Diagnostic Protocols for Evaluating the Degradation Mechanisms in Gel-Polymer Lithium Batteries.

Gel polymer electrolytes (GPEs) present a promising alternative to standard liquid electrolytes (LE) for Lithium-ion Batteries (LIBs) and Lithium Metal Batteries bridging the advantages of both liquid and solid polymer electrolytes. However, their cycle life still lags behind that of standard LIBs, and their degradation mechanisms remain poorly understood. A significant challenge is the need for specific diagnostic protocols to systematically study the degradation mechanisms of GPE-based cells. Challenges include the separation of cell components and effective washing, as well as the study of the solid electrolyte interfaces, all complicated by the semi-solid nature of GPEs. This paper provides a brief review of existing literature and proposes a comprehensive set of diagnostic tools for dismantling and evaluating the degradation of GPE-based LIBs. Finally, these methods and recommendations are applied to LiNi0.5Mn1.5O4 (LNMO)-graphite cells, revealing electrolyte oxidation as a major source of cell degradation.

Beam Effects in Synchrotron Radiation Operando Characterization of Battery Materials: X-Ray Diffraction and Absorption Study of LiNi0.33Mn0.33Co0.33O2 and LiFePO4 Electrodes.

Operando synchrotron radiation-based techniques are a precious tool in battery research, as they enable the detection of metastable intermediates and ensure characterization under realistic cycling conditions. However, they do not come exempt of risks. The interaction between synchrotron radiation and samples, particularly within an active electrochemical cell, can induce relevant effects at the irradiated spot, potentially jeopardizing the experiment's reliability and biasing data interpretation. With the aim of contributing to this ongoing debate, a systematic investigation into these phenomena was carried out by conducting a root cause analysis of beam-induced effects during the operando characterization of two of the most commonly employed positive electrode materials in commercial Li-ion batteries: LiNi0.33Mn0.33Co0.33O2 and LiFePO4. The study spans across diverse experimental conditions involving different cell types and absorption and scattering techniques and seeks to correlate beam effects with factors such as radiation energy, photon flux, exposure time, and other parameters associated with radiation dosage. Finally, it provides a comprehensive set of guidelines and recommendations for assessing and mitigating beam-induced effects that may affect the outcome of battery operando experiments.

Chromium Speciation in Zirconium-Based Metal-Organic Frameworks for Environmental Remediation.

Acute CrVI water pollution due to anthropogenic activities is an increasing worldwide concern. The high toxicity and mobility of CrVI makes it necessary to develop dual adsorbent/ion-reductive materials that are able to capture CrVI and transform it efficiently into the less hazardous CrIII . An accurate description of chromium speciation at the adsorbent/ion-reductive matrix is key to assessing whether CrVI is completely reduced to CrIII , or if its incomplete transformation has led to the stabilization of highly reactive, transient CrV species within the material. With this goal in mind, a dual ultraviolet-visible and electron paramagnetic spectroscopy approach has been applied to determine the chromium speciation within zirconium-based metal-organic frameworks (MOFs). Our findings point out that the generation of defects at Zr-MOFs boosts CrVI adsorption, whilst the presence of reductive groups on the organic linkers play a key role in stabilizing it as isolated and/or clustered CrIII ions.

Exploring new hydrated delta type vanadium oxides for lithium intercalation.

Three hydrated double layered vanadium oxides, namely Na0.35V2O5·0.8(H2O), K0.36(H3O)0.15V2O5 and (NH4)0.37V2O5·0.15(H2O), were obtained by using mild hydrothermal conditions. Their delta type structural frameworks were solved by high-resolution synchrotron X-ray powder diffraction and the interlayer spacings were interpreted from difference Fourier maps. The inter-slab distances are modulated by the water content and the special arrangements of the alkali and ammonium cations. The XPS measurements denote mixed valence systems with high contents of V4+ ions up to 40%. The monitoring of the V4+ EPR signal over time suggests a reduction of the electronic delocalization on account of the partial oxidation to V5+. The electrochemical performance of the active phases is strongly conditioned by the vacuum-drying process of the electrodes, showing better capacity retention when vacuum is not applied. In situ X-ray diffraction shows a structural mechanism of contraction/expansion of the bilayers upon lithium insertion/extraction where the alkali ions behave as structural stabilizers. Galvanostatic cycling at very low current density implies migration of the alkali "pillars" triggering the collapse of the structure.

Thermal activation of charge carriers in ionic and electronic semiconductor ß-AgIVVO3 and ß-AgIVVO3@VV 1.6VIV 0.4O4.8 composite xerogels.

Silver vanadium oxide (SVO) and Silver Vanadium Oxide/Vanadium Oxide (SVO@VO) composite hydrogels are formed from the self-entanglement of ß-AgVO3 nanoribbons and slightly reduced vanadium oxide (VO) (VV 1.6VIV 0.4O4.8) nanoribbons; respectively. Starting from randomly distributed nanoribbons within hydrogels, and after a controlled drying process, a homogeneous xerogel system containing tuneable SVO : VO ratios from 1 : 0 to 1 : 1 can be obtained. The precise nanoribbons compositional control of these composite system can serve as a tool to tune the electrical properties of the xerogels, as it has been demonstrated in this work by impedance spectroscopy (IS) experiments. Indeed, depending on the composition and temperature conditions, composite xerogels can behave as electronic, protonic or high temperature ionic conductors. In addition, the electric and protonic conductivity of the composite xerogels can be enhanced (until a critical irreversible point), through the temperature triggered charge carrier creation. As concluded from thermogravimetry, IR, UV-Vis and EPR spectroscopy studies, besides the SVO : VO ratio, the thermal induced oxidation/reduction of V5+ to V4+, and thermally triggered release of strongly bonded water molecules at the nanoribbon surface are the two key variables that control the electric and ionic conduction processes within the SVO and composite SVO/VO xerogels.

Open and closed forms of the interpenetrated [Cu2(Tae)(Bpa)2](NO3)2·nH2O: magnetic properties and high pressure CO2/CH4 gas sorption.

Two closed and one open structural forms of the interpenetrated [Cu2(Tae)(Bpa)2](NO3)2·nH2O (H2Tae = 1,1,2,2-tetraacetylethane, Bpa = 1,2-bis(4-pyridyl)ethane) cationic coordination polymer have been synthesized. Three crystallographically related interpenetrated "ths" cationic nets encapsulate water molecules and nitrate anions giving rise to the closed structural forms of [Cu2(Tae)(Bpa)2](NO3)2·nH2O. Depending on the location of water molecules and nitrate groups, two different closed forms with 5.5 and 3.6 crystallization water molecules have been obtained. The thermal activation of the closed structures gives rise to a 29% expansion of the unit cell. This closed to open transformation is reversible, and is triggered by the loss or uptake of solvent. The high pressure gas adsorption experiments show similar selectivity values towards CO2 for CO2/CH4 mixtures to that showed by some metal organic frameworks without unsaturated metal sites, and isosteric heats for CO2 adsorption similar to that for the HKUST-1 compound.

Commensurate Superstructure of the {Cu(NO3)(H2O)}(HTae)(Bpy) Coordination Polymer: An Example of 2D Hydrogen-Bonding Networks as Magnetic Exchange Pathway.

The average and commensurate superstructures of the one-dimensional coordination polymer {Cu(NO3)(H2O)}(HTae)(Bpy) (H2Tae = 1,1,2,2-tetraacetylethane, Bpy = 4,4'-bipyridine) were determined by single-crystal X-ray diffraction, and the possible symmetry relations between the space group of the average structure and the superstructure were checked. The crystal structure consists in parallel and oblique {Cu(HTae)(Bpy)} zigzag metal-organic chains stacked along the [100] crystallographic direction. The origin of the fivefold c axis in the commensurate superstructure is ascribed to a commensurate modulation of the coordination environment of the copper atoms. The commensurately ordered nitrate groups and coordinated water molecules establish a two-dimensional hydrogen-bonding network. Moreover, the crystal structure shows a commensurate to incommensurate transition at room temperature. The release of the coordination water molecules destabilizes the crystal framework, and the compound shows an irreversible structure transformation above 100 °C. Despite the loss of crystallinity, the spectroscopic studies indicate that the main building blocks of the crystal framework are retained after the transformation. The hydrogen-bonding network not only plays a crucial role stabilizing the crystal structure but also is an important pathway for magnetic exchange transmission. In fact, the magnetic susceptibility curves indicate that after the loss of coordinated water molecules, and hence the collapse of the hydrogen-bonding network, the weak anti-ferromagnetic coupling observed in the initial compound is broken. The electron paramagnetic resonance spectra are the consequence of the average signals from Cu(II) with different orientations, indicating that the magnetic coupling is effective between them. In fact, X- and Q-band data are reflecting different situations; the X-band spectra show the characteristics of an exchange g-tensor, while the Q-band signals are coming from both the exchange and the molecular g-tensors.

Ax(H3O)2-xMn5(HPO3)6 (A = Li, Na, K and NH4): open-framework manganese(ii) phosphites templated by mixed cationic species.

Ax(H3O)2-xMn5(HPO3)6 (A = Li, x = 0.55 (1-Li); A = Na, x = 0.72 (2-Na); A = K, x = 0.30 (3-K); A = NH4, x = 0.59 (4-NH4)) phases were synthesized by employing mild hydrothermal conditions. 1-Li was studied by single crystal X-ray diffraction, while sodium, potassium and ammonium containing analogues were obtained as polycrystalline samples and characterized by powder X-ray diffraction. The four compounds were characterized by ICP-Q-MS, thermal analysis and XPS, IR, UV/Vis and EPR spectroscopy. Single crystal data indicate that 1-Li crystallizes in the P3[combining macron]c1 space group with lattice parameters a = 10.3764(1) Å and c = 9.4017(1) Å with Z = 2. The crystal structure of these phases is constituted by a three-dimensional [Mn(ii)5(HPO3)6](2-) anionic skeleton templated by alkali metal and ammonium cations together with protonated water molecules. Such an inorganic framework is formed by layers of edge-sharing MnO6 octahedra placed in the ab plane and joined along the c direction through phosphite pseudotetrahedra. The sheets display 12-membered ring channels parallel to the c-axis, ca. 5 Å in diameter, where the extraframework species display a strong disorder. EPR measurements point to the existence of short range ferromagnetic interactions around 12 K. Magnetic susceptibility and heat capacity measurements show that all the compounds exhibit long range antiferromagnetic order below circa 4 K, with a significant magnetocaloric effect around the Neel temperature.

Low temperature red luminescence of a fluorinated Mn-doped zinc selenite.

M2(SeO3)F2 (M = Zn (1), Mn (2)) stoichiometric phases together with the Zn2-xMnx(SeO3)F2 compound doped at various concentrations (x = 0.002-0.2) were synthesized by employing mild hydrothermal conditions. These compounds have been characterized by scanning electron microscopy (SEM), Rietveld refinement of the X-ray powder diffraction patterns, ICP-Q-MS, thermogravimetric and thermodiffractometric analyses, and IR, UV/vis and electron paramagnetic resonance (EPR) spectroscopies. Compounds 1 and 2 crystallize in the orthorhombic Pnma space group with lattice parameters: a = 7.27903(4), b = 10.05232(6) and c = 5.26954(3) Šfor the zinc species and a = 7.50848(9), b = 10.3501(12) and c = 5.47697(6) Šfor the manganese phase, with Z = 4. The crystal structures of these compounds are isotypic and are built up from a 3D framework constructed by (010) sheets of [MO3F3] octahedra linked up by [SeO3] building units. Luminescence measurements of Mn2(SeO3)F2 were performed at different temperatures between 10 and 150 K. At 10 K, the emission spectrum consists of a broad band peaked at around 660 nm related to the (4)T1g→(6)A1g transition in octahedrically coordinated Mn(2+). Moreover, the influence of temperatures up to 295 K and the Mn concentration on the luminescent properties of the Zn2-xMnx(SeO3)F2 system were systematically studied. Magnetic measurements of 2 show antiferromagnetic coupling as the major interactions exhibiting a spin canting at low temperature.

Amine templated open-framework vanadium(III) phosphites with catalytic properties.

Four novel amine templated open-framework vanadium(III) phosphites with the formula (C(5)N(2)H(14))(0.5)[V(H(2)O)(HPO(3))(2)], 1 (C(5)N(2)H(14) = 2-methylpiperazinium), and (L)(4-x)(H(3)O)(x)[V(9)(H(2)O)(6)(HPO(3))(14-y)(HPO(4))(y)(H(2)PO(3))(3-z)(H(2)PO(4))z]·nH(2)O (2, L = cyclopentylammonium, x = 0, y = 3.5, z = 3, n = 0; , L = cyclohexylammonium, x = 1, y = 0, z = 0.6, n = 2.33; , L = cycloheptylammonium, x = 1, y = 0, z = 0, n = 2.33) were synthesized employing solvothermal reactions and characterized by single-crystal X-ray diffraction, ICP-AES and elemental analyses, thermogravimetric and thermodiffractometric analyses, and IR and UV/vis spectroscopy. Single-crystal data indicate that 1 crystallizes in the triclinic system, space group P1, whereas 2, 3 and 4 crystallize in the hexagonal space group P6(3)/m. Compound 1 has a two-dimensional motif with anionic sheets of [V(H(2)O)(HPO(3))(2)](-) formula, whose charge is compensated by the 2-methylpiperazinium cations embedded between the layers. In contrast, 2, 3 and 4 present a pillar-layer network giving rise to a three-dimensional framework containing intersecting 16-ring channels with the primary amine templates and the crystallization water molecules enclosed in them. 1, 2, 3 and 4 behave as heterogeneous catalysts for the selective oxidation of alkyl aryl sulfides, with tert-butylhydroperoxide (TBHP) as the oxidizing agent, being active, selective and recyclable for several successive cycles of reaction.

Enhancement of the luminescent properties of a new red-emitting phosphor, Mn2(HPO3)F2, by Zn substitution.

The Mn(2)(HPO(3))F(2) phase has been synthesized as single crystals by using mild hydrothermal conditions. The compound crystallizes in the orthorhombic Pnma space group, with unit cell parameters of a = 7.5607(8), b = 10.2342(7), and c = 5.5156(4) Å, with Z = 4. The crystal structure consists of a three-dimensional framework formed by alternating (010) layers of [MnO(3)F(3)] octahedra linked up by three connected [HPO(3)] tetrahedra. Luminescence measurements were performed at different temperatures between 10 and 150 K. The 10 K emission spectrum of the octahedrally coordinated Mn(II) cation exhibits a broad band centered at around 615 nm corresponding to the (4)T(1) → (6)A(1) transition. In order to explore the effect of the Mn(II) concentration and the possibility of enhancing the luminescence properties of the Mn(II) cation in Mn(2)(HPO(3))F(2), different intermediate composition members of the finite solid solution with the general formula (Mn(x)Zn(1-x))(2)(HPO(3))F(2) were prepared and their luminescent properties studied. The magnetic and specific heat behavior of M(2)(HPO(3))F(2) (M = Mn, Fe) have also been investigated. The compounds exhibit a global antiferromagnetic ordering with a spin canting phenomenon detected at approximately 30 K. The specific heat measurements show sharp λ-type peaks at 29.7 and 33.5 K for manganese and iron compounds, respectively. The total magnetic entropy is consistent with spin S = 5/2 and S = 2 of Mn(II) and Fe(II) cations.