Electronic Thesis and Dissertation Repository

Thesis Format

Integrated Article

Degree

Master of Engineering Science

Program

Mechanical and Materials Engineering

Supervisor

Sun, Xueliang (Andy)

Abstract

The revolutionary rechargeable lithium-ion battery paves the way for environmentally-friendly applications such as electric vehicles. Nevertheless, further improvements are required to match or exceed the performance of conventional internal combustion engine vehicles, such as higher energy density, faster charging speed, longer lifetime, better safety and lower cost. Lithium layered nickel cobalt manganese oxides (NCM) are a popular choice of cathode material, but they still suffer from problems such as cation mixing, volume changes, microcracking, surface side reactions, high temperature performance issues and structural reconstruction. This thesis compares various NCM materials to figure out what guidelines should be followed to improve performance. The first section observes the impact of chemical composition, while the second section explores conventional polycrystalline versus single crystal morphology for NCM. It is shown that the stability and lifetime of NCM materials, and therefore battery performance, can be improved by using lower nickel composition and single crystal morphology.

Summary for Lay Audience

The revolutionary rechargeable lithium-ion battery paves the way for environmentally-friendly applications such as electric vehicles. Nevertheless, further improvements are required to match or exceed the performance of regular vehicles, such as higher energy density, faster charging speed, longer lifetime, better safety and lower cost. Lithium layered nickel cobalt manganese oxides (NCM) are a popular choice of cathode material, but they still suffer from problems such as cation mixing, volume changes, microcracking, surface side reactions, high temperature performance issues and structural changes. This thesis compares various NCM materials to figure out what guidelines can improve battery performance. The first section observes the impact of chemical composition, while the second section explores NCM particles made up of multiple crystals versus one single crystal. It is shown that the stability and lifetime of NCM materials, and therefore battery performance, can be improved by using lower amounts of nickel and using single crystals.

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