Szabó Ákos, Ershov Denis, Ábrahám Ágnes, Kiss Éva, Szarka Györgyi, Felhősi Ilona, Gyarmati Benjámin, Domján Attila, Iván Béla, Kun Robert
Polymer Chemistry and Physics Research Group, Institute of Materials and Environmental Chemistry, HUN-REN Research Centre for Natural Sciences, Magyar tudósok krt. 2., Budapest H-1117, Hungary.
Department of Chemical and Environmental Process Engineering, Faculty of Chemical Technology and Biotechnology, Budapest University of Technology and Economics, Műegyetem rkp. 3, Budapest H-1111, Hungary.
ACS Appl Energy Mater. 2024 Dec 9;7(24):12036-12047. doi: 10.1021/acsaem.4c02519. eCollection 2024 Dec 23.
Amphiphilic copolymers of comb-like poly(poly(ethylene glycol) methacrylate) (PPEGMA) with methyl methacrylate (MMA) synthesized by one-pot atom transfer radical polymerization were mixed with lithium bis (trifluoromethanesulfonyl) imide salt to formulate dry solid polymer electrolytes (DSPE) for semisolid-state Li-ion battery applications. The PEO-type side chain length (EO monomer's number) in the PEGMA macromonomer units was varied, and its influence on the mechanical and electrochemical characteristics was investigated. It was found that the copolymers, due to the presence of PMMA segments, possess viscoelastic behavior and less change in mechanical properties than a PEO homopolymer with 100 kDa molecular weight in the investigated temperature range. In contrast to the PEO homopolymer, it was found that no crystallization of the copolymers occurs in the presence of the Li-salt. Solid-state NMR and cross-polarization NMR studies revealed that no crystallization (i.e., ion-pair formation) of the Li-salt occurs in the case of the copolymer samples at ambient temperatures; thereby, no phase separation takes place, in contrast to the reference PEO homopolymer sample, which resulted in fairly good ionic conductivity of the copolymers at lower temperatures. The temperature-dependent Li-ion conductivity analyses showed that the conductivity of the copolymers falls in the 10-10 S/cm range, which is typical for polyether-type DSPEs, but the much lower mass fraction of EO monomers in the copolymers provides the same ionic conductivity values than that of the PEO homopolymer. From a large-scale practical point of view, this clearly indicates reduced Li-salt usage if such copolymer matrices are used instead of PEO homopolymer. Moreover, linear sweep voltammetry (LSV) polarization measurements showed that the PPEGMA-MMA copolymer electrolytes can exhibit a 200-300 mV broader electrochemical stability window than the PEO homopolymer, which is crucial in designing high energy density semisolid-state Li-ion batteries.
通过一锅法原子转移自由基聚合合成的梳状聚（聚乙二醇甲基丙烯酸酯）（PPEGMA）与甲基丙烯酸甲酯（MMA）的两亲性共聚物，与双（三氟甲磺酰）亚胺锂盐混合，以制备用于半固态锂离子电池应用的干固体聚合物电解质（DSPE）。改变PEGMA大分子单体单元中PEO型侧链长度（EO单体数量），并研究其对机械和电化学特性的影响。研究发现，由于存在PMMA链段，共聚物具有粘弹性行为，并且在研究的温度范围内，其机械性能变化比分子量为100 kDa的PEO均聚物小。与PEO均聚物相反，发现在锂盐存在下共聚物不会发生结晶。固态NMR和交叉极化NMR研究表明，在室温下，共聚物样品中锂盐不会发生结晶（即离子对形成）；因此，与参考PEO均聚物样品不同，不会发生相分离，这使得共聚物在较低温度下具有相当好的离子电导率。温度依赖性锂离子电导率分析表明，共聚物的电导率在10-10 S/cm范围内，这是聚醚型DSPE的典型值，但共聚物中EO单体的质量分数低得多，却能提供与PEO均聚物相同的离子电导率值。从大规模实际应用的角度来看，这清楚地表明，如果使用这种共聚物基体代替PEO均聚物，则锂盐用量会减少。此外，线性扫描伏安法（LSV）极化测量表明，PPEGMA-MMA共聚物电解质的电化学稳定性窗口比PEO均聚物宽200-300 mV，这对于设计高能量密度半固态锂离子电池至关重要。
