Department of Chemical and Biomolecular Engineering , University of California , Berkeley , California 94720 , United States.
Energy Storage and Distributed Resources Division , Lawrence Berkeley National Laboratory , Berkeley , California 94720 , United States.
J Phys Chem B. 2019 Dec 19;123(50):10858-10867. doi: 10.1021/acs.jpcb.9b09517. Epub 2019 Dec 9.
Nonaqueous polyelectrolyte solutions have recently been proposed as potential battery electrolytes due to their unique ability to tune the mobility of the anion relative to that of the electrochemically active lithium ion. This could potentially be used to study the effect of concentration polarization during battery charge, a major limiting factor in achieving fast charge rates that is caused by high anion mobility. An important consideration in the design of polyelectrolyte solutions for battery applications is the solubility of the polymer in battery-relevant carbonate blend solvents. Little is understood from a transport perspective, however, about the importance of designing the polymer to be solvophillic or if it is sufficient to obtain solubility through the incorporation of appended ions alone (as with polystyrene sulfonate in water). Using a model polysulfone-based system without added salt, we investigate the conductivity, viscosity, and diffusion of polyelectrolyte solutions over a range of concentrations and molecular weights in dimethyl sulfoxide (DMSO) and water. In both solvents, sulfonated polysulfone is readily soluble and the charged group is known to dissociate, but the neutral backbone polymer is only soluble in DMSO. We find marked differences in the transport behavior of polymer solutions prepared from the two solvents, particularly at high concentrations. Comparing this transport behavior to that of the monomer in solution demonstrates a larger decrease in lithium motion in DMSO than in water, even though the bulk viscosity in water increases far more rapidly. This study sheds light on the important parameters for optimizing polyelectrolyte solution transport in different solvents.
非水多聚电解质溶液最近因其能够调节阴离子相对于电化学活性锂离子的迁移率的独特能力而被提议作为潜在的电池电解质。这可能用于研究电池充电过程中浓度极化的影响，这是实现快速充电速率的主要限制因素，其原因是阴离子迁移率较高。在设计用于电池应用的聚电解质溶液时，一个重要的考虑因素是聚合物在与电池相关的碳酸酯混合溶剂中的溶解度。然而，从传输的角度来看，对于设计亲溶剂聚合物的重要性或仅通过引入附加离子（如聚苯乙烯磺酸盐在水中）获得溶解度是否足够了解甚少。我们使用无外加盐的模型聚砜基系统，在二甲基亚砜（DMSO）和水中研究了一系列浓度和分子量的聚电解质溶液的电导率、粘度和扩散。在这两种溶剂中，磺化聚砜都很容易溶解，已知带电基团会离解，但中性骨架聚合物仅在 DMSO 中溶解。我们发现，由两种溶剂制备的聚合物溶液的传输行为存在明显差异，尤其是在高浓度下。将这种传输行为与溶液中单体的传输行为进行比较表明，DMSO 中锂离子的运动下降幅度大于水中，尽管水中的整体粘度增加得更快。这项研究阐明了在不同溶剂中优化聚电解质溶液传输的重要参数。
