Search Results (14)

Lithium–air batteries (LABs) possess the highest energy density among all energy storage systems, and have drawn widespread interest in academia and industry. However, many arduous challenges are still to be conquered, one of them is Li₂CO₃, which is a ubiquitous product in LABs. It is inevitably produced but difficult to decompose; therefore, Li₂CO₃ is perceived as the “Achilles’ heel of LABs”. Among various approaches to addressing the Li₂CO₃ issue, developing Li₂CO₃-decomposing redox mediators (RMs) is one of the most convenient and versatile, because they can be electrochemically oxidized at the gas cathode surface, then they diffuse to the solid-state products and chemically oxidize them, recovering the RMs to a pristine state and avoiding solid-state catalysts’ contact instability with Li₂CO₃. Furthermore, because of their function mechanism, they can double as catalysts for Li₂O₂/LiOH decomposition, which are needed in LABs/LOBs anyway regardless of Li₂CO₃ incorporation due to the sluggish kinetics of oxygen reduction/evolution reactions. This review summarizes the progress in Li₂CO₃-decomposing RMs, including halides, metal–chelate complexes, and metal-free organic compounds. The insights into and discrepancies in the mechanisms of Li₂CO₃ decomposition and corresponding catalysis processes are also discussed. Full article

After more than 30 years of delay compared to lithium-ion batteries, sodium analogs are now emerging in the market. This is a result of the concerns regarding sustainability and production costs of the former, as well as issues related to safety and toxicity. Electrode materials for the new sodium-ion batteries may contain available and sustainable elements such as sodium itself, as well as iron or manganese, while eliminating the common cobalt cathode compounds and copper anode current collectors for lithium-ion batteries. The multiple oxidation states, abundance, and availability of manganese favor its use, as it was shown early on for primary batteries. Regarding structural considerations, an extraordinarily successful group of cathode materials are layered oxides of sodium, and transition metals, with manganese being the major component. However, other technologies point towards Prussian blue analogs, NASICON-related phosphates, and fluorophosphates. The role of manganese in these structural families and other oxide or halide compounds has until now not been fully explored. In this direction, the present review paper deals with the different Mn-containing solids with a non-layered structure already evaluated. The study aims to systematize the current knowledge on this topic and highlight new possibilities for further study, such as the concept of entatic state applied to electrodes. Full article

Metal halide solid-state electrolytes (SSEs) (Li-M-X system, typically Li₃MX₆ and Li₂MX_4; M is metal or rare-earth element, X is halogen) exhibit significant potential in all solid-state batteries (ASSB) due to wide stability windows (0.36–6.71 V vs. Li/Li⁺), excellent compatibility with cathodes, and a water-mediated facile synthesis route for large-scale fabrication. Understanding the dynamics of Li⁺ transportation and the influence of the host lattice is the prerequisite for developing advanced Metal halide SSEs. Neutron powder diffraction (NPD), as the most cutting-edge technology, could essentially reflect the nuclear density map to determine the whole crystal structure. Through NPD, the Li+ distribution and occupation are clearly revealed for transport pathway analysis, and the influence of the host ion lattice on Li+ migration could be discussed. In this review, we stress NPD utilization in metal halide SSEs systems in terms of defect chemistry, phase transition, cation/anion disorder effects, dual halogen, lattice dynamics/polarizability, and in situ analysis of phase evolution. The irreplaceable role of NPD technology in designing metal halide SSEs with enhanced properties is stressed, and a perspective on future developments of NPD in metal halide SSEs is also presented. Full article

Solid-state lithium metal batteries offer superior energy density, longer lifespan, and enhanced safety compared to traditional liquid-electrolyte batteries. Their development has the potential to revolutionize battery technology, including the creation of electric vehicles with extended ranges and smaller more efficient portable devices. The employment of metallic lithium as the negative electrode allows the use of Li-free positive electrode materials, expanding the range of cathode choices and increasing the diversity of solid-state battery design options. In this review, we present recent developments in the configuration of solid-state lithium batteries with conversion-type cathodes, which cannot be paired with conventional graphite or advanced silicon anodes due to the lack of active lithium. Recent advancements in electrode and cell configuration have resulted in significant improvements in solid-state batteries with chalcogen, chalcogenide, and halide cathodes, including improved energy density, better rate capability, longer cycle life, and other notable benefits. To fully leverage the benefits of lithium metal anodes in solid-state batteries, high-capacity conversion-type cathodes are necessary. While challenges remain in optimizing the interface between solid-state electrolytes and conversion-type cathodes, this area of research presents significant opportunities for the development of improved battery systems and will require continued efforts to overcome these challenges. Full article

Optimized vertical heterojunction rectifiers with a diameter of 100 µm, consisting of sputter-deposited p-type NiO forming a p–n junction with thick (10 µm) Ga₂O₃ drift layers grown by halide vapor phase epitaxy (HVPE) on (001) Sn-doped (10¹⁹ cm⁻³) β-Ga₂O₃ substrates, exhibited breakdown voltages >8 kV over large areas (>1 cm²). The key requirements were low drift layer doping concentrations (<10¹⁶ cm³), low power during the NiO deposition to avoid interfacial damage at the heterointerface and formation of a guard ring using extension of the NiO beyond the cathode metal contact. Breakdown still occurred at the contact periphery, suggesting that further optimization of the edge termination could produce even larger breakdown voltages. On-state resistances without substrate thinning were <10 mΩ.cm⁻², leading to power figure-of-merits >9 GW.cm⁻². The devices showed an almost temperature-independent breakdown to 600 K. These results show the remarkable potential of NiO/Ga₂O₃ rectifiers for performance beyond the limits of both SiC and GaN. The important points to achieve the excellent performance were: (1) low drift doping concentration, (2) low power during the NiO deposition and (3) formation of a guard ring. Full article

Water-based lubrication faces the common challenge of component lifetime extension which is impaired by tribocorrosion due to material surface depassivation. However, such mechanisms in a pH-neutral and low-halide electrolyte require additional understanding. A ball-on-flat configuration study of hard-phase materials in a low amplitude–high frequency sliding contact against martensitic chromium steel with contact pressures around 200 MPa is presented. Under lubrication by purified water, tungsten carbide-based metal matrix composite (MMC) with NiCr binder and silicon nitride-based ceramic (SiAlON) against DIN/EN 1.4108 steel yielded coefficients of friction above unity. Wear scar enlargement led to fretting-like conditions with adhesion becoming the fundamental wear mechanism. A tribocorrosion-induced depletion of tungsten carbide and nickel was determined for MMC. SiAlON materials suffered extreme wear under the formation of abrasive SiO₂, while heat-treated DIN/EN 1.4125 steel showed lower friction and wear, but also showed signs of hydrogen embrittlement. Results from accompanying single-material corrosion experiments could not satisfactorily explain the phenomena. Including galvanic interaction and the influence of contact geometry, a new tribocorrosion model for fretting conditions is proposed. It describes an expanding anodic belt located at the inner-most crevice position of an otherwise cathodically polarized material. Low conductivity of the electrolyte is seen as a key player in this process, while the galvanic situation between two materials in contact was shown to invert when water was substituted by a wet organic phase. Full article

Carbon capture, utilisation and storage (CCUS) is a key area of research for CO₂ abatement. To that end, CO₂ capture, transport and storage has accrued several decades of development. However, for successful implementation of CCUS, utilisation or conversion of CO₂ to valuable products is important. Electrochemical conversion of the captured CO₂ to desired products provides one such route. This technique requires a cathode “electrocatalyst” that could favour the desired product selectivity. Copper (Cu) is unique, the only metal “electrocatalyst” demonstrated to produce C₂ products including ethylene. In order to achieve high-purity Cu deposits, electrodeposition is widely acknowledged as a straightforward, scalable and relatively inexpensive method. In this review, we discuss in detail the progress in the developments of electrodeposited copper, oxide/halide-derived copper, copper-alloy catalysts for conversion of CO₂ to valuable products along with the future challenges. Full article

Organic–inorganic halide two-dimensional (2D) layered perovskites have been demonstrated to have better environmental stability than conventional three-dimensional perovskites. In this study, we investigate the fabrication of electron transport layer (ETL)-free Ruddlesden–Popper 2D perovskite solar cells (PSCs) by tuning the work function of a fluorine-doped tin oxide (FTO) electrode. With the deposition of polyethylenimine (PEIE) onto its surface, the work function of the FTO electrode could be raised from −4.72 to −4.08 eV, which is more suitable for electron extraction from the perovskite absorber. Using this technique, the ETL-free 2D PSCs exhibited an excellent power conversion efficiency (PCE) of 12.7% (on average), which is substantially higher than that of PSCs fabricated on a pristine FTO electrode (9.6%). Compared with the PSCs using TiO₂, the ETL-free PSCs could be fabricated under a low processing temperature of 100 °C with excellent long-term stability. After 15 days, the FTO/PEIE-based ETL-free PSCs showed a PCE degradation of 16%, which is significantly lower than that of the TiO₂-based case (29%). The best-performing PSC using a FTO/PEIE cathode showed a high PCE of 13.0%, with a small hysteresis degree of 2.3%. Full article

Electron transporting layers facilitating electron extraction and suppressing hole recombination at the cathode are crucial components in any thin-film solar cell geometry, including that of metal–halide perovskite solar cells. Amorphous tantalum oxide (Ta₂O₅) deposited by spin coating was explored as an electron transport material for perovskite solar cells, achieving power conversion efficiency (PCE) up to ~14%. Ultraviolet photoelectron spectroscopy (UPS) measurements revealed that the extraction of photogenerated electrons is facilitated due to proper alignment of bandgap energies. Steady-state photoluminescence spectroscopy (PL) verified efficient charge transport from perovskite absorber film to thin Ta₂O₅ layer. Our findings suggest that tantalum oxide as an n-type semiconductor with a calculated carrier density of ~7 × 10¹⁸/cm³ in amorphous Ta₂O₅ films, is a potentially competitive candidate for an electron transport material in perovskite solar cells. Full article

Transitioning from fossil fuels to renewable energy sources is a critical goal to address greenhouse gas emissions and climate change. Major improvements have made wind and solar power increasingly cost-competitive with fossil fuels. However, the inherent intermittency of renewable power sources motivates pairing these resources with energy storage. Electrochemical energy storage in batteries is widely used in many fields and increasingly for grid-level storage, but current battery technologies still fall short of performance, safety, and cost. This review focuses on sodium metal halide (Na-MH) batteries, such as the well-known Na-NiCl₂ battery, as a promising solution to safe and economical grid-level energy storage. Important features of conventional Na-MH batteries are discussed, and recent literature on the development of intermediate-temperature, low-cost cathodes for Na-MH batteries is highlighted. By employing lower cost metal halides (e.g., FeCl₂, and ZnCl₂, etc.) in the cathode and operating at lower temperatures (e.g., 190 °C vs. 280 °C), new Na-MH batteries have the potential to offer comparable performance at much lower overall costs, providing an exciting alternative technology to enable widespread adoption of renewables-plus-storage for the grid. Full article

The energy storage industry has expanded globally as costs continue to fall and opportunities in consumer, transportation, and grid applications are defined. As the rapid evolution of the industry continues, it has become increasingly important to understand how varying technologies compare in terms of cost and performance. This paper defines and evaluates cost and performance parameters of six battery energy storage technologies (BESS)—lithium-ion batteries, lead-acid batteries, redox flow batteries, sodium-sulfur batteries, sodium-metal halide batteries, and zinc-hybrid cathode batteries—four non-BESS storage systems—pumped storage hydropower, flywheels, compressed air energy storage, and ultracapacitors—and combustion turbines. Cost and performance information was compiled based on an extensive literature review, conversations with vendors and stakeholders, and costs of systems procured at sites across the United States. Detailed cost and performance estimates are presented for 2018 and projected out to 2025. Annualized costs were also calculated for each technology. Full article

Indium tin oxide (ITO) film is one of the ideal candidates for transparent conductive cathode in methylammonium lead halide perovskite solar cells. Thus, the diffusion of methyl group in ITO film is inevitable, which could deteriorate the optical-electrical property of ITO film. In this study, ITO films with and without (100) preferred orientation were bombarded by the low-energy methyl group beam. After the bombardment, the optical-electrical property of ITO film without (100) preferred orientation deteriorated. The bombardment of methyl group had little influence on the optical-electrical property of ITO film with (100) preferred orientation. Finally, combining the crystallographic texture and chemical bond structure analysis, the diffusion mechanism of low-energy methyl group on ITO lattice and grain boundary, as well as the relation between the optical-electrical property and the diffusion of the methyl group, were discussed systematically. With the above results, ITO film with (100) preferred orientation could be an ideal candidate for transparent conductive cathode in methylammonium lead halide perovskite solar cells. Full article

Galvanic replacement is the spontaneous replacement of surface layers of a metal, M, by a more noble metal, M_noble, when the former is treated with a solution containing the latter in ionic form, according to the general replacement reaction: nM + mM_nobleⁿ⁺ → nM^m+ + mM_noble. The reaction is driven by the difference in the equilibrium potential of the two metal/metal ion redox couples and, to avoid parasitic cathodic processes such as oxygen reduction and (in some cases) hydrogen evolution too, both oxygen levels and the pH must be optimized. The resulting bimetallic material can in principle have a M_noble-rich shell and M-rich core (denoted as M_noble(M)) leading to a possible decrease in noble metal loading and the modification of its properties by the underlying metal M. This paper reviews a number of bimetallic or ternary electrocatalytic materials prepared by galvanic replacement for fuel cell, electrolysis and electrosynthesis reactions. These include oxygen reduction, methanol, formic acid and ethanol oxidation, hydrogen evolution and oxidation, oxygen evolution, borohydride oxidation, and halide reduction. Methods for depositing the precursor metal M on the support material (electrodeposition, electroless deposition, photodeposition) as well as the various options for the support are also reviewed. Full article

We have successfully developed a novel cathodic cross-coupling reaction of aryl halides with arenes. Utilization of the cathodic single electron transfer (SET) mechanism for activation of aryl halides enables the cross-coupling reaction to proceed without the need for any transition metal catalysts or single electron donors in a mild condition. The SET from a cathode to an aryl halide initiates a radical chain by giving an anion radical of the aryl halide. The following propagation cycle also consists entirely of anion radical intermediates. Full article