UNS: Ion transport in semicrystalline solid polymer electrolytes

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#1510092Li, ChristopherAlthough the current state-of-the-art lithium ion batteries (LIBs) have been widely used in consumer electronics, because of the relatively low theoretical capacity, they cannot meet the need of applications such as electrical vehicles, autonomous aircrafts, etc. The theoretical capacity of LIBs can be greatly improved by replacing graphite with lithium metal as the anode to fabricate a lithium metal battery (LMB). To materialize LMB, the biggest obstacle is the associated fire or explosion hazards. In order to achieve safe operation for LMB, solid polymer electrolytes (SPEs) with good room temperature ionic conductivity and high shear modulus are needed. The goal of this proposed research is to understand the ion transport mechanism in semicrystalline SPEs for energy device applications. The proposed semicrystalline SPEs could be a viable candidate for fabricating next generation safe LMBs. In this proposal, through critical analysis of the past four decades of research on SPE, an overlooked question regarding the detailed mechanism of the crystalline morphology effect on ionic conductivity in SPEs has been raised. To answer this challenging question, the PI proposes a series of semicrystalline SPEs with precisely controlled crystal size, orientation, and chain folding. This novel approach, for the first time, decouples the intertwine structural (tortuosity) and dynamic (tethered chain confinement) effects on ion transport in SPE. It also demonstrates that tortuosity associated with crystalline morphology plays a critical role on ion transport in semicrystalline SPEs. The proposed research will provide a new strategy to design SPEs for energy device applications: Compared with existing SPEs, the proposed semicrystalline SPE with controlled crystal morphology and orientation is advantageous because crystalline polymer is mechanically 3-4 orders of magnitude stronger than amorphous rubbery polymers, the intrinsic two-phase model (crystalline and amorphous) associated with semicrystalline SPE addresses the needs for two performance measures, the mechanical properties and the high ionic conductivity, respectively. The proposed research aims to tackle a challenging problem in the energy research field. If successful, the project will lead to a new type of SPEs, which enables safe operation of lithium metal batteries, a grand challenge facing the energy research community. These proposed educational activities encompass a broad impact. First, the proposed plan will help bridge the existing gap between levels of educational developments by involving high school students and teachers in research activities through a number of mentoring programs. Second, due to the high population of under-represented groups in the Philadelphia region, the proposed outreach program will be specifically geared towards encouraging the participation of under-represented populations. Third, the proposed research will be publicized through scientific media and public workshops. The dissemination of this information along with hands-on experiences for secondary education teachers will result in more informed teachers capable of educating the future by establishing collaborative efforts with school districts in the surrounding Philadelphia region.