PRISM :: Browsing by Author "Thangadurai, Venkataraman"

Browsing by Author "Thangadurai, Venkataraman"

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Aqueous Batteries for Large-Scale Energy Storage and Carbon Removal Applications
(2024-08-08) Iyapazham Vaigunda Suba, Prathap; Thangadurai, Venkataraman; Karan, Kunal; Shi, Yujun; Shimizu, George; Roberts, Edward (Ted) PL; Kuss, Christian
Aqueous batteries are safe and environmentally friendly energy storage devices, suitable for intermittent renewable energy sources and carbon removal applications. However, these batteries are hindered by the low operating potential which leads to limitation in energy density. In this thesis, aqueous battery chemistry concept is applied for two different applications such as: a redox-flow battery transformation to an all-gel battery and a seawater-battery for carbon removal application. Flexible, scalable, and low-cost energy storage solutions are required for the widespread use of renewable energy and the mitigation of climate change. In this regard, redox flow batteries are scalable due to their ability to decouple power and energy; however, the commercial applications of these batteries are limited by expensive ion-selective membranes. An auxiliary electrode (AE) mediated membrane-free redox battery concept was demonstrated and different AE materials were screened for their application in vanadium based redox battery. In an AE mediated membrane-free vanadium redox battery, the Coulombic efficiency of the system was limited to 36%. The low Coulombic efficiency observed in AE based battery was mitigated by using a gel-battery design approach in which Bi/BiOCl and V4+/V5+ redox couples were utilized in a gel-based architecture. The Bi/BiOCl conversion reaction based redox couple was demonstrated to work reversibly against traditional vanadium-based redox pair in an aqueous electrolyte. Redox active materials in this cell design are in the gel form, and a traditional membrane or a separator is not required. This proof-of-concept all-gel battery delivered 0.9 V with a volumetric energy density of 22.14 Wh L-1. For carbon removal applications, an aqueous battery with seawater electrolyte was studied. In this battery, iron phosphate (FePO4) electrode was utilized to manipulate ions in different seawater aliquots to generate sodium hydroxide, a base to use in ocean alkalinity enhancement. Electrochemical analysis, Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD) and X-ray Photoelectron Spectroscopy (XPS) revealed that Na+ ions can be reversibly intercalated in FePO4. The alkalinity titration was used to determine the increase in alkalinity of seawater. The results indicated that a 16% increase in alkalinity was achieved in 15 ml of synthetic seawater over a period of 3.5 hours (one cycle) using the FePO4 electrode coupled with Pt electrode. A seawater electrolyte based battery with Ni(OH)2/NiOOH redox reaction in place of Pt electrode coupled with FePO4 electrode was studied. The battery delivered a potential of 0.6 V and the galvanostatic cycling experiments revealed that the battery can operate in seawater electrolyte for 50 cycles with 94% Coulombic efficiency.
Open Access
Carbon Formation on Stainless Steel 304H in the Convection Section of an Ethane Cracking Plant
(Taylor & Francis, 2015) Ramezanipour, Farshid; Singh, Anand; Paulson, Scott; Farag, Hany; Birss, Viola; Thangadurai, Venkataraman
Open Access
Ceria-Based Anodes for Next Generation Solid Oxide Fuel Cells
(2015-05-01) Mirfakhraei, Behzad; Birss, Viola; Thangadurai, Venkataraman
Mixed ionic and electronic conducting materials (MIECs) have been suggested to represent the next generation of solid oxide fuel cell (SOFC) anodes, primarily due to their significantly enhanced active surface area and their tolerance to fuel components. In this thesis, the main focus has been on determining and tuning the physicochemical and electrochemical properties of ceria-based MIECs in the versatile perovskite or fluorite crystal structures. In one direction, BaZr0.1Ce0.7Y0.1M0.1O3-δ (M = Fe, Ni, Co and Yb) (BZCY-M) perovskites were synthesized using solid-state or wet citric acid combustion methods and the effect of various transition metal dopants on the sintering behavior, crystal structure, chemical stability under CO2 and H2S, and electrical conductivity, was investigated. BZCY-Ni, synthesized using the wet combustion method, was the best performing anode, giving a polarization resistance (RP) of 0.4 Ω.cm2 at 800 oC. Scanning electron microscopy and X-ray diffraction analysis showed that this was due to the exsolution of catalytic Ni nanoparticles onto the oxide surface. Evolving from this promising result, the effect of Mo-doped CeO2 (nCMO) or Ni nanoparticle infiltration into a porous Gd-doped CeO2 (GDC) anode (in the fluorite structure) was studied. While 3 wt. % Ni infiltration lowered RP by up to 90 %, giving 0.09 Ω.cm2 at 800 oC and exhibiting a ca. 5 times higher tolerance towards 10 ppm H2S, nCMO infiltration enhanced the H2S stability by ca. 3 times, but had no influence on RP. In parallel work, a first-time study of the Ce3+ and Ce4+ redox process (pseudocapacitance) within GDC anode materials was carried out using cyclic voltammetry (CV) in wet H2 at high temperatures. It was concluded that, at 500-600 oC, the Ce3+/Ce4+ reaction is diffusion controlled, probably due to O2- transport limitations in the outer 5-10 layers of the GDC particles, giving a very high capacitance of ca. 70 F/g. Increasing the temperature ultimately diminished the observed capacitance, likely as the chemical reduction of GDC at high temperatures is irreversible.
Open Access
Characteristics of a Novel Alkali Flame Ionization Detector as an Air Sensor for Volatile Organonitrogen Compounds
(2023-05-05) Mogenson, Cole Mitchell; Thurbide, Kevin; Kimura-Hara, Susana; Anikovskiy, Max; Thangadurai, Venkataraman
This thesis describes the introduction and characterization of a novel alkali flame ionization detector (AFID) for use as an air sensor for organonitrogen compounds without any chromatographic separation. Using a planar channelled quartz design, a simple, lightweight architecture for the portable device is presented, which yields a sensitive and selective response toward nitrogen-containing analytes over hydrocarbons. For instance, the AFID sensor offers a detection limit of 30 pg N/s and a selectivity for nitrogen response over carbon of nearly two orders of magnitude. Further, the nitrogen response was linear over the 1000-fold range of concentrations investigated. Relative to a flame photometric detector (FPD) device also used in a sensor mode under optimal conditions, the AFID was observed to provide over a 160 times greater S/N value for nitrogen analytes with a selectivity of nitrogen over carbon that was about 16.6 times larger. When using the AFID and FPD sensors in tandem, it was found that the response ratio of the simultaneous signals generated by each produced characteristic signal ratio values that more clearly identified the presence or absence of nitrogen in unknown analytes. The AFID sensor was also used to detect organonitrogen analytes in several sample matrices. Results indicate that signal response was largely unaffected by these potentially interfering sample conditions, and thus this method could be a valuable approach for portable air sensing of nitrogen compounds.
Open Access
Chemically Stable Proton Conducting Doped BaCeO3 -No More Fear to SOFC Wastes
(Springer Science and Business Media LLC, 2013-07-04) Kannan, Ramaiyan; Singh, Kalpana; Gill, Sukhdeep; Fürstenhaupt, Tobias; Thangadurai, Venkataraman
Development of chemically stable proton conductors for solid oxide fuel cells (SOFCs) will solve several issues, including cost associated with expensive inter-connectors and long-term durability. Best known Y-doped BaCeO3 (YBC) proton conductors-based SOFCs suffer from chemical stability under SOFC by-products including CO2 and H2O. Here, for the first time, we report novel perovskite-type Ba0.5Sr0.5Ce0.6Zr0.2Gd0.1Y0.1O3?? by substituting Sr for Ba and co-substituting Gd + Zr for Ce in YBC that showed excellent chemical stability under SOFC by-products (e.g., CO2 and H2O) and retained a high proton conductivity, key properties which were lacking since the discovery of YBCs. In situ and ex- situ powder X-ray diffraction and thermo-gravimetric analysis demonstrate superior structural stability of investigated perovskite under SOFC by-products. The electrical measurements reveal pure proton conductivity, as confirmed by an open circuit potential of 1.15?V for H2-air cell at 700°C and merits as electrolyte for H-SOFCs.
Open Access
Comparative Evaluation of Coated and Non-Coated Carbon Electrodes in a Microbial Fuel Cell for Treatment of Municipal Sludge
(MDPI AG, 2019-03-16) Nandy, Arpita; Sharma, Mohita; Venkatesan, Senthil Velan; Taylor, Nicole; Gieg, Lisa; Thangadurai, Venkataraman
This study aims to provide insight into the cost-effective catalyst on power generation in a microbial fuel cell (MFC) for treatment of municipal sludge. Power production from MFCs with carbon, Fe2O3, and Pt electrodes were compared. The MFC with no coating on carbon generated the least power density (6.72 mW·m?2) while the MFC with Fe2O3-coating on carbon anodes and carbon cathodes generated a 78% higher power output (30.18 mW·m?2). The third MFC with Fe2O3-coated carbon anodes and Pt on carbon as the cathode catalyst generated the highest power density (73.16 mW·m?2) at room temperature. Although the power generated with a conventional Pt catalyst was more than two-fold higher than Fe2O3, this study suggests that Fe2O3 can be investigated further as an efficient, low-cost, and alternative catalyst of Pt, which can be optimized for improving performance of MFCs. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry (CV) results demonstrated reduced resistance of MFCs and better charge transfer between biofilm and electrodes containing coated anodes compared to non-coated anodes. Scanning electron microscopy (SEM) was used to analyze biofilm morphology and microbial community analysis was performed using 16S rRNA gene sequencing, which revealed the presence of known anaerobic fermenters and methanogens that may play a key role in energy generation in the MFCs.
Open Access
Correction: Synthesis and characterization of novel Li-stuffed garnet-like Li5+2xLa3Ta2?xGdxO12 (0 ? x ? 0.55): structure–property relationships
(Royal Society of Chemistry (RSC), 2017-06-15) Basset, Dalia M. Abdel; Mulmi, Suresh; E-Bana, Mohammed S.; Fouad, Suzan S.; Thangadurai, Venkataraman
Correction for ‘Synthesis and characterization of novel Li-stuffed garnet-like Li5+2xLa3Ta2?xGdxO12 (0 ? x ? 0.55): structure–property relationships’ by Dalia M. Abdel Basset, et al., Dalton Trans., 2017, 46, 933–946.
Open Access
Designing Electrolytes and Electrode-electrolyte Interfaces for Next-Generation Lithium Metal Batteries
(2021-08-26) Zhou, Chengtian; Thangadurai, Venkataraman; Shimizu, George; Yujun, Shi
State-of-the-art lithium-ion batteries (LIBs) are approaching their energy density limits and thus may not be the answer to the ever-increasing demand for higher specific energy density in today’s energy storage and power applications. Li metal is considered the ultimate anode material due to its ultra-high specific capacity 3860 mAh g-1, more than 10 times higher than lithiated graphite. Solid-state electrolytes (SSEs) provide a potential solution to advance the performance of Li metal batteries (LMBs). However, the device integration of SSEs, especially Li-stuffed garnet, is exceptionally challenging. Another critical aspect for LMBs is to limit excess Li metal at the anode. In this thesis, the interface between Li metal anode and Li-stuffed garnet Li6.5La2.9Ba0.1Zr0.4Ta1.6O12 is investigated. Poor contact between Li and garnet is identified as the reason for high interfacial resistance. A viable surfactant-assisted wet chemical method to deposit ZnO layer on Li-stuffed garnet is reported to reduce the interfacial resistance to as low as 10 Ω cm2. A composite polymer-ceramic electrolyte (CPE) for room temperature solid-state Li-S battery (SSLSB) is demonstrated. The CPE has low interfacial resistance against both Li metal anode and sulfur cathode. An engineered sulfur-Ketjen black(S@KB) composite cathode is coupled with CPE to demonstrate a SSLSB with a pronounced specific capacity of 1108 mAh g−1 and areal capacity of 1.77 mAh cm−2. As CPE is prepared by a solution casting method, lean solvent confinement affects the morphological structure and ionic conductivity of CPE. A higher amount of solvent retention leads to higher ionic conductivity but at the cost of membranes’ mechanical properties. In order to study anode-free Li-metal batteries (AFLMBs), a special coin cell configuration is designed with high compression. The high pressure leads to more stable cycling performance, providing a more accurate assessment of AFLMBs. A carbonate-glyme hybrid electrolyte for AFLMB is demonstrated with capacity retention of 73% for 50 cycles. The hybrid electrolyte possesses a unique solvation structure, where diglyme solvates both Li-ions and film-forming additive, while carbonates dilute the mixture, enabling facile ion migrations.
Open Access
Developing Porous Water Stable Metal Phosphonates for CO2 Capture Applications
(2016) Mah, Roger K; Shimizu, George; Marriott, Robert; Thangadurai, Venkataraman; Maeda, Kazuyuki
Porous solid sorbents have emerged as a promising class of materials for CO2 capture applications. A subclass of solid sorbents, metal-organic frameworks (MOFs), has been thoroughly investigated towards implementation into CO2 capture systems, owing to high tailorability from an inherently modular nature. The crux of conventional carboxylate-based MOFs has been stability against hydrolytic cleavage in the presence of elevated temperature and humidity. This thesis investigated the development of water stable phosphonate MOFs using the trigonal 1,3,5-tris(phosphonophenyl)benzene (H6L1) as the ligand coordinated to trivalent and tetravalent metals. The first metal investigated was Sn4+, which required significant efforts towards enhancing crystallinity. An ordered material for SnH2L1 (CALF-28) was achieved through solvothermal reaction followed a humidity exposure step. After the harsh humidity treatment, CALF-28 remained porous albeit with a decreased surface area. The second framework investigated utilized La3+ producing single crystals of LaH3L1 (CALF-29). Upon exposure to mild humidity treatment, CALF-29 decomposed resulting in significant loss of surface area revealing CALF-29 had no stability against hydrolytic cleavage. The final metal investigated with L1 was Zr4+ to produce ZrH2L1 (CALF-31). After repeated exposures to harsh humidity, CALF-31 remained porous with only a minor surface area drop. CALF-28 and CALF-31 were evaluated as potential CO2 capture sorbents and revealed the strengths of solid sorbents against the traditional monoethanolamine benchmark using calculations developed during this work. Finally, coordination of 1,3,5-tris(phosphonobiphenyl)benzene (H6L2) with Zr4+ provided insights into the effect of extending the L1 ligand. From the preliminary results, the potential advantages of H6L2, namely increased functionalization sites to accommodate polarizing groups, were discussed in the context of enhancing the CO2 capture potential of frameworks formed using trigonal trisphosphonates.
Open Access
Developing Solid Composite Polymer Electrolytes and Unveiling Layered Oxide Cathodes through Machine Learning for Sodium-Ion Batteries
(2024-05-21) Salari, Hirbod; Thangadurai, Venkataraman; Salahub, Dennis R.; Dolgos, Michelle; Sabharwal, Mayank
Solid-state sodium-ion batteries (ss-SIBs) are becoming a viable substitute for traditional lithium-ion batteries, offering a sustainable and cost-efficient option for future energy storage needs. The primary advantage is the abundant availability and lower cost of sodium compared to lithium. The advancement of ss-SIBs depends on achieving superior electrochemical, mechanical, interfacial, and thermal stability in solid electrolytes and optimal cathode selection. Solid polymer electrolytes (SPEs) are particularly promising due to their flexibility and potential for enhancement, despite challenges such as low ionic conductivity and high interfacial resistance. This thesis introduces a solid composite polymer electrolyte (SCPE) aimed at enhancing sodium-ion conductivity in ss-SIBs. The SCPE film was produced via a simple solution casting method, incorporating poly(vinylidene fluoride) (PVDF), poly(vinyl pyrrolidone) (PVP), succinonitrile as binders, NaPF6 salt, and NZSP NASICON as a ceramic electrolyte additive. Characterization techniques, including electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray diffraction (XRD), were used to analyze the microstructure and electrochemical properties of the SCPEs. The resulting SCPEs exhibited a total conductivity of 6.8 × 10-4 S/cm at 23°C and 2.5 × 10-3 S/cm at 71°C. SEM analysis revealed uniform dispersion of the ceramic electrolyte within the SPE matrix, attributed to the polar nature of the host polymer, which reduces crystallinity and enhances sodium-ion conductivity. A symmetric half-cell assembly with a sodium electrode demonstrated excellent performance in sodium plating and stripping at a current density of 7 mA cm-2 at 23°C. Further, the thesis explores a machine-driven approach to predict critical factors affecting ss-SIB cathode performance using a dataset of about 350 data points of transition metal layered oxide cathode materials. Machine learning techniques were employed to develop three interconnected models aimed at predicting the P2/O3 ratio, initial discharge capacity, and discharge capacity after 50 cycles. The model for predicting the P2/O3 ratio achieved an R2 value of 83%, indicating high accuracy. The subsequent models, using Gaussian Process (GP) and Multilayer Perceptron Regressor (MLPR), achieved around 80% accuracy in predicting initial discharge capacity and 85% accuracy in discharge capacity after 50 cycles.
Open Access
Development of Fuel Electrodes for Reversible Solid Oxide Fuel Cell Applications
(2017) Addo, Paul; Birss, Viola; Marriott, Robert; Thangadurai, Venkataraman; Shi, Yujun; Pagnier, Thierry
The stability, sulfur tolerance, and electrochemical performance of Ni-YSZ (yttria-stabilized zirconia) composites and single phase La0.3M0.7Fe0.7Cr0.3O3-δ (M = Sr, Ca, (LMFCr)) perovskites, for use as fuel electrodes for reversible solid oxide fuel cell (RSOFC) applications, were investigated in detail. RSOFCs are electrochemical devices that can be operated in both the solid oxide fuel cell (SOFC) and solid oxide electrolysis cell (SOEC) modes. Although Ni-YSZ is the most common fuel electrode for RSOFC applications, it is prone to sulfur poisoning in ppm H2S levels at operating temperatures > 650 oC, thereby decreasing the rate of the hydrogen oxidation/reduction reaction (HOR/HER). It is shown that, at ≤ 650 oC, exposure of Ni-YSZ to ≤ 10 ppm H2S unexpectedly enhanced the HOR activity, while at higher temperatures, conventional Ni poisoning was seen. It was concluded that the activation behaviour at ≤ 650 oC was due to the formation of a catalytic Ni-S species (e.g., Ni3S2) at the triple phase boundary where the HOR/HER occurs. The sulfur tolerance of LCFCr electrodes was also investigated in H2 + low ppm H2S, with LCFCr showing the inverse behavior of Ni/YSZ. At > 700 oC, exposure of LCFCr to ≤ 10 ppm H2S activated the HOR/HER, while deactivation was seen at ≤ 700 oC. It was concluded that exposure of LCFCr to H2S at higher temperatures led to an increase in the density of surface FeO2 terminated species, the proposed active site for the HOR/HER. The LSFCr materials were also shown, for the first time, to be very active (comparable or better than other oxide materials (e.g., La1-xSrxCr1-yMnyO3-δ)) and stable electrocatalysts in CO/CO2 gas environments in both the SOFC and SOEC reaction directions at 600-800 oC. LSFCr was shown to be structurally stable in pure CO2 and 70% CO2:30% CO mixtures at 800 oC, with no major impurities detected. Also, extensive electrochemical characterization, based on both 2-electrode and 3-electrode full and half cell configurations, showed that LSFCr was more active as an electrocatalyst for the reduction of CO2 than for the oxidation of CO. Furthermore, it was found that the surface interaction of CO2 with LSFCr (adsorption, dissociation, electron transfer) was the slowest step in the reaction, relative to oxide ion transport processes.
Open Access
Development of Li-based Garnet Electrolytes for All-Solid-State Li Batteries
(2021-04-26) Palakkathodi Kammampata, Sanoop; Thangadurai, Venkataraman; Marriott, Robert A; Trudel, Simon; Cheng, Yufeng; Kleinke, Holger
All-solid-state Li batteries employing a ceramic solid electrolyte are considered as the nextgeneration energy storage devices due to their advantages in safety and potentially high energydensity. Garnet-type Li6.5La3-xAxZr1.5-xTax+0.5O12 (A = Ca, Sr, Ba; x = 0, 0.1, 0.3, 0.5) solidelectrolytes were prepared by conventional solid-state synthesis and spark plasma synthesis (SPS).The effect of doping of alkaline earth metals and sintering methods on the structural andelectrochemical properties of the solid electrolytes were investigated in this thesis. Powder X-raydiffraction (PXRD) studies have confirmed the cubic garnet-type structure of the solid electrolytes.Microstructure of the solid electrolytes were analysed by scanning electron microscopy (SEM).The samples prepared by SPS process exhibited higher density than the samples prepared byconventional solid-state route. The AC electrochemical impedance spectroscopy (EIS) was usedto measure the impedance of solid electrolytes. All garnet electrolytes prepared in this thesisshowed bulk conductivity in the range of 10-4 S/cm. Among the alkaline earth metal-doped solidelectrolytes, x = 0.1 (Ca and Sr) members prepared by SPS route showed highest conductivity atroom temperature (4.8 x 10-4 S/cm). Li6.5La2.9Sr0.1Zr1.4Ta0.6O12 prepared by SPS process showedan excellent Li-ion charge transfer resistance of 3.5 ? cm2 at 25 °C and the highest critical currentdensity of 0.6 mA/cm2 among all other samples.X-ray photoelectron spectroscopy (XPS) analyses were conducted on SPS-processedLi6.5La3-xAxZr1.5-xTax+0.5O12 (A = Ca, Sr, Ba; x = 0, 0.1) garnet electrolytes to quantify the impuritylayers on garnet surface. XPS analyses revealed that the surface of these electrolytes is covered byLiOH and Li2CO3-based compounds with a thickness of 4?6 nm within 30 minutes as a result ofthe reaction with traces of H2O and CO2 in an Ar-filled glovebox. Chemical compatibility ofLi7La2.75Ca0.25Zr1.75Ta0.25O12 (LLCZT) with commercial cathode materials and liquid Li-ion electrolytes (LLEs) was investigated using PXRD, SEM and EIS analysis. Hybrid cell consistingof Li metal, LLEs, LLCZT and LiNi0.8Co0.15Al0.05O2 or LiNi0.6Mn0.2Co0.2O2 cathode wereassembled in a coin cell and electrochemical performance was evaluated.
Open Access
Development of mixed ion-electron conducting metal oxides for solid oxide fuel cells
(2014-05-14) Kan, Wang Hay; Thangadurai, Venkataraman
A solid oxide fuel cell (SOFC) is an energy conversion device, which directly converts chemical fuels (e.g., H2, CxHy) into electricity and heat with high efficiency up to 90%. The byproduct of CO2 can be safely sequestrated or subsequently chemically transformed back into fuels(e.g., CO, CH4) by electrolysis using renewable energy sources such as solar and wind. The stateof-the-art Ni-YSZ anode is de-activated in the presence of ppm level of H2S and forming coke in hydrocarbons. Currently, mixed ion and electron conductors (MIECs) are considered as alternatives for Ni-YSZ in SOFCs. The key goal of the research was to develop mixed ion-electron conducting metal oxides based on B-site disordered perovskite-type Ba(Ca,Nb)1-xMxO3-δ (M = Mn, Fe, Co), the B-site 1:1 ordered perovskite-type (M = Mn, Fe, Co) and the Sr2PbO4-type Sr2Ce1-xPrxO4 for SOFCs. Ba2(Ca,Nb)2-xMxO6-δ was chemically stable in 30 ppm levels of H2S at 600 °C for 24 h and in pure CO2 at 800 °C for 24 h. The thermal expansion coefficients (TEC) of the as-prepared ordered perovskites was found to be comparable to Zr0.84Y0.16O1.92 (YSZ). The near-surface concentration of Fe2+ in Ba2Ca0.67Fe0.33NbO6-δ was found to be about 3 times higher than that in the bulk sample. The electrochemical performance of Ba2Ca0.67M0.33NbO6-δ was assessed by ac impedance spectroscopy using a YSZ supported half-cell. The area specific polarization resistance (ASR) of all samples was found to decrease with increasing temperature. The ASR for H2 gas oxidation can be correlated to the higher concentration of low valence Fe2+ species near-surface (nano-scale). BaCa0.335M0.165Nb0.5O3-δ crystallizes in the B-site disordered primitive perovskite (space group Pm-3m) at 900 °C in air, which can be converted into the B-site 1:2 ordered perovskite (space group P-3m1) at 1200 °C and the B-site 1:1 ordered double perovskite phase (space groupFm-3m) at 1300 °C. The chemical stability of the perovskites in CO2 and H2 highly depends on the B-site cations ordering. The B-site disordered primitive perovskite phase is more readily reduced in dry and 3% H2O in 10% H2 balanced with 90% N2, and is less stable in CO2 at elevated temperatures, compared to the B-site 1:1 ordered double perovskite phase. The thermal decomposition is highly suppressed in Sr2Ce1−xPrxO4 compounds for Pr > 0, suggesting that Pr improves the thermal stability of the compounds. Rietveld analysis of PXRD and SAED supported that both Pr and Ce ions are located on the 2a site in Pbam. Conductivity increases with Pr content in Sr2Ce1−xPrxO4. The highest total conductivity of 1.24 x 10−1 S cm−1 was observed for Sr2Ce0.2Pr0.8O4 at 663 °C in air.
Open Access
Development of Novel Garnet-Type Solid Electrolytes for Potential Application in Li Ion Batteries
(2012-09-06) Narayanan, Sumaletha; Thangadurai, Venkataraman
The development of promising solid electrolytes having a garnet-like structure has been successfully achieved through solid state (ceramic) method. Various approaches to improve the Li ion conductivity were employed. The first approach involved creating oxide ion vacancies into the crystal structure of parent garnet-like oxide, Li5La3Nb2O12 to create a novel family of compounds with nominal composition, Li5La3Nb2-xYxO12-δ (0 ≤ x ≤ 1). The second approach was Li stuffing into the garnet-like oxides to develop a series of Li stuffed novel Li5+2xLa3Nb2-xYxO12 (0.05 ≤ x ≤ 0.75) and Li6.5La2.5Ba0.5ZrTaO12. Powder X-ray diffraction (PXRD), thermo gravimetric analysis (TGA), scanning electron microscopy (SEM), electron probe microanalysis (EPMA) coupled with a wavelength-dispersive spectrometer (WDS), 7Li nuclear magnetic resonance (Li-NMR), and AC impedance spectroscopy were employed to characterize the structure, morphology, elemental composition, Li ion sites, and Li ion conductivity. Studies have shown that Li5+2xLa3Nb2-xYxO12 have turned out to be promising solid electrolytes with high Li ion conductivity (10-4 Scm-1 at ambient temperatures). In addition, all families of garnets are found to be chemically stable with Li cathode materials (Li2MMn3O8, where M = Fe, Co) up to 400 oC in air. The developed electrolyte materials have the potential to be used in all-solid-state Li ion batteries.
Open Access
Development of Oxygen Electrodes for Reversible Solid Oxide Fuel Cells
(2017) Molero Sánchez, Beatriz; Birss, Viola; Trudel, Simon; Thangadurai, Venkataraman; Ponnurangam, Sathish; Barnett, Scott
The primary focus of this thesis has been to develop high performance stable oxygen electrodes, with a primary emphasis on a mixed conducting La0.3Ca0.7Cr0.3Fe0.7O3-δ (LCFCr) perovskite, for use in advanced reversible solid oxide fuel cells (RSOFCs). RSOFCs are single unit electrochemical devices that can operate in both the fuel cell (SOFC) and electrolysis (SOEC) mode, thus acting as flexible and efficient energy conversion systems. The interest in LCFCr arose from earlier work with LSFCr (La0.3Sr0.7Cr0.3Fe0.7O3-δ), shown to be a very promising SOFC cathode. Thus, this thesis began with a rigorous study of the oxygen evolution (OER) and reduction (ORR) reactions at the LSFCr material, including understanding how to interpret the electrochemical results. However, LSFCr has a thermal expansion coefficient (TEC) that does not match with common solid electrolytes and thus its long time stability is questionable. For this reason, the Ca analogue (LCFCr), a new electrode material, was synthesized and shown to have a much more suitable TEC. Extensive 2-electrode and 3-electrode half-cell studies revealed two slow steps during the OER and ORR, including oxygen/LCFCr surface reactions and O2- transfer at the LCFCr/electrolyte interface. It was also shown that LCFCr is more active in the electrolysis mode (OER) than in the SOFC mode (ORR). Further, the infiltration of ceria or co-infiltration of ceria+LCFCr led to substantial improvements in LCFCr performance, also providing further insights into the processes that control the reaction rates. It was shown that, after 200 h of operation in either the SOFC or SOEC modes, the main source of degradation was from the series resistance (the LCFCr/Au current collector interface), suggestive of Au sintering. The low frequency process, related to the LCFCr/air interface, also deteriorated somewhat, while the underlying LCFCr/electrolyte interface remained stable. This was confirmed from both electrochemistry and high-resolution TEM, showing the retention of a very high quality interface at the atomic level. A novel and very promising SOC powder and cell sintering methodology was also developed using microwave technology, significantly lowering the manufacturing temperature, processing, and energy requirements, due also to the much lower energy demand of the MW furnace. This translates to significant manufacturing cost savings, making MW processing of complete solid oxide cells a promising route for the future.
Open Access
Development of Physics-Based Models of Lithium-ion Battery Energy Storage for Power System Techno-Economic Studies
(2023-09-21) Vykhodtsev, Anton; Rosehart, William D.; Zareipour, Hamidreza; Thangadurai, Venkataraman; Westwick, David T.; Nielsen, Jorgen S.; Liang, Hao
The pathway to achieving a sustainable, low-carbon power system includes the widespread integration of energy storage to tackle intermittency of renewable energy sources and provide stability to the grid through various grid services. Among the wide range of stationary energy storage technologies available, the lithium-ion battery dominates the growth in installations throughout the world. Although lithium-ion battery energy storage systems are complex grid assets with nonlinear characteristics and lifespans that depend on operating conditions, the majority of economic assessments are conducted using a simple energy reservoir model that does not consider the physical processes occurring inside the lithium-ion battery storage. This thesis focuses on the development of physics-based models for lithium-ion battery energy storage in power system techno-economic studies. The aim of this work is to assist developers and investors in making better-informed decisions. In this work, modelling approaches used to represent lithium-ion battery energy storage in power system operation and planning studies are reviewed. The role of advanced models in enhancing the accuracy of economic evaluations and producing feasible schedules for battery storage providing transmission-level services is discussed. More importantly, this work proposes three physics-based mixed-integer models for battery energy storage for use in power system operation research studies. The first model is based on the single particle model and replicates the nonlinear operational characteristics of the battery. This model can be used for short-term operation studies. The second proposed model combines the widely-used energy reservoir model with the physical description of solid electrolyte interphase formation as a degradation mechanism. This model has been tested for long-term studies in both energy and power grid applications. Finally, the third proposed model is a data-driven model that accurately reproduces the degradation processes and nonlinear performance of the lithium-ion cell. The model facilitates long-term assessment of battery energy storage and effectively tracks both capacity and power fade over time. The results obtained from all the models are validated using the digital twin, which is based on the single particle model.
Open Access
Development of Poly (vinylidene fluoride) and Poly(vinyl pyrrolidone) based Solid Polymer Electrolyte for the Next Generation of Solid-state Sodium ion Battery
(2023-01-05) Bristi, Afshana Afroj; Thangadurai, Venkataraman; Shi, Yujun; Heyne, Belinda
Solid-state sodium-ion batteries (ss-SIBs) are a promising alternative to commercially available lithium-ion batteries for next-generation energy storage applications due to the abundance and cost-effectiveness of sodium over lithium. Good electrochemical, mechanical, electrode compatibility, interfacial, and thermal stability properties of the solid form of electrolytes are considered as prerequisites to develop ss-SIBs. Among the organic and inorganic solid electrolytes, solid polymer electrolytes (SPE) are being considered as the promising ones based on the versatility of polymer materials and their potential optimization scope. However, low ionic conductivity and high interfacial resistance are the key drawbacks of typical SPEs. In this thesis, using a facile solution casting fabrication process, a high sodium-ion conductive, filler-less composite solid polymer electrolyte (SPE) film based on poly (vinylidene fluoride) polymer, poly (vinyl pyrrolidone) (PVP) binder, and NaPF6 salt has been studied for ss-SIB. A systematic characterization was carried out to investigate the microstructure and electrochemical properties of PVDF and PVP based SPEs via electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), thermogravimetric analysis (TGA), and Raman spectroscopy techniques. Total conductivities of 8.51 × 10–4 and 8.36 × 10–3 S cm–1 at 23 and 83 °C, respectively, were observed from the developed SPE. Obtained low activation energy (Ea) value suggests that in the composite polymer matrix Na-ion can easily be diffused. Identified β- and γ-phases of the PVDF polymer in the composite SPE matrix indicates the polar nature of the host polymer, which is believed to play an important role in decreasing the crystallinity as well as enhancing the Na+ conductivity. A hybrid symmetric half-cell assembly using Na electrode, 1 M NaClO4 in ethylene carbonate (EC) and propylene carbonate (PC) (EC/PC = 1:1 wt. %) and with SPE showed excellent Na plating–stripping performance at 10 mA cm–2 at 23 °C. A hybrid full cell with a SPE, a Na anode, and a Na3V2(PO4)3 cathode were assembled in a coin cell and electrochemical performance was evaluated.
Open Access
Dielectric characteristics of fast Li ion conducting garnet-type Li5+2xLa3Nb2 xYxO12 (x = 0.25, 0.5 and 0.75)
(Royal Society of Chemistry, 2016) Narayanan, Sumaletha; Baral, Ashok Kumar; Thangadurai, Venkataraman
Here, we report the dielectric characteristics of Li-stuffed garnet-type Li5+2xLa3Nb2−xYxO12 (x = 0.25, 0.5 and 0.75) in the temperature range about −53 to 50 °C using AC impedance spectroscopy. All the investigated Li-stuffed garnet compounds were prepared, under the same condition, using conventional solid-state reaction at elevated temperature in air. The Nyquist plots show mainly bulk contribution to the total Li+ ion conductivity for Li5.5La3Nb1.75Y0.25O12 (Li5.5–Nb) and Li6La3Nb1.5Y0.5O12 (Li6–Nb), while both bulk and grain-boundary effects are visible in the case of Li6.5La3Nb1.25Y0.75O12 (Li6.5–Nb) phase at ∼−22 °C. Non-Debye relaxation process was observed in the modulus AC impedance plots. The dielectric loss tangent of Li5+2xLa3Nb2−xYxO12 are compared with that of the corresponding Ta analogue, Li5+2xLa3Ta2−xYxO12 and showed a decrease in peak intensity for the Nb-based garnet samples which may be attributed to a slight increase in their Li+ ion conductivity. The relative dielectric constant values were also found to be higher for the Ta member (>60 for Li5+2xLa3Ta2−xYxO12) than that of the corresponding Nb analogue (∼50 for Li5+2xLa3Nb2−xYxO12) at below room temperature. A long-range order Li+ ion migration pathway with relaxation time (τ0) 10−18–10−15 s and an activation energy of 0.59–0.40 eV was observed for the investigated Li5+2xLa3Nb2−xYxO12 garnets and is comparable to that of the corresponding Ta-based Li5+2xLa3Ta2−xYxO12 garnets.
Open Access
Dopant Concentration - Porosity - Li-ion Conductivity Relationship in Garnet-Type Li5+2xLa3Ta2-xYxO12 (0.05 ≤ x ≤ 0.75) and Their Stability in Water and 1M LiCl
(American Chemical Society, 2015) Narayanan, Sumaletha; Ramezanipour, Farshid; Thangadurai, Venkataraman
Open Access
Effect of Excess Li on the Structural and Electrical Properties of Garnet-Type Li6La3Ta1.5Y0.5O12
(Electrochemical Society, 2015) Narayanan, Sumaletha; Hitz, Gregory T.; Wachsman, Eric D.; Thangadurai, Venkataraman
Volatility of lithium during preparation of lithium-stuffed garnet-type metal oxide solid Li ion electrolytes is a common problem, which affects phase formation, ionic conductivity, mechanical strength and density. Synthesis of Li-stuffed garnets has been performed generally using the conventional solid-state reactions at elevated temperature in air. The present study describes the effect of excess LiNO3 (2.5 to 15 wt.%) addition during the ceramic synthesis on the structural and electrical properties of garnet-type Li6La3Ta1.5Y0.5O12. Powder X-ray diffraction (PXRD) confirmed that cubic phase was formed in all tested cases, and there is no significant variation in lattice parameter with amount of excess LiNO3 used. However, increasing amounts of excess lithium decreased inter-particle contact and increased grain growth during sintering, producing sharply varied microstructures. PXRD showed no secondary phase and scanning electron microscopy (SEM) analysis showed rather uniform morphology and absence of "glassy" materials at the grain-boundaries. The bulk Li ion conductivity was found to increase with amount of excess lithium, reaching a maximum room temperature conductivity of 1.62 × 10−4 Scm−1 for the sample prepared using 10 wt.% excess LiNO3. Raman microscopy study indicated the presence of Li2CO3 in all aged Li6La3Ta1.5Y0.5O12 samples prepared using excess LiNO3.