Date of Award

5-31-2018

Document Type

Campus Access Dissertation

Degree Name

Doctor of Philosophy (PhD)

Department

Chemistry/Physical/Analytical Chemistry

First Advisor

Jonathan Rochford

Second Advisor

Michelle Foster

Third Advisor

Niya Sa

Abstract

A novel method for the partial graphitization of activated carbon materials is presented. Activated carbon powders were progressively heat treated under an argon environment up to 2100 0C. The carbon’s surface area and crystallinity were shown to be tunable from the choice of heat treatment temperature. The changes in the carbon’s surface area and average pore diameter were elucidated with the use of a nitrogen sorption technique. An increase in the carbon’s graphitic nature by the association of single graphene layers into elongated, stacked crystallite formations was revealed with powder X-ray diffraction. The effects of the treatments on the solid electrolyte interface layer of a lithium-ion capacitor negative electrode were studied by the use of chronoamperometric and chronopotentiometric formation cycles.

A Design of Experiment statistical method was applied to lithium-ion electrolyte solvent component selection in an attempt to increase the low temperature (-30 0C) discharge performance of a lithium-ion battery. The best performing electrolyte combination showed a low temperature discharge capacity increase of 300% from the current standard electrolyte used in production. The effects of varying the solvent component proportions on the solid electrolyte interface layer solid electrolyte interface (SEI) layer of a lithium-ion battery were investigated by the use of impedance spectroscopy and X-ray photoelectron spectroscopy. The effects of solvent component proportions on cycle life performance were studied with an accelerated aging high temperature cycling method.

The properties of 20 absorbent glass mat (AGM) separators from 4 different manufacturers were investigated by use of numerous porometric measurement techniques (mercury intrusion, capillary flow, liquid extrusion, and dynamic wetting). Interconnected pore networks were discovered and shown to determine the separator’s wetting properties. Separator surface profile, binder content, and particle size distribution were characterized with a scanning electron microscope. The effects of compression on AGM single cell formation gas generation were studied with the use of a novel AGM battery test box and gas measurement device developed at UW-Milwaukee under Dr. Deyang Qu. AGM formation gas generation was shown to be highly dependent on the separator’s compressed thickness. A pattern of incomplete formation voltage profiles was identified and allows for the early detection of incomplete battery formation during manufacturing.

Comments

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