Scale-up of Metal-Supported Solid Oxide Fuel Cells

Metal-supported solid oxide fuel cells (mSOFC) display a number of advantages over conventional all-ceramic SOFCs, including low-cost structural materials (e.g. stainless steel), mechanical ruggedness, excellent tolerance to redox cycling, and extremely fast start-up capability. Challenges for mSOFCs include: oxidation of the metal support, especially at 800°C and above; the possibility of the stainless steel exacerbating Cr poisoning of the cathode catalyst; fabrication and materials set restrictions arising from the requirement that stainless steel be sintered in reducing atmosphere; and, only moderate performance and lifetime have been demonstrated to date. These advantages and challenges suggest that mSOFCs may be well-suited for portable, ruggedized, fast-start, intermittent-fuel, or other unique and innovative applications. Nissan has developed the world’s first light-duty vehicle with a conventional SOFC stack for traction power, fueled by bio-ethanol reformate. Because of the desire for rapid-start capability, developing mSOFC cell and stack technology for this vehicular application is a priority. The small volume allowance for the SOFC stack on-board a small vehicle furthermore demands high power density from the mSOFC. In this work, we seek to maximize mSOFC power density. This work is an extension of our previous efforts focusing on co-sintered, YSZ-based mSOFCs with porous metal supports on both anode and cathode sides, with catalysts deposited into both electrodes via infiltration. These features provide for a mechanically rugged cell that can be processed with low-cost scalable techniques, and high surface-area catalysts that provide excellent performance by avoiding interdiffusion or coarsening during cell sintering. To support the vehicular traction application, in this work we further develop catalyst infiltration processing for mSOFCs to dramatically increase power density. The goal is to increase cell performance by improving infiltration of conventional catalyst compositions (lanthanum strontium manganite (LSM), Ni, doped ceria) into electrode backbones of conventional yttria-stabilized zirconia (YSZ). Various aspects of the infiltration procedure were optimized, including: precursor composition and dilution with water; catalyst loading; and, crystallization temperature. Figure 1 shows the resulting high performance. Peak power of 1.1 and 1.9 W/cm2 is achieved at 700°C and 800°C, respectively, and the 800°C performance is the highest reported for mSOFCs to date. Cell stability in the operating temperature range 600 to 750°C will also be presented. Acknowledgements Funding for this work was provided by Nissan Motor Co., Ltd. This work was funded in part by the U.S. Department of Energy under contract no. DE-AC02-05CH11231. Figure 1

In this context of energy transition, the use of renewable energies through the conversion of different resources with promising technologies into storable energy carriers is of eminent importance for a sustainable energy supply. Hydrogen production from steam using solid oxide electrolysis cells (SOEC) is part of this so called “energy mix”. Recently, promising progress appeared from the investigation of metal supports in the solid oxide cell architecture. Metal-supported solid oxide fuel cells (MS-SOFCs) show not only good mechanical strength, relatively low operating temperature (500-750 °C) and improved sealing capability but also low materials cost and tolerance towards rapid thermal cycling and redox cycling [1-3]. In the present study, a MS-SOFC was tested under electrolysis conditions. The cell consisted of Ni-catalyst-loaded La0.1Sr0.9TiO3-α/gadolinium-doped ceria (Ni-LST/GDC) as fuel electrode, gadolinium-doped ceria/yttrium-stabilized zirconia (GDC/YSZ) as electrolyte and La0.6Sr0.4Co0.2Fe0.8O3-δ (LSCF) as O2 electrode. After a short testing period in fuel cell mode, a first evaluation of the cell performance profile in electrolysis mode was performed. Thus, a series of current-voltage curves as well as impedance diagrams (under OCV and under load) was recorded for different fuel electrode gas compositions. Furthermore, degradation under electrolysis operation was also investigated based on the evolution of the cell voltage against time for several currents applied. Consequently, analysis of the post-mortem characterization by SEM/EDX, along with the electrochemical testing results, aims at identifying the changes in cell characteristics specifically related to degradation under electrolysis operating conditions. [1] M. C. Tucker, J. Power Sources 195 (2010) 4570-4582. [2] J. T.S. Irvine, J. Bae, J-Y Park, W. S. Choi, J. H. Kim, Int. J. Hydrogen Energy, In Press-Corrected Proof. [3] A. M. Dayaghi, K. J. Kim, S. Kim, J. Park, S. J. Kim, B. H. Park, G. M. Choi, J. Power Sources 324 (2016) 288-293.

Durability of symmetric-structured metal-supported solid oxide fuel cells

Know when to fold ‘em: An empirical description of risk management in public research funding

The majority of published R&D in supercapacitors relies on testing at a small coin or Swagelok cell size. This is often due to a lack of availability of equipment and knowledge required to move to a larger scale. Whilst comparisons between materials and other components can be made at the small cell level, the actual performance in larger devices does not necessarily follow to the same extent. In many cases, a scaling factor can be applied to the values of energy and power density for an active material to give the corresponding values in large devices but this is not always the case. For the extrapolation of performance from small to large cell to be valid, many factors must be considered and matched to real devices such as electrode thickness, relative electrolyte amount, current collector properties and separator type. Whilst allowing an estimate of large device properties in this way from small cell level is useful, this approach does not consider many of the problems encountered when scaling up that also differ between cell geometries (cylindrical, pouch or prismatic) can result in predicted performances never being achieved. In the current work, the development from coin cell to >800 F A5 sized pouch cell (the same geometric area as the batteries of the Nissan Leaf) is reported using commercially available activated carbon (YP50-F, Kuraray, Japan) as the active material and TEABF4in acetonitrile electrolyte, with comparisons made throughout between the small and large scale. The scale-up of mixing of electrode ink is demonstrated from the 50 g to 10 Kg scale, with discussion of the effects of various components on the solid content achievable at the viscosities required for coating. Various parameters in electrode production are discussed in relation to their effects on cell performance at the coin and large pouch level including electrode thickness/loading and drying temperature profiles, the later of which being surprisingly shown to be responsible for delamination of electrode from current collectors and complete failure in large cells over time (not observed in coin cells). The effect of calendaring of electrodes at different temperatures is shown to produce a range of electrode densities, with the effect on adhesion, specific capacitance and ESR investigated in cell. It is shown that whilst electrode capacitance is, to a broad degree, unaffected by calendering, much benefit can be gained in terms of ESR and adhesion but that over-calendering has a major detrimental effect. The production of A5 sized pouch cells from the electrodes produced is illustrated, with early cell testing results used to highlight the problems faced in supercapacitor pouch cells resulting from early capacitance fade, gas production and a lack of compression. These problems are addressed through the application of external compression (as is provided in module assemblies and by the spring in coin cells) and through the float ageing of cells to a stable capacitance and subsequent gas removal, with the differences in time and energy required at coin and pouch cell level to achieve this highlighted. In conclusion, the effects and contributions of electrode thickness, number of electrodes, electrolyte mass and “parasitic” components such as packaging in pouch cells are considered in terms of both volumetric and gravimetric energy and power densities, contrasting the real device values obtained in scale-up with those of the active materials often reported and those predicted from coin cell results. Figure 1

The experimental verification of a Lithium-ion battery for automotive life requirements utilizes significant laboratory resources and calendar time. If the amount of life testing required to validate a cell design for automotive applications can be reduced, new cell designs could be confidently implemented at lower cost and in shorter time. High precision coulometry (HPC) has recently emerged as a promising candidate for shortening the time required for validating cell life. Literature examples have demonstrated improved identification of the mechanisms causing capacity fade1 and qualitative sorting of higher performing cells2. Academic groups have pioneered this approach but have been primarily limited to testing low currents that are used to probe the rates of side reactions in calendar life scenarios. Our research focus has been the design, development and validation of a 200 A, high precision (<50 ppm current and <25 ppm voltage) battery tester in partnership with Arbin Instruments and Sandia National Laboratory, with the support of the US Department of Energy (DOE) Advanced Research Projects Agency- Energy (ARPA-E)3. The capability to perform high precision measurements at currents up to 200 A means the additional degradation brought about by high-rate cycling can be evaluated in addition to calendar assessments. Additionally, we aim to quantitatively assess performance degradation trends by linking presently measured values to future performance. Validation testing is presented using 5 Ah prismatic cells to quantify the reduction in test time that is practically achievable using high precision measurements. Continuous cycle aging using multiple current profiles and ambient temperatures is conducted with periodic reference performance tests. The mathematical relations between capacity, resistance, coulombic efficiency, and electrode endpoint slippage are leveraged to define various life prediction methods. The reference performance test measurements from both the high precision tester and standard commercial reference tester are entered as inputs into the life prediction models. Improved measurement precision can result in reduced uncertainty bands when extrapolating life metric trends into the latter stages of cell life. Enhanced measurement precision can also enable the quantification of long term trends at earlier stages of testing.

This paper describes concepts to minimize the plume generated by unwanted sediments collected along with manganese nodules during hydraulic mining operations. The concept consists of two novel technologies: separating all sediment from the collected nodule slurry to eliminate sediment from entering the riser and lift system, thereby reducing, or eliminating a midwater plume, and subsea electrocoagulation (EC) to create rapidly settling flocs of sediment being discharged from the seafloor collector. The first approach involves designing a gravity separator (hopper) whereby the larger particles fall through an outlet and are entrained with clean water before entering the riser, while all the sediment and water collected with the nodules exits at the hopper overflow. To prevent sediment from being entrained with the nodules, a "reverse hydrocyclone" and secondary hopper is incorporated in the underflow circuit to help maintain a positive pressure differential between the riser inlet and the hopper during operations. The second approach employs the marinization of proven wastewater treatment EC technology to create large metalliferous flocs which attract the sediment causing rapid settling when the slurry is discharged aft of the collector. Work reported here includes numerical (CFD) confirmation of the separator performance, and experimental demonstration of the EC application, as well as techno-economic assessments of the cost impacts of implementing these technologies. This work was supported by the U.S. Department of Energy, Advanced Research Projects Agency – Energy (ARPA-E), and with contributions of sediment for the EC tests by The Metals Company from the Clarion Clipperton Zone and Ocean Minerals, LLC from the Cook Islands EEZ.

Distributed Energy Resources (DER) have increased penetration into the electric grid in recent years due to the growth of many renewable energy technologies as well as more efficient small conventional generation sources. Microgrids have grown in popularity along with the increased usage of DERs as a way to manage the multiple DERs on a local level.1Microgrids contain energy storage devices to store and distribute the intermittent energy provided by DERs (see figure 1).Coupling a solar energy resource with a Li-ion battery energy storage, we study the autonomy (the percentage of time the system meets demand) and utilization (amount of capacity used) during yearly operation.2By including a demand schedule with the coupled solar and battery system, we study both how different demands, system sizes and solar insolation patterns will affect the autonomy and utilization of the system. Both islanded and grid-tied demand structures will be discussed.The battery model involved in this study is an electrochemical and transport based Li-ion battery model.3For the solar portion of the model we will assess both ideal insolation curves as well as site based insolation data. For the real-site data, several solar monitoring sites within the US will be employed. The real data will offer a contrasting look at how much the coupled system can be affected on a daily and seasonal basis. In addition, using real data will allow for a greater assessment about the stability of a coupled system in areas with strong insolation, but high variability against areas of weaker insolation, but low variability. A balance between a high level of both autonomy and utilization will be studied in conjunction with preferable demand structures. This balance will affect the structure and operation of a microgrid with both solar and battery systems. Acknowledgements The authors acknowledge financial support from the U.S. Department of Energy’s Advanced Research Projects Agency- Energy (ARPA-E), and the Solar Energy Research Institute in India and the United States (SERIIUS), as well as, Washington University in St. Louis’ McDonnell Academy Global Energy and Environmental Partnership (MAGEEP).

Battery Management Systems (BMS) are critical to safe and efficient operation of lithium-ion batteries and accurate prediction of the internal states [1]. Smarter BMS that can estimate and implement optimal charging profiles in real-time are important for advancement of the Li-ion battery technology. Estimating optimal profiles using physics-based models is computationally expensive because of the non-linear and stiff nature of the model equations, involving the need for constrained non-linear optimization [2-12]. In this work, we present an alternative approach to control batteries applying the concept of differential geometry. This approach is known as Generic Model Control (GMC), or Reference System Synthesis [13,14]. This work enables robust stabilization and control of battery models to set-point as an alternative approach, eliminating the need to perform optimization of nonlinear models. This work builds on our previous work of implementation of GMC for differential variables occurring in a model consisting of differential algebraic equations (DAEs), and extends it to set point based control for algebraic variables. Conventional GMC is applicable for cases in which the output is typically independent of control [13]. We also extend it for cases for which the measured variable can be an explicit function of the manipulated variable. As compared to the generic model control approaches implemented by previous researchers, we have implemented the same concept using direct DAE numerical solvers [15]. The results are presented for single input single objective, and for constrained problems. The proposed approach is compared with standard control approaches and is found to be equally robust if not better. Acknowledgements The work presented herein was funded in part by the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000275 and the Clean Energy Institute at the University of Washington, Seattle.

Liquid electrolyte solutions containing dissolved active material imbue Redox Flow Batteries (RFBs) with many unique benefits relative to solid-state electrochemical energy storage devices: long shelf-life, long system life-time, de-coupled rated energy and power, ease of recyclability.1 Operating a RFB system with flowing electrolyte solutions presents unique concerns as well, with one notable concern arising from possible precipitation of electrolyte. Precipitation of active material can have many consequences including sensor inaccuracy, inaccessible storage capacity, partially- or fully-blocked reactor electrode regions, and system clogging.Aqueous vanadium RFBs, a leading chemistry in commercial systems, has a precipitation mechanism at high temperatures for battery solutions containing commercially relevant vanadium concentrations >1.5 M. At elevated temperatures (> 40°C), positive electrolyte solutions can precipitate V2O5 dimers, first as a gel-like substance and eventually as solid particles.2 The UTRC team has developed recovery procedures for systems that may succumb to such precipitation events; in the case for aqueous vanadium RFBs, exposure of precipitate to lower oxidation state forms of vanadium (i.e. negative electrolyte) reduces and redissolves precipitated V2O5. This electrolyte takeover process (ETP) can successfully redissolve precipitates and recover performance from precipitate-induced cell/stack under-performance.As UTRC pursues alternative flow chemistries, the same ETP principles are applied to other chemistries such as polysulfide-based systems, known for sulfur crossover and precipitation of elemental sulfur in positive electrode volumes.3 This abstract will discuss the progress made at UTRC to recover from precipitation events in such chemistries, which, unlike aqueous vanadium, do not permit simple mixing of negative and positive electrolytes. Acknowledgements: The authors gratefully acknowledge support from Vionx Energy Corporation. Some of the work to be presented here was funded by the Advanced Research Projects Agency - Energy (ARPA-E), U.S. Department of Energy (DOE) under Award Number DE-AR0000994.

Simultaneous Pursuit of Discovery and Invention in the US Department of Energy

Rechargeable lithium-ion batteries have been extensively used in mobile communication and portable instruments due to their high volumetric and gravimetric energy density and low self-discharge rate, leading many scientists and engineers to work towards developing lithium-ion batteries with improved performance and longer life.In normal operation, an active solid-electrolyte-interface (SEI) layer forms in the first cycle of charging, due to reactions of lithium and solvent at the active surface (1,2). The SEI layer provides a barrier between the electrolyte and electrode to prevent further reaction while allowing lithium ions to permeate through the SEI layer in order to intercalate into and out of the bulk solid to store and release energy. However, the SEI layer continues to grow under repeated cycling. This growth increases the diffusion resistance of the lithium ions to the bulk active material, and removes cyclable lithium from the system, reducing the efficiency of the battery (1,2). This increased resistance can produce high temperature and can result in thermal runaway (3-5) within the battery. The properties and chemical composition of the SEI layer (active and passive) has been a subject of intense research due to its importance in the safety, capacity fade, and cycle life of Li-ion secondary batteries (6-12). Examination of the growth of the SEI layer as a mechanism for capacity fade has been performed using Kinetic Monte Carlo (KMC) simulations (13). This has provided valuable insight into the growth of the SEI layer and has shown the effects of high rates of charging on SEI layer passivation. These KMC simulations can be used to study the surface heterogeneity of the electrode surface as the passive layer is formed.The KMC model used will be expanded to a 2+1D model which tracks the thickness of the SEI layer over a representative surface of the solid particle. This will give a sense of the heterogeneity that arises in the SEI layer and will be coupled with the pseudo 2D model to simulate full battery operation. The P2D model will be converted from a system of partial differential equations to a system of ordinary differential equations by using reformulation techniques developed for the continuum model (14). The KMC model studies the events that occur in the SEI layer and the particle surface. For example, diffusion of the solvent in the SEI layer is modeled using the KMC approach. The reactions at the active material surface are modeled by considering the relative rate constants and using a random number generator to determine the event which occurs. In contrast, the continuum P2D model explains what happens in the bulk phases, and is deterministic. This coupled model will perform continuum calculations simultaneously with the KMC calculations. As passivation is considered in the KMC model, the capacity of the battery will fade with time, allowing for life time studies to be performed. This will lead to better understanding of the conditions which lead to capacity fade and better operation of lithium-ion batteries. Acknowledgements The authors acknowledge financial support by the National Science Foundation under grant numbers CBET-0828002, CBET-0828123, and CBET-1008692, and the Advanced Research Projects Agency – Energy (ARPA-E), U.S. Department of Energy, under Award Number DE-AR0000275.

Large fixed and floating wind farms are planned in the US, the first of which will come on stream along the East Coast, and then possibly followed by the West Coast in deepwater. However, there are other regions in North and South America, and even the Caribbean that are rapidly aiming for offshore wind farms. One of those locations, offshore Texas, may develop ahead of the West Coast by taking advantage of the unparalleled expertise in ocean engineering in Texas gained through over 40 years of offshore oil and gas developments. In addition, Texas has regional competitive advantages that could result in another offshore boom for the region. Texas is the leading state for onshore wind power and consequently has some highly innovative research institutions and initiatives that could further push Texas to the forefront of regional, if not global, offshore wind technology development and deployment. The additional advantages that Texas can provide to wind farm developers based on its proximity to the Caribbean and South American offshore wind markets are also presented. As an example of innovation in Texas, the University of Texas at Dallas, DOE ARPA-E (Department of Energy Advanced Research Projects Agency – Energy) funded vertical axis wind turbine (VAWT) development is summarized (ARPA-E, 2020). While elements of VAWT technology are transferable to horizontal axis wind turbine (HAWT) technology to improve HAWT performance, more generally, the deployment of VAWTs overcomes many logistical and performance problems inherent in deploying HAWTs offshore. Such VAWT advantages are discussed. Two cases are presented comparing HAWT versus VAWT floating wind farms. The technology and execution differences of the two cases are compared and the net present value and internal rate of return are calculated conserving the technology differences. Discussion of forthcoming additional financing opportunities is also presented to illustrate how even in low-cost electric rate markets, offshore wind can still be feasible.

The Advanced Research Projects Agency-Energy (ARPA-E) launched the Reliable Electricity Based on ELectrochemical Systems (REBELS) program in 2014 to pursue alternate fuel cell materials and operating conditions that could enable system cost reductions and new electrochemical functionality. The program objective of a current density of 200 mA/cm2 at 0.78 V and 500oC on methane fuel in a button cell was achieved. Several teams demonstrated thousands of hours of operation on internally-reformed methane fuel at 500oC without coking, both with and without a significant steam co-feed. Fuel cells with charge storage functionality in or near the anode showed an improved response to variations in current density, with a lower voltage decrease at higher fuel utilization. Progress was also made on using fuel cells to convert methane to liquid fuels. Further research is needed to evaluate whether stacks in this temperature range possess the appropriate combination of performance and cost to accelerate the commercialization of high efficiency fuel cells.

The incorporation of physics-based lithium-ion battery models in real-time optimization, control and estimation has the potential to substantially facilitate their efficient and safe operation.1,2 In addition to improved prediction of battery states, the access to predictions of variables internal to battery electrochemistry allows the formulation of more complete optimization and control problems than would be possible by simple circuit models.3 Various approaches have been employed to enable this integration by reducing the computational demands of electrochemical models, particularly for the macro-homogeneous ‘P2D’ models of Newman and co-workers.4 These may be broadly divided into two categories: simplifications of the full model subject to limiting assumptions,5–7 or reformulation techniques which exploit the underlying structure of model equations to achieve fast simulation.1,8,9 The single particle model (SPM) visualizes the electrodes in a lithium-ion battery as two spherical particles and considers the electrode reactions and lithium transport through the active particle. Importantly however, it neglects potential and concentration variations in the electrolyte phase, which limits its predictive ability to low-current scenarios. Reformulated P2D models offer the desired computational performance without sacrificing physical detail, but their utility is dependent on the precise estimation of a large number of parameters from experimental data.10 This talk focuses on the development of a lumped physics-based model for lithium-ion batteries. The governing equations of the P2D model are integrated over the volume of each region in a cathode-separator-anode representation. This results in a set of volume-averaged quantities and relations, with the temporal evolution of each averaged variable expressed as an overall balance containing internal source terms and interfacial fluxes, which need to be approximated. The averaged porous domains may thus be regarded as three ‘tanks-in-series’. The model equations are simulated, and the electrochemical variable predictions compared against both the full P2D model and SPM over a range of parameter combinations and operating conditions. Various approximations for the interfacial fluxes are also evaluated in terms of their impact on cell-level predictions. The model is also extended to incorporate thermal effects via volume-averaged energy balances. Model predictions for different galvanostatic discharge rates suggest that the lumped model is of intermediate sophistication between the SPM and the P2D models. This is most likely because it incorporates liquid phase transport in an average sense, in contrast to SPM, which ignores them entirely. The lumped model is conservative, and possesses the computational simplicity of SPM, while also incorporating elements from the P2D model, but with a smaller number of parameters, making it easier to parameterize and potentially facilitating use in real-time prediction and control. In addition, tank models have been extensively researched in control theory, enabling the extension of these concepts to battery systems through lumped models. The ‘tanks-in-series’ averaging procedure described herein may be generalized to any electrochemical battery model. Acknowledgements The authors are also thankful for financial support from the Battery500 Consortium and the Advanced Research Projects Agency (ARPA-E). The authors acknowledge financial support from the Department of Chemical Engineering and the Clean Energy Institute at the University of Washington. References A. M. Bizeray, S. Zhao, S. R. Duncan, and D. A. Howey, J. Power Sources, 296, 400 (2015).V. Ramadesigan, P. W. C. Northrop, S. De, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 159, R31 (2012).M. Pathak, D. Sonawane, S. Santhanagopalan, R. D. Braatz, and V. R. Subramanian, ECS Trans., 75, 51 (2017).M. Doyle, T. J. Fuller, and J. Newman, J. Electrochem. Soc., 140, 1526 (1993).S. Santhanagopalan and R. E. White, J. Power Sources, 161, 1346 (2006).B. S. Haran, B. N. Popov, and R. E. White, J. Power Sources, 75, 56 (1998).M. Guo, G. Sikha, and R. E. White, J. Electrochem. Soc., 158, A122 (2011).P. W. C. Northrop, V. Ramadesigan, S. De, and V. R. Subramanian, J. Electrochem. Soc., 158, A1461 (2011).P. W. C. Northrop, M. Pathak, D. Rife, S. De, S. Santhanagopalan, and V. R. Subramanian, J. Electrochem. Soc., 162, A940 (2015).V. Ramadesigan, K. Chen, N. A. Burns, V. Boovaragavan, R. D. Braatz, and V. R. Subramanian, J. Electrochem. Soc., 158, A1048 (2011).