Degree

Doctor of Philosophy (PhD)

Department

Department of Mechanical & Industrial Engineering

Document Type

Dissertation

Abstract

The growing concerns over the limitations and environmental impact of conventional lithium-ion batteries (LIBs) have driven the search for more sustainable energy storage solutions. Metal-free batteries, such as those utilizing ammonium ions (NH₄⁺), offer a compelling alternative due to their non-toxic nature, abundant availability, and unique electrochemical properties. The NH₄⁺ ion's lower molar mass and distinct tetrahedral structure enable efficient charge transfer and intercalation, distinguishing it from traditional metal ions and potentially improving battery performance. Self-charging batteries, which integrate piezoelectric materials to harvest ambient mechanical energy, present a significant advancement in energy storage technology. By capturing and converting mechanical energy into electrical power, these batteries eliminate the need for external charging, enhancing both the sustainability and convenience of portable electronic devices. Together, metal-free and self-charging batteries represent a critical step toward more eco-friendly and efficient energy solutions. This research investigates four complementary advancements in metal-free and self-charging battery systems. In the first chapter, the use of methanol as an antisolvent in a 4 m ammonium acetate electrolyte enables metal-free ammonium-ion batteries (AIBs) to operate at temperatures as low as –20 °C. Coupled with a polyaniline (PANI) anode and polypyrrole (PPy) cathode, the system demonstrates strong capacity retention and stability under extreme conditions. The second chapter presents flexible quasi-solid-state AIBs employing an edible xanthan-gum hydrogel and 3 m ammonium sulfate electrolyte, achieving reliable performance under bending and twisting through the PANI/PPy electrode pairing. The third chapter introduces a self-charging zinc-ion battery that leverages a piezoelectric PVDF–ZnO separator to convert mechanical energy into electrical power. Using a QSS 3 m Zn(CF₃SO₃)₂ electrolyte with a Zn anode and FeVO₄ cathode, the device shows continuous recharging and practical self-sustaining operation. The fourth chapter develops two fully metal-free aqueous AIBs using perylenetetracarboxylic dianhydride (PTCDA) as the organic anode, paired with either PANI or PPy cathodes in 1 m and 3 m (NH₄)₂SO₄ electrolytes. Benefiting from the small hydration radius and high mobility of NH₄⁺, both systems exhibit fast ion diffusion, strong cycling stability, and excellent rate recovery, successfully powering small electronic devices and demonstrating their potential for safe, lightweight, and sustainable energy storage.

Date

2-10-2026

Committee Chair

Wang Ying

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