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The goal of this work is to further understand the relationships between porous electrode microstructure and mass transport properties. This understanding allows us to predict and improve cell performance from fundamental principles. The investigated battery systems are the widely used rechargeable Li-ion battery and the non-rechargeable alkaline battery. This work includes three main contributions in the battery field listed below. Direct Measurement of Effective Electronic Transport in Porous Li-ion Electrodes. An accurate assessment of the electronic conductivity of electrodes is necessary for understanding and optimizing battery performance. The bulk electronic conductivity of porous LiCoO2-based cathodes was measured as a function of porosity, pressure, carbon fraction, and the presence of an electrolyte. The measurements were performed by delamination of thin-film electrodes from their aluminum current collectors and by use of a four-line probe. Imaging and Correlating Microstructure To Conductivity. Transport properties of porous electrodes are strongly related to microstructure. An experimental 3D microstructure is needed not only for computation of direct transport properties, but also for a detailed electrode microstructure characterization. This work utilized X-ray tomography and focused ion beam (FIB)/scanning electron microscopy (SEM) to obtain the 3D structures of alkaline battery cathodes. FIB/SEM has the advantage of detecting carbon additives; thus, it was the main tomography tool employed. Additionally, protocols and techniques for acquiring, processing and segmenting series of FIB/SEM images were developed as part of this work. FIB/SEM images were also used to correlate electrodes' microstructure to their respective conductivities for both Li-ion and alkaline batteries. Electrode Microstructure Metrics and the 3D Stochastic Grid Model. A detailed characterization of microstructure was conducted in this work, including characterization of the volume fraction, nearest neighbor probability, domain size distribution, shape factor, and Fourier transform coefficient. These metrics are compared between 2D FIB/SEM, 3D FIB/SEM and X-ray structures. Among those metrics, the first three metrics are used as a basis for SG model parameterization. The 3D stochastic grid (SG) model is based on Monte Carlo techniques, in which a small set of fundamental inter-domain parameters are used to generate structures. This allows us to predict electrode microstructure and its effects on both electronic and ionic properties.

A large number of Li-ion batteries used today will reach their End-Of-Life (EOL) in a few years. After their EOL, the recovery of their precious elements is required. By applying physical separation, a fraction with fine particle size is left behind which is known as Black Mass (BM). BM is rich in LIB precious materials, including Li metal oxides and graphite. In this study, pyrometallurgical recycling of BM is investigated. In the first step, the BM high-temperature transformations are being studied, focusing on reducing Li metal oxides, Li evaporation, and F removal. In the second step, Fe and Cu oxides are added to the BM to investigate how the graphite remaining in the BM can be used as a reducing agent and form alloys with Co and Ni. The use of mechanical activation as a mean to improve the kinetics of the reactions and the efficiency of the reduction reaction was also studied. To model the experiments in this study, thermodynamic softwares (FactSage and HSC) were also employed.

The Lithium-ion (Li-ion) battery is one of the major topics currently studied as a potential way to help in reducing greenhouse gas emissions. Major car manufacturers are interested in adapting the Li-ion battery in the power trains of Plug-in Hybrid Electric Vehicles (PHEV) to improve fuel efficiency. Materials currently used for Li-ion batteries are LiCoO2 (LCO) and graphite—the first materials successfully integrated by Sony into Li-ion batteries. However, due to the high cost and polluting effect of cobalt (Co), and the low volumetric capacity of graphite, new materials are being sought out. LiFePO4 (LFP) and SnO2 are both good alternatives for the cathode and anode materials in Li-ion batteries. But, to create high-performance batteries, nano-sized carbon-coated particles of LFP and SnO2 are required. The present work attempts to develop a new synthesis method for these materials: organic template-assisted synthesis for three-dimensionally ordered macroporous (3DOM) LFP and porous SnO2. With the newly developed synthesis, highly pure materials were successfully synthesized and tested in Li-ion batteries. The obtained capacity for LFP was 158m Ah/g, which is equivalent to 93% of the theoretical capacity. The obtained capacity for SnO2 was 700 mAh/g, which is equivalent to 90% of the theoretical capacity. Moreover, Hybrid Pulse Power Characterization (HPPC) was used to test LFP and LCO for comparison and feasibility in PHEVs. HPPC is generally used to test the feasibility and capacity fade for PHEVs. It simulates battery use in various driving conditions of PHEVs to study pulse energy consumption and regeneration. In this case, HPPC was conducted on a half-cell battery for the first time to study the phenomena on a single active material, LFP or LCO. Based on the HPPC results, LFP proved to be more practical for use in PHEVs.

The battery separator is a component of the conventional battery that for long has been overlooked. Just because it’s the only inactive component, doesn’t mean it’s any less important for the battery cell. Recent trends point to an immense growth of the electrical vehicle-industry, and by so, also the lithium-ion battery separators market. This is because the lithium-ion battery is the most common battery type in commercial electrical vehicles. In one of the major manufacturing processes of the separator, mineral oil is used, to achieve a porous film. This study aims to evaluate different oils interaction with the polymer resin in the manufacturing process. Since most oils used in the battery separator industry today use paraffin rich oils, oils with different naphthenic content is tested to find correlations between the oils properties and the crystallinity or the porosity. No correlations for either the porosity or the crystallinity could be made to the oil’s properties. The images taken with the SEM was not enhanced enough to study the pores themselves or the pore structure of the films. For future studies it is recommended to collect more data to identify outliers so more accurate values are obtained. The methodology needs to be verified to ensure the procedure is reproducible. For the study of the pores and the pore structure, an FE-SEM should be used to achieve greater quality enhancement images on the surface of the films. / Batteri separatorn är en komponent i det konventionella batteriet som länge har förbisetts. Bara för att den är en inaktiv komponent, betyder inte att den är mindre viktig för battericellens prestation. Trender idag pekar mot en enorm tillväxt inom elbils-industrin, och med det även litium-jon batteriseparatorns marknad. Det är för att litium-jon batteriet är det batteriet som vanligen används kommersiellt idag i elbilar. I en av de två stora industriella tillverkningsprocesserna används olja för att åstadkomma en porös film. Denna studie syftar på att utvärdera olika oljors interaktion med polymeren i denna tillverkningsprocess. Eftersom de flesta batteriseparator-industrier idag använder paraffinrik olja så testas oljor med olika mycket naftalensikt innehåll för att hitta korrelationer mellan oljornas egenskaper och kristalliniteten eller porositeten hos filmerna. Inga korrelationer för porositeten eller kristalliniteten kunde göras till oljornas egenskaper. Bilderna tagna med SEM var ej tillräckligt förstorade för att kunna studera vare sig porstorleken eller porstrukturen hos filmerna. För framtida studier rekommenderas att samla in mer data för att kunna utskilja ”outliers” i datan, för att erhålla mer korrekta värden. Metodiken måste även verifieras för att säkerställa att proceduren är reproducerbar. För att studera porerna och porstrukturen, borde en FE-SEM användas för att få mer förstorade bilder med bättre kvalité på filmernas yta.

Indiana University-Purdue University Indianapolis (IUPUI) / Recycling valuable cathode material from end-of-life (EOL) Li-ion batteries (LIBs) is essential to preserve raw material depletion and environmental sustainability. Direct recycling reclaims the cathode material without jeopardizing its original functional structures and maximizing return values from spent LIBs compared to other regeneration processes. This work employed two chemically delithiated lithium cobalt oxide (LCO) cathodes at different states of health (SOH), which are analogous to the spent cathodes but free of any impurities, to investigate the effectiveness of cathode regeneration. The material and electrochemical properties of both delithiated SOHs were systematically examined and compared to pristine LCO cathode. Further, those model materials were regenerated by a hydrothermal-based approach. The direct cathode regeneration of both low and high SOH cathode samples restored their reversible capacity and cycle performance comparable to pristine LCO cathode. However, the inferior performance observed in higher current density (2C) rate was not comparable to pristine LCO. In addition, the higher resistance of regenerated cathodes is attributed to lower high-rate performance, which was pointed out as the key challenge of the cathode recycling process. This study provides valuable knowledge about the effectiveness of cathode regeneration by investigating how the disordered, lithium-deficient cathode at different SOH from spent EOL batteries are rejuvenated without changing any material and electrochemical functional properties.

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