Cycling of solid-state lithium-ion batteries with high-loading cathodes at low stack pressure

Tran, Huy

Permalink

https://hdl.handle.net/2142/127520 Copy

Description

Title

Cycling of solid-state lithium-ion batteries with high-loading cathodes at low stack pressure

Author(s)

Tran, Huy

Issue Date

2024-12-13

Director of Research (if dissertation) or Advisor (if thesis)

Braun, Paul V

Department of Study

Materials Science & Engineerng

Discipline

Materials Science & Engr

Degree Granting Institution

University of Illinois at Urbana-Champaign

Degree Name

M.S.

Degree Level

Thesis

Keyword(s)

• Solid-state Battery
• High-loading Cathode
• Low Stack Pressure

Language

eng

Abstract

Solid-state lithium batteries (SSLBs) are poised to revolutionize energy storage by offering enhanced safety and higher energy density compared to conventional lithium-ion batteries. Unlike their liquid electrolyte counterparts, SSLBs eliminate the risk of leakage and flammability, making them particularly attractive for applications in electric vehicles, portable electronics, and renewable energy systems. However, achieving stable cycling performance with high-loading cathodes under low stack pressure for SSLBs remains a significant challenge due to issues such as poor ionic contact and mechanical instability at the solid-solid interfaces. Addressing these limitations requires the development of advanced electrolyte materials, innovative interface engineering techniques, and optimized cell architectures to enhance the longevity and efficiency of SSLBs while maintaining their superior safety and energy density advantages. SSLBs are poised to revolutionize energy storage by offering enhanced safety and higher energy density compared to conventional lithium-ion batteries. However, achieving stable cycling performance with high-loading cathodes under low stack pressure remains a significant challenge due to issues such as poor ionic contact and mechanical instability at the solid-solid interfaces. In this dissertation, the challenges associated with cycling solid-state lithium-ion batteries with high-loading cathodes at low stack pressure are thoroughly examined and addressed. In Chapter 2, the influence of cell chemistry on cycling performance is investigated to optimize long-term stability. The cathode material utilized in this study is electroplated dense LiCoO₂, featuring a specific crystallographic orientation that has previously demonstrated benefits in reducing interfacial resistance at the cathode-electrolyte interface and improving the cycling performance of solid-state batteries (SSBs). For the anode, the lithium-indium system was selected due to its alloy structure, which promotes uniform lithium deposition, minimizes dendrite formation, and facilitates rapid lithium diffusion. Pre-lithiation of the anode significantly enhances cycle life by mitigating structural degradation during lithium plating and stripping processes. The alloy phase composition, as predicted by the phase diagram, is successfully validated through XRD analysis. In addition, a thin-film solid electrolyte bilayer was employed for its couple electrochemical stability. Among the options considered, LIC (Li3InCl6) was selected as the electrolyte against the cathode, while LPSCl (Li6PS5Cl) emerged as the optimal choice for contact with the anode over LYC (Li3YCl6), owing to its self-limiting reaction with interfacial lithium. This interaction forms a thin, stable solid electrolyte interphase (SEI) with lower impedance, contributing to enhanced performance and durability of the battery system. Thus, the cell configuration used in the next part of this study was chosen to be LCO|LIC|LPSC|LiIn. In Chapter 3, the influence of stack pressure on cell cycling performance was systematically investigated. To ensure accuracy, the pressing system used in this study was thoroughly tested to confirm that the applied pressures remained consistent with the target values. Following validation of the system, cells were subjected to cycling under various stack pressures to evaluate their electrochemical performance. The results revealed that lower stack pressures led to a decline in both initial coulombic efficiency and capacity retention, with more pronounced capacity degradation observed over time. Despite this, the cells still demonstrated remarkable stability at low stack pressure (1 MPa), achieving excellent capacity retention of over 83% after 100 cycles. Additionally, the impact of volume changes associated with lithium plating and stripping on the overall stack pressure was also discussed. The challenges of achieving stable cycling with high-loading cathodes under low stack pressure are explored and addressed in Chapter 4. Initial attempts using the cell fabrication procedure outlined in Chapter 2 yielded suboptimal results, as the voltage profiles indicated signs of anodic void formation. To enhance the contact between the anode and solid electrolyte, the cell fabrication process was modified by increasing the pressure during assembly, a step referred to as the anode contact formation (ACF) process. Implementing this improved ACF procedure resulted in exceptional cycling performance, with over 75% capacity retention after 200 cycles at a current density of 2.18 mAh cm⁻², even at low operating temperatures. However, when a composite cathode replaced the electrodeposited dense cathode, the cells exhibited severe capacity degradation. The inclusion of a carbon additive (Super P) in the composite mixture provided little improvement, as rapid capacity fading occurred during the early stages of cycling. These findings indicate that a complex interplay of performance-limiting factors affects the composite cathode's stability, highlighting the need for continued advancements in cathode material design and interface engineering to overcome the limitations observed with composite cathodes. Finally, Chapter 5 provides a comprehensive summary of the key findings regarding the impact of stack pressure on electrochemical performance, emphasizing the critical role of cathode configuration in achieving stable cycling with high active material loading at low stack pressures. The analysis highlights the intricate relationship between stack pressure, interface stability, and cycling efficiency, particularly for dense and composite cathode configurations. Additionally, the chapter broadens the scope to identify areas for future research. It underscores the necessity of developing a deeper understanding of the chemo-mechanical failures responsible for performance degradation, including phenomena like particle isolation, interfacial void formation, and cracking. This knowledge will be essential to inform strategies for improving cell design and optimizing solid-state battery performance at low stack pressures. Ultimately, the findings and proposed directions aim to guide advancements toward practical and scalable solid-state battery technologies.

Graduation Semester

2024-12

Type of Resource

Thesis

Handle URL

https://hdl.handle.net/2142/127520

Copyright and License Information

Copyright 2024 Huy Tran

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