Preparation And Performance Of Comb-Like Polymer Electrolyte Based On Sulfonated Poly(ether Ether Ketone)

With good mechanical performance, light quality, and excellent shape plasticity, Solid polymer electrolyte is an important alternative for lithium ion battery electrolytes. It has been studied extensively in the past decades. Polyethylene oxide(PEO) is regarded as the most proper matrix of solid polymer electrolyte. The ether oxygens act as coordinating sites in the system that promote the association/dissociation of the salt. Although such complexes show high ionic conductivity at high temperature, the properties for crystallization of polymers at low temperatures severely reduce their conductivity, and thus the high ionic conductivity and strong mechanical strength cannot be obtained spontaneously due to its preference for crystalizing.In this paper, a novel comb-like polymer sulfonate poly(ether ether ktone)-graftpoly(ethylene glycol)(SPEEK-g-PEG) was synthesized. Firstly, SPEEK were prepared by the sulfonation of poly ether ether ktone(PEEK). Then the partially hydroxyl-functionalized SPEEK-OH was obtained by the reduction of part of benzophenone moieties into the corresponding benzhydrol moieties. Lastly, SPEEK-OH was further reacted with EpoxidePEG. The results of FT-IR and 1H-NMR showed that SPEEK-g-PEG had been synthesized successfully. The polymers have good thermal stability proven by TGA investigation. Also, the DSC and XRD investigation indicated that the novel comb-like PEO are mostly in amorphous state at room temperature.Series of comb-like SPEEK-g-PEG with various length of side chains and grafting density were synthesized by grafting different weight of PEO to SPEEK with different reduction degree. SPEEK-g-PEG with different proportions of LiClO4 are poured into membrane, get a series of solid polymer electrolyte of lithium ion battery with different side chain length and grafting density. Its ionic conductivity was tested by AC impedance method. The results show that the ionic conductivity of polymer electrolyte are relate to side chain length, grafting density, concentration of lithium, and temperature.The ionic conductivity of comb-like polymer SPEEK-g-PEG can reach 10-4 S/cm at room temperature, which is two order of magnitude higher than the mixture of SPEEK/PEG with the same composite. The ionic conductivity of SPEEK-g-PEG increases with the increasing of grafting density and decreasing of concentration of lithium ions. The ionic conductivity of the SPEEK-g-PEG550 electrolyte reach 1.45×10-4 S/cm at 30 oC, when the grafted rate is 43% and the [EO] / [Li~+] is 16/1.