This thesis studies the performance of solid polymer lithium batteries from room temperature to elevated temperatures using mainly electrochemical techniques, with emphasis on the bulk properties of the polymer electrolyte and the electrode-electrolyte interfaces. Its contributions include: 1) Demonstrated the relationship between polymer segmental motion and ionic conductivity indeed has a Vogel-Tammann-Fulcher (VTF) dependence, and improved the conductivity of the graft copolymer electrolyte (GCE) by almost an order of magnitude by changing the ion-conducting block from poly(oxyethylene) methacrylate (POEM) to a block with a lower glass transition temperature \((T_g)\) poly(oxyethylene) acrylate (POEA). 2) Identified the rate-limiting step in the battery occurs at the cathode-electrolyte interface using both full cell and symmetric cell electrochemical impedance spectroscopy (EIS), improved the battery rate capability by using the GCE as both the electrolyte and the cathode binder to reduce the resistance at the cathode-electrolyte interface, and used TEM and SEM to visualize the polymer-particle interface (full cells with \(LiFePO_4\) as the cathode active material and lithium metal as the anode were assembled and tested). 3) Applied the solid polymer battery to oil and gas drilling application, performed high temperature (up to 210°C) cycling (both isothermal and thermal cycling), and demonstrated for the first time, current exchange between a solid polymer electrolyte and a liquid lithium metal. Both the cell open-circuit-voltage (OCV) and the overall GCE mass remained stable up to 200°C, suggesting that the GCE is electrochemically and gravimetrically stable at high temperatures. Used full cell EIS to study the behavior of the various battery parameters as a function of cycling and temperature. 4) Identified the thermal instability of the cell was due to the reactivity of lithium metal and its passivation film at high temperatures, and used Li/GCE/Li symmetric cell EIS to study the thermal stability of the anode-electrolyte interface, which was responsible for the fast capacity fade observed at high temperatures. 5) Proposed a new electrolyte material and a new battery design called polymer ionic liquid (PIL) battery that can dramatically improve the safety, energy density, and rate capability of rechargeable lithium batteries. / Engineering and Applied Sciences

<p>This dissertation describes the design and characterization of a lightweight hydrogen reactor coupled to a proton exchange membrane fuel cell for portable power delivery. The system is intended to recharge portable batteries in the absence of an established electrical power supply. The presented work can be divided into two endeavors; the first being an investigation of various hydrogen generation pathways and the second being the design, fabrication, and testing of a system to house hydrogen generation and deliver electrical power.</p> <p>Two hydrogen storage materials are considered for this work: ammonia borane and sodium borohydride. Organic acids are investigated for their ability to accelerate the hydrolysis of either material and generate hydrogen on-demand. In the case of ammonia borane, organic acids are investigated for a secondary role beyond reaction acceleration, serving also to purify the gas stream by capturing the ammonia that is produced during hydrolysis. Organic acids are found to accelerate the hydrolysis of ammonia borane and sodium borohydride with relative indifference towards the purity of water being used. This is advantageous as it allows the user to collect water at the point of use rather than transport highly pure water for use as a reactant. Collecting water at the point of use increases system energy density as only ammonia borane or sodium borohydride and an organic acid are transported with the system hardware.</p> <p>A custom hydrogen reactor is developed to facilitate hydrolysis of ammonia borane or sodium borohydride. The reactor is paired with a fuel cell to generate electrical power. The rate of hydrogen being generated by the system is modulated to match the fuel cell’s consumption rate and maintain a relatively constant pressure inside the reactor. This allows the system to satisfy a wide range of hydrogen consumption rates without risking over pressurization. The system is shown to produce up to 0.5 sLpm of hydrogen without exceeding 30 psia of hydrogen pressure or a temperature rise greater than 35°C.</p><p>The envisioned use for this system is portable battery charging for expeditionary forces within the United States military. This application informed several design choices and is considered when evaluating technological maturation. It is also used to compare the designed system to existing energy storage technologies.</p>