Nanowhisker filled solid polymer electrolytes

技术总结聚合物电解液比目前锂电池中使用的液体电解液更安全、更清洁、更灵活。它们与锂金属电极一起使用是一个有吸引力的可能性，因为它们比液体电解液更坚硬。为此，PEO基电解液的硬度不足以防止树枝晶的形成，这限制了锂金属的使用。它们的导电性也不够高，不适合实际使用。不幸的是，刚性和导电性是反向相关的，因为锂的运动与聚合物的运动是耦合的，任何试图通过更快的聚合物运动来提高导电性的尝试都会导致刚性的降低。该项目基于隧道状聚合物/盐结构促进锂的快速运动的想法，最近使用单晶电解质演示了这一点。它将用一套基于纤维素纳米晶须的高纵横比纳米薄膜来利用这一运动，这被认为是为了促进隧道结构。这些填料提供了可控的表面化学、功能化程度和纵横比，从而形成了理想的模型体系。在以前工作的基础上，将特别关注共晶成分，在这种成分下，金属合金的导电性和机械性能都得到了改善。在此成分下，类金属合金形成两个晶相相间的片层状大尺度结构。聚合物电解质的这种结构的形成还没有被研究。该项目将使用循环热处理作为一种手段，在聚合物/盐共熔中产生类似的图案，这将使隧道状结构进一步远离填料表面。理想的电解液应该有填充物，从而有锂的传导路径，沿着垂直于电极的方向排列。已经确定，可以使用磁场、电场和剪切来对准纤维素纳米晶须，该项目将研究这三种方法在不破坏从填料表面延伸出来的聚合物/盐图案的情况下对准的有效性。该项目将促进对表面化学和长宽比在纳米填料与聚合物/盐体系相互作用中的作用、控制聚合物共晶结构的因素以及控制聚合物/盐混合物中填料排列的最佳方法的了解。非技术型聚合物电解液比目前手机和笔记本电脑锂电池中使用的液态电解液更安全、更清洁、更灵活。它们是在已经使用锂离子电池技术的车辆上使用的一个有吸引力的可能性。聚合物电解质对这一应用很有吸引力，因为它们允许技术进步，将每次充电的寿命从100英里延长到400英里。目前，随着这些技术的进步，聚合物电解质是不可行的，也不能获得足够的功率放电来满足车辆应用。这两个所需的改进目前是相互排斥的：尝试实现更长的充电寿命将减少功率，反之亦然。这个项目中的科学将与长寿命和高功率的目标脱钩。它是基于聚合物/锂盐混合物在无机表面附近出现的独特特征。它将使用非常小的填料，提供更大的表面积，并改变表面化学和填料对齐，以获得最佳结果。这项工作的成果将使科学家能够独立地致力于提高功率和寿命，从而推动锂离子电池替代能源技术的进步。美国在科学研究方面处于世界领先地位，但在科学、技术、工程和数学领域却难以填补职位空缺。联合创新学院是一个全国性的组织，它试图通过以一种有趣的方式向孩子们介绍STEM概念来缩小这种脱节，在关键时期，他们正在决定自己喜欢什么和擅长什么。该计划是专门为11岁的学生设计的，这些学生可能已经认定自己在数学和科学方面不擅长。InnoWorks是一个由学生运营的组织，教授、研究生和本科生在其中筹集资金，开发课程，并准备和举办夏令营。这个项目将开始宾夕法尼亚州立大学的一个分会，从而向孩子们展示科学是有趣的。

TECHNICAL SUMMARYPolymer electrolytes are safer, cleaner, and more flexible than liquid electrolytes currently used in Li batteries. They are an attractive possibility for use with Li metal electrodes because they are stiffer than liquid electrolytes. For this purpose, PEO-based electrolytes are not stiff enough to prevent dendrite formation, which limits use of Li metal. They also do not have high enough conductivity to be practical. Unfortunately, stiffness and conductivity are inversely related because Li motion is coupled to polymer motion, and any attempt to improve conductivity through faster polymer motion results in decreased stiffness. This project is based on the idea that tunnel-like polymer/salt structures promote fast Li motion, recently demonstrated using single-crystal electrolytes. It will harness this motion with a set of high aspect ratio nanofillers based on cellulose nanowhiskers, which are hypothesized to promote the tunnel structures. These fillers offer controllable surface chemistry, degree of functionalization and aspect ratio, thus forming an ideal model system. Building on prior work, particular attention will be paid to the eutectic composition, at which improved electrical conductivity and mechanical properties are established in metal alloys. At this composition, the analogous metal alloys form large-scale structures with the two crystal phases in alternating lamellae. The formation of such structures for polymer electrolytes has not been investigated. The project will use cyclic thermal treatments as a means to produce similar patterns in polymer/salt eutectics, which will extend the tunnel-like structures further from the filler surface. The ideal electrolyte would have fillers, and thus Li conduction pathways, aligned along the direction normal to the electrodes. It is established that cellulose nanowhiskers can be aligned using magnetic fields, electric fields, and shear, and the project will investigate all three for effectiveness at alignment without disrupting polymer/salt pattering extending from the filler surface. The project will promote understanding of the roles of surface chemistry and aspect ratio on interaction of nanoscale fillers with polymer/salt systems, the factors controlling polymer eutectic structures, and the best ways to control filler alignment in polymer/salt mixtures. NON-TECHNICAL SUMMARYPolymer electrolytes are safer, cleaner, and more flexible than liquid electrolytes currently used in the Li batteries in cell phones and laptop computers. They are an attractive possibility for use in vehicles, where Li ion battery technology is already used. Polymer electrolytes are attractive for this application because they allow technical advancements that extend the charge lifetime from 100 to 400 miles per charge. Polymer electrolytes are not currently feasible with these technical advancements, nor can they attain power discharge sufficient for vehicle applications. These two required improvements are currently mutually exclusive: attempts to enable longer charge lifetime will reduce power and vice versa. The science in this project will decouple the objectives of long lifetime and high power. It is based on unique features of polymer/Li salt mixtures that occur near inorganic surfaces. It will use very small fillers, which provide more surface area, and alter the surface chemistry and filler alignment to obtain optimal results. The results of this work will allow scientists to work on increasing power and lifetime independently, thus promoting advancement of the alternative energy technology of Li ion batteries. The U.S. is a world leader in scientific research, yet struggles to fill jobs in the sciences, technology, engineering and mathematics. The United InnoWorks Academy is a national organization that seeks to narrow this disconnect by introducing STEM concepts in a fun way to kids in the critical period where they are deciding what they like and what they are good at. The program is specifically designed towards students who, at age 11, may have already decided that they are not good at math and science. InnoWorks is a student-run organization in which professors, graduate students and undergraduate students raise funds, develop curriculum, and prepare and run summer camps. This project will start a Penn State Chapter, thus showing kids that science is fun.