Modeling and Simulation of an Alkaline Ni/Zn Cell

The majority of Li-ion chemistry varieties consists of flammable materials and therefore may go to unpredictable catastrophic failures. One of the reasons for the battery thermal runaways is the development of low-resistive internal short circuits defined as hard shorts. Unfortunately, currently there are no fast and simple approaches for detecting the earliest signs of growing internal shorts and tracking battery health by this way. This impedes penetration of Li-ion batteries in electric vehicle and energy storage markets. The main objectives of our research are: elimination of thermal runaways and reduction of manufacturing and battery maintenance costs by early identification of potentially faulty cells. Internal shorts increase self-discharge (SD) of batteries. Therefore, the SD metric can serve for battery health estimation. However, presently there is no fast and at the same time direct methods to measure SD that doesn’t require full charge/discharge cycle with long rest times between charge and discharge steps. Conventional methods determine average SD rate for the specific long rest period. They are impractical for online SD measurement. Therefore, the focus and goal of our approach was on the development of a fast SD measurement method that can be incorporated in Battery Management System algorithms. The goal was reached with a suite of experimental electrochemical protocols combined with a newly developed model. The new metric, the SD current, which is determined under potentiostatic conditions at a slight discharge overvoltage, is proposed as a fast SD metric for detection of shorts and assessment of their severity. The slight discharge consumes only negligible capacity with minor state of charge disturbance. However, it allows equilibrating the battery quickly and subsequent determination of SD current as a pure metric at a stable state of charge corresponding to applied voltage. The method doesn’t require disconnection of the battery from the circuit and stabilization of battery voltage before measurement. Measurement can be done in 1–1.5 h or less in comparison with days or weeks for conventional SD measurement. The method is validated using a cell comprising artificial external shorts of different severity and with no short. It precisely differentiates the shorts with different resistivity. In addition, the developed modeling approach allows further decrease in the time of measurement using only initial partial datasets instead of the full set of data. The mathematical description was validated for several runs with 6% deviation from experimental data. A prime advantage of the model lies in the ability to predict SD at different battery state of charges, temperatures, etc. The method is non-invasive, and is battery chemistry and design agnostic. It is capable of the detection of nascent internal shorts as precursors of soft and then hard shorts that cause thermal runaway. Since the method detects early precursors of cell failures far before the point at which a thermal runaway occurs, it enables to provide advanced warning so that corrective action can be taken to avoid fires and cell explosions. The technology based on this patent pending method can be used in electric drive vehicles, stationary energy storage applications, military, aeronautic, as well as for portable electronic devices. It is easy adaptable by any battery management system to monitor battery state of health at any time and at any battery state of charge. Another promising application may be as a tool for the first responders on electric drive vehicles, grid storage and other battery related accidents. It also can be used at battery production, reducing inventory time to detect internal shorts not intentionally introduced to the battery during manufacturing process. Lastly, this technology could facilitate consistent analysis of SD behavior for previously used batteries and their cells that are repurposed within the secondary use industry.

Continuum models for the spatial dynamics of growing cell populations have been widely used to investigate the mechanisms underpinning tissue development and tumour invasion. These models consist of nonlinear partial differential equations that describe the evolution of cellular densities in response to pressure gradients generated by population growth. Little prior work has explored the relation between such continuum models and related single-cell-based models. We present here a simple stochastic individual-based model for the spatial dynamics of multicellular systems whereby cells undergo pressure-driven movement and pressure-dependent proliferation. We show that nonlinear partial differential equations commonly used to model the spatial dynamics of growing cell populations can be formally derived from the branching random walk that underlies our discrete model. Moreover, we carry out a systematic comparison between the individual-based model and its continuum counterparts, both in the case of one single cell population and in the case of multiple cell populations with different biophysical properties. The outcomes of our comparative study demonstrate that the results of computational simulations of the individual-based model faithfully mirror the qualitative and quantitative properties of the solutions to the corresponding nonlinear partial differential equations. Ultimately, these results illustrate how the simple rules governing the dynamics of single cells in our individual-based model can lead to the emergence of complex spatial patterns of population growth observed in continuum models.

The field of advanced batteries faces today two main challenges: development of power sources for electro-mobility (i.e., electrochemical propulsion) and development of storage technologies for load-leveling applications (i.e., large scale batteries). Our starting point in this presentation is state-of-the-art Li-ion batteries. Using carbonaceous anodes and lithiated transition metal cathodes with selected combinations of transition metals may offer very suitable batteries for full EVs. Ni rich Li[NiCoMn]O2, Mn and Li rich Li1+x[NiMnCo]1-xO2 cathode materials operating in the right potential windows can provide Li-ion batteries high enough energy density as needed for full electrochemical propulsion. Also, by combining Li-Ti-O anodes with LiMPO4 olivine cathodes it is possible to demonstrate very suitable battery systems for stationary large energy storage applications. We will review briefly the updated frontier of Li-ion battery technology. Despite the high capability of this battery technology, there are so many applications for power sources in modern life, what promote very strongly a search for more new battery systems. The use of sulfur cathodes in Li batteries can increase considerably their gravimetric energy density, however, the volumetric energy density of Li-sulfur battery systems is not advantageous compared to advanced Li ion batteries. The good news are that in recent years, we see a nice progress in developing durable composite sulfur cathodes. It seems that there are 3 main approaches: encapsulating sulfur in activated carbon matrices, the use of substrates to which the LiSn species formed by sulfur reduction adsorb very strongly and the use of composite cathodes with high loading of sulfur and semi-permeable membranes that avoid transport of LiSn species to the negative electrodes. There is intensive work on Li-oxygen systems. We see progress in development of electro-catalysis for these systems. We will demonstrate electro-catalytic electrodes in Li-oxygen cells, which anodic reactions (Li-peroxide oxidation and molecular oxygen evolution) occur at very low over-potential, that does not endanger the stability of the electrolyte solutions. We demonstrate also red-ox mediators in solutions that facilitate both ORR and OER. Despite the frustration from the slow progress made towards practical directions, it is important to continue investing efforts in Li-oxygen systems. The community should understand that a long-term research is still required in order to see practical horizons to Li-air battery systems. A main problem is the reactivity of all kinds of polar-aprotic solvents towards superoxide and peroxide species formed by oxygen reduction, in the presence of the super-electrophilic Li ions. The intensive work on both Li-S and Li-oxygen systems is connected to a renaissance in efforts to develop practical Li metal anodes for rechargeable batteries. However, intensive studies that were carried out during more than 3 decades, concluded more than 15 years ago that there is no way to cycle Li metal anodes in practical rechargeable Li battery systems. Even if dendrites formation is avoided, continuous detrimental reactions between the active metal and any type of relevant electrolyte solution is inevitable. We will examine briefly what are the chances to overcome the intrinsic problems in using Li metal anodes in practical rechargeable batteries. We may be able to suggest practical alternative anodes for non-aqueous batteries based on sulfur or oxygen cathodes. Discussing other options for “beyond Li-ion batteries” usually includes Na-ion and magnesium batteries. In fact, the plethora of relevant Na-ion insertion cathodes available today is a good surprise, especially since many of them demonstrate excellent kinetics. However, there is no way that Na-ion systems can rival Li-ion battery systems in terms of energy density. Hence, Na-ion systems may be relevant for large energy storage applications, that can benefit from the high abundance of Na in earth crust. However for such uses, demonstrating high stability during prolonged cycling is mandatory. Consequently, a major challenge in R&D of Na-ion batteries is to exhibit the durability required for load-leveling applications. Finally, we will mention the status of R&D of rechargeable Mg battery systems: excellent work was done so far on the anode-solutions part. Several families of electrolyte solutions with wide electrochemical windows, in which Mg anodes are fully reversible were demonstrated. We have not seen yet cathodes materials that function well in the solutions in which Mg anodes are fully reversible, except the low voltage/low capacity Chevrel phase cathode materials. Hence, these systems still require long term research work, especially towards high voltage/high capacity cathode materials. A main incentive to develop rechargeable Mg batteries may relate to advantages in safety and high volumetric energy density.

Energy storage system (ESS) plays a prominent role in renewable energy (RE) to overcome the intermittent of RE energy condition and improve energy utilization in the power system. However, ESS for residential applications requires specific and different configuration. Hence, this review paper aims to provide information for system builders to decide the best setup configuration of ESS for residential application. In this paper, the aim is to provide an insight into the critical elements of the energy storage technology for residential application. The update on ESS technology, battery chemistry, battery charging, and monitoring system and power inverter technology are reviewed. Then, the operation, the pro, and cons of each variant of these technologies are comprehensively studied. This paper suggested that the ESS for residential ESS requires NMC battery chemistry because it delivers an all-rounded performance as compared to other battery chemistries. The four-stages constant current (FCC) charging technique is recommended because of the fast charging capability and safer than other charging techniques reviewed. Next, the battery management system (BMS) is recommended to adapt in advance machine learning method to estimate the state of charge (SOC), state of health (SOH) and internal temperature (IT) to increase the safety and prolong the lifespan of the batteries. Finally, these recommendations and solutions aimed to improve the utilization of RE energy in power system, especially in residential ESS application and offer the best option that is available on the shelf for the residential ESS application in the future.

Owing to their unsurpassed energy density, lithium ion batteries have been adopted for hybridized vehicles, such as the Chevy Volt and the Nissan Leaf, in the aerospace industry, and in stationary energy storage applications. However, as highlighted by several recent high profile safety events, significant challenges remain for the widespread adoption of Li-ion technology in automotive and aerospace applications. These documented safety incidents have been driven by both cell-level and pack level events, and as such, accurate simulation of safety events on both the cell and pack level is needed for fundamental understanding of the underlying physics and safety-conscious design. [1,2,3,4].In this work, using commercially available AutoLion™ software, we demonstrate cell- and pack-level electrochemical/thermal coupled simulation of various types of safety events, including nail penetration, external short, and internal short. Figures 1 and 2 highlight two types of such safety simulations performed. Figure 1 gives the peak temperature of all four cells in a four-cell pack nail penetration; this simulation highlighting the hotter temperature of the interior cells during multi-cell short. Figure 2 illustrates the voltage and current response of an externally-shorted 25Ah L-ion ion cell. In our presentation, we elucidate on the physics of these shorts on both the cell- and pack-level, and demonstrate how simulation can be used to screen various cell and pack designs for safe implementation of safe Li-ion battery technologies. Acknowledgements Partial support of this work by DOE CAEBAT2 program is greatly acknowledged.

Charging up Stationary Energy Storage

Low C-rate charge and discharge experiments, plus complementary differential voltage or differential capacity analysis, are among the most common battery characterization methods. Here, we adapt the multi-species, multi-reaction (MSMR) half-cell thermodynamic model to low C-rate cycling of whole-cell Li-ion batteries. MSMR models for the anode and cathode are coupled through whole-cell charge balances and cell-cycling voltage constraint equations, forming the basis for model-based estimation of MSMR half-cell parameters from whole-cell experimental data. Emergent properties of the whole-cell, like slippage of the anode and cathode lithiation windows, are also computed as cells cycle and degrade. A sequential least-square optimization scheme is used for parameter estimation from low-C cycling data of Samsung 18650 NMC∣C cells. Low-error fits of the open-circuit cell voltage (e.g., under 5 mV mean absolute error for charge or discharge curves) and differential voltage curves for fresh and aged cells are achieved. We explore the features (and limitations) of using literature reference values for the MSMR half-cell thermodynamic parameters (reducing our whole-cell formulation to a 1-degree-of-freedom fit) and demonstrate the benefits of expanding the degrees of freedom by letting the MSMR parameters be tailored to the cell under test, within a constrained neighborhood of the half-cell reference values. Bootstrap analysis is performed on each dataset to show the robustness of our fitting to experimental noise and data sampling over the course of 600 cell cycles. The results show which specific MSMR insertion reactions are most responsible for capacity loss in each half-cell and the collective interactions that lead to whole-cell slippage and changes in useable capacity. Open-source software is made available to easily extend this model-based analysis to other labs and battery chemistries.

Intermediate temperature NaCl-AlCl3-based Al-ion batteries are considered as a promising stationary energy storage system due to their low cost, high safety, etc. However, such a cheap electrolyte has a critical feature, i.e., strong corrosion, which results in the short cycle life of the conventional Al-metal anode and also limits the development of the NaCl-AlCl3-based Al-ion batteries. A noncorrosive electrolyte may be a good choice for addressing the above challenge, while it is difficult to obtain the electrolyte that has advantages of both noncorrosion and low cost. Therefore, here, we report a Ga-metal anode in the affordable NaCl-AlCl3 electrolyte for constructing a long-life stationary Al-ion energy storage system. This featured liquid metal anode shows good alloying and dealloying processes between metallic Ga and Al, as well as renders superior stability of the interface between the electrolyte and the anode (e.g., smoothly running for over 580 h at 2 mA cm-2). No-corrosion and no-pulverization problems appear in this novel liquid/liquid interface. Those advantages demonstrate that the liquid Ga-metal anode has a great promise for the improvement of the NaCl-AlCl3-based Al-ion batteries for large-scale stationary energy storage applications.

Lithium-ion batteries (LIBs) offering the highest energy density among the known battery chemistries are the major contenders for both transportation and stationary storage applications. In order to satisfy the demands of energy density for these applications, new full cell configuration with either improved working voltage or specific capacity is needed to further enlarge its energy density. One candidate that has received a great deal of attention is the spinel cathode LiMn2O4, which offers the advantages of a high operating voltage (4.0 V vs. Li+/Li) and an excellent rate capability. Nonetheless, the relatively low specific capacity of 125 mAh·g-1 is mainly due to the restricted operating voltage between 3 and 4.5 V. In theory, LiMn2O4 cathode can deliver a capacity of ∼297 mAh·g-1 when 2 mole of lithium ions are inserted/extracted into/from both 8a tetrahedral and 16c octahedral sites of the spinel lattice at the voltages of, respectively, ∼4.0 and ∼2.7 V.1 Phase transition related to 4.0 V plateau is highly reversible, involving only two similar cubic spinel phases. However, phase transition related to 2.7 V plateau is partly reversible because a cubic spinel transforms to a tetragonal spinel with Jahn-Teller distortion occurring as a result of Mn3+ formation. The increase in the axial ratio from c/a = 1.0 in the cubic phase to c/a = 1.6 in the tetragonal phase due to the cooperative Jahn-Teller distortion leads to a fracture of large particles, which induces a loss of electrical contact with the current collector upon cycles.2 These effects cause serious capacity fading. However, the dynamic process of this phase transition has never been fully understood due to a lack of characterization techniques. Based on the above considerations, we report an in operando neutron diffraction study to fully understand the ~2.7 V related phase transition in the Li1+xMn2O4 spinel upon electrochemical cycling. We found solid solution formation upon reversible discharge and charge process, although a first-order phase transition is widely believed. The solid solution formation is possibly due to a thick electrode configuration that we applied and a large overpotential it could generate, which is cosistent with the phenomenon that observed under high-rate charging/discharging of LiFePO4 using in situ synchrotron XRD.3 J. B. Goodenough, M. M. Thackeray, W. I. F. David, P. G. Bruce, Rev. Chim. Miner., 1984, 21, 435.S.-H. Kang, J. B. Goodenough, and L. K. Rabenberg, Chemistry of Materials, 2001, 13, 1758-1764.H. Liu, F. C. Strobridge, O. J. Borkiewicz, K. M. Wiaderek, K. W. Chapman, P. J. Chupas, C. P. Grey, Science 344, 7 (2014).

The telecommunications industry relies on a stable power supply for continuous operation. When grid reliability is uncertain, energy storage systems are often used as backup power. Lithium-ion (Li-ion) batteries have become the preferred choice for this purpose due to their high energy density, rapid power delivery, and minimal self-discharge. These advantages make them particularly suitable for the growing energy demands of data centers.Ensuring the long-term reliability of Li-ion batteries in telecom applications requires understanding their capacity degradation, particularly under deep discharge cycling. However, experimentally assessing degradation under varying conditions requires extensive cycling, making the process time-consuming and resource-intensive. Developing a predictive model for battery lifespan provides a practical alternative.This study builds upon previous research in which Li-ion cells were characterized using electrochemical impedance spectroscopy. Charge-discharge data from a deep discharge profile (90%–0% SOC) at a C/2 rate under ambient conditions, performed four times daily to simulate telecom applications with unreliable grid electricity, is used to develop an electrochemical model through parameter estimation in COMSOL v6.2. In many cases, detailed information required for physical modeling is unavailable due to experimental constraints (e.g., lack of specialized measurement equipment) or proprietary restrictions (e.g., undisclosed electrode chemistry). To address these challenges, this study proposes an electrochemical modeling methodology using a limited dataset, including manufacturer specifications (dimensions, nominal capacity, cut-off voltage, and maximum voltage) and experimental charge-discharge curves.A generic 1D isothermal model from the COMSOL library, which assumes standard Lithium manganese oxide (LiMn2O4) chemistry, serves as the starting point, followed by a sensitivity study to assess the influence of various parameters on charge-discharge behavior. An iterative parameter estimation approach is then employed to refine the model which integrates the electrical behavior of the cell, mass conservation, mass transport, and reaction kinetics (P2D electrochemical model). This methodology addresses a gap in the literature, as most Li-ion battery models focus on lower-capacity cells (< 25 Ah), whereas this study examines a high-capacity (115 Ah) battery designed for telecom applications.Initial results successfully replicated the first charge cycle of the experimental data, demonstrating that the model can capture the essential electrochemical behavior even without the actual battery parameters. While the first cycle has been validated, further cycles and additional experimental data will also be used for further validation and model refinement. This successful replication provides a promising validation, laying a solid foundation for future improvements. Future work will focus on enhancing the model’s ability to predict capacity degradation over time and estimate cycle life. Additionally, different battery chemistries will be studied to assess their impact on the model’s performance.

Batteries are an attractive option for grid-scale energy storage applications because of their small footprint and flexible siting. A high-temperature (700 °C) magnesium-antimony (Mg||Sb) liquid metal battery comprising a negative electrode of Mg, a molten salt electrolyte (MgCl(2)-KCl-NaCl), and a positive electrode of Sb is proposed and characterized. Because of the immiscibility of the contiguous salt and metal phases, they stratify by density into three distinct layers. Cells were cycled at rates ranging from 50 to 200 mA/cm(2) and demonstrated up to 69% DC-DC energy efficiency. The self-segregating nature of the battery components and the use of low-cost materials results in a promising technology for stationary energy storage applications.

Rechargeable battery technologies have ignited major breakthroughs in contemporary society, including but not limited to revolutions in transportation, electronics, and grid energy storage. The remarkable development of rechargeable batteries is largely attributed to in-depth efforts to improve battery electrode and electrolyte materials. There are, however, still intimidating challenges of lower cost, longer cycle and calendar life, higher energy density, and better safety for large scale energy storage and vehicular applications. Further progress with rechargeable batteries may require new chemistries (lithium ion batteries and beyond) and better understanding of materials electrochemistry in the various battery technologies. In the past decade, advancement of battery materials has been complemented by new analytical techniques that are capable of probing battery chemistries at various length and time scales. Synchrotron X-ray techniques stand out as one of the most effective methods that allow for nearly nondestructive probing of materials characteristics such as electronic and geometric structures with various depth sensitivities through spectroscopy, scattering, and imaging capabilities. This article begins with the discussion of various rechargeable batteries and associated important scientific questions in the field, followed by a review of synchrotron X-ray based analytical tools (scattering, spectroscopy, and imaging) and their successful applications (ex situ, in situ, and in operando) in gaining fundamental insights into these scientific questions. Furthermore, electron microscopy and spectroscopy complement the detection length scales of synchrotron X-ray tools and are also discussed toward the end. We highlight the importance of studying battery materials by combining analytical techniques with complementary length sensitivities, such as the combination of X-ray absorption spectroscopy and electron spectroscopy with spatial resolution, because a sole technique may lead to biased and inaccurate conclusions. We then discuss the current progress of experimental design for synchrotron experiments and methods to mitigate beam effects. Finally, a perspective is provided to elaborate how synchrotron techniques can impact the development of next-generation battery chemistries.

The battery is the key source of green energy for vehicle movement or powering residential / industrial buildings. The increase in energy demand requires larger battery capacity and energy density to meet power requirements in mobility and stationary energy storage applications such as in emergency power backup, solar power storage, portable power packs, etc., In recent years, the technology used in batteries has improved beyond expectations, mainly due to various cell chemistry. It is essential to understand the basic design and cost challenges in battery design, selection, cell chemistry advancements and on-going research areas in battery cell development. The study uses a detailed literature review, technical comparison of various cell chemistries & applications and identification of key design parameters using technical data comparison. The study reveals that Lithium batteries have an advantage over other cell chemistries due to its specific energy density, cost, scale of production in mobility and energy storage applications.

A key question any battery modeler must grapple with is how much physics to include in a physics-based model. An ideal approach was articulated by Albert Einstein as “everything should be made as simple as possible, but not simpler.” Yet, a quick review of the electrochemical literature suggests an alternative is to embrace the Grateful Dead lyric, “too much of everything is just enough.” Finding the right balance between model complexity and experimental complexity is critical for rigorous model-data convergence, and remains an on-going challenge for nearly every battery chemistry.[1]The publications of honoree Ralph White often resolve this dilemma by incorporating impressively comprehensive physics in a model, along with equally impressive mathematical analysis, so a careful reader can determine, for themselves, what physics matters for the situation they care about. An elegant example of this is the analytical solution for the electrochemical impedance spectroscopy (EIS) response of the pseudo-two-dimensional (P2D) model of a porous insertion electrode [2]. Numerical solutions of the P2D model for linear or nonlinear EIS of a battery, as we have shown,[3-5] allows one to capture the behavior of an experimental battery system, but parameter identification challenges do not always allow rigorous validation of the essential physics. Analytical models such as given in [2] can help sort out what parameters, or clustering of parameters, matter.In this talk we tackle the question of model-data convergence, where the goal is modeling that meets Einstein’s ideal so that quantitative physics-based insights can be extracted and interpreted from experimental data. Just as with modeling, experimental measurements should embrace Einstein’s notion of being simple, but not too simple, if we hope to extract meaningful parameters from real batteries. A key experimental concept introduced in this talk is measurement signal parity in full-cell datasets. We show that a single physics-based model simultaneously fit to two datasets (of opposite signal parity) can help discern half-cell processes from full-cell data. We illustrate this, first, using slow cycling data from commercial NMC|C 18650 cells to non-destructively estimate half-cell thermodynamic parameters from the commercial cells as they cycle and age. The cornerstone of our thermodynamic modeling is adaptation of half-cell methods developed at General Motors,[6] but implemented here for full-cell analysis.[7] We also look at second harmonic nonlinear EIS as a negative parity complement to linear EIS (positive parity) data, but we step back from our prior use of computed P2D models;[3, 5] for our current state of knowledge, P2D models may be closer to the Grateful Dead end of second harmonic EIS battery modeling than Einstein’s ideal. To better align our understanding and ability to extract meaningful parameters, we attempt to thoughtfully build up the physics of nonlinear EIS from a basic physical chemistry description of the electrified interface – a Helmholz double layer and Butler-Volmer charge transfer kinetics – while progressively adding solid state transport and electrode geometry to increasingly capture more of the variance of linear (positive parity) and second harmonic nonlinear (negative parity) EIS experimental data without over-fitting. In both the thermo and EIS examples, one appropriate physics-based model is simultaneously fit to two datasets of opposite parity. Working with battery aging data, we show how this approach for aligning modeling physics to complementary datasets of opposite parity can be used to quantify half-cell physicochemical processes that evolve with cycle aging of an engineered commercial full-cell.[1] M. Cornish and M. Marinescu, Toward rigorous validation of Li-S Battery Models, J.E.S. 169 060531 (2022)[2] G. Sikha and R. White, Analytical expression for the impedance response of an insertion electrode cell, J.E.S. 154(1) A43 (2007).[3] M.D. Murbach and D.T. Schwartz, Extending Newman’s P2D lithium-ion battery impedance approach to include the nonlinear harmonic response, J.E.S. 164(11) E3311 (2017).[4] M.D. Murbach and D.T. Schwartz, Analysis of Li-ion battery electrochemical impedance spectroscopy data: an easy-to-implement approach for physics-based parameter estimation using an open-source tool, J.E.S. 165(2) A297 (2018).[5] M.D. Murbach, V.W. Hu, and D.T. Schwartz, Nonlinear electrochemical impedance spectroscopy of lithium-ion batteries: experimental approach, analysis, and initial finding, J.E.S. 165(11) A2758 (2018).[6] M. Verbrugge, D. Baker, B. Koch, X-C Xiao, and W-T. Gu, Thermodynamic model for substitutional materials: Application to lithiated graphite, spinel MnO, LFP, NMC, J.E.S. 164(11) E3243 (2017).[7] V.W. Hu and D.T. Schwartz, Low error estimation of half-cell thermodynamic parameters from whole-cell li-ion battery experiments: Physics-based model formulation, experimental demonstration, and an open software tool, J.E.S. 169(3) 030539 (2022).

Rechargeable aqueous batteries have gained significant attention as a promising alternative to conventional lithium-ion systems, particularly for grid-level energy storage applications. This growing interest is driven by several key advantages, including superior safety, low cost, environmental compatibility, and the potential for sustainable large-scale production. Historically, lead-acid and alkaline rechargeable batteries have represented iconic examples of aqueous systems, playing pivotal roles in both stationary and portable energy storage. However, recent advancements have led to the exploration of diverse aqueous battery systems that rely on aqueous electrolytes incorporating alkali or multivalent metal ion salts. These systems include lithium-ion aqueous batteries (Li-ion aqueous), zinc-ion batteries (ZIBs), and aluminum-ion batteries (AIBs), each offering unique advantages.A fundamental challenge in aqueous battery technology arises from the complexity introduced by the solvent itself—water. Due to its protic nature, water allows for proton-coupled electron transfer (PCET) reactions, which are commonly overlooked. Understanding these proton-coupled processes is crucial for developing aqueous batteries with high efficiency and long cycle life. Therefore, it becomes essential to differentiate between charge storage mechanisms involving protons and those relying on the reversible insertion of alternative charge carriers, such as lithium ions or multivalent cations. Such differentiation is critical not only for accurately determining the origin of stored charge but also for optimizing battery performance by minimizing parasitic reactions, such as hydrogen evolution or material dissolution.Here, we will present a rigorous and systematic electrochemical methodology to unambiguously reveal reversible proton-coupled charge storage mechanisms using a diverse selection of model electrodes. These include inorganic materials such as TiO₂ and MnO₂, organic compounds like quinone-based electrodes, and metal-organic frameworks exemplified by Prussian Blue. Furthermore, we will demonstrate how to elucidate charge storage mechanisms in aqueous electrolytes containing alternative charge carriers, examining the interplay between proton-coupled processes and the insertion of other ionic species. This multifaceted analysis will not only address the critical question of the proton source within the aqueous electrolyte, but also highlight the impact of proton-coupled charge storage on the formation and evolution of local pH gradients. By systematically investigating these phenomena, we aim to provide a comprehensive understanding of how proton-coupled electron transfer reactions contribute to charge storage across a range of material chemistries.