In the pursuit of more affordable battery technologies, potassium-ion batteries (KIBs) have emerged as a promising alternative to lithium-ion systems, owing to the abundance and wide distribution of potassium resources. While chalcogenides are uncommon as intercalation cathodes in KIBs, this study's electrochemical tests on CrSe2 revealed a reversible K+ intercalation/deintercalation process. The CrSe2 cathode achieved a KIB battery capacity of 125 mA h g-1 at a 0.1C rate within a practical 1-3.5 V vs. K+/K operation range, nearly matching the theoretical capacity of 127.7 mA h g-1. Notably, the battery retained 85% of its initial capacity at a high 1C rate, suggesting that CrSe2 is competitive for high-power applications with many current state-of-the-art cathodes. In-operando PXRD studies uncovered the nature of the intercalation behavior, revealing an initial biphasic region followed by a solid-solution formation during the potassium intercalation process. DFT calculations helped with the possible assignment of intermediate phase structures across the entire CrSe2-K1.0CrSe2 composition range, providing insights into the experimentally observed phase transformations. The results of this work underscore CrSe2's potential as a high-performance cathode material for KIBs, offering valuable insights into the intercalation mechanisms of layered transition metal chalcogenides and paving the way for future advancements in optimizing KIB cathodes.

The present work investigates the influence of ultrasonic irradiation on the properties of ZnO nanostructures. Slurries of ZnO prior formed by co-precipitation were irradiated by low-power ultrasound for different times. The properties of the samples were characterized by X-ray diffraction (XRD), extended X-ray absorption fine structure (EXAFS), Fourier transformed infrared (FTIR) absorption, scanning electron microscopy (SEM) and photoluminescence (PL). Ultrasonic waves induced significant variation in morphology of the particles. Needles, rods, rice-like and fragmented particles were detected in different treated samples. The irradiation also led to the formation of different types of point defects in the ZnO structure, varying in nature and density, which in turn affected the structural local ordering and luminescent efficiency. A possible growth mechanism of the particles is presented, and the type and origin of the formed point defects are discussed.

Phosphate-based glasses (PBGs) are bioresorbable materials that find application in the field of controlled drug delivery and tissue engineering. The structural arrangements of the phosphate units in PBGs, along with the knowledge of how therapeutic metallic ions are embedded in the phosphate network are important in understanding the degradation and targeted release properties of these materials. Using a combination of Raman spectroscopy, high-energy X-ray diffraction and 31P and 23Na solid-state magic angle spinning nuclear magnetic resonance, the atomic structure of coacervate PBGs in the system P2O5-CaO-Na2O-MOx (M = Cu or Zn) with loadings of 2, 10 and 15 mol % of M2+ have been studied as functions of composition and calcination temperature. After drying at room temperature, the structures of the phosphate network in PBG-Cu and PBG-Zn are quite similar, with that of PBG-Zn exhibiting slightly higher connectivity. Heating at 300 degrees C causes degradation of the polyphosphate chains, even though Q2 species remain predominant. X-ray photoelectron spectroscopy demonstrates that Cu in calcined PBGs is present in both oxidation states +1 and +2, with a predominance of the +2 state. Cu and Zn ion release data after 24 h exposure of PBGs in deionized water and cell medium DMEM show that release is proportional to their loadings. Cytotoxicity MTT assays of dissolution products of PBG-Cu/ ZnX calcined at 300 degrees C on human osteosarcoma cells (MG-63) and on human skin cells (HaCaTs) showed good cellular response for all compositions, indicating that PBGs have great potential for both hard and soft tissue regeneration.

Phosphate-based glasses are a very promising class of multifunctional biomaterials. Being bioresorbable, they are capable of inducing simultaneous regeneration of tissue and delivery of drugs/therapeutic molecules and ions. Therefore, they can be used both as temporary implants and as controlled local delivery systems. Biomaterial-related infections, often causing revision surgery, could be prevented by incorporating into the biomaterial device antimicrobial agents that will be slowly released as the implant degrades. To date, the conventional technique used to prepare phosphate-based glasses is the melt-quenching process, which requires the melting of oxide powders at high temperatures (1000–1200 °C) followed by rapid cooling. However, this method often leads to non-homogeneous, bulk glasses that cannot be used for hosting temperature-sensitive molecules and can lead to reduction of antibacterial ions. Composition is also difficult to control because of the loss of volatile phosphate species during heating. This chapter describes two in-solution techniques for the synthesis of phosphate-based glasses alternative to the melt-quenching one: sol–gel and coacervation. A review of the literature published so far on the topics and a summary of key results is presented.

Objectives: Antibiotic resistance is increasingly a growing global threat. This study aimed to investigate the potential use of newly developed scandium-doped phosphate-based glasses (Sc-PBGs) as an antibacterial and anticariogenic agent through controlled release of Sc3+ ions. Methods: Sc-PBGs with various calcium and sodium oxide contents were produced and characterised using thermal and spectroscopic analysis. Degradation behaviour, ion release, antibacterial action against Streptococcus mutans, anti-matrix metalloproteinase-2 (MMP-2) activity, remineralisation potential and in vivo biocompatibility were also investigated. Results: The developed glass system showed linear Sc3+ ions release over time. The released Sc3+ shows statistically significant inhibition of S. mutans biofilm (1.2 log(10) CFU reduction at 6 h) and matrix metalloproteinase-2 (MMP-2) activity, compared with Sc-free glass and positive control. When Sc-PBGs were mounted alongside enamel sections, subjected to acidic challenges, alternating hyper- and hypomineralisation layers consistent with periods of re- and demineralisation were observed demonstrating their potential remineralising action. Furthermore, Sc-PBGs produced a non-toxic response when implanted subcutaneously for 2 weeks in Sprague Dawley rats. Significance: Since Sc3+ ions might act on various enzymes essential to the biological mechanisms underlying caries, Sc-PBGs could be a promising therapeutic agent against cariogenic bacteria. (C) 2021 The Academy of Dental Materials. Published by Elsevier Inc. All rights reserved.

Phosphate-based glasses (PBGs) are traditionally prepared using the high-temperature melt-quenching (MQ) route or via the more recent sol−gel (SG) method that requires the use of organic solvents. The coacervation method represents an excellent inexpensive and green alternative to MQ and SG, being performed in aqueous solution and at room temperature. Coacervation is particularly applicable for the production of PBGs designed for biomedical applications because it allows for the inclusion of temperature-sensitive molecules and does not require the use of toxic solvents. Whereas the atomic structure of the MQ and SGPBGs is known, the atomic structure of those prepared via coacervation has yet to be investigated. In this study, a comprehensive advanced structural characterization has been performed on phosphate-based glasses in the system P2O5−CaO−Na2O−Ag2O (Ag2O mol % = 0, 1, 3, 5, 9, and 14) prepared via the coacervation method. Glasses within this system should find application as bioresorbable biomaterials thanks to their ability to release bioactive ions in a controlled manner. In particular, they possess antibacterial properties, inferred by the release of Ag over time. High-energy X-ray diffraction (HEXRD), P and Na solid-state magic-angle spinning nuclear magnetic resonance (MAS NMR), and X-ray absorption Spectroscopy (XAS) at the Ag K-edge were used to probe the atomic structure of the glasses after drying in vacuum and after calcination at 300 °C. The length of the polyphosphate chains in the solid state appears to be independent of silver concentration; however, significant degradation of these chains is seen after calcination at 300 °C. Atomic-scale characterisation results indicate that the structure of these glasses is akin to that of other silver-doped phosphate glasses prepared using the MQ and SG methods. This suggests that phosphate-based glasses prepared using milder and greener conditions may have similar chemical and physical properties such as solubility, biocompatibility, and antibacterial properties.

Increased demand for lithium products for use in lithium-ion batteries has led to a search for new lithium resources in recent years to meet projected future consumption. One potential lithium resource is low lithium bearing brines that are discharged from hydraulically fractured oil and gas wells as flowback and produced water (FPW). In this way, hydraulic fracturing presents an opportunity to turn what is normally considered wastewater into a lithium resource. In this research, two manganese-based lithium-selective adsorbents were prepared using a co-precipitation method and were employed for lithium recovery from FPW. At optimized conditions, lithium uptake reached 18 mg g(-1) , with a > 80% lithium recovery within 30 min. The recovered lithium was isolated and concentrated to 15 mM in an acidic final product. The degree of sorbent loss during acid desorption of lithium was significantly higher for sorbents used in the FPW as compared to recovery from a synthetic lithium bearing brine (4.5% versus 0.8%). Thus, we propose that organic molecules present in the FPW reduce manganese in the sorbent structure during lithium sorption, leading to increased sorbent loss through reductive dissolution. Systematic characterization including wet chemical manganese valence measurements, along with EXAFS, XPS, and TEM-EELS show that exposure to FPW causes tetravalent manganese in the bulk sorbent structure to be reduced during lithium sorption, which subsequently dissolves during acid desorption. Partial removal of these organic molecules by nanofiltration leads to decreased sorbent dissolution in acid. In this way, we show that dissolved organic molecules represent a critical control on the reductive dissolution of manganese based lithium ion exchange sorbents. This research provides promising results on the use of manganese-based lithium sorbents in FPW.

The effects of mechanochemical synthesis and postsynthetic grinding on the spin crossover material [Fe(atrz)3](BF4)2 was examined in detail using a combination of X-ray diffraction, magnetometry, EXAFS and TEM. Mechanochemical synthesis yielded a different polymorph (β-phase) to the solution synthesised sample (α-phase), with a lower temperature spin crossover. Milling duration did not significantly affect this temperature but did result in the production of smaller nanoparticles with a narrower size distribution. It is also possible to convert from α- to the β-phase via postsynthetic grinding.

Lithium-rich layered oxides and sodium layered oxides represent attractive positive electrode materials exhibiting excess capacity delivered by additional oxygen redox activity. However, structural degradation in the bulk and detrimental reactions with the electrolyte on the surface often occur, leading to limited reversibility of oxygen redox processes. Here, we present the properties of P3-type Na0.67Mg0.2Mn0.8O2 synthesized under both air and oxygen. Both materials exhibit stable cycling performance in the voltage range of 1.8-3.8 V, where the Mn3+/Mn4+ redox couple entirely dominates the electrochemical reaction. Oxygen redox activity is triggered for both compounds in the wider voltage window 1.8-4.3 V with typical large voltage hysteresis from nonbonding O 2p states generated by substituted Mg. Interestingly, for the compound prepared under oxygen, an additional novel reversible oxygen redox activity is shown with an exceptionally small voltage hysteresis (20 mV). The presence of vacancies in the transition-metal layers is shown to play a critical role not only in forming unpaired O 2p states independent of substituted elements but also in stabilizing the P3 structure during charge with reduced structural transformation to the O'3 phase at the end of discharge. This study reveals the important role of vacancies in P3-type sodium layered oxides to increase energy density using both cationic and anionic redox processes.

Increasing dependence on rechargeable batteries for energy storage calls for the improvement of energy density of batteries. Toward this goal, introduction of positive electrode materials with high...

Defects of various types in crystalline and nanocrystalline materials govern a range of electrical, optical and mechanical properties. In particular, they are at the heart of translational ion dynamics in solid electrolytes. One of the most prominent examples revealing a drastic increase in ionic conductivity sigma(DC) by several orders of magnitude when going from an ordered crystalline matrix to a structurally disordered one is lithium tantalate. Here, structurally disordered, nanocrystalline LiTaO3 served as a model substance to shed light on the question to what extent the degree of disorder decreases upon annealing an originally defect-rich oxide. Disorder can be introduced by high-energy ball milling of LiTaO3 crystallites with diameters in the mu m range. Broadband conductivity spectroscopy, EXAFS and positron annihilation lifetime spectroscopy were used to correlate ion transport properties with interatomic distances, bond distortions and positron lifetimes. It turned out that milling times of only 30 min are sufficient to generate a highly defective oxide. Upon annealing at temperatures of T = 200 degrees C the defects can almost be preserved. Annealing at 750 degrees C for 1 h is needed to induce healing of the defects. Although we observe a recovery of the original interatomic distances and an increase in activation energy E-a for ionic transport from 0.75 eV to 0.81 eV, the initial transport properties of the unmilled sample (0.97 eV) cannot be fully restored. Most interestingly, the change in E-a is accompanied by a change of the entropy-controlled Arrhenius pre-factor governing the temperature dependence of sigma T-DC. Moreover, positron lifetimes remain high in the annealed samples. Hence, our results point to samples with fewer distortions but still rich in vacancy-type defects. Altogether, the combination of ball milling and annealing helps adjust ionic conductivities in LiTaO3 to vary over 4 to 5 orders of magnitude.

Correction for ‘Lithiation of V2O3(SO4)2 – a flexible insertion host’ by Stephanie F. Linnell et al., J. Mater. Chem. A, 2020, DOI: 10.1039/d0ta06608g.

Materials that display strong capabilities for lithium insertion without significant change in unit cell size on cycling are of considerable importance for electrochemical applications. Here, we present V2O3(SO4)(2)as a host for lithium-ion batteries. Electrochemically, 2.0 Li(+)ions can be inserted, giving Li2V2O3(SO4)(2)with an oxidation state of V4+, as determined by X-ray absorption spectroscopy. The capacity of V2O3(SO4)(2)can be increased from 157 mA h g(-1)to 313 mA h g(-1)with the insertion of two additional Li(+)ions which would drastically improve the energy density of this material, but this would be over a wider potential range. Chemical lithiation usingn-butyllithium was performed and characterisation using a range of techniques showed that a composition of Li4V2O3(SO4)(2)can be obtained with an oxidation state of V3+. Structural studies of the lithiated materials by X-ray diffraction showed that up to 4.0 Li(+)ions can be inserted into V2O3(SO4)(2)whilst maintaining its framework structure.

Additional capacity delivered by oxygen redox activity may in principle represent a means of enhancing the electrochemical performance of layered sodium transition metal oxides. However, irreversible structural changes occurring during cycling typically cause significant capacity fade with limited reversibility of oxygen redox processes. Here, P3-structure Na0.67Co0.2Mn0.8O2 was synthesised under two different reaction conditions. Both materials exhibit very stable cycling performance in the voltage range 1.8-3.8 V where the redox couples of transition metals entirely dominate the electrochemical reaction. For the compound prepared under more oxidising conditions, anion redox activity is triggered in the wider voltage window 1.8-4.4 V in a reversible manner with exceptionally small voltage hysteresis (20 mV). The presence of vacancies in the transition metal layers is shown to play a critical role not only in generating unpaired O 2p states but also in stabilising the crystal structure in the high voltage region.

It is possible to increase the charge capacity of transition metal (TM) oxide cathodes in alkali-ion batteries by invoking redox reactions on the oxygen. However, oxygen loss often occurs. To explore what affects oxygen loss in oxygen redox materials, we have compared two analogous Na-ion cathodes, P2-Na0.67Mg0.28Mn0.72O2 and P2-Na0.78Li0.25Mn0.75O2. On charging to 4.5 V, >0.4e(-) are removed from the oxide ions of these materials, but neither compound exhibits oxygen loss. Li is retained in P2-Na0.78Li0.25Mn0.25O2 but displaced from the TM to the alkali metal layers, showing that vacancies in the TM layers, which also occur in other oxygen redox compounds that exhibit oxygen loss such as Li[Li0.2Ni0.2Mn0.6]O-2, are not a trigger for oxygen loss. On charging at 5 V, P2-Na0.78Li0.25Mn0.75O2 exhibits oxygen loss, whereas P2-Na0.67Mg0.28Mn0.72O2 does not. Under these conditions, both Na+ and Li+ are removed from P2-Na0.78Li0.25Mn0.75O2, resulting in underbonded oxygen (fewer than 3 cations coordinating oxygen) and surface-localized O loss. In contrast, for P2-Na0.67Mg0.28Mn0.72O2, oxygen remains coordinated by at least 2 Mn4+ and 1 Mg2+ ions, stabilizing the oxygen and avoiding oxygen loss.

Phosphate-based glasses are materials of great interest for the regeneration and repair of damaged hard or soft tissues. They have the desirable property of slowly dissolving in the physiological environment, eventually being totally replaced by regenerated tissue. Being bioresorbable, they can simultaneously induce tissue regeneration and deliver therapeutic agents (e.g. antibacterial ions) in a controlled way. In this work, we have synthesised a series of glasses in the P2O5-CaO-Na2O system doped with Ag2O using the coacervation method. The addition of silver is known to provide the glass with antibacterial properties due to the release of Ag+ ions into the body fluid. The coacervation method is a facile, water-based technique which offers significant advantages over the conventional melt-quench route for preparing phosphate-based glasses which requires melting of metal oxide powders at high temperatures (1000-1200 °C). The properties of the initial colloidal polyphosphate systems (coacervates) as a function of the Ag2O content were characterised using rheology and liquid state 31P NMR. The effect of Ag+ addition on the final dried glasses was investigated using thermal analysis, Raman spectroscopy and X-ray diffraction. The antibacterial activity was assessed against Staphylococcus aureus (S. aureus), a bacterial strain commonly found in post-surgery infections. A dose-dependent antimicrobial effect was seen with an increasing silver content.

The search for improved energy-storage materials has revealed Li- and Na-rich intercalation compounds as promising high-capacity cathodes. They exhibit capacities in excess of what would be expected from alkali-ion removal/reinsertion and charge compensation by transition-metal (TM) ions. The additional capacity is provided through charge compensation by oxygen redox chemistry and some oxygen loss. It has been reported previously that oxygen redox occurs in O 2p orbitals that interact with alkali ions in the TM and alkali-ion layers (that is, oxygen redox occurs in compounds containing Li+-O(2p)-Li+ interactions). Na2/3[Mg0.28Mn0.72]O2 exhibits an excess capacity and here we show that this is caused by oxygen redox, even though Mg2+ resides in the TM layers rather than alkali-metal (AM) ions, which demonstrates that excess AM ions are not required to activate oxygen redox. We also show that, unlike the alkali-rich compounds, Na2/3[Mg0.28Mn0.72]O2 does not lose oxygen. The extraction of alkali ions from the alkali and TM layers in the alkali-rich compounds results in severely underbonded oxygen, which promotes oxygen loss, whereas Mg2+ remains in Na2/3[Mg0.28Mn0.72]O2, which stabilizes oxygen.

The defect density of a material is central to its properties. Here, we show, employing EXAFS measurements and MD simulation, how the Ba-Li antisite defect density of perovskite-structured BaLiF3 nanoparticles can be tuned. In particular, we show that ball milling reduces the defect content. Conversely, thermal annealing increases the defect density. The work represents a first step toward tailoring the properties of a material via defect tuning postsynthesis.

The rhodium(III) hydrogarnets Ca3Rh2(OH)12 and Sr3Rh2(OH)12 crystallize as polycrystalline powders under hydrothermal conditions at 200 °C from RhCl3·3H2O and either Ca(OH)2 or Sr(OH)2 in either 12 M NaOH or KOH. Rietveld refinements against synchrotron powder X-ray diffraction (XRD) data allow the first crystal structures of the two materials to be determined. If BaO2 is used as a reagent and the concentration of hydroxide increased to hydroflux conditions (excess NaOH), then single crystals of a new complex rhodium hydroxide, BaNaRh(OH)6, are formed in a phase-pure sample, with sodium included from the flux. Structure solution from single-crystal XRD data reveals isolated octahedral Rh centers that share hydroxides with 10-coordinate Ba and two independent 8-coordinate Na sites. 23Na magic-angle spinning NMR confirms the presence of the two crystallographically distinct Na sites and also verifies the diamagnetic nature of the sample, expected for Rh(III). The thermal behavior of the hydroxides on heating in air was investigated using X-ray thermodiffractometry, showing different decomposition pathways for each material. Ca3Rh2(OH)12 yields CaRh2O4 and CaO above 650 °C, from which phase-pure CaRh2O4 is isolated by washing with dilute nitric acid, a material previously only reported by high-pressure or high-temperature synthesis. Sr3Rh2(OH)12 decomposes to give a less crystalline material with a powder XRD pattern that is matched to the 2H-layered hexagonal perovskite Sr6Rh5O15, which contains mixed-valent Rh3+/4+, confirmed by Rh K-edge XANES spectroscopy. On heating BaNaRh(OH)6, a complex set of decomposition events takes place via transient phases.