The future in and of criticality assessments

In recent literature, the concept of criticality aspires to provide a multifaceted risk assessment of resource supply shortage. However, most existing methodologies for the criticality assessment of raw materials are restricted to a fixed temporal and spatial reference system. They provide a snapshot in time of the equilibrium between supply and demand/economic importance and do not account for temporal changes of their indicators. The static character of criticality assessments limits the use of criticality methodologies to short‐term policy making of raw materials. In the current paper, we argue for an enhancement of the criticality framework to account for three key dynamic characteristics, namely changes of social, technical, and economic features; consideration of the spatial dimension in site‐specific assessments; and impact of changing governance frameworks. We illustrate how these issues were addressed in studies outside of the field of criticality and identify the dynamic parameters that influence resource supply and demand based on a review of studies that belong to the general field of resource supply and demand. The parameters are grouped in seven categories: extraction, social, economic, technical, policy, market dynamics, and environmental. We explore how these parameters were considered in the reviewed studies and propose ways and specific examples of addressing the dynamic effects in the criticality indicators. Furthermore, we discuss the current work on future scenarios to provide reference points for indicator benchmarks. The insights and guidelines derived from the review and our recommendations for future research set the foundations for an enhanced dynamic and site‐specific criticality assessment framework.     

Geostrategic Supply Risk and Economic Importance as Drivers for Implementation of Industrial Ecology Measures in a Nitrogen Fertilizer Production Company

Among other concerns, safeguarding the supply chains of raw materials is an important task for industrial companies. Therefore, not surprisingly, the number of scientific publications concerning the evaluation of resource criticality has increased in recent years. However, it was noticed that currently published methodologies are too complex to be applied by industrial companies on a daily basis. For this reason, the need to develop a methodology that would allow not only assessing resource criticality, but could also be integrated into widely applied methodological frameworks as an additional driver to improve resource efficiency was identified. Geostrategic supply risk and economic importance were chosen as key indicators to analyze and assess relative resource criticality. The developed methodology was field tested by applying it to a resource‐intensive nitrogen fertilizer production company. Five scenarios for resource efficiency improvements, consisting of cleaner production and industrial symbiosis measures, were investigated. If all the proposed measures were implemented, consumption of natural gas would decrease by 3.552 million cubic meters per year (0.3% of the total consumption). However, not all identified measures contribute to a reduction of the overall criticality of resources for the production company. Nevertheless, the integration of criticality assessments into the widely applied methodologies for development and implementation of resource efficiency innovations is a valuable addition and should be included in the analysis for sustainable innovations and development.     

Rational Construction of Self‐Standing Sulfur‐Doped Fe2O3 Anodes with Promoted Energy Storage Capability for Wearable Aqueous Rechargeable NiCo‐Fe Batteries

Aqueous rechargeable Ni‐Fe batteries featuring an ultra‐flat discharge plateau, low cost, and outstanding safety characteristics show promising prospects for application in wearable energy storage. In particular, fiber‐shaped Ni‐Fe batteries will enable textile‐based energy supply for wearable electronics. However, the development of fiber‐shaped Ni‐Fe batteries is currently challenged by the performance of fibrous Fe‐based anode materials. In this context, this study describes the fabrication of sulfur‐doped Fe₂O₃ nanowire arrays (S‐Fe₂O₃ NWAs) grown on carbon nanotube fibers (CNTFs) as an innovative anode material (S‐Fe₂O₃ NWAs/CNTF). Encouragingly, first‐principle calculations reveal that S‐doping in Fe₂O₃ can dramatically reduce the band gap from 2.34 to 1.18 eV and thus enhance electronic conductivity. The novel developed S‐Fe₂O₃ NWAs/CNTF electrode is further demonstrated to deliver a very high capacity of 0.81 mAh cm^?2 at 4 mA cm^?2. This value is almost sixfold higher than that of the pristine Fe₂O₃ NWAs/CNTF electrode. When a cathode containing zinc‐nickel‐cobalt oxide (ZNCO)@Ni(OH)₂ NWAs heterostructures is used, 0.46 mAh cm^?2 capacity and 67.32 mWh cm^?3 energy density are obtained for quasi‐solid‐state fiber‐shaped NiCo‐Fe batteries, which outperform most state‐of‐the‐art fiber‐shaped aqueous rechargeable batteries. These findings offer an innovative and feasible route to design high‐performance Fe‐based anodes and may inspire new development for the next‐generation wearable Ni‐Fe batteries.     

Import‐based Indicator for the Geopolitical Supply Risk of Raw Materials in Life Cycle Sustainability Assessments

There is a growing concern over the security and sustainable supply of raw material among businesses and governments of developed, material‐intensive countries. This has led to the development of a systematic analysis of risk incorporated with raw materials usage, often referred as criticality assessment. In principle, this concept is based on the material flow approach. The potential role of life cycle assessment (LCA) to integrate resource criticality through broadening its scope into the life cycle sustainability assessment (LCSA) framework has been discussed within the LCA communities for some time. In this article, we aim at answering the question of how to proceed toward integration of the geopolitical aspect of resource criticality into the LCSA framework. The article focuses on the assessment of the geopolitical supply risk of 14 resources imported to the seven major advanced economies and the five most relevant emerging countries. Unlike a few previous studies, we propose a new method of calculation for the geopolitical supply risk, which is differentiated by countries based on the import patterns instead of a global production distribution. Our results suggest that rare earth elements, tungsten, antimony, and beryllium generally pose high geopolitical supply risk. Results from the Monte Carlo simulation allow consideration of data uncertainties for result interpretation. Issues concerning the consideration of the full supply chain are exemplarily discussed for cobalt. Our research broadens the scope of LCA from only environmental performance to a resource supply‐risk assessment tool that includes accessibility owing to political instability and market concentration under the LCSA framework.     

Highly Efficient Oxygen Reduction Reaction Activity of Graphitic Tube Encapsulating Nitrided CoxFey Alloy

Nonprecious metals are promising catalysts to avoid the sluggish oxygen reduction reaction (ORR) in next‐generation regenerative fuel cells or metal–air batteries. Therefore, development of nonprecious metal catalysts for ORR is highly desirable. Herein, precise tuning of the atomic ratio of Fe and Co encapsulated in melamine‐derived nitrogen‐rich graphitic tube (NGT) is reported. The Co_1.08Fe_3.34 hybrid with metal? nitrogen bonds ( 1 : Co_1.08Fe_3.34@NGT) shows remarkable ORR catalytic activities (80 mV higher in onset potential and 50 mV higher in half‐wave potential than those of state‐of‐the‐art commercial Pt/C catalysts), high current density, and stability. In acidic solution, 1 also shows compatible performance to commercial Pt/C in terms of ORR activity, current density, stability, and methanol tolerance. The high ORR activity is ascribed to the co‐existence of Fe? N, Co? N, and sufficient metallic FeCo alloys which favor faster electron movement and better adsorption of oxygen molecules on the catalyst surface. In the alkaline anion exchange membrane fuel cell setup, this cell delivers the power density of 117 mW cm^?2, demonstrating its potential use for energy conversion and storage applications.     

Although there is no Physical Short‐Term Scarcity of Phosphorus,its Resource Efficiency Should be Improved

The German government has adopted a law that requires sewage plants to go beyond the recovery of phosphorus from wastewater and to promote recycling. We argue that there is no physical global short‐ or mid‐term phosphorus scarcity. However, we also argue that there are legitimate reasons for policies such as those of Germany, including: precaution as a way to ensure future generations’ long‐term supply security, promotion of technologies for closed‐loop economics in a promising stage of technology development, and decrease in the current supply risk with a new resource pool.     

Superior Lithium Storage Properties of β‐FeOOH

Several crystal forms of FeOOH are recently reported to be highly promising for lithium storage due to their high capacity, low cost, and environmental friendliness. In particular, β‐FeOOH has shown a capacity of ≈1000 mAh g^?1, which is comparable to other promising iron‐based anodes, such as Fe₂O₃ and Fe₃O_4. However, its storage mechanisms are unclear and the potential for further improvement remains unexplored. Here, it is shown that this material can have a very high reversible capacity of ≈1400 mAh g^?1, which is 20%–40% higher than Fe₂O₃ and Fe₃O₄. Such a high capacity is delivered from a series of reactions including intercalation and conversion reactions, formation/deformation of solid‐state electrolyte interface layers and interfacial storage. The mechanisms are studied by a combination of electrochemical and X‐ray absorption near edge spectroscopic approaches. Moreover, very long cycling performance, that is, after even more than 3000 cycles the material still has a significant capacity of more than 800 mAh g^?1, is obtained by a simple electrode design involving introducing a rigid support into porous electrodes. Such long cycling performance is for the first time achieved for high‐capacity materials based on conversion reactions.     

Rechargeable Iron–Sulfur Battery without Polysulfide Shuttling

Sulfur represents one of the most promising cathode materials for next‐generation batteries; however, the widely observed polysulfide dissolution/shuttling phenomenon in metal–sulfur redox chemistries has severely restricted their applications. Here it is demonstrated that when pairing the sulfur electrode with the iron metal anode, the inherent insolubility of iron sulfides renders the shuttling‐free nature of the Fe–S electrochemical reactions. Consequently, the sulfur electrode exhibits promising performance for Fe²⁺ storage, where a high capacity of ≈1050 mAh g^?1, low polarization of ≈0.16 V as well as stable cycling of 150 cycles are realized. The Fe–S redox mechanism is further revealed as an intriguing stepwise conversion of S₈ ? FeS₂ ? Fe₃S₄ ? FeS, where a low volume expansion of ≈32.6% and all‐solid‐state phase transitions facilitate the reaction reversibility. This study suggests an alternative direction to exploit sulfur electrodes in rechargeable transition metal–sulfur batteries.     

Concentration‐dependent studies of Nd3+‐doped zinc phosphate glasses for NIR photoluminescence at 1.05 μm

Nd³⁺‐doped lead‐free zinc phosphate glasses with the chemical compositions (60‐x) NH₄H₂PO₄ + 20ZnO + 10BaF₂ + 10NaF + xNd₂O₃ (where x = 0.5, 1.0, 1.5, 2.0 and 2.5 mol%) were prepared using a melt quenching technique. Vibrational bands were assigned and clearly elucidated by Raman spectral profiles for all the glass samples. Judd–Ofelt (J–O) intensity parameters (Ω_λ: λ = 2, 4, 6) were obtained from the spectral intensities of different absorption bands of Nd³⁺ ions. Radiative properties such as radiative transition probabilities (A_R), radiative lifetimes (τ_R) and branching ratios (β_R) for different excited states were calculated using J–O parameters. The near infrared (NIR) photoluminescence spectra exhibited three emission bands (⁴F_3/2 level to ⁴I_13/2, ⁴I_11/2 and ⁴I_9/2 states) for all the concentrations of Nd³⁺ ions. Various luminescence properties were studied by varying the Nd³⁺ concentration for the three spectral profiles. Fluorescence decay curves of the ⁴F_3/2 level were recorded. The energy transfer mechanism that leads to quenching of the ⁴F_3/2 state lifetimes was discussed at higher concentration of Nd³⁺ ions. These glasses are suggested as suitable hosts to produce efficient lasing action in NIR region at 1.05 μm.     

3D Porous γ‐Fe2O3@C Nanocomposite as High‐Performance Anode Material of Na‐Ion Batteries

A simple and template‐free method for preparing three‐dimensional (3D) porous γ‐Fe₂O₃@C nanocomposite is reported using an aerosol spray pyrolysis technology. The nanocomposite contains inner‐connected nanochannels and γ‐Fe₂O₃ nanoparticles (5 nm) uniformly embedded in a porous carbon matrix. The size of γ‐Fe₂O₃ nanograins and carbon content can be controlled by the concentration of the precursor solution. The unique structure of the 3D porous γ‐Fe₂O₃@C nanocomposite offers a synergistic effect to alleviate stress, accommodate large volume change, prevent nanoparticles aggregation, and facilitate the transfer of electrons and electrolyte during prolonged cycling. Consequently, the nanocomposite shows high‐rate capability and long‐term cyclability when applied as an anode material for Na‐ion batteries (SIBs). Due to the simple one‐pot synthesis technique and high electrochemical performance, 3D porous γ‐Fe₂O₃@C nanocomposites have a great potential as anode materials for rechargeable SIBs.     

Seasonal and within‐canopy variation in shoot‐scale resource‐use efficiency trade‐offs in a Norway spruce stand

Previous leaf‐scale studies of carbon assimilation describe short‐term resource‐use efficiency (RUE) trade‐offs where high use efficiency of one resource requires low RUE of another. However, varying resource availabilities may cause long‐term RUE trade‐offs to differ from the short‐term patterns. This may have important implications for understanding canopy‐scale resource use and allocation. We used continuous gas exchange measurements collected at five levels within a Norway spruce, Picea abies (L.) karst., canopy over 3 years to assess seasonal differences in the interactions between shoot‐scale resource availability (light, water and nitrogen), net photosynthesis (A_n) and the use efficiencies of light (LUE), water (WUE) and nitrogen (NUE) for carbon assimilation. The continuous data set was used to develop and evaluate multiple regression models for predicting monthly shoot‐scale A_n. These models showed that shoot‐scale A_n was strongly dependent on light availability and was generally well described with simple one‐ or two‐parameter models. WUE peaked in spring, NUE in summer and LUE in autumn. However, the relative importance of LUE for carbon assimilation increased with canopy depth at all times. Our results suggest that accounting for seasonal and within‐canopy trade‐offs may be important for RUE‐based modelling of canopy carbon uptake.     

Fe‐Based Tunnel‐Type Na0.61[Mn0.27Fe0.34Ti0.39]O2 Designed by a New Strategy as a Cathode Material for Sodium‐Ion Batteries

Sodium‐ion batteries are promising for grid‐scale storage applications due to the natural abundance and low cost of sodium. However, few electrodes that can meet the requirements for practical applications are available today due to the limited routes to exploring new materials. Here, a new strategy is proposed through partially/fully substituting the redox couple of existing negative electrodes in their reduced forms to design the corresponding new positive electrode materials. The power of this strategy is demonstrated through the successful design of new tunnel‐type positive electrode materials of Na_0.61[Mn_0.61‐xFe_xTi_0.39]O₂, composed of non‐toxic and abundant elements: Na, Mn, Fe, Ti. In particular, the designed air‐stable Na_0.61[Mn_0.27Fe_0.34Ti_0.39]O₂ shows a usable capacity of ≈90 mAh g^?1, registering the highest value among the tunnel‐type oxides, and a high storage voltage of 3.56 V, corresponding to the Fe³⁺/Fe⁴⁺ redox couple realized for the first time in non‐layered oxides, which was confirmed by X‐ray absorption spectroscopy and Mössbauer spectroscopy. This new strategy would open an exciting route to explore electrode materials for rechargeable batteries.     

Toward a dynamic evaluation of mineral criticality: Introducing the framework of criticality systems

A new methodology to quantify minerals’ criticalities is proposed—the criticality systems of minerals. In this methodology, four types of agents—mineral suppliers, consumers, regulators of the market, and others, such as the communities near mining operations—interact with each other through three types of indicators: constraints, such as the political stability in the mining regions, the mineral's substitutability and economic importance; agents’ interactions, such as buyer–seller bargaining; and interactive variables, such as the demand, supply, and price. When the criticality systems of two mineral groups are constructed, analyses that compare the indicators of these criticality systems can determine which group is more critical than the other. This methodology allows evaluation of criticality in a dynamic and systemic manner.     

Progress in High‐Voltage Cathode Materials for Rechargeable Sodium‐Ion Batteries

Room‐temperature rechargeable sodium‐ion batteries are considered as a promising alternative technology for grid and other storage applications due to their competitive cost benefit and sustainable resource supply, triumphing other battery systems on the market. To facilitate the practical realization of the sodium‐ion technology, the energy density of sodium‐ion batteries needs to be boosted to the level of current commercial Li‐ion batteries. An effective approach would be to elevate the operating voltage of the battery, which requires the use of electrochemically stable cathode materials with high voltage versus Na⁺/Na. This review summarizes the recent progress with the emerging high‐voltage cathode materials for room‐temperature sodium‐ion batteries, which include layered transitional‐metal oxides, Na‐rich materials, and polyanion compounds. The key challenges and corresponding strategies for these materials are also discussed, with an emphasis placed on the intrinsic structural properties, Na storage electrochemistry, and the voltage variation tendency with respect to the redox reactions. The insights presented in this article can serve as a guide for improving the energy densities of room‐temperature Na‐ion batteries.     

Electrochemical Activity of Hematite Phase in Full‐Cell Li‐ion Assemblies

Exploring negative electrodes for high‐performance Li‐ion power packs and related issues that are hampering their commercialization is a particularly important topic of research. This study investigates the electrochemical activity of low‐cost and typical conversion‐type hematite (α‐Fe₂O₃) anodes in practical assemblies, namely, full‐cell configurations. Numerous studies have reported improvements in the electrochemical activity of α‐Fe₂O₃ in half cells with Li by tuning the morphology or formulating composites with carbonaceous materials. However, these studies are not sufficient to market them for practical assemblies with conventional cathodes like LiCoO₂, LiMn₂O₄, LiFePO₄ and its derivatives, mainly because of large polarization problems, such as, hysteresis, irreversible capacity loss, volume variation, and capacity fading. Eliminating these issues in the fabrication of full cells is necessary, and this study reviews relevant research activities and discusses future prospects in the field.     

Self‐Assemble and In Situ Formation of Ni1−xFexPS3 Nanomosaic‐Decorated MXene Hybrids for Overall Water Splitting

Herein, the authors present the development of novel 0D–2D nanohybrids consisting of a nickel‐based bimetal phosphorus trisulfide (Ni_1?xFe_xPS₃) nanomosaic that decorates on the surface of MXene nanosheets (denoted as NFPS@MXene). The nanohybrids are obtained through a facile self‐assemble process of transition metal layered double hydroxide (TMLDH) on MXene surface; followed by a low temperature in situ solid‐state reaction step. By tuning the Ni:Fe ratio, the as‐synthesized NFPS@MXene nanohybrids exhibit excellent activities when tested as electrocatalysts for overall water splitting. Particularly, with the initial Ni:Fe ratio of 7:3, the obtained Ni_0.7Fe_0.3PS₃@MXene nanohybrid reveals low overpotential (282 mV) and Tafel slope (36.5 mV dec^?1) for oxygen evolution reaction (OER) in 1 m KOH solution. Meanwhile, the Ni_0.9Fe_0.1PS₃@MXene shows low overpotential (196 mV) for the hydrogen evolution reaction (HER) in 1 m KOH solution. When integrated for overall water splitting, the Ni_0.7Fe_0.3PS₃@MXene || Ni_0.9Fe_0.1PS₃@MXene couple shows a low onset potential of 1.42 V and needs only 1.65 V to reach a current density of 10 mA cm^?2, which is better than the all noble metal IrO₂ || Pt/C electrocatalyst (1.71 mV@10 mA cm^?2). Given the chemical versatility of Ni_1?xFe_xPS₃ and the convenient self‐assemble process, the nanohybrids demonstrated in this work are promising for energy conversion applications.     

High Performance Na0.5[Ni0.23Fe0.13Mn0.63]O2 Cathode for Sodium‐Ion Batteries

The synthesis of a new layered cathode material, Na_0.5[Ni_0.23Fe_0.13Mn_0.63]O₂, and its characterization in terms of crystalline structure and electrochemical performance in a sodium cell is reported. X‐ray diffraction studies and high resolution scanning electron microscopy images reveal a well‐defined P2‐type layered structure, while the electrochemical tests demonstrate excellent characteristics in terms of high capacity and cycle life. This performance, the low cost, and the environmental compatibility of its component poses Na_0.5[Ni_0.23Fe_0.13Mn_0.63]O₂ to be among the most promising materials for the next generation of sodium‐ion batteries.     

Carbon‐Coated Li3Nd3W2O12: A High Power and Low‐Voltage Insertion Anode with Exceptional Cycleability for Li‐Ion Batteries

The synthesis of carbon‐coated Li₃Nd₃W₂O₁₂ (C‐Li₃Nd₃W₂O₁₂), a low voltage insertion anode (0.3 V vs. Li) for a Li‐ion battery, is reported to exhibit extraordinary performance. The low voltage reversible insertion provides an increase in the energy density of Li‐ion power packs. For instance, C‐Li₃Nd₃W₂O₁₂ delivered an energy density of ≈390 Wh kg^?1 (based on cathode mass loading) when coupled with an LiMn₂O₄ cathode with an operating potential of 3.4 V. Furthermore, excellent cycling profiles are observed for C‐Li₃Nd₃W₂O₁₂ anodes both in half and full‐cell configurations. The full‐cell is capable of delivering very stable cycling profiles at high current rates (e.g., 2 C), which clearly suggests the high power capability of such garnet‐type anodes.     

Heterobinuclear Zn‐Ln (Ln = La,Nd, Eu,Gd, Tb,Er and Yb) complexes based on asymmetric Schiff‐base ligand: synthesis,characterization and photophysical properties

With a novel asymmetric Schiff‐base zinc complex ZnL (H₂L = N‐(3‐methoxysalicylidene)‐N′‐(5‐bromo‐3‐methoxysalicylidene)phenylene‐1,2‐diamine), obtained from phenylene‐1,2‐diamine, 3‐methoxysalicylaldehyde and 5‐bromo‐3‐methoxysalicylaldehyde, as the precursor, a series of heterobinuclear Zn‐Ln complexes [ZnLnL(NO₃)₃(CH₃CN)] (Ln = La, 1; Ln = Nd, 2; Ln = Eu, 3; Ln = Gd, 4; Ln = Tb, 5; Ln = Er, 6; Ln = Yb, 7) were synthesized by the further reaction with Ln(NO₃)₃·6H₂O, and characterized by Fourier transform‐infrared, fast atom bombardment mass spectroscopy and elemental analysis. Photophysical studies of these complexes show that the strong and characteristic near‐infrared luminescence of Nd³⁺, Yb³⁺and Er³⁺ with emissive lifetimes in the microsecond range has been sensitized from the excited state of the asymmetric Schiff‐base ligand due to effective intramolecular energy transfer; the other complexes do not show characteristic emission due to the energy gap between the chromophore and lanthanide ions. Copyright © 2012 John Wiley & Sons, Ltd.