Abstract

Batteries are a key energy storage solution for a sustainable energy future. They provide carbon free power to portable devices such as mobile phones, laptops, and even electric vehicles. With further improvements to battery performance¸ the diversity of machines that can be electrified will increase. Solid state batteries (SSBs) have the potential to provide much greater energy density compared to conventional batteries. Greater energy density will help address the power to size ratio limitation of conventional batteries. Despite improvements in these major areas, SSBs still face some significant operational challenges. The study herein focuses on improving the performance of a full cell composed of an NMC (nickel-manganese-cobalt) composite cathode, sulfide solid electrolyte (lithium-phosphorus-sulfur-chloride), and a lithium metal anode. The cell performance was analyzed by changing the ratio of materials used in the composite cathode, which is made up of NMC, carbon black and the sulfide electrolyte material, LPSCL. In addition, the fabrication pressure of the cell was varied to identify conditions for stable cycling. Performance results showed that compared to other ratios a 60:35:5 percent split between NMC, LPSCL and carbon black showed a low resistance of 650 Ohms. In addition, a fabrication pressure of 25 MPa resulted in a long cycle time of 5 days with minimal decay in charge and discharge voltage. In order to better understand the fundamental principles behind the experimental results a battery model was created by customizing Ansys-Fluent with User-Defined-Functions (UDFs). The model was used to study the effect of contact resistance and ionic diffusion coefficient on the battery performance. The results of the model show that the diffusion coefficient affects the electrode utilization while the contact resistance influences the battery voltage. In particular, the results show that SSBs can be improved by ensuring that the contact resistance is less than the electrode resistance. Similarly, the high (350 MPa) and low (2.5 MPa) fabrication pressure test results show a voltage limit of 3.8 V unlike the 25 MPa test. The voltage limit is indicated by the battery shorting, meaning that the contact resistance was greater than the electrode resistance. Another way to improve SSBs shown by the model is that by increasing the diffusion coefficient of the electrolyte, the cathode utilization will increase. Similarly, the 60:35:5 ratio cathode composition test showed low resistance, meaning that it is easier for ions travel to the cathode, resulting in greater cathode utilization.

Library of Congress Subject Headings

Solid state batteries--Quality control; Solid state batteries--Materials; Nickel-manganese alloys

Publication Date

12-6-2023

Document Type

Thesis

Student Type

Graduate

Degree Name

Mechanical Engineering (MS)

Department, Program, or Center

Mechanical Engineering

College

Kate Gleason College of Engineering

Advisor

Isaac Perez Raya

Advisor/Committee Member

Matthew Ganter

Advisor/Committee Member

Rui Liu

Campus

RIT – Main Campus

Plan Codes

MECE-MS

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