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

while stabilizing lithium metal [29,30] . C provides the conversion sites for lithium polysulfide, and zeolitic
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imidazolate framework-67 (ZIF-67) provides the chemical adsorption sites [31,32] . The nanofiber membrane
plays an important role in adsorption, conversion of polysulfides, and inhibition of lithium dendrite growth,
improving the performance of lithium-sulfur batteries.

Therefore, in this work, a gelatin-based multifunctional composite separator (CZGNF) was designed and
prepared by the electrospinning method. The CZGNF separator is a two-layer nanofibrous membrane with
multiple functions. Gelatin with good ionic conductivity and high lithium-ion mobility is an excellent
material for a separator. Gelatin can also achieve homogenization of the lithium-ion flux and improve the
stability of lithium metal. In the CZGNF separator, polysulfides are chemisorbed by ZIF-67, preventing the
shuttling of lithium polysulfides. C provides lithium polysulfide conversion sites and improves the
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conversion efficiency of Li polysulfides. The preparation of the CZGNF separator is simple, and it can
effectively prevent the “shuttle effect” while improving the stability of the lithium anode. The performance
of Li-S batteries is significantly improved. This article provides new ideas for the study of multifunctional
composite nanofiber separators.

EXPERIMENTAL METHODS
Materials
Multi-walled carbon nanotubes (L-MWNT-1020 Shenzhen Nano Port), sublimed sulfur (AR, Aladdin),
Co(NO ) ·6H O (AR, Shanghai Hushi), 2-methylimidazole (99%, Aladdin), poly(vinylidene fluoride-co-
2
3 2
hexafluoropropylene) (PVDF-HFP, molecular weight, MW = 400000), 1-methyl-2pyrrolidinone (NMP,
anhydrous, 99.5%, Aladdin), gelatin (Aladdin, Chemical purity (CP), Shanghai Aladdin Biochemical
Technology Co., LTD), acetic acid (Sinopharm Chemical Reagent Co., Ltd.), methyl alcohol (99.8% from
ACP Chemical Inc.), C (99.9%, Aladdin). All chemicals were purchased and used directly without further
60
treatment.

Preparation of ZIF-67
40 mmol 2-methylimidazole and 10 mmol Co (NO ) ·6H O were separately dissolved in 100 mL of
2
3 2
methanol and magnetically stirred for 0.5 h. Then, the 2-methylimidazole solution was slowly added to the
Co (NO ) ·6H O solution and magnetically stirred for 6 h. The resulting solution was left at room
3 2
2
temperature for 24 h, and then washed with methanol and centrifuged 3 times. Finally, the precipitate was
dried at 60 °C for 12 h to obtain purple ZIF-67 particles.
Preparation of gelatin nanofiber and C 60 /ZIF-67-GNF separator
Preparation of the gelatin nanofiber (GNF) separator: 1.8 g of gelatin was added to 8 g acetic acid and 2 g
distilled water and stirred for 12 h to obtain solution A. Electrospinning was performed with 10 mL of
solution A at a high voltage of 16.5 kV at a rate of 0.09 mL h . The distance between the needle tip and the
-1
collector was set to 17 cm. The product was dried at 60 °C for 12 h and separated from Al foil to obtain the
electrospun separator (GNF).

Preparation of the C /ZIF-67-GNF (CZGNF) separator: 0.1 g of ZIF-67, 0.1 g of C , and 1.8 g of gelatin
60
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were added to 8 g acetic acid and 2 g distilled water, followed by stirring for 12 h to obtain solution B. First,
the electrospinning of solution A was conducted in a 4 mL injection pump. After that, the electrospinning
of solution B was carried out in a 4 mL injection pump. Thus, fibrous separators of different compositions
on both sides were obtained. Finally, the electrospun separator was treated in a drying oven at 60 °C for 12 h
and separated from its Al foil to obtain the CZGNF composite separator. The electrospinning process
parameters were the same as above.