聚偏氟乙烯/聚偏氟乙烯磺酸锂/锂盐复合固态电解质的制备及其性能

doi:10.19799/j.cnki.2095-4239.2021.0160

摘要/Abstract

摘要：

以聚偏氟乙烯(PVDF)、氯磺酸和氢氧化锂等为原料制备了聚偏氟乙烯磺酸锂(SPVDFLi)，将SPVDFLi与PVDF复合制得单离子聚合物电解质(SIPE)。为进一步提高SIPE的电导率，向其添加双三氟甲烷磺酰亚胺锂(LiTFSI)制备双盐型聚合物复合电解质(SPVDFLi/LiTFSI-y)，通过调控LiTFSI与聚合物的比例探究了双盐型聚合物电解质的电化学性能。结果表明：LiTFSI的添加有效提高了聚合物复合电解质的电导率。含40% LiTFSI的SPVDFLi/LiTFSI-40聚合物复合电解质室温电导率可达到1.41×10^-4 S/cm，锂离子迁移数为0.68，稳定电压可以达到4.84 V。组装的LiFePO₄/SPE/Li电池，0.2 C倍率下循环50圈后容量保持率为99.1%。该聚合物复合电解质有望用于制备高性能锂离子电池。

关键词: 聚合物复合电解质, 聚偏氟乙烯磺酸锂, 电导率, 锂离子迁移数

Abstract:

Single-ion polymer electrolytes were recently developed and used in solid-state batteries. In single-ion polymer electrolytes, anions are attached to the main chain of polymers, and only lithium ions are allowed to pass through into the electrolyte. As a result, the single-ion polymer electrolytes had a high lithium-ion migration number, which will be beneficial in reducing the concentration polarization of lithium batteries. However, the low ion conductivity of single-ion polymer electrolytes limits their application in lithium batteries. In the present work, chlorosulfonic acid, polyvinylidene fluoride (PVDF), and lithium hydroxide were used to prepare sulfonated polyvinylidene fluoride (SPVDF) and polyvinylidene fluoride sulfonate lithium (SPVDFLi). The chemical structures of PVDF and SPVDF were confirmed by the 1H nuclear magnetic resonance spectra. A series of single-ion polymer electrolytes (SIPEx) were prepared by a solvent casting method from PVDF and SPVDFLi mixture solution. To improve the electrolyte's ion conductivity, PVDF/SPVDFLi/LiTFSI composite electrolytes (SPVDFLi/LiTFSI-y) were created by varying the amount of LiTFSI in the SIPE. The ion conductivity of SIPEs increased by increasing the content of SPVDFLi. The ion conductivity of PVDF/SPVDFLi/LiTFSI composite electrolytes further increased by increasing the content of LiTFSI, SPVDFLi/LiTFSI-40 showed the conductivity of 1.41×10^-4 S/cm at 25 ℃, the steady voltage of up to 4.84 V, and the capacity retention rate of is 99.1% after 50 cycles at 0.2 C, because of its high conductivity, high lithium-ion migration number, and high efficiency in inhibiting the growth of lithium dendrites SPVDFLi, the excellent lithium-ion battery assembled with SPVDFLi/LiTFSI-40. These findings suggest that the PVDF/SPVDFLi/LiTFSI composite electrolytes will be used to create high-performance solid-state lithium-ion batteries.

Key words: polymer composite electrolytes, polyvinylidene fluoride sulfonate lithium, conductivity, lithium-ion migration number

中图分类号:

TM 912

苏月, 刘旭华, 曾芳磊, 任玉荣, 林本才. 聚偏氟乙烯/聚偏氟乙烯磺酸锂/锂盐复合固态电解质的制备及其性能[J]. 储能科学与技术, 2021, 10(6): 2069-2076.

Yue SU, Xuhua LIU, Fanglei ZENG, Yurong REN, Bencai LIN. Preparation and properties of polyvinylidene fluoride/polyvinylidene fluoride sulfonate lithium/lithium salt composite solid electrolyte[J]. Energy Storage Science and Technology, 2021, 10(6): 2069-2076.

图/表 8

图 1

图 2

图 3

表 1

不同电解质的锂离子迁移数"

样品	I₀/mA	I_SS/mA	R₀/Ω	R_SS/Ω	$t L i +$
SPVDFLi-60	0.26	0.21	410	420	0.78
SPDVDFLi/LiTFSI-40	0.95	0.62	75	88	0.68
PVDF/LiTFSI	3.30	1.70	650	700	0.47

表 1

表 2

图 4

图 5

图6

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样品	拉伸强度/MPa	杨氏模量/MPa	断裂伸长率/%
SPVDFLi-60	2.3±0.3	13.7±0.6	23.0±0.2
SPVDFLi/LiTFSI-10	3.1±0.5	29.5±0.2	25.8±0.5
SPVDFLi/LiTFSI-20	4.0±0.2	14.8±0.9	33.7±0.4
SPVDFLi/LiTFSI-30	3.0±0.1	12.7±0.4	35.1±0.7
SPVDFLi/LiTFSI-40	4.2±0.2	16.5±0.3	56.5±0.1
PVDF/LiTFSI	8.0±0.4	55.2±0.2	35.8±0.2

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