Rechargeable Research Articles

Non-Destructive Analysis of Pb-Acid Battery Positive Plates, Based on Neutron Tomography

Lead-acid batteries (LABs) are one of the first rechargeable batteries. Historically used for backup power during the early public electricity network, LABs now hold a global market share of approximately 50%, mainly in automotive applications and energy reserves for telecommunication and data networks. Their low energy density and high surge current make them suitable for high-current, in-time applications. The LAB electrochemical cell consists of PbO2 as the positive electrode, metallic Pb as the negative electrode, and H2SO4 as the electrolyte.The composition of the positive electrode active material (PAM) involves mixtures of α- and β-PbO2 and an amorphous gel phase of Pb(IV) oxy-hydroxides, determining the PAM's functional properties. The hydrated Pb(IV) oxy-hydroxide is the electrochemically active phase, conducting ions but not electrons. The mechanical consistency of the PAM relies on α-PbO2, acting as a structural binder, while β-PbO2 provides electronic conductivity. LAB performance is influenced by the proportions of α and β crystalline zones. Jointly, α - and β -PbO2 act as a Pb(IV) reservoir for reduction, occurring through the gel phase during discharge. Together, α- and β-PbO2 function as a reservoir for Pb(IV) reduction, a process that takes place through the gel phase during discharge in lead-acid batteries (LABs). These two crystalline phases, α- and β-PbO2, reform from the gel phase during charging, and their proportions depend on the specifics of the charging process and the material state. Consequently, the relative amounts and distribution of α and β crystalline zones play a crucial role in influencing the overall performance of LABs.In the present investigation, we propose, for the first time, an ex situ NT investigation of intact PPs, endeavouring to assess the internal structure of the PAM (pore formation) and spine/PAM decohesion of real battery electrodes – fabricated with two alternative metallurgical methods (punching P and gravity casting G) – subjected to harsh electrochemical testing conditions, representative of recharge abuse. Our study is complemented by X-ray radiography - aimed at pinpointing spine and PAM cracking – and cross-sectional SEM imaging aimed at disclosing details with spine/PAM interface: grid shape variation, corrosion depth, mode and mechanism, corrosion layer nature and thickness.The synergic effect of these measurments enable a complete understanding and tracking of the PPs degradation mechanism : (i) NT offered a 3D quantitative and qualitative assessment of PAM porosity ,spine/PAM decohesions, and highly attenuating regions. Aging led to pore growth, with G electrodes displaying more extensive cracking. Variations in porosity distribution between P and G electrodes is observed. Hydrogenated gel distribution differed between electrode types and with aging. (ii) XR provided a non-destructive grid-scale overview. P electrodes exhibited limited defects, while G electrodes showed extensive spine issues. Corrosion progression differed from local SEM observations (iii) in which corrosion is explored at the spine/PAM interface, revealing no clear correlation between current density and corrosion. Representative micrographs for P and G electrodes were shared.The combination of these technique enable a complete characterization of positive plate degradation,.The methodical use of NT holds the potential to establish a comprehensive morpho chemical knowledge base for comprehending the manufacturing and aging processes of lead-acid battery electrodes directly visualization of the 3D arrangement of the hydrogen-containing electroactive amorphous phase, is a crucial metric for assessing the state of health (SOH) that is typically challenging to access experimentally This approach, coupled with in operando capabilities, relies on the quantitative examination of functionally significant features and their changes throughout the aging process. Figure 1

Electrochemical Analysis Comparison of Nitrogen Undoped and Doped Ti3C2Tx/Co3O4 Hybrid Composites on Carbon Cloth for Application as Electrode in Supercapacitor

Supercapacitor provides great potential for good energy storage devices application, compared with other energy storage such as rechargeable batteries, fuel cell, dielectric capacitors and so on. Freestanding and flexible electrodes are vital for the development of flexible and wearable devices that store energy. But the significant trade-off between mechanical flexibility and electrode electrochemical performance limits the fabrication of efficient energy storage systems. In this research, we report the synthesis of a 2D material Ti3C2Tx and Co NPs on carbon cloth (CC) substrate. Co NPs was synthesized by microplasma reactors which eliminate harmful reducing agents and are efficient and cost-effective. And the Co NPs/Ti3C2Tx were synthesized by hydrothermal method for supercapacitor. These materials were characterized by scanning electron microscopy (SEM) Energy Dispersive Spectroscopy and X-Ray Diffraction for morphology and phases analysis. Besides these Transmission electron microscopies (TEM) and X-ray Photoelectron spectroscopy (XPS) were also done. For electrochemical analysis these materials were applied on the 2.25 cm2 carbon cloth as active material (working electrode) by various electrochemical techniques in 1 M H2SO4 electrolyte. The Co NPs/Ti3C2Tx electrode had a maximum gravimetric capacity of 52 mAh g-1, specific capacitance of 580 mF cm-2 and 240 F g-1 at the current density of 1 mA cm-2. Figure 1

(Invited) Electrochemical Random Access Memory for Neuromorphic Computing

Electrochemical random access memory (ECRAM) is a three terminal device that functions by tuning electronic conductance in functional materials through solid-state electrochemical redox reactions, and is one of several emerging device concepts that are currently being investigated in academic and industrial laboratories for enabling energy efficient brain inspired computing. Early demonstrations of nearly ideal analog switching and the realization that electrochemical ion insertion can be used to tune the electronic properties of many types of materials including transition metal oxides, layered 2D material, organic and coordination polymers, has sparked tremendous interest in ECRAM. Depending on the specific material, the resulting changes in conduction can range from gradual increments needed for analog elements, to large, abrupt changes for dynamically reconfigurable adaptive architectures. At its core, ECRAM shares many fundamental aspects with rechargeable batteries, where ion insertion materials are used extensively for their ability to reversibly store charge and energy. Computing applications, however, present drastically different requirements: systems will require many millions of devices, scaled down to less than 100 nanometers, all while achieving reliable electronic-state tuning at scaled-up rates (~109 Hz) and endurances (>1012 cycles), and with minimal energy dissipation and noise. In my presentation, I will briefly cover the history of ECRAM, the recent progress in devices spanning various types of materials, circuits, architectures, and discuss the rich portfolio of challenging, fundamental questions and how we can harness ECRAM to realize a new paradigm for low power neuromorphic computing.

(Invited) Self-Discharge of Layered Oxide Cathodes Induced by Carbonate-Mediated Hydrogenation

Significant efforts have been made to improve the energy and power characteristics of cathodes in Li-ion batteries, while the research into cathode self-discharge has lagged behind. Self-discharge is the voltage drop experienced by all rechargeable batteries while stored in the charged state. The voltage drop becomes more problematic with increased cathode voltage and temperature. The physicochemical nature of internal reactions leading to cathode self-discharge is hardly understood and seldom discussed.To tackle this challenge, the structure and redox evolution of commercial LiNi0.5Mn0.3Co0.2O2 electrodes and single crystal cathode thin films upon the self-discharge in carbonate-based electrolyte is revealed by surface-sensitive X-ray scattering, spectrometric and electrochemical characterizations in conjunction with thermodynamic analysis. As evidenced by the interfacial toolkits and theoretical calculations, there is an evolution and growth of cathode surface reduction layer in different types of electrolyte after self-discharged from different potentials. Structural and chemical chacterizations as well as the elemental depth profiles within cathode thin film confirms proton-insertion-induced layered cathode hydrogenation. Calculation shows that such process is both thermodynamically and kinetically favorable and is triggered by the interfacial hydrogen atom abstraction of methylene group in carbonate solvent on delithiated cathode surface. A combination of experimental and theoretical studies reveals the carbonate-mediated cathode hydrogenation mechanism accounting for the voltage drop in the self-discharge. This offers additional understanding regarding defect generation and the degradation mechanism in layered cathodes beyond the traditional behaviors of lithium-diffusion-induced self-discharge and rock-salt phase induced cathode degradation. This study offers foundational knowledge of the interfacial degradation of cathode that can be translated to the rational design of improved cathodes and electrolytes, and the self-discharge mechanism studies in other electrochemical ion insertion materials and devices.

Ionblox’s SiOx-Based, High-Energy, High-Power Li-Ion Battery for Performance Electric Vehicles and Electric Aviation

Demands on land-based, high-performance electric vehicles (EVs) and electric aviation, by means of electric conventional takeoff and landing aircraft (eCTOLs) and electric vertical takeoff and landing aircraft (eVTOLs) demand more on a secondary cell chemistry than ever before. There are many secondary cells on the market that offer energy density, power density, fast-charge capability, or cycle life, but few, if any other manufacturing-ready cells, offer a combination of all four. IONBLOX has solved this by pairing it’s patented, Pre-lithiated SiOx anode with a high nickel, NMC cathode to produce cells exceeding 330 wh/kg. Herein we describe the performance of our 32 Ah cell, featuring high-energy density, high-power density, extreme fast charge capability, and good cycle life, within a package that is already in production.In particular, challenges for the eVTOL market will be addressed, which require peak power demand on the cell at low state-of-charge, without reducing the energy density. Methods for characterizing cells for such high-power applications will be further explored. DCIR pulse characterization and more customized testing like usable energy testing, which is important for identifying the applicable energy density for high-power use cases, will be demonstrated. Additionally, extreme fast charge capability is described on our large format cells with 5 min charge to >60% total cell capacity, over 1000 cycles. This shows such a cell is up to the expectations of a consumer familiar with the timing of a standard gasoline pump. Contribution from the information presented herein demonstrates the state of Si-based anode chemistry and can serve as useful guidelines to the academic community as future technologies are pursued for similar applications Figure 1

Optimizing Mid-Temperature Sodium Iodine Batteries for Sustainable Large-Scale Energy Storage: A Comprehensive Modeling Approach and Experimental Validation

The need for safe, eco-friendly, low-cost batteries for large scale implementation rises in the presence of the expansions of renewable energy sources. High-temperature liquid sodium batteries (e.g. sodium-sulfur) are a well-established technology for large-scale grid storage. Combining the molten sodium anode with an aqueous iodine cathode overcomes the problems of thermal loses and sealing by reducing the operating temperature to about 100°C. This leads to higher cost efficiency, energy density and a simplified cell design.Here we present a novel modelling approach for complex carbon-based cathode structures and its limits and abilities on enhancing the utilizable capacity. Due to their sustainability and high efficiency, which is comparable to Li-Ion –batteries, mid-temperature sodium-iodine batteries are a promising candidate for stationary energy storage applications. With a high specific energy of around 200 Wh kg-1, sodium-iodine batteries have the ability to meet the growing demand of short-term energy storage caused by the integration of renewable energy sources into the power grid. Up to this day, the detailed processes inside the battery are not well-understood. Quantities like initial species concentrations, C-rate, cell design and cathode geometry have large impacts on the overall battery performance. A deeper understanding of these processes is inevitable for enhancing the battery performance by choosing the optimal abovementioned quantities. We set up a fully resolved 3D Simulation model to gain insight into microstructural processes inside the battery, as experimental studies are limited to macroscopic quantities like electronic current and potential. The methodology is based on continuum hypothesis by using an open-source CFD software, which is rewritten accordingly. The proposed spatially resolved three-dimensional simulation model takes charge and mass transport, heterogeneous and homogeneous reactions as well as the electrochemical processes into account. Results show that transport limitations confine the utilizable capacity of the battery [1].This contribution focuses on enhancing the battery energy density and efficiency by including open-pored glassy carbon foam structures in the cathode half-cell [2, 3]. We state simulation predicted, optimal morphology properties of such a structure. Furthermore, we describe the evaluation of improved thermodynamic data of the aqueous iodine solution by refitting simulation results to polarization curves. We utilize a novel impedance spectroscopy simulation method for sodium iodine batteries to improve parameterization of the underlying electrochemical model by comparing the results with experimental data. References Gerbig, F., Cernak, S., Nirschl, H. (2021). 3D Simulation of Cell Design Influences on Sodium–Iodine Battery Performance. Energy Technology, vol. 9, no. 6, p. 2000857Gerbig, F., Cernak, S. and Nirschl H. (2021), Towards a Novel Sodium-Iodine Battery with an Aqueous Catholyte: Numerical Investigations of Complex Cathode Structures, ECS Trans., vol. 104, no. 1, pp. 123–130Gerbig, M. Holzapfel, and H. Nirschl, Simulating the Impact of Glassy Carbon Foam Electrodes on the Performance of Sodium Iodine Batteries, J. Electrochem. Soc., vol. 170, no. 4, p. 40517, 2023, doi: 10.1149/1945-7111/accab7. Figure 1

Advancing Low-Cost Iron Redox Flow Batteries for Grid Storage

Iron-based redox flow batteries are promising and low-cost energy storage technologies for grid level showing the potential to meet DOE’s cost targets LCOS, $0.05/kWh due to its natural abundancy and eco friendliness. Iron deposition process has a parasitic hydrogen evaluation reaction (HER) controlling the storage capacity and efficiency. HER reaction imbalances the electrolyte composition and causes durability issues. Our present study shows how the performance of the iron flow battery can be increased by introducing advanced 3D electrodes and engineered electrolytes.This work was performed under the auspices of the U.S. Department of Energy by Lawrence Livermore National Laboratory under Contract DE-AC52-07NA27344. Funding was provided by Lawrence Livermore National Laboratory Directed Research and Development (LDRD) Grant 22-DR-014. IM release number: LLNL-ABS-858432

(Battery Student Slam 8 Award Winner) A Simple and Fast Method to Assemble Flexible and Stable Quasi-Solid-State Zn Ion Pouch Cell

Aqueous zinc-ion batteries (AZIBs) have been investigated intensively as effective energy storage devices that are environmentally friendly, safe, and have a lower cost than current Li-ion batteries.[1-5] Being outstandingly safe due to usage of non-organic electrolyte, AZIBs could also be used as power supply for wearable electronics. This also put high standard requirements in terms of flexibility, stability and electrochemical performance to AZIBs. On the other hand, the general challenges, such as the formation of the dendrites on the Zn anodes, hydrogen evolution and side reactions, have been obstructing the practical application of AZIBs. In this presentation, a simple method to assemble quasi-solid-state Zn ion pouch cell with excellent mechanical performance, flexibility and electrochemical performance was developed, combining in-situ electrodeposition of MnO2 cathode and aramid nano fiber-based hydrogel with Zn plate as anode. In-situ and cycling measurements of the electrodeposition of MnO2 on carbon nanotube mat shows excellent capacitance and superior cycling stability. In addition, Kevlar derivatized aramid nanofiber-based hydrogel shows extremely strong strength when combined with polyvinyl alcohol, which prolonged the lifetime of the cell by preventing Zn dendrite growth largely.[5,6] Moreover, the method to assemble the AZIBs pouch cell enables us to optimize the process, decrease the steps, and save time effectively by taking advantage of hydrogel formation stage and avoiding conventional verbose slurry-casting-drying steps. This work paves an efficient path to assemble flexible and stable AZIBs pouch cells with high capacity and cycling stability.[1] Tang, Boya, et al. "Issues and opportunities facing aqueous zinc-ion batteries." Energy & Environmental Science 12.11 (2019): 3288-3304.[2] Li, Chang, et al. "Toward practical aqueous zinc-ion batteries for electrochemical energy storage." Joule 6.8 (2022): 1733-1738.[3] Yu, Feng, et al. "An aqueous rechargeable zinc-ion battery on basis of an organic pigment." Rare Metals 41.7 (2022): 2230-2236.[4] Lin, Yuexing, et al. "Dendrite-free Zn anode enabled by anionic surfactant-induced horizontal growth for highly-stable aqueous Zn-ion pouch cells." Energy & Environmental Science 16.2 (2023): 687-697.[5] Wang, Peng, and Petru Andrei. "High Performance Separator and Hydrogel Based on Aramid Fibers for Zn Ion Batteries." Electrochemical Society Meeting s 242. No. 4. The Electrochemical Society, Inc., 2022.[6] Xu, Lizhi, et al. "Water‐rich biomimetic composites with abiotic self‐organizing nanofiber network." Advanced Materials 30.1 (2018): 1703343.

Scalable One-Pot Synthesis of Nanostructured P2-Type Na2/3Ni1/3Mn2/3O2 Cathode Material for High-Performance Na-Ion Batteries

Sodium-ion batteries (SIBs) based on sodium transition metal oxides are considered as a viable alternative to lithium-ion batteries (LIBs) for grid-scale energy storage. This is because the critical elements used in these SIBs, such as sodium, manganese, and nickel, are abundantly available, and their supply chain does not pose any geopolitical risk like lithium and cobalt used in common LIB cathodes.1 Among sodium transition metal oxide cathodes, the P2-type Na2/3[Ni1/3Mn2/3]O2 (NNMO) is a promising material due to its high operating voltage (up to 4.5 V vs Na/Na+) and high capacity. When cycled between 2-4.5 V vs Na/Na+, it has a capacity of 173 mAh/g.2 This combination of high operating voltage and high capacity allows NNMO to outperform common LIBs in terms of energy density. Therefore, SIBs based on NNMO cathode are a scalable alternative to LIBs.Unfortunately, the current method used to produce NNMO through solid-state conversion is a time and energy-intensive process. It requires a temperature above 800 degrees Celsius and takes at least 12 hours to make a single batch of NNMO. Moreover, NNMO formed using this method has large particle sizes of a few micrometers. In my presentation, I will introduce a new and highly scalable method for synthesizing NNMO. This method can create NNMO in less than 20 minutes, which is much faster than the usual 12+ hours required by existing methods. Additionally, our protocol produces Nano-NNMO particles with size in the sub-200 nm. Nanoscale NNMO is crucial because it enhances the electrochemical performance of the materials, which I will also discuss. Key words: Sodium-ion batteries, Na2/3[Ni1/3Mn2/3]O2, high capacity, nanoparticles, rapid synthesis. References (1) Wang, C.; Liu, L.; Zhao, S.; Liu, Y.; Yang, Y.; Yu, H.; Lee, S.; Lee, G.-H.; Kang, Y.-M.; Liu, R.; et al. Tuning local chemistry of P2 layered-oxide cathode for high energy and long cycles of sodium-ion battery. Nature Communications 2021, 12 (1), 2256. DOI: 10.1038/s41467-021-22523-3.(2) Zhang, J.; Wang, W.; Wang, W.; Wang, S.; Li, B. Comprehensive Review of P2-Type Na2/3Ni1/3Mn2/3O2, a Potential Cathode for Practical Application of Na-Ion Batteries. ACS Applied Materials & Interfaces 2019, 11 (25), 22051-22066. DOI: 10.1021/acsami.9b03937.

Proton Activity and Pathway in Aqueous Organic Redox Flow Battery Electrolyte

Aqueous soluble organic (ASO) redox-active materials have recently shown great promise as alternatives to transition metal ions employed as energy-bearing active materials in redox flow batteries for large-scale energy storage because of their structural tunability, cost-effectiveness, availability, and safety features. However, development so far has been limited to a small palette of organics that are aqueous soluble. This presentation will use fluorenone as an example to showcase how a natively redox-inactive molecule can be tuned to possess two-electron redox reversibility through hydrogenation and dehydrogenation. The modified fluorenone molecules demonstrated high energy density and recorded stable cycling. Furthermore, research has shown the unique chemical-electrochemical coupled redox reactions mechanism; thus, the system rate capabilities can be improved by incorporating suitable hydrogen acceptors that regulate the proton pathway for faster kinetics.Reference:Feng et al., Science 372, 836–840, 2021Feng et al., Joule 7, 1–14, 2023

High-Rate and Durable Zinc-Based Flow Batteries for Large-Scale Energy Storage

Large-scale energy storage is a key enabling technology for the widespread adoption of renewable energy such as wind and solar power. Among various technologies, zinc-based flow batteries stand out as one of the most promising candidates due to the high energy density, low cost, and use of earth-abundant active materials. However, the low operating current density and short cycle life resulting from notorious zinc dendrite formation, large internal resistance, and sluggish reaction kinetics pose a great challenge for their practical applications. Although great efforts have been made to address these issues, previous works mainly focused on one specific aspect, making it challenging to boost the overall performance of zinc-based flow batteries. In this presentation, a systematic study on the effects of key components on the electrochemical performance of zinc-bromine flow batteries will be presented. Our results show that all key components (electrodes, electrolytes, membranes, and flow fields) can exert a significant influence on the electrochemical performance. More impressively, a high areal capacity of >200 mAh/cm2 and an operating current density of as high as 400 mA/cm2 can be achieved by optimizing the design and operating parameters. Underlying mechanisms and perspectives for further improvement will be discussed during the presentation.

(Invited) Towards Rechargeable Zn/CuO Batteries for Grid-Scale Storage

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 a Zn anode 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 10% of 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. Optimization studies performed for Bismuth content indicate that changes in Bi2O3 concentration can impact the charge-discharge behavior of the CuO cathodes resulting in the suppression of metal hydroxide-related redox peaks on charge. The absence of these peaks correlates with improved cyclability, suggesting that methods and materials approaches to further suppress these recharge pathways may lead to CuO high-capacity cathodes with improved cycle-life in the future.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 also affect the battery cycling mechanism and may have future roles of 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, polymer gel electrolytes and ion selective polymers in enabling reversible Cu-based cathodes. The general challenges of achieving a highly reversible energy dense battery based on two conversion electrodes operating in highly alkaline environment will be covered as will development towards a > 200 Wh/L industrially relevant Zn/CuO battery.This work was supported by the U.S. Department of Energy Office of Electricity. This work was performed, in part, at the Center for Integrated Nanotechnologies, an Office of Science User Facility operated for the U.S. Department of Energy (DOE) Office of Science. The views expressed in this article do not necessarily represent the views of the U.S. Department of Energy or the United States Government. This article has been co-authored by an employee of National Technology & Engineering Solutions of Sandia, LLC under Contract No. DE-NA0003525 with the U.S. Department of Energy (DOE). The employee owns all right, title and interest in their contribution to the article and is solely responsible for its contents. The United States Government retains and the publisher, by accepting the article for publication, acknowledges that the United States Government retains a non-exclusive, paid-up, irrevocable, world-wide license to publish or reproduce the published form of this article or allow others to do so, for United States Government purposes. The DOE will provide public access to these results of federally sponsored research in accordance with the DOE Public Access Plan.

(Invited) Innovating Sustainable, Cost-Effective, and Durable Redox Flow Battery Membranes

In the quest to integrate renewable energy sources like solar and wind into the electric grid efficiently, the development of long-duration energy storage (LDES) systems is paramount. The U.S. Department of Energy's Long Duration Storage Shot initiative is at the forefront of this endeavor, aiming to reduce the costs of grid-scale energy storage by 90% for systems with over 10 hours of operation. A key player in this mission is the non-aqueous redox flow battery (RFB), known for its use of earth-abundant materials and potential to meet these cost-reduction goals. However, the commercial viability of RFBs hinges on the development of high-performance, cost-effective membranes, which are crucial for their functionality and affordability. These membranes' ionic conductivity is vital for the power density of RFBs, while their ion selectivity and solvent uptake greatly influence the batteries' cycle life.Our team has made groundbreaking advancements in membrane technology for non-aqueous flow batteries. We've addressed the challenge of balancing ionic conductivity with mechanical strength in polymer electrolytes. Our findings reveal that enhanced solvent uptake while boosting membrane ionic conductivity, can compromise mechanical integrity. To counter this, we've employed two strategies: selective plasticization of the ion-conductive block in block copolymers and reinforcing the membrane's mechanical strength through hydrogen and ionic bonds with an inorganic scaffold. Significantly, we've also reduced the crossover of redox-active species in our membrane designs, notably decreasing polysulfide species crossover in a Na metal – polysulfide hybrid flow battery. This has led to improved capacity retention, Coulombic efficiency, and extended cycle life compared to traditional porous membranes.Our latest innovations include the development of hydrocarbon single-ion conductors, demonstrating enhanced conductivity and stability. We've also introduced crosslinking chemistry to control solvent uptake more effectively, thus improving ionic conductivity while preserving mechanical strength. Lastly, our pioneering tape casting method for producing ceramic-polymer composite membranes represents a major leap in scalable membrane production, paving the way for the practical application of non-aqueous redox flow batteries in long-duration energy storage. Acknowledgment This research was conducted at Oak Ridge National Laboratory, managed by UT Battelle, LLC, for the U.S. Department of Energy (DOE) and is sponsored by the U.S. Department of Energy through the Energy Storage Program in the Office of Electricity. We acknowledge Dr. Jagjit Nanda SLAC National Accelerator Laboratory for the fruitful discussions.

High-Voltage, Long Term-Stable and Wearable Zinc-Ion Hybrid Batteries with Gel Biopolymer Electrolytes

We are on the eve of the energy transition towards the phase-out of coal, electromobility and renewable power supply. Lithium-ion batteries (LIBs) and electric double-layer capacitors (EDLCs) are complementary energy storage devices supporting this technological change. They have dominated the commercial market of power sources, serving as energy supplies for various technologies ranging from daily electronics and gadgets through electric vehicles to management systems of the intermittent electric grid. However, conventional energy storage systems present some challenges regarding operational safety, the expected increase in production costs, the risk of limited availability of raw natural resources, and universal waste disposal.1,2 Zinc-ion rechargeable power sources, including batteries and hybrid supercapacitors, are a promising alternative to commercial LIBs and EDLCs.3,4 This technology integrates attractive features, such as high gravimetric and volumetric theoretical capacity, low cost, high safety, and environmental friendliness. Nevertheless, the widespread adoption of zinc-ion systems for powering commercial devices still faces challenges related to electrode design, the risk of liquid electrolyte leakage, rigid construction, and the presence of synthetic polymer-based components. This research attempts to address the aforementioned shortcomings by exploring the concept of biopolymer-based zinc-ion systems.Herein, we present zinc-ion hybrid batteries employing gel biopolymer electrolytes. Batteries and dual-ion hybrid batteries of aqueous Zn-ion technology operate according to similar mechanisms, differing on the catholyte side. In Zn-ion batteries, zinc ions are involved in the reactions on both electrodes, whereas hybrid systems have cathodes adopted from alkaline metal-ion technologies, operating according to intercalation/deintercalation processes of monovalent cations, e.g., Li-ion, Na-ion, K-ion, etc.5 As observed, hybrid devices are feasible with fast kinetics, good stability, and flat and high discharge voltage plateau. The application of gel electrolytes additionally improves their performance on the anode side, facilitating Zn stripping/plating processes due to homogeneous current distribution and flat Zn deposition. Generally, the presented idea emerges as a promising strategy, offering an efficient, safe, low-cost, non-combustive, flexible and sustainable technology. Particular attention is paid to overcoming LIB performance and environmental limitations whilst developing wearable features through innovative biobased technological improvements.References(1) Mauler, L.; Duffner, F.; Zeier, W. G.; Leker, J. Battery Cost Forecasting: A Review of Methods and Results with an Outlook to 2050. Energy Environ. Sci. 2021, 14 (9), 4712–4739.(2) Simon, P.; Gogotsi, Y.; Dunn, B. Where Do Batteries End and Supercapacitors Begin? Science (80-. ). 2014, 343, 1210–1211.(3) Wang, Y.; Sun, S.; Wu, X.; Liang, H.; Zhang, W. Status and Opportunities of Zinc Ion Hybrid Capacitors: Focus on Carbon Materials, Current Collectors, and Separators. Nano-Micro Lett. 2023, 15 (1), 78.(4) Tang, B.; Shan, L.; Liang, S.; Zhou, J. Issues and Opportunities Facing Aqueous Zinc-Ion Batteries. Energy Environ. Sci. 2019, 12 (11), 3288–3304.(5) Shi, Y.; Chen, Y.; Shi, L.; Wang, K.; Wang, B.; Li, L.; Ma, Y.; Li, Y.; Sun, Z.; Ali, W.; Ding, S. An Overview and Future Perspectives of Rechargeable Zinc Batteries. Small 2020, 16 (23), 2000730. Figure 1. Work concept. Figure 1

Morphology Controled LiFePO4 Electrodes Via Polyol Refluxing for Enhanced Lithium-Ion Battery Performance

In the synthesis of LiFePO4 cathodes with secondary nanorod structures and nano-plate morphologies, researchers utilized a polyol refluxing process. Notably, we achieved this without the use of characteristic structure directing agents. Through varying the reaction time, they were able to modulate the morphological characteristics of the synthesized samples.X-ray diffraction studies conducted on the prepared samples indicated a highly crystalline nature. This suggests that the synthesized cathodes possessed a robust and ordered atomic structure, which is crucial for their electrochemical performance.Electron microscopy investigations provided insights into the morphology of the samples obtained at different reaction times. Samples produced after 1 to 16 hours of polyol reaction exhibited secondary nanorod bundles. However, the sample recovered after 32 hours of polyol reaction displayed a distinct nano-plate morphology. These observations highlight the influence of reaction time on the final morphology of the synthesized cathodes.The dimensions of the obtained samples ranged from a few tens to a few hundred nanometers. This nano-scale size is advantageous for enhancing the electrode's surface area, which can facilitate rapid ion diffusion and electron transport during battery cycling.When employed in lithium test cells, the LiFePO4 cathodes synthesized for different durations delivered varying discharge capacities. Specifically, cathodes prepared under 1, 4, 8, 16, and 32 hours of reaction time exhibited discharge capacities of 161, 162, 171, 143, and 155 mAhg−1, respectively. Notably, all samples displayed a well-defined discharge plateau at 3.4 V, indicating stable electrochemical behavior during cycling.Remarkably, among the prepared electrodes, the LiFePO4 nanorod bundle cathode synthesized under 1 hour reaction time demonstrated the highest average reversible capacities. It maintained capacities of 123 and 103 mAhg−1 at C-rates as high as 3.2 and 6.4 C, respectively. This highlights the importance of reaction time in controlling the electrochemical performance of the synthesized cathodes.The crystal growth mechanism during the polyol refluxing method can be elucidated through several stages. These include precursor dissolution and nucleation, oriented crystal growth and alignment through self-assembly, aggregation, partial dissolution, and finally, complete re-crystallization. Understanding these mechanisms is essential for optimizing the synthesis process and tailoring the properties of LiFePO4 cathodes for various applications. Tarascon JM, Armand M. Issues and challenges facing rechargeable lithium batteries. Nature 2001;414:359–67Amatucci GG, Tarascon JM, Klein LC. CoO2, the end member of the LixCoO2 solid solution. J Electrochem Soc 1996;143:1114–23Ravet N, Chouinard Y, Magnan JF, Besner S, Gauthier M, Armand M. Electroactivity of natural and synthetic triphylite. J Power Sources 2001;97–98:503–7 Figure 1

(Invited) Transport Limits for Zinc Aqueous Electrolyte Batteries: Investigation over Multiple Length Scales

Large scale grid level storage would benefit from low cost environmentally sustainable batteries. A system class under investigation is rechargeable zinc anode batteries utilizing aqueous electrolytes. These systems hold promise due to their potential for safe low-cost scalable energy storage. Consideration of the systems over various length scales is warranted due to the complexity of the possible reactions and pernicious parasitic processes. Further, the diversity and intricacies of these battery systems inherently reduce the probability of optimization experiments alone resulting in marketable products.Many of the fundamental issues influencing ion and electron transport and electron transfer and how the transport phenomena evolve under flux are not yet fully undefined. More complete understanding demands multiple characterization approaches used in concert, to tie together information gathered at the local or atomic level and the mesoscale with systems level performance from electrochemical impedance spectroscopy (EIS), galvanostatic cycling (GC), and related techniques. This presentation will provide insight into probes of the reaction mechanisms, evolution of zinc interfaces, methods to determine limitations of cathode function at high rate, and impact of the findings on the electrochemical behavior of the batteries.

Microstructure Characterizations of Electrodeposited Magnesium after Discharge/Charge Cycles for Rechargeable Magnesium Battery

Rechargeable magnesium (Mg) batteries attract lots of attention owing to their high theoretical volumetric energy density and low cost from the natural abundance of Mg. Additionally, Mg is less prone to dendrite growth during charging, improving the battery safety. While most studies of rechargeable Mg batteries focus on developing new electrolytes and their performances, the microstructure of the Mg metal anodes during discharge/charge cycles is not fully characterized. Therefore, in this report, we investigated the microstructure evolution of electrodeposited Mg after discharge/charge cycles on both a bulk Mg metal anode and a copper (Cu) current collector in an all phenyl complex (APC) electrolyte.The electrodeposited Mg on both the Mg anode and the Cu current collector at a current density of 2.25 mA/cm2 with a capacity of 1.5 mAh/cm2 show uniform distributions of Mg grains with an average grain size of about 1 to 2 μm. Subsequent Mg stripping with intermediate current density (0.75 mA/cm2) results in non-uniform discharge holes and possible local exposure of the substrate underneath, which could deteriorate the anode integrity. In contrast, the stripped electrodeposited Mg at relatively large (2.25 mA/cm2) and small (0.25 mA/cm2) discharge current densities show dense and uniform discharged holes on the surface. The microstructure evolution of the electrodeposited Mg on different substrates will be discussed based on the plating/stripping overpotentials and the interfacial impedances of the electrodeposited Mg under different conditions.

Refining Mn(III) Active Sites in MnO2-Based Self-Assembled Electrodes Via Oxygen Vacancy Induction to Enhance Oxygen Reaction Performance in Zinc-Air Batteries

Rechargeable zinc-air batteries are considered as a promising candidate for next-generation electrochemical energy conversion devices due to their safety, low cost, and high theoretical capacity/ energy density. Over the past few decades, α-MnO2-based electrodes have demonstrated their excellent performance and competitiveness in oxygen catalytic reactions. (1) According to eg filling theory, Mn(III) (t2g3eg1) sites in [MnO6] octahedral unit deliver superior bifunctional activity compared to Mn(II) (t2g3eg2) and Mn(IV) (t2g3eg0) sites.(2) However, the presence of unpaired single electrons of the Mn(III) site leads to low thermodynamic stability. Introducing oxygen vacancies to promote the electron rearrangement of the [MnO6] unit is a promising approach for enhancing the durability of Mn(III) active sites. Herein, we construct an oxygen-vacancy-enhanced MnO2-based electrode via a self-assembly process (NiCo2O4-MnO2@Ni foam). The intrinsic oxygen catalytic activity of NiCo2O4-MnO2@Ni foam is significantly improved by forming abundant highly stable Mn(III) active sites, which accelerate the mass transfer ability. As expected, the NiCo2O4-MnO2@Ni foam shows good bifunctional activity with a low overpotential of 0.69 V. The zinc-air battery assembled by NiCo2O4-MnO2@Ni foam exhibits a high peak power density of 576 mW cm-2, surpassing that of the Pt/C-Ir/C electrode. Additionally, benefiting from its stable flower-shaped hierarchical structure, the self-assembled electrode demonstrates long-term charge-discharge cycling stability, which lasts over 800 hours. This work provides innovative insights into enhancing MnO2-based electrodes by oxygen vacancy introduction.References N. Xu, Q. Nie, L. Luo, C. Z. Yao, Q. Gong, Y. Liu, X. Zhou, and J. Qiao, ACS applied materials & interfaces (2018).Z. Yin, R. He, H. Xue, J.-M. Chen, Y. Wang, X. Ye, N. Xu, J. Qiao and H. Huang, Energy Materials (2022).

(General Student Poster Award Winner, 3rd Place) Lithium Niobate Coatings on Lithium Iron Phosphate Cathode Materials for Applications in Lithium-Ion Batteries

Lithium-ion batteries have become a crucial tool in countering global fossil fuel reliance; when paired with electric motors, they provide an alternative to petroleum-based energy storage for internal combustion engines. Typical cathode materials used in lithium-ion batteries present a unique set of challenges. Some of the electrochemical materials that have a relatively high performance also have serious impacts on the environment and human health.1 Other materials that lack these specific drawbacks, such as lithium iron phosphate (LFP), face other issues. For example, LFP suffers from a relatively low electrical conductivity and a relatively slow lithium-ion diffusion, both of which affect the general electrochemical performance of this material. These weaknesses can be addressed using coatings applied to LFP nanoparticles. Carbon coatings have already been shown to improve the performance of LFP nanoparticles, but materials with higher ionic conductivities have remained relatively undeveloped.2 By synthesizing a composite coating of both carbon and lithium niobate, further improvements to LFP nanoparticles were sought to enable a wider range of applications for this cathode material.In this work, lithium niobate coatings on carbon coated LFP nanoparticles were synthesized using a low temperature solvothermal method. Lithium niobate coatings have been shown to improve the specific capacity, rate capability, and durability of other cathode materials for lithium-ion batteries.3 Half-cells were fabricated to examine the effect of adding a lithium niobate coating to the carbon coated LFP cathode materials. Electrochemical testing techniques such as galvanostatic cycling and cyclic voltammetry were used to compare the properties and performance of the composite coated LFP relative to the carbon coated LFP. The composite coatings were also characterized using transmission electron microscopy, energy dispersive spectroscopy, and X-ray photoelectron spectroscopy. This coating method has resulted in the successful synthesis of lithium niobate coatings on carbon coated LFP nanoparticles with an observed improvement in durability. Goodenough, J. B.; Kim, Y. Challenges for Rechargeable Li Batteries. Mater. 2010, 22 (3), 587–603.Wang, J.; Sun, X. Understanding and Recent Development of Carbon Coating on LiFePO4 Cathode Materials for Lithium-Ion Batteries. Energy Environ. Sci. 2012, 5 (1), 5163–5185.Kim, J. H.; Kim, H.; Choi, W.; Park, M.-S. Bifunctional Surface Coating of LiNbO3 on High-Ni Layered Cathode Materials for Lithium-Ion Batteries. ACS Appl. Mater. Interfaces 2020, 12 (31), 35098–35104.

Manganese Oxide Gas Diffusion Electrode Conditioning and Electrochemical Doping for Reversible Oxygen Reduction/Evolution Reactions

Developing durable and active bifunctional gas diffusion electrodes for reversible oxygen reduction/evolution (ORR/OER) reaction catalysis is crucial yet challenging in the development of numerous electrochemical energy conversion systems, including regenerative fuel cells and rechargeable metal-air batteries. This research is focused on developing manganese oxide-based gas diffusion electrodes for reversible oxygen electrodes.Core-porous shell Mn/Mn3O4 (abbreviated as MnOx) nanoparticles (QSI) demonstrated increased ORR/OER activities compared to γ-MnO2 (EMD) and b-MnO2.[1] The unique behaviour of core-shell MnOx is attributed to the charge transfer between the low-valent Mn core and the high-valent Mn3O4 shell, thereby regenerating Mn(III) active sites through comproportionation.[1]The stability of transition-metal-based reversible oxygen electrodes remains a challenge. As shown in Figure 1, the deterioration of Mn/Mn3O4 during ORR and OER cycling can be attributed to three aspects: Mn active sites oxidation (Figure 1a), less active MnOx phase formation (Figure 1b), and material loss (carbon corrosion and dissolved MnO4 - formation) (Figure 1c).[2] As a result, the QSI MnOx electrode transformed from pristine to inactive status within 15 galvanostatic ORR/OER cycles. To improve the stability of the electrode, a set of in-situ electrochemical conditioning and electric field-driven metallic cation incorporation into MnOx GDE was investigated. Among the explored metal cations, the Ni2+ incorporation showed the most significant improvement in terms of activity and cyclic stability. The Ni-MnOx GDE demonstrated excellent stability for over 120 galvanostatic cycles at ±10 mA cm-2 in O2-saturated KOH without losing OER activity, surpassing the Pt/C-IrO2 benchmark.[3]These findings position the MnOx electrodes as promising and sustainable alternatives to precious metal-based electrodes for ORR/OER catalysis and provide valuable insights into designing reversible oxygen electrodes for energy conversion and storage in alkaline systems, contributing to a green future.[1] Pei, Y., Wilkinson, D. P., & Gyenge, E. L. Insights into the electrochemical behavior of manganese oxides as catalysts for the oxygen reduction and evolution reactions: monometallic core‐shell Mn/Mn3O4. Small, 2023, 19, 2204585.[2] Pei, Y., Wilkinson, D. P., & Gyenge, E. L. Gas Diffusion Electrode Design and Conditioning with Manganese (III/IV) Oxide Catalyst for Reversible Oxygen Reduction/Evolution Reactions. ACS Energy & Fuels (2023), 37, 23, 19278–19291.[3] Pei, Y., Wu, W. Y., Wilkinson, D. P., & Gyenge, E. L. High-Performance Reversible Oxygen Reduction/Evolution Gas Diffusion Electrodes with Multivalent Cation Doped Core-Shell Mn/Mn3O4 Catalysts. ChemElectroChem, in press. Figure 1