Search

Sodium‐metal batteries (SMBs) are regarded as key for next‐generation energy storage due to their high theoretical energy and potential cost‐effectiveness. However, Na‐metal systems remain challenged by several factors, including uncontrollable metallic dendrite growth for liquid systems and unstable solid electrolyte interphase (SEI) with most organic electrolytes, which limit the feasibility of SMBs. Here, the authors detail the interrelated degradation mechanisms. Afterward, the recent advances in improving the electrochemical performance of SMBs are highlighted. The strategies can be subdivided into the following taxonomy: The utilization of three‐dimensional (3D) conductive skeletons; the introduction of protective layers; the development of compatible electrolyte systems; and the employment of alloy anodes. Designing deposition substrates for the "'hostless"' Na has a great effect on reducing the current density and buffering the plating‐stripping volume expansion. The artificial interface approach would introduce efficient mechanical modulus or film‐forming type barriers, which can inhibit detrimental parasitic reactions. Improved solvent‐electrolyte combinations and additives tailored for Na will promise to suppress Na dendrite growth by obtaining a more stable SEI. The formation of alloy phase with Na can tune the bulk properties of the metal per se. Finally, the research challenges and possible development directions of SMBs are also discussed. [ABSTRACT FROM AUTHOR]

Recycling cathode materials from spent lithium‐ion batteries (LIBs) is critical to a sustainable society as it will relief valuable but scarce recourse crises and reduce environment burdens simultaneously. Different from conventional hydrometallurgical and pyrometallurgical recycling methods, direct regeneration relies on non‐destructive cathode‐to‐cathode mode, and therefore, more time and energy‐saving along with an increased economic return and reduced CO2 footprint. This review retrospects the history of direct regeneration and discusses state‐of‐the‐art development. The reported methods, including high‐temperature solid‐state, hydrothermal/ionothermal, molten salt thermochemistry, and electrochemical method, are comparatively introduced, targeting at illustrating their underlying regeneration mechanism and applicability. Further, representative repairing and upcycling studies on wide‐applied cathodes, including LiCoO2 (LCO), ternary oxides, LiFePO4 (LFP), and LiMn2O4 (LMO), are presented, with an emphasis on milestone cases. Despite these achievements, there remain several critical issues that shall be addressed before the commercialization of the mentioned direct regeneration methods. [ABSTRACT FROM AUTHOR]

Sodium‐based layered oxide cathodes are competitive candidates for commercial sodium‐ion batteries owing to their high theoretical capacities, low costs, and simple synthesis. P3‐type layered oxides with large open channels enable fast Na+ transport and hence good rate performance. However, the lower crystal symmetry of P3‐type oxides and variation of Na+ contents in the Na layer during desodiation/sodiation lead to large electrostatic repulsion changes between TMO2 slabs (TM=Transition Metal), resulting in irreversible phase transitions, and fast performance degradation. Herein, a potential Na+ conductor Na2SeO4 is first found that it can be easily in situ grown on P3‐Na0.45Ni0.2Mn0.8O2 to form a novel heterostructure P3‐Na0.45Ni0.2Mn0.8O2/Na2SeO4. The synergy between P3‐Na0.45Ni0.2Mn0.8O2 and Na2SeO4 functions in promoting Na+ diffusion and suppressing P3‐O3 phase transitions upon deep sodiation, which results in recorded high‐rate capability (68.2% capacity retention with retained 83.9 mAh g−1 capacity at 6400 mA g−1) and superior cycling stability (capacity retention 75% after 1000 cycles) among all reported P3‐type cathodes. Thus, it is believed that this novel heterostructure design opens a new pathway to promote practical applications for layered oxide cathodes in sodium‐ion batteries. [ABSTRACT FROM AUTHOR]

High‐performance lithium‐ion batteries (LIBs) are required for the rising energy storage demand, while their development depends mainly on cathode materials. Vanadium‐based compounds are considered to be promising due to the feasibility of multielectron reactions arising from the rich valence states of vanadium (+2 to +5). Herein, for the first time the electrochemical properties of a vanadium‐based fluoroxide, β‐KVOF3, as a cathode for LIBs, are reported. After optimization, a reversible capacity as high as 274 mAh g−1, a stable 300 cycles lifetime, and an energy density comparable to LiFePO4 (650 vs 550 Wh kg−1) are achieved. Experiments and simulation study of reaction mechanism illustrate that such performance originates from the reversible V3+/V5+ redox reaction, high structural stability of β‐KVOF3, and the pseudocapacitive process during charging and discharging. This study reveals that β‐KVOF3 is a promising cathode for Li‐ion storage and provides a new design idea for developing high‐performance LIBs cathode materials. [ABSTRACT FROM AUTHOR]

Solid polymer electrolytes (SPEs) offer inherent advantages for battery applications, such as high safety and excellent processability, but their practical use is limited by challenges like low ionic conductivity, subpar mechanical properties, and instability of the electrode/electrolyte interface. Here, novel SPEs are developed by embedding 2D MXenes decorated at the surface with methoxypolyethylene glycol chains into poly(vinylidene fluoride)‐hexafluoropropylene matrices, enhanced with succinonitrile as a plasticizer. This innovative design improves the compatibility of the modified MXene in poly(vinylidene fluoride)‐hexafluoropropylene and, together with the synergistic effects of succinonitrile, promotes the dissociation of lithium salt. The SPE achieves ionic conductivity of 1.49 × 10−4 S cm−1 at 30 °C, and a Li‐ion transference number of 0.59. These results are supported by comprehensive experimental characterization, COMSOL simulations, and DFT calculations. This SPE enables stable and reversible Li plating/stripping for over 2100 h in Li/Li symmetric cells, while fabricated Li/LiFePO4 full cells deliver a notable capacity of 135.4 mAh g−1 with an average Coulombic efficiency of 98.9% after 100 cycles at 0.2 C. Furthermore, the Li/LiNi0.6Co0.2Mn0.2O2 full cells also demonstrate a capacity of 140.5 mAh g−1 after over 200 cycles at 0.5 C, showcasing an impressive capacity retention rate of 99.6%. [ABSTRACT FROM AUTHOR]

Kostengünstige elektrochemische Energiespeichersysteme (EESS) sind dringend erforderlich, um die Anwendung erneuerbarer Energiequellen wie Wind, Sonne usw. voranzutreiben. Die Geschichte der Lithium‐Ionen‐Batterien hat gezeigt, dass die Kosten von EESSs hauptsächlich von Ladungsträger‐Ionen und Redoxzentren in den Elektroden abhängen und ihre Leistung durch positive Elektroden begrenzt wird. In diesem Szenario bewertet dieser Kurzaufsatz mehrere EESS‐Kandidaten und fasst die bekannten gemischten polyanionischen Verbindungen (MPVs) zusammen – eine Familie mit robusten Strukturen und großen Kanälen für die Ionenspeicherung und ‐migration. Nach einer umfassenden Analyse wird darauf hingewiesen, dass eine tiefere Erforschung der MPVs zu einer Reihe neuartiger kristallographisch interessanter Verbindungen und ausgezeichneten Kathodenmaterialien für kostengünstige Energiespeicheranwendungen führen kann. [ABSTRACT FROM AUTHOR]

Low‐cost electrochemical energy storage systems (EESSs) are urgently needed to promote the application of renewable energy sources such as wind and solar energy. In analogy to lithium‐ion batteries, the cost of EESSs depends mainly on charge‐carrier ions and redox centers in electrodes, and their performance is limited by positive electrodes. In this context, this Minireview evaluates several EESS candidates and summarizes the known mixed polyanionic compounds (MPCs)—a family with robust frameworks and large channels for ion storage and migration. After comprehensive analysis, it is pointed out that a deeper exploration of MPCs may generate numerous novel crystallographically interesting compounds and excellent cathode materials for low‐cost energy storage applications. [ABSTRACT FROM AUTHOR]

Sodium‐ion batteries (NIBs) are the most promising alternatives to lithium‐ion batteries in the development of renewable energy sources. The advancement of NIBs depends on the exploration of new electrode materials and fundamental understanding of working mechanisms. Herein, via experimental and simulation methods, we develop a mixed polyanionic compound, Na2Fe(C2O4)SO4⋅H2O, as a cathode for NIBs. Thanks to its rigid three dimensional framework and the combined inductive effects from oxalate and sulfate, it delivered reversible Na insertion/desertion at average discharging voltages of 3.5 and 3.1 V for 500 cycles with Coulombic efficiencies of ca. 99 %. In situ synchrotron X‐ray measurements and DFT calculations demonstrate the Fe2+/Fe3+ redox reactions contribute to electron compensation during Na+ desertion/insertion. The study suggests mixed polyanionic frameworks may provide promising materials for Na ion storage with the merits of low cost and environmental friendliness. [ABSTRACT FROM AUTHOR]

A novel copper oxalate Na2Cu(C2O4)2 was synthesized through a hydrothermal method and characterized by single-crystal X-ray diffraction. It crystallizes in monoclinic system, P21/ n space group with a = 72578(3) Å, b = 5.7711(4) Å, c = 8.6604(8) Å, β = 106.948(9)°. The structure displays a novel stacking pattern of [Cu(C2O4)2]2- units connected through electrostatic attraction by Na+ cations. Structural comparisons are made to related compounds. [ABSTRACT FROM AUTHOR]

A novel copper oxalate Na2Cu(C2O4)2 was synthesized through a hydrothermal method and characterized by single-crystal X-ray diffraction. It crystallizes in monoclinic system, P21/ n space group with a = 72578(3) Å, b = 5.7711(4) Å, c = 8.6604(8) Å, β = 106.948(9)°. The structure displays a novel stacking pattern of [Cu(C2O4)2]2- units connected through electrostatic attraction by Na+ cations. Structural comparisons are made to related compounds. [ABSTRACT FROM AUTHOR]

The rapid development of deep‐UV (DUV) all‐solid‐state laser sources greatly depends on the good performance of the nonlinear optical (NLO) crystals used for harmonic generation. In this work, the potential prospects for NLO borate crystals are investigated from the point of view of their structure–property relationships. The microscopic structural units, energy bandgaps, linear and nonlinear optical properties of numerous borate compounds with diverse structural features are compared and summarized. The results reveal that KBe2BO3F2 almost achieves the theoretical limits of DUV NLO borates. It would be a great challenge to discover other borates which have comparable NLO capability, especially for coherent light production below the wavelength of 190 nm by direct second harmonic generation. [ABSTRACT FROM AUTHOR]

Although layered vanadium oxides are extensively studied for sodium‐ion batteries (SIBs), their broader application is hindered by the instability of their bulk‐phase structure, sluggish electron/ion‐transfer kinetics, and insufficient active sites. Herein, a novel synergistic strategy is proposed to modulate the electronic structure of VO by incorporating Na+ cations into deep V─O layers (D‐NVOx), resulting in significant structural modifications such as enlarged lattice spacing, the generation of abundant oxygen vacancies, and disordering of the V─O layers. Comprehensive analytical characterizations and theoretical calculations reveal that this synergy induces reversible Na+ pseudocapacitive intercalation and reconstructs low‐energy barrier channels, thereby accelerating Na‐ion diffusion kinetics. Moreover, the oxygen vacancies dramatically boost electronic conductivity and reinforce structural stability. The reduced crystallinity and lattice distortion result in dense nanointerfaces, potentially widening diffusion channels and providing additional active sites for fast surface Na‐ion storage. Owing to these merits, the D‐NVOx electrode achieves a high specific capacity (505 mAh g‒1 at 0.05 A g‒1), outstanding cyclic stability (96% capacity retention over 2000 cycles at 2.0 A g‒1), and superior rate performance (280 mAh g‒1 at 5.0 A g‒1). This work provides in‐depth insights into enhancing electrochemical energy storage in SIBs by modulating electronic structure and structural defects. [ABSTRACT FROM AUTHOR]

Metal hexacyanoferrates (MHCFs) with adjustable composition and open framework structures have been considered as intriguing cathode materials for sodium‐ion batteries (SIBs). Exploiting MHCFs with ultrafast and durable sodium storage capability as well as comparable capacity is always a goal that many investigators pursue, but remains challenging. Herein, simultaneous tailoring of chemical composition and morphology configuration is carried out to design a hollow monoclinic high‐entropy MHCF (HMHE‐HCF) assembled by nanocubes for the first time to realize the objective. The “cocktail effect” of high‐entropy construction, rich sodium content of monoclinic phase, and unique hollow structure endow HMHE‐HCF cathode with fast reaction kinetics and energetically stable performance during continuous charging/discharging processes. As a result, the HMHE‐HCF cathode demonstrates superior rate performance up to an ultra‐high rate of 100 C (71.1 % retention to 0.1 C), and remarkable cycling stability with a capacity retention of 77.8 % over 25,000 cycles at 100 C, outperforming most reported sodium‐ion cathodes. Further, the HMHE‐HCF//hard carbon full‐cell delivers capacities of 99.0 and 82.3 mAh g−1 at 0.1 C and 10 C, respectively, and retains 98.1 % of the initial capacity after 1,600 cycles at 5 C, demonstrating its potential application for sodium‐ion storage. [ABSTRACT FROM AUTHOR]

Ca‐ion based devices are promising candidates for next‐generation energy storage with high performance and low cost, thanks to its multielectrons, superior kinetics, as well as abundance (2500 times lithium). Because of the lack of an appropriate combination of suitable electrode materials and electrolytes, it is unsuccessful to attain a satisfactory performance on complete Ca‐ion energy storage devices. Here, the multiion reaction strategy is defined to construct a complete Ca‐ion energy storage device and a capacitor–battery hybrid mechanism is deliberately adopted. Profiting from the elaborate design, it exhibits a high reversible capacity of 92 mAh g−1, unmatchable rate capability, and a high capacity retention of 84% over 1000 cycles under room temperature, which is the best performance of reported Ca‐based energy storage devices. [ABSTRACT FROM AUTHOR]

Single crystals of the new title compound are prepared by melting mixtures of Na2CO3, CaCO3, LiF, BeO, and B2O3 with a molar ratio of 0.9:0.5:0.4:1:2 (Pt crucible, 900 °C). [ABSTRACT FROM AUTHOR]

SrBeB2O5 is prepared by repeated solid state reaction of stoichiometric amounts of SrCO3, BeO, and H3BO3 (muffle furnace, 1173 K, 48 h). [ABSTRACT FROM AUTHOR]

Single crystals of Sr8MgB18O36 are obtained by flux melting of SrCO3, MgO, H3BO3, and LiF (or NaF) in the molar ratio of 1:1:2:3. [ABSTRACT FROM AUTHOR]

The new title polyborate is synthesized by solid state reaction of stoichiometric mixtures of SrCO3, BeO, and H3BO3 (1253 K, 6 d) followed by spontaneous crystallization from a B2O3/NaF flux (melting, Pt crucible, 24 h, 10 K/d cooling rate). [ABSTRACT FROM AUTHOR]

Polycrystalline CsBe4(BO3)3 is prepared by solid state reaction of a stoichiometric mixture of Cs2CO3, BeO, and B2O3 (800 °C, 2 d, air). [ABSTRACT FROM AUTHOR]

The title fluorine beryllium borate crystal is grown by high temperature solid state reaction of CaCO3, SrCO3, BeO, B2O3, and NaF in stoichiometric amounts (710°C, 48 h). [ABSTRACT FROM AUTHOR]