butylolit (BuLi), bateria litowo-jonowa, elektrolity polimerowe
Keywords in English
Boron trifluoride (BF3), butyllithium (BuLi), lithium-ion battery, polymer electrolytes
Abstract in Polish
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S. Młynarska - praca inżynierska - 1029215.pdf
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Identyfikator pracy APD: 8424

Uniform Resource Identifier
https://repo.pw.edu.pl/info/bachelor/WUTeb953eeef0c841dba8907acb75c425cf/
URN
urn:pw-repo:WUTeb953eeef0c841dba8907acb75c425cf

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