For battery architectures that need a solid ion conductor with good contacting performance and high stability against electrochemical oxidation, polymerized ionic liquids (PIL) pose a valuable class of materials. The low conductivity of the binary PIL/ lithium salt system can be increased using a ternary ionic liquid acting as plasticiser. The conductive mechanism of the ternary system is however not fully understood. This work shows the shift in conduction mechanism for the ternary Li−/[1,3]PYR-/PDADMA-FSI system by increasing the lithium salt concentration and comparing the transfer mechanism to binary ionic liquid (IL) electrolyte analogues using pulsed field gradient (PFG) nuclear magnetic resonance (NMR), NMR relaxometry, Raman spectroscopy and electrochemical techniques. Two conducting regimes were found which show a strong trade-off between conductivity and transference number. In the low lithium salt regime (≤35 wt% LiFSI), cluster diffusion of aggregated lithium is the dominating mechanism leading to low transference numbers (0.04–0.15 at room temperature (RT)). The high salt regime (≥50 wt% LiFSI) shows diffusion through free lithium ion hopping transfer, which has a stronger dependence on temperature and yields higher transference numbers (0.31 at RT). Increasing lithium salt concentration shows an inverse linear correlation with conductivity. The electrochemical characteristics of ternary IL/PIL/lithium salt are shown to be highly tuneable by varying the lithium salt fraction, while it maintains excellent characteristics like processability, stability and mechanical function.

Sulfide-based solid-state batteries (SSBs) are emerging as a top contender for next-generation rechargeable batteries with improved safety and higher energy densities. However, SSBs with Ni-rich cathode materials such as LiNi0.82Mn0.07Co0.11O2 (NMC82) exhibit several chemomechanical challenges at the cathode–electrolyte interface, such as contact loss and solid-electrolyte decomposition, resulting in poor interfacial Li+ ion transport. To overcome these challenges, we used polymerized ionic liquids (PIL) as coatings at the NMC82 cathode surface, with and without incorporating a lithium salt. The thin Li+ ion-conductive Li–PIL nanocoating shows excellent compatibility with sulfide solid electrolytes and enables efficient Li+ transfer over the cathode–solid electrolyte interface, as demonstrated by 2D solid-state exchange NMR. It also improves contact retention between the cathode–solid electrolyte particles and mitigates electrolyte oxidation-induced degradation. This is reflected in the electrochemical performance of coated NMC82 in sulfide SSBs, where both a higher rate performance (190 mA h g−1 vs. 163 mA h g−1 for uncoated at 0.1C) and a remarkable capacity retention of 82.7% after 500 cycles at 0.2C and ambient conditions (20 °C) are observed. These results emphasize the effectiveness of PILs with Li salts as multifunctional coatings that enable high-performance sulfide-based SSBs with Ni-rich cathode materials at ambient temperature.

An integrated battery-electrolyzer stores renewable electricity as a battery and produces hydrogen when overcharged. This dual application requires electrode concepts that ideally enhance both battery and electrolysis operation without compromising either. One such concept is 3D structured electrodes including channels that improve ionic conductivity and material utilization as well as facilitating bubble removal during electrolysis. In this work, we first develop a 1D model of a porous sintered nickel electrode that takes the void fraction of the 3D geometry into account and allows for the determination of the current and potential distribution for both battery charging and oxygen evolution. An optimized void fraction that maximizes the reactive surface area for oxygen evolution is determined, and we discuss under what circumstances a 3D geometry is beneficial. Finally, we show how the improved ionic conductivity of 3D electrodes also results in more homogeneous battery charging, increasing charging efficiency in nickel electrodes.

Molecular catalysts play a significant role in chemical transformations, utilizing changes in redox states to facilitate reactions. To date molecular electrocatalysts have efficiently produced single-carbon products from CO2 but have struggled to achieve a carbon–carbon coupling step. Conversely, copper catalysts can enable carbon–carbon coupling, but lead to broad C2+ product spectra. Here we subvert the traditional redox-mediated reaction mechanisms of organometallic compounds through a heterogeneous nickel-supported iron tetraphenylporphyrin electrocatalyst, facilitating electrochemical carbon–carbon coupling to produce ethanol. This represents a marked behavioural shift compared with carbon-supported metalloporphyrins. Extending the approach to a three-dimensional porous nickel support with adsorbed iron tetraphenylporphyrin, we attain ethanol Faradaic efficiencies of 68% ± 3.2% at −0.3 V versus a reversible hydrogen electrode (pH 7.7) with partial ethanol current densities of −21 mA cm−2. Separately we demonstrate maintained ethanol production over 60 h of operation. Further consideration of the wide parameter space of molecular catalyst and metal electrodes shows promise for additional chemistries and achievable metrics.

A renewable power-based energy system will require both short- and long-term electricity storage and conversion to hydrogen-based fuels. This study investigates 3D electrodes for an integrated alkaline Ni-Fe battery and electrolyzer. The dual system can sustain current densities similar to those in alkaline electrolyzers while simultaneously reaching efficient hour-duration battery-storage capacities. We demonstrate that the combination of microporosity and a conductive three-dimensional (3D) electrode design with macroscopic channels enables the required current densities during charge, electrolysis, and discharge. The ionic conduction in the 3D electrode enables higher utilization of the active electrode mass and lower overpotentials during both the (dis)charge reaction and electrolysis. The double function of these electrodes is understood from a general statistical model and a more detailed porous-electrode model perspective. The 3D structuring provides a pathway forward, accessible with industrially established techniques, to these higher-power and higher-energy-density electrodes.

Increasing the electrode thickness, thereby reducing the proportion of inactive cell components, is one way to achieve higher-energy-density lithium-ion batteries. This, however, results in higher electronic and ionic overpotentials and/or mechanical failure induced by binder migration. Here, we report ethanol-induced phase inversion as an effective method for making high-mass-loading nickel-rich, layered oxide (LiNi0.8Mn0.1Co0.1O2 [NMC811]) electrodes. The ethanol-induced phase inversion electrodes significantly outperform their conventionally processed counterparts with similar loading (35 mg/cm2) and porosity (30%) in Li/NMC half-cells (131.7 mAh/g vs. 56.7 mAh/g) at 1C (7 mA/cm2) discharge. The binder structure induced by the nonsolvent improves the pore connectivity and results in lower tortuosity factors. The rapid solvent removal reduces the binder migration during drying, enabling ultrahigh active mass loadings up to 60 mg/cm2 (12 mAh/cm2). Further, the compatibility of the phase inversion process with current roll-to-roll coating setups makes this a processing technique with high industrial feasibility.

Electrochemical CO₂ reduction aims to compete with Power-to-X alternatives but is well behind the scales of water electrolyzers and thermochemical reactors. In a recent issue of Nature Chemical Engineering, Crandall and co-workers demonstrate a 1000 cm² tandem CO₂/CO electrolyzer for acetate production. The work invites discussion on scientific and engineering scale-up challenges.

Solid-state batteries with lithium metal anodes are considered the next major technology leap with respect to today’s lithium-ion batteries, as they promise a significant increase in energy density. Expectations for solid-state batteries from the automotive and aviation sectors are high, but their implementation in industrial production remains challenging. Here, we report a solid-state lithium–metal battery enabled by a polymer electrolyte consisting of a poly(DMADAFSI) cationic polymer and LiFSI in Pyr13FSI as plasticizer. The polymer electrolyte is infiltrated and solidified in the pores of a commercial LiNi0.8Mn0.1Co0.1O2 (NMC811) cathode with up to 2.8 mAh cm–2 nominal areal capacity and in the pores of a 25 μm thin commercial polypropylene separator. Cathode and separator are finally laminated into a cell in combination with a commercial 20 μm thin lithium metal anode. Our demonstration of a solid-state polymer battery cycling at full nominal capacity employing exclusively commercially available components available at industrial scale represents a critical step forward toward the commercialization of a competitive all-solid-state battery technology.

Electrochemical ammonia synthesis via the nitrogen reduction reaction (NRR) has been poised as one of the promising technologies for the sustainable production of green ammonia. In this work, we developed extensive process models of fully integrated electrochemical NH ₃ production plants at small scale (91 tonnes per day), including their techno-economic assessments, for (Li-)mediated, direct and indirect NRR pathways at ambient and elevated temperatures, which were compared with electrified and steam-methane reforming (SMR) Haber-Bosch processes. The levelized cost of ammonia (LCOA) of aqueous NRR at ambient conditions only becomes comparable with SMR Haber-Bosch at very optimistic electrolyzer performance parameters (FE > 80% at j ≥ 0.3 A cm ⁻²) and electricity prices (<$0.024 per kW h). Both high temperature NRR and Li-mediated NRR are not economically comparable within the tested variable ranges. High temperature NRR is very capital intensive due the requirement of a heat exchanger network, more auxiliary equipment and an additional water electrolyzer (considering the indirect route). For Li-mediated NRR, the high lithium plating potentials, ohmic losses and the requirement for H ₂, limits its commercial competitiveness with SMR Haber-Bosch. This incentivises the search for materials beyond lithium.

Ammonia is an indispensable commodity and a potential carbon free energy carrier. The use of H permeable electrodes to synthesize ammonia from N ₂, water and electricity, provides a promising alternative to the fossil fuel based Haber-Bosch process. Here, H permeable Ni electrodes are investigated in the operating temperature range 25–120 °C, and varying the rate of electrochemical atomic hydrogen permeation. At 120 °C, a steady reaction is achieved for over 12 h with 10 times higher cumulative NH ₃ production and almost 40-fold increase in faradaic efficiency compared to room temperature experiments. NH ₃ is formed with a cell potential of 1.4 V, corresponding to a minimum electrical energy investment of 6.6 kWh kg ⁻¹ (Figure presented.). The stable operation is attributed to a balanced control over the population of N, NH _x and H species at the catalyst surface. These findings extend the understanding on the mechanisms involved in the nitrogen reduction reaction and may facilitate the development of an efficient green ammonia synthesis process.

The electrochemical dinitrogen reduction reaction (NRR) has recently gained much interest as it can potentially produce ammonia from renewable intermittent electricity and replace the Haber-Bosch process. Previous literature studies report Fe- and Mo-carbides as promising electrocatalysts for the NRR with activities higher than other metals. However, recent understanding of extraneous ammonia and nitrogen oxide contaminations have challenged previously published results. Here, we critically assess the NRR performance of several Fe- and Mo-carbides reported as promising by implementing a strict experimental protocol to minimize the effect of impurities. The successful synthesis of α-Mo₂C decorated carbon nanosheets, α-Mo₂C nanoparticles, θ-Fe₃C nanoparticles, and χ-Fe₅C₂ nanoparticles was confirmed by X-ray diffraction, scanning and transmission electron microscopy, and X-ray photoelectron and Mössbauer spectroscopy. After performing NRR chronoamperometric tests with the synthesized materials, the ammonia concentrations varied between 37 and 124 ppb and are in close proximity with the estimated ammonia background level. Notwithstanding the impracticality of these extremely low ammonia yields, the observed ammonia did not originate from the electrochemical nitrogen reduction but from unavoidable extraneous ammonia and NO_x impurities. These findings are in contradiction with earlier literature studies and show that these carbide materials are not active for the NRR under the employed conditions. This further emphasizes the importance of a strict protocol in order to distinguish between a promising NRR catalyst and a false positive.

Nanostructured solid composite electrolyte or nano-SCE, which is composed of an ionic liquid, nanoporous silica, and residuals of immobilized precursor components, shows promising synergistic properties. The ionic conductivity of nano-SCE is in the range of 2–5 mS cm⁻¹, which exceeds the bulk ionic liquid conductivity at ambient temperature, while maintaining characteristics of a solid electrolyte such as having no leakage issues as the ionic liquid is confined, and lower flammability compared to conventional liquid electrolytes. In this study, the underlying mechanism of enhanced conductivity is investigated by using magic angle spinning NMR and NMR relaxometry analysis. Water, one of the volatile precursor molecules has shown to play a key role in the final conductivity and stability at the solid-electrolyte interface, as it enhances the temperature range in which the ionic liquid remains mobile. In line with previous studies, water with lowered mobility is found in the silicon matrix. The activation energies of lithium ion transfer probed by NMR relaxometry, however, do not change as function of water content. The increase in bulk mobility of lithium ions under ambient conditions compared to water-less nano-SCE is found to be the origin of the altered conductivity of this material.

Hydrogen permeable electrodes can be utilized for electrolytic ammonia synthesis from dinitrogen, water, and renewable electricity under ambient conditions, providing a promising route toward sustainable ammonia. The understanding of the interactions of adsorbing N and permeating H at the catalytic interface is a critical step toward the optimization of this NH3 synthesis process. In this study, we conducted a unique in situ near ambient pressure X-ray photoelectron spectroscopy experiment to investigate the solid-gas interface of a Ni hydrogen permeable electrode under conditions relevant for ammonia synthesis. Here, we show that the formation of a Ni oxide surface layer blocks the chemisorption of gaseous dinitrogen. However, the Ni 2p and O 1s XPS spectra reveal that electrochemically driven permeating atomic hydrogen effectively reduces the Ni surface at ambient temperature, while H2 does not. Nitrogen gas chemisorbs on the generated metallic sites, followed by hydrogenation via permeating H, as adsorbed N and NH3 are found on the Ni surface. Our findings suggest that the first hydrogenation step to NH and the NH3 desorption might be limiting under the operating conditions. The study was then extended to Fe and Ru surfaces. The formation of surface oxide and nitride species on iron blocks the H permeation and prevents the reaction to advance; while on ruthenium, the stronger Ru-N bond might favor the recombination of permeating hydrogen to H2 over the hydrogenation of adsorbed nitrogen. This work provides insightful results to aid the rational design of efficient electrolytic NH3 synthesis processes based on but not limited to hydrogen permeable electrodes.

The nitrogen reduction reaction (NRR) is a promising pathway toward the decarbonization of ammonia (NH3) production. However, unless practical challenges related to the detection of NH3 are removed, confidence in published data and experimental throughput will remain low for experiments in aqueous electrolyte. In this perspective, we analyze these challenges from a system and instrumentation perspective. Through our analysis we show that detection challenges can be strongly reduced by switching from an Hcell to a gas diffusion electrode (GDE) cell design as a catalyst testing platform. Specifically, a GDE cell design is anticipated to allow for a reduction in the cost of crucial 15N2 control experiments from €100−2000 to less than €10. A major driver is the possibility to reduce the 15N2 flow rate to less than 1 mL/min, which is prohibited by an inevitable drop in mass-transport at low flow rates in H-cells. Higher active surface areas and improved mass transport can further circumvent losses of NRR selectivity to competing reactions. Additionally, obstacles often encountered when trying to transfer activity and selectivity data recorded at low current density in Hcells to commercial device level can be avoided by testing catalysts under conditions close to those in commercial devices from the start.

The electrochemical nitrogen reduction reaction (NRR) is a promising alternative to the current greenhouse gas emission intensive process to produce ammonia (NH₃) from nitrogen (N₂). However, finding an electrocatalyst that promotes NRR over the competing hydrogen evolution reaction (HER) has proven to be difficult. This difficulty could potentially be addressed by accelerating the electrocatalyst development for NRR by orders of magnitude using high-throughput (HTP) workflows. In this work, we developed a HTP gas diffusion electrode (GDE) cell to screen up to 16 electrocatalysts in parallel. The key innovation of the cell is the use of expanded Polytetrafluoroethylene (ePTFE) gas diffusion layers (GDL) which simplifies the handling of catalyst arrays compared to carbon fabrics and enables sufficient N₂ mass transport. We demonstrate the robustness of the HTP workflow by screening 528 bimetallic catalysts of composition AB (A,B = Ag, Al, Au, Co, Cu, Fe, Mn, Mo, Ni, Pd, Re, Ru, W) for NRR activity. None of the materials produced ammonia significantly over background level which emphasizes the difficulty of finding active electrocatalysts for NRR and narrows down the search space for future studies.

Rapid advances in electrocatalytic ammonia synthesis are impeded by laborious detection methods commonly used in the field and by constant risk of external contaminations, which generates misleading false positives. We developed a facile real-time GC-MS method for sensitive isotope NH3 quantification, requiring no external sample manipulations. This method ensures high detection reliability paramount to accelerate (electro-)catalyst screening.

Direct electrochemical nitrogen reduction holds the promise of enabling the production of carbon emission-free ammonia, which is an important intermediate in the fertilizer industry and a potential green energy carrier. Here we show a strategy for ambient condition ammonia synthesis using a hydrogen permeable nickel membrane/electrode that spatially separates the electrolyte and hydrogen reduction side from the dinitrogen activation and hydrogenation sites. Gaseous ammonia is produced catalytically in the absence of electrolyte via hydrogenation of adsorbed nitrogen by electrochemically permeating atomic hydrogen from water reduction. Dinitrogen activation at the polycrystalline nickel surface is confirmed with 15N2 isotope labeling experiments, and it is attributed to a Mars-van Krevelen mechanism enabled by the formation of N-vacancies upon hydrogenation of surface nitrides. We further show that gaseous hydrogen does not hydrogenate the adsorbed nitrogen, strengthening the benefit of having an atomic hydrogen permeable electrode. The proposed approach opens new directions toward green ammonia.

The transition to renewable electricity sources and green feedstock implies the development of electricity storage and conversion systems to both stabilise the electricity grid and provide electrolytic hydrogen. We have recently introduced the concept of a hybrid Ni/Fe battery-electrolyser (battolyser) for this application1. The hydrogen produced during the Ni/Fe cell charge and continued electrolysis can serve as chemical feedstock and a fuel for long-term storage, while the hybrid battery electrodes provide short term storage. Here, we present Ni-Fe layered double hydroxides (NiFe-LDHs) for enhancing the positive electrode performance. The modified Ni(OH)2 material capacity, high rate performance and stability have been tested over a large range of charge rates (from 0.1C to 20C) over 1000 cycles. The Ni-Fe layered double hydroxides allow the capacity per nickel atom to be multiplied by 1.8 in comparison to the conventional β-Ni(OH)2 material which suggests that the nickel content can be reduced by 45% for the same capacity. This reduction of the nickel content is extremely important as this presents the most costly resource. In addition, Fe doped Ni(OH)2 shows improved ionic and electronic conductivity, OER catalytic activity outperforming the benchmark (Ir/C) catalyst, and long term cycling stability. The implementation of this Fe doped Ni(OH)2 material in the Ni/Fe hybrid battery-electrolyser will bring both electrolysis and battery function forward at reduced material cost and energy loss.

Both daily and seasonal fluctuations of renewable power sources will require large-scale energy storage technologies. A recently developed integrated battery and electrolyzer system, called battolyser, fulfills both time-scale requirements. Here, we develop a macroscopic COMSOL Multiphysics model to quantify the energetic efficiency of the battolyser prototype that, for the first time, integrates the functionality of a nickel-iron battery and an alkaline electrolyzer. The current prototype has a rated capacity of 5 Ah, and to develop a larger, enhanced system, it is necessary to characterize the processes occurring within the battolyser and to optimize the individual components of the battolyser. Therefore, there is a need for a model that can provide a fast screening on how the properties of individual components influence the overall energy efficiency of the battolyser prototype. The model is validated using experimental results, and new configurations are compared, and the energy efficiency is optimized for the scale-up of this lab-scale device. Based on the modeling work, we find an optimum electrode thickness for the nickel electrode of 3 and 2.25 mm for the iron electrode with optimal electrode porosities in the range of void fraction of 0.15-0.35. Additionally, electrolyte conductivity and the gap thickness are found to have a small effect on the overall efficiency of the device.