SURI 2023: Mechanical Properties of Thin-Film Solid-State Battery Electrolytes Produced in Open-Air

This research experience aligns with my chosen Grand Challenges theme of sustainability. Batteries are constantly used in everyday life. Innovations in energy storage are critical to the transition from fossil fuels to alternative, sustainable energy sources. Improved energy storage could transform the transportation sector by enabling greater reliance on cost-effective electric vehicles. Recent battery-related fires indicate that safety remains a challenge for lithium-ion batteries. These batteries, in addition to being flammable and posing a safety hazard, require raw materials that are difficult to obtain and whose extraction processes are harmful to the environment and human rights.

My research illustrates how solid-state electrolytes (SSEs) offer a superior alternative to the lithium-ion batteries currently used. Solid-state electrolyte batteries are leak-proof, energy-dense, flame-resistant, contain no toxic organic solvents, and are well-suited for scalable manufacturing. Under the mentorship of Dr. Nick Rolston, this project focuses on developing printable, ink-based materials for solid-state SSEs that can be deposited over large areas via low-cost solution-processing methods, achieving high energy density while reducing material costs and simplifying manufacturing.

My research aimed to support the development of an SSE battery material that can store energy more efficiently and reliably than current lithium-ion batteries. I learned to print battery materials, characterize ionic and electronic conductivity and defectivity using microscopy, and produce battery devices. I also coached other new research assistants on producing test slides. This research is beneficial to me as a GCSP Student because it has deepened my understanding of how batteries are manufactured and how they can be used to develop more sustainable and safer systems. The sustainable challenges addressed by our SSEs research will help prevent electrolyte degradation in lithium-ion batteries, benefiting the world. This research project aligns with my interests, as it demonstrates how we can further develop products for global use. The research not only deepened my understanding of and interest in renewable energy but also provided me with hands-on experience in an area I enjoy.

SURI 2024: LiPON Thin-Film Solid-State Battery Electrolytes Produced in Open-Air

This fall, I used the Double Cantilever Beam (DCB) method to measure the fracture energy of 1 µm LiPON samples and 2 µm Ga‑LLZO:Li₂O samples by analyzing the load–displacement response during crack propagation. The LiPON samples exhibited an average fracture energy of 16.69 J/m² with a standard deviation of 5.88 J/m², while the Ga‑LLZO:Li₂O samples averaged 52.23 J/m² with a standard deviation of 1.76 J/m² (Figure 1). These values differed significantly from the results I obtained during the summer, where LiPON averaged 41 J/m², and LLZO averaged 27 J/m². The discrepancy, especially for LiPON, prompted a deeper investigation into whether the measured cracks propagated within the films or along the epoxy–glass interface.

Because both LiPON and LLZO samples were transparent, it was difficult to visually confirm the fracture path. I attempted optical microscopy, but the images could not reliably distinguish between the thin‑film material and the epoxy used to bond the samples to the glass substrates. To address this limitation, I completed training on the GD‑OES system, which can detect elemental composition at the surface of a sample.

However, the GD‑OES results were inconsistent. Some LiPON samples showed lithium on both sides of the glass, but it was often present only in isolated regions. To verify whether the system was functioning properly, I analyzed a LiPON substrate directly. The results were only partially consistent: most samples showed trace lithium, but the presence of phosphorus, nitrogen, and oxygen varied unpredictably. Some samples contained phosphorus but no nitrogen or oxygen; others contained nitrogen but lacked phosphorus or oxygen; and a few contained combinations of these elements but not all three.

In contrast, the Ga‑LLZO:Li₂O samples produced clear and consistent GD‑OES signatures. All samples contained lithium, gallium, and oxygen, which aligned with the expected composition. This increased my confidence that the LLZO samples were correctly identified, whereas the LiPON samples may not have been labeled correctly. Based on the inconsistent elemental data and the unexpected fracture energies, I cannot be fully confident that the LiPON samples received from Switzerland were genuine LiPON.

This research process taught me how essential it is to anticipate complications when beginning a project and to adapt quickly when they arise. In my case, this meant learning a new characterization technique (GD‑OES) and using it to validate the materials I was testing. Although the GD‑OES results did not fully resolve the issue, they provided valuable insight into the sample composition and confirmed that at least trace elements of the films were present on both sides of the fractured glass.

Overall, this semester’s work strengthened my ability to test and evaluate samples produced by external collaborators and reinforced the importance of verifying material identity before drawing conclusions. My experiences this summer and fall have also clarified my academic and professional interests. I enjoyed both research periods, but I preferred the summer work because it involved both developing and testing the materials, an approach that aligns more closely with my chemical engineering background. This combined experience has increased my confidence in pursuing a graduate degree in engineering and has shown me that I thrive in research environments that integrate materials synthesis, characterization, and mechanical evaluation.

Research Experience #3:  FA23 WAESCO Grant

Research Proposal: Design of Thermomechanically Robust Metal Halide Perovskite Photovoltaic Devices

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