Large-scale Energy Storage Systems Research Articles

Experimental heat transfer study of an enhanced storage medium

Phase change materials (PCMs) are suitable for storing solar energy due to their high-density energy storage and ability to operate in a wide range of temperatures. However, the lower thermophysical properties of PCMs limit their use in solar energy storage applications. Therefore, the incorporation of nanoparticles has emerged as a promising technique to enhance the storage density of PCMs.Extensive studies have been conducted on the measurement of thermophysical properties of both PCMs and nano-PCMs (PCMs with nanoparticles dispersed in them). However, there has been no comprehensive study covering the following aspects: (a) the measurement of thermophysical properties of NaNO3 (PCM) and nano-NaNO3 (nano-PCM), (b) solar energy storage of NaNO3 involving both sensible heat and latent heat in the same study, (c) the construction and implementation of an experimental rig capable of studying heat transfer in PCM and nano-PCM for solar energy storage applications (with a maximum temperature of up to 350 °C), and (d) investigating the effect of nanoparticles on large-scale solar energy storage systems. Therefore, the aim of this study is to experimentally investigate all of the aforementioned points. In order to develop and test these solar storage mediums, an experimental setup has been designed and manufactured, as mentioned earlier.Furthermore, limited studies have considered sodium nitrate salt (NaNO3) as a PCM. In this study, NaNO3 is used as the base material, and two types of materials are considered: PCM1, which consists of sodium nitrate salt (NaNO3), and PCM2, which consists of sodium nitrate salt (NaNO3) with 0.75 wt% iron oxide nanoparticles (Fe2O3) added. The experiments conducted involved both steady-state and transient conditions. The results showed that the addition of nanoparticles improved the charging and discharging by 25.6 % and 23.929 %, respectively. Moreover, the specific heat capacity and latent heat of the developed PCMs increased by 17.857 % and 9.97 %, respectively. These findings suggest that PCM2, with the presence of nanoparticles, melts and discharges energy faster compared to PCM1. Overall, this study contributes to the understanding of solar energy storage using PCMs and nano-PCMs, highlighting the potential benefits of nanoparticle incorporation in enhancing their performance.

Hard carbons from automotive shredder residue (ASR) as potential anode active material for sodium ion battery

Graphite, the most prominent anode material for Li-ion battery, exhibited very poor performance in sodium ion battery. The electrochemical intercalation of Na+ ions in graphite is impeded due to smaller interlayer spacing. Here, we have reported ASR derived hard carbon as a suitable anode electroactive material for Na-ion battery. Prepared via single step selective thermal transformation, the hard carbons contain defects, heteroatoms, nanopore, and ordered carbon zones with expanded interlayer spacing. Among all the hard carbons, the hard carbon synthesised at 1100 °C, showed better electrochemical performance owing to its improved structural and morphological properties. The electrochemical study reveals that hard carbon synthesised at 1100 °C provides initial reversible capacity of 434mAh/g at a current density of 10 mA/g with a capacity retention of 53% after 100 cycles. Issues like global warming and climate changes have made human to shift their energy choices from fossil fuels to renewable sources. Although Li-ion battery is currently dominating the energy market, yet it falls short to meet the growing large scale energy storage system (EES) demand. Na-ion battery is considered as a worthy contender for growing ESS. The hard carbon studied in this work, can be a potential candidate for use as anode active material in Na-ion battery.

Large-scale energy storage system: safety and risk assessment

The International Renewable Energy Agency predicts that with current national policies, targets and energy plans, global renewable energy shares are expected to reach 36% and 3400 GWh of stationary energy storage by 2050. However, IRENA Energy Transformation Scenario forecasts that these targets should be at 61% and 9000 GWh to achieve net zero carbon emissions by 2050 and limit the global temperature rise within the twenty-first century to under 2 °C. Despite widely known hazards and safety design of grid-scale battery energy storage systems, there is a lack of established risk management schemes and models as compared to the chemical, aviation, nuclear and the petroleum industry. Incidents of battery storage facility fires and explosions are reported every year since 2018, resulting in human injuries, and millions of US dollars in loss of asset and operation. Traditional risk assessment practices such as ETA, FTA, FMEA, HAZOP and STPA are becoming inadequate for accident prevention and mitigation of complex energy power systems. This work describes an improved risk assessment approach for analyzing safety designs in the battery energy storage system incorporated in large-scale solar to improve accident prevention and mitigation, via incorporating probabilistic event tree and systems theoretic analysis. The causal factors and mitigation measures are presented. The risk assessment framework presented is expected to benefit the Energy Commission and Sustainable Energy Development Authority, and Department of Standards in determining safety engineering guidelines and protocols for future large-scale renewable energy projects. Stakeholders and Utility companies will benefit from improved safety and reliability by avoiding high-cost asset damages and downtimes due to accident events.

A highly reversible Zn anode enabled by organic/inorganic Bi-protective layer

Aqueous Zn-ion batteries (AZIBs) are regarded as one of the most promising large-scale energy storage system due to the merits of low cost and safety. However, uncontrolled Zn dendrite caused by uneven Zn2+ deposition on the surface of Zn anode is a serious challenge for the development of Zn anode. In this work, an organic/inorganic bi-protective layer is constructed on Zn electrodes and features an inorganic layer (MXene) at the bottom and a polymer layer sulfonated poly(ether ketone)(SPEEK) on the top. MXene is porous and conductive, which can diminish the local current density and have a shunting impact on Zn2+. SPEEK has good mechanical qualities to reduce the volume effect of Zn during charge/discharge procedure and avoid the direct contact among Zn and electrolyte. Therefore, the bi-protective layer SPEEK/MXene (SKME) can both limit side effects and decrease dendrite development. Therefore, the SKME@Zn electrode has extremely long plating/stripping cycling period of 1300 h at 0.5 mA cm−2. The SKME@Zn//V2O5 full batteries display higher cycle stability than the bare Zn//V2O5 and MXene@Zn//V2O5 systems, indicating that this organic/inorganic bi-protective layer has practical application prospects.

Research on Parallel Control Strategy of Grid-forming of Power Conversion System

A high proportion of power electronic equipment, distributed energy, and other new energy access to the grid system, low inertia and low damping to the power grid system, these kinds of power grid characteristics in power electric wire aging remote mountains or island areas, therefore, need energy storage system under the microgrid can provide inertial support for load or grid, improve the system damping characteristics. On this basis, the grid-forming control is proposed, so that the power conversion system can work under the off-grid, and can provide inertia and damping to maintain the system stability. In addition, large-scale energy storage systems often require multiple machines operating in parallel. In this paper, the topology of NPC for a power conversion system is studied and analyzed in off-grid mode.

A dynamic electrostatic shielding layer toward highly reversible Zn metal anode

Aqueous Zn-ion batteries (AZIBs) have gained considerable attention due to their inherent safety, cost-effectiveness, and environmental friendliness. However, their application in large-scale energy storage system is hindered by uncontrollable dendrite growth and severe side reactions at the electrode-electrolyte interface. To address these challenges, we propose the incorporation of trivalent yttrium (Y3+) ions in ZnSO4 electrolyte, which can form a cationic electrostatic shielding layer on the Zn anode to regulate the deposition behavior of Zn2+ ions. The inert Y3+ ions with a lower effective reduction potential will selectively adsorb on the active sites, facilitating uniform Zn deposition through a sustained dynamic electrostatic shielding effect. Moreover, the adsorbed Y3+ ions create a protective interface for the Zn anode, mitigating the corrosion reactions caused by water molecules. Consequently, the Zn//Zn cell with 0.1 M Y3+ ions demonstrates dendrite-free Zn plating/stripping over 2080 h at 5 mA cm−2, and the assembled Zn//NH4V4O10 cell delivers a high capacity retention of 89.6% after 2000 cycles at 5 A g−1. This work develops a new rare earth ion additive and confirms its sustained dynamic electrostatic shielding effect for dendrite-free Zn deposition, providing theoretical support and an exploration direction for further investigation of unexplored rare earth elements.

Quantum sensing of electric field distributions of liquid electrolytes with NV-centers in nanodiamonds

To use batteries as large-scale energy storage systems it is necessary to measure and understand their degradation in-situ and in-operando. As a battery’s degradation is often the result of molecular processes inside the electrolyte, a sensing platform which allows to measure the ions with a high spatial resolution is needed. Primary candidates for such a platform are NV-centers in diamonds. We propose to use a single NV-center to deduce the electric field distribution generated by the ions inside the electrolyte through microwave pulse sequences. We show that the electric field can be reconstructed with great accuracy by using a protocol which includes different variations of the free induction decay to obtain the mean electric field components and a pulse sequence consisting of three polarized π-pulses to measure the electric field’s standard deviation . From a semi-analytical ansatz we find that for a lithium ion battery there is a direct relationship between and the ionic concentration. Our results show that it is therefore possible to use NV-centers as sensors to measure both the electric field distribution and the local ionic concentration inside electrolytes.

Applications of energy storage systems in power grids with and without renewable energy integration — A comprehensive review

Energy storage system (ESS) is recognized as a fundamental technology for the power system to store electrical energy in several states and convert back the stored energy into electricity when required. Some excellent characteristics such as availability, versatility, flexible performance, fleet response time, modularity etc., make ESS more attractive for power system applications. The ESS has signification contributions and applications to operate the power system optimally in power grids with and without integrating renewable energy (RE) systems. This paper presents a comprehensive review of ESS technologies and their applications in power grids. Five different types of ESS, namely mechanical, chemical, electrical, electro-chemical and thermal, are elaborately explored with their key characteristics and applications. A summary of comparative analysis to find the appropriate ESS for power system applications and an analysis of the practical implementation of different ESS worldwide have been presented briefly, reflecting the suitability of ESS for power system applications. The comparative analysis further demonstrates the nature of various ESS, including their advantages and limitations in specific applications. The major challenges from these analyses are identified to be the capacity of ESS, RE integration, high maintenance and implementation cost of ESS, ESS degradation, waste management and associated environmental pollution. Moreover, the review finds out that there are still numerous challenges in terms of technology and economy that need to be addressed to make the practical applications of ESS viable for power industries. The reviews also identify recent key researches that can effectively address those issues and explore the future directions researchers can undertake to improve various characteristics of ESS. Finally, the transition pathway to promote ESS for power systems applications with and without integration of RE systems is discussed to demonstrate the possibility and potentiality of large-scale ESS deployment for a sustainable climate-friendly future.

Biopolymer-blended protective layer for use in stabilizing the zinc anode in metal battery applications

Metallic Zn anodes have recently attracted attention for use in large-scale energy storage systems; however, controlling the nucleation and growth behaviors of Zn is essential owing to its poor reversibility. In this study, we employed a protective layer (denoted XPpl) fabricated using xanthan gum and poly(ethylene oxide) (PEO). This layer exhibited a structured surface morphology and abundant oxygen-containing functional groups. When only glass fiber membrane (denoted GF) was used, Zn metal anodes polluted with dendritic Zn and broken fibers were observed after cycling. Upon introducing XPpl, dendrite-free Zn deposition was observed, and Zn metal was physically/chemically protected from the GF. An XPpl-protected ZnǁCu cell could undergo long-term operation for >5000 cycles at 2 mA cm−2. This study will provide insights into critical factors that affect Zn nucleation and growth, enabling accurate factor selection.

Usage of Co-Solvent for Fabricating the Composite Cathode for Sulfide-Based All-Solid-State Lithium Batteries

In recent decades, lithium-ion batteries (LIBs) have been widely used in electric vehicles and large-scale energy storage systems. However, current LIBs using the flammable organic electrolytes have a safety issue. Therefore, all-solid-state lithium batteries (ASSLBs) with enhanced safety and high energy density are in the spotlight. Among many solid electrolytes, sulfide-based solid electrolytes with high ion conductivity and ductile property are the most promising. In order to develop the ASSLBs, the composite cathode with high mass loading is imperative, which can be fabricated by the wet process suitable for mass production. Polar solvents can disperse a binder with polar groups well, but it may cause severe dissolution of sulfide solid electrolytes in the composite cathode. Therefore, we tried to use co-solvent that can disperse a polymer binder well and prevent the dissolution of sulfide solid electrolyte. Cycling performance of ASSLBs employing the wet-type composite cathode was evaluated and will be reported.

Voltage Differential Analysis during Power Discharge Operation in Energy Storage Systems

Constant Power Discharge (CPD) is a lucrative operating mode for grid-tied ESS in many energy markets. The CPD mode corresponds to an increasing current drawn as the ESS discharges. The operation can be modeled with an aged anode and cathode open circuit potentials (OCPn/p+RRC) model that can let us identify electrode-level (eSOH) parameters and resistance growth even though we do not have slow discharge with Constant Current. This identification process from realistic ESS field data, namely constant power discharge, will enable continuous eSOH diagnostics and lead to real-time and operando quantification of loss of active material and loss of lithium inventory (LAM and LLI, respectively).In addition, the timing of when the cell groups' differential voltage peaks occur when the battery system is under constant power operations inform us about the imbalance among cell groups in a module of a battery system, as shown in the figure. Using the time separation among cell differential voltage peaks as a metric of cell imbalance can improve cell balancing algorithms that measure cell imbalance using maximum or minimum voltage, which can be directly affected by the power limits of the battery system.The efficacy of the proposed algorithms is evaluated for multi-cell modules consisting of NMC/graphite cells, operating as part of a large-scale grid-connected energy storage system. Ultimately, by enabling improved diagnostics of the state of health of individual cells in a battery system and improved cell balancing algorithms, this work will enhance the performance and safety of large-scale lithium-ion battery systems. Figure 1

High Performance Zinc-Based Anodes for Aqueous Zinc Batteries

In the past thirty years, there has been significant development in the search for alternative energy sources such as secondary battery systems. Zinc (fourth-most mined material) has attracted much attention due to its abundance, low-cost, and recyclability. Moreover, as zinc-based batteries can be manufactured with aqueous-based electrolytes that benefits from many advantages of Zn anode, such as low redox protentional (-0.76V vs SHE), high theoretical capacity (820mAh/g), and enhanced safety. These features allow for high applicability in large-scale stationary energy storage system. Zinc-based batteries (MnO2/Zinc) have been previously commercialized and are one of the dominant technologies in the primary battery market. However, the alkaline MnO2/Zn battery is not currently considered re-chargeable due to the formation of zinc-dendrites, passivation of Zn metal, and cathode poisoning. In contrast to the alkaline system, the mild acidic system does not suffer from zinc passivation as there is negligible generation of zinc oxide/zinc hydroxide.In this work, we report a proof-of concept work where electrodeposited zinc-based anodes (zinc and zinc-alloys) are used in mild acidic aqueous electrolyte. The study provides a comparison of commercial zinc foil, and electrodeposited zinc/zinc-alloy. The anodes are further analyzed structurally through X-ray diffraction and scanning electron microscopy. To evaluate the feasibility of each anode. further electrochemical characterization was carried out in coin cells as symmetric and full cells. The electrodeposited zinc-based anodes exhibit low electrode polarization (~0.030-0.045V), and more stable cycling performance at 10 mA cm-2 compared to commercial zinc foil. Furthermore, full cells with an electrodeposited zinc or zinc-alloy anode, DTT cathode, in 2M ZnSO4 delivered comparable capacities but higher stability compared to commercial zinc. Consequently, this work points toward a further development for anode materials in rechargeable aqueous zinc batteries for scalable applications.

(Digital Presentation) Renewable Energy Storage Based on the Electrochemical Cycle of Hydrogen Peroxide

The large-scale application of intermittent renewable energy sources (such as wind and solar) requires low-cost, efficient, and zero-emission energy storage systems.1-5 Recently, we proposed an energy storage concept based on the electrochemical cycle of hydrogen peroxide (H2O2).6-8 As a proof-of-concept, we demonstrated a highly efficient PEM H2O2 electrolyzer (HPEL) for power-to-hydrogen conversion, and a unitized regenerative hydrogen peroxide cycle cell (UR-HPCC) with a round-trip efficiency (RTE) of above 90% for renewable energy storage.6, 7 The employment of platinum group metal-free (PGM-free) catalysts and other low-cost carbon materials in these devices promised a low system cost for large-scale energy storage.In this talk, we will present our recent study on the key factors affecting the performance and H2O2-cycle ability of the HPCC system. We identify the selectivity of anode catalyst in HPEL for hydrogen peroxide oxidation reaction (HPOR), the catalyst loading, and membrane thickness as the main performance-determining factors for HPEL. Specifically, the cobalt and nitrogen-doped carbon (Co-N-C) catalyst exhibits higher selectivity for HPOR over the H2O2 disproportionation reaction (HPDR) than Fe-N-C and Pt/C catalysts. Increasing the catalyst loading and membrane thickness can effectively inhibit the H2O2 crossover and thus improve the H2O2 utilization. By optimizing these factors, the crossover and disproportionation of H2O2 in the HPEL can be reduced significantly, resulting in higher system performance. On the other hand, high efficiency for H2O2 regeneration in the fuel cell component of the HPCC system is the key to the H2-H2O2 cycle. By optimizing the MEA fabrication method, catalyst loading, and operating conditions, we achieved high efficiency for H2O2 generation and remarkable power density in a PEM fuel cell. These results can guide the development of the next-generation large-scale renewable energy storage system. Acknowledgments Financial support from the State Key Laboratory of Coal Conversion, Institute of Coal Chemistry, Chinese Academy of Sciences is greatly appreciated. This study is financially supported by the autonomous research project of SKLCC (Grant No. 2021BWZ006), ICC CAS (Grant No. 2020SC001), Key Research and Development (R&D) Projects of Shanxi Province (Grant No. 202102070301018), and Shanxi Province grant (Grant No. 202103021224442 and 20210302123011). References S. J. Davis et al., Net-zero emissions energy systems. Science 360, eaas9793 (2018).X. Yang, C. P. Nielsen, S. Song, M. B. McElroy, Breaking the hard-to-abate bottleneck in China’s path to carbon neutrality with clean hydrogen. Nature Energy 7, 955-965 (2022).A. C. Bhosale, P. C. Ghosh, L. Assaud, Preparation methods of membrane electrode assemblies for proton exchange membrane fuel cells and unitized regenerative fuel cells: A review. Renewable and Sustainable Energy Reviews 133, 110286 (2020).Z. Pu et al., Regenerative fuel cells: Recent progress, challenges, perspectives and their applications for space energy system. Applied Energy 283, 116376 (2021).J. Tang, C. Su, Y. Zhong, Z. Shao, Oxide-based precious metal-free electrocatalysts for anion exchange membrane fuel cells: from material design to cell applications. Journal of Materials Chemistry A, 9, 3151-3179 (2021).R. Ding et al.. Low-voltage hydrogen peroxide electrolyzer for highly efficient power-to-hydrogen conversion. ChemRxiv, doi:10.26434/chemrxiv-2021-9dmp4 (2021).J. Yang et al., Highly efficient unitized regenerative hydrogen peroxide cycle cell with ultralow overpotential for renewable energy storage. Journal of Power Sources 545, 231948 (2022).R. Ding et al., (Digital presentation) Hydrogen peroxide electrolyzer and reversible hydrogen peroxide cycle cell for renewable energy storage, Meeting s, The Electrochemical Society, MA2022-01, 2495 (2022).

Kinetically well-matched porous framework dual carbon electrodes for high-performance sodium-ion hybrid capacitors

Sodium-ion hybrid capacitors (SIHCs) have attracted extensive interest due to their applications in sodium-ion batteries and capacitors, which have been considered expectable candidates for large-scale energy storage systems. The crucial issues for achieving high-performance SIHCs are the reaction kinetics imbalances between the slow Faradic battery-type anodes and fast non-Faradaic capacitive cathodes. Herein, we propose a simple self-template strategy to prepare kinetically well-matched porous framework dual-carbon electrodes for high-performance SIHCs, which stem from the single precursor, sodium ascorbate. The porous framework carbon (PFC) is obtained by direct calcination of sodium ascorbate followed by a washing process. The sodium-ion half cells with PFC anodes exhibit high reversible capacity and fast electrochemical kinetics for sodium storage. Moreover, the as-obtained PFC can be further converted to porous framework activated carbon (PFAC) with rich porosity and a high specific surface area, which displays high capacitive properties. By using kinetically well-matched battery-type PFC anodes and capacitive PFAC cathodes, dual-carbon SIHCs are successfully assembled, which can work well in 0–4 V. The optimal PFC//PFAC SIHC exhibits high energy density (101.6 Wh kg−1 at 200 W kg−1), power density (20 kW kg−1 at 51.1 Wh kg−1), and cyclic performance (71.8 % capacitance attenuation over 10,000 cycles).

(Invited) Rational Composition and Structure Designs for Layered Oxide Cathodes

Since its birth nearly three decades ago, lithium-ion battery (LIB) has changed all aspects of our life, from portable electronics, electric vehicles (EVs) to large-scale energy storage systems and the emerging electric flight applications. Currently, the bottleneck of the energy density of LIB is set by the intercalation cathode materials, which has been a significant push to develop high energy density and low-cost cathodes in response to rapidly expanding market. In this talk, I will focus on the identification of key failure modes and development of mitigation strategies for facilitating the future application of battery technologies. I will present some insights into the failure mechanism of battery materials that differ from the existing paradigms. Further, I will discuss how we can utilize rational composition and structure design to improve energy density, battery life without compromising safety, speed up battery charging, and reduce the cost of batteries.

LTO/TiO2 Nanowire-Decorated on Graphite Felt As Electrode for High-Performance Vanadium Redox Flow Battery

Vanadium redox flow battery(VRFB) is one of the most promising large-scale energy storage systems. However, the graphite electrode materials employed for VRFB often have shortcomings such as poor electrochemical activity and insufficient conductivity, which will lead to poor performance of VRFB. To modify the graphite electrode, in this study, lithium titanate/titanium dioxide(LTO/TiO2) composite catalyst with the nanowire morphology was directly grown on the surface of the heat treatment graphite felt(HGF). The graphite felt electrode through the nanowire morphology, the reaction area between the electrode and the electrolyte and active sites are increased, thereby improving the performance of VRFB. In order to further prove the effect of lithium titanate/titanium dioxide composite catalyst modified graphite felt(LTO/TiO2@HGF), the modified graphite felt electrode was applied to the positive and negative electrodes of VRFB, and the charge and discharge tests at different current densities were carried out. In terms of efficiency, the LTO/TiO2-modified graphite felt electrode has obviously better results. When the current density is increased to 200 mA/cm2, its energy efficiency can reach 60.57%, which is 8.63% higher than that of HGF. In the stability test with a current density of 160 mA/cm2, the VRFB was charged and discharged for 60 cycles, and the overall performance did not change significantly, which means that the composite material of lithium titanate and titanium dioxide not only effectively improve the performance of the VRFB, but also show the stability that can be used for a long time.

(Invited) Heterostructure Engineering in Electrode Materials for Sodium Ion Batteries

Sodium-ion batteries (SIBs) have stepped into the spotlight as a promising alternative to lithium-ion batteries (LIBs) for large-scale energy storage systems. However, the stability and performance of sodium ion battery electrode materials are lacking compared to their lithium counterparts as a consequence of the larger size of the Na+ ion compared to Li+. Heterostructure engineering is a promising strategy to overcome these intrinsic limitations toward practical SIBs. In this talk, we review the recent progress in heterostructure engineering of electrode materials and the origin of the phase interface’s influence on the Na+ storage and transport properties. Efficient strategies for the design and fabrication of heterostructures are discussed, with focus on the mechanism of heterostructure formation. The heterostructure’s influence on Na+ storage and transport properties is primarily generated from local distortions of the structure and chemomechanical coupling at the phase interface, which may accelerate ion/electron diffusion, create additional active sites, and bolster the structural stability. Finally, we will discuss the existing challenges, knowledge gaps, and opportunities toward the advancement of heterostructure engineering as a means to develop practical, high-performance sodium ion batteries.

Microstructural Engineering of Flow Battery Electrodes with Non-Solvent Induced Phase Separation

Rising levels of greenhouse gases urge the decarbonization of human activities. Electrification of strategic sectors such as transport, industry, and heating necessitates affordable, safe, and dispatchable large-scale energy storage systems. Redox flow batteries (RFBs) stand as a promising long-duration and large-scale energy storage technology due to their design features[1]. Ongoing research focuses on engineering key cell components (e.g. membranes, electrodes, active materials) to improve cost competitiveness. This work focuses on the fabrication of novel porous carbon electrodes which strongly influence the performance and cost of the technology. The requirements for porous electrodes liquid-phase electrochemical reactors are contradictory: a large surface area is needed to overall exchange current density, but also minimal pressure losses to decrease pumping costs. Additionally, surface properties of the electrode dictate the reaction kinetics whereas its microstructure controls the mass transport of the reactants within the reactor area[2]. However, the current state-of-the-art porous electrodes for RFBs consists of carbon-fiber materials repurposed from other electrochemical technologies (e.g. polymer electrolyte fuel cells) which do not offer a favorable tradeoff between transport properties and surface area. Additionally, their production involves complex manufacturing processes resulting in high cost and limited morphological versatility. Therefore, there is a need to develop alternative synthetic platforms which offer tailorable microstructures and surface properties to match the requirements of emerging electrochemical applications, such as redox flow batteries. In this work, we draw inspiration from the membrane technology and employ non-solvent induced phase separation (NIPS) as a method to synthesize porous carbon electrodes for RFBs[3,4].Here, we present our latest efforts to develop a manufacturing route enabling the control of microstructural features of carbonaceous porous electrodes for RFBs. The microstructure of the carbon scaffold is determined by the nature and composition of the polymer blend used to cast the electrode precursor. We use polyacrylonitrile as scaffold precursor and polyvinylpyrrolidone as a pore forming agent, dissolved in an organic solvent (i.e., dimethylformamide, dimethylsulfoxide or N-methylpyrrolidone). The polymer blends were cast into a mold and immersed in a water coagulation bath prior to being stabilized (270 °C) and carbonized (1050 °C). Various process parameters (e.g. polymer concentration, bath temperature, solvent type) governing the final electrode properties were leveraged to control structural features, opening new opportunities for the fabrication of diverse microstructures (i.e., porosity gradient, isoporosity and with macrovoids). Electrochemical double layer capacitance and pressure drop measurements show an increased design space compared to carbon-fiber electrodes, confirming the versatility of the synthetic route. Microstructural analysis of the prepared NIPS electrodes reveals two porosity domains: large finger-like macrovoids (throat diameter >50 μm) and smaller interconnected microvoids (pore diameter 2-15 μm). Flow cell polarization and electrochemical impedance spectroscopy measurements in two common flow battery electrolytes, an Fe2+/Fe3+ single electrolyte and vanadium full cell, show improvements in performance compared to traditional electrodes. An increase in the polymer concentration of the polymer blend solution produced NIPS electrodes with smaller pores and resulted in better mass transport within the electrode. When the temperature of the coagulation bath was increased to 40 ºC, the electrode has higher electrochemically active surface area, producing a significant power increase in the sluggish vanadium electrolyte. Overall, the NIPS electrodes operate at significantly lower activation and mass transport overpotentials in all-vanadium RFBs, generating higher electrical power at the expense of a slight pressure drop increase. Although preliminary, we demonstrate the potential of NIPS to manufacture electrodes with tailorable microstructures for convection-enhanced electrochemical technologies.[1] T. M. Gür, Energy Environ. Sci. 2018, 11, 2696.[2] A. Forner-Cuenca, E. E. Penn, A. M. Oliveira, F. R. Brushett, J. Electrochem. Soc. 2019, 166, A2230.[3] R. R. Jacquemond, C. T.-C. Wan, Y.-M. Chiang, Z. Borneman, F. R. Brushett, K. Nijmeijer, A. Forner-Cuenca, Cell Reports Physical Science 2022, 3, 100943.[4] C. T.-C. Wan, R. R. Jacquemond, Y.-M. Chiang, K. Nijmeijer, F. R. Brushett, A. Forner-Cuenca, Adv. Mater. 2021, 10. Figure 1

(Invited) Zinc/ Sodium Vanadium Oxide (NaV3O8) Aqueous Electrolyte Batteries: Competing Proton and Zinc Ion Insertion

Large-scale energy storage systems suitable for pairing with renewable energy generation require low-cost materials and safety. A promising candidate for large scale storage is the aqueous Zn-ion battery (AZIB). Zinc metal is a useful anode for aqueous batteries as it possesses a high theoretical capacity (820 mAh/g), low redox potential (-0.76 V vs SHE), and allows for two electron transfers per Zn2+ (de)insertion.Sodium vanadium oxides have been investigated as cathode materials for AZIBs as the size of Na+ is larger than Zn2+ facilitating ion diffusion within the lattice. Specifically, sodium vanadium oxide (NaV3O8, NVO) in an anhydrous form and its monohydrate (NaV3O8·H2O) have been identified as candidate materials. Notably, one of the phases that forms during the discharge of these materials within a zinc battery system is zinc hydroxy-sulfate (Zn4(SO4)(OH)6·5H2O (ZHS) and has been attributed to H+ insertion in NVO where the H+ insertion is accompanied by local pH change and precipitation of the ZHS.This presentation probes the competing zinc ion and proton insertion mechanisms for discharge of NVO. The impact of (dis)charge rate on reduction products formed is determined with quantitative Rietveld refinement analysis. Further, synchrotron based EDXRD providing spatio-temporally resolved data is used to determine phase evolution operando in different locations within thick porous NVO positive electrodes. Determining the reaction progression within thick electrodes while under load is an important aspect of scaling batteries appropriately, where these results can have relevance to development of future sustainable energy storage systems.

Degradation Behavior of Layered Structure Cathode in Sulfide Based All-Solid-State Batteries

With declaration of carbon zero in response to climate change, the importance is also being bandied about developing large-scale energy storage system, especially for electric vehicle (EV). Commercialized EV with a highest development lithium-ion batteries (LIB) could operate over 300 miles per single charging, but liquid electrolyte-based LIB gives rise to a huge risk concerning about ignition and explosion. All-solid-state batteries (ASSBs) is considered to alternative next-generation battery that have high safety advantageous with removal the risk of ignition by applying non-combustible inorganic solid-electrolytes (SEs). In case of sulfide-based ASSBs, there were progressed in performance itself at cell capacity increase and cycling characteristic due to advance in cell configuration, composite cathode, and cell fabrication technique compared to early works. Nevertheless, it is still demanded improvement related to the cathode-electrolyte interface stability, and its dominant causes are electrochemical- and chemo-mechanical problems. Therefore, most of researchers have tried to figure out the behavior of all-solid-state batteries by providing external pressure, and then resolve degradation issues including contact loss and resistive layer formation. However, in practical and commercialization aspects, the external pressured cell can be a stumbling block to scale-up from lab to large-scale ASSBs stage.In this study, we evaluated electrochemical performance using by general coin cell to investigate behavior of ASSBs, which is consisted with LiNi0.5Co0.2Mn0.3O2/Li6PS5Cl/VGCF|Li6PS5Cl|In-Li. The ASSB coin cell showed a significant capacity degradation having 59 % of capacity retention in 50th cycles, as expected. Herein, the main cause of the rapid capacity decrease is likely to be due to the accelerated physical contact loss. In addition to this, we have expanded the scope of analysis to investigate if there are other causes entire range including cell- and material level. The degradation in cell level is the inhomogeneous electrochemical reaction, that is within composite cathode, resulting from analysis of electrochemical impedance spectroscopy, cross-sectional scanning electron microscopy, x-ray diffraction, and X-ray photoelectron spectroscopy. This induces more severe degradation on close to SE separator, resulting in intensification of SE deterioration accompanied by damage implying a phase transformation of the active material. Furthermore, even though the contact loss problem has improved through re-pressing, the capacity was not recovered, which is because the material itself has deteriorated.Moving on to the material level, many cracks are observed inside of the active material, and sulfur infused into grain-boundary of active materials that confirmed by energy dispersive X-ray spectroscopy. In addition, through analyzing transmission electron microscopy, the phase transformation both mixed and rock-salt phase was confirmed the cathode surface of not only secondary particle but also primary particle of interior cathode. For more specifically affirmed this, various analysis including Raman spectroscopy and inductively coupled plasma optical emission spectroscopy were conducted, and we confirmed that the major cause is due to depletion of the Li source. Therefore, the loss of active Li by infused sulfur caused acceleration of deterioration cathode making poor capacity retention. This study is meaningful in providing another guideline that should be regarded for practical all-solid-state batteries through a new consideration in cathode degradation.