Fast and Reversible Four-Electron Storage Enabled By Ethyl Viologen for Rechargeable Magnesium Batteries

Magnesium (Mg) batteries are the most promising “post‐lithium‐ion” energy storage technologies owing to their high theoretical energy density, low cost, and intrinsic safety with air and moisture. However, the development of Mg batteries has been limited to cathode materials leading to low power, low reversible energy density, and poor cycle life. Here, a new Mg cathode is reported based on ethyl viologen (EV), which not only has a fast redox couple EV2+/EV0 but also is capable of coupling with redox‐active anions, such as iodide (I−), achieving a total four‐electron storage. The EV2+/EV0 redox couple demonstrates a superior rate performance (10 C) and stable cycle life (500 cycles) owing to intrinsic fast electrode kinetics. A high material utilization (>80%) can be achieved at 1.0 C under a high areal loading of 5 mg cm−2. When coupling with iodide I−, a reversible four‐electron storage is achieved with a high energy density (304.2 Wh kg−1) and a stable cycle life (>100 cycles). This study provides effective strategies for designing reversible multielectron storage for high‐rate and high‐energy rechargeable Mg batteries.

Our modern and technological society requests enhanced energy storage devices to tackle the current necessities. In addition, wearable electronic devices are being demanding because they offer many facilities to the person wearing it. In this manuscript, a historical review is made about the available energy storage devices focusing on super-capacitors and lithium-ion batteries, since they currently are the most present in the industry, and the possible polymeric materials suitable on wearable energy storage devices. Polymers are a suitable option because they not only possess remarkable mechanical resistance, flexibility, long life-times, easy manufacturing techniques and low cost in addition to they can be environmentally friendly, nontoxic, and even biodegradable too. Moreover, the electrical and electrochemical polymer properties can be tunning with suitable fillers giving to versatile conducting polymer composites with a good cost and properties' ratio. Although the advances are promising, there are still many drawbacks that need to be overcome. Future research should focus on improving both the performance of materials and their processability on an industrial scale, where additive manufacturing offers many possibilities. The sustainability of new energy storage devices should not

According to the progress of electronics industry, electronic devices have been diversified to various forms such as roll-up displays, smart cards, and wearable devices. Flexible electronic devices are demanding has various properties such as lightweight, ultrathin, and flexibility. Therefore, batteries as their power sources are required to have same properties. In addition, high energy density and operational safety are needed. Until now commercial lithium-ion batteries (LIBs) are the only viable candidates for flexible devices. Recently, the flexible lithium/sulfur (Li/S) battery has been proposed with a high theoretical energy density of 2600 Wh kg-1. As most active materials considered in these studies are rigid and brittle, flexible cathodes were achieved by the physical combination of rigid active materials with flexible current collectors such as carbon-based materials or polymers. This integrated design has two inevitable disadvantages; (1) during deformation the active material can detach from the current collector; (2) the capacity per electrode is reduced by the presence of electrochemically inactive materials such as current collector, binder and conducting agents. Therefore, there is a strong need for a new approach to the flexible cathode which consists of only active material without a separate current collector. Sulfurized polyacrylonitrile (SPAN) composite could be a good candidate due to its good electric conductivity, high sulfur utilization, and stable cycle life. In addition, it can be fabricated as either particle or nanofiber. However, the SPAN electrodes reported so far were prepared by mixing SPAN, conductive agent, and binder which were pasted on metallic current collector. In carbon nanotube paper and graphene paper, it is well-known that the strain during deformation decreases with the diameter of the fiber. Therefore, in this work, the SPAN nanofiber web cathode which does not include conductive agent, binder, as well as current collector was fabricated from PAN nanofiber web and sulfur by heat treatment process. Also, pre-lithiated carbon felt was used as anode in order to make all flexible full cell and investigated its electrochemical properties.

Antiferroelectrics (AFEs) with high energy density and fast discharge speed are greatly needed to improve the performance of capacitors. In the present work, La-doped PbHfO3 ceramics were fabricated and the antiferroelectricity was investigated. The complicated phase transition behavior at both high electric field and rising temperature in composition Pb0.94La0.04HfO3 was revealed. Multiple phase transition was observed at high field, and when rising the temperature to 110 °C, an intermediate phase transition to another AFE phase was observed. The Pb0.94La0.04HfO3 ceramics have a high recoverable energy density of 10.2 J/cm3 and efficiency of 81.7%. Double P–E loop could be observed even at 180 °C, ensuring the high energy density at high temperature. In addition, a high current density of 2109 A/cm2 and a power density of 369 MW/cm3 could be obtained. This work revealed the antiferroelectricity in La-doped PbHfO3 ceramics and proved their potential for high energy and power density applications.

The prime importance in the energy storage field is to develop a new system that can combine high energy and power density. While lithium-ion batteries (LIBs) have become scientifically and commercially important because of their high energy densities, their power densities are not sufficient for emerging large-scale applications. Supercapacitors, on the other hand, are capable of delivering very high power due to their intrinsically fast surface-reaction mechanism, but they fail to meet high energy density requirements. This presentation proposes a new type of battery that adopts the fast surface reaction mechanism mimicking the supercapacitor without sacrificing energy density: an all-graphene energy storage device. The key advantages of an all-graphene energy storage device are that (i) both electrodes (a functionalized graphene cathode and a reduced graphene anode) exhibit fast surface reactions instead of intercalation while maintaining high energy density, and (ii) simple chemical modification of graphene yields either the anode or the cathode in a one-pot synthesis. Combined with controlled porous morphology and high electrical conductivity of graphene, the all-graphene energy storage device was capable of delivering a high energy of 195 Wh/kgtotal electrode, which is comparable to the energy density of conventional LIBs. The newly developed all-graphene energy storage device also retains 8.5 Wh/kgtotal electrode (energy) and 3,300 W/kgtotal electrode (power) at charge/discharge rates of just a few seconds. This energy and power performance perfectly spans the region that conventional LIBs and supercapacitors cannot reach. The performance and operating mechanism of an all-graphene energy storage device resemble those of both supercapacitors and batteries, blurring the conventional distinction between the two. This work sheds new light on the development of advanced energy-storage devices that bridge the performance gap between LIBs and supercapacitors. Presenting author: H. Kim E-mail: kimhaegyeom1@gmail.com Corresponding author: K. Kang E-mail: matlgen1@snu.ac.kr

Fast development of portable electronic devices (such as a smart phone, iPad, and Galaxy Note) and electrified vehicles (such as EVs and HEVs) require better and smaller lithium ion batteries as their energy storages. What is needed for the cathode of the lithium ion battery is a material capable of a higher volumetric energy density as well as gravimetric energy density. However, not only the development of cathode material but also the commercialization of high energy density anode material has been limited due to cathode material’s much lower energy density compared to anode material. In this regard, Li-rich material (Li2MnO3-LiMO2, M=Ni, Mn and Co) that has 150 % higher energy density than commercialized LiCoO2 is the unique next generation cathode material to solve the problem of cathode material’s low energy density. In the past decade, many researches have focused on the surface stabilization method of this material to improve its intrinsic problems of poor cycle/ rate capability and such surface treatment methods have been demonstrated in a few examples, including AlF3 coating and spinel heterostructures, yielding noticeable improvements in rate and cycle ability. Although such surface treatments showed improved rate and cycle performances, achieving the high volumetric energy density and long-term cycle life which are more critical factors for the commercialization of Li-rich material still remained unsatisfied. In general, Li-rich material’s reversible capacity is related with its particle size since the Li2MnO3 phase in large Li-rich material, which is a major component to realize high energy density, is not fully activated in low voltage range below 4.6 V. For this reason, many previous papers reported their results with only small primary particle size below 100nm. The high surface area induced by the small particle size increases side reactions with electrolyte resulting poor long-term cycle life as well as lowers the volumetric energy density. Note that Li-rich material’s deteriorations are generated from its surface and continue to affect its cycling capability and the deteriorations can be divided into two mechanisms: one is side reactions with electrolyte, and another is the phase collapse. The side reactions with electrolyte at its high working voltage yield active material attack speiceses such as HF and electrolyte exhaustion causing Li-rich material’s fast discharge capacity decay during cycles. Furthurmore, it is hardly show long-term cycle life with over 200 cycles since the phase transition from layered structure to spinel-like and NiO rock salt is generated on the surface of active material, and followed by expention of this transition into the bulk. For instance, AlF3 coated Li-rich LNCMO has abrupt capacity fade after 100 cycles, although it showed good rate and cycle capability within 100 cycles. Hence, new active material design, rather than simple surface modification methods such as coating or doping, is required to solve above previous limits.The new material design needs to start with a simple question: how to minimize the damages of surface deteriorations such as side reasction with electrolyte and phase trasnsition on bulk material and maximize volumetric energy density. The most effective solution for the question is increasing the primary particle size with the stable activation method, since the volumetric energy density of cathode material is maximized from synthesis of micron secondary particles consisted of primary particles by using co-precipitation method in industry. Here we demonstrate a novel approach for lithium storage, which is a material design of a secondary structure which consists of large flake shaped primary particle (hundred nanometers x mictrometers) with a novel activation method using simple chemical treatment to achieve superior long-term cycle life with high volumetric energy density. In this design, the large primary particle effectively reduced its surface area producing markedly decreased surface instability reaction as well as high tap density. Interstingly, the chemical approach activated only surface Li2MnO3 phase of large primary particle and the very surface activation effectively overcame the activation problem, which is limit of large primary particle have. This novel concept is very meaningful in that it is the first and unique method to achieve cathode material’s high volumetric energy density with long-term cycle life. As a result, this novel designed material affords remarkable battery performance with extremely high cycle retention during 400 cycles and high volumetric energy density ever reported before.

Lithium-Ion Batteries receive growing attention because of their potentially high energy and power density, which are important requirements for automobile applications. Reports agreed that the positive electrode is hereby the performance limiting cell component. NxMyCz (nickel manganese cobalt spinel) is one of the most promising cathode materials, both due to its rather high operating voltage and to either high power or energy density [1]. Hereby, a compromise between high power (thin layers and, i.e., high porosity) and high energy density (thick layers and, i.e., low porosity) has to be reached, in particular for automotive applications. This demands for an extended understanding of the interplay between microstructure parameters and chemical stoichiometry of NMC cathodes on cell performance characteristics. In this study, two NMC - cathodes recovered from commercial high energy and high power cells are analyzed (i) by SEM and X-ray tomography and (ii) by Electrochemical Impedance spectroscopy (EIS). By evaluating the impedance spectra measured at 0 to 40°C and at SOC 0 to SOC 100 by the distribution function of relaxation times (DRT) [2], a physically motivated transition line model [3] was established. The microstructure parameters required for a quantitative analysis of the electrochemical loss processes were obtained by X-ray tomography data. Additionally, the exact composition is determined by energy dispersive X-ray spectroscopy (EDX) investigations The results confirm, that a NMC electrode custom tailored for high energy density is rather thick (70 µm) and made of large low-porous agglomerates of primary particles, as described in [4]. The significant difference between the NMC cathode of a high energy and a high power cell however is not, as expected, a significantly higher porosity, but a sophisticated combination of small carbon black particles and elongated carbon black fibers, enabling high discharge currents. The tortuosity of the electrode pores, which represent the transport pathways for the liquid electrolyte, is low for the high power cell, which raises the effective electrolyte conductivity significantly, when compared to the high energy cell [4]. Furthermore the high power cell features a special compound of two different NxMyCz active materials. By including all the results from EIS, DRT, X-ray tomography and EDX, an evaluation of the influence of composition and microstructure on performance characteristics of the NxMyCz cathodes will be presented.

Capacitive contribution matters in facilitating high power battery materials toward fast-charging alkali metal ion batteries

Aqueous multi-electron electrolyte for hybrid flow batteries with high energy and power densities

A branched dihydrophenazine-based polymer as a cathode material to achieve dual-ion batteries with high energy and power density

We present a novel approach for the fabrication of lithium-ion microbattery electrodes which deliver high energy and high power density. The key enabling technology is the use of self-assembled <i>Tobacco mosaic</i> virus (TMV) nanoforests as a template for active battery materials. The self-assembling TMV is a genetically modified biological nanorod with increased metal binding properties for enhanced manufacturability. High energy density is achieved due to the active surface area increase within a given footprint by combining TMV with three-dimensional (3D) microfabricated structures. The TMV nanostructure enables high power density through larger electrode/electrolyte contact area and faster charge transport. The electrodes consist of an array of electroplated gold micropillars. The pillars are coated with the self-assembled nanoscale TMV template and subsequently metalized in-place. Active battery material (V₂O₅) is conformally deposited using atomic layer deposition (ALD) on the hierarchical micro/nano network. Electrochemical testing of these electrodes indicates a 3-5 fold increase in energy density, compared to the TMV-templated electrodes without micropillars, without increasing footprint area or reducing rate performance. Further increase in energy density can be achieved by increasing surface area of 3D microelements as demonstrated by fabrication and electrochemical testing of the electrodes with hollow gold micropillars. Scaling up energy density by increasing active material thickness beyond 100 nm revealed some loss in surface area which highlighted the importance of nanoscale engineering for achieving maximum energy and power density in energy storage systems.

The crucial request for alternative clean energy technologies to replace conventional fossil fuels and drive technological advancement in consumer and wearable electronics, electric vehicles etc. has led to great advancement in electrochemical energy storage systems research. The lithium-ion battery possesses high energy density while the supercapacitor can guarantee high power density. However, modern technologies such as integrated solar and wind energy solutions require a blend of high energy and power density devices, which is a great challenge. Presently, there is increased research interest in aqueous hybrid supercapacitors, a device capable of combining the high energy density of rechargeable batteries and the high-power density of electric-double layer capacitors.The current hotspot of the hybrid supercapacitor research is the zinc-ion hybrid supercapacitor owing to its several advantages such as the abundance of Zinc resource over lithium, high theoretical capacity of Zn, double charge transfer compared to univalent Lithium, environmental safety and high energy/power density. Wang et al first reported the carbon zinc-ion hybrid supercapacitor in 2018 by directly using zinc foil as anode and bio-carbon as cathode to realize long stability up to 20000 cycles. Next, Dong et al also developed an activated carbon-based zinc-ion hybrid supercapacitor which achieved a high energy density of ~84 Wh kg-1 and power density of 14.9 kW kg-1 in a potential window of 0.2 – 1.8 V. Despite the rapid advances over a short period in this class of energy storage devices, some problems still exist. The coulombic efficiency of Zinc-ion hybrid supercapacitors is inferior in low-cost ZnSO4 electrolytes owing to side reactions between the electrolyte and the Zn anode, while the mass loading of commonly used carbon cathode is extremely low (less than 2 mg cm-2). Importantly, the charge storage mechanism in zinc-ion hybrid supercapacitors is unclear.In this work, we developed high performance zinc-ion hybrid supercapacitors with superior charge storage, improved rate capability, and high power and energy density using a high mass density carbon anode with superior capacitive/pseudocapacitive storage. We successfully reveal that the charge storage of zinc-ion hybrid supercapacitors is extensively limited in zinc sulfate electrolytes and successfully address the coulombic efficiency problem using by modifying the electrolyte. Finally, using techniques such as in-situ Raman spectroscopy and X-ray diffraction analysis, we probe the charge storage mechanism and unravel a double cation charge storage mechanism, resulting in high energy density and extended potential window. Finally, our work provides crucial insights into understanding the charge storage process of zinc-ion hybrid supercapacitors and designing hybrid supercapacitors with new material chemistries.

Introduction Since the introduction of lithium-ion batteries in 1990, the steady growth in volume and performance of lithium-ion cell components and batteries has demonstrated their strong demand in the high-energy-density energy-storage market. The commercial lithium-ion cells adopt the stable intercalation reaction to enable the reversible insertion of lithium ions between layered oxide cathodes and graphite anodes, resulting in the high energy density (100–350 Wh kg–1) and long-term cycling capability (1,000 cycles) that outperform other rechargeable batteries. However, after three decades of research, the charge-storage capacities of the electrode active materials are approaching their theoretical values (200–300 mAh g–1), while the cost of the electrode continues to increase. This limits the improvement of the energy density of lithium-ion cells, which has reduced the annual growth rate from 7% to 2%, making it difficult to supply the energy-storage market of more than 1,500 GWh in 2030. In response to these challenges, next-generation batteries are being developed, focusing on electrochemical cells to achieve high reversible energy storage and competitive prices and solid-state electrolytes for enhanced stability and improved energy density. Both developments aim at achieving new energy density records (300–500 Wh kg–1 and 700–800 Wh L–1) that would enable electric vehicles to surpass conventional vehicles in range, while reducing cell costs. Results and Discussion In this presentation, we will present the designs of the next-generation rechargeable cells aimed at overcoming the bottleneck faced by current commercial lithium-ion cells. From the materials science point of view, the lithium–sulfur battery is the most promising candidate because of its high energy density, low cost, and low toxicity. On the other hand, from the materials engineering point of view, the solid-state electrolytes with high ionic conductivity are proposed to increase the energy density, cyclability, and safety of the batteries through configuration modification. To adopt the advantages of these two novel battery technologies, we report an integrated design of the lithium–sulfur electrochemical cell with the solid-state electrolyte as a lithium–sulfur solid-state electrolyte cell. The lithium–sulfur electrochemical cell employs a high-sulfur-loading polysulfide cathode to achieve high energy density and to form a smooth ion-transfer interface between the catholyte and the solid-state electrolyte. On the other hand, the solid-state electrolyte provides excellent stability and safety to the cells by stabilizing the polysulfide cathode and protecting the lithium anode. The resulting cell design demonstrates the new battery materials and configurations, which include the development of a high-performance polysulfide cathode, the design and synthesis of solid-state electrolytes (i.e., polymer, oxide, and sulfide-based electrolytes), and the cell integration and interface analytical method. Our battery technologies enable the design of lithium–sulfur solid-state electrolyte batteries to achieve high sulfur loadings (4–16 mg cm–2) and high sulfur contents (50–80 wt%), which are better than those of current lithium–sulfur batteries that aim to be 5–10 mg cm–2 and 70 wt%. With the high sulfur loading, the lithium–sulfur solid-state electrolyte batteries exhibit high areal capacity (5–7 mA·h cm–2) and energy density (11–15 mW·h cm–2). Both values are higher than those of commercial lithium-ion cells for electric vehicles. Moreover, the cell has a long cyclability (100–200 cycles) and high rate capability (C/20 to 1C rate). Conclusion In summary, we report in the presentation a summary of our lithium–sulfur solid-state electrolyte batteries with a high-loading polysulfide cathode. The solid-state electrolytes stabilize the polysulfide cathode and the electrochemical reaction of lithium–sulfur batteries, while the stabilized polysulfide cathode forming a stable ionic conductive interface between the cathode and the solid-state electrolytes. Our lithium–sulfur solid-state electrolyte cells demonstrate outstanding battery-design parameters, excellent cell-performance values, and advanced interface analytical method. Both are essential for the commercial development of advanced next-generation rechargeable batteries. References L.-L. Chiu, S.-H. Chung, J. Mater. Chem. A 2022, 10, 13719.Y.-J. Yen, S.-H. Chung, J. Mater. Chem. A 2023, 11, 4519.Y.-C. Huang, B.-X. Ye, S.-H. Chung, RSC Adv. 2024, 14, 4025.

Novel Na0.5Bi0.5TiO3 based, lead-free energy storage ceramics with high power and energy density and excellent high-temperature stability

Developing dielectric capacitors with both a high power density and a high energy density for application in power electronics has been a long-standing challenge. Glass-ceramics offer the potential of retaining the high relative permittivity of ceramics and at the same time of exhibiting the high dielectric breakdown strength and fast charge/discharge rate of glasses, thus producing concurrently high power and energy densities in a single material. In this work, glass-ceramics are fabricated to achieve simultaneously high power and energy densities, high efficiency, and thermal stability by tuning the glass crystallization process via a suitable nucleating agent and a high oxygen partial pressure. Under the same practical charge-discharge test conditions, the as-prepared glass-ceramics combine the high energy density of ceramics and ultrafast discharge rate of glasses, producing the highest power density among glass- and ceramic-based dielectric materials. This work demonstrates the significant potential of achieving both high power and energy densities in glass-ceramics by optimizing the glass crystallization process.