Electrochemical cells based on the intercalation and deintercalation of chalcogen anions.

Abstract

This application is filed in accordance with the 2 O 2 S 2 The present invention relates to electroactive materials suitable for electrochemical cell electrodes, comprising chalcogen oligomers capable of reversibly deintercalating / reintercalating anions of chalcogen, such as, and electrochemical electrodes and cells containing said materials.

Description

[Technical Field]

[0001] The present invention relates to electrochemistry, and in particular to solid-state ion batteries. [Background technology]

[0002] In view of global warming and scarcity of natural resources, the production and storage of renewable energy is of great importance and one of the great challenges for the scientific community.

[0003] Electrical devices and transportation are currently based on lithium batteries, but lithium resources are limited, so researchers are already looking into alternatives, for example, using sodium.

[0004] In these batteries, alkali metal cations (Li + , Na + ) ensures conduction within the electrolyte. + ions) are exchanged between two active materials on the positive and negative electrodes, which are capable of intercalating and deintercalating lithium, at least in the positive electrode.

[0005] More recently, Li-ion batteries using elemental sulfur as the cathode have been considered (Manthiram et al., Chem. Rev. 2014, 114, 11751-11787). However, in such lithium-sulfur batteries, the conductive ionic species that migrate between the sulfur cathode and the lithium anode is still the lithium cation (Li + )

[0006] Alternative ionic species have also been investigated as conductive species in electrochemical cells, for example, zinc-ion batteries containing zinc at the anode and manganese oxide at the cathode. Although these electrochemical systems have been extensively studied, their benefits are still in question. After years of research, only recently have stable charge / discharge cycles been achieved for batteries using aluminum ions as the intercalating species. Magnesium-ion batteries have been successfully realized. Nevertheless, the use of alternative cations continues to be a challenge.

[0007] There has been substantially less research into batteries based on the intercalation or deintercalation of anions. Most studies have focused on the transfer of O from an air cathode to a metal anode during discharge. 2- The focus is on metal ions, with organic anions also being considered (PF6 - , BF4 - Alternative anion batteries use fluorides, chlorides, and metal halides, such as BiF3 and BiCl3, as the cathode and a reactive metal, such as lithium, as the anode, allowing halide anions to migrate from the cathode to the anode.

[0008] However, lithium sources are limited, necessitating consideration of alternative materials. [Prior art documents] [Non-patent literature]

[0009] [Non-Patent Document 1] Manthiram et al., chem.Rev.2014, 114, 11751~11787 Summary of the Invention [Problem to be solved by the invention]

[0010] It is therefore an object of the present invention to provide alternative electroactive materials that rely on naturally abundant elements such as chalcogens. [Means for solving the problem]

[0011] The present inventors have discovered that it is possible to deintercalate and reintercalate chalcogens / chalcogenides, such as sulfur, from materials containing chalcogen oligomers, such as sulfur couples, at moderate temperatures (below 300° C.).

[0012] This phenomenon has been shown to be reversible. This discovery allows for the consideration of using such chalcogen materials to provide, for example, sulfur-sulfur chalcogen-chalcogen batteries. Such batteries involve an active material containing a chalcogen oligomer, such as a chalcogen pair, and the exchange of chalcogen anions between the cathode and anode.

[0013] Thus, according to a first object, the present invention relates to an electroactive material for an electrochemical cell electrode comprising a chalcogen oligomer, characterized in that said material is capable of reversibly deintercalating anions of said chalcogen by reduction and reintercalating said anions by oxidation while maintaining its overall structure.

[0014] As used herein, the term "electroactive material" refers to a material that can be used as an electrode material and that is capable of undergoing an oxidation-reduction reaction.

[0015] Chalcogens are chemical elements in group 16 of the periodic table. This group specifically includes the following elements: oxygen (O), sulfur (S), selenium (Se), and tellurium (Te). Typically, the chalcogen is sulfur.

[0016] The term "oligomer" refers to a neutral or charged species containing chalcogen atoms chemically linked to each other through strong chemical bonds. Typically, these blocks consist of several identical chalcogen atoms, typically 2 to 6, with charges that can range from 1 to 2. Thus, chalcogen oligomers are typically called Q n where Q represents a chalcogen atom and n represents an integer from 2 to 6. Typically, the chalcogen oligomer is a sulfur pair (SS).

[0017] Typically, the material comprising chalcogen oligomers may be selected from among La2O2S2, SrS2, SrS3, BaS2, BaS3, Ba2S2F2, FeS2, NiS2, CoS2, MnS2, TiS3, VS4, PbS2, BiS2, but any compound with an arrangement of at least two chalcogen atoms may be useful.

[0018] According to the present invention, the material comprises a chalcogen oligomer that can be reduced to form a chalcogen anion or a chalcogen oligomer anion as follows: (Q n ) 2- +(2n-2)e - →nQ 2-

[0019] When the chalcogen is sulfur, the following reductive cleavage can occur: (S2) 2- +2e - →2S 2- or (S3) 2- +4e - →3S 2-

[0020] As an example, the La2O2S2 structure has isolated (S2) molecules aligned parallel to these 2D blocks. 2- Fluorite-type structures separated from each other by sulfur dimers 2 / ∞ [La2O2)] 2+It is composed of infinite layers. The removal of one sulfur atom per dimer, i.e., deintercalation, leads to the La2O2S compound, whose structure is inherited from the stacked structure of the precursor La2O2S2. This novel phase crystallizes in the Amm2 space group and is a new polymorph of the well-known hexagonal La2O2S (hp-La2O2S(P-3m1)). In the following, the term oA-La2O2S will be used for this specific orthorhombic morphology in contrast to the well-known hexagonal form.

[0021] Therefore, La2O2S2 is [ka] According to the reaction S 2- reversibly deintercalating and reintercalating oA represents the central cuboidal crystal form.

[0022] oA-La2O2S has never been synthesized or characterized before.

[0023] According to another object, the present invention thus provides a method for producing a method for manufacturing a semiconductor device comprising: Formula (I): oA-La2O2S (I) In the material It also relates to materials in which oA represents a central cuboid morphology.

[0024] Similarly, La2O2S2 is [ka] According to the reaction - It also reversibly deintercalates and reintercalates.

[0025] oA-La2O2S 1.5 (Amm2 space group) has never been synthesized or characterized before.

[0026] According to another object, the present invention thus provides a method for producing a method for manufacturing a semiconductor device comprising: Formula (II): oA-La2O2S 1.5 (II) In the material It also relates to materials in which oA represents a central cuboid morphology.

[0027] According to one embodiment, oA-La2O2S(I) can be prepared by a method comprising mixing La2O2S2 and Rb and heating the mixture. Typically, the reaction can be carried out in a sealed quartz tube, preferably in a 1:2 molar ratio. Typically, the heating temperature is between 200 and 350°C, depending on the application or adaptation of the procedures discussed in detail in the Examples.

[0028] According to one embodiment, oA-La4O4S3(II) can be prepared in a similar manner. In a variant, it can also be prepared by intercalation of sulfur anions into oA-La2O2S, i.e., by a method comprising mixing oA-La2O2S with S flakes and heating the mixture. Typically, before the heating step, the mixture can be pelletized and sealed in an evacuated quartz tube. Typically, the heating temperature is 150-200°C.

[0029] The materials of formula (I) and (II) may be characterized by their X-ray and electron diffraction spectra, as illustrated in the accompanying figures.

[0030] As used herein, deintercalation refers to the removal of atoms or ions from the host lattice in which they were present, while reintercalation refers to their reversible reinclusion (or reinsertion) within the lattice without modifying the overall crystal structure of the host material, i.e., its lamellar structure.

[0031] According to the present invention, at the positive electrode, chalcogen (or chalcogenide) anions (typically S 2- ) deintercalates from the electrode material during discharge (reduction) and reintercalates into said material during charge (oxidation).

[0032] According to one embodiment, the chalcogen anion has formula (III): (S n ) X- (III) or an oligomer thereof, wherein n and x are integers such that x is equal to 1 or 2 and n is 1 to 6.

[0033] Typically, n is 1 and x is 2 and the chalcogen anion is S 2- It is as follows.

[0034] According to one embodiment, the electrochemical cell electrode is a positive electrode, which herein means the electrode of the electrochemical cell, referred to as the element, into which chalcogen ions leave and electrons enter upon discharge.

[0035] "Positive electrode" refers to an electrode that functions as a cathode during discharge and an anode during charge, the anode being defined as the electrode where the electrochemical oxidation reaction (release of electrons) occurs, while the cathode is the reduction site.

[0036] According to another object, the present invention also relates to a positive electrode comprising the electroactive material of the present invention.

[0037] According to one embodiment, the positive electrode may include a current collector and a coating layer, the coating layer including the electroactive material.

[0038] The positive electrode generally consists of an electroactive material and a conductive medium used as a current collector that is typically coated with a mixture including solid electrolyte particles, conductive additives, and a binder.

[0039] The term "current collector" is understood to mean an element such as a pad, plate, foil, sheet, mesh, fabric, etc., made of an electrically conductive material and connected to the positive or negative electrode, which ensures the conduction of the flow of electrons between the terminals and the electrodes of the battery.

[0040] Typically, the current collector is composed of a metal or alloy selected from the group consisting of aluminum, copper, nickel, carbon, stainless steel and alloys thereof.

[0041] According to one embodiment, the current collector is an aluminum sheet.

[0042] According to another object, the present invention provides a method for producing a method for manufacturing a semiconductor device comprising: - a positive electrode as defined above; - negative electrode; an electrolyte layer sandwiched between a positive electrode and a negative electrode; The present invention also relates to an electrochemical cell comprising the above-mentioned compound, characterized in that the electrolyte is a solid electrolyte comprising, as conductive ions, chalcogen anions of the chalcogen oligomer of the electroactive material.

[0043] The term "negative electrode" refers to an electrode that functions as an anode during discharge and a cathode during charge, the anode being defined as the electrode where the electrochemical oxidation reaction (release of electrons) occurs, while the cathode is the reduction site.

[0044] Typically, the term negative electrode refers to the electrode from which electrons leave and on which chalcogen anions collect during discharge.

[0045] "Electrochemical cell" means a basic electrochemical cell consisting of a positive electrode / electrolyte / negative electrode assembly that allows electrical energy provided by a chemical reaction to be stored and returned in the form of an electric current.

[0046] According to one embodiment, the electrochemical cell is a solid state cell.

[0047] In an all-solid-state element, the electrolyte compound may be contained within the solid electrolyte layer, but may also be partially contained within the electrodes.

[0048] According to another object, the invention relates to a battery comprising a plurality of electrochemical cells as defined above, the cells being electrically connected.

[0049] "Battery" or accumulator means an assembly of multiple cells according to the present invention. [Brief explanation of the drawings]

[0050] [Figure 1] 1 illustrates the principle of a sulfur-sulfur battery according to the present invention, involving sulfur as the chalcogen and La2O2S2 as the electroactive material. [Figure 2] (a) The structure of La2O2S2 reported by Ostorero et al. (SG:Cmca) (Acta Cryst. C46, ​​1376-1378 (1990)); (b) Schematic of the S-S bond cleavage under the donation of one electron per elemental metal MO, which subsequently leads to the deintercalation of the half-sulfur atom of the S2 dumbbell, which is thought to enable the topochemical transformation of La2O2S2 into a new polymorph called La2O2S; (c) Illustrates the two low-energy, dynamically stable phases of oA-La2O2S predicted by USPEX. [Figure 3](a) Partial intercalation of sulfur into oA-La2O2S and deintercalation of sulfur from La2O2S2 leading to the intermediate compound oA-La2O2S1.5; (b) Sulfur intercalation experiments into oA-La2O2S. Experimental XRD patterns of pure oA-La2O2S and the products of its mixture with sulfur (0.5 or 1 equivalent of S) after heat treatment at 150 or 200 °C. New XRD peaks appearing after heat treatment at 0.5 S are marked by *; (c) Sulfur deintercalation from La2O2S2. Experimental XRD patterns of La2O2S2 and the products of its mixture with Rb0, Ag0, and Ni0 after heat treatment at 200 or 350 °C. XRD peaks assigned to by-products are marked as follows: ● = Ag2S (Fur Krist.- Cryst. Mater. 110, 136-144 (1958)); ■ = α-NiS (J. Trahan, RG Goodrich, S.F. Watkins, Phys. Rev. B2, 2859-2863 (1970)). [Figure 4] We present an overview of low-temperature sulfur-rich topochemistry in the La-OS system. The topochemical intercalation and deintercalation of sulfur in the oxychalcogenide compound La2O2S2 leads to the formation of two new metastable compounds. [Figure 5] (A) EDX spectrum and (B) backscattered electron image (BEI) of an oA-La2O2S powder sample impregnated with epoxy resin and its elemental composition mapped for La and S. DETAILED DESCRIPTION OF THE INVENTION

[0051] In FIG. 1, a cell of such a sulfur-sulfur battery is shown diagrammatically in a discharging state.

[0052] The cell comprises a positive electrode 1 (cathode) and a negative electrode 2 (anode). A sulfur anion conducting electrolyte 3 is sandwiched between electrodes 1 and 2.

[0053] Both electrodes 1 and 2 are electrically connected together using an electrical circuit that includes an ammeter 9 .

[0054] As depicted in Figure 1: The positive electrode 1 includes a current collector 4 and an electroactive material layer 5. Layer 5 is at the interface between a conductive electrolyte 3 and the inner surface of the current collector 4. Typically, the current collector 4 can be an aluminum sheet.

[0055] The negative electrode 2 includes a current collector 6 and a layer 7 at the interface between the conductive electrolyte 3 and the inner surface of the current collector 6 .

[0056] Typically, the negative electrode current collector 6 is made of copper.

[0057] Layer 7 is a sulfur composite, or wM+S 2- →M w S+2e - It may be composed of a metal M capable of reacting with sulfur anions according to the following reaction: It may also be composed of another material capable of intercalating and deintercalating sulfur anions.

[0058] During discharge, the positive electrode 1, for example in the case of La2O2S2: [ka] As such, it attracts electrons from the electrical circuit, thus allowing reductive cleavage to occur.

[0059] S 2- The anions migrate through the electrolyte 8 from the positive electrode 1 to the negative electrode 2, where they are collected and oxidized, releasing electrons: S 2- →S 0 +2e - or wM+S 2- →M w S+2e -

[0060] The resulting electrons then travel back through the electrical circuit 9 to the positive electrode 1 .

[0061] Although not shown in FIG. 1, the opposite reaction occurs during charging, where the positive electrode becomes the anode (oxidation site) and the negative electrode becomes the cathode (reduction site).

[0062] The following examples are provided for illustrative purposes only. [Example]

[0063] La2O2S2 was used as a precursor to test the topochemical reduction of chalcogenides (Figure 2a). The structure shows the isolated (S2) structure aligned parallel to these 2D blocks. 2- Fluorite-type structures separated from each other by sulfur dimers 2 / ∞ [La2O2] 2+ The dimer consists of infinite layers. The removal of one sulfur atom per dimer should a priori lead to the La2O2S compound (Figure 2b), whose structure should be inherited from the stacked structure of the precursor La2O2S2. We first investigated the low-energy structure of the La2O2S compound using the Crystal Structure Prediction (CSP) methodology. The USPEX evolutionary structure search algorithm, combined with first-principles calculations, allowed us to locate two polymorphs: the hP and oA crystal structures, which are stable and metastable, respectively (see Figure 2c). Both phases are dynamically stable, validating their respective locations in the global and local minima on the potential energy surface of La2O2S. The most stable candidate is the La2O2S compound, with sulfur atoms alternating within the octahedral environment of lanthanum. 2 / ∞[La2O2] shows a hexagonal stacked structure with fluorite-type (111) slabs. Interestingly, this is exactly the structure of the La2O2S compound, generally prepared at high temperatures (800-1200 °C), reported in the literature (Acta Cryst. B29, 2647-2648 (1973)). In the following, this structure will be denoted as hP-La2O2S according to Pearson notation (h stands for hexagonal and P stands for simple cell). USPEX also predicted the structure of an unknown metastable polymorph with only a slightly higher enthalpy. This structure also shows stacked features, but with sulfur atoms alternating in a prismatic environment. 2 / ∞ The structure is constructed on a full-reminiscence stack of [La2O2]fluorine-type (001) slabs (La2O2S2). Similar to hP-La2O2S, this metastable polymorph, with an orthorhombic Amm2 space group, is hereafter referred to as oA-La2O2S. The thermal and kinetic stability of these two structures was further confirmed by ab initio molecular dynamics (AIMD) simulations, in which both hP- and oA-La2O2S retained their primary structural framework after 10 ps at temperatures up to 600 K. Consequently, theoretical calculations clearly predict the possible existence of a metastable oA-La2O2S phase other than the already known hP-La2O2S phase.

[0064] Then, alkali metal Rb was dissolved in a vacuum-sealed Pyrex tube at low temperature. 0We attempted topochemical desorption of sulfur into the layered precursor La2O2S2 by reaction with HCl. Once the excess Rb (and its salts) was washed out with dry ethanol (see synthesis procedure in the SI), powder X-ray diffraction (XRD) patterns were collected for the products synthesized at 200 °C and 350 °C. Both were found to be very similar and did not reveal any known phases. Furthermore, EDX analysis of the bulk product powder clearly showed the absence of rubidium and a La / S molar ratio of 2.0(2) / 1.0(1) (see Figure 5). These results indicate the formation of a sulfur-deficient La2O2S phase without incorporating Rb into the structure. Although no hP-La2O2S XRD peaks were detected in the X-ray patterns, the presence of the polymorph oA-La2O2S predicted by USPEX was confirmed by the goodness of fit X. 2 This could be easily verified via the Riedveld method with a σ = 1.33 and a Bragg reliability factor R(obs) = 1.67%, see table below.

[0065] [Table 1]

[0066] Scanning transmission electron microscopy (STEM) similarly supports the conclusion that the newly synthesized phase is oA-La2O2S. 2 / ∞ The stacking of [La2O2] infinite sheets and fluorine-type (100) slab structures is clearly visible in high-angle annular dark-field (HAADF) STEM images. In contrast, the fluorite-type (111) slabs characteristic of the stable polymorph hP-La2O2S could not be found in the experimental STEM images. The EDX spectrum of the nanosized single crystals was consistent with the composition of La2O2S, as was the EDX analysis of the bulk powder. The structural arrangement of the new oA-La2O2S compound is directly inherited from the one of La2O2S2. This observation clearly confirms the topochemical nature of the deintercalation process. The sulfur deintercalation process is 2 / ∞It does not modify the integrity of the [La2O2] slab at all, but creates one slab along the 1 / 2(b+c) direction of the original La2O2S2 structure (SG:Cmca). 2 / ∞ The [La2O2] layer shifts to two or more layers. Raman spectroscopy confirmed the complete loss of sulfur dimers along the topochemical reduction, i.e., the peaks at 487 and 498 cm in La2O2S2. -1 The band associated with the S-S stretching mode located at (S2) completely disappeared after deintercalation of one sulfur atom from La2O2S2, confirming the conclusion drawn from the XRD pattern that the reaction of hP-La2O2S towards oA-La2O2S was complete. Finally, the diffuse reflectance spectrum also showed that (S2) 2- This confirms the splitting of the dimer. The adsorption threshold is * -σ * The characteristic value of the electronic transition shifts from 2.50 eV in La2O2S2 to 3.88 eV in oA-La2O2S, which is slightly lower than that observed in hP-La2O2S (4.13 eV). Thus, during the reaction of La2O2S2 with elemental rubidium, the alkali metal causes the breaking of the S-S bond (S2). 2- It was concluded that the Cu intercalated in the La2O2S2 host lattice activates the redox reaction with the dimer. 0 Unlike nanoparticles (Angew. Chem. Int. Ed. 57, 13618~13623 (2018)), Rb 0 leads to the topochemical desorption of sulfur to provide the oA-La2O2S metastable phase. The choice of reducing agent is crucial for the outcome of the reaction. When La2O2S2 was treated under a reducing atmosphere, i.e., under a 5% H2 / Ar flow, at 200-300 °C, no reaction occurred. Finally, reduction occurred at 350 °C, which ultimately terminated in the thermodynamically stable hP-La2O2S, where the original fluorite (100) slab was transformed into a fluorite (111) slab. This result supports the comparison of common reducing agents such as H2 with the more powerful reducing agent Rb, which favored the topochemical reduction to oA-La2O2S even at the same reaction temperature (350 °C).0 emphasizes the comparison with

[0067] At this stage, a hypothesis was put forward as to whether the topotactic deintercalation of La2O2S2 could be reversible at low temperatures. To test this possibility, a portion of oA-La2O2S was mixed with 1 equivalent of sulfur and heated at 200 °C (Figure 3a). As shown in Figure 3b, the product was analyzed using XRD. The original La2O2S2 material could be completely recovered without any by-products, and the reversibility of the temperature-assisted intercalation / deintercalation process was confirmed based on the formation / breakage of sulfur dimers within the La2O2S / La2O2S2 layered oxychalcogenide. To gain more insights into the intercalation of sulfur, the reactivity of oA-La2O2S towards only half an equivalent of sulfur at low temperatures was also tested. The XRD pattern of the product obtained from the intercalation of 0.5S into oA-La2O2S at 200 °C (see Figure 3b) clearly demonstrates the conversion of oA-La2O2S into an unknown intermediate phase with a small amount of La2O2S2. The XRD pattern of the intermediate phase was similar to that of oA-La2O2S but shifted to lower diffraction angles, suggesting the presence of an intercalated oA-La2O2S x phase (1 < x < 2.0). The same XRD pattern was observed while attempting to deintercalate 0.5S from La2O2S2 using 1.0 equivalent of Rb 0 , 1.0 equivalent of Ag and 0.5 equivalent of Ni 0 (Figure 3c). The cell parameters of approximately 8.4 Å, approximately 4.0 Å and approximately 12.8 Å and the same space group as oA-La2O2S (Amm2) without any superstructure peaks allowed the refinement of the diffraction pattern of oA-La2O2S 1.5 . This clearly demonstrated the existence of an intermediate phase with a strong reminiscence of the oA-La2O2S structure. This new intermediate phase has half of the single-atom S 2- while retaining the main structural framework of oA-La2O2S as a dimer (S2) 2-One reasonable hypothesis is that the partial dimerization occurs due to the substitution of anions with the oA-La2O2S 1.5 Indeed, both the intercalation of 0.5S with metal species and the deintercalation of 0.5S resulted in the formation of a 413-417 cm -1 The Raman spectra were similar, featuring a single strong peak at 400-500 cm, while the Raman peaks from oA-La2O2S or La2O2S2 were absent. -1 The strong peaks around the α- and β-bonds are characteristic of the SS stretching mode (Angew. Chem. Int. Ed. Engl. 14, 655-720 (1975)). These Raman spectra indicate that the α- and β-bonds are formed through partial cleavage of the SS bond. 1.5 This confirms the formation of

[0068] To solve the crystal structure of this novel phase, we performed precession electron diffraction tomography (PEDT) analysis. This emerging technique can reduce dynamic diffraction effects during data collection, allowing complex structures to be solved ab initio using a single nanocrystal. Therefore, PEDT data were collected on multiple nanocrystals of the novel phase. All data sets were analyzed using the computer programs PETS2.0 (Acta Crystallographica, B75, 512-522 (2019)), Superflip (Journal of Applied Crystallography, 40, 451-456 (2007)), and Jana2006 (Zeitschrift fur Kristallographie, 229, 345-352 (2014)). The orthorhombic unit cell a = 8.348 Å, b = 3.961 Å, and c = 12.645 Å (V = 418.1 Å). 3 ) and a reconstruction of the reciprocal lattice planes hk0, h0l, and 0kl, consistent with the non-centrosymmetric space group Amm2, were observed. The structure was then solved and refined using the Jana2006 program based on electron diffraction data. The structural analysis converged with an electron Bragg reliability factor R(obs) = 10.1%, yielding the composition oA-La2O2S 1.5The new structure obtained is a stacked structure with S 2- and (S2) 2- alternating with sulfur layers containing one-third and two-thirds sulfur anions as seeds 2 / ∞ [La2O2] consists of a fluorine-type (001) infinite slab. 1.5 The structural model was used to successfully refine powder XRD patterns (see Figure 3) from both sulfur intercalation and deintercalation, i.e., from the oA-La2O2S+0.5S and La2O2S2+0.5Ni reaction mixtures. To reach a satisfactory fit, large distortion parameters had to be considered. This can be interpreted as a signature of stacking disorder that occurs predictably during the intercalation or deintercalation process in relation to the 2D structure of the host lattice and the possible presence of different phases. The structural analysis was based on data collected on the best crystallized crystals. However, in most of the PEDT data, stacking faults lead to diffuse scattering features along the

[0001] axis. The experimental contrast in the HAADF-STEM images is 2 / ∞ We assert stacking of infinite slabs of [La2O2]fluorine type (001). This specific oA-La2O2S 1.5 Similar structures were independently predicted by the compositional evolutionary algorithm USPEX. The most stable predicted structure was in good agreement with the experimental structure obtained by PEDT analysis. The second and third most stable structures displayed a 1D slab and a 2D hexagonal (fluorine-type (111)) slab, because their [La2O2] units and these slabs constituted an intergrowth structure with a (quasi-)2D array of sulfur dimers / atoms. However, neither of them could be found in the experiments performed.

[0069] This research work demonstrates the deintercalation and reintercalation of sulfur within layered oxychalcogenide compounds using a unique topochemical approach. Alkali or transition metals can be used as reducing agents to induce the reduction of chalcogenide oligomers and the rupture of chalcogen-chalcogen bonds. In the case of La2O2S2, the low-temperature deintercalation of sulfur atoms proceeds in two steps, resulting in the formation of two new metastable phases, oA-La2O2S, which retain the layered character of the precursor. 1.5 and form oA-La2O2S. This is a fully reversible topotactic process, since the sulfur atoms can be reintercalated at low temperatures to form the precursor La2O2S2 again, as illustrated in Figure 4.

[0070] [Table 2]

[0071] 1. Synthesis Procedure The initial precursor La2O2S2 was synthesized according to the procedure described in Angew. Chem. Int. Ed. 2018, 57, 13618-13623.

[0072] oA-La2O2S:S by Rb 2- Topochemical deintercalation of anions Prior to the preparation, all laboratory glassware and equipment were dried in an oven (T = 80 °C). Under an argon atmosphere, La2O2S2 and Rb (Aldrich, 98+%) were weighed in a molar ratio of 1:2 and introduced into a quartz tube whose bottom was protected with a carbon coating. All of these preparations were carried out under an argon atmosphere. Afterwards, the Pyrex tube was vacuumed (approximately 10 -3 The mixture was then heated to a pressure of 1000 torr and sealed. -1The mixture was heated to 200 °C at a rate of 0.1% and annealed for 2 hours. Finally, the sealed mixture was gradually cooled in the furnace to yield a pale gray-blue powder. The excess Rb was deposited on the other side of the quartz tube. The quartz tube was opened under an argon atmosphere, and the entire contents were quenched with an excess of ethanol (Caution: Rb ignites upon contact with ethanol under ambient conditions). The colorless precipitate was contaminated with small carbon flakes, which were separated by repeated decantation with mechanical stirring. The precipitate was then washed with ethanol, water, and acetone, and then vacuum-dried to yield a colorless powder of oA-La2O2S. This product was stable under ambient conditions. The same reaction performed at 350 °C also provided identical results: pure oA-La2O2S without any trace of hP-La2O2S or any other impurities.

[0073] Intercalation of sulfur anions into oA-La2O2S Colorless powder of oA-La2O2S (approximately 200 mg) was combined with S flakes (Aldrich, 99.99%+%) in a molar ratio of oA-La2O2S:S = 1:0.5 and ground in an agate mortar under an argon atmosphere. The mixture was then pelletized and sintered under vacuum (approximately 10 -3 The mixture was sealed in a quartz tube at 100°C for 1 h. -1 The mixture was heated to 150–200 °C at a rate of 0.1–0.25°C and annealed for 4–48 h (see Figure 3b for the results), followed by gradual cooling in the furnace to obtain pale yellow pellets. If the sulfur was not completely consumed, residual sulfur was deposited on the other side of the quartz tube. To complete the intercalation, the resulting pellets were ground with an additional 0.5 equivalents of S under an argon atmosphere. The mixture was again subjected to heat treatment at 200 °C in an evacuated quartz tube. After annealing for 160 h, the mixture was completely converted to pale yellow pellets of pure La2O2S2.

[0074] oA-La4O4S3: S with various metals 2- A general procedure for the topochemical deintercalation of anions. Detailed synthesis conditions (i.e., stoichiometry, annealing duration, and form of metal source) for each metal species are described below. 1.0 equivalent of La2O2S2 (approximately 150-250 mg) was added with 0.5-2.0 equivalents of the metal element, and the mixture was ground together under an argon atmosphere until the powder became grayish and sticky in an agate mortar. The mixture was then pelletized and sintered under vacuum (approximately 10 -3 The mixture was sealed in a quartz tube at 175°C (torr). -1 The mixture was heated to 350 °C at a rate of 1000 kJ / s and annealed for 2–4 h. Finally, the sealed mixture was gradually cooled in the furnace to obtain a mixture containing oA-La4O4S3 (see Figure 3c for its XRD).

[0075] Reaction with Ag: 1.0 equiv. of Ag powder (Aldrich, 2-3.5 μm, 99.9% or higher) was added. Annealing: 4 h. Neither the slight excess (approximately 1.1 equiv.) of Ag nor the extended / repeated heat treatment led to further consumption of La2O2S2.

[0076] Reaction with Ni: 0.5 equivalents of Ni nanopowder (Aldrich, <100 nm, 99%) was added. Annealing: 4 hours. Extended and repeated heat treatments did not improve the yield of oA-La4O4S3 and ended in partial decomposition to hP-La2O2S. [Explanation of symbols]

[0077] 1 positive electrode 2 negative electrode 3. Conductive electrolyte 4 Current collector 5. Electroactive Material Layer 6 Current collector 7 layers 8 Electrolytes

Claims

1. 1. An electroactive material for an electrochemical cell electrode comprising a chalcogen oligomer, characterized in that said material can reversibly deintercalate anions of said chalcogen by reduction and reintercalate said anions by oxidation while maintaining its overall structure, said active material being La 2 O 2 S 2 , 【Chemistry 1】 An electroactive material that reversibly deintercalates and reintercalates S 2− according to the reaction: oA = 0.05 + ...

2. A positive electrode comprising the material of claim 1.

3. 3. The positive electrode of claim 2 comprising a current collector and a coating layer, said coating layer comprising said electroactive material.

4. 4. The positive electrode of claim 3, wherein the current collector is an aluminum sheet.

5. a positive electrode according to any one of claims 2 to 4; - a negative electrode, and an electrolyte layer sandwiched between a positive electrode and a negative electrode; 1. An electrochemical cell comprising: a first electrode and a second electrode; a second electrode and a third electrode; a second electrode and a fourth ...

6. 10. A battery comprising a plurality of electrochemical cells according to claim 5, wherein the cells are electrically connected.

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