Critical metrics for practical application-oriented rechargeable zinc-air batteries

Nickel–Cadmium Cells Cell Fabrication Methods Silver–Zinc Cells Performance Other Silver Positive Electrode Systems Nickel–Zinc Cells Nickel–Hydrogen Cells Other Cell Systems Electrolyte Safety and Disposal Keywords: sealed cells; secondary cells

Filter paper derived three-dimensional mesoporous carbon with Co3O4 loaded on surface: An excellent binder-free air-cathode for rechargeable Zinc-air battery

There is a strong demand for rechargeable battery with large energy density and capacity because of increase in performance of mobile equipment such as mobile phone, laptop personal computer (PC) and also electric vehicle. At present, Li ion battery (LIB) have been widely used for such purpose. However, there are several issues such as the insufficient capacity and safety required to solve. Zinc-air batteries have been used commercially as a non rechargeable battery at present, however, recently, there is strong interest for development of rechargeable Zn-air battery because of its theoretical large capacity, low cost, and safety. However zinc-air rechargeable battery still has limits in cycle file and energy efficiency. In particular, increase in air electrode performance is strongly required. In this study, nickel cobalt spinel oxide, NiCo2O4, was studied as reversible air electrode for Zn-air battery. In addition, effects of dopant on oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) were studied. NiCo2O4 based spinel oxide is active to ORR and OER, however, surface area is still insufficient by the preparation of conventional hydrothermal method. Therefore, application of splay pyrolysis method for preparation of NiCo2O4 oxide is also studied for increasing ORR/OER activity and stability.NiCo2O4 based oxide was prepared by hydrothermal synthesis method and partial substitution was performed by using Mn, Fe, and Cu. On spray pyrolysis method, precursor solvent turned into nano-sized droplet by ultrasonic wave vaporizer, and the droplets are transferred to the tubular electric furnaces by air as carrier gas. The solvent evaporates from the droplets resulting in the formation of mesopore and after calcination, the fine powder is gathered in filters. Air electrode performance was measured by using gas diffusion layer, and PTFE and graphitic carbon were mixed with NiCo2O4 spinel for electrode. 8MKOH aqueous solution at 313K was used for electrolyte and a constant current of 20 mA/cm2 was applied by battery charge discharge equipment.Various spinel oxides were successfully prepared by hydrothermal synthesis method from XRD measurement. It was found that ORR and OER activity of MnCo2O4 and NiCo2O4 was reasonably high among the spinel oxides prepared. ORR activity is slightly higher on MnCo2O4, however, NiCo2O4 shows much longer cycle stability of ORR/OER. In addition, elution of Mn was observed in case of MnCo2O4, in contrast, almost no change in composition was observed for NiCo2O4 after cycle measurement. Therefore, NiCo2O4 shows reasonable activity to ORR and OER and high chemical stability. Effects of dopant on NiCo2O4 on ORR and OER activity and doping Cu and Fe is effective for increasing ORR potential and decreasing OER potential. Although the most superior performance of air electrode was observed on Cu doped one, elution of Cu is obviously observed. Therefore, from chemical stability, Fe doped NiCo2O4 is the most active to air electrode catalyst. The optimization of Fe amount in Ni site was also studied and it was found that Ni0.65Fe0.35Co2O4 is the most active and stable air electrode catalyst. On this electrode, overpotential for ORR reaction is around 0.25V at 20mA/cm2, 313 K and almost 500 cycles of ORR/OER which is 1 h ORR and OER each. In addition, introduction of mesoporous structure was achieved by splay pyrolysis method and increase in surface area is also effective for increasing stability to ORR/OER activity.This work is based on results obtained from a project, "Research and Development Initiative for Scientific Innovation of New Generation Batteries (RISING2)", JPNP16001, commissioned by the New Energy and Industrial Technology Development Organization (NEDO).

The effective utilization of clean energy and finding alternatives to fossil resources are highly important to ensure the sustainability of human society and are always among the major goals of both chemistry and material science research. Advanced electrochemical devices, such as fuel cells, water electrolysers and metal-air batteries, represent the most promising strategies for clean-energy utilization. In an electrochemical device, the redox reactions are spatially separated by a membrane, allowing direct extraction/transfer of electrons at an electrode-electrolyte interface, which leads to higher intrinsic energy conversion efficiencies, milder process conditions, easy product separation and excellent design features for coupling to renewable energy infrastructure. The performance of such electrochemical processes is fundamentally determined by the physicochemical properties of the electrochemical interfaces, encompassing both the electrocatalyst and the structure of the adjacent electrochemical double layer. Specifically, electrocatalysts play key roles in electrochemical reactions and often limit the performance of entire systems due to their insufficient activity, low durability or high cost. Ideally, the rate, efficiency, and selectivity of the above electrochemical reactions can be substantially improved by developing high-performance electrocatalyst. One of the central tasks for chemists and material scientists is to design and fabricate the high-efficient efficiency but low-cost electrocatalysts systems. The current promising electrochemical reactions mainly focus on the realization of the reversible conversion between chemical and electricity energy, e.g., the oxygen reduction reaction (ORR), oxygen evolution reaction (OER), hydrogen oxidation reaction (HOR), and hydrogen evolution reaction (HER). Coupling of the above electrochemical reactions provide a solid foundation for various essential electrochemical devices, such as direct hydrogen fuel cells (HOR + ORR); electrolysers (OER + HER); rechargeable zinc (Zn)-air battery (ORR + OER). Therefore, this thesis aims to design and synthesize high-performance electrocatalysts for HER, ORR and OER based on earth-abundant materials with proper hierarchical 2D or 3D nanostructures. Combined with the advanced characterization techniques and density functional theory (DFT) calculations, the relationship between the electrochemical activity and active sites of these earth-abundant electrocatalysts were detailedly explored and confirmed. Furthermore, to emphasize the hierarchical 2D or 3D nanostructures, the actual performance of these electrocatalysts was all evaluated in practical devices including Zn-air battery and proton exchange membrane fuel cell (PEMFC), specifically as follows: (1) The vast majority of the reported HER electrocatalysts performs poorly under alkaline conditions due to the sluggish water dissociation kinetics. In the first work, a hybridization catalyst construction concept is presented to dramatically enhance the alkaline HER activities of catalysts based on 2D transition metal dichalcogenides (TMDs) (MoS2 and WS2). A series of ultrathin 2D-hybrids are synthesized via facile controllable growth of 3d metal (Ni, Co, Fe, Mn) hydroxides on the monolayer 2D-TMD nanosheets. The resultant Ni(OH)2 and Co(OH)2 hybridized ultrathin MoS2 and WS2 nanosheet catalysts exhibit significantly enhanced alkaline HER activity and stability compared to their bare counterparts. The combined theoretical and experimental studies confirm that the formation of the heterostructured boundaries by suitable hybridization of the TMD and 3d metal hydroxides is responsible for the improved alkaline HER activities because of the enhanced water dissociation step and lowers the corresponding kinetic energy barrier by the hybridized 3d metal hydroxides. (2) Nitrogen-coordinated iron atoms on carbon matrix (Fe-N-C) materials are the most active Pt-group-metal-free ORR catalysts but still suffering their low stability and relatively lower activity compared to platinum-based materials. In the second work, Fe and Ni dual sites atomically dispersed in hierarchically ordered macroporous carbon support (Fe-Ni/N-HOMC) was designed and successfully prepared. Isolated atomic Fe- N4 and Ni-N4 active sites were confirmed via various characterizations. The ORR activity and stability of Fe-Ni/N-HOMC in both acid and alkaline electrolyte were much higher than commercial Pt/C and the mono-Fe doping counterpart, which was among the state-of-the-art ORR electrocatalysts. In addition, this 3D ordered interconnected macroporous structure with abundant mesopores and micropores could greatly increase the accessible ORR active site and also enhance the mass transport during the ORR process. When employed as cathodes for PEMFC, we found the excellent ORR activity of Fe-Ni/N-HOMC was completely translated to the cathode in the fuel cell. (3) High-performance bifunctional electrocatalysts with ORR and OER activity is the key to developing efficient rechargeable Zn-air batteries. In the third work, a high-performance bifunctional electrocatalysts for both OER and ORR were synthesized via further hybridizing as-prepared Fe-Ni/N-HOMC with NiFe layer double hydroxides (LDHs). Layered double hydroxides (LDHs) have been reported to be promising OER electrocatalysts with ultrahigh OER performances. The as-synthesized new composites exhibited almost the same ORR activity as Fe-Ni/N-HOMC, revealing that hybridization of NiFe-LDHs would not deteriorate the initial ORR activity. Moreover, the remarkable enhancement of OER activity was observed after the hybridization, which was attributed to the strong coupling of uniformly dispersed small NiFe-LDH nanoparticles with the carbon substrate. The prototype Zn-air battery was assembled using these new composites, which displayed the ultralow voltage gap and long-term stability. (4) Compared with Fe-N-C or Co-N-C based ORR electrocatalysts, the Cu-nitrogen-carbon composites were attracted little attention. However, the natural multicopper oxidases (MCOs) enzymes, such as laccase, can serve as efficient ORR catalyst with almost no overpotential. Inspired by their tris-copper centers in MCO, one novel Cu-nitrogen-carbon composite (Cu SAs/N-CS) with atomic Cu coordination sites were synthesized via the pyrolysis of the Cu-involved metal-organic-framework. The copper contents in Cu SAs/N-CS reaches as high as 3.17 wt.%, and the average distances of adjacent copper sites was around only 3.1 Å. Due to the synergetic effect of abundant single atomic copper active sites with closer distance and ultrathin carbon nanosheet structure, Cu SAs/N-CS exhibited superior ORR activity exceeding commercial Pt/C catalyst, methanol tolerance, and long-term stability in both alkaline and neutral electrolyte. In summary, four kinds of new composites were successfully designed and prepared as high-performance electrocatalysts for HER, ORR and OER. Multi-dimensional heterostructures, atomic metal coordination sites and 3D hierarchically porous structure were designed and observed, which contributed greatly to improve activities of these composites. This thesis suggests several new viewpoints in the design of electrocatalysts based on earth-abundant materials: (i) offering new strategies for the preparation of novel 2D and 3D heterostructures as electrocatalysts; (ii) expanding methods for the synthesis of atomic metal coordination sites and evaluating their activities for ORR; (iii) evaluating the practical performances of achieved electrocatalysts in proton exchange membrane fuel cell and Zn-air battery; (iv) attempting to explain reaction mechanisms of some electrocatalysts by DFT calculation.

We investigated the correlation among surface chemistry, morphology, and current densities of the charge‐discharge processes and the performance of lithium electrodes in Li vs. Li half‐cell testing and practical rechargeable AA batteries (Tadiran Batteries, Limited). The electrolyte system was /tributylamine (stabilizer)/1,3 dioxolane solution. It was found that the performance of the lithium anodes in practical batteries depends on the current densities at which the batteries are operated. These determine the surface chemistry of the anodes in the following manner: at sufficiently high discharge rates (Li dissolution) the native films which cover the active metal are replaced completely and rapidly by surface films which originate from solvent‐reduction processes. These films induce uniform, dendrite‐free Li deposition. At too‐low discharge rates, part of the native films remains, and thus the surface films are too heterogeneous. This leads to dendritic Li deposition. Charging the batteries at too‐high rate (Li deposition) leads to the exposure of fresh Li to the solution, which reacts predominantly with the salt anion . The surface films thus formed (comprised of LiF, species, etc.) lead to nonuniform Li deposition. It is possible to adjust charging rates which lead to lithium deposition with a very minor exposure of fresh lithium, and thereby change the Li surface chemistry to that dominated by solvent reduction. This leads to an extended cycle life of the Li anodes due to the uniform Li deposition that the surface films thus formed induce.

Construction of Co/FeCo@Fe(Co)3O4 heterojunction rich in oxygen vacancies derived from metal–organic frameworks using O2 plasma as a high-performance bifunctional catalyst for rechargeable zinc-air batteries

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.

12 - Metal - air cells

Rechargeable Zn-air batteries have received extensive attention due to their use of nontoxic materials, safety, and high energy density. However, the oxygen reduction reaction (ORR) and oxygen evolution reaction (OER) at the air electrode of Zn-air batteries both suffer from slow kinetics, limiting their commercialization development. Herein, we prepared Co, N, and S co-doped hollow carbon nanoboxes (Co-N/S-CNBs) rich in topological defects using polyphenylene sulfide (PPS) as a sulfur-rich carbon source. Critically, by utilizing the self-propagating high-temperature synthesis (SHS), PPS can avoid melting, while simultaneously enabling the catalyst to take on a unique hollow structure. Additional post-treatment to introduce Co and N atoms as active centers further increases the defect sites and microporous structures of the catalyst. Under alkaline electrolytes, the Co-N/S-CNBs enabled Zn-air batteries to exhibit excellent bifunctional catalytic activity for both ORR and OER, surpassing commercial catalysts. Chemical analysis showed that the cracking loss of small molecules from PPS during pyrolysis is the main reason for the formation of topological defects, where the defect sites act as active centers to enhance the catalytic performance. Overall, this work provides new insights into the mechanism of how defects are formed in such a catalyst, as well as shows how a high-performance bifunctional electrocatalyst can be utilized for practical Zn-air batteries.

The proliferation of portable electronic devices has fueled rapid market growth for the rechargeable battery industry. Miniaturization of electronics coupled with consumer demand for lightweight batteries providing ever longer run times continues to spur interest in advanced battery systems. Interest also continues to run strong in electric vehicles (EVs) and the large auto manufacturers continue to develop prototype EVs. Advanced batteries continue to play a strong role in other applications such as load leveling for the electric utility industry and satellite power systems for aerospace. Secondary battery systems have been based on aqueous electrolytes. The use of water imposes a fundamental limitation on battery voltage because of the electrolysis of water. The application of nonaqueous electrolytes affords a significant advantage in terms of achievable battery voltages. By far the most actively researched field in nonaqueous battery systems has been the development of practical rechargeable lithium batteries based on the use of lithium metal, Li, or a lithium alloy, as the negative electrode. The use of lithium as a negative electrode for secondary batteries offers a number of advantages. Lithium has the lowest equivalent weight of any metal and affords very negative electrode potentials when in equilibrium with solvated lithium ions, resulting in very high theoretical energy densities for battery couples. These high theoretical energy densities have prompted a wealth of research activity in a wide variety of experimental battery systems. However, realization of the technology to commercialize these systems has been slow. A key technical problem in developing practical lithium batteries has been poor cycle life attributable to the lithium electrode. The highly reactive nature of freshly plated lithium leads to reactions with electrolyte and impurities to form passivating films that electrically isolate the lithium metal. The formation of surface films on the lithium electrode imparts the apparent stability of the electrolyte to the electrode. In addition to providing a stable film in the presence of lithium, the electrolyte must satisfy additional requirements, including good conductivity, being in the liquid range over the battery operating temperature, and electrochemical stability over a wide voltage range. In order to satisfy the various electrolyte system requirements, the use of mixed solvent electrolytes has become common in practical cells. Examples are tetrahydrofuran, C 4 H 8 O, ‐based electrolytes or ethylene carbonate C 2 H 4 O 3 ,–propylene carbonate, C 4 H 6 O 3 , mixed solvent systems. A second class of important electrolytes for rechargeable lithium batteries are solid electrolytes. Of particular importance is the class known as solid polymer electrolytes (SPEs), polymers capable of forming complexes with lithium salts to yield ionic conductivity. The best known of the SPEs are the lithium salt complexes of poly(ethylene oxide) (PEO), —(CH 2 CH 2 O h ) n —, and poly(propylene oxide) (PPO). The lithium or lithium alloy negative electrode systems employing a liquid electrolyte can be categorized as having either a solid positive electrode or a liquid positive electrode. Systems employing a solid electrolyte employ solid positive electrodes to provide a solid‐state cell. The most important rechargeable lithium batteries are those using a solid positive electrode within which the lithium ion is capable of intercalating. These intercalation, or insertion, electrodes function by allowing the interstitial introduction of the ion into a host lattice. Intercalation electrodes have found wide application in systems employing both solid or liquid electrolytes. The use of high temperature lithium cells for electric vehicle applications has been under development since the 1970s. Advances in the development of lithium alloy–metal sulfide batteries have led to lithium–aluminum/metal sulfide batteries, ie, the Li–Al/FeS system. The cell employs a molten salt electrolyte, most commonly a lithium chloride/potassium chloride, LiCl–KCl eutectic mixture. The negative electrode is composed of lithium–aluminum alloy, which operates at about 300 mV positive of pure lithium. The positive electrode is composed of iron sulfide mixed with a conductive agent such as carbon or graphite. Electrodes are constructed by cold pressing powder onto current collectors. The best known of the high temperature batteries is the sodium–sulfur, Na–S, battery. The cell is constructed using a solid electrolyte typically consisting of β‐alumina, β‐Al 2 O 3 , ceramic, although borate glass fibers have also been used. The negative electrode consists of molten sodium metal and the positive electrode of molten sulfur. Because sulfur is not conductive, a current collection network of graphite is required. The cell is operated at about 350°C. The Na–S battery couple is a strong candidate for applications in both EVs and aerospace. The Na–S system is expected to provide significant increases in energy density for satellite battery systems. A battery system closely related to Na–S is the Na–metal chloride cell. The cell design is similar to Na–S; however, in addition to the β‐alumina electrolyte, the cell also employs a sodium chloroaluminate, NaAlCl 4 , molten salt electrolyte. The positive electrode active material consists of a transition metal chloride such as iron(II) chloride, FeCl 2 , or nickel chloride, NiCl 2 , in lieu of molten sulfur. This technology is in a younger state of development than the Na–S. Rechargeable cells employing aluminum, Al, as a negative electrode in room temperature molten salts have been investigated. Redox flow batteries, under development since the early 1970s, are still of interest primarily for utility load leveling applications. Examples of this technology include the iron–chromium, Fe–Cr, battery and the vanadium redox cell. Commercialization of advanced battery systems is limited. Efforts to develop commercially viable EV versions of advanced battery systems continue. The ultimate goal is to develop battery technology suitable for practical, consumer‐acceptable electric vehicles.

What matters in engineering next-generation rechargeable Zn-air batteries?

Fast-charging capability and calendar life are critical metrics in rechargeable batteries, especially in silicon-based batteries that are susceptible to sluggish Li+ desolvation kinetics and HF-induced corrosion. No existing electrolyte simultaneously tackles both these pivotal challenges. Here we report a microscopically heterogeneous covalent organic nanosheet (CON) colloid electrolyte for extremely fast-charging and long-calendar-life Si-based lithium-ion batteries. Theoretical calculations and operando Raman spectroscopy reveal the fundamental mechanism of the multiscale noncovalent interaction, which involves the mesoscopic CON attenuating the microscopic Li+-solvent coordination, thereby expediting the Li+ desolvation kinetics. This electrolyte design enables extremely fast-charging capabilities of the full cell, both at 8 C (83.1 % state of charge) and 10 C (81.3 % state of charge). Remarkably, the colloid electrolyte demonstrates record-breaking cycling performance at 10 C (capacity retention of 92.39 % after 400 cycles). Moreover, benefiting from the robust adsorption capability of mesoporous CON towards HF and water, a notable improvement is observed in the calendar life of the full cell. This study highlights the role of microscopically heterogeneous colloid electrolytes in enhancing the fast-charging capability and calendar life of Si-based Li-ion batteries. Our work offers fresh perspectives on electrolyte design with multiscale interactions, providing insightful guidance for the development of alkali-ion/metal batteries operating under harsh environments.

Fast‐charging capability and calendar life are critical metrics in rechargeable batteries, especially in silicon‐based batteries that are susceptible to sluggish Li+ desolvation kinetics and HF‐induced corrosion. No existing electrolyte simultaneously tackles both these pivotal challenges. Here we report a microscopically heterogeneous covalent organic nanosheet (CON) colloid electrolyte for extremely fast‐charging and long‐calendar‐life Si‐based lithium‐ion batteries. Theoretical calculations and operando Raman spectroscopy reveal the fundamental mechanism of the multiscale noncovalent interaction, which involves the mesoscopic CON attenuating the microscopic Li+‐solvent coordination, thereby expediting the Li+ desolvation kinetics. This electrolyte design enables extremely fast‐charging capabilities of the full cell, both at 8 C (83.1 % state of charge) and 10 C (81.3 % state of charge). Remarkably, the colloid electrolyte demonstrates record‐breaking cycling performance at 10 C (capacity retention of 92.39 % after 400 cycles). Moreover, benefiting from the robust adsorption capability of mesoporous CON towards HF and water, a notable improvement is observed in the calendar life of the full cell. This study highlights the role of microscopically heterogeneous colloid electrolytes in enhancing the fast‐charging capability and calendar life of Si‐based Li‐ion batteries. Our work offers fresh perspectives on electrolyte design with multiscale interactions, providing insightful guidance for the development of alkali‐ion/metal batteries operating under harsh environments.

Next-generation rechargeable batteries are expected to exhibit safety, long life, high power and high energy density. Rechargeable batteries are composed of a positive electrode, a negative electrode, and electrolyte. Improvement of their characteristics themselves, such as capacity, conductivity, or stability by tuning materials, has been one of the main research topics. However, practical batteries are complex system using other functional materials in order to improve battery performance at the pack level. Therefore, the behavior of carrier ions inside the practical battery is also important research topics for the development of rechargeable batteries.For charge/discharge of conventional lithium-ion batteries using an organic electrolyte, an inhomogeneous reaction in composite electrodes related to practical charge/discharge performance has been reported1). Electrodes of lithium-ion batteries are composed of active material, conductive carbon, and binder. Electrolyte is poured into void spaces of composite electrodes, which has a role for ion transport. The electric and ionic conductions must be maintained during charge/discharge. However, these conduction paths depend on the mesoscale structure of composite electrodes, which causes the reaction distribution in composite electrodes. The reaction inhomogeneity is quite related to the practical cell performance of batteries such as safety, cycle life, and rate capability. It has been reported that a reaction distribution forms in the electrode depth direction due to the presence of this nonuniform balance between electric and ionic resistances, and the active area for charge/discharge in composite electrode decreases1). In addition, during high-rate charge/discharge in which a large current flow, not only such an inhomogeneous SOC in electrodes but also concentration change of electrolyte occurs. For electrolyte used for lithium-ion batteries, the lithium-ion transport number is small, about 0.4. Therefore, a salt concentration gradient can be formed in the electrolyte during charge/discharge, and the utilization of lithium-ion is greatly restricted. From the results of NMR measurement, a concentration distribution of 0.78 to 1.27 M is reported2). On the other hand, in the case of the all-solid-state rechargeable battery, the transport number of the carrier ions of the solid electrolyte is 1, so in principle, it is considered that a concentration distribution of carrier is not occurred, and therefore, the high energy density and high rate characteristics are expected. However, direct measurement of concentration distribution in solid electrolyte during battery operation has not been reported.In this study, we introduce examples of the analysis of reaction distribution using synchrotron radiation X-ray in rechargeable batteries. In lithium-ion batteries, nonuniform reaction phenomena of electrode active material were analyzed by two-dimensional imaging XAFS. The results indicate that ion conduction governs the reaction rate inside the composite electrode. In addition, changes in the concentration of the electrolyte solution were investigated by X-ray radiography. For the analysis in all-solid-state battery, the model system was developed using silver ions as probes3), and the characteristics of the all-solid secondary battery were analyzed under charge/discharge conditions.

This paper studies the critical topic of optimal sizing of energy resources, focusing specifically on the configuration of storage system solutions within a microgrid framework. A microgrid is a localized energy system that can operate independently or in conjunction with the main power grid, and it is increasingly recognized for its potential to enhance energy resilience, efficiency, and sustainability. In this study, we examine a microgrid that integrates three key components: photovoltaic (PV) systems, battery storage, and fuel cell (FC) systems. Each of these technologies plays a vital role in the overall energy management strategy of the microgrid. In addition to installation costs, we also focus on minimizing net present costs (NPC), which encompass the total cost of ownership over the lifespan of the energy systems, including initial capital expenditures, operational and maintenance costs, and any potential revenue from energy sales or savings. By carefully analyzing the trade-offs between different system configurations, we seek to identify the most economically viable options. Another critical metric we consider is the loss of load expectation (LOLE), which quantifies the reliability of the energy supply. LOLE represents the expected number of hours per year during which the energy demand exceeds the available supply. By minimizing LOLE, we enhance the reliability and stability of the microgrid, ensuring that it can meet the energy needs of its users even during periods of high demand or low generation. Through a comprehensive analysis of these factors, this paper aims to provide valuable insights into the optimal sizing of energy resources within microgrids. By leveraging advanced modeling techniques and optimization algorithms, we seek to identify configurations that not only reduce costs but also enhance the overall performance and reliability of hybrid energy systems. Ultimately, our findings will contribute to the ongoing efforts to develop sustainable and resilient energy solutions that can meet the challenges of a rapidly changing energy landscape. The teaching-learning-based optimization (TLBO) metaheuristic algorithm is employed for configuring microgrids. Results from the algorithm demonstrate that TLBO offers a more effective resource configuration than alternative approaches.