Stationary Applications Research Articles

Energy harnessing and storage from surface switching with a ferroelectric electrolyte.

In the quest for innovative energy solutions suitable for mobile, stationary and digital applications, ferroelectric topological insulators (FETIs)1 emerge as promising candidates. These materials combine topologically protected states with spontaneous and switchable polarization. This study reveals emergent phenomena in FETI-electrolytes through experiments and simulations, specifically in the A3-2xBaxClO family (where A = Li, Na or K, and x = 0 or 0.005). Here, it is shown that surface oscillations of the potential (V), temperature, and mass may synchronize with the bulk's oscillations, and be harnessed and stored in the form of electrical energy either in a sole FETI or in a battery-type cell presenting a panoply of applications from wireless batteries to transistors, memories, sensors, and selective catalysts.

Nanoconfinement-induced Calcium ion Redox Charge Storage of V2CTx MXene

Rechargeable calcium metal batteries are promising for sustainable stationary energy storage applications but are plagued by the irreversible nature of Ca metal anodes due to the formation of non-ionically conductive...

NMR contributions to the study of water transfer in proton exchange membranes for fuel cells

As programs to support efficient and sustainable energy sources are expanding, research into the potential applications of the hydrogen vector is accelerating. Proton exchange membrane fuel cells are electrochemical converters that transform the chemical energy of hydrogen into electrical energy. These devices are used today for low- and medium-power stationary applications and for mobility, in trains, cars, bicycles, etc. Proton exchange membrane fuel cells use a polymer membrane as the electrolyte. The role of the membrane is multiple: it must separate gases, be an electronic insulator and a very good ionic conductor. In addition, it must resist free-radical chemical attack and have good mechanical strength. Nafion-type perfluorinated membranes have all these properties: the fluorinated backbone is naturally hydrophobic, but the hydrophilic ionic groups give the material excellent water sorption properties. The water adsorbed in the structure is extremely mobile, acting as a transport medium for the protons generated at the anode. Although it has been studied for a long time and has been the subject of a large number of papers perfluorinated membranes are still the reference membranes today. This article reviews some contributions of Nuclear Magnetic Resonance methods in liquid state to the study of water properties in the structure of Nafion-type perfluorinated membranes.

High-performance Na-ion full-cells with P2-type Na0.67Mn0.5-xNixFe0.43Al0.07O2 cathodes: Cost analysis for stationary battery storage systems

Na-ion batteries are viable alternatives to Li-ion batteries especially for stationary applications. Developing suitable electrode materials, half-cell and full-cell studies and cost analysis are major steps and challenges for their commercialization. In this study, we report the synthesis of a promising cathode material, Na0.67Mn0.5-xNixFe0.43Al0.07O2 (x = 0.02–0.10 with Δx = 0.02), using a modified solid-state synthesis technique. The materials were heated at high temperature for 6 h in air and quenched in liquid N2. We determined the solubility limit of Ni in Na0.67Mn0.5Fe0.43Al0.07O2 as x ≤ 0.06. The interlayer separation increases with increasing Ni content due to the ionic radii difference between Mn and Ni. X-ray photoelectron spectroscopy (XPS) measurements evidence the valance state of Ni in the x = 0.06 sample as 2+ and 3+.Cyclic voltammetry (CV) analysis of the half-cells were performed at 10 °C, room temperature, and 50 °C to observe the effect of environmental temperature on redox mechanism. The highest half-cell capacity of the cells was determined as 181 mAh/g for x = 0.06 at C/3-rate. Artificial solid electrolyte interface (SEI) formation was performed on the hard carbon anode by presodiation technique and the full-cells of Na0.67Mn0.44Ni0.06Fe0.43Al0.07O2/hard carbon were assembled in CR2032 coin cells. The capacity values of the cells at C/2, C, and 2C-rate were determined as 131.4 mAh/g, 116 mAh/g and 100.8 mAh/g for the 1 cycle and 33 mAh/g, 40.6 mAh/g and 49.9 mAh/g for the 500th cycle, respectively. The cost analysis for the commercial package for stationary energy storage system was performed by BatPac program and results are discussed.

Aging Aware Battery Operation and State of Health Evaluation in Energy Storage Systems

The sources of performance loss in lithium-ion batteries are many and can vary widely dependent on battery usage [1]. Understanding these mechanisms and coupling usage patterns to dominating degradation phenomena can allow smarter use and longer lifetime of the batteries. This can especially bring value in stationary applications, as the usage patterns have different characteristics and second life applications for batteries are considered as well [2].Driven by the development of battery electric vehicles, batteries with higher power and energy densities have revolutionized the market. The lifetime of the batteries is another crucial criterion. A significant amount of work has been performed studying the degradation phenomena and evaluating stress factors. High/low potentials, high C-rates, and temperature deviations from room temperature should be avoided to keep the degradation rate low [3-5]. The power demand for batteries in stationary energy storage systems is lower than vehicle applications and some of these extremes could therefore be avoided [6]. Finding optimal sizing of the batteries, with high energy throughput and low degradation rate, is therefore of interest. The energy delivered by the storage system is further part of the power trading market, hence motivating the need to accurately correlate delivered energy and battery performance loss from different services.In this work the degradation of commercial 18650-type Nickel Cobalt Manganese (NCM)/Graphite cells, in stationary applications is studied. Different scenarios including type of service, sizing, and second-life applications are studied through accelerated testing. The work expands upon a previous study focusing on the degradation effects of combining services [7]. The degradation analysis involves different techniques such as the capacity evolution (Figure 1), electrochemical impedance spectroscopy (EIS), as well as changes in the electrodes revealed by differential voltage analysis (DVA). The electrode balancing, capacity and cell polarization is evaluated in terms of battery state-of-health and important characteristics highlighted. Preliminary results show no additional degradation introduced by scaling the current amplitude 50%. A clear relationship between state-of-charge window and degradation rate is shown, where the graphite two-phase regions are of importance. These regions are also affected by the electrode slippage observed in the DVA. Strategies for battery characterization and operation strategies for second-life applications will be further investigated.Figure 1. Preliminary results of the normalized capacity development of the cells in the study, as an averaged value of duplicate cells. Frequency regulation (FR) is a mild cycle around 50% SOC, current maximum 1C. FR_high has a current maximum of 1.5C. Peak shaving (PS) is a 1C constant current cycling between 22-78% SOC, PS_low has a 0.5C constant current cycling. FRPS is the two cycles combined.References Birkl, C. R.; Roberts, M. R.; McTurk, E.; Bruce, P. G.; Howey, D. A., Degradation diagnostics for lithium ion cells. Journal of Power Sources 2017, 341, 373-386. Martinez-Laserna, E.; Gandiaga, I.; Sarasketa-Zabala, E.; Badeda, J.; Stroe, D. I.; Swierczynski, M.; Goikoetxea, A., Battery second life: Hype, hope or reality? A critical review of the state of the art. Renewable and Sustainable Energy Reviews 2018, 93, 701-718. Baure, G.; Dubarry, M., Battery durability and reliability under electric utility grid operations: 20-year forecast under different grid applications. Journal of Energy Storage 2020, 29. Keil, P.; Schuster, S. F.; Wilhelm, J.; Travi, J.; Hauser, A.; Karl, R. C.; Jossen, A., Calendar Aging of Lithium-Ion Batteries. Journal of The Electrochemical Society 2016, 163 (9), A1872-A1880. Ecker, M.; Nieto, N.; Käbitz, S.; Schmalstieg, J.; Blanke, H.; Warnecke, A.; Sauer, D. U., Calendar and cycle life study of Li(NiMnCo)O2-based 18650 lithium-ion batteries. Journal of Power Sources 2014, 248, 839-851. Dubarry, M.; Devie, A.; Stein, K.; Tun, M.; Matsuura, M.; Rocheleau, R., Battery Energy Storage System battery durability and reliability under electric utility grid operations: Analysis of 3 years of real usage. Journal of Power Sources 2017, 338, 65-73. Ohrelius, M.; Berg, M.; Wreland Lindström, R.; Lindbergh, G., Lifetime Limitations in Multi-Service Battery Energy Storage Systems. Energies 2023, 16 (7). Figure 1

Research and Innovation Activities on PEM Fuel Cells and Electrolysers Supported by the Clean Hydrogen Partnership

The Clean Hydrogen Partnership — the successor of the Fuel Cells and Hydrogen Joint Undertaking (FCH JU) — aims to contribute to EU Green Deal and Hydrogen Strategy by providing financial support for research and innovation activities in the field of advanced clean hydrogen technologies. It builds on 15 years of strategic cooperation between public and private sectors enabling several innovative technologies to advance from the experimental scale closer to maturity.The projects funded under the previous FCH JU programmes and the first Call for Proposals 2022 of the Clean Hydrogen Partnership have significantly advanced both the proton-exchange membrane-based fuel cell (PEMFC) and electrolyser (PEMEL) technologies. So far, about 660 million EUR were allocated to support 122 projects addressing different aspects of PEMFC and PEMEL technologies. A large share of this funding, around 585 mil EUR supporting 102 projects, was dedicated to large scale demonstrations of PEMFC in transport and stationary applications. Largely thanks to this support, the EU reached a competitive position to provide PEMFC and PEMEL technologies with a well-established supply chain from processing the raw materials into specialised materials (e.g. electro-catalysts), production of components and sub-systems.Significant advancements have been made in the development, validation and demonstration of PEM fuel cell technologies for material handling vehicles, buses and passenger cars as well as stationary applications. Future research and demonstration projects on PEM fuel cells are needed in transport sector such as heavy-duty vehicles, industrial vehicles, shipping and aviation.The R&I projects on PEM electrolysers have contributed to making hydrogen production more competitive and enabled the scale-up of these technologies alongside improvements in efficiency and cost reduction. Significant progress has been made on PEMEL for example: (i) achieving a rapid response time (in the order of a few seconds) needed in grid balancing, (ii) upscale the PEM electrolysers to a multi-MW level and (iii) providing reliable green hydrogen production solutions to decarbonise industrial processes.This paper will cover the status and main results of R&I activities in PEM fuel cells and electrolysers supported by the Clean Hydrogen Partnership, including an overview of the European competitiveness in this sector.

Electrophoretic Deposition of Polyethylene Oxide-Based Gel-Polymer Electrolyte for 3D Lithium-Ion Batteries

Despite the advances made in lithium-ion batteries (LIBs) over the last few decades, improved energy and power density is still required for portable devices, transit, and stationary applications [1-3]. Along with developing new materials, optimizing the shape of the battery electrodes is critical for improving the battery performance since the structure of these electrodes has a large impact on ion movement and reaction kinetics. The appeal of 3D structured batteries comes from certain operating features that are not available with conventional 2D geometries. One important feature is the ability to increase areal capacity (mAh cm−2) within a given footprint area of the electrode .Up to today, various methods were employed to coat the foam-type 3D electrodes with polymer or solid-state electrolytes: spin coating, layer-by-layer, and drop coating. Nonetheless, only a number of full-cell operation cases were disclosed, which led to the conclusion that, despite many attempts, drawbacks still exist in solving the homogeneous coating problem of polymer electrolytes.In this work, we report on the simple and facile coating process of polymer electrolyte on the intricate 3D structured NiO@Ni foam anode with the electrophoretic technique. To the best of our knowledge, it was not yet reported in the literature. The conformally coated polymer layer is proven to be very thin and homogeneous without any defects. The NiO@Ni foam/PEO configuration without the use of a commercial separator displayed stable cyclability up to 100 cycles with capacity retention of 88% and coulombic efficiency of 99%. The results are very promising for solving the problem of integrating polymer electrolytes onto any 3D structured anodes.In summary, a facile and simple electrophoretic technique was employed to conformally coat PEO gel-polymer electrolyte onto foam-type NiO/Ni anode for LIBs for the first time. Two electrodes of NiO/Ni foam as a working electrode and Pt metal as a counter electrode were used for the EPD process. Where the PEO solution acted as an electrolyte and, in the end, formed on the NiO/Ni foam surface. Through investigating various layers of PEO, it was concluded that the method allowed obtaining homogeneous thin films of around 2.66 μm for optimal 10 layers, which were free of cracks and defects. The electrochemical performance of the gel-polymer electrolyte PEO with commercially available liquid electrolyte 1M LiPF6 electrolyte solution in EC/EMC/DC was comparable to the traditional separator when used without it in a half-cell with lithium. The cycling stability results displayed an outstanding performance for the PEO electrolyte, delivering a capacity of 406 mAh g-1 at a 0.1 C rate after the 100th cycle. The stability of the formed PEO on the surface of the anode was demonstrated by FTIR analysis after 100 cycles. The stated simple approach allowed a cell operation at room temperature without a commercial separator, which is an excellent result for further developing high-energy-density full 3D batteries.

(Invited) Understanding PEMFC by Advanced Electron Microscopy

A thorough knowledge of the atomic structure and composition of catalyst nanoparticles is paramount to the development of advanced materials for proton exchange membrane fuel cells (PEMFC), one of the most promising energy conversion devices for automotive and stationary applications. Pt and Pt-based alloys nanoparticles (NPs) are currently used as the catalyst to promote the kinetics of the hydrogen oxidation and oxygen reduction reactions in the anode and cathode of the fuel cell, respectively. Yet, the durability of the catalysts remains a major issue for their commercialization. In addition, it is essential to characterize the ionomer distribution and coverage over the catalyst NPs and the carbon support, as the ionomer/catalyst interface plays a critical role in the ORR and MEA fuel cell performance.Ideally, voltage cycling of the membrane electrode assemblies would be performed in-situ within a TEM, but these experiments are highly challenging, since separate gas phase reactants need to be present simultaneously, in particular hydrogen and oxygen Instead, a very close approximation to a true in-situ experiment is done via potential cycling in a half-cell in the presence of liquid electrolyte, as opposed to solid electrolyte in a single cell. This allows us to observe the exact same location before and after cycling through a technique called identical location TEM/STEM (IL-TEM/STEM). Under these conditions, various electron microscopy techniques, such as bright-field TEM and HAADF STEM coupled with EDS and EELS can be performed. To better acquire and understand TEM/STEM-based experimental images, in particular the selection of appropriate operating conditions, and interpretation/validation of the results, it is critical to perform multislice TEM/STEM image simulations to calculate the interaction of an electron beam with a material system.In this talk, the focus is to understand the behavior of Pt and Pt-alloy NPs during the various stages of fuel cell cycling. For this purpose a set-up was developed to simulate the effect of voltage cycling on the cathode side of the fuel cell. In this set up, catalyst NPs supported on carbon nanotubes and amorphous carbon were observed by advanced transmission electron microscopy, before and after cycling. In particular, we studied Pt and Pt-alloy NPs and carbon support degradation mechanisms as a function of cycling using for the first time a combination of 2D IL TEM and 3D IL TEM. This new approach reveals many unpredictable features of morphology changes/behavior of Pt NPs and carbon support, after experiencing the long durability test. These new findings provide an insight which great surpasses what have been observed using solely 2D IL TEM.The experiments show particle migration in conjunction with carbon corrosion during the initial cycles, whereas the appearance of single atoms and atomic clusters on the surface of the carbon support appear after additional voltage cycling as a result of surface dissolution of NPs. For the case of alloyed NPs, the experiments show a heterogeneous deposition of Pt on the NPs. Moreover, we demonstrate a novel approach to distinguish the ionomer phase from the carbon support in PEMFCs, by employing the carbon signal in STEM-EELS, using two types of detectors. In this fashion, not only the ionomer, but also the carbon support, can be mapped in high spatial resolution, despite some damage caused by the electron beam.

Transient Characteristics of the Low-Temperature PEMFC: A Comparative Analysis Using a Physics-Based Model

Low-temperature proton exchange membrane fuel cells (LT-PEMFCs) have experienced a considerable technological leap in the last few decades for transportation and stationary applications. Specifically, the precious metal loading in the catalyst layers (CLs) is notably decreased while enhancing the overall cell performance.1 However, the durability and cost remain major factors that affect the widespread commercialization of the LT-PEMFC. Though this can be achieved with further material development, some existing issues may be resolved by implementing effective design and control strategies. A good understanding of fuel cell water dynamics is required to improve durability and performance. Although some dynamic characteristics can be observed from the experiments, a physics-based model of the LT-PEMFC is necessary to study in-depth transient responses under various conditions like current profiles, operating temperatures, pressure, and humidification levels. Lately, the transient analysis of the fuel cell has gained more attention to elucidate the complex transport phenomena.2 Several transient models of the LT-PEMFC are reported to capture the two-phase behavior inside the cell. Usually, these models are 1D, 2D, or single channel 3D with assumptions like isothermal operation, vapor-equilibrated membrane, simplified reaction kinetics, and more.3–5 Hence, they do not provide spatio-temporal insights into the cell performance containing water dynamics with various flow configurations.The current study focuses on a transient physics-based model of the LT-PEMFC for dynamic analysis across its thickness and flow channels. The membrane used in LT-PEMFC requires humidification to enhance the ionic conductivity and function properly.6 This study considers Schroeder’s paradox for the membrane, which exhibits a different water uptake behavior in the presence of saturated water vapor and liquid water.7 The water uptake property is strongly dependent on the temperature. Therefore, we have developed a single polynomial expression for the membrane water uptake, including temperature and water activity dependency. Using the governing equations & empirical correlations from the numerical and experimental studies, we develop a comprehensive 3D, multiphase, non-isothermal, transient physics-based model of the LT-PEMFC that can closely approximate the liquid water transport under various operating conditions. It is a Multiphysics model that couples electrochemical reactions, porous media flow, transport of reactant species, liquid water transport, heat generation, charge transfer, and ionomer water transport. COMSOL Multiphysics is used to solve the model. It provides a spatio-temporal water distribution inside the membrane, CL, microporous layer, gas diffusion layer, and flow channels. Experiments are performed on 32 cm2 LT-PEMFC with the hybrid flow configuration at 75 °C and 80% RH to validate the physics-based model in the steady state condition. The validation study suggests that the present multiphase model estimates the LT-PEMFC performance with an acceptable RMS current density error of 15 mA/cm2. The simulations are operated in the Galvano-dynamic mode, and the corresponding LT-PEMFC response for the hybrid configuration is shown in Figure 1(a) at various operating pressures. Also, the preliminary results of the liquid water saturation under the channel and rib are incorporated in Figure 1(b). It shows that the water accumulation under the rib is more than the channel due to lower local temperature and weaker convection under the rib, promoting water vapor condensation. Further, the comparison between hybrid and parallel configurations is performed and illustrated in this presentation. Another objective is to study how quickly the liquid water saturation and membrane water content react upon changing the load cycle, RH, operating temperature, and flow configuration. This work is an important step toward understanding the impact of various flow configurations and operating conditions on the water dynamics and membrane water content inside the LT-PEMFC. The developed physics-based model would be extended further by considering the membrane deformation due to the shrinking-swelling under the humidification and thermal cycling, which is critical for the performance and degradation.

An Ultrafast, Durable, and High-Loading Polymer Anode for Aqueous Zinc-Ion Batteries and Supercapacitors

With high theoretical capacities (820 mAh g−1 and 5855 mAh cm−3), suitable electrochemical potential (−0.763 V vs standard hydrogen electrode), low cost, and rich abundance of component materials, aqueous zinc-ion batteries (ZIBs) and capacitors (ZICs) have exhibited great promise for grid-level energy storage and other stationary applications. Zn metal as excessive Zn are often used to compensate for the uncontrollable dendritic growth, corrosion behaviour, and low Coulombic efficiency (CE) of the Zn metal. As such, most of the ZIBs and ZICs developed using these electrode materials exhibited actual device energy and power densities that were significantly lower than the corresponding theoretical values. Another key performance metric that needs to be improved in ZIBs is their high-rate charge and discharge. In addition to the dendrite-derived problems commonly experienced in batteries based on other metal anodes, ZIBs are disadvantaged by hydrogen gas evolution from water decomposition especially under high-rate charge/discharge, leading to poor cycle life.Herein, an ultrafast, stable, and high-loading polymer anode for aqueous Zn-ion batteries and capacitors (ZIBs and ZICs) is developed by engineering both the electrode and electrolyte. The anode polymer is rationally prepared to have a suitable electronic structure and a large π-conjugated structure, whereas the electrolyte is manufactured based on the superiority of trif late anions over sulfate anions, as analyzed and confirmed via experiments and simulations. This dual engineering results in an optimal polymer anode with a low discharge potential, near-theoretical capacity, ultrahigh-loading capability (≈50 mg cm−2), ultrafast rate (100 A g−1), and ultralong lifespan (one million cycles). Its mechanism involves reversible Zn2+/proton co-storage at the carbonyl site. When the polymer anode is coupled with cathodes for both ZIB and ZIC applications, the devices demonstrate ultrahigh power densities and ultralong lifespans, far surpassing those of corresponding Zn-metal-based devices. Figure 1

Co-Free Heteroatom-Doped P2-Type Layered Oxide Cathodes: Advancing High Power Sodium-Ion Battery Technology

Sodium-ion battery technology has been blooming as an indigenous solution to stationary storage applications, triggering the cultivation of a cutting-edge alternative to the archaic lithium-ion (Li-ion) batteries due to high abundance, inexpensiveness, sustainability, safety and similar redox chemistry as of Li-ion technology 1. Although Na-ion batteries are propitious however, challenges such as long-term stability, high energy density, high specific capacity have impeded the practical application 2. The stepping stone for a successful Na-ion battery lies in the cathode, thus researchers have focused on development of layered oxide cathode. These are classified into P2, P3, O3 phases, depending on the environment of Na (prismatic or octahedral) and the stacking sequence of the anionic layers 3. P2-type Na0.67Ni0.33Mn0.65O2 (NMNO) cathodes offer high theoretical capacity, environmental friendliness, air-moisture stability, facile synthesis, and direct sodium-ion diffusion. However, there are still some setbacks, such as limited reversible capacity, rapid capacity decay, sluggish Na-ion kinetics, cracking and exfoliation in the crystallites 4. In order to overcome the challenges faced by sodium-ion batteries, researchers have employed several strategies such as inert or active cation substitution, limiting the cut-off voltage, surface modification, preparation of mixed-phase materials, sodium compensation additives, selection of binder, and choice of electrolyte 5. One of the most effective strategies is the doping of electrochemically inactive transition metals in layered transition metal oxide cathodes. However, a better understanding of the parameters that govern the stability of these cathodes are still necessary.By exploring the various factors that impact the stability of layered transition metal oxide cathodes, we propose a novel approach to synthesize a durable P2-type Na0.67Ni0.33Mn0.65Nb0.02O2 (NMNNbO) electrode with robust hexagonal crystallites through a quick, energy-efficient and cost-effective microwave-irradiated synthesis technique. Previous studies have utilized modified Pechini or conventional solid-state routes for inactive transition metal doping, which can be expensive, time-consuming and energy-intensive 6. This leads to an efficient cathode material with higher capacity and improved rate capability, which could be produced on a commercial scale at a lower cost due to the reduced synthesis time. A comprehensive investigation of the cathode material through X-ray diffraction analysis (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HR-TEM), X-ray photoelectron microscopy (XPS), reveals its superior electrochemical performance, stability, and durability. Through the use of advanced in-situ and ex-situ characterization techniques, the mechanism of Na-ion insertion and extraction, phase transition, and crack formation have been elucidated. Additionally, first-principle calculations using density functional theory (DFT) have been employed to gain a deeper understanding on the role of Nb in the cathode material. Electrochemical characterization was done against Na-metal in a half-cell format utilizing the electrolyte, 1 M NaPF6 in ethylene carbonate and propylene carbonate (1:1). The practicality of the material has also been validated through the evaluation of a full-cell performance against pre-sodiated hard carbon anode. A deeper understanding of the parameters affecting the electrochemical performance, can accelerate the development of high power and durable sodium-ion batteries, making them a more viable option for energy storage applications.

Building a P2D Model for the NiMH Battery

For understanding a battery when working under realistic conditions, a dynamic battery model is a useful tool. One of the most known electrochemical model types for batteries is the Newman P2D model.[1] This model has a good balance between complexity and computational efficiency. Due to the level of complexity, using a P2D model allows us to make simulations to optimize battery design by adjusting parameters such as electrode porosity and tortuosity, electrode thickness, and overall cell thickness. But it can also be used to optimize battery management system (BMS) functionality. There are many studies made on different Li-ion type batteries when it comes to P2D modelling, but to our knowledge there is no dynamic NiMH P2D model reported in literature. In this study we have created a dynamic P2D model through combining it with two previously developed models focused on the specific difficulties on NiMH modelling: Hysteresis estimation and gas behavior. [2,3]Two phenomena are paramount to include in dynamic NiMH battery models: the open circuit voltage (OCV) hysteresis; and the oxygen evolution/recombination reactions in the cell. The OCV hysteresis manifests as an OCV dependence on battery charge/discharge history. In the NiMH battery, the OCV hysteresis is of such a magnitude that one OCV value can be indicative of an SOC ranging between 20% and 90%, making any type of SOC determination algorithm unusable without taking the hysteresis behavior into account.[2] The hysteresis can predominantly be traced to the phase changes that takes place in the positive electrode as it is charged and discharged. This suggests that models of other battery electrodes with significant phase changes, such as LiS and Si, will have to take this behavior into account as well. While the hysteresis effect affects the energy efficiency of the battery, the gas reactions affect the coulombic efficiency of the battery. Since the NiMH battery has a water-based electrolyte, once the positive electrode voltage reaches above the oxygen evolution potential oxygen is produced.[3] This parasitic reaction diverts current from charging the battery, decreasing the coulombic efficiency. Once the oxygen reaches the negative electrode it is recombined and releasing the lost energy as heat. A model that fails to take the gas behavior into account will have difficulties to properly simulate the temperature behavior in the cell. In addition, the decreased coulombic efficiency affects any coulomb counting done as a part of SOC tracking in the cell.A dynamic model that takes both these behaviors into account can be used for many different purposes. Algorithms for use in battery management systems (BMS), for example end of charge criteria and state of charge estimation, will have higher accuracy when optimized using the model. A digital twin based on such a model can be used to monitor battery performance and deviations. System dimensioning can be optimized to achieve the best cost-to-life ratio. It can also be used to develop better usage patterns to get the most out of the battery. Through using the model to develop more efficient usage patterns, the influence of hysteresis and the gas evolution can be minimized, thereby increasing the efficiency of the system.[1] K.E. Thomas, J. Newman, R.M. Darling, Mathematical Modeling of Lithium Batteries, in: Adv. Lithium-Ion Batter., Springer US, Boston, MA, 2002: pp. 345–392. https://doi.org/10.1007/0-306-47508-1_13.[2] J.B. Axén, H. Ekström, E.W. Zetterström, G. Lindbergh, Evaluation of hysteresis expressions in a lumped voltage prediction model of a NiMH battery system in stationary storage applications, J. Energy Storage. 48 (2022). https://doi.org/10.1016/j.est.2022.103985.[3] J. Börjesson Axén, H. Ekström, E. Widenkvist Zetterström, G. Lindbergh, A NiMH dynamic pressure composition model for on-line applications, Manuscript

Integrating Micro-Patterned Flow Fields into Electrode Architecture Via Non-Solvent Induced Phase Separation for High Performance Redox Flow Batteries

To facilitate increasing penetration of intermittent renewables in the energy mix, there is a growing need for energy storage technologies. Redox flow batteries (RFBs) have attracted significant attention in recent years due to their suitable characteristics for long-duration stationary energy storage applications. However, the wider adoption of RFB systems is still limited by the capital cost, to which the reactor stack is a large contributor[1]. Further cost reduction can be achieved by reducing kinetic, mass-transfer, and ohmic losses to improve the stack performance. Porous electrodes are key components within the battery stack, providing active sites for electrochemical reactions, and transport pathways for active species. Commercially available carbon-fiber electrode architectures include carbon paper, carbon felt, and carbon cloth. They have a highly porous structure, but their relatively low surface area and low hierarchical fiber orientation increase both electrochemical and pumping losses[2]. There is still a need to develop a low-cost porous electrode that meets the requirements of high active surface area and facile electrolyte transport to enhance battery performance and system efficiency.Non-solvent induced phase separation (NIPS) is a manufacturing route in the field of membrane technology, which is widely used to fabricate asymmetric membranes[3]. Recently this route has also been used to fabricate non-fibrous porous electrodes[4]. The microstructure of NIPS electrodes is largely influenced and controlled by the solvent/non-solvent exchange rate at the interface between a polymer solution and a coagulation bath. When the phase exchange process is slow, segregation is delayed. This type of segregation generally results in a sponge-like, relatively dense structure[5]. This sponge-like structure has the advantage of small pore size and high surface area, but also has poor hydraulic permeability and high mass-transfer losses. The trade-off between surface area and permeability needs to be further optimized.In the present study, inspired by the flow field designs widely used in RFBs to guide the electrolyte flow paths for low pressure drop, uniform electrolyte distribution, and high electrochemical performance[6], we propose a strategy to imprint micro-patterned flow fields directly into the electrode architecture during NIPS processing to improve mass transfer properties. NIPS polymer films were cast onto molds with specific micro-patterns, and the resulting micro-channels can be preserved in the electrodes after carbonization. To verify the effectiveness of the micro-patterned electrodes, here, we investigate two selected micro-patterned designs. The groove-patterned electrodes were combined with flow-through flow fields (FT-FFs) for in-plane mass transport optimization, and the pillar-patterned electrodes were combined with interdigitated flow fields (IDFFs) for through-plane flow optimizations[7]. Two geometric sizes of the micro-patterns were considered in each design. The pore sizes and distributions of the micro-patterned electrodes were determined by mercury intrusion porosimetry. The hydraulic permeability of the electrodes was evaluated by half-cell pressure drop measurements, and the electrochemical specific surface area was determined through electrochemical impedance spectroscopy under non-faradaic conditions. In addition, we performed electrochemical battery tests with symmetric iron RFB (0.5 M Fe2+/Fe3+, 2 M HCl) cells and vanadium full-cells (1.6 M V active species at 50% state-of-charge). It was found that due to the small pore size (e.g., ~1 μm) and narrow pore size distribution of the sponge-like NIPS structure, the main contribution to the total losses in electrodes without micro-patterns in electrochemical performance comes from mass-transfer. Electrodes with groove and pillar patterns can help reduce the pressure drop and improve mass transfer properties. Pillar-patterned electrodes with the combination of IDFF show high overall electrochemical performance with greatly reduced mass transport resistances. At an electrolyte velocity of 10 cm/s, the total resistances for kinetic and mass transfer are less than 0.1 Ω·cm2 in symmetric iron cell tests. Compared to the activated commercial electrode (e.g., 2-layer Freudenberg H23 carbon paper, thermally treated at 450 oC for 12 h), the total resistances for kinetic and mass transfer are reduced by ~60%, which shows great potential for adoption in next generation high-performance RFB systems. References J. Noack, L. Wietschel, N. Roznyatovskaya, K. Pinkwart, J. Tübke, Energies, 9, 627 (2016).A. Forner-Cuenca, F.Brushett, Current Opinion in Electrochemistry, 18, 113-122 (2019).H. Wang, J. Jung, J. Kim, S. Kim, E. Drioli, Y. Lee, Journal of Membrane Science, 574, 44-54 (2019).C. Wan, R. Jacquemond, Y. Chiang, K. Nijmeijer, F. Brushett, A. Forner-Cuenca, Advanced Materials, 33, 2006716 (2021).D. Wang, J. Lai, Current Opinion in Chemical Engineering, 2, 229-237 (2013).X. Ke, J. Prahl, J. Alexander, J. Wainright, T. Zawodzinski, R. Savinell, Chemical Society Reviews, 23, 8721-8743 (2018).V. Muñoz-Perales, P. García-Salaberri, A. Mularczyk, S. Ibáñez, M. Vera, A. Forner-Cuenca, ChemRxiv, (2023).

Carbon-Free, Connected Core-Shell Nanoparticle Catalysts with Advanced Oxygen-Reduction Performances for PEFCs

As the world faces diminishing non-renewable energy sources and a surge in global pollution, establishing a hydrogen and low-carbon economy has become crucial. Polymer electrolyte fuel cells (PEFCs) hold great promise as a sustainable energy source with the potential for high efficiency, and clean power generation in both stationary and mobile applications. However, the conventional platinum nanoparticle catalysts on carbon support (Pt/C) used for the oxygen reduction reaction (ORR) at the cathode shows sluggish ORR activity, leading to high cost and inferior PEFC performance. Moreover, the carbon-supports used for the Pt catalysts are susceptible to degradation caused by carbon-corrosion during start-stop operations, which can severely compromise the overall performance of the PEFCs. Hence, in order to significantly enhance the commercial viability of PEFCs, considerable progress must be made in terms of cost, performance, and durability.Previously our group has reported carbon-free, connected Pt-alloy catalysts to address the above issues. This catalyst is composed of connected Pt-alloy nanonetworks with high electronic conductivity and exhibits enhanced ORR activity, high start-stop durability, and thin catalyst layers. Specifically, this catalyst exhibited 9 times higher specific activity than that of the commercial Pt/C, making it an excellent candidate for cathode catalyst applications.[1,2] However, high-temperature annealing process is required to develop connected networks between the Pt-alloy nanoparticles, resulting in larger crystallite sizes and reduced surface areas. This limitation has prevented connected Pt-alloy catalysts from achieving significant improvement in mass activity.In this work, we have proposed a novel synthesis method that enables the development of connected core-shell nanoparticle catalysts without any high-temperature treatment. This method eliminates the particle growth and exhibit a high surface area, making it highly effective for ORR applications. Here, a carbon-free catalyst with a core-shell nanonetwork structure having a non-Pt (Pd) core and Pt shell was developed. Additionally, the relationship between the thickness of the Pt-shell layer and ORR activity was investigated.Connected core-shell catalysts with Pd nanoparticles as core and Pt as atomic shell (Pd@Pt) were synthesized in a one-pot polyol process that does not require high-temperature annealing as shown in Fig. 1. The formation of connected Pd@Pt core-shell nanonetworks (< 10 nm) was confirmed by TEM and STEM-EDX analysis. Also, the structure of Pt shell on core metals was successfully tuned by controlling the reaction temperature and time, precursor ratio, etc. Here, the number of the Pt layers on the surface of the connected Pd@Pt core-shell catalysts were varied from 1–6 atomic layers and the results show that the ORR mass activity was notably enhanced in the catalyst with a moderate shell thickness ranging from 2.5 to 3.5 Pt atomic layers. This suggests that connected Pd@Pt catalyst with a moderate Pt layer achieves both high surface area and ORR specific activity. The high surface area of the developed catalysts is attributed to a new synthesis method that does not use high temperature annealing and a low Pt core-shell structure. The improvement in ORR specific activity can be attributed to the more suitable d-band center position of the Pt shell, which is influenced by strain and ligand effects resulting from the Pd core. The ORR performance of the carbon-free connected Pd@Pt catalyst showed 2–4 times enhancement in electrochemical surface area (ECSA) and 1.5–3 times improvement in ORR mass activity compared to the connected Pt-alloy catalysts prepared using high-temperature annealing. Further, high durability of the connected core-shell catalyst against load cycles (0.6 ↔1.0 V) at 60 °C in acidic electrolyte solution was also demonstrated, indicating that a high stability nanonetwork connected by Pt atomic shell.In summary, we have successfully demonstrated a new synthesis method for the formation of connected core-shell nanoparticles by Pt atomic shell without high-temperature annealing and prepared a carbon-free, connected Pd@Pt core-shell catalyst with advanced ORR performance, highlighting its great potential as a cathode catalyst. Acknowledgement The part of this presentation is based on results obtained from a project, JPNP20003, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

Impact of Reinforced Polymer Electrolyte Membrane Scratch on Fuel Cell Durability Using 4D X-Ray Computed Tomography Technique

PEMFCs, or Polymer Electrolyte Membrane Fuel Cells, can be used in both stationary power and transportation applications and are promising for use in heavy duty electric vehicles due to their high energy density, ability to be refueled quickly, and extended range, which are key challenges for battery-powered vehicles [1]. Despite these advantages, there are still obstacles preventing the widespread commercialization of PEMFCs, one of which is production cost [2]. To reduce manufacturing costs, it is imperative to ensure that quality control rejects and scraps are minimized. Moreover, enhancing component integration defect detection would ensure the durability of the fuel cell and enhance its operational lifetime. However, robust quality control requires a thorough understanding of potential non-uniformities and their effects on fuel cell performance and operational degradation.Non-uniformities of the membrane electrolyte assembly (MEA) can result in durability issues by damaging the membrane and making it more vulnerable to mechanical and chemical stress during the operation [3]. Several studies have been done on cation contamination and membrane pinholes and their effect on fuel cell performance and durability [4,5] but little attention has been paid to other types of non-uniformities such as membrane scratches and foreign particles, which may also conceivably affect durability [6]. By implementing 4D in-situ X-ray computed tomography (XCT) [7,8], the current work aims to track the evolution of scratches that appear on a reinforced membrane surface during fabrication and its specific objective is to determine the impacts of membrane scratches on membrane durability in fuel cells.The study was conducted by using small-scale fuel cells with GORE-SELECT® membranes that were intentionally scratched with a razor blade, subjecting them to combined chemomechanical membrane accelerated stress test (AST), and monitoring the membrane degradation and evolution of the scratches using 4D-XCT throughout the AST. During the fabrication step, the depth of scratches was regulated by a weak bond between the reinforcement layer and the perfluorosulfonic acid (PFSA) layer, i.e., the scratches did not tear through the reinforcement. Furthermore, the scratches did not adversely impact the initial cell performance. However, during AST operation the evolution of the scratched region was affected by several factors, including the friction between the layers of the membrane electrode assembly, the width of the scratch (Figure 1), the presence of membrane debris, and the extent of membrane strain. Additionally, it was observed that changes in the quality of catalyst layer transfer onto the scratched region can alter the degradation pattern and potentially create a self-mitigating mechanism. These findings may be used to develop more optimized quality control measures for membrane scratches in fuel cell production. Acknowledgements This research was supported by the Natural Sciences and Engineering Research Council of Canada, Canada Foundation for Innovation, British Columbia Knowledge Development Fund, Western Economic Diversification Canada, Ballard Power Systems, and W.L. Gore & Associates. This research was undertaken, in part, thanks to funding from the Canada Research Chairs program. Keywords: fuel cell; membrane durability; X-ray computed tomography; membrane scratch; manufacturing References [1] Cullen DA, Neyerlin KC, Ahluwalia RK, Mukundan R, More KL, Borup RL, et al. New roads and challenges for fuel cells in heavy-duty transportation. Nat Energy 2021;6:462–74. https://doi.org/10.1038/s41560-021-00775-z.[2] Whiston MM, Azevedo IL, Litster S, Whitefoot KS, Samaras C, Whitacre JF. Expert assessments of the cost and expected future performance of proton exchange membrane fuel cells for vehicles. Proc Natl Acad Sci U S A 2019;116:4899–904.[3] De Bruijn FA, Dam VAT, Janssen GJM. Review: Durability and degradation issues of PEM fuel cell components. Fuel Cells 2008;8:3–22.[4] Tavassoli A, Lim C, Kolodziej J, Lauritzen M, Knights S, Wang GG, et al. Effect of catalyst layer defects on local membrane degradation in polymer electrolyte fuel cells. J Power Sources 2016;322:17–25.[5] Lü W, Liu Z, Wang C, Mao Z, Zhang M. The effects of pinholes on proton exchange membrane fuel cell performance. Int J Energy Res 2011;35:24–30.[6] Kundu S, Fowler MW, Simon LC, Grot S. Morphological features (defects) in fuel cell membrane electrode assemblies. J Power Sources 2006;157:650–6.[7] Ramani D, Singh Y, White RT, Wegener M, Orfino FP, Dutta M, et al. 4D in situ visualization of mechanical degradation evolution in reinforced fuel cell membranes. Int J Hydrogen Energy 2020;45:10089–103.[8] White RT, Eberhardt SH, Singh Y, Haddow T, Dutta M, Orfino FP, et al. Four-dimensional joint visualization of electrode degradation and liquid water distribution inside operating polymer electrolyte fuel cells. Sci Rep 2019;9:1–12. Figure 1

(Invited) Effect of Temperature on Lithium-Ion Battery Voltage Response and How to Model It in the Mechanistic Modeling Approach

The ongoing usage of lithium-ion cells and packs in both stationary and mobile applications necessitates comprehensive tools and models to diagnose and prognose cell performance onboard. One of the main tasks of a battery management system is to infer the state of charge (SOC) and state of health (SOH) of batteries. SOC estimation is usually done by relating a measured relaxation voltage to a stored SOC versus open circuit voltage (OCV) curve. The latter is dependent on the cell SOH and its degradation path. Therefore, both an accurate OCV and relaxation measurement are necessary for state estimation and it is essential to consider how they vary with temperature to ensure accuracy.This study aims at an exploration of the impact of temperature on relaxation and cell’s kinetics and how the voltage response at different temperatures can be simulated using the mechanistic modeling framework by tuning two parameters, the ohmic resistance increase and the rate degradation factor. The mechanistic modeling framework is using electrode half-cell data to synthesize the terminal voltage of battery cells based on the individual electrode potentials. Although proven valid in the quantification of degradation modes, path dependence of aging and cell-to-cell variations, the application of this modeling framework has been restricted so far mostly to voltage profiles recorded at room temperature and low rates. To be used in deployed battery management systems, this limitation should preferably be overcome to enable on-board diagnostics from medium to high rates and at any temperature.

Towards Energy Dense Rechargeable Batteries Utilizing Zn and Cu

Batteries are easy to use, remotely monitorable, not fuel dependent, easily permitted and installed, and start automatically and reliably during an electrical outage. This makes them optimal for stationary storage and power assurance applications. Within battery-based grid storage, as of mid-2017, lithium-ion, sodium-ion, and lead-acid systems are the leaders, comprising 59% (~1.1 GW), 8% (0.15 GW), and 3% (0.06 GW) of global operational electrochemical storage, respectively.1 However, these batteries suffer from low energy density, high cost, poor safety, environmental concerns, and/or cycle life. Existing battery options on the market also do not meet the required market needs for long-duration backup power. For example, lead-acid batteries require too much space, are heavy, and contain toxic materials. Lithium-ion batteries, while compact and capable of excellent cycle life, are too expensive to serve long outages and have notable flammability and environmental risks.Alkaline Zn batteries are a strong candidate for electrical grid storage applications due to Zn’s high capacity (820 mAh/g), established materials supply chain and low cost. To realize the highest energy dense batteries, Zn needs to be coupled with a similarly low cost, abundant and high-capacity cathode. CuO (674 mAh/g) is an intriguing high-capacity cathode when paired with Zn in alkaline electrolyte, a battery that until recently has been relegated to the history books as a primary system. In 2021 Schorr et al. reported a rechargeable Zn/CuO battery that utilized a Bi additive to help facilitate the electrochemical reversibility of the Cu conversion electrode. Bi2O3, a species with comparable redox potentials to Cu2O, promoted reversibility and minimized passivation in the historically non-reversible system. The battery cycled without any observable Cu and Bi mixed oxide phases, cycling between metallic Cu and Bi and Cu2O/Cu(OH)2 and Bi2O3, respectively. Although the Bi additive did not eliminate capacity fade completely, limiting the cells to a 30% depth of discharge (relative to CuO) enabled 250 cycles at > 124 Wh/L. Alternatively, compensating for capacity loss with additional Cu metal provided for very high areal capacities (∼40 mA h/cm2) and energy densities (∼260 W h/L), despite only 65% active material cathode loadings and ∼10% Zn anode utilization; however, preliminary tests indicated these batteries were prone to shorting.Seeking to improve performance and minimize the spatial segregation of Cu- and Bi-phases observed upon cycling in the prior system, D. Arnot et al. prepared nanoscale carbon coated (Cu/Bi) particles, where the coating partially minimized dissolution and diffusion of soluble cuprate and bismuthate complexes, where ~ 200 cycles at 300 mAh/g was demonstrated (@ ~ 100 Wh/L). CuBi2O4 and CuO phases were formed upon oxidation, indicating carbon coatings can affect the battery cycling mechanism and may have future roles increasing performance.Data collected from a variety of experimental techniques, including cyclic voltammetry, rotating ring-disk electrode voltammetry, electrochemical impedance spectroscopy, electron microscopy, transmission electron microscopy, Raman spectroscopy, operando energy-dispersive X-ray diffraction measurements, battery cycling along with recent DFT modeling will be presented to help elucidate the role of additives, carbon coatings, and ion selective polymers in enabling reversible Zn/Cu based batteries. In addition, the general challenges of achieving a highly reversible energy dense battery based on two conversion electrodes operating in highly alkaline environment will be discussed.A near-term goal is to demonstrate a Zn/CuO battery with long lifetime, at appreciable energy densities (> 200 Wh/L), with excellent safety, lower toxicity and sufficiently low cost to be manufactured and installed on the grid. While the laboratory scale Zn/CuO battery builds have very promising characteristics to date they have not been optimized or adapted for consumer or market-based needs in terms of power performance, energy density, cycle life or stability in terms of shelf life and the ability to tolerate partial state of charge. Progress towards these goals may also be discussed.This work was supported by the U.S. Department of Energy, Office of Electricity, and the Laboratory Directed Research and Development program at Sandia National Laboratories. Sandia National Laboratories is a multi-mission laboratory managed and operated by National Technology and Engineering Solutions of Sandia, LLC, a wholly owned subsidiary of Honeywell International, Inc., for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-NA-0003525. The views expressed herein do not necessarily represent the views of the U.S. Department of Energy or the United States Government.N. Schorr et al. ACS Applied Energy Mater. 2021, 4, 7, 7073–7082. https://doi.org/10.1021/acsaem.1c01133.D. J. Arnot et al. J. Power Sources 2022, 529, 231168. https://doi.org/10.1016/j.jpowsour.2022.231168.

Dynamic Electrochemical Impedance Spectroscopy for Characterization of the State of Health of Graphite Electrodes

Graphitic carbon is the most used material as anode in lithium-ion batteries since the last 30 years. To make batteries cost-effective for mobility or stationary applications the optimization of every aspect is crucial. Advanced techniques can be implied to undercover or demonstrate the main chemical processes at the graphite electrode such as the Electrochemical Impedance Spectroscopy (EIS). EIS is a powerful technique able to reveal and separate resistive and capacitive properties of an interface in a non-destructive way. It has been applied for the characterization of graphite in order to quantify the charge transfer resistance on the intercalation process, to study the mechanism of formation of solid-electrolyte-interface (SEI), and reveal the lithium plating process [1]. There are high requirements for the collection of impedance spectra on a broad range of frequencies (typically from kHz to tens of mHz) at different electrode potentials regarding measurement time and the condition of a system in equilibrium. To overcome these requirements a technique has been developed called Dynamic Electrochemical Impedance Spectroscopy (DEIS). For DEIS a multi-frequency signal, containing all frequencies to probe in a form of summed sine waves, is superimposed to the galvanostatic current. Using this method, it is possible to measure the time-varying impedance while the system is drifting through non-equilibrium states, e.g. during charge/discharge cycling.In this study we propose DEIS measurements performed on a freshly assembled graphite/lithium half-cell cycled at current rates of C/10 and C/5 and 1C (for aging). Figure 1 A shows the working electrode voltage profile of the first 16 cycles. The chosen geometry for the cell is a three-electrode pouch cell with 2x2cm square electrodes and an insulated copper wire with lithium plated at the tip as micro-reference electrode (see Figure 1 B).The novelty of the proposed method is the fully automatized procedure to acquire the dynamic impedance on a wide frequency band (1kHz-10mHz) continuously over an arbitrary number of cycles to investigate the degradation of the electrode. The experimental set-up is shown as a scheme in Figure 1 C [2]. On base of the recorded current and voltage signals, we computed the time-varying impedance using the Dynamic Multi-Frequencies Analysis (DMFA). This method allows to calculate the impedance at the low frequency band by filtering of the sine components in the Fourier domain; the voltage drift is calculate in the same way [3]. An example of the computed time-varying impedance and the respective potential profile for the first cycle is reported in Figure 1 D.

The Role of Energy Density for Grid-Scale Batteries

For grid-scale battery energy storage systems it is often presumed that cell level energy density is not too important. Yet, countless publications highlight low energy density as the key limitation of technologies such as redox flow batteries or aqueous alkali-ion batteries that are inherently developed for stationary applications.Here, we resolve this apparent conflict by quantifying the areal energy density, expressed in kWh m-2, of over forty MWh-scale battery energy storage systems deployed around the world.[1] Via satellite imagery we compare lithium-ion, sodium-sulfur, and flow battery projects and show that the amount of energy that is stored per land area is often comparable between these technologies, even though the energy density on cell level varies by an order of magnitude. We highlight excellent safety and vertical scalability as key untapped advantages of aqueous batteries and provide examples of where they can excel, besides simply competing with state-of-the-art lithium-ion batteries. We show, for example, that MWh-scale aqueous flow batteries can safely be deployed underground and within buildings, feats that due to safety constraints are not possible with current lithium-ion batteries at this scale.Seeing satellite images of battery installations near solar farms is a humbling experience that every researcher working in the field should come across and we provide the locations of all the examined battery installations in a Google Earth file. Grasping the fantastical scale at which renewables are, and must continue to be, deployed certainly provides some perspective regarding energy density of individual battery cells. [1] Reber, D., Jarvis, S.R., Marshak, M.P., The role of energy density for grid-scale batteries, ChemRxiv, 2022, doi: 10.26434/chemrxiv-2022-5ddhs

Long-Life Lead-Carbon Batteries for Stationary Energy Storage Applications.

Owing to the mature technology, natural abundance of raw materials, high recycling efficiency, cost-effectiveness, and high safety of lead-acid batteries (LABs) have received much more attention from large to medium energy storage systems for many years. Lead carbon batteries (LCBs) offer exceptional performance at the high-rate partial state of charge (HRPSoC) and higher charge acceptance than LAB, making them promising for hybrid electric vehicles and stationary energy storage applications. Despite that, adding carbon to the negative active electrode considerably enhances the electrochemical performance. However, carbon brings some adverse effects, such as the severe hydrogen evolution reaction (HER) in the NAM due to the low overpotential of carbon material, promoting severe water loss in LCBs. From a practical application point of view, the irreversible sulfation of the negative active material (NAM) and extreme shedding and softening of the positive active material (PAM) are the main obstacles for next-generation LCBs. Recently, a lead-carbon composite additive delayed the parasitic hydrogen evolution and eliminated the sulfation problem, ensuring a long life of LCBs for practical aspects. This comprehensive review outlines a brief developmental historical background of LAB, its shifting towards LCB, the failure mode of LAB, and possible potential solutions to tackle the failure problems. The detailed LCB's development towards long life was discussed in light of the reported literature to guide the researcher to date progress. More emphasis was directed toward the new applications of LCBs for stationary energy storage applications. Finally, state-of-the-art progress and further research gaps were pointed out for future work in this exciting era.