GOALI: Self-Assembled Multivalent Lithium Salts for Solid Polymer Electrolytes

技术概述：这个GOALI项目是天普大学、混合塑料和MaxPower公司之间的合作项目，它解决了一个基本问题，即是否有可能通过对纳米材料的自组装和聚合物中的锂离子扩散的理解，设计出具有高室温电导率（1 × 10-3 S/cm）和锂离子转移数（tLi+）的固体聚合物电解质（spe）。这样形成的spe将具有液体电解质的优点，而不会伴随挥发性、可燃性和枝晶形成等安全问题。多离子锂盐将由多八面体硅氧烷（POSS）纳米颗粒合成，并与聚氧化物（PEO）结合，因为初步数据表明这些spe具有更好的锂离子传输性能。多八面体硅氧烷是一种类似两面星的纳米粒子，一端是疏水性苯基，另一端是基于- si - o - bf3 - Li+的离子基。在形成的形态中，苯基团簇和- si - o - bf3 -基团朝向PEO相。吸电子的POSS笼和BF3基团使阴离子上的负电荷离域，使解离的Li+可以被周围的PEO基质溶剂化。PEO是完全无定形的，因此所得到的固体结构不是PEO结晶性的结果，而是苯基晶体和连接苯基簇和PEO链的-Si-O-BF3阴离子—Li+—O-H2CH2桥形成交联的结果。电导率的增强可能是这种形态的结果，其中Li+离子与几个-Si-O-BF3阴离子松散配合，并可能以较低的活化能沿界面区域迁移。初步数据显示离子电导率为3 × 10-4 S/cm，接近目标值1 × 10-3 S/cm， tli+ = 0.6。研究了提高Li+/苯基比的更好设计的多离子锂盐。目的是尽量减少维持无PEO结晶度的固体所需的非导电相的数量，并尽量增加溶剂化Li+离子的低Tg导电相的数量。形态学，力学和电化学性能将相互关联，以阐明有助于提高电导率的因素。本项目由美国国家科学基金会固体与材料化学计划资助。非技术总结：拟议研究的潜在影响是改进固体聚合物电解质，这将提高锂/锂离子电池在大型电能存储应用中的性能，如电动汽车/混合动力汽车或匹配波动电源（包括风能和太阳能）的输出与波动需求。固体聚合物电解质本质上比目前用于便携式设备的小型锂离子电池的挥发性液体电解质更安全。该研究将重点开发具有与当前液体电解质相当的离子电导率，但更安全，整体性能更好的新材料。材料合成将与混合塑料公司合作进行，该公司拥有该项目所需的专业知识和扩大规模的设施。该公司将与锂电池制造商MaxPower公司合作，对开发的新型固体聚合物电解质材料进行长期电池测试，以完成全面评估。本科生/研究生将在学术和工业环境中参与聚合物、有机和电化学的跨学科研究。

TECHNICAL SUMMARY:This GOALI project is a collaboration between Temple University, Hybrid Plastics, and MaxPower, Inc., and addresses the fundamental question of whether it is possible, using an understanding of the self-assembly of nanomaterials and lithium ion diffusion in polymers, to design solid polymer electrolytes (SPEs) that have both high room-temperature conductivity ( 1 x 10-3 S/cm) and lithium ion transference numbers, tLi+, that approach 1. The SPEs so formed will have the advantages of liquid electrolytes without the accompanying safety problems of volatility, flammability and dendrite formation. Multi-ionic lithium salts will be synthesized from polyoctahedral silsesquioxane (POSS) nanoparticles and combined with polyethylene oxide (PEO), since preliminary data indicate that these SPEs exhibit improved lithium ion transport properties. The polyoctahedral silsesquioxanes are Janus-like nanoparticles, with hydrophobic phenyl groups at one end and ionic groups based on -Si-O-BF3- Li+ at the other end. In the morphology that forms, the phenyl groups cluster and the -Si-O-BF3- groups orient towards the PEO phase. The electron withdrawing POSS cage and BF3 groups delocalize the negative charge on the anion so that the dissociated Li+ can be solvated by the surrounding PEO matrix. The PEO is completely amorphous, so that the resulting solid structure is not the result of PEO crystallinity but instead it is proposed to be the result of phenyl crystallites and crosslinks formed from -Si-O-BF3 anion--- Li+---O-H2CH2 bridges that connect the phenyl clusters and PEO chains. Enhanced conductivity may be the result of this morphology, in which Li+ ions are loosely coordinated to several -Si-O-BF3 anions, and may migrate along the interfacial regions with a lower activation energy. Preliminary data show ionic conductivities of 3 x 10-4 S/cm, close to the target value of 1 x 10-3 S/cm, with tli+ = 0.6. Better designed multi-ionic lithium salts in which the Li+/phenyl group ratio is increased will be investigated. The purpose is to minimize the amount of non-conductive phase needed to maintain a solid without PEO crystallinity and to maximize the amount of low Tg conductive phase with solvated Li+ ions. Morphology, mechanical and electrochemical properties will be correlated to elucidate the factors that contribute to enhanced conductivity. This project is supported by the NSF Solid State and Materials Chemistry Program.NON-TECHNICAL SUMMARY:The potential impact of the proposed research is improved solid polymer electrolytes that would enhance the performance of lithium/lithium ion batteries used in large electrical energy storage applications such as electric vehicles/hybrid electric vehicles or matching the output of fluctuating power sources including wind and solar with fluctuating demand. Solid polymer electrolytes are intrinsically safer than the volatile liquid electrolytes currently used in small lithium ion batteries for portable devices. The research will focus on the development of new materials which have ionic conductivities comparable to those of current liquid electrolytes, but are safer and have better performance overall. Material synthesis will be performed in collaboration with Hybrid Plastics, Inc., a company with the expertise and scale-up facilities necessary for the project. Long-term battery testing for complete evaluation of the new solid polymer electrolyte materials that are developed will be accomplished through collaboration with MaxPower, Inc, a lithium battery manufacturer. Undergraduate/graduate students will participate in interdisciplinary research in polymer-, organic- and electro-chemistry both in academic and industrial environments.