Multifunctional solid polymer electrolytes for all-solid-state batteries

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Lithium ion batteries are found in many daily use devices such as smartphones, laptop and tablet computers, cordless tools, and electric vehicles. However, there are safety concerns about these batteries, because failure in these devices can lead to a fire. For safe and efficient operation, lithium ion battery components have many requirements such as ionic conductivity, electrochemical stability, mechanical robustness, processability and fire retardance. In this research project, the investigators will use a tunable chemical platform to address these simultaneous requirements. This battery system includes a polymer network base that is made of chain-like molecules bonded together to form a highly connected scaffold. The system also includes comb-like structures that consist of polymers extending off the network scaffold. Additional components, such as stabilizers or fire retardants, can be added to the end of the combs to impart the corresponding properties to the system. By changing the structure or composition of the network scaffold, the investigators will study how the material properties can be altered to optimize the overall performance of the system. Using the concepts learned during this project, the participants will develop two class modules for a course on nanostructured polymeric materials. Additionally, high school students and teachers, particularly from groups under-represented in STEM fields, will be involved in the research activities via the Summer Engineering Experience at Drexel Program.In this research project the investigators aim to design, synthesize, and implement a series of multifunctional and versatile comb-chain crosslinker based network solid polymer electrolytes (ConSPEs). The versatility element comes from the large number of functional groups found on the ends of the chains and cross-linkers, which provide fast cross-linking and an opportunity to add further components. Using this platform the investigators will tune network chemistry, architecture, mechanical and electrochemical properties to address the high performance electrolyte needs. Specifically, components will be added to target a given, desired solid electrolyte property. For example, poly(propylene carbonate) would improve voltage stability and transference number, while grafted halogenated moieties would improve fire retardance, solid electrolyte interface formation and cycling performance. The investigators will characterize the materials using oscillatory shear and classical tensile mechanical measurements, and small-length scale dependent mechanical properties will be assessed using quantitative nanomechanical mapping via atomic force microcopy. Electrochemical characterizations include ion conductivity via electrochemical impedance and cycling stability via cyclic voltammetry. After establishing a library of ConSPE materials, the investigators will select two differing materials and combine them into bilayer structures. Such asymmetric bilayer materials might be more capable than a uniform materials of meeting the different requirements of the anode- and cathode-facing sides of the solid electrolyte.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.