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LiMn2O4 is a battery cathode material with desirable properties such as low cost, low toxicity, high natural abundance of Mn, and environmental compatibility. By means of first-principles calculations, we study the structural, magnetic, and electronic properties of LiMn2O4 under ambient conditions and high hydrostatic pressures (until 20 GPa). We obtain two oxidation states for Mn, even using a cubic structure, which differ in all analyzed properties: structural, electronic, and magnetic. At P > 0, such properties were found to display a standard behavior decreasing smoothly and linearly with pressure. Furthermore, the enthalpy of cubic and orthorhombic structures under low and high-pressure conditions were examined, showing that no cubic to orthorhombic phase transition exists in all the investigated pressure range, nor is a magnetic cubic to a non-magnetic cubic phase transition possible.

There is an increasing need for sustainable energy storage solutions as fossil fuels are replaced by renewable energy sources. Multivalent batteries, specifically Mg batteries, are one energy storage technology that researchers continue to develop with hopes to surpass the performance of Li-ion batteries. However, the limited energy density and transport properties of Mg cathodes remain critical challenges preventing the realization of high-performance multivalent batteries. In this work, ABO4 zircon materials (A = Y, Eu and B = V, Cr) are computationally and experimentally evaluated as Mg intercalation cathodes. Remarkably good Mg-ion transport properties were predicted and Mg-ion intercalation was experimentally verified in sol-gel synthesized zircon YVO4, EuVO4, and EuCrO4. Among them, EuVO4 exhibited the best electrochemical performance and demonstrated repeated reversible cycling. While we believe that the one-dimensional diffusion channels and redox-active species tetragonal coordination limit the value of many zircons as high-performance cathodes, their unique structural motif of overlapping polyhedra along the diffusion pathway appears instrumental for promoting good Mg-ion mobility. The motif results in a favorable "6-5-4" change in coordination that avoids unfavorable sites with lower coordination along the diffusion pathway and a structural design metric for future Mg cathode development.

©Pergamon-Elsevier Science Ltd.. We acknowledge partial financial support of this work by Spanish Ministerio de Economía y Competitividad (project MAT2011-28751-C02). Alicia Prados acknowledges financial support from Ministerio de Educación of Spain (FPU program) and acknowledges the useful discussions on this work with Dr. Ángela Llavona., Bismuth ultra-thin films grown on n-GaAs electrodes via electrodeposition are porous due to a blockade of the electrode surface caused by adsorbed hydrogen when using acidic electrolytes. In this study, we discuss the existence of two sources of hydrogen adsorption and e propose different routes to unblock the n-GaAs surface in order to improve Bi films compactness. Firstly, we demonstrate that increasing the electrolyte temperature provides ompact yet polycrystalline Bi films. Cyclic voltammetry scans indicate that this low crystal quality might be a result of the incorporation ofBi hydroxides within the Bi film as a result of the temperature increase. Secondly, we have illuminated the semiconductor surface to take advantage of photogenerated holes. These photocarriers oxidize the adsorbed hydrogen nblocking the surface, but also create pits at the substrate surface that degrade the Bi/GaAs interface and prevent an epitaxial growth. Finally, we show that performing a cyclic voltammetry scan before electrodeposition enables the growth of compact Bi ultra-thin films of high crystallinity on semiconductor substrates with a doping level low enough to perform transport measurements., Ministerio de Economía y Competitividad (MINECO), Ministerio de Educacion (Spain), Depto. de Física de Materiales, Fac. de Ciencias Físicas, TRUE, pub

As concerns about the availability of mineral resources for lithium-ion batteries (LIBs) arise and demands for large-scale energy storage systems rapidly increase, non-LIB technologies have been extensively explored as low-cost alternatives. Among the various candidates, sodium-ion batteries (SIBs) have been the most widely studied, as they avoid the use of expensive and less abundant elements such as lithium, cobalt, and nickel while also sharing similar operating principles with LIBs. In this Perspective, we discuss why SIBs hold great promise and can act as competitors to lithium-ion technology. In addition, the remaining challenges and future research directions are highlighted, focusing on cathode developments and the use of SIBs in large-scale applications, including electric vehicles and stationary energy storage.

Cathode degradation of Li-ion batteries (Li+) continues to be a crucial issue for higher energy density. A main cause of this degradation is strain due to stress induced by structural changes according to the state-of-charge (SOC). Moreover, in solid-state batteries, a mismatch between incompatible cathode/electrolyte interfaces also generates a strain effect. In this respect, understanding the effects of the mechanical/elastic phenomena associated with SOC on the cathode performance, such as voltage and Li+ diffusion, is essential. In this work, we focused on LiCoO2 (LCO), a representative LIB cathode material, and investigated the effects of biaxial strain and hydrostatic pressure on its layered structure and Li+ transport properties through first-principles calculations. With the nudged elastic band technique and molecular dynamics, we demonstrated that in Li-deficient LCO, compressive biaxial strain increases the Li+ diffusivity, whereas tensile biaxial strain and hydrostatic pressure tend to suppress it. Structural parameter analysis revealed the key correlation of "Co layer distances" with Li+ diffusion instead of "Li layer distances", as ordinarily expected. Structural analysis further revealed the interplay between the Li-Li Coulomb interaction, SOC, and Li+ diffusion in LCO. The activation volume of LCO under hydrostatic pressure was reported for the first time. Moreover, vacancy formation energy calculations showed that the Li intercalation potential could be decreased under compressive biaxial strain due to the weakening of the Li-O bond interaction. The present findings may serve to improve the control of the energy density performance of layered cathode materials., This work was supported in part by JSPS KAKENHI grant JP19H05815, MEXT as “Program for Promoting Research on the Supercomputer Fugaku” grants JPMXP1020200301 and JPMXP1020230325, Data Creation and Utilization Type Material Research and Development Project grant JPMXP1121467561, as well as JST COI-NEXT grant JPMJPF2016., Peer Reviewed, Postprint (published version)

Rechargeable magnesium batteries are promising energy storage technology which could eventually power electric cars. However, the double charge of Mg-ion results in sluggish kinetics in most cathode materials. Due to that, exotic materials, with more complex discharging mechanisms than what we are used for conventional Li-ion batteries, have been explored. In particular, vanadium tetrasulfide (VS4), a quasi-1D material, was recently shown to be a good candidate for magnesium storage, providing good theoretical capacity and excellent kinetics for magnesium intercalation. Here we present a DFT-based analysis of the complex magnesation process of VS4. The results indicate a mixed hetero- and homogeneous process with Mg0.75VS4 formed at the initial stages of the cathode discharge. At higher magnesiation levels (i.e., MgxVS4 with x > 1) we observed a possible degradation mechanism related to the V[sbnd]S bond breaking, which leads to the formation of magnesium sulfur clusters inside the structure. All of that enables us to identify the origin of the superior properties of VS4 as cathode material, enabling the design of strategies to further improve its performance.

Rechargeable all-solid-state batteries (ASSBs) are considered as promising candidates for next-generation energy storage due to their high energy density and excellent safety performance. However, the low ionic conductivity of the solid-state electrolytes (SSEs) and interfacial issues are still challenging. Herein, we report a series of new mixed-metal halide superionic conductors Li3−xY1−xHfxCl6 (0 ≤ x < 1) with high ionic conductivity up to 1.49 mS cm−1 at room temperature. Using various experimental characterization techniques and bond-valence energy landscape (BVEL) calculations, we gain insights into the aliovalent substitution of Hf for Y in halide Li3YCl6 that influences the local structural environment and the underlying lithium-ion transport. Importantly, it is found that the existence of prevalent cation site disorder and defect structure as well as the synthetically optimized (Y/Hf)Cl6 framework with a more covalent feature in Hf4+-substituted Li3YCl6 strongly benefits the transport properties. In particular, the formation of an infinitely 3D connected Li+ ion diffusion pathway consisting of face-sharing octahedra within the lattice of Hf4+-substituted Li3YCl6 is revealed by structural elucidation and theoretical calculations. Additionally, owing to the exceptional interfacial stability of the as-milled SSEs against high-voltage cathode materials, all-solid-state lithium-ion batteries with a LiCoO2 cathode and Li-In anode exhibit outstanding electrochemical performance. © 2023 The Royal Society of Chemistry.

Cathode voltage drop (CVD) is an important component of pot voltage. Many initiatives to lower CVD have been implemented in industry. One of them is copper inserts in the collector bars which have been implemented successfully in many smelters. Recently, this idea has been pushed further by using full copper collector bars that are sealed into the cathode blocks in new, innovative ways without the need for cast iron rodding. This paper describes the design, preheat, start-up and performance of the first proprietary and patented full copper collector bar test pot in Emirates Global Aluminium (EGA). Detailed measurements of several critical parameters were made during all stages of the pot start-up and operation. The CVD in the test pot is approximately half the value of the CVD in regular steel collector bar pots and is also much lower than in pots with copper inserts. The performance of full copper collector bar pots is comparable to that of regular pots, except for the fact that they show a considerably lower specific energy consumption for the same pot technology. Building on the success of the first pot, several other full copper collector bar pots have been put into operation in different EGA pot technologies., Cathode voltage drop (CVD) is an important component of pot voltage. Many initiatives to lower CVD have been implemented in industry. One of them is copper inserts in the collector bars which have been implemented successfully in many smelters. Recently, this idea has been pushed further by using full copper collector bars that are sealed into the cathode blocks in new, innovative ways without the need for cast iron rodding. This paper describes the design, preheat, start-up and performance of the first proprietary and patented full copper collector bar test pot in Emirates Global Aluminium (EGA). Detailed measurements of several critical parameters were made during all stages of the pot start-up and operation. The CVD in the test pot is approximately half the value of the CVD in regular steel collector bar pots and is also much lower than in pots with copper inserts. The performance of full copper collector bar pots is comparable to that of regular pots, except for the fact that they show a considerably lower specific energy consumption for the same pot technology. Building on the success of the first pot, several other full copper collector bar pots have been put into operation in different EGA pot technologies.

The implementation of Ready-to-Use Cathodes (RuC) using copper conductors in the cathodic system not only allowed to fully avoid rodding but also significantly decreased the specific energy consumption, reducing the carbon footprint of the Hall-Héroult process. The basic concepts, the cathode implementation, and the operating figures in smelting technologies ranging from 300 to 600 kA for up to 2.5 years of operation are highlighted. The robustness of the Ready-to-Use design is proven by stable low cathodic resistance allowing energy savings in the range from 0.15 kWh to 0.40 kWh per kg aluminium. An autopsy performed after 1 140 days of operation revealed a fully intact copper bar system. Copper samples were taken from the bars at different locations and chemically analysed, concluding that most of the copper value can be recovered after its useful life through recycling processes. Based on these positive results, further spread of the Ready-to-Use Cathode technology is expected., The implementation of Ready-to-Use Cathodes (RuC) using copper conductors in the cathodic system not only allowed to fully avoid rodding but also significantly decreased the specific energy consumption, reducing the carbon footprint of the Hall-Héroult process. The basic concepts, the cathode implementation, and the operating figures in smelting technologies ranging from 300 to 600 kA for up to 2.5 years of operation are highlighted. The robustness of the Ready-to-Use design is proven by stable low cathodic resistance allowing energy savings in the range from 0.15 kWh to 0.40 kWh per kg aluminium. An autopsy performed after 1 140 days of operation revealed a fully intact copper bar system. Copper samples were taken from the bars at different locations and chemically analysed, concluding that most of the copper value can be recovered after its useful life through recycling processes. Based on these positive results, further spread of the Ready-to-Use Cathode technology is expected.

In the conventional synthesis of layered transition metal oxides the high-temperature process not only causes lithium loss due to evaporation, but also facilitate the inevitable cation mixing of Li+ and Ni2+, resulting in severe shifts in their stoichiometric ratios and thus structure instability. Herein, we report a universal ion-exchange method to prepare Ni-rich layered oxide materials LiNi0.85Co0.06Mn0.09O2 (NCM85) with low Li/Ni intermixing at a low reaction temperature of 300 °C, where sodium-based layered oxides (NaNi0.85Co0.06Mn0.09O2) were used as precursors for ion exchange with Li+ ion in lithium molten salts. By studying the effects of ion-exchange time and additional heat treatment on the structure and performance of the layered oxide materials, we established the processing-structure-performance relationships for Ni-rich NCM85 materials. Moreover, we further demonstrated the universality of this ion-exchange method and processing-structure-performance relationships for other layered oxide materials including LiNi0. 5Co0.2Mn0.3O2 and LiNi0.5Mn0.5O2. We anticipate that such universal method of ion exchange and universal processing-structure-performance relationships can guide the rational design and synthesis of other layered oxide materials for lithium-ion batteries.

Nickel-rich LiNi0.8Mn0.1Co0.1O2 (NMC811) is one of the most promising Li-ion battery cathode materials and has attracted the interest of the automotive industry. Nevertheless, storage conditions can affect its properties and performance. In this work, both NMC811 powder and electrodes were storage-aged for one year under room conditions. The aged powder was used to prepare electrodes, and the performance of these two aged samples was compared with reference fresh NMC811 electrodes in full Li-ion coin cells using graphite as a negative electrode. The cells were subjected to electrochemical as well as ante- and postmortem characterization. The performance of the electrodes from aged NM811 was beyond expectations: the cycling performance was high, and the power capability was the highest among the samples analyzed. Materials characterization revealed modifications in the crystal structure and the surface layer of the NMC811 during the storage and electrode processing steps. Differences between aged and fresh electrodes were explained by the formation of a resistive layer at the surface of the former. However, the ageing of NMC811 powder was significantly mitigated during the electrode processing step. These novel results are of interest to cell manufacturers for the widespread implementation of NMC811 as a state-of-the-art cathode material in Li-ion batteries.

Li-ion batteries (LIBs) can reduce carbon emissions by powering electric vehicles (EVs) and promoting renewable energy development with grid-scale energy storage. However, LIB production and electricity generation still heavily rely on fossil fuels at present, resulting in major environmental concerns. Are LIBs as environmentally friendly and sustainable as expected at the current stage? In the past 5 years, a skyrocketing growth of the EV market has been witnessed. LIBs have garnered huge attention from academia, industry, government, non-governmental organizations, investors, and the general public. Tremendous volumes of LIBs are already implemented in EVs today, with a continuing, exponential growth expected for the years to come. When LIBs reach their end-of-life in the next decades, what technologies can be in place to enable second-life or recycling of batteries? Herein, life cycle assessment studies are examined to evaluate the environmental impact of LIBs, and EVs are compared with internal combustion engine vehicles regarding environmental sustainability. To provide a holistic view of the LIB development, this Perspective provides insights into materials development, manufacturing, recycling, legislation and policy, and beyond. Last but not least, the future development of LIBs and charging infrastructures in light of emerging technologies are envisioned.

TiSiCN coatings have been obtained by anode evaporation of titanium and the decomposi-tion of hexamethyldisilazane in an arc discharge, using a self-heated hollow cathode, at the pressure rate of 1 mTorr of the Ar+N2 gas mixture. The proposed method makes it possible to independently and widely change the amount of metal and precursor vapor flows, the pressure and composition of the vapor-gas mixture and the degree of ionic interaction on the surface of the growing coating within a single discharge system. The paper presents the method and the results of the effect of a current discharge (10–50 A), and the flux of precursor vapours (0–1 g/h), on deposition rates, compositions, and properties of TiSiCN coatings deposited by an advanced combined PVD+PECVD method. Dense homogeneous TiSiCN coatings up to 6 µm thick and up to 27.5 GPa in hardness were obtained at 7.5 µm/h. The composition of the obtained coatings has been studied by X-ray diffraction and X-ray photoelectron spectroscopy, and it has been shown that the presented methods can form nanocomposite coatings with nanocrystallites TiC, TiN, and TiCxN1−x 3–10 nm in the amorphous matrix based on SiCN. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.

We report the synthesis and electrochemical characterization of octahydroxytetraazapentacenedione (OHTAPQ). The potassium batteries using OHTAPQ as electrode material delivered the specific capacity of 190 mAh g−1 at the current density of 0.6 A g−1. The use of the concentrated (2.2 M KPF6) diglyme-based electrolyte suppressed significantly the capacity fading of the potassium half-cells with OHTAPQ electrodes thus enabling their stable operation for 1200 charge-discharge cycles. Furthermore, OHTAPQ delivered the specific discharge capacity of 82–103 mAh g−1 at high current densities of 9–21 A g−1, which leads to high power densities approaching 41000 W kg−1. Thus, we demonstrate that the rationally designed organic electrode material enables high-capacity and high-power potassium batteries, which can be considered as a more environment-friendly and scalable alternative to the mainstream lithium-ion battery technology. © 2021 Elsevier B.V.

Development of new functional materials with improved characteristics for solid oxide fuel cells (SOFCs) and solid oxide electrolysis cells (SOECs) is one of the most important tasks of modern materials science. High electrocatalytic activity in oxygen reduction reactions (ORR), chemical and thermomechanical compatibility with solid electrolytes, as well as stability at elevated temperatures are the most important requirements for cathode materials utilized in SOFCs. Layered oxygen-deficient double perovskites possess the complex of the above-mentioned prop-erties, being one of the most promising cathode materials operating at intermediate temperatures. The present review summarizes the data available in the literature concerning crystal structure, thermal, electrotransport-related, and other functional properties (including electrochemical performance in ORR) of these materials. The main emphasis is placed on the state-of-art approaches toimproving the functional characteristics of these complex oxides. © 2021 by the authors. Licensee MDPI, Basel, Switzerland.

Multivalent batteries are an energy storage technology with the potential to surpass lithium-ion batteries; however, their performance have been limited by the low voltages and poor solid-state ionic mobility of available cathodes. A computational screening approach to identify high-performance multivalent intercalation cathodes among materials that do not contain the working ion of interest has been developed, which greatly expands the search space that can be considered for material discovery. This approach has been applied to magnesium cathodes as a proof of concept, and four resulting candidate materials [NASICON V2(PO4)3, birnessite NaMn4O8, tavorite MnPO4F, and spinel MnO2] are discussed in further detail. In examining the ion migration environment and associated Mg2+ migration energy in these materials, local energy maxima are found to correspond with pathway positions where Mg2+ passes through a plane of anion atoms. While previous studies have established the influence of local coordination on multivalent ion mobility, these results suggest that considering both the type of the local bonding environment and available free volume for the mobile ion along its migration pathway can be significant for improving solid-state mobility.

Cation-disordered rocksalt (DRX) oxides are a promising new class of high-energy-density cathode materials for next-generation Li-ion batteries. However, their capacity fade presents a major challenge. Partial fluorine (F) substitution into the oxygen (O) lattice appears to be an effective strategy for improving the cycling stability, but the underlying atomistic mechanism remains elusive. Here, using a combination of advanced transmission electron microscopy based imaging and spectroscopy techniques, the structural and chemical evolution upon cycling of Mn-based DRX cathodes with an increasing F content (Li-Mn-Nb-O-Fx , x = 0, 0.05, 0.2) are probed. The atomic origin behind the beneficial effect of high-level fluorination for enhancing the surface stability of the DRX is revealed. It is discovered that, due to the reduced O redox activity while with increasing F concentration, F in the DRX lattice mitigates the formation of an O-deficient surface layer upon cycling. For low F-substituted DRX, the O loss near the surface results in the formation of an amorphous cathode-electrolyte interphase layer and nanoscale voids after extended cycling. Increased F concentration in the DRX lattice minimizes both O loss and the interfacial reactions between DRX and the liquid electrolyte, enhancing the surface stability of DRX. These results provide guidance on the development of next-generation cathode materials through anion substitution.

Hydrogen crossover poses a crucial issue for polymer electrolyte membrane (PEM) water electrolysers in terms of safe operation and efficiency losses, especially at increased hydrogen pressures. Besides the impact of external operating conditions, the structural properties of the materials also influence the mass transport within the cell. In this study, we provide an analysis of the effect of elevated cathode pressures (up to 15 bar) in addition to increased compression of the membrane electrode assembly on hydrogen crossover and the cell performance, using thin Nafion 212 membranes and current densities up to 3.6 A cm-2. It is shown that a higher compression leads to increased mass transport overpotentials, although the overall cell performance is improved due to the decreased ohmic losses. The mass transport limitations also become visible in enhanced anodic hydrogen contents with increasing compression at high current densities. Moreover, increases in cathode pressure are amplifying the compression effect on hydrogen crossover and mass transport losses. The results indicate that the cell voltage should not be the only criterion for optimizing the system design, but that the material design has to be considered for the reduction of hydrogen crossover in PEM water electrolysis.

In search of high energy density cathode materials, the eldfellite mineral-type NaVIII(SO4)2 compound has been theoretically predicted to be a promising cathode insertion host for sodium-ion batteries. Synergizing computational and experimental investigations, the current work introduces NaVIII(SO4)2 as a novel versatile cathode for Li-ion and Na-ion batteries. Prepared by a low temperature sol-gel synthesis route, the eldfellite NaV(SO4)2 cathode exhibited an initial capacity approaching ∼79% (vs. Li+/Li) and ∼69% (vs. Na+/Na) of the theoretical capacity (1e− ≅ 101 mA h g−1) involving the V3+/V2+ redox potential centered at 2.57 V and 2.28 V, respectively. The bond valence site energy (BVSE) approach and DFT-based calculations were used to gain mechanistic insight into alkali ion migration and probe the redox center during (de)insertion of Li+/Na+ ions. Post-mortem and electrochemical titration tools revealed the occurrence of a single-phase (solid-solution) redox mechanism during reversible Li+/Na+ (de)insertion into NaVIII(SO4)2. With the multivalent vanadium redox center, eldfellite NaVIII(SO4)2 forms a new cathode insertion host for Li/Na-ion batteries with potential two-electron uptake., QC 20230613

Covalent triazine frameworks (CTFs) are among the most valuable frameworks owing to many fantastic properties. However, molten salt-involved preparation of CTFs at 400–600 °C causes debate on whether CTFs represent organic frameworks or carbon. Herein, new CTFs based on the 1,3-dicyanoazulene monomer (CTF-Azs) are synthesized using molten ZnCl2 at 400–600 °C. Chemical structure analysis reveals that the CTF-Az prepared at low temperature (400 °C) exhibits polymeric features, whereas those prepared at high temperatures (600 °C) exhibit typical carbon features. Even after being treated at even higher temperatures, the CTF-Azs retain their rich porosity, but the polymeric features vanish. Although structural de-conformation is a widely accepted outcome in polymer-to-carbon rearrangement processes, the study evaluates such processes in the context of CTF systems. A proof-of-concept study is performed, observing that the as-synthesized CTF-Azs exhibit promising performance as cathodes for Li- and K-ion batteries. Moreover, the as-prepared NPCs exhibit excellent catalytic oxygen reduction reaction (ORR) performance; hence, they can be used as air cathodes in Zn-air batteries. This study not only provides new building blocks for novel CTFs with controllable polymer/carbon features but also offers insights into the formation and structure transformation history of CTFs during thermal treatment., QC 20230327

Triple ionic and electronic conductivity (TIEC) in cathode materials for protonic ceramic fuel cells (PCFCs) is a desirable feature that enhances the spatial expansion of active reaction sites for electrochemical oxygen reduction reaction. The realization of optimal TIEC in single-phase materials, however, is challenging. A facile route that facilitates the optimization of TIEC in PCFC cathodes is the strategic development of multiphase cathode materials. In this study, a cubic-rhombohedral TIEC nanocomposite material with the composition Ba(CeCo)(0.4)(FeZr)(0.1)O-3-(delta) (BCCFZ) is designed via self-assembly engineering. The material consists of a mixed ionic and electronic conducting phase, BaCo1-(x+y+z)CexFeyZrzO3-delta (M-BCCFZ), and a dominant proton-conducting phase, BaCe1-(x+y+z)CoxZryFezO3-delta (H-BCCZF). The dominant cerium-rich H-BCCFZ phase enhances the material's oxygen vacancy concentration and the proton defects formation and transport with a low enthalpy of protonation of -30 +/- 9 kJ mol(-1). The area-specific resistance of the BCCFZ symmetrical cell is 0.089 ohm cm(2) at 650 degrees C in 2.5% H2O-air. The peak power density of the anode-supported single cell based on BCCFZ cathode reaches 1054 mW cm(-2) at 650 degrees C with good operation stability spanning over 500 h at 550 degrees C. These promote BCCFZ as a befitting cathode material geared toward PCFC commercialization.

In the process of upgrading energy storage structures, sodium-ion batteries (SIBs) are regarded as the most promising candidates for large-scale grid storage systems. However, the difficulty in further improving their specific capacity and lifespan has become a major obstacle to promoting extensive application. Herein, by optimizing synthesis conditions, a biphasic-Na2/3Ni1/3Mn2/3O2 cathode that exhibits an ultrahigh capacity of ≈200 mAh g-1 without the involvement of anion redox reactions is successfully synthesized. Nevertheless, there is significant electrochemical performance degradation because of failure at the cathode-electrolyte interface as revealed by comprehensive analyses. Further in-depth research proves that the surface side reactions that occur at high operating voltages and the transition metal dissolution that occurs in low voltage are the root causes of electrode surface failure. Therefore, the metal oxide atomic layer deposition (ALD) protective layer is deliberately chosen to suppress such failures. The coating effectively blocks corrosion of the cathode material by the electrolyte and successfully anchors the transition metal ions on the particle surface. As a result, the cycle stability and rate performance of the electrode are improved considerably. This surface engineering strategy could provide concepts with broad applicability for suppressing the failure of sodium layered cathodes. © 2021 Wiley-VCH GmbH

The use of a nanostructured aluminum substrate as the cathode for a perovskite photovoltaic device is described. This cathode consists of an aluminum substrate onto which a highly ordered array of aluminum oxide tubular pores was grown via anodization. The 1-mu m thick pores - arranged in a closed-packed hexagonal pattern - were subsequently selectively etched at the bottom to remove the so-called aluminum oxide barrier layer. The subsequent infiltration of the pores with the components of a methylammonium lead iodide perovskite solar cells, and the completion with a semi-transparent anode, have shown to allow the establishment of an ohmic contact between the substrate itself and the components infiltrated into the Al2O3 pores. Indeed, a clear rectifying behavior was observed on the full devices, as well as modest photovoltaic conversion efficiencies. This paper demonstrates that an ohmic contact can be established between the aluminum substrate from which nanoporous anodic alumina was grown, and that the pores can be used to compartmentalize the infill material down to the nanoscopic level.

The current methods of water quality monitoring tend to be costly, labor-intensive, and off-site. Also, they are not energetically sustainable and often require environmentally damaging power sources such as batteries. Microbial fuel cell (MFC) technology is a promising sustainable alternative to combat these issues due to its low cost, eco-friendly energy generation, and bio-sensing features. Extensive work has been done on using MFCs as bio-sensors or sources of power separately. However, little work has been done toward using MFCs for both applications at the same time. Additionally, previous studies using MFCs for water quality measurement have been mostly limited to laboratory conditions due to the biochemical complexity of the real-world. Another limitation of MFCs is how little power they can generate, requiring the MFC-based systems to have minimal power consumption. This work addresses these challenges and presents an energy-autonomous water quality sensing unit that uses a single MFC both as its sensory input and the sole source of power for computing the chemical oxygen demand (COD). In the proposed unit, geometric features of the voltage profile of the MFC (e.g., peak heights) are used as the inputs to a machine learning algorithm (support vector regression (SVR)). The electrical power generated by the MFC is used to drive a low-power microcontroller which logs the MFC voltage and runs the machine learning algorithm. Experimental evaluation showed that the device is capable of detecting the COD of natural pond water samples accurately (coefficient of determination (R 2 )=0.94). This work is the first demonstration of energy autonomy in an MFC-based sensing unit for measuring water quality and represents a step forward in the development of energy-autonomous sensors for environmental monitoring applications.

In the process of upgrading energy storage structures, sodium-ion batteries (SIBs) are regarded as the most promising candidates for large-scale grid storage systems. However, the difficulty in further improving their specific capacity and lifespan has become a major obstacle to promoting extensive application. Herein, by optimizing synthesis conditions, a biphasic-Na2/3Ni1/3Mn2/3O2 cathode that exhibits an ultrahigh capacity of ≈200 mAh g-1 without the involvement of anion redox reactions is successfully synthesized. Nevertheless, there is significant electrochemical performance degradation because of failure at the cathode-electrolyte interface as revealed by comprehensive analyses. Further in-depth research proves that the surface side reactions that occur at high operating voltages and the transition metal dissolution that occurs in low voltage are the root causes of electrode surface failure. Therefore, the metal oxide atomic layer deposition (ALD) protective layer is deliberately chosen to suppress such failures. The coating effectively blocks corrosion of the cathode material by the electrolyte and successfully anchors the transition metal ions on the particle surface. As a result, the cycle stability and rate performance of the electrode are improved considerably. This surface engineering strategy could provide concepts with broad applicability for suppressing the failure of sodium layered cathodes. © 2021 Wiley-VCH GmbH

A new process is presented for low-cost one-step production of pure solid silicon from natural quartzite by molten salt electrolysis. At a process temperature of 1 100 degrees C, a techno-economic model including detailed mass and energy balances estimates energy consumption below 15 kWh/kg, with operating cost of US, A new process is presented for low-cost one-step production of pure solid silicon from natural quartzite by molten salt electrolysis. At a process temperature of 1 100 degrees C, a techno-economic model including detailed mass and energy balances estimates energy consumption below 15 kWh/kg, with operating cost of US

The development, by Helix BioS and Free Radical Process Design (FRPD), of an electrochemistry-based water-treatment process for harvesting metals from acid mine drainage generated by closed polymetallic sulphide mines in the Peruvian Andes is described. The Rotowinner process employs a continuous and autonomous electrowinning (electrolysis/electro-coagulation) technology incorporating a rotating cathode in a containerised module. The recovery of metals such as zinc, manganese, iron and copper, and metal oxides from acid mine drainage is achieved by simultaneous scraping of, e.g. zinc, from a rotating electrode and, e.g. manganese dioxide, from a counter-rotating electrode, while iron is precipitated as a sludge under an electric field. The planned deployment of laboratory-scale units near mining areas - to optimise water remediation and materials recovery - and of containerised units for testing at a precious-metal mining/refining site is discussed., The development, by Helix BioS and Free Radical Process Design (FRPD), of an electrochemistry-based water-treatment process for harvesting metals from acid mine drainage generated by closed polymetallic sulphide mines in the Peruvian Andes is described. The Rotowinner process employs a continuous and autonomous electrowinning (electrolysis/electro-coagulation) technology incorporating a rotating cathode in a containerised module. The recovery of metals such as zinc, manganese, iron and copper, and metal oxides from acid mine drainage is achieved by simultaneous scraping of, e.g. zinc, from a rotating electrode and, e.g. manganese dioxide, from a counter-rotating electrode, while iron is precipitated as a sludge under an electric field. The planned deployment of laboratory-scale units near mining areas - to optimise water remediation and materials recovery - and of containerised units for testing at a precious-metal mining/refining site is discussed.

Nano polymorphism (NPM), as an emerging research area in the field of energy storage, and rechargeable batteries, have attracted much attention recently. In this review, the recent progress on the composition and formation of polymorphs, and the evolution processes of different redox electrodes in rechargeable metal-ion, metal–air, and metal–sulfur batteries are highlighted. First, NPM and its significance for rechargeable batteries are discussed. Subsequently, the current NPM modulation strategies of different types of representative electrodes for their corresponding rechargeable battery applications are summarized. The goal is to demonstrate how NPM could tune the intrinsic material properties, and hence, improve their electrochemical activities for each battery type. It is expected that the analysis of polymorphism and electrochemical properties of materials could help identify some “processing–structure–properties” relationships for material design and performance enhancement. Lastly, the current research challenges and potential research directions are discussed to offer guidance and perspectives for future research on NPM engineering.

Controlling the structure of graphene-based materials with improved ion intercalation and diffusivity is crucial for their applications, such as in aluminum-ion batteries (AIBs). Due to the large size of AlCl4− ions, graphene-based cathodes have specific capacities of ≈60 to 148 mAh g−1, limiting the development of AIBs. A thermal reductive perforation (TRP) strategy is presented, which converts three-layer graphene nanosheets to surface-perforated graphene materials under mild temperature (400 °C). The thermal decomposition of block copolymers used in the TRP process generates active radicals to deplete oxygen and create graphene fragments. The resultant material has a three-layer feature, in-plane nanopores, >50% expanded interlayer spacing, and a low oxygen content comparable to graphene annealed at a high temperature of ≈3000 °C. When applied as an AIB cathode, it delivers a reversible capacity of 197 mAh g−1 at a current density of 2 A g−1 and reaches 92.5% of the theoretical capacity predicted by density-functional theory simulations.

This licentiate thesis presents experimental studies concerning two parts of the electrochemical cell in the chlorate process: a cathode and an anode. Newly synthesized MnOx electrodes were investigated for the cathodic reaction, hydrogen evolution reaction (HER) in the chlorate process. In industry addition of toxic and carcinogenic chromium (VI) as sodium dichromate provides high efficiency. Here undesirable addition of sodium dichromate was avoided while high cathodic efficiency was achieved. Cathodic efficiency and selectivity towards HER, achieved by the MnOx electrodes annealed at different temperatures, were measured by means of mass spectrometry (MS). The second study investigated oxygen evolution in the chlorate process, which is an anodic side reaction. The evolution of oxygen decreases anodic efficiency and also presents a safety risk due to occurrence of HER in the undivided cell. We followed the amount of produced oxygen by two types of the electrode TiRu, similar to that industrially used, and synthesized TiRuSnSb, by means of MS. The produced oxygen amount was compared to the amount produced by Pt. To our best knowledge, this was the first study that successfully disentangles three different sources of oxygen with good time resolution. Oxygen is produced by homogenous hypochlorite decomposition, heterogeneously by different catalysts present in the electrolyte solution and anodically during the electrolysis i.e. electrochemically. Different electrode materials catalyzed hypochlorite decomposition differently and led to a different volume of oxygen produced., Denna licentiatavhandling redogör för experimentella studier av tvådelar av den elektrokemiska cell som används i kloratprocessen:katoden och anoden. Syntetiserade MnOx elektroder utvärderades för katodreaktionen,vätgasutveckling, i kloratprocessen. Industriellt tillsätts giftigt ochcancerogent krom(IV) som natriumdikromat för hög verkningsgrad. Denna studie uteslöt oönskad tillsats av natriumdikromat samtidigt som hög katodisk effektivitet erhölls. Katodisk effektivitet och selektivitet för vätgasutveckling, med MnOx elektroder,värmebehandlade vid olika temperaturer, uppmättes med masspektrometer. I den andra studien undersöktes syrgasutveckling i kloratprocessen,vilket är en anodisk sidoreaktion. Syrgasutvecklingen minskar den anodiska effektiviteten och utgör en säkerhetsrisk med anledning avden pågående vätgasutvecklingen i den odelade cellen. Vi uppmättemängden producerad syrgas med två olika elektroder TiRu, liknandeden som industriellt används, och syntetiserad TiRuSnSb, med masspektrometer. Den producerade syrgasmängden jämfördes med mängden producerat på Pt. Såvitt vi vet var detta den första studiesom särskiljer på tre olika syrgaskällor med god tidsupplösning. Syrgas produceras homogent av hypokloritsönderfall, heterogent av olika katalysatorer närvarande i elektrolyten och anodiskt vid elektrolys dvs. elektrokemiskt. Olika elektrodmaterial katalyserade hypokloritsönderfall olika och producerade olika volym syrgas., QC 2021-04-28

Luminescent characteristics of K3Lu(PO4)2:Pr3+ (1 and 5 mol.%) microcrystalline powders, a promising optical material for scintillation applications, were investigated using various experimental techniques. The material shows emission features connected with both high intensity interconfigurational 4f15d→4f2 transitions (broad UV emission bands) and intraconfigurational 4f2→4f2 transitions (weak emission lines in the visible range). The output of X-ray excited 4f15d→4f2 emission of Pr3+ increases with a temperature rise from 90 K to room temperature and higher depending on the Pr3+ ions concentration. The high 5% concentration of Pr3+ ions is found to be favourable for the stabilization of a monoclinic phase (P21/m space group) over a trigonal one (P3‾ space group) while emission properties of the material reveal that a phase transition occurs at higher temperatures. Decay kinetics of Pr3+ 4f15d→4f2 emission are recorded upon excitation with high repetition rate X-ray synchrotron excitation and pulse cathode ray excitation. Issues related to a non-exponential decay of luminescence and presence of slow decay components are discussed in terms of energy transfer dynamics. The presence of defects was revealed with thermoluminescence measurements and these are suggested to be the mainly responsible for delayed recombination of charge carriers on the Pr3+ 4f15d states. Some peculiarities of host-to-impurity energy transfer are discussed. © 2020 Elsevier B.V.

Electrolytic copper refining allows one to obtain high-purity copper, so analyzing the main ways impurities transition into electrolysis products is a relevant problem. Solving it makes it possible to control the process when changing the composition of raw materials and, as a result, the content of impurities in the anodes. In this work, on the basis of a complex analysis and synchronization of a large array of data on impurity concentrations in various industrial environments obtained on a series of commercial cells, the directions of the flow of impurities is determined and the relationship between the content of impurities in the different products of the electrolysis (slime, electrolyte, and copper cathode) is established. It is shown that the transition of impurities from one process medium (source) to another (receiver) occurs by four main schemes: linear increase, no visible dependence, the presence of the limit concentration in the receiver, and the presence of the threshold concentration in the source. The results of a statistical analysis of the distribution of six impurities (bismuth, arsenic, lead, sulfur, nickel, and silver) belonging to different groups are presented in four main pairs of the impurity source–receiver: anode–solution, anode–slime, slime–cathode, and solution–cathode. For all dependencies of the impurity concentration in the source on the content in the receiver, the coefficients of linear regression equations are determined and their significance is estimated. The coefficients make it possible to explain the pathways of the impurity transition observed in the commercial cells and predict the quality of cathode copper and the composition of slime when the anode composition changes. Calculations show that the accumulation of impurities in the cathodes is due to the occlusion of slime particles and the incomplete removal of the solution from the surface of commercial cathodes rather than electrochemical reactions. Attempts to im

Reduction of ZrO2 by lithium during electrolysis of LiCl-KCl-Li2O melt at 650 C was studied using a set of physicochemical methods of analysis. Influence of ZrO2 in the space near a molybdenum cathode on the kinetics of the cathode process was established. Possible variations of the electrode reaction associated with the zirconium reduction were proposed. The appearance of ZrO2 in the cathode space resulted in consumption of reduced lithium and in increase in the potential relaxation time of the molybdenum cathode after cathode polarization. Long-term galvanic impulse electrolysis of LiCl-KCl-Li2O melt at 650 C was carried out using the molybdenum cathode which was immersed into the ZrO2 powder. According to the X-ray fluorescence analysis as well as the method of nuclear reactions the reduction product was presented by the ZrO2, Li2ZrO3, Zr3O phases. Additionally, by alloying the reduction product with tin, the ZrO2 reduction degree to metallic zirconium was estimated, which was close to zero. It was assumed that the main pathway for the appearance of the metallic zirconium in the ZrO2 reduction product during electrolysis of the LiCl-KCl-Li2O melt was direct electroreduction of dissolved zirconium in the melt. © 2021 The Author(s). Published on behalf of The Electrochemical Society by IOP Publishing Limited.

Increasing concerns regarding the sustainability of lithium sources, due to their limited availability and consequent expected price increase, have raised awareness of the importance of developing alternative energy-storage candidates that can sustain the ever-growing energy demand. Furthermore, limitations on the availability of the transition metals used in the manufacturing of cathode materials, together with questionable mining practices, are driving development towards more sustainable elements. Given the uniformly high abundance and cost-effectiveness of sodium, as well as its very suitable redox potential (close to that of lithium), sodium-ion battery technology offers tremendous potential to be a counterpart to lithium-ion batteries (LIBs) in different application scenarios, such as stationary energy storage and low-cost vehicles. This potential is reflected by the major investments that are being made by industry in a wide variety of markets and in diverse material combinations. Despite the associated advantages of being a drop-in replacement for LIBs, there are remarkable differences in the physicochemical properties between sodium and lithium that give rise to different behaviours, for example, different coordination preferences in compounds, desolvation energies, or solubility of the solid-electrolyte interphase inorganic salt components. This demands a more detailed study of the underlying physical and chemical processes occurring in sodium-ion batteries and allows great scope for groundbreaking advances in the field, from lab-scale to scale-up. This roadmap provides an extensive review by experts in academia and industry of the current state of the art in 2021 and the different research directions and strategies currently underway to improve the performance of sodium-ion batteries. The aim is to provide an opinion with respect to the current challenges and opportunities, from the fundamental properties to the practical applications of this technology.

Glycerol electrolysis affords a green and energetically favorable route for the production of value-added chemicals at the anode and H2 production in parallel at the cathode. Here, a facile method for trapping Pt nanoparticles at oxygen vacancies of molybdenum oxide (MoOx) nanosheets, yielding a high-performance MoOx/Pt composite electrocatalyst for both the glycerol oxidation reaction (GOR) and the hydrogen evolution reaction (HER) in alkaline electrolytes, is reported. Combined electrochemical experiments and theoretical calculations reveal the important role of MoOx nanosheets for the adsorption of glycerol molecules in GOR and the dissociation of water molecules in HER, as well as the strong electronic interaction with Pt. The MoOx/Pt composite thus significantly enhances the specific mass activity of Pt and the kinetics for both reactions. With MoOx/Pt electrodes serving as both cathode and anode, two-electrode glycerol electrolysis is achieved at a cell voltage of 0.70 V to reach a current density of 10 mA cm−2, which is 0.90 V less than that required for water electrolysis., QC 20220516

Altogether five platinum group metal (PGM) and PGM-free cathode catalysts were investigated in full PEM water electrolysis cells regarding their polarisation behaviour and their hydrogen and oxygen recombination properties. It was shown that the recombination activity of permeated oxygen and evolved hydrogen within the cathodic catalyst layer correlates with the activity of the oxygen reduction reaction (ORR) which was determined ex situ with linear sweep voltammetry. We found that the investigated PGM-free cathode catalysts had a low activity for the ORR resulting in higher measurable oxygen in hydrogen volume fractions compared to the PGM catalysts, which are more active for the ORR. Out of the three investigated PGM-free catalysts, only one commercially available material based on a Ti suboxide showed a similar good polarisation behaviour as the state of the art cathode catalyst platinum, while its recombination activity was the lowest of all catalysts. In addition to the recombination of hydrogen and oxygen on the electrocatalysts, we found that the prevalent carbon-based cathodic porous transport layers (PTL) also offer catalytically active recombination sites. In comparison to an inactive PTL, the measurable oxygen flux using carbon-based PTLs was lower and the recombination was enhanced by microporous coatings with high surface areas. © 2021 The Author(s).

In this work, the sequential Electrocoagulation + Electro-oxidation + Activated carbon adsorption (EC + EO + AC) process was studied as an alternative for the treatment of an industrial textile wastewater (TWW) issuing from a manufacturing company located in Medellín (Colombia). The EC's and EO's operational conditions were optimized using a Box-Behnken experimental design, the Response Surface Methodology and a constrained nonlinear optimization algorithm in terms of organic matter degradation efficiency. The best performance for EC (i. e., dye removal = 94%, COD and TOC degradation of 45 and 40%, respectively) was obtained using Fe anode and Boron Doped Diamond (BDD) cathode, with current density, jEC, equals to 5 mA/cm2, pH = 9.3, 60 RPM and 10 min of electrolysis. After EC treatment, the effluent biodegradability (evaluated as the BOD5/COD ratio) increases from 0.14 to 0.23. Regrettably, EC was not effective for the removal of acute toxicity to Artemia salina since the treated effluent remained very toxic (100%). The treatment of EC's effluent by EO enhanced organic pollutant removal. For EC + EO sequential process, EO optimal operational conditions (jEO = 10 mA/cm2, pH = 3, 240 RPM, BDD as anode and Fe as cathode) allowed reduction of 100% of color, 88% of COD and 79% of TOC after 30 min of electrolysis. Moreover, the BOD5/COD ratio increased from 0.23 to 0.58; however, the treated effluent remained very toxic to the Artemia salina. Consequently, an activated carbon adsorption step was included to complete the treatment process. Thus, by coupling the EC + EO + AC process, effluent's acute toxicity decreased completely. From molecular weight distribution analysis, it was concluded that EC + EO was efficient in eliminating low molecular weight (< 5 kDa) compounds. Finally, the operation cost, which includes chemical reagents, electrodes, energy consumption, and sludge disposal, for the EC + EO + AC sequential process was estimated in 3.83 USD /m3. © 2020 Elsev

In this work, the Box–Behnken experimental design and the surface response methodology were applied for the optimization of the operational conditions of the electro-catalytic degradation of wastewaters, resulting from a local textile industry. The experiments were carried out in a laboratory scale batch cell reactor, with monopolar configuration, and electrodes made of boron-doped diamond (anode) and titanium (cathode). The multifactorial experimental design included the following variables: current density (i: 5–10 ?mA/cm2), pH (3–7), and submerged cathode area (CA: 8–24 ?cm2). To determine the process efficiency, the degradation percentage of: the chemical oxygen demand (%DCOD), the total organic carbon (%DTOC) and the color (%DC) were defined as response variables. The following optimal conditions for the electro-oxidation (EO) process were obtained: i ?= ?10 ?mA/cm2, pH = 3 and CA ?= ?16 ?cm2, reaching ca. 92 ?% of DC, 37 ?% of DCOD and 31 ?% of DTOC. The electro-Fenton (EF) and photo-electro-Fenton (PEF) processes were also evaluated at EO optimal conditions. For the EF process, with addition of iron (0.3 ?mM), the %DC, %DCOD and %DTOC was enhanced to 95, 52 and 45 ?%, respectively. For the PEF process (UV ?= ?365 ?nm), it was possible to reach 98 ?%DC, 56 ?%DCOD and 48 ?%DTOC. © 2014, Springer Science+Business Media Dordrecht.

Potassium-ion battery (KIB) is a promising technology for large-scale energy storage applications due to their low cost, theoretically high energy density and abundant resources. However, the development of KIBs is hindered by the sluggish K+ transport kinetics and the structural instability of the electrode materials during K+ intercalation/de-intercalation. In the present investigation, we have designed a potassium-ion capacitor (KIC) using layered potassium niobate (K4Nb6O17, KNO) nanosheet arrays as anode and orange-peel derived activated carbons (OPAC) as fast capacitive cathode materials. The systematic electrochemical analysis with the ex-situ characterizations demonstrates that KNO-anode exhibits highly stable layered structure with excellent reversibility during K+ insertion/de-insertion. After optimization, the fabricated KNO//OPAC delivers both a high energy density of 116 Wh/kg and high power density of 10,808 W/kg, which is significantly higher than other similar hybrid devices. The cell also displays long term cycling stability over 5000 cycles, with 87 % of capacity retention. This study highlights the utilization of layered nanosheet arrays of niobates to achieve superior K-storage for KICs, paving the way towards the development of high-performance anodes for post lithium-ion batteries. © 2020