The Application Of Star Polymer With Pseudo-crown Ether Cavities In Polymer Electrolyte

In recent years,lithium ion batteries?LIBs?have been widely used in portable electronic products and electric vehicles for its high energy density,low self-discharge and no memory effect.Electrolyte is one of the key components affects the performance of LIBs.Traditional LIBs based on liquid electrolytes easily lead to spme safety problems such as leakage,which restrict its further application.Solid-state polymer electrolyte?SPE?,which have many advantages such as excellent safety,good mechanical properties and processing properities,are more and more applied in LIBs.The poly?ethylene oxide??PEO?-based SPE is the earliest studied and most used system in SPE.However,the high crystallinity of PEO at room temperature restrict the ion transport.So there are various strategies to modified PEO-based SPE to get better properities material such as addition of nanofiller,polymer blends,design of a block polymer,graft polymer or cross-linked polymer and synthesis star polymer.In this paper,for the complexation of crown-ether with lithium salts can improve the conductivity,the star polymer with polymeric pseudo-crown ether cavities is synthesized and applied in polymer electrolyte.The specific research contents are as follows:?1?The star polymer comprised of cross-linked cores containing pseudo-crown ether cavities and PEO arms are designed via cation template-assisted cyclopolymerization.The star polymer electrolyte is prepared via blending the star polymer with high molecular weight PEO matrix.The pseudo-crown ether cavities in cross-linked cores can coordinate with alkali metal cations and offer more cation diffusion channels.Addition of rigid star polymer to PEO matrix can improve the mechanical properties of the system and suppress the crystallinity of PEO.The conductivity of star polymer obtained from potassium cation template and poly?ethylene glycol?dimethacrylate?PEGDMA750?monomer?K-SPE750-Li?is 2.82×10^-5 S cm^-1 at 20?,shows the structure of star polymer and PEO cavities can promote ion conduction.Furthermore,the cell of Li|K-SPE750-Li|LiFePO₄shows stable cycling performance and good rate property.The star polymer electrolyte doped sodium salts and potassium salts shows a good conductivity,which can be potentially applied in sodium ion batteries?SIBs?and potassium ion batteries?KIBs?.?2?Porous polymer electrolytes?PPEs?containing poly?vinylidene fluoride??PVDF?and the star polymer with pseudo-crown ether cavities and were prepared via phase inversion process.The porous in PPE can store liquid electrolyte,the lithium ions are free to migrate in the electrolyte with the process of ion transport.Furthermore,the addition of liquid electrolyte can improve the interface compatibility between electrolyte and electrode,and make the battery have better cycle stability.The PPE membrane with 20 wt%star polymer?PPE-2?exhibits the highest porosity,uptake and ionic conductivity(1.27×10^-3 S cm^-11 at 30 ^oC).The Li|PPE-2|LiFePO₄ shows good electrode compatibility,high specific capacity and stable cycling performance.