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Page 10 of 14 Liang et al. Energy Mater 2023;3:300006 https://dx.doi.org/10.20517/energymater.2022.63

th
Figure 7. (A) The 1st cycle charge-discharge curves; (B) magnified discharge curves; (C) 100 cycle charge-discharge curves; and (D)
cycling performances of the Li-S batteries with different separators at 0.2 C.

separator, and 11 mV for the CZGNF separator, so the Li-S battery with CZGNF separator had the smallest
overpotential. Thus, the CZGNF separator improved the liquid-solid conversion kinetics of lithium
polysulfide. Three quarters of the theoretical capacity of the sulfur cathodes came from the deposition of
soluble lithium sulfide to be converted to insoluble Li S, so it is important for rapid polysulfide transition
2
[33]
kinetics and abundant deposition sites, which facilitate the cycling performance of Li-S batteries . For the
Li-S battery with CZGNF separator after 100 cycles, the specific discharge capacity remained at 888 mAh
g , and the capacity retention rate was 65.4%. The discharge specific capacities of Li-S batteries with GNF
-1
-1
and PP separators after 100 cycles were 750 mAh g and 539 mAh g , respectively, and their capacity
-1
retention rates were 56.2% and 44.1%, respectively [Figure 7C and D]. The presence of a slight shuttle effect
may lead to unstable and excessive discharge/charge efficiency of lithium-sulfur batteries . Therefore, the
[34]
Coulombic efficiency of Li-S batteries with CZGNF separator is higher than those of Li-S batteries with
GNF separator and PP separator. The Li-S battery with CZGNF separator had the highest initial capacity,
the highest capacity retention rate, and the highest Coulombic efficiency due to fast ion/electron diffusion
and high lithium polysulfide conversion efficiency.

Figure 8 shows the electrochemical impedance spectra (EIS) of the Li-S batteries with three separators
before and after cycling. The Li-S battery with CZGNF separator has the lowest impedance value because of
the high ionic conductivity of the CZGNF separator, which accelerates electron transfer inside the battery