Characterization of PEO18−LiTFSI−5 %SiO2−5 %SN Composite Polymer Electrolyte Membrane

As shown in Figure 2(a, b), the diameter of SiO2 nanospheres ranges from 200 nm to 300 nm. the thickness of the membrane is ∼100 μm, which can be controlled by the amount of pouring solution. By observing the SEM figure of the membrane, the surface of the membrane presents wavy folds, and no pore structure, indicating the excellent densification of the membrane. Meanwhile, no exposed SiO2 particles were observed on the surface of the membrane, indicating that SiO2 nanospheres was well embedded in the PEO matrix through the action of stirring mechanism.

Figure 2(c) shows the XRD pattern of PEO18−LiTFSI−5 %SiO2−5 %SN composite solid polymer electrolyte. we can observe two characteristic diffraction peaks corresponding to the PEO chains at 2θ=19° and 23°. By comparing the intensity of the diffraction peaks, diffraction peak intensity of PEO18−LiTFSI−5 %SiO2−5 %SN solid polymer electrolyte is lower, indicating that the crystallinity of PEO18−LiTFSI−5 %SiO2−5 %SN is lower than PEO18−LiTFSI. It means that the addition of SiO2 nanospheres and SN can effectively reduce the crystallinity of PEO.

Figure 3 shows the EDS spectrum of composite solid polymer electrolyte. S and F are evenly distributed, indicating that LiTFSI was evenly dispersed in the peo matrix. The addition of SN to promote the dissociation of lithium has been better demonstrated. The uniform distribution of Si indicates that SiO2 nanospheres were evenly dispersed in the PEO matrix by mechanical stirring, ultrasonic and solution casting methods. The C and O (mainly come from PEO and SN) maintained uniform distribution, indicating that the composite solid electrolyte obtained by adding SN and SiO2 nanospheres into the PEO matrix maintained uniform dispersion.

SEM and EDS mapping of PEO18−LiTFSI−5 %SiO2−5 %SN.