Preparation of all-solid-state polymer electrolyte by ultraviolet cross-linking method

doi:10.11949/0438-1157.20211460

Abstract

Abstract:

In the application of all-solid-state polymer electrolyte (SPE), the bottleneck is how to meet the requirements of ion conductivity and mechanical strength simultaneously. Aiming at the above problem, this paper adopts the reversible addition fragmentation chain transfer (RAFT) solution polymerization technology to synthesize SPEs with different chain structures. The SPEs apply the cyclohex-3-enylmethyl acrylate (CEA) as post-crosslinking monomer and the poly(ethylene glycol) methyl ether acrylate (PEGMA) as ion-conducting monomer. A chemically cross-linked network structure was formed by the “click chemistry” reaction between the double bond on the cyclohexene in CEA and the mercaptan. The prepared triblock copolymer electrolyte has independent ion-conducting blocks while the crosslinking monomers concentrating at both ends of the molecular chain, thus meeting the demands of mechanical strength and ionic conductivity simultaneously. The prepared triblock copolymer electrolyte presented ionic conductivity of 6.13×10^-5 S/cm at 60℃. The lithium iron phosphate/lithium (LiFePO₄/Li) all-solid-state battery using the prepared triblock copolymer electrolyte presented specific discharge capacity of 139.1 mAh/g after 130 cycles at 0.5 C. The retention rate was 97.8% while the coulombic efficiency remained above 99.0%, showing good electrochemical performance.

Key words: electrochemistry, electrolytes, polymers, all-solid-state lithium battery, polymer electrolytes, RAFT radical polymerization, relationship between chain structure and properties

摘要：

制约全固态聚合物电解质开发应用的瓶颈在于如何同时实现高离子电导率与高机械强度。采用可逆加成断裂链转移（RAFT）溶液聚合技术，以3-环己烯-1-亚甲基丙烯酸酯（CEA）为后交联单体，聚乙二醇甲醚丙烯酸酯（PEGMA）为导离子单体，制备了不同链结构的全固态聚合物电解质，再通过硫醇-烯烃之间的“点击化学”反应形成化学交联网络结构。所制备的三嵌段共聚物电解质具有独立的导离子中间嵌段，且交联单体位于分子链两端，从而能够同时满足离子电导率与机械强度的要求。该三嵌段共聚物电解质在60℃下的离子电导率为6.13×10^-5 S/cm，并应用于磷酸亚铁锂/锂（LiFePO₄/Li）全固态电池。所得电池在0.5 C下循环130圈后，放电比容量为139.1 mAh/g，容量保持率为97.8%，库仑效率高于99.0%，显示出良好的电化学性能。

关键词: 电化学, 电解质, 聚合物, 全固态锂电池, 聚合物电解质, RAFT自由基聚合, 链结构与性能关系

CLC Number:

TQ 152

Zhenan ZHENG, Xiang GAO, Yingwu LUO, Jie HUANG. Preparation of all-solid-state polymer electrolyte by ultraviolet cross-linking method[J]. CIESC Journal, 2022, 73(1): 441-450.

郑哲楠, 高翔, 罗英武, 黄杰. 紫外光交联法制备全固态聚合物电解质[J]. 化工学报, 2022, 73(1): 441-450.

Figures/Tables 15

Fig.1 Scheme of synthesis of cyclohex-3-enylmethyl acrylate (CEA)

Fig.2 1H NMR spectrum of P(PEGMA-co-CEA)

Fig.3 Scheme of UV crosslinking reaction of the synthesized polymer electrolyte and PETMP

Fig.4 DSC curve of PPEGMA homopolymer

Fig.5 DSC curves and DSC derivative curves of TRI and RAN

Fig.6 Determination of the linear viscoelastic range of TRI

Fig.7 Relationship between G*, tanδ and frequency of TRI and RAN

Fig.8 Rate performance of LiFePO4/Li cell using TRI and commercial liquid electrolyte (The test temperature for TRI was 60℃, while that for liquid electrolyte was 30℃)

Fig.9 Charge/discharge profiles of LiFePO4/Li cells using TRI (a) and commercial liquid electrolyte (b) under different test rates

Fig.10 Nyquist plots of LiFePO4/Li cells using TRI and commercial liquid electrolyte after rate performance tests and at discharge state (the test temperature for TRI was 60℃, while that for liquid electrolyte was 30℃; the inset image is a partial enlargement of the semicircular)

Fig.11 Cycling performance of LiFePO4/Li cell using TRI and its corresponding coulombic efficiencies (the test temperature was 60℃ and the test rate was 0.5 C for both charge and discharge procedures)

Fig.12 Nyquist plots of LiFePO4/Li cell using TRI after different amounts of cycles and at discharge state (the test temperature was 60℃, the inset image is a partial enlargement of the semicircular)

Fig. A1 1H NMR spectrum and structural formula (inset) of cyclohex-3-enylmethyl acrylate (CEA)

Fig.A3 1H NMR spectrum and structural formula (inset) of poly(ethylene glycol) methyl ether acrylate (PEGMA)

Fig.A2 Gas chromatogram of cyclohex -3-enylmethyl acrylate (CEA)

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