Electrochemical hydrogen production is central to future renewable energy systems, yet conventional water electrolyzers tightly couple electricity supply and hydrogen generation, limiting operational flexibility and increasing system cost. Decoupled water electrolysis offers an alternative architecture by separating the hydrogen and oxygen evolution reactions in time or space, enabling simultaneous energy storage and on-demand hydrogen production. A promising implementation is the Zn-H2 hybrid electrolysis concept, where water oxidation is coupled to zinc deposition during charging and hydrogen evolution occurs during discharge. However, its viability critically depends on bifunctional gas-evolving electrodes capable of repeatedly switching between the hydrogen evolution reaction (HER) and oxygen evolution reaction (OER) in highly alkaline, zinc-containing electrolyte, an extreme and largely unexplored regime. Here we report robust, noble-metal-free catalyst coatings based on transition-metal-modified steel that enable stable HER <-> OER cycling under realistic Zn-H2 electrolysis conditions. By systematically comparing electrodeposition and microwave-assisted solvothermal synthesis, we identify nanostructured cobalt coatings grown directly on low-carbon steel as a highly active and durable bifunctional catalyst platform. These electrodes sustain catalytic activity during repeated HER/OER switching and maintain performance even in concentrated alkaline electrolyte saturated with ZnO, where conventional coatings rapidly degrade. Electrochemical measurements during cycling indicate dynamic changes in catalytic behavior, while ex situ surface characterization before and after HER and OER operation reveals the formation of a cobalt oxyhydroxide phase associated with OER activity alongside metallic cobalt sites that promote HER. This combination enables efficient bifunctional operation. The optimized electrodes show strong resistance to dissolution and minimal susceptibility to zinc interference. These findings establish a scalable catalyst design strategy for decoupled Zn-H2 electrolysis and demonstrate stable bifunctional electrocatalysis under realistic Zn-rich alkaline cycling conditions, advancing integrated hydrogen production and electrochemical energy storage technologies.

The surge in demand for electronic gadgets, electric vehicles, and grid storage necessitates safer and more energy-dense batteries. Traditional lithium-ion batteries (LIBs) with liquid electrolytes offer high ionic conductivity (similar to 10(-3)S/cm) but face risks like flammability and leakage. Solid-state electrolytes (SSEs) emerge as promising alternatives, minimizing safety concerns and improving performance. This study introduces a tape-casting technique to produce stable and flexible quasi-hybrid polymer electrolytes (QHPEs) for lithium-ion batteries. These membranes integrate Poly (vinylidene fluoride-co-hexa-fluoropropylene) (PVDF-HFP) as a polymer matrix, a single-ion conducting polymer (SICs), and Ta-doped LLZO for enhanced mechanical stability and ionic conductivity. The addition of plasticizers is also explored to increase the ionic conductivity, addressing the low ionic conductivity of SICs at room temperature despite their high lithium transference number approaching unity. These plasticizers ethylene carbonate/propylene carbonate (EC/PC) remain inside the QHPE membrane, facilitating lithium-ion transport and thereby enhancing overall performance Comprehensive thermal, structural, and electrochemical characterization techniques validate their performance. The optimized QHPE exhibits good ionic conductivity (0.11 mS/cm at 25 degrees C), a broad electrochemical voltage window up to 4.5V (j <= 0.01mAcm(-2)), and very good cycling stability (146 mAh/g at 1C, retaining 84.2 % capacity after 250 cycles). Compatibility with lithium metal electrodes and successful integration with various cathode materials like LiFePO4 (LFP), NMC811, and NCA highlight the potential of these membranes for advanced battery applications.

With the growing shift towards renewable energy sources, it has become significantly more urgent to explore and develop new energy storage solutions with high capacity, abundant materials and low cost. Conventional electrochemical storage systems (batteries) have been developed rapidly, but only pose as a partial solution due to their still low storage density and high cost.[1] Hydrogen occupies a key position within the energy transition attributable to its high storage density (33.33 kWh/kg) and its wide use as energy storage and as an essential raw material in industry.[2] However, two of the main problems are high investment costs and high cost of stored electricity due to the low efficiency of the conversion chain.[3] Both of these problems could be significantly improved by a new approach as described by Hahn et al. combining the functionalities of a battery and an electrolyzer. In this concept (see Fig. 1), water is oxidized to oxygen at the gas electrode during charging and zinc oxide is reduced to metallic zinc at the counter electrode. When the storage cell is being discharged as required, zinc is converted back to zinc oxide and water is reduced at the gas evolution electrode to produce hydrogen with an efficiency near 80%.[4][5] Due to the very low material costs of the galvanic Zn cell as well as the high energy density of the deposited zinc of 820Ah/kg and thus low overall dimensions, the capital costs can be reduced significantly.[6] At the core of this concept, we are working on the development of a noble-metal free bifunctional catalyst for the gas evolution electrode, realizing both hydrogen generation and oxygen generation over thousands of cycles. For this we applied multiple synthesis methods (microwave-assisted solvothermal synthesis, spray-coating technique, electrodeposition) to achieve various steel substrate-based catalysts doped with different metals (Ni, Co, Mo). The best results in terms of activity, overpotential and stability have been achieved using the microwave-assisted solvothermal synthesis. Apart from electrochemical activity and stability tests, simulating hundreds of charge and discharge cycles, we used microscopic and spectroscopic characterization methods such as SEM-EDX, thin-film XRD and ICP-OES. [1] ENERGY STORAGE ASSOCIATION. Hydrogen Energy Storage - Energy Storage Association. 4/8/2021. Available also from http://energystorageassociationarchive.org/why-energy-storage/technologies/hydrogen-energy-storage/ [2] LUDWIG-BÖLKOW-SYSTEMTECHNIK GMBH. H2data.de - Hydrogen fact sheet. 2/12/2021. Available also from: http://www.h2data.de/. [3] BREEZE, P. Chapter 8 - Hydrogen Energy Storage. In: BREEZE, P. (ed.). Power system energy storage technologies. London: Elsevier, AP, Academic Press, 2018, pp. 69–77. The power generation series. ISBN 978-0-12-812902-9. Available from doi: 10.1016/B978-0-12-812902-9.00008-0. [4] Robert Hahn, Andreas Gabler, Axel Thoma, Fabian Glaw, K.-D. Lang, Small fuel cell system with cartridges for controlled hydrogen generation. Int. Journal of Hydrogen Energy 40 (2015) pp. 5340-5345 [5] Robert Hahn, Oren Rosenfeld, Chaim Markheim, Andreas Schamel, The Zn-H2 storage system, Fuel Cells, Electrolysers & H2 Processing, EFCF 2023, 4-7 July 2023 Lucerne, to be published in Fuel Cells 2024 [6] RUAN, P. et al. Design Strategies for High-Energy-Density Aqueous Zinc Batteries. Angewandte Chemie International Edition. 2022, vol. 61, no. 17, e202200598. issn 1521-3773. Available from doi: 10.1002/ anie.202200598. Figure 1

A novel electrically chargeable galvanic system is presented that efficiently stores energy in the form of zinc and releases hydrogen and electricity upon discharge. In this concept, oxygen is released at the gas electrode during charging, and zinc oxide is reduced to metallic zinc at the counter electrode. When the cell is discharged on demand, the zinc is converted back to zinc oxide, but the water is reduced at the gas electrode to produce hydrogen. The system can therefore be used not only to store electricity-in combination with a fuel cell-but also as an on-demand hydrogen generator, for example, for industrial use. When used as an electrical storage system, the overall round-trip efficiency can approach 50%, significantly exceeding the efficiency of alternative power-to-gas technologies. There are no hydrogen storage or transportation losses. The electrochemical cell combines two breakthrough technologies: a bifunctional catalyst for hydrogen and oxygen evolution reaction that survives thousands of oxidation and reduction cycles, and a dendrite-free deposition of thick, high-capacity zinc coatings that can be cycled almost indefinitely thanks to pulsed charge current and intelligent electronic control.

We introduce a manufacturing concept of variable capacity energy harvesters consisting of macroporous springs integrated within a conducting silicone rubber and dielectric. Printing and polymerising emulsion templates resulted in macroporous spring elements, which were coated with conducting silicone rubber to maintain the active contact surface. By increasing size and number of these springs, the capacitance change of the energy harvesters during compression and recovery increased from 0.4 nF/cm2 to 0.8 nF/cm2. During cyclic loading with 30N at 2Hz, the energy harvesters with macroporous springs delivered a power density of 0.58µW/cm2 at a bias voltage of 50V, which was 25 times higher than the control without springs. The energy harvesters provided a constant power output over three hours of cyclic loading (21,600 cycles), indicating their structural stability and the durability of the macroporous springs.

Although lithium-ion batteries are playing a paramount role in everyday life around the world, from portable electronics to electric vehicles, there seems to be no international organization governing its development since the commercialization began in 1991. As a consequence, there is no clearly defined nomenclature for certain aspects of lithium-ion batteries. For instance, no international consensus has been reached on the nomenclature of the interphases that play a very crucial role in the operation of lithium-ion batteries. Unfortunately, this absence of proper nomenclature for interphases has been trending for far too long and it is confusing for emerging scientists, especially as it is being dragged to emerging technologies such as solid-state batteries and post-lithium chemistries. Here, the nomenclature problem of the interphases in lithium-ion batteries is critically addressed.

The process of anion intercalation in graphite and its reversibility plays a crucial role in the next generation energy-storage devices. Herein the reaction mechanism of the aluminum graphite dual ion cell by operando X-ray scattering from small angles to wide angles is investigated. The staging behavior of the graphite intercalation compound (GIC) formation, its phase transitions, and its reversible process are observed for the first time by directly measuring the repeated intercalation distance, along with the microporosity of the cathode graphite. The investigation demonstrates complete reversibility of the electrochemical intercalation process, alongside nano- and micro-structural reorganization of natural graphite induced by intercalation. This work represents a new insight into thermodynamic aspects taking place during intermediate phase transitions in the GIC formation.

Mechanical energy harvesting devices can scavenge low-frequency energy from regular biomotion. Here, the harvester exploits printed nanocomposite dielectric inks in combination with commercial conductive elastomers to produce a low-cost, high-performance embodiment of a variable capacitance mechanism device.

Herein, the use of a gel polymer electrolyte (GPE) comprising polyacrylonitrile and 1‐ethyl‐3‐methylimidazolium chloride:aluminum trichloride (EMIMCl:AlCl 3 ) ionic liquid in aluminum batteries is investigated. The investigated GPE is characterized in terms of conduction properties. The obtained ionic conductivity values are suitable for battery applications. The ability of the GPE to sustain an efficient aluminum stripping deposition process is verified, revealing the need of a swelling process to enable the aluminum plating/stripping. The mitigation of the chloroaluminate corrosivity in the GPE is confirmed by evaluating the corrosion current of stainless steel 316 current collectors. The long‐term ability of GPE to sustain the stripping deposition process is tested, evidencing a good Al/GPE interface stability. Finally, the GPE electrolyte suitability in the Al battery is verified by assembling an Al/GPE/pyrolytic graphite (PG) cell. The test cell shows a good cycling ability, demonstrating the suitability of the GPE electrolyte for the realization of aluminum batteries.

Herein, we report a comparison of aluminum graphite dual-ion cells (AGDICs) electrochemical characteristics employing the conventional 1-ethyl-3-methylimidazolium chloride:aluminum trichloride (EMIMCl : AlCl3) electrolyte and two popular deep eutectic solvents (DESs), namely urea : AlCl3 and acetamide:AlCl3. The three electrolytes ' characteristics have been evaluated in terms of Al-stripping deposition capability and cycling behavior in AGDICs. The results evidence the EMIMCl : AlCl3 ' s Al-stripping deposition and rate capability in AGDICs superior characteristics addressed to the lower viscosity and higher conductivity with respect to the urea : AlCl3 and acetamide:AlCl3. On the other hand, the urea : AlCl3 guarantees a much higher columbic efficiency in AGDICs, thanks to the superior electrochemical window stability.

Rechargeable graphite dual-ion batteries are extremely appealing for grid-level stationary storage of electricity, thanks to the low-cost and high-performance metrics, such as high-power density, energy efficiency, long cycling life, and good energy density. An in-depth understanding of the anion intercalation mechanism in graphite is fundamental for the design of highly efficient systems. In this work, a comparison is presented between pyrolytic (PG) and natural (NG) graphite as positive electrode materials in rechargeable aluminum batteries, employing an ionic liquid electrolyte. The two systems are characterized by operando synchrotron energy-dispersive X-ray diffraction and time-resolved computed tomography simultaneously, establishing a powerful characterization methodology, which can also be applied more in general to carbon-based energy-related materials. A more in-depth insight into the AlCl4-/graphite intercalation mechanism is obtained, evidencing a mixed-staged region in the initial phase and a two-staged region in the second phase. Moreover, strain analysis suggests a correlation between the irreversibility of the PG electrode and the increase of the inhomogenous strain. Finally, the imaging analysis reveals the influence of graphite morphology in the electrode volume expansion upon cycling.

For the first time, electrophoretic deposition (EPD) has been employed to prepare a self-supported, inorganic membrane consisting of SiO2 nano-fibers, as a separator for lithium-ion batteries. The SiO2 nano-fibers that were fabricated by a low-cost force spinning technique were deposited by EPD directly onto LiNi0.8Co0.15Al0.05O2 cathode material. Citric acid charging agent and anhydrous acetone solvent were used. The resulting porosity and tortuosity of the EPD SiO2 separator were 71.42 %, and 1.70, respectively. The slightly higher tortuosity of the EPD-SiO2-fiber separator (60 mu m) led to a lower rate capability in comparison to commercial GF/A glass fiber separator (260 mu m). On the other hand, the latter exhibited lower self-discharge than the former in full-cells with a graphite anode; this is proposed to be related to the different purities of the two materials that impart different electronic properties or the presence of 20 wt % PVDF in the EPD-SiO2 separator. Indeed, the deposited membrane has good characteristics as a battery separator and the EPD process is extremely feasible for the fabrication of miniaturized lithium-ion batteries on wafer level.

A cost effective and reliable technology for the fabrication of electrochemical test-cell arrays for battery materials research, based on batch-fabricated glass micro packages was developed and tested. Jet dispensing was investigated for the first time as a process for fabricating battery electrode arrays and separators and compared to micro dispense printing. The process shows the reproducibility over the whole range of investigated materials and battery cell structures that is required for battery materials research. Such setup gives rise to a significantly improved reliability and reproducibility of electrochemical experiments. Cost-effective fabrication of our test chips by batch processing allows for their single-use in electrochemical experiments, thereby preventing contamination issues due to repeated use as in conventional laboratory test cells. In addition, the integration of micro pseudo reference electrodes is demonstrated. Thus, the test cell array together with the developed electrode/electrolyte deposition technology provide a highly efficient tool for speedy combinatorial and high throughput testing of battery materials on a system level (full cell tests). Experimental results are shown for the microfabrication of lithium-ion test cells with help of several electrode and binder materials. The influence of jetting parameters on electrode lateral dimensions and thickness, reproducibility of the electrode mass as well as the use of integrated micro-reference electrodes for impedance spectroscopy and cyclic voltammetry measurements in micro cells are presented in detail.

This work presents an enhanced hydrometallurgical process for recycling lithium ion batteries. First, endof-life batteries were processed in a physical pre-treatment plant to obtain a representative electrode material. The resulting leachate was purified forth by iron-precipitation, liquid–liquid extractions, and an innovative Li–Na separation, in order to obtain valuable products. These products include high-grade graphite, cobalt oxide(Co 3 O 4 , purity 83%), cobalt oxalate(CoC 2 O 4 , purity 96%), nickel oxide(Ni O, purity89%), and lithium carbonate(Li 2 CO 3 , purity 99.8%). The recovery rate was quantitative for graphite, between 80% and 85% for cobalt depending on the nature of the recovery method, 90% for nickel, and 72%for lithium. Secondary streams were also valorized to obtain sodium sulfate(Na 2 SO 4 , purity 96%), and MnCoFe 2 O 4 magnetic nano-sorbents according to the zero-waste concept. In order to close the loop, recycled Co 3 O 4 and NiO were used as conversion-type anode materials for advanced lithium ion batteries showing promising performances.

A high-performance Al/graphite battery has been investigated, employing a natural graphite cathode (NG) and 1-ethyl-3methylimidazolium chloride (EMIMCl):AlCl3 as electrolyte. The employed graphite is characterized by excellent reversibility as revealed by electrochemical tests and ex-situ XRD. The Al/EMIMCl:AlCl3/NG battery showed extraordinary performance in terms of rate capability, and cycle life. The cell delivered a capacity of 110 mAhg(-1) at lower current values, retaining 90% and 60% of the capacity employing a current of 20 Ag-1 and 50 Ag-1, respectively (i. e., a complete charge-discharge cycle in 35 and 9 seconds, respectively). Furthermore, the cycling test performed using a current of 20 Ag-1 revealed an extremely long calendar life of half million of cycles. The practical applicability of the investigated Al/graphite system has been ascertained; this involved estimating the energy efficiency as a function of current rate and carefully calculating the practical energy densities that can be obtained from the system.

A cost-effective and reliable technology allowing extreme miniaturization of batteries into glass chips and electronic packages has been developed, employing a dispense-print process for battery electrodes and liquid electrolyte. Lithium-ion micro-batteries (active area 6 × 8 mm2, 0.15–0.3 mAh) with interdigitated electrodes were fabricated, tested and finally compared with the traditional battery architecture of stacked electrodes. Commercial graphite and lithium titanate anode as well as layered nickel cathode materials were used. All the processes for the micro-battery fabrication were established during this work; in particular the micro fluidic electrolyte filling process that allows simultaneous electrolyte supply to all cells on a planar substrate. Electrode mass reproducibility was sufficient for adequate electrode balancing. Current capability similar to the conventional face-to-face electrode configuration was achieved with interdigital electrodes that can be fabricated much easily on a substrate level. The cells were successfully cycled; several 100 cycles can be achieved. Additional results of life-time characteristics and electrochemical impedance spectroscopy are presented as well. These rechargeable micro-batteries can be used for future extremely miniaturized electronic products.

Herein we report on a detailed investigation of the irreversible capacity in the first cycle of pyrolytic graphite electrodes in aluminum batteries employing 1-ethyl-3-methylimidazolium chloride:aluminum trichloride (EMIMCl:AlCl3) as electrolyte. The reaction mechanism, involving the intercalation of AlCl4 in graphite, has been fully characterized by correlating the micro/nanostructural modification to the electrochemical performance. To achieve this aim a combination of X-ray diffraction (XRD), small angle X-ray scattering (SAXS) and computed tomography (CT) has been used. The reported results evidence that the irreversibility is caused by a very large decrease in the porosity, which consequently leads to microstructural changes resulting in the trapping of ions in the graphite. A powerful characterization methodology is established, which can also be applied more generally to carbon-based energy-related materials. Introduction

ADVERTISEMENT RETURN TO ISSUEPREVViewpointNEXTAttainable Energy Density of MicrobatteriesNeil A. Kyeremateng*Neil A. KyerematengMicro Energy Storage Group, Research Center for Microperipheric Technologies, Technical University of Berlin, 13355 Berlin, Germany*E-mail: [email protected] (N.A.K.).More by Neil A. Kyerematenghttp://orcid.org/0000-0003-0122-1692 and Robert Hahn*Robert HahnMicro Energy Storage Group, Fraunhofer Institut für Zuverlässigkeit und Mikrointegration (IZM), 13355 Berlin, Germany*E-mail: [email protected] (R.H.).More by Robert HahnCite this: ACS Energy Lett. 2018, 3, 5, 1172–1175Publication Date (Web):April 25, 2018Publication History Received27 March 2018Accepted17 April 2018Published online25 April 2018Published inissue 11 May 2018https://pubs.acs.org/doi/10.1021/acsenergylett.8b00500https://doi.org/10.1021/acsenergylett.8b00500article-commentaryACS PublicationsCopyright © 2018 American Chemical Society. This publication is available under these Terms of Use. Request reuse permissions This publication is free to access through this site. Learn MoreArticle Views2707Altmetric-Citations53LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InRedditEmail PDF (756 KB) Get e-AlertscloseSupporting Info (1)»Supporting Information Supporting Information SUBJECTS:Batteries,Electrochemical cells,Electrodes,Electrolytes,Energy density Get e-Alerts

Herein we report a novel study on the reaction mechanism of non-aqueous aluminum/graphite cell chemistry employing 1-ethyl-3-methylimidazolium chloride:aluminum trichloride (EMIMCl:AlCl3) as the electrolyte.