Synergism of primary and secondary interactions in a crystalline hydrogen peroxide complex with tin.

Despite the significance of H2O2-metal adducts in catalysis, materials science and biotechnology, the nature of the interactions between H2O2 and metal cations remains elusive and debatable. This is primarily due to the extremely weak coordinating ability of H2O2, which poses challenges in characterizing and understanding the specific nature of these interactions. Herein, we present an approach to obtain H2O2-metal complexes that employs neat H2O2 as both solvent and ligand. SnCl4 effectively binds H2O2, forming a SnCl4(H2O2)2 complex, as confirmed by 119Sn and 17O NMR spectroscopy. Crystalline adducts, SnCl4(H2O2)2·H2O2·18-crown-6 and 2[SnCl4(H2O2)(H2O)]·18-crown-6, are isolated and characterized by X-ray diffraction, providing the complete characterization of the hydrogen bonding of H2O2 ligands including geometric parameters and energy values. DFT analysis reveals the synergy between a coordinative bond of H2O2 with metal cation and its hydrogen bonding with a second coordination sphere. This synergism of primary and secondary interactions might be a key to understanding H2O2 reactivity in biological systems.

Enhanced charge capacity and stability of Germanium(IV) Sulfide-Based anodes through Triton X100-Assisted synthesis and polysulfide shuttle mitigation.

Highly soluble germanium oxide,an amorphous macroreticular form of germanium oxide, was used as a precursor for the deposition of GeS2on reduced graphene oxide (rGO) through a low-temperature, wet-chemistry process. Thermal treatment of the solid provided an ultrathin rGO - supported amorphous GeS2coating. The GeS2@rGO composite was tested as a lithium ion battery (LIB) anode. Leveraging the versatility of wet chemistry processing, we employed strategies initially developed for mitigating polysulfide shuttle effects in lithium-sulfur batteries to enhance anode performance. The anode exhibited exceptional stability, surpassing 1000 cycles, with charge capacities exceeding 1220 and 870 mAh.g-1 at rates of 2 and 5 A.g-1, respectively. Performance improvements were achieved by minimizing GeS2 grain size using the non-ionic surfactant Triton X-100 during synthesis and preventing polysulfide shuttle effects through a negatively charged thick glass fiber separator, fluoroethylene carbonate additive (FEC) in EC:DEC (ethylene carbonate: diethyl carbonate) solvent, and a polyacrylic acid (PAA) binder. These cumulative modifications more than tripled the charge capacity of the germanium sulfide LIB anode. Feasibility was further demonstrated through full cell studies using a LiCoO2 counter electrode.

Dioxygen-halogen bonding exemplified by crystalline peroxosolvates of N,N'-bis(haloacetyl) bispidines.

The halogen bonding in molecular crystals and supramolecular assemblies has been widely investigated. Special attention is given to the molecular structures capable of simultaneously exhibiting different types of non-covalent interactions, including conventional hydrogen bonds and halogen bonds. This paper systematically analyzes crystalline peroxosolvates of bispidine-based bis-amide derivatives, containing haloacetic acid residues, namely previously reported 1,1'-(1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-iodooethanone) peroxosolvate C13H20I2N2O2·H2O2 (1) and four new crystalline compounds, 1,1'-(1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-bromoethanone) peroxosolvate C13H20Br2N2O2·H2O2 (2), 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-iodoethanone) peroxosolvate C13H20I2N2O5·0.5H2O2 (3), 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-bromoethanone) peroxosolvate C13H20Br2N2O5·H2O2 (4), and 1,1'-(9-hydroperoxy-9-hydroxy-1,5-dimethyl-3,7-diazabicyclo[3.3.1]nonane-3,7-diyl)bis(2-chloroethanone) peroxosolvate C13H20Cl2N2O5·H2O2 (5). Compounds 2-5 were synthesized for the first time and their crystal structures were determined by single-crystal X-ray diffractometry (SCXRD). To the best of our knowledge, 3-5 are unprecedented crystalline hydrogen peroxide adducts of organic hydroperoxides (R-OOH). Short intermolecular contacts between halogen and hydroperoxo oxygen atoms were found in 1-3. The halogen bonding of C-I(Br) fragments with dioxygen species in compounds 1-3 as well as in the previously reported cocrystal of diacetone diperoxide with triodotrinitrobenzene (6) was identified through reduced density gradient analysis, Hirshfeld surface analysis, and Bader analysis of crystalline electron density. The interactions were quantified using the electron density topological properties acquired from the periodic DFT calculations and evaluated to lie in the range of 9-19 kJ mol-1. A distinctive spectral feature was revealed for this type of interaction, involving a red shift of the characteristic O-O stretching vibration by about 6 cm-1, which appeared in IR spectra as a narrow low-intensity band in the region 837-872 cm-1.

Bioinspired Non-Heme Mn Catalysts for Regio- and Stereoselective Oxyfunctionalizations with H2 O2.

In recent years, metalloenzymes-mediated highly selective oxidations of organic substrates under mild conditions have been inspiration for developing synthetic bioinspired catalyst systems, capable of conducting such processes in the laboratory (and, in the future, in industry), relying on easy-to-handle and environmentally benign oxidants such as H2 O2 . To date, non-heme manganese complexes with chiral bis-amino-bis-pyridylmethyl and structurally related ligands are considered as possessing the highest synthetic potential, having demonstrated the ability to mediate a variety of chemo- and stereoselective oxidative transformations, such as epoxidations, C(sp3 )-H hydroxylations and ketonizations, oxidative desymmetrizations, kinetic resolutions, etc. Furthermore, in the past few years non-heme Mn based catalysts have become the major platform for studies focused on getting insight into the molecular mechanisms of oxidant activation and (stereo)selective oxygen transfer, testing non-traditional hydroperoxide oxidants, engineering catalytic sites with enzyme-like substrate recognition-based selectivity, exploration of catalytic regioselectivity trends in the oxidation of biologically active substrates of natural origin. This contribution summarizes the progress in manganese catalyzed C-H oxygenative transformations of organic substrates, achieved essentially in the past 5 years (late 2018-2023).

Organoantimony Dihydroperoxides: Synthesis, Crystal Structures, and Hydrogen Bonding Networks.

Despite growing interest in the potential applications of p-block hydroperoxo complexes, the chemistry of inorganic hydroperoxides remains largely unexplored. For instance, single-crystal structures of antimony hydroperoxo complexes have not been reported to date. Herein, we present the synthesis of six triaryl and trialkylantimony dihydroperoxides [Me3Sb(OOH)2, Me3Sb(OOH)2·H2O, Ph3Sb(OOH)2·0.75(C4H8O), Ph3Sb(OOH)2·2CH3OH, pTol3Sb(OOH)2, pTol3Sb(OOH)2·2(C4H8O)], obtained by the reaction of the corresponding dibromide antimony(V) complexes with an excess of highly concentrated hydrogen peroxide in the presence of ammonia. The obtained compounds were characterized by single-crystal and powder X-ray diffraction, Fourier transform infrared and Raman spectroscopies, and thermal analysis. The crystal structures of all six compounds reveal hydrogen-bonded networks formed by hydroperoxo ligands. In addition to the previously reported double hydrogen bonding, new types of hydrogen-bonded motifs formed by hydroperoxo ligands were found, including infinite hydroperoxo chains. Solid-state density functional theory calculation of Me3Sb(OOH)2 revealed reasonably strong hydrogen bonding between OOH ligands with an energy of 35 kJ/mol. Additionally, the potential application of Ph3Sb(OOH)2·0.75(C4H8O) as a two-electron oxidant for the enantioselective epoxidation of olefins was investigated in comparison with Ph3SiOOH, Ph3PbOOH, t-BuOOH, and H2O2.

Electrochemical Behavior of Reduced Graphene Oxide Supported Germanium Oxide, Germanium Nitride, and Germanium Phosphide as Lithium-Ion Battery Anodes Obtained from Highly Soluble Germanium Oxide.

Germanium and germanium-based compounds are widely used in microelectronics, optics, solar cells, and sensors. Recently, germanium and its oxides, nitrides, and phosphides have been studied as active electrode materials in lithium- and sodium-ion battery anodes. Herein, the newly introduced highly soluble germanium oxide (HSGO) was used as a versatile precursor for germanium-based functional materials. In the first stage, a germanium-dioxide-reduced graphene oxide (rGO) composite was obtained by complete precipitation of GeO2 nanoparticles on the GO from an aqueous solution of HSGO and subsequent thermal treatment in argon at low temperature. The composition of the composite, GeO2-rGO (20 to 80 wt.% of crystalline phase), was able to be accurately determined by the HSGO to GO ratio in the initial solution since complete deposition and precipitation were achieved. The chemical activity of germanium dioxide nanoparticles deposited on reduced graphene oxide was shown by conversion to rGO-supported germanium nitride and phosphide phases. The GeP-rGO and Ge3N4-rGO composites with different morphologies were prepared in this study for the first time. As a test case, composite materials with different loadings of GeO2, GeP, and Ge3N4 were evaluated as lithium-ion battery anodes. Reversible conversion-alloying was demonstrated in all cases, and for the low-germanium loading range (20 wt.%), almost theoretical charge capacity based on the germanium content was attained at 100 mA g-1 (i.e., 2595 vs. 2465 mAh g-1 for Ge3N4 and 1790 vs. 1850 mAh g-1 for GeP). The germanium oxide was less efficiently exploited due to its lower conversion reversibility.

Speciation of Tellurium(VI) in Aqueous Solutions: Identification of Trinuclear Tellurates by 17O, 123Te, and 125Te NMR Spectroscopy.

Tellurates have attracted the attention of researchers over the past decade due to their properties and as less toxic forms of tellurium derivatives. However, the speciation of Te(VI) in aqueous solutions has not been comprehensively studied. We present a study of the equilibrium speciation of tellurates in aqueous solutions at a wide pH range, 2.5-15 by 17O, 123Te, and 125Te NMR spectroscopy. The coexistence of monomeric, dimeric, and trimeric oxidotellurate species in chemical equilibrium at a wide pH range has been shown. NMR spectroscopy, DFT computations, and single-crystal X-ray diffraction studies confirmed the formation and coexistence of trimeric tellurate anions with linear and triangular structures. Two cesium tellurates, Cs2[Te4O8(OH)10] and Cs2[Te2O4(OH)6], were isolated from the solution at pH 5.5 and 9.2, respectively, and studied by single-crystal X-ray diffractometry, revealing dimeric and tetrameric tellurate anions in corresponding crystal structures.

Fast Quantum Approach for Evaluating the Energy of Non-Covalent Interactions in Molecular Crystals: The Case Study of Intermolecular H-Bonds in Crystalline Peroxosolvates.

Energy/enthalpy of intermolecular hydrogen bonds (H-bonds) in crystals have been calculated in many papers. Most of the theoretical works used non-periodic models. Their applicability for describing intermolecular H-bonds in solids is not obvious since the crystal environment can strongly change H-bond geometry and energy in comparison with non-periodic models. Periodic DFT computations provide a reasonable description of a number of relevant properties of molecular crystals. However, these methods are quite cumbersome and time-consuming compared to non-periodic calculations. Here, we present a fast quantum approach for estimating the energy/enthalpy of intermolecular H-bonds in crystals. It has been tested on a family of crystalline peroxosolvates in which the H∙∙∙O bond set fills evenly (i.e., without significant gaps) the range of H∙∙∙O distances from ~1.5 to ~2.1 Štypical for strong, moderate, and weak H-bonds. Four of these two-component crystals (peroxosolvates of macrocyclic ethers and creatine) were obtained and structurally characterized for the first time. A critical comparison of the approaches for estimating the energy of intermolecular H-bonds in organic crystals is carried out, and various sources of errors are clarified.

Triphenyllead Hydroperoxide: A 1D Coordination Peroxo Polymer, Single-Crystal-to-Single-Crystal Disproportionation to a Superoxo/Hydroxo Complex, and Application in Catalysis.

The synthesis, transformation, and application in catalysis of triphenyllead hydroperoxide, the first dioxygen lead complex, are described. Triphenyllead hydroperoxide is characterized by 207Pb nuclear magnetic resonance (NMR), Fourier transform infrared spectroscopy (FTIR), Raman spectroscopy, and single-crystal X-ray diffraction, revealing the first one-dimensional (1D) coordination peroxo polymer. Photolytic isomorphous transformation of Ph3PbOOH yields a mixed hydroxo/superoxo crystalline structure, the first nonalkali superoxo crystalline metal salt, which is stable up to 100 °C. Upon further photolysis, another isomorphous transformation of the superoxide to hydroxide is observed. These are the first single-crystal-to-single-crystal hydroperoxide-to-superoxide and then to hydroxide transformations reported to date. Photolysis of triphenyllead hydroperoxide yields two forms of superoxide-doped crystalline structures that are distinguished by widely different characteristic relaxation times. The use of Ph3PbOOH as an easy-to-handle solid two-electron oxidant for the highly enantioselective epoxidation of olefins is described.

Comparison of Proton Acceptor and Proton Donor Properties of H2O and H2O2 in Organic Crystals of Drug-like Compounds: Peroxosolvates vs. Crystallohydrates.

Two new peroxosolvates of drug-like compounds were synthesized and studied by a combination of X-ray crystallographic, Raman spectroscopic methods, and periodic DFT computations. The enthalpies of H-bonds formed by hydrogen peroxide (H2O2) as a donor and an acceptor of protons were compared with the enthalpies of analogous H-bonds formed by water (H2O) in isomorphic (isostructural) hydrates. The enthalpies of H-bonds formed by H2O2 as a proton donor turned out to be higher than the values of the corresponding H-bonds formed by H2O. In the case of H2O2 as a proton acceptor in H-bonds, the ratio appeared reversed. The neutral O∙∙∙H-O/O∙∙∙H-N bonds formed by the lone electron pair of the oxygen atom of water were the strongest H-bonds in the considered crystals. In the paper, it was found out that the low-frequency Raman spectra of isomorphous crystalline hydrate and peroxosolvate of N-(5-Nitro-2-furfurylidene)-1-aminohydantoin are similar. As for the isostructural hydrate and peroxosolvate of the salt of protonated 2-amino-nicotinic acid and maleic acid monoanion, the Raman spectra are different.

Crystalline Peroxosolvates: Nature of the Coformer, Hydrogen-Bonded Networks and Clusters, Intermolecular Interactions.

Despite the technological importance of urea perhydrate (percarbamide) and sodium percarbonate, and the growing technological attention to solid forms of peroxide, fewer than 45 peroxosolvates were known by 2000. However, recent advances in X-ray diffractometers more than tripled the number of structurally characterized peroxosolvates over the last 20 years, and even more so, allowed energetic interpretation and gleaning deeper insight into peroxosolvate stability. To date, 134 crystalline peroxosolvates have been structurally resolved providing sufficient insight to justify a first review article on the subject. In the first chapter of the review, a comprehensive analysis of the structural databases is carried out revealing the nature of the co-former in crystalline peroxosolvates. In the majority of cases, the coformers can be classified into three groups: (1) salts of inorganic and carboxylic acids; (2) amino acids, peptides, and related zwitterions; and (3) molecular compounds with a lone electron pair on nitrogen and/or oxygen atoms. The second chapter of the review is devoted to H-bonding in peroxosolvates. The database search and energy statistics revealed the importance of intermolecular hydrogen bonds (H-bonds) which play a structure-directing role in the considered crystals. H2O2 always forms two H-bonds as a proton donor, the energy of which is higher than the energy of analogous H-bonds existing in isostructural crystalline hydrates. This phenomenon is due to the higher acidity of H2O2 compared to water and the conformational mobility of H2O2. The dihedral angle H-O-O-H varies from 20 to 180° in crystalline peroxosolvates. As a result, infinite H-bonded 1D chain clusters are formed, consisting of H2O2 molecules, H2O2 and water molecules, and H2O2 and halogen anions. H2O2 can form up to four H-bonds as a proton acceptor. The third chapter of the review is devoted to energetic computations and in particular density functional theory with periodic boundary conditions. The approaches are considered in detail, allowing one to obtain the H-bond energies in crystals. DFT computations provide deeper insight into the stability of peroxosolvates and explain why percarbamide and sodium percarbonate are stable to H2O2/H2O isomorphic transformations. The review ends with a description of the main modern trends in the synthesis of crystalline peroxosolvates, in particular, the production of peroxosolvates of high-energy compounds and mixed pharmaceutical forms with antiseptic and analgesic effects.

Identification of Barium Hydroxo-Hydroperoxostannate Precursor for Low-Temperature Formation of Perovskite Barium Stannate.

A breakthrough "superoxide colloidal solution route" for low-temperature synthesis of barium and strontium stannate perovskites and their doped analogues was recently introduced. The synthesis starts from hydrogen peroxide-rich stannate solutions and yields a so-called "crystalline superoxide molecular cluster" that is converted by low temperature (<300 °C) to the respective perovskites. In this paper, the so-called "crystalline superoxide molecular cluster" is identified as a superoxide-free, barium trihydroxo(hydroperoxo)peroxostannate, BaSn(OH)3(OOH)(OO) phase (BHHPS). EPR and Raman spectroscopy studies reveal the absence of superoxide in this crystalline phase. FTIR of the deuterated sample, 119Sn NMR, and elemental analysis uncovered the empirical formula, H4O7SnBa with two peroxides per each tin element. Rietveld refinement of the XRD confirms the BHHPS cubic phase with replacement of the perovskite oxygen atoms by the OH- and OOH-ligands and peroxobridging groups.

Enhanced Thermal Buffering of Phase Change Materials by the Intramicrocapsule Sub per Mille CNT Dopant.

Microencapsulation of a carbon nanotube (CNT)-loaded paraffin phase change material, PCM in a poly(melamine-formaldehyde) shell, and the respective CNT-PCM gypsum composites is explored. Although a very low level (0.001-0.1 wt %) of intramicrocapsule loading of CNT dopant does not change the thermal conductivity of the solid, it increases the measured effusivity and thermal buffering performance during phase transition. The observed effusivity of 0.05 wt % CNT-doped PCM reaches 4000 W s-0.5 m-2 K-1, which is higher than the reported effusivity of alumina and alumina bricks and an order of magnitude larger than the solid, CNT-free PCM powder. The CNT dopant (0.015 wt %) in a 30 wt % PCM-plaster composite improved the effusivity by 60% compared to the CNT-free composite, whereas the addition of the same amount of CNTs to the bulk of the plaster does not improve either the effusivity or the thermal buffering performance of the composite. The thermal enhancement is ascribed to a CNT network formation within the paraffin core.

Crystalline Ammonium Peroxogermanate as a Waste-Free, Fully Recyclable Versatile Precursor for Germanium Compounds.

High, nearly 100%, yield synthesis of ammonium peroxogermanate (APG), (NH4)6[Ge6(µ-OO)6(µ-O)6(OH)6]·6H2O, is presented, and its crystal structure is determined by single crystal X-ray study. It comprises centrosymmetric hexanuclear peroxogermanate anions [Ge6(µ-OO)6(µ-O)6(OH)6]6- with six µ-oxo- and six µ-peroxo groups forming negatively charged layers. The space between these layers is filled by ammonium cations and water molecules, forming a highly stable structure due to hydrogen bonding. Highly soluble macroporous amorphous germanium oxide (HSGO) is then synthesized by mild treatment of APG. The compound forms highly oversaturated metastable germanium oxide solution with a solubility of 100 g/L, over 20 times higher than the solubility of amorphous germanium oxide. HSGO solution is a versatile reagent that can react with basic and acidic reagents to give a diverse range of salts including, e.g., germanium sulfide, germanium hydrophosphate, and potassium germanate. In the absence of acid or base, the aqueous HSGO solution yields hexagonal germanium oxide under ambient conditions.

Vanadium Oxide Thin Film Formation on Graphene Oxide by Microexplosive Decomposition of Ammonium Peroxovanadate and Its Application as a Sodium Ion Battery Anode.

Formation of vanadium oxide nanofilm-coated graphene oxide (GO) is achieved by thermally induced explosive disintegration of a microcrystalline ammonium peroxovanadate-GO composite. GO sheets isolate the microcrystalline grains and capture and contain the microexplosion products, resulting in the deposition of the nanoscale products on the GO. Thermal treatment of the supported nanofilm yields a sequence of nanocrystalline phases of vanadium oxide (V3O7, VO2) as a function of temperature. This is the first demonstration of microexplosive disintegration of a crystalline peroxo compound to yield a nanocoating. The large number of recently reported peroxide-rich crystalline materials suggests that the process can be a useful general route for nanofilm formation. The V3O7@GO composite product was tested as a sodium ion battery anode and showed high charge capacity at high rate charge-discharge cycling (150 mAh g-1 at 3000 mA g-1 vs 300 mAh g-1 at 100 mA g-1) due to the nanomorphology of the vanadium oxide.

Synthesis of high volumetric capacity graphene oxide-supported tellurantimony Na- and Li-ion battery anodes by hydrogen peroxide sol gel processing.

High-charge-capacity sodium-ion battery anodes made of Sb2Te3@reduced graphene oxide are reported for the first time. Uniform nano-coating of graphene oxide is carried out from common sol of peroxotellurate and peroxoantimonate under room temperature processing. Reduction by hydrazine under glycerol reflux yields Sb2Te3@reduced graphene oxide. The electrodes exhibit exceptionally high volumetric charge capacity, above 2300mAhcm-3 at 100mAg-1 current density, showing very good rate capabilities and retaining 60% of this capacity even at 2000mAg-1. A comparison of sodiation and lithiation shows that lithiation exhibits better volumetric charge capacity, but surprisingly only marginally better relative rate capability retention at 2000mAg-1. Tellurium-based electrodes are attractive due to the high volumetric charge capacity of Te, its very high electric conductivity, and the low relative expansion upon lithiation/sodiation.

H2O2 induced formation of graded composition sodium-doped tin dioxide and template-free synthesis of yolk-shell SnO2 particles and their sensing application.

Sodium peroxostannate nanoparticles with graded composition were produced from aqueous hydrogen peroxide-sodium hydroxostannate solution. The uniform particles were converted to composition graded sodium stannate by mild thermal treatment for peroxide decomposition and yielded yolk-shell tin dioxide particles by dilute acid treatment. The mechanism of formation of the graded sodium concentration is explained in view of the solubility of peroxostannate in H2O2-H2O solution and based on 119Sn NMR, XRD, dynamic light scattering (DLS) and electron microscopy studies. Initial studies illuminating sensitive hydrogen sensing by yolk-shell tin oxide particles are presented.

Crystal structure of (Z)-N-benzyl-idene-1-phenyl-methanamine oxide hydrogen peroxide monosolvate.

The title adduct, C14H13NO·H2O2, consists of (Z)-N-benzyl-idene-1-phenyl-methanamine oxide and hydrogen peroxide mol-ecules in a 1:1 ratio. The organic coformer adopts a skew geometry with an inter-aryl-ring dihedral angle of 81.9 (2)°. In the crystal, the organic and peroxide mol-ecules are linked through both peroxide O-H donor groups to oxide O-atom acceptors, giving one-dimensional chains extending along the b axis. Present also are weak inter-molecular C-H⋯O hydrogen-bonding inter-actions.

Hydrogen Peroxide Insular Dodecameric and Pentameric Clusters in Peroxosolvate Structures.

Peroxosolvates of 2-aminonicotinic acid (I) and lidocaine N-oxide (II) including the largest insular hydrogen peroxide clusters were isolated and their crystal structures were determined by single-crystal X-ray diffraction. An unprecedented dodecameric hydrogen peroxide insular cluster was found in I. An unusual cross-like pentameric cluster was observed in the structure of II. The topology of the (H2 O2 )12 assembly was never observed for small-molecule clusters. In I and II new double and triple cross-orientational disorders of H2 O2 were found. Cluster II is the first example of a peroxosolvate crystal structure containing H2 O2 molecules with a homoleptic hydrogen peroxide environment. In II, a hydrogen bond between an H2 O2 molecule and a peptide group -CONH⋅⋅⋅O2 H2 was observed for the first time.

Nanocrystalline SnS2 coated onto reduced graphene oxide: demonstrating the feasibility of a non-graphitic anode with sulfide chemistry for potassium-ion batteries.

An anode material incorporating a sulfide is reported. SnS2 nanoparticles anchored onto reduced graphene oxide are produced via a chemical route and demonstrate an impressive capacity of 350 mA h g-1, exceeding the capacity of graphite. These results open the door for a new class of high capacity anode materials (based on sulfide chemistry) for potassium-ion batteries.