The obtained GPE was a self-standing transparent film without vis

The obtained GPE was a self-standing transparent film without visible leakage of liquid electrolyte. The ionic conductivity of GPEs strongly depends on the amount of liquid electrolyte embedded in the pores of a polymer membrane, and it is accepted that the absorbed electrolyte solution acts as a medium for ion transport through the polymer matrix

[26, 27]. A typical EIS plot for the PVDF-HFP/PMMA/SiO2 composite sandwiched between two stainless steel blocking electrodes is shown in Figure 3c. No semicircles were observed in the high-frequency part of the Nyquist plot, implying that the polymer electrolyte has a high integrity and its total conductivity mainly results from the ionic conduction [28, 29]. The GPE membrane exhibited a high room temperature ionic conductivity of 3.12 mS cm−1. The CV data of the GPE (Figure 3d) do not show any breakdown or abrupt current rise during cycling up to 4.5 V vs. Li+/Li, confirming that the GPE is electrochemically stable in the operation range of Li|S cell between 1 and 3 V vs. Li+/Li. Figure 3 Morphology, ionic conduction, and electrochemical stability of the synthesized GPE. (a, b) SEM images of PVDF-HFP/PMMA/SiO2 polymer matrix at different magnifications.

(c) Impedance buy LY294002 spectra of as-prepared gel polymer electrolyte. (d) CV profile of Li/GPE/SS cell (scan rate 0.1 mV s−1). The electrochemical performance of the Li|GPE|S cell with the S/GNS composite is presented in Figure 4. The galvanostatic charge–disSelleck KPT 330 charge profiles and cycling performance of the cells are depicted in Figure 4a,b. The discharge curves (Figure 4a) show two plateaus that can be assigned to the two-step reaction

of sulfur with lithium [9, 10]. The first plateau at about 2.4 V is related to the formation Bacterial neuraminidase of higher-order lithium polysulfides (Li2S n , n ≥ 4), which are soluble in liquid electrolyte. The following electrochemical transition of these polysulfides into lithium sulfide Li2S2/Li2S is associated to a prolonged plateau around 2.0 V. The kinetics of the latter reaction is slower than that of the polysulfide formation, which is reflected by the length of the plateaus [6]. Figure 4b presents the cycling performance of the Li|GPE|S cell with the S/GNS composite cathode. The cell delivers a high initial discharge capacity of about 809 mAh g−1 at 0.2C rate and exhibits an enhanced cyclability. This indicates that a combination of the S/GNS composite cathode and PVDF-HFP/PMMA/SiO2 GPE plays a significant role of retarding diffusion of the polysulfides out of the cathode area and suppressing their transport towards the anode side (shuttle effect). The coulombic efficiency data presented in the same figure confirm this suggestion and reach 95%. For further clarification of the effects of S/GNS composite and GPE on the cell performance, its rate capability performance was investigated.

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