Microstructure Engineering of All-Solid-State Composite Electrodes

Driven by the immense global demand for energy, the development of advanced energy storage systems is critical. Solid-state batteries (SSBs) have emerged as promising alternatives to traditional lithium-ion batteries for next-generation energy storage due to their enhanced safety and higher energy densities. Composite cathodes are pivotal in determining the areal capacity and specific energy of SSBs, making their design, fabrication and characterization an important research direction. This dissertation focuses on electrode microstructure engineering and the development of novel organic active materials for high-performance SSBs. It begins with a review of key challenges associated with composite cathodes and current solutions. Chapter 2 explores strategies using organic cathodes to address these challenges from microstructural, mechanical, and chemical perspectives, along with a discussion on mechanical failures in conversion cathodes and potential optimization strategies. Chapter 3 and Chapter 4 focus on constructing favorable microstructures in organic cathodes. We identified that the unfavorable organic cathode microstructure is attributed to the mechanical mismatch between the soft organic compound and the relatively hard solid electrolyte. By employing solvent-assisted processing approach or manipulating the hardness of sulfide-based solid electrolyte, we successfully transformed the microstructure from “electrolyte-in-active material” to “active material-in-electrolyte”, thereby improving both cathode fraction and electrode-level energy density. Chapter 5 and Chapter 6 introduce novel conductive organic materials for solid-state batteries. First, we demonstrate that high malleable organic materials can accommodate mechanical stress from active material volume change during cycling. The intimate interfacial contact between organic material and solid electrolyte enables operation under low stack pressure. Second, we examine the physical properties of lithium-containing organic materials, revealing that the reduced form of organic material exhibits improved chemical stability when combined with sulfide electrolyte. This highly reversible interface within the cathode ensures long-term cycling stability. Finally, I address mechanical failure in sulfur-based conversion cathodes in Chapter 7, where delamination at the cathode-solid electrolyte interface leads to significant polarization during cycling at low stacking pressure. To mitigate this issue, a strategy using FeS2 particles coated with organic materials is proposed to enhance cycling stability.

Name thesis:degree_name

Doctor of Philosophy

Discipline thesis:degree_discipline

Materials Engineering

Grantor

University of Houston

Year dc:date.issued

2024

Author dc:creator

• Chen, Zhaoyang

Advisor dc:contributor.advisor

• Yao, Yan

Committee members dc:contributor.committeemember

• Canepa, Pieremanuele
• Zhao, Lihong
• Dasgupta, Neil
• Bocarsly, Joshua D.

• Chemistry, Organic
• Engineering, Materials Science
• Energy

Language dc:language.iso

en

Handle dc:identifier.uri

https://hdl.handle.net/10657/18277

OAI identifier oai:identifier

oai:uh-ir.tdl.org:10657/18277