Date of Award

4-2020

Degree Name

Master of Science in Engineering

Department

Chemical and Paper Engineering

First Advisor

Dr. Qingliu Wu

Second Advisor

Dr. Paul Fleming

Third Advisor

Dr. Qiang Yang

Keywords

Lithium-ion batteries, cellulose, cellulose fibers, cellulose nanocrystals, separator

Access Setting

Masters Thesis-Open Access

Abstract

During the past two decades, lithium-ion batteries (LIBs) have gained great success in the field of portable devices, and currently, are penetrating to the market of vehicles. Compared to the fast development of LIBs, little efforts have been dedicated to the separator, which is one of the most important components of LIBs. Primarily, the lithium-ion battery separator has two functions, one is to prevent direct contact between the positive and negative electrodes, and the other is to provide a path for effective ionic transportation. Currently, the separator market of LIBs is dominated by polyolefin materials such as polypropylene, polyethylene, and their combinations. However, the low thermal stability and poor wettability of polyolefin separators by the electrolyte result in state-of-art (SOA) LIBs with low power density, narrow range of operating temperature, and high cost. In this thesis, a novel cellulose-based membrane will be developed and be utilized as a separator of LIBs to address aforementioned issues. The well-established methods for papermaking will be adopted to fabricate two types of cellulose-based membrane separators; one is made of cellulose fibers and the other with cellulose fibers and cellulose nanocrystals (CNC). The effect of processing parameters, such as the solvents, ratio of CNC to cellulose fiber, and filtering method on the properties of membranes will be investigated. The achieved membranes will be evaluated by using advanced techniques, including force tensiometer, scanning electron microscopy, electrochemical characterizations, etc., to demonstrate superior properties of cellulose separators developed here.

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