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Water-Assisted Increase of Ionic Conductivity of Lithium Poly(acrylic acid)-Based Aqueous Polymer Electrolyte
ACS Applied Energy Materials ( IF 5.4 ) Pub Date : 2020-09-16 , DOI: 10.1021/acsaem.0c01765
Jae Hyun Park 1 , Sungyeb Jung 2 , Yeon Hwa Song 3 , Narayana R. Aluru 4 , Taehoon Kim 5 , Sang Bok Lee 5 , U Hyeok Choi 6 , Jaekwang Lee 2
Affiliation  

We propose a novel aqueous polymer electrolyte (APE) using a strongly hydrophilic poly(acrylic acid) (PAA) matrix containing mobile lithium counterions. The conductivity of this new PAA–Li+–water electrolyte increases dramatically (to 10–2 S/cm at 298 K) with the addition of water. This value is almost 100 times higher than those of nonaqueous electrolytes and solid-state electrolytes. From the molecular dynamics simulations, we find that the increase of ion conductivity originates from the close interplay between ions, water, and the polymers in the molecule level. The structural features (i.e., ion/water distribution around the polymer) and transport properties (i.e., diffusion coefficient and ionic conductivity) are systematically investigated along with the quantifications of the microscopic properties such as the binding index of the ion, hydration numbers, and the equilibrium distance between the ion and PAA monomer at various water-content conditions. In particular, the change in the conductivity according to water content, ϕWt, is divided into the diffusion-dominant regime at the low-water-content condition (ϕWt < 0.7) and the structure-dominant regime at the high-water-content condition (ϕWt ≥ 0.7). In the diffusion-dominant regime, the conductivity increases by diffusion enhancement proportional to the water content, while in the structure-dominant regime, the conductivity varies little due to the considerable reduction of the number density of Li ions. Namely, there exists an optimal water content, above which the effects of additional water become negligible. We believe that our innovative findings would provide significant advances in developing APE-based high-power and long-life lithium-ion batteries. Also, the proposed nontoxic and flexible APE could offer a promising solution for the development of flexible and wearable aqueous rechargeable lithium-ion batteries.

中文翻译:

水辅助提高锂基聚(丙烯酸)基水性聚合物电解质的离子电导率

我们提出了一种新型的水性聚合物电解质(APE),它使用了包含移动锂抗衡离子的强亲水性聚丙烯酸(PAA)基质。这种新型PAA–Li + –水电解质的电导率急剧增加(达到10 –2S / cm在298 K)并加水。该值几乎是非水电解质和固态电解质的100倍。从分子动力学模拟中,我们发现离子电导率的增加源自离子,水和分子水平上聚合物之间的紧密相互作用。系统地研究了结构特征(即,聚合物周围的离子/水分布)和传输特性(即,扩散系数和离子电导率)以及微观特性的量化,例如离子的结合指数,水合数和在各种含水量条件下离子与PAA单体之间的平衡距离。尤其是电导率随水分含量变化,ϕ Wt,在低水含量的条件被分为扩散主导制度(φ重量<0.7),并在高水含量的条件下的结构主导制度(φ重量≥0.7)。在以扩散为主的状态下,电导率通过与水含量成正比的扩散增强而增加,而在以结构为主的状态下,电导率由于Li离子数密度的显着降低而几乎没有变化。即,存在最佳水含量,在此之上,额外水的影响可忽略不计。我们相信,我们的创新发现将为开发基于APE的高功率和长寿命锂离子电池提供重大进展。同样,提出的无毒和柔性的APE可以为开发柔性和可穿戴的水性可充电锂离子电池提供有希望的解决方案。
更新日期:2020-10-26
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