Synthesis And Properties Of Poly (Ether Sulfone)-poly (Ethylene Oxide) Copolymers As Novel All-solid-state Polyelectrolyte Separators

Separator is one of the most important components of lithium ion batteries. It isvery crucial to design high performance (excellent mechanical strength, high ionicconductivity, good chemical stability, safe and effective, environment friendly) andlow cost separators. All-solid-state polymer electrolytes have attacted much attentionin the past decades because they possess many advantages over traditional liquid-electrolyte-filled microporous separators or polymer gels such as non-volatility, noelectrolyte leakage and imflammability which allow lithium ion batteries to operatemore safely at elevated temperatures.This thesis mainly focus on the preparation, characterization and properties ofthree different types of all-solid-state polymer electrolytes, bistrifluoromethanesulfo-nimide-lithium-doped and succinonitrile-plasticized poly(ethylene oxide)-segmentedpoly(ether sulfone)s, poly(ethylene oxide)-segmented sulfonated poly(ethyle sulfone)lithium salts (LiSPES-PEO), and poly(ethylene oxide)-segmented poly(ether sulfone/sulfonated polystyrene lithium salt blends (PES-PEO/SPSLi).In the first part, a series of poly(ethylene oxide)-segmented poly(ether sulfone)copolymers have been synthesized and their thermal stability, lithium salt doping,lithium ion conductivity and mechanical properties have been investigated. Thesynthesis was achieved by condensation polymerization of4,4’-dichlorodiphenylsulfone (DCDPS), chlorine-terminated poly(ethylene oxide)(PEO-Cl2) prepared bythe reaction of PEG and thionyl chloride, and dibasic phenols in dimethylacetamide(DMAC) in the presence of K2CO3. The synthesized copolymers were structurallycharacterized by FT-IR and1H-NMR spectra. The copolymer membranes show hightensile stress and very large elongation at break. XRD patterns suggest that thesemembranes have amorphous structure at room temperature. The copolymermembranes doped with bistrifluoromethanesulfonimide lithium salt (LiTFSI) and plasticized with succinonitrile (SN), PES-PEO/SN/LiTFSI, displayed high lithiumionic conductivities at80oC (6.4×10-5S/cm~5.30×10-4S/cm).In the second part, a series of poly(ethylene oxide)-segmented sulfonatedpoly(ethyle sulfone) lithium salts (LiSPES-PEO) have been synthesized and theirthermal stability, lithium ion conductivity and mechanical properties have also beeninvestigated. The synthesis was achieved by condensation polymerization of4,4’-difluorodiphenyl sulfone-3,3’-disulfonated sodium salt (DFDPSDS),4,4’-dichlorodiphenyl sulfone (DCDPS), chlorine-terminated poly(ethylene oxide)(PEO-Cl2) prepared by the reaction of PEG and thionyl chloride, and4,4’-dihydroxybiphenyl (DHBP) in dimethylacetamide (DMAC) in the presence of K2CO3.The synthesized copolymers were structurally characterized by FT-IR and1H-NMRspectra. Then membranes were fabricated by the solution cast technique andsubsequently converted into the lithium salt form of the copolymer membranes. Themembranes LiSPES-PEO displayed high lithium ionic conductivities at80oC（5.84×10-7S/cm~2.09×10-4S/cm）.In the third part, a new type of polymeric lithium salt, sulfonated polystyrenelithium salt (degree of sulfonation=32.2%),(SPSLi) was synthesized andsubsequently blended with the PES-PEO in solution at varied weight ratios to yieldnovel polymer blend electrolyte membranes (PES-PEO/SPSLi). The blendmembranes show high tensile stress and very large elongation at break. XRD patternssuggest that these membranes have amorphous structure at room temperature Themembranes PES-PEO/SPSLi displayed high lithium ionic conductivities at80oC（6.25×10-7S/cm~2.38×10-6S/cm）.