Gel polymer electrolyte with high ionic conductivity and high lithium ion transference number for lithium-ion batteries attracts unremitting pursuit of scientists. For that, we develop a novel strategy of one-step reactive vapor-induced phase separation (RVIPS) to fabricate a porous polymer electrolyte (PPE) membrane from poly(vinylidene fluoride-hexafluoropropylene) (PVDF-HFP). The polymer and a salt of lithium bis(trifluoromethanesulfonyl) imide (LiTFSI) were first mixed in acetone, then the solution was cast under an ammonia water atmosphere to evaporate solvent. The porous microstructure of the obtained PPE membrane was carefully analyzed and was compared with that of the PPE membrane prepared under water vapor of a usual VIPS. Moreover, the electrochemical properties of the PPE membranes were measured. Our results indicate that the reactive vapor of ammonia water induced dehydrofluorination of PVDF-HFP to result in its cross-linking. The cross-linking together with the plasticizer effect of the incorporated LiTFSI suppresses the crystallization of PVDF-HFP, while enhancing the flexibility of the polymer chain segments. As a result, the PPE membrane containing 10% LiTFSI displays interconnected pores and takes up 240% liquid electrolyte, so as to possess an ionic conductivity as high as 1.32 × 10^–3 S cm⁻¹ at 30 ºC. In addition, battery tests demonstrate a high-rate ability and excellent cycle performance of the PPE membrane fabricated via the RVIPS. An initial capacity of 128 mAh∙g⁻¹, 97.7% capacity retention and 99.9% Coulombic efficiency at 1C after 120 cycles of the cell equipped with the PPE membrane undoubtedly indicate its promising potential.

Graphical Abstract

中文翻译：

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锂离子电池用一步反应气相诱导相分离法制备聚偏氟乙烯-六氟丙烯多孔聚合物电解质

用于锂离子电池的高离子电导率和高锂离子迁移数的凝胶聚合物电解质引起了科学家们的不懈追求。为此，我们开发了一种新的一步反应蒸汽诱导相分离 (RVIPS) 策略，以从聚（偏二氟乙烯-六氟丙烯）（PVDF-HFP）制造多孔聚合物电解质（PPE）膜。首先将聚合物和双（三氟甲磺酰基）亚胺锂盐（LiTFSI）在丙酮中混合，然后将溶液在氨水气氛下浇铸以蒸发溶剂。仔细分析所得 PPE 膜的多孔微观结构，并将其与在普通 VIPS 的水蒸气下制备的 PPE 膜进行比较。此外，还测量了 PPE 膜的电化学性能。我们的结果表明，氨水的反应性蒸汽诱导 PVDF-HFP 脱氟化氢，从而导致其交联。交联和掺入的 LiTFSI 的增塑剂作用抑制了 PVDF-HFP 的结晶，同时增强了聚合物链段的柔韧性。因此，含有 10% LiTFSI 的 PPE 膜显示出相互连通的孔隙，并占据 240% 的液体电解质，从而具有高达 1.32 × 10 的离子电导率^–3  S cm ⁻¹在 30 ºC。此外，电池测试表明通过 RVIPS 制造的 PPE 膜具有高倍率能力和出色的循环性能。在配备 PPE 膜的电池经过 120 次循环后，1C 下128 mAh∙g ^-1的初始容量、97.7% 的容量保持率和 99.9% 的库仑效率无疑表明其具有广阔的潜力。

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