PhD Thesis Defense: Baiheng Li

"Materials design and optimization for sodium-based solid-state batteries"

Abstract

Sodium-ion batteries (SIBs) are a promising candidate for next-generation energy storage solutions, especially in the case of grid energy storage applications due to raw material cost and availability for cathode, anode, and electrolyte materials. In addition, sodium (Na)'s similarity to lithium (Li) in terms of physicochemical and electrochemical properties is favorable for the design and development of SIBs with the convenient reference of current lithium-ion batteries (LIBs). However, many challenges remain to be resolved in order to harness sodium's much higher chemical reactivity comparing to lithium: for example, the cycle life and safety of SIBs leave a lot to be desired. To eliminate excessive side reactions between the electrodes and electrolyte in SIBs, one advantageous approach is the employment of solid-state electrolyte (SE). 

NASICON (Na_1+xZr₂Si_xP_3−xO₁₂) is a type of ceramic SE that has exceptional chemical stability when in direct contact with metallic Na, wide electrochemical voltage window, and fabrication methods that can potentially become scalable, which makes it a good option for Na solid-state batteries (SSBs). This thesis targets the shortcomings of NASICON SE, which first and foremost includes the poor wettability at the electrode-electrolyte interface. A grain boundary engineering strategy that resolves the electrode-electrolyte contact issue, which was used to create a stable Na SSB with proven cycle life of over 12,000 h. Additionally, to expediate the NASICON synthesis vis solid-state reaction, process control agents (PCAs) were investigated with the goal of shortening the milling time to 2/3 of original length. With optimized PCA species and concentration, this goal was achieved with improvements in physical and electrochemical properties. 

Na SSBs are very promising as a candidate for next-generation battery technology, especially for large-scale energy storage systems, where they would be appreciated for the low cost and high availability of raw materials and minimized fire risks. In the last section of this work, the engineering and economic barriers associated with popularizing energy storage systems beyond the current Li-ion chemistry. In summary, this thesis aims to bring Na SSBs closer to practical applications by making improvements both in electrochemical performance and scalability of production.

Thesis Committee

• Weiyang (Fiona) Li (chair)
• Ian Baker
• Jifeng Liu
• Hui (Claire) Xiong (Boise State University)

Contact

For more information, contact Thayer Registrar at thayer.registrar@dartmouth.edu .