The electrochemical stability window of GPE was determined by cyclic voltammetry (CV) conducted with VMP3 in coin-type cells where GPE was interleaved between lithium metal and stainless steel electrodes. The electrochemical performance of the S/GNS composite cathode was investigated in coin-type cells (CR2032) with PVDF-HFP/PMMA/SiO2 GPE. The cell was composed of a lithium metal anode and the S/GNS composite cathode separated find more by the GPE film. The cathode is comprised of 80 wt% S/GNS composite, 10 wt% acetylene black (AB; 99.5% purity, MTI, Richmond, CA, USA) as a conductive agent, and 10 wt% polyvinylidene fluoride
(PVDF; 99.5% purity, MTI) as a binder. These materials were dispersed in 1-methyl-2-pyrrolidinone (NMP; ≥99% purity, Sigma-Aldrich). The resultant slurry was spread onto aluminum foil using
a doctor blade and dried at 50°C for 12 h. The resulting cathode film was used to prepare the cathodes by punching circular disks of 1 cm in diameter. The coin cells were assembled in high-purity argon (99.9995%) atmosphere. The cells were tested galvanostatically on multi-channel battery tester (BT-2000, Arbin Instruments, College Station, TX, USA) between 1 and 3 V vs. Li+/Li. The applied currents CDK inhibitor and specific capacities were calculated on the basis of the weight of S in the cathode. Results and discussion Figure 2a,b,c exhibits the SEM images of the S/GNS composite at different magnifications. The data of Figure 2a,b show that after the high-speed ball milling the composite contains graphene nanosheets remarkably reduced in size compared with the initial graphene used for the composite synthesis (not shown). At the higher magnification (Figure 2c), it can be clearly seen that GNS sheets are covered with sulfur, and irregular stacks of interlaced nanosheet-like structure were formed. The EDX
mapping (Figure 2d,e,f) confirms the homogeneous distribution of the components of the S/GNS composite. It could be suggested that the graphene nanosheets may act as nano-current collectors for the sulfur particles and enhance the conductivity of the composite. On the other hand, the size reduction of graphene and formation of disordered and hollow structure of the composite agglomerates create the pathways Axenfeld syndrome for the electrolyte and Li-ion transport providing enhanced activity of the composite. These structural advantages of the composite are favorable for the cathode rate capability, which was further observed in the electrochemical studies. Figure 2 Morphology of the synthesized S/GNS composite. (a to c) SEM image of S/GNS composites at different magnifications. (d to f) EDX mapping showing distribution of carbon and sulfur. Figure 3a,b presents the SEM images of the PVDF-HFP/PMMA/SiO2 polymer matrix at different magnifications. The membrane is highly porous, and the pore diameters range from 1 to 5 μm.
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