Design And Electro-chemical Performance Of Crosslinked Solid Polymer Electrolytes For Lithium Metal Battery

Electrolyte is one of the indispensable components in lithium-ion battery,and solid electrolytes serve as separator and liquid electrolyte,which can not only separate the cathode and anode,but also deliver lithium ion.Compared with liquid electrolytes,solid electrolytes have the advantages of wider electrochemical stability window,light weight,and better interfacial compatibility with lithium metal anodes.However,the low room temperature ionic conductivity and poor mechanical strength of polyether-based polymer electrolytes limit the further application of solid polymer electrolytes.In this dissertation,by using organicinorganic hybrid nanoparticles as cross-linked core,forming cross-linked structure and introducing new polymer substrate to help enhance the mechanical properties of polymer electrolytes,it provides new approaches to improve the performance of polymer electrolytes.Firstly,POSS-SH,a typical organic-inorganic hybrid nanoparticle,was utilized as the cross-linked core,and long-chain polyethylene glycol was harnessed as the cross-linking agent,and the hybrid polymer electrolytes were prepared by the initiator-free thiol-ene reaction initiated by ultraviolet irradiation.The mechanism of initiator-free thiol-ene photopolymerization is proposed and the effects of different lengths of polyethylene glycol chain and diverse types of double bond were systematically investigated based on the electrochemical performance and the mechanical strength of the hybrid polymer electrolytes.Therefore,a facile way was developed to fabricate cross-linked hybrid polymer electrolytes for lithium-metal batteries via initiator-free thiol-ene photopolymerization.Secondly,the long-chain polyethylene glycol diol was used as initiator and stannous octanoate was employed as catalyst,bulk caprolactone monomers are polymerized via ringopening reaction to obtain PCL-PEG-PCL triblock polymers.The end group was modified by the functionalization of double bond.The hybrid triblock polymer electrolyte was fabricated via the initiator-free thiol-ene photopolymerization.The introduction of polycaprolactone drastically improves the mechanical properties of polymer electrolytes.The combination of ring-opening polymerization and initiator-free thiol-ene photopolmerization would broaden the method for polyester-based cross-linked hybrid polymer electrolytes and provided new options for the functionalization of polymer electrolytes.Thirdly,CD-SH,a thiolated decorated cyclodextrin,was utilized as the cross-linked core,and long-chain polyethylene glycol was harnessed as the cross-linking agent,and the cyclodextrin-based polymer electrolytes were prepared by the initiator-free thiol-ene photopolymerization.The effects of different lengths of polyethylene glycol chain and various functionality of thiolated decorated cyclodextrin were systematically investigated based on the electrochemical performance of the cyclodextrin-based polymer electrolytes.The cyclodextrin-based polymer electrolytes own high ionic conductivity,excellent cycling performance and ultra stable interfacial compatibility.Finally,HAm CP,a hybrid flame-retardant nanoparticle,was utilized as the cross-linked core,and long-chain polyethylene glycol diglycidyl ether was harnessed as the cross-linking agent,and the cyclophosphazene-based hybrid polymer electrolytes were prepared by the epoxy-amine thermal curing reaction.The effects of different lengths of polyethylene glycol chain was systematically investigated based on the electrochemical performance and the mechanical strength of the cyclophosphazene-based hybrid polymer electrolytes.The cyclophosphazene-based hybrid polymer electrolytes exhibit high thermal stability and ionic conductivity,excellent cycling performance and C-rates,stable interfacial compatibility with lithium anode.