Applications of transition metal sulfide compounds in the positive electrode of solid-state batteries

Abstract

This invention generally relates to the use of transition metal sulfide compounds in the positive electrode of a solid-state battery, transition metal sulfide compounds, devices or materials incorporating said compounds, such as composite materials, electrodes, electrochemical energy storage batteries or devices, such as all-solid-state batteries. This invention also relates to methods of manufacturing and / or using such compounds, materials, or devices, and methods of manufacturing said compounds, materials, and / or devices.

Description

Technical Field

[0001] This invention generally relates to the use of transition metal sulfide compounds in the positive electrode of a solid-state battery, transition metal sulfide compounds, devices or materials incorporating said compounds, such as composite materials, electrodes, electrochemical energy storage batteries or devices, such as all-solid-state batteries. This invention also relates to methods of manufacturing and / or using such compounds, materials, or devices, and methods of manufacturing said compounds, materials, and / or devices. Background Technology

[0002] As the importance of developing efficient energy storage technologies for portable electronic devices continues to grow, the motivation to develop high-energy-density lithium-ion (Li-ion) batteries is also increasing.

[0003] In this respect, solid-state batteries (SSBs) are well-suited for achieving suitable high energy densities, where the electrolyte is in a solid state rather than a liquid or gel. In fact, solid electrolytes (SEs) enable the use of high-voltage positive electrode materials containing lithium metal and alkaline negative electrodes. In particular, due to the non-uniform current distribution, solid electrolytes allow for the prevention of dendrite formation that occurs during the repeated shuttle of lithium between the two electrodes (positive and negative). Furthermore, solid-state batteries do not require any separators, unlike lithium-ion batteries which use liquid electrolytes to stack electrochemical cells. Therefore, for solid-state batteries, a bipolar stack structure with reduced spacing between each pair of individual cells and a thinner current collector becomes possible. Consequently, solid-state batteries allow for a reduction in the battery weight and volume required to achieve higher energy densities (see Janek, J. et al.).

[0004] However, unlike batteries that use liquid electrolytes, solid-state batteries have a poor ion permeation pathway between the active material and the solid electrolyte, whereas liquid electrolytes permeate through porous electrodes, thus providing a good ion permeation pathway (see Kalaya, N. et al.).

[0005] In this regard, Kanno et al. have suggested the use of Li in materials with "lithium superionic conductor" properties. 10,682–686 (2011) 10 GeP2S 12 As a solid electrolyte, its conductivity is equivalent to that of current lithium-ion liquid electrolytes (10). -2 (S / cm). However, it was found that germanium in solid electrolytes impairs chemical compatibility with metallic lithium. Furthermore, germanium is a high-cost raw material, which hinders its large-scale application in lithium-ion batteries.

[0006] Some lithium SSB configurations include the use of layered oxide materials as the positive electrode material, such as LiNi. x Mn y Coz O2(NMC), Li 1-x MnO2(LMO) and Li 1-x CoO2 (LCO), and sulfide-based solid electrolytes such as Li3PS4, have shown better compatibility with lithium metal (or its alloys, such as lithium-indium alloys) used as negative electrodes. This is exemplified by Koerver, R. et al. in "Redox Active Anode Interfaces in Solid-State Batteries" in *Journal of Materials Chemistry A*, A 5, 22750–22760 (2017), which describes the application of a layer of oxide LiNi... 0.8 Mn 0.1 Co 0.1 O2 (NMC-811) and a sulfide solid electrolyte β-Li3PS4 are ground together to obtain a positive electrode active material, with the aim of improving the compatibility between the positive electrode active material and the sulfide solid electrolyte. The solid-state battery comprises:

[0007] A milled mixture of 70 wt.% NMC-811 and 30 wt.% solid electrolyte β-Li3PS4 was used as the positive electrode active material.

[0008] -β-Li3PS4 as a solid electrolyte, and

[0009] - Indium foil as the negative electrode active material (in its original state, after the first charge, it forms a lithium-indium alloy).

[0010] Koerver et al. observed that at higher voltage limits (above 4.0 V for Li / Li + Under these conditions, this configuration still cannot prevent the degradation of the solid electrolyte. Furthermore, the interface between the positive electrode and the solid electrolyte remains poor in this configuration due to:

[0011] -Due to O 2- Li attracts on the surface of the solid electrolyte + The greater capacity to generate ion depletion regions; and / or

[0012] - The chemical reactivity of layered oxides relative to electrolytes.

[0013] To alleviate concerns about the depletion region, oxide coatings, such as LiNbO3 and ZrO3 coated with Li-based basal oxides, have been proposed (see Culver, SP et al. and Xiao, Y. et al.). It is assumed that the oxide coating does not form an ion depletion region.

[0014] However, such oxide coatings did not exhibit this effectiveness when used with sulfide electrolytes. In fact, Xiao, Y. et al., in their computational screening of positive electrode coatings for solid-state batteries in Joule (2019), did not recommend using oxide coatings (such as LiNbO3) with sulfide solid electrolytes (such as β-Li3PS4) due to their high chemical reactivity.

[0015] Furthermore, Culver, SP et al., in "On the Functionality of Coatings for Positive Electrode Active Materials in Thiophosphate-Based All-Solid-State Batteries" (Adv. EnergyMater.) (2019), also taught that coating layered oxides such as NMC or LCO with sulfides such as thiophosphates or even metals does not alleviate the problems associated with the instability of these sulfides to layered oxides at high voltages. Summary of the Invention

[0016] Therefore, an object of the present invention is to provide a novel electroactive compound that can control the oxide positive electrode material / sulfide solid electrolyte interface, and an electrochemical energy storage device that houses such a material. Another object of the present invention is to provide a compound and / or material (e.g., a composite material) that overcomes one or more of these disadvantages of prior art materials and devices, and / or has one or more of the following properties:

[0017] -Chemically stable, especially compared to oxide compounds or materials used in SSB technology (pure oxide-sulfide interface);

[0018] - Obtain an interface or compound that allows lithium intercalation (or has electrochemical activity); and

[0019] - Electrochemically stable, and electrochemically stable within the operating voltage range of commercially available oxides (e.g., relative to Li / Li). + (Voltage is 3V to 4.3V).

[0020] Twenty years ago, Li x FeS2 has been disclosed as a potential negative electrode active material in solid-state lithium batteries (see Takada et al.). However, the use of such a material (FeS2) has proven uncertain because it is unstable at room temperature.

[0021] It has now been found that mixing a transition metal sulfide compound, preferably a lithium-based sulfide compound (hereinafter referred to as Li-active sulfide or Li-insertion sulfide), with a layered oxide compound (hereinafter referred to as Li-active oxide or Li-insertion oxide) provides at least one, preferably a plurality of the above-mentioned desired properties. It has also been found that certain transition metal sulfide compounds can themselves be used as stabilizing materials for the positive electrode of a solid-state battery (SSB). The "active material" means that the material is capable of reversible exchange of ions (such as Li + ) through insertion or conversion reactions.

[0022] Therefore, a first aspect of the present invention is the use or method of use of a ternary (commonly referred to as "trivalent") transition metal sulfide compound as an active material for the positive electrode of a solid-state battery, said compound being preferably a chalcogenide compound and further combined with an alkali (hereinafter referred to as "alkali") such as lithium, sodium and potassium (i.e., containing them). According to this aspect of the present invention, the ternary transition metal compound of the present invention can have only one transition metal. In this particular case, the transition metals are selected from the group consisting of: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Au, Rf, Db, Sg, Bh, Hs and Cn. Transition metals that can form layered sulfides are preferred. In particular, iron, titanium, manganese, nickel, vanadium and their combinations are preferred metals. Preferably, the transition metal sulfide compound of the present invention contains at least two transition metals.

[0023] The ternary metal sulfide compound is preferably a layered sulfide compound, such as Li2TiS3.

[0024] The "third transition metal sulfide compound" or "ternary transition metal compound" refers to a compound having the empirical formula I, which has the elemental formula A x B b S z , where A is at least one alkali, and "x" is the atomic content of this or these alkalis (per formula unit). Preferably, A is a single element. Further preferably, the alkali is selected from the group consisting of: Li, Na or K. Lithium is the preferred alkali, especially for solid-state lithium batteries. The ratio x is a number in the range 0 < x < 3. When the alkali is lithium, the number "x" is preferably selected in the range 0.8 to 2.5, or x is 0.8 < x < 2. Preferably, x is equal to 1 or 2. The ratio x can also be selected in the range 0.9 to 1.5.

[0025] B is at least one transition metal, and preferably two or more. The atomic content of the transition metal b is preferably 0.5 to 3, more preferably 1 to 3. It can advantageously be 1, 2 or 3. This transition metal compound advantageously further comprises at least one basic compound. The elemental content of the metal atoms can be measured by atomic emission spectroscopy.

[0026] To achieve the operating voltage range of commercially available oxides, it is also preferable that B is at least two different transition metals. In this case, it is further preferred that the transition metal sulfide is a non-stoichiometric compound. When B b When B is at least two transition metals, it can have the empirical formula M. y N w M and N are different, preferably abundant transition metals, and y and w are the atomic contents of (one or more) elements M and N, respectively.

[0027] “z” is the atomic content of sulfur and is equal to x+b.

[0028] Preferably, the transition metal sulfide of the present invention is in powder form, advantageously a fine powder. Fine powder refers to powder particles with a particle size or average particle size D measured by standard laser diffraction methods. 50 Less than 5 micrometers, advantageously less than 2 micrometers.

[0029] According to a preferred embodiment, the solid electrolyte (i.e., ion conductor) material can be mixed with a ternary transition metal sulfide compound to form an active electrode material. The solid electrolyte material can be of any type, such as ceramic or polymer, but sulfide compounds are advantageous, such as lithium sulfide, silicon sulfide, phosphorus sulfide, particularly thiophosphate, boron sulfide, or mixtures thereof. For example, sulfide or sulfide-based electrolytes may comprise compounds selected from components such as SiS2, GeS2, B2S3, and Li7GeP2S. 10 Li7GePSI-Cl (or argillium sulfide), amorphous (or glassy) Li3PS4, crystalline β-Li3PS4, and mixtures thereof. β-Li3PS4 is particularly preferred.

[0030] The relative weight ratio of ternary transition metal sulfides in the solid electrolyte can be 0.5 to 4, preferably 1 to 3, and more preferably 1.8 to 2.7 (e.g., 70:30).

[0031] The electrode comprising a transition metal sulfide compound, particularly a positive electrode, as described with reference to the first aspect of the invention, is also an object of the invention. Another object of the invention is an electrochemical battery or accumulator, particularly a solid-state battery, preferably a lithium-ion battery, comprising a positive electrode as defined above. The battery or accumulator also comprises a negative electrode and an electrolyte. Another object of the invention is a method for manufacturing a positive electrode, electrochemical battery, or accumulator, particularly a solid-state battery, preferably a lithium-ion battery, the method comprising the steps of providing a transition metal sulfide as described in the first aspect of the invention and manufacturing an electrode, battery, and / or accumulator containing it.

[0032] A second aspect of the invention is the use or method of using transition metal sulfide compounds as electrode active materials in solid-state batteries, wherein the transition metal sulfide compound is preferably a chalcogenide compound, combined or combined with an oxide compound, wherein the oxide compound is preferably a Li-intercalated oxide or a Na-intercalated oxide. This combination between the oxide and the sulfide is referred to as a composite material; the composite material is also an object of the invention. According to this second aspect of the invention, the transition metal sulfide has the empirical formula IIB. b S z Where S is sulfur, and B may contain one, two, or more transition metals selected from the group consisting of: Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Rh, Pd, Ag, Hf, Ta, W, Re, Os, Ir, Pt, Au, Rf, Db, Sg, Bh, Hs, and Cn. Transition metals that can form layered sulfides are preferred. When the transition metal sulfide contains a single transition metal, the compound is preferably a stoichiometric compound. More preferably, the transition metal is a transition metal selected from the group consisting of: titanium, iron, manganese, nickel, and vanadium.

[0033] The transition metal sulfide compound that can be used according to the second aspect of the invention is advantageously a compound of formula II: B b S z In Formula II, S is sulfur, and "z" represents the atomic abundance of this element, which is a number in the range of about 1 to 3. Preferably, "z" is a number in the range of 0.9 to 1.1, 1.9 to 2.1, 2.9 to 3.1, or 3.9 to 4.1. In particular, z can be equal to 1, 2, or 3.

[0034] B is at least one transition metal, and preferably two or more. The atomic content b of the (one or more) transition metals is preferably in the range of about 1 to 2. It can advantageously be 1 or 2. The elemental content of the metal atoms can be measured by atomic emission spectroscopy.

[0035] This transition metal compound advantageously further comprises at least one basic compound. Such ternary compounds may have the basic formula IA. b b e s s , where A, B and S are as defined with respect to Equation I.

[0036] To achieve the operating voltage range of commercially available oxides, it is also preferable that B is at least two different transition metals. In this case, it is further preferred that the transition metal sulfide is a non-stoichiometric compound. When B b When B is at least two transition metals, it can have the empirical formula M. y N w Where M and N are different, preferably abundant transition metals, and y and w are the atomic contents of (one or more) elements M and N, respectively. It is also preferred that the transition metal sulfide of the present invention is in powder form, advantageously a fine powder. Fine powder refers to powder particles with an average particle size (or median particle size D) when measured by laser diffraction. 50 The micrometer size is less than 5 μm, preferably less than 2 μm.

[0037] Oxide materials are active oxide compounds or combinations thereof, and can be of the types used in SSB technology, such as oxides, layered oxides, or spinel-type materials. Referring specifically to solid-state lithium batteries, these oxides typically have an empirical formula A. x C c O z Where O is oxygen, x is as defined above, c is a number in the range of 1 to 3, and z equals x + c. A is a base, such as Li, Na, or K, preferably lithium. C contains at least one element from Groups 2 to 13, and in particular, C may contain at least one transition metal oxide. The oxide active material can be a non-stoichiometric transition metal oxide. For example, such an oxide material can be lithium nickel manganese cobalt oxide (LNMC oxide), such as LiNi 0.6 Mn 0.2 Co 0.2 O2 or Li (Ni 0.33 Mn 0.33 Co 0.33 )O 2, Lithium cobalt oxide (LC oxide), lithium manganese oxide (LM oxide), LiFePO4, LiNiMnO2, or mixtures thereof. For solid-state lithium or sodium batteries, the oxide may further have formula A. 3+d Cl 1-d D d O, where Dd is greater than zero, A is at least Li and Na, and D is at least one of S, Se, and N. Oxide materials are typically in the form of particulate powders. The size or average particle size D of the powder particles is measured by standard laser diffraction methods. 50Preferably less than 20 micrometers, advantageously less than 10 micrometers.

[0038] According to a second aspect of the invention, another object of the invention is a composite material comprising a mixture or combination of layered or active oxide materials and transition metal sulfide compounds, as described above with reference to the second aspect of the invention, or a combination of said compounds.

[0039] The composite material advantageously comprises a tight bond of sulfides and oxides. This tight bond can comprise a mixed powder, which can be obtained by mixing, milling, and / or grinding the two materials. The powders of oxide and sulfide materials are ground together to obtain a material with an average particle size (or median particle size D). 50 The powder, wherein the particle size can be 10 μm or smaller, preferably 2 μm or smaller, more preferably 1 μm or smaller. Preferably, when measured by laser diffraction, it can be in the range of 0.1 μm to 10 μm, preferably 1 μm to 10 μm (e.g., about 2 μm). When used as a mixed powder, the sulfide to be used is preferably a sulfide containing a base as defined in Formula I. The base to be selected is a base corresponding to the ion species (Li+, Na+, Ca+) to be used for exchange between the electrodes of the SSB.

[0040] In the composite material of the present invention, the relative weight ratio of oxide to transition metal sulfide can be 0.1 to 30, preferably 0.7 to 15, more preferably 0.1 to 1.2 or 1 to 15 (e.g., about 1:1 or 9:1).

[0041] The composite material may comprise the mixed powders as described above and / or particles having a core and a coating, wherein the core comprises layered or active oxide materials and the coating comprises transition metal sulfide compounds. The composite material may consist substantially of these coated particles, or contain only a portion of them, or even a negligible portion thereof. "Substantially constitutes" means that more than 90% by weight of the composite material is made of coated particles. However, it is preferred that the composite material of the present invention contains 10 to 70%, preferably 20 to 50%, and especially 30 to 40% by weight of the aforementioned coated particles.

[0042] The core can be of any specific shape, such as spherical, oval, complex, and / or aggregated. Preferably, the core has an average particle size or median particle size D in the range of 20 μm to 5 μm, preferably 12 μm to 8 μm, and more preferably 11 μm to 9 μm (e.g., about 10 μm). 50 .

[0043] The coating may be only partially coated and / or have an irregular shape and / or thickness. The thickness of the layer is preferably less than 100 nm, preferably in the range of 1 to 10 nm. This can be measured using a transmission electron microscope. The coating acts as a protective barrier, preventing the formation of ion depletion zones on the particle surface. The sulfide compound used as a coating does not necessarily contain a base. Base-free compounds of formula II improve the oxide / electrolyte interface.

[0044] When the transition metal sulfide is a ternary compound and includes a base, particularly lithium or sodium, it exhibits another effect because the compound is electrochemically active and stable over the operating voltage range of most commercially available oxides used as positive electrode materials for batteries.

[0045] According to a preferred embodiment, the composite material of the second aspect of the invention may further comprise a solid electrolyte (i.e., an ion conductor) material. The solid electrolyte material may be of any type, such as ceramic or polymer, but sulfide compounds, such as lithium sulfide, silicon sulfide, phosphorus sulfide, such as thiophosphate, boron sulfide, or mixtures thereof, are advantageous. For example, sulfide or sulfide-based electrolytes may comprise compounds selected from the following components: SiS2, GeS2, B2S3, Li7GeP2S 10 Li7GePSI-Cl (or argillium sulfide), amorphous (or glassy) Li3PS4, crystalline β-Li3PS4, and mixtures thereof. β-Li3PS4 is particularly preferred.

[0046] In such embodiments, the relative weight ratio of oxides and transition metal sulfides in the solid electrolyte can be in the range of 0.5 to 4, preferably 1 to 3, more preferably 1.8 to 2.7 (e.g., 70:30).

[0047] In one embodiment, the initial specific capacity of the positive electrode material (obtained after the first discharge) is in the range of 150 to 250 (mAh·g⁻¹). This range of specific capacity can be obtained at a charging rate in the range of C / 50 to C / 5 (hereinafter referred to as the "C rate"). The C / 50 rate corresponds to the complete removal or insertion of lithium ions from the compound of the present invention within 50 hours.

[0048] The composite material according to the second aspect of the invention can be manufactured by known methods. Preferably, it comprises mixing particles of a layered oxide material with a transition metal sulfide, which can also conveniently be in powder form. Mixing is advantageously carried out by mechanical milling, such as ball milling. When ball milling is chosen, the powder-to-ball weight ratio can be in the range of 1:40 to 1:20, for example, 1:36. The rotational speed of the ball mill can be in the range of 100 rpm to 200 rpm, for example, 140 rpm. The duration of ball milling can be in the range of 1 minute to 5 hours, for example, 30 minutes. When the composite material contains a solid electrolyte, the composite material can be manufactured by mixing and / or milling a mixture of the electrolyte material powder with a mixture of the already mixed (e.g., ground) layered oxide and transition metal sulfide composite material. To obtain coated particles, one or a combination of techniques selected from atomic layer deposition, pulsed laser deposition, spraying, sputtering, sol-gel methods, and pyrolysis can be used.

[0049] As illustrated in the examples, ternary transition metal sulfides or composite materials according to either the first or second aspect of the invention can be advantageously used in SSB technology. Therefore, another object of the invention is an electrode material, preferably a positive electrode material, which comprises, is composed of, or is substantially composed of the composite material or ternary transition metal sulfide described above.

[0050] The electrode material can advantageously be a compressed material shaped into a positive electrode. This compressed material or granules can be of any shape to suit its use as a component of an electrochemical cell and / or accumulator.

[0051] Another object of the present invention is an electrochemical battery comprising at least two electrodes (a positive electrode and a negative electrode) in contact with an ionic conductor (i.e., an electrolyte). Each electrode has some electronic conducting properties. According to the invention, the positive electrode comprises a composite material according to the invention, is composed of a composite material according to the invention, or is substantially composed of a composite material according to the invention. As is known in the art, the electrode is configured to reversibly accept or release alkaline ions, such as lithium or sodium, transferred by the ionic conductor (electrolyte).

[0052] The negative electrode may comprise an active material selected from the group consisting of known active materials used for negative electrodes in SSB batteries. When the SSB is a lithium-ion battery, the material may be a well-known negative electrode active material for lithium-ion batteries, such as hard carbon, soft carbon, carbon black, Ketjen black, acetylene black, activated carbon, carbon nanotubes, carbon fibers, amorphous carbon, and other carbon materials. Metals, lithium-containing metals, and alloys may also be used, as they can also serve as a source of lithium in the battery. Suitable metals include, for example, Li, In, Cu, Si, Sn, Sb, Ge, and / or alloys thereof. Lithium-containing metal oxides, metal nitrides, and metal sulfides are also useful, particularly in combination with Ti, Mo, Sn, Fe, Sb, Co, and V. Phosphorus or metal-doped phosphorus (e.g., NiP3) may also be used. In one example, the active material for the negative electrode is indium, LiIn, LixSn (e.g., Li 4.4 Sn) and / or pre-lithiated indium-copper alloys.

[0053] The electrolyte is advantageously a solid electrolyte as described above. When the composite material of the present invention contains an electrolyte material, the electrolyte or ion conductor of the electrochemical cell of the present invention advantageously contains or contains the same material.

[0054] Another object of the present invention is a solid-state storage battery comprising at least one electrochemical cell of the present invention and an external connector. In embodiments, the storage battery of the present invention can cycle within an allowable cutoff voltage range of 1.5 to 4.5 V relative to Li / Li+, preferably within the range of 1.9 to 4.3 V relative to Li / Li+, and more preferably within the range of 2 to 4 V relative to Li / Li+. The cutoff voltage can be defined as the voltage at which the storage battery is considered fully discharged or charged, exceeding which further discharge of charge would damage the storage battery. The storage battery of the present invention exhibits good cycle performance and low overpotential. For example, when measured on a platform of 2.5 V relative to Li / Li+, the overpotential is below 200 mV at room temperature (20°C), particularly in the range of 150 mV to 200 mV.

[0055] Advantageously, a storage battery may contain more than one electrochemical cell, and in particular, it may contain a battery stack.

[0056] The size and shape of the external connectors are advantageously designed to supply power to electrical devices.

[0057] The particularly preferred transition metal sulfide compound used in the first and second aspects of the present invention is a transition metal sulfide compound of formula III: Li 1.33-2y / 3 M 0.67-y / 3 N yS2, wherein MN is a combination of two or more transition metals selected from the group consisting of: Sc, Ti, V, Cr, MN, Fe, Co, Ni, Cu, Y, Zr, Nb, Mo, Tc, Rh, Pd, Ag, Hf, Ta, W, re, Os, Ir, Pt, Au, Rf, Db, Sg, Sg. Compounds of Formula III contain a combination of at least two transition metals MN, where Li, M, and N each have an atomic content dependent on y, as shown in Formula III, where y is a number greater than 0 and not greater than 0.5, such as 0.3. When y is less than 0.5, it is a lithium-rich component. Advantageously, one of M and N is a combination of two or more transition metals selected from the group consisting of: Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Pd, Ta, W. It is also particularly preferred that M or N is Fe and / or Ti, because such compounds are stable to air and moisture. Compounds in which N is Ti and M is Fe are particularly preferred. In terms of atomic content, the term "about" can be understood as meaning ±0.05.

[0058] Therefore, the sulfide of Formula III is a particularly preferred material for the aforementioned applications, and as a transition metal compound, it can be part of the composite materials, positive electrode materials, electrodes, electrochemical cells, storage batteries, and especially solid-state lithium storage batteries of the present invention. It has the particular advantages of protecting the layered oxide interface, providing additional specific capacity (compared to the layered oxide itself), and being stable under normal conditions of air, moisture, and temperature.

[0059] Furthermore, devices incorporating batteries according to any aspect of the present invention are also objects of the present invention, such as microgrids for stabilizing power grids, electrochemical storage devices for intermittent renewable energy sources (such as solar and wind power), mobile storage devices for electric vehicles (such as motorcycles, cars, multi-purpose vehicles, buses, trucks, etc.), household power storage devices, and emergency power or energy storage devices for hospitals, schools, factories, computer clusters, servers, companies, and any other public and / or private buildings or infrastructure. Composite materials or devices incorporating said materials according to any aspect of the present invention can be used in the following industries: automotive, computer, banking, video games, leisure, creative, cultural, cosmetics, life sciences, aviation, pharmaceuticals, metals and steel, railway, military, nuclear, naval, aerospace, food, agriculture, construction, glass, cement, textiles, packaging, electronics, petrochemical, and chemical industries. Attached Figure Description

[0060] Specific embodiments of the invention will now be described with reference to the following accompanying drawings, in which:

[0061] Figure 1a shows an exploded perspective view of an apparatus for performing electrochemical measurements from an electrochemical cell, such as chronoamperometry, constant current cycling, and EIS measurements; Figure 1 b is a cross-sectional view of the device taken along line AA.

[0062] Figure 2 Powder X-ray diffraction (XRD) patterns of NMC 622 / LTFS powder mixture, the same composite material after heat treatment, and LTFS and NMC622 powders are shown.

[0063] Figure 3 The current-to-time graphs of NMC 622 / LTFS mixed particles (1:1 weight ratio) before (black line) and after (red line) heat treatment are shown.

[0064] Figure 4 It shows the result of Figure 3 A graph showing the steady current versus applied potential for the determined NMC 622 / LTFS hybrid particles.

[0065] Figure 5 The constant current cycling curves of a battery made from a mixture of LTFS and Li3PS4 in a weight ratio of 70:30 are shown at a C / 50 rate, and the battery was cycled at different temperature ranges (room temperature, 45°C, 75°C, and 105°C).

[0066] Figure 6 The constant current cycling curve (potential-to-capacity ratio) of test battery A at C / 50 rate is shown.

[0067] Figure 7 The constant current cycling curve (potential-to-capacity ratio) of battery B at a C / 50 rate is shown.

[0068] Figure 8 It shows that in relation to Figure 7 The specific capacity (mAh·g) of test battery B obtained under the same conditions -1 As the cycle evolves.

[0069] Figure 9 The constant current cycling curves (potential-to-capacity comparison) of batteries A and b at a C / 50 rate are shown.

[0070] Figure 10 Electrochemical impedance spectroscopy (EIS) spectra of verification battery A and verification battery B obtained after the first charge (in the delithiation state) are shown.

[0071] Example

[0072] Examples 1 through 5 relate to the manufacture of various compounds, materials, and electrochemical cells, and describe apparatuses for manufacturing and testing them.

[0073] Examples 6 through 10 specifically demonstrate that the Li-active sulfide materials are electrochemically active and maintain chemical stability and electrochemical activity despite temperature changes, within the operating voltage range of the positive electrode (e.g., relative to Li / Li). + The oxide (at 4.0V) is electrochemically stable, and the oxide / SE interface is improved when the oxide is mixed with the LTFS of the present invention.

[0074] Example 1: Method for synthesizing lithium sulfide (LTFS) of the present invention

[0075] compound Li 1.13 Ti 0.3 Fe 0.57 S2 (hereinafter referred to as LTFS) was prepared by a solid-state reaction (Liu et al.). For this purpose, 259.6 mg Li2S (Alfa Aesar, 99 w / w%), 728.4 mg TiS2 (Sigma Aldrich, 99.9 w / w%), and 263.7 mg FeS (Alfa Aesar, 99 w / w%) were weighed and uniformly mixed, then hand-milled for 30 minutes. These precursor powders were then filled into quartz tubes in a glove box filled with Ar (O2 and H2O content <1 ppm), and then heated under vacuum (~10 °C). –5 The tube was sealed at a temperature of (mbar). The sealed tube was then annealed at 750°C for 36 hours, followed by water quenching. The resulting compound was collected in a glove box and hand-ground for 10 minutes before storage and further use. Air contact was prevented by sealing when the tube was exposed to the ambient atmosphere. Otherwise, the entire process would have been carried out in a glove box filled with Ar.

[0076] Example 2: Preparation of solid electrolyte β-Li3PS4

[0077] β-Li3PS4 solid electrolyte was synthesized from Li2S and P2S5 via solution in tetrahydrofuran (THF): 328.07 mg Li2S (Alfaea, 99 w / w%) and 529 mg P2S5 (Acros Organics, >98 w / w%) were weighed and homogenized by hand milling for several minutes in an Ar-filled glove box (O2 and H2O content <1 ppm). The mixture was collected and suspended in 25 mL of THF (Sigma-Aldrich, 99.9%) at room temperature.

[0078] The mixture was left to stand for 3 days with continuous stirring. The solid was then recovered by centrifugation at 600 rpm for 3 minutes and washed with pure THF. After washing, the wet powder was transferred to a glass tube and further introduced into a sand bath placed on top of a hot plate. The glass tube was then connected to a Schlenk line (vacuum gas manifold) inside a glove box and evacuated to a final pressure of approximately 0.1 mbar to dry the sample.

[0079] The tube was then left at room temperature for 2 hours, followed by heating at 100°C for 24 hours to remove the remaining THF. Finally, it was heated at 140°C for 18 hours to obtain the final product, β-Li3PS4.

[0080] Example 3: Preparation of the positive electrode composite material according to the present invention

[0081] In the example, the layered oxide used to manufacture the positive electrode composite material is LiNi. 0.6 Mn 0.2 Co 0.2 O2 (hereinafter referred to as NMC622), with an average particle size of 10 μm and a purity of 99.9 w / w%. It is produced by Umicore. TM Company (Umicore) TM (Provided by Brussels, Belgium)

[0082] Inside an argon-filled glove box, LTFS and NMC 622 obtained according to Example 1 were mixed together (weight ratio 1:1), hand-milled for 30 minutes, and further ball-milled in a planetary ball mill at 140 rpm for 30 minutes (powder to ball weight ratio 1:36, 1g powder to 36g of zirconia balls, i.e., 12 3g balls). The ball milling was carried out outside the glove box, and the composite material was contained in two hermetically sealed zirconia ball milling containers.

[0083] Next, the Li-active sulfide β-Li3PS4 from Example 2 was weighed and added to the NMC 622 / LTFS mixture at the desired weight ratio (70% NMC 622 / LTFS and 30% β-Li3PS4). These components were then mixed by hand grinding with a mortar and pestle for 1 hour. This composite material was used to assemble test battery B.

[0084] Another composite material according to the invention was obtained using the same steps as for testing battery B, but without using layered oxide materials. Therefore, LTFS was added to the Li-active sulfide β-Li3PS4 of Example 2 at a weight ratio of (70:30). This composite material was used to assemble and test battery A.

[0085] Another composite material according to the invention was obtained following the same steps as test battery B, but with a different NMC 622 / LTFS ratio. In this material, the weight ratio of test battery B was not 1:1, but 9:1. A mixture of NMC 622 / LTFS was added to the Li-active sulfide β-Li3PS4 of Example 2 at a weight ratio of 70:30 (70% NMC 622 / LTFS and 30% β-Li3PS4). This composite material was used to assemble and verify battery B.

[0086] Another composite material was obtained following the same steps, but without using LTFS. Therefore, NMC 622 was added to the Li-active sulfide β-Li3PS4 of Example 2 at a weight ratio of 70:30 (70% NMC 622 / LTFS and 30% β-Li3PS4). This composite material was used to manufacture verification battery A.

[0087] Example 4: Particle assembly for testing (see Example 6)

[0088] 60 mg of each positive electrode composite material from Example 3 was placed into the dye group and pressed using a hydraulic press at 4 tons / cm². -2 The particles are compressed under pressure for 5 minutes to form particles with a diameter of 8 mm and a thickness of 0.3 mm. The particles are then removed from the dye group.

[0089] Example 5: Battery Assembly

[0090] The homemade battery is used for battery assembly and testing (cycling and EIS) as well as heating and characterization (chronoamperometry) of particulate LTFS / NMC mixtures. The battery casing is capable of pressure monitoring and operates over a temperature range from ambient temperature (approximately 20°C) to 170°C (maximum temperature inside the casing). The casing is used for the aforementioned in-situ heating treatment of the sample, rather than another in-situ heating treatment, which implies direct manipulation of the sample, potentially altering the results.

[0091] Shell structure

[0092] The battery casing 1 can be described as an assembly of three separate cylindrical components, such as... Figure 1 The ones shown better in section a are:

[0093] - Upper piston 3 and lower piston 5; and

[0094] - Central Body Part 7.

[0095] The upper piston 3 includes a top plunger 9, and the lower piston 5 includes a lower plunger 11, both having the shape of a cylindrical rod extending along the longitudinal direction and the central axis A. A nut 13 is located at the top and center of the upper piston 13.

[0096] At the center of the central body portion 7, a hole 15 accommodates plungers 9 and 11 from each of the pistons 3 and 5. The three elements 3, 5, and 7 are assembled by introducing plungers 9 and 11 from both sides of the central body portion 7 along the longitudinal axis A into the hole 15 (located within the central body portion and having a diameter of approximately 8 mm). The housing 1 can be closed or opened by simply inserting (or removing) at least one of the plungers 9 and 11 into the hole 15.

[0097] like Figure 1 As shown in Figure b, the upper piston 3 includes a nut 13, a force sensor 17, and an upper piston 9 in a stacked relationship. The upper piston 9 includes a top electrical contact 19.

[0098] The lower piston 5 comprises a base 21, a body, and a lower plunger 11 in a stacked relationship from bottom to top. The lower plunger 11 also includes a bottom electrical connector 23.

[0099] The central body portion 7 includes an inner insulating sleeve 25 made of polymer material surrounding the orifice 15. The diameter of the internal cavity of the sleeve is approximately 8 mm. When the plungers 9, 11 of each piston 3, 5 enter the orifice 15 from both sides of the body 7, a cylindrical space 27 is created between the ends of each plunger 9, 11. The positive electrode material, solid electrolyte (SE), and negative electrode forming the electrochemical cell can be placed within this space 27. A heating sleeve 29 is disposed around the inner sleeve 25 and is adapted to apply heat to the space 27 and the electrochemical cell located within the space 27.

[0100] Assembly steps of electrochemical cells

[0101] All battery assembly and testing were carried out in an argon-filled glove box (O2 and H2O content <1ppm).

[0102] The battery is assembled at room temperature, without heating, by sequentially loading and pressing each component therein. The electrochemical battery comprises:

[0103] - Solid electrolytes (SE);

[0104] - Positive electrode composite material, comprising the material according to the invention and a commercial oxide; and

[0105] - A negative electrode made of an indium copper disk.

[0106] An indium-copper disk is manufactured by laying 10 mg to 15 mg of indium foil (Sigma-Aldrich, 99% purity, 0.127 mm thickness) on one side of a copper disk cut from copper foil (Goodfellow, 99.99% purity, 0.02 mm thickness) to a diameter of 8 mm. The negative electrode is initially made of indium and does not contain lithium in its original state. However, after the first charge, due to delithiation of the positive electrode, lithium ions from the lithium-ionized positive electrode form an InLi intermetallic phase with indium according to the following reaction: In + Li + +e - =InLi, and lithium is provided at the negative electrode.

[0107] In this way, when performing battery measurements, the negative electrode serves as both the reverse electrode and the reference electrode, while the positive electrode is considered the working electrode.

[0108] At the start of assembly, the upper piston 3 of the outer casing 1 is removed. First, 30 to 35 mg of the solid electrolyte β-Li3PS4 prepared in Example 2 is loaded into the sleeve 25 and evenly distributed on the lower plunger 11 and within the space 27. Variations in the mass of the solid electrolyte within the aforementioned range have no significant effect on the final result. The outer casing 1 is closed by inserting the upper plunger 9 into the sleeve 25. The outer casing 1 is placed vertically in a hydraulic press (not shown), and a 1-ton cm pressure is applied. -2 The pressure is applied for 1 minute (monitored by pressure sensor 17) and maintained for 1 minute. This yields solid electrolyte particles.

[0109] Next, remove the upper piston 3 from the outer casing 1 and load 5 to 10 mg of a positive electrode composite material, which is then evenly distributed on the surface of the pre-pressed solid electrolyte sheet. This amount is sufficient to cover the entire surface of the particles. Close the outer casing 1 and use a hydraulic press to slowly press the plunger 9 against the positive electrode composite material (pressing rate: 0.4 ton-cm every 10 minutes). -2 ), until it reaches 4 tons cm -2 The value. This final pressure is maintained for 2 hours.

[0110] Remove the outer casing 1 from the press and remove the lower piston 5 from the outer casing 1. Flip the casing over and place the indium-copper disk within space 27, ensuring the indium layer of the disk contacts the solid electrolyte layer. Reposition the lower piston 5 and apply the pressure required to compress the battery: 0.5 tons / cm². 2 .

[0111] Once the battery is assembled in the sleeve, the battery is sealed, and the casing 1 is placed in a stainless steel frame (not shown). Bolts (not shown) are set in nuts 13 and tightened with a screwdriver. In this way, the casing is secured to the frame and provides the pressure required for circulation.

[0112] Testing of electrochemical cells

[0113] To perform the cycle, once the desired pressure is set, the housing is connected to a Biologic (Seyssinet-Pariset) VMP-3 potentiostat / galvanostat via a cable connecting the inside and outside of the glove box.

[0114] V pairs (In-InLi) / Li + and V for Li / Li + The conversion between scales is based on the assumption that once lithiation occurs, the In-Li electrode potential remains stable and relative to Li / Li + It was done while maintaining a voltage of 0.6V.

[0115] The following batteries were assembled and tested. Specifically:

[0116] Test battery A

[0117] - Positive electrode composite material: LTFS / β-Li3PS4 composite material (70:30 by weight)

[0118] - Solid electrolyte: β-Li3PS4, and

[0119] - Negative electrode: Li-In alloy (indium on a copper disk).

[0120] Test battery B

[0121] - Positive electrode composite material: NMC 622–LTFS (1:1 weight ratio) and β-Li3PS4 were mixed by hand milling at a weight ratio of 70:30 (70% NMC 622 / LTFS mixture, 30% β-Li3PS4).

[0122] - Solid electrolyte: β-Li3PS4, and

[0123] - Negative electrode: Li-In alloy (indium on a copper disk).

[0124] Verify battery A

[0125] - Positive electrode composite material: NMC 622 and β-Li3PS4 were mixed by hand grinding at a weight ratio of 70:30 (70% NMC 622, 30% β-Li3PS4).

[0126] - Solid electrolyte: β-Li3PS4, and

[0127] - Negative electrode: Li-In alloy (indium on a copper disk).

[0128] Verify battery B

[0129] - Positive electrode composite material: NMC 622–LTFS (9:1 weight ratio) and β-Li3PS4 were mixed by hand milling at a weight ratio of 70:30 (70% NMC 622 / LTFS mixture, 30% β-Li3PS4).

[0130] - Solid electrolyte: β-Li3PS4, and

[0131] - Negative electrode: Li-In alloy (indium on a copper disk).

[0132] Example 6: Preliminary test of the chemical stability of the interface between 1–Li-active oxide and Li-active sulfide

[0133] The suitability and chemical stability of the material, which is free of β-Li3PS4, were tested by X-ray diffraction and chronoamperometry of particles made from a 1:1 weight ratio mixture of NMC622 and LTFS (see Example 5) before and after heat treatment at 100°C in an inert atmosphere (argon) for 5 days. This temperature was chosen to accelerate the interfacial decomposition reaction.

[0134] Once the heat treatment was complete, the battery was cooled to room temperature, and then chronoamperometry was performed on the heated particles. Powders of the original LTFS and NMC were used as XRD references.

[0135] Heated and unheated particles of NMC 622 and LTFS were ground, and the X-ray diffraction patterns of the resulting powders were measured.

[0136] Therefore, the criteria used to define a stable interface are based on a comparison of the X-ray diffraction patterns and electrical resistance of the particles before and after heat treatment.

[0137] The structure of the synthesized powder compound was characterized by X-ray diffraction (XRD) analysis.

[0138] X-ray diffraction (XRD) measurements provide information about the crystal structure of materials. XRD patterns are collected using a Bruker d8 advanced diffractometer. The following parameters are set to collect X-ray pattern data:

[0139] - Detector slit = 9.5mm;

[0140] - Beam slit = 0.6mm;

[0141] - Range: 2θ = 10° to 50°;

[0142] - (Angstrom)(CuKα);

[0143] -Speed: 211 seconds / step;

[0144] - Increment: 0.015°.

[0145] like Figure 2 As shown, the material structure ("fresh NMC 622-LTFS 1:1" and "heated NMC 622-LTFS 1:1") did not change significantly in terms of the number, position, width and intensity of peaks before and after heating.

[0146] Therefore, this result indicates that the crystal structure of the characterized material remains stable after heat treatment.

[0147] Chronoamperometry (CA) Measurement

[0148] In the chronoamperometry method, the current as a function of time is measured after a potential step is applied. Particles made from a 1:1 weight mixture of NMC 622 and LTFS are placed under a potential that increases by 0.01V every 10 seconds, repeated 10 times. A steady-state current is determined at each potential step.

[0149] exist Figure 3 The results are shown in the figure. The small shift in current from the third potential step could be due to temperature variations within the glove box, as each curve was measured on a different day (five days apart). However, the variation is small enough to be attributed to this temperature change. Therefore, the resistance is essentially unaffected.

[0150] Figure 4 A graph showing the steady current versus the applied potential is shown. The resistance is determined to be... Figure 4 The reciprocal of the slope of the curve. No significant change in particle resistance was observed before (2.48 Ω) and after heating to 100 °C (2.57 Ω). Specific conductivity σ was determined using the following relationship: σ = L / (A*R), where L and A are the particle thickness and area, respectively, and R is the particle resistance determined by the slope. During the measurement, the particle size remained constant (diameter = 8 mm, thickness = 0.3 mm). Therefore, conductivity σ remained stable at 0.02 S·cm. -1 Because it changes by only 0.001 s·cm before and after heat treatment. -1 The unchanged conductivity indicates the absence of resistive interlayers formed by decomposition products, thus preventing interfacial reactions. Therefore, the stability of the conductivity despite heat treatment suggests a stable interface between the oxides NMC 622 and NTFS.

[0151] Based on the results of XRD and CA measurements, it can be concluded that the interface between oxide NMC 622 and LTFS remains stable despite heating.

[0152] Example 7: Preliminary testing of materials according to the invention - constant current cycling to test the electrochemistry of Li-active sulfides Learning activity

[0153] To test the electrochemical activity of LTFS, the positive electrode composite material used in test battery A was assembled according to Example 5, using a positive electrode containing a mixture of LTFS and β-Li3PS4 in a weight ratio of 70:30, β-Li3PS4 as a solid electrolyte, and a Li-In alloy as a negative electrode.

[0154] After being left to stand in an open circuit for 5 hours, the battery reacts at a rate of C / 50 relative to Li / Li. + Cycle between 1.9V and 3.0V, and cycle 4 times each at the following temperatures: room temperature, 45°C, 75°C, and 105°C.

[0155] like Figure 5 As shown, irreversibility was observed only in the first cycle (likely due to byproduct formation at the solid electrolyte-electrode interface), and this phenomenon was observed in all first cycles at all test temperatures. Overvoltage was measured at a potential plateau of approximately 2.4V, and its value was:

[0156] -Room temperature: 196mV

[0157] -45℃: 135mV.

[0158] -75℃: 100mV.

[0159] -105℃: 61mV.

[0160] The overvoltage decreases with increasing temperature. Regardless of the aforementioned temperature conditions, it does not exceed 200 mV. Furthermore, after 16 cycles, the observed capacity retention remains above 90%. Therefore, reversible cycling is demonstrated and shows a preference for increasing temperature, as evidenced by the small polarization (i.e., overpotential).

[0161] Example 8: Electrochemical Characterization 1 – Constant Current Cycling to Test Operating Voltage Range of Commercially Available Li-Active Oxides Electrochemical stability of Li-active sulfides LTFS

[0162] In this example, the constant current cycling is performed in two steps within the operating voltage range to test:

[0163] - Electrochemical stability of LTFS alone combined with solid electrolyte β-Li3PS4 (tested in battery A); and

[0164] - Electrochemical stability of LTFS mixed with solid electrolyte β-Li3PS4 and commercial oxide (test battery B).

[0165] For this purpose, two solid-state batteries were assembled according to the same procedure for battery assembly described in Example 5.

[0166] Electrochemical analysis was performed in an Ar-filled glove box (O2 and H2O content <1ppm) using a Bioroger (Seyssinet-Pariset, France) VMP-3 potentiostat / galvanostat model.

[0167] Test battery A

[0168] This battery was tested to demonstrate the electrochemical stability and suitability of the selected sulfide material itself at the operating voltage of the oxide material. Details of each component of this type of battery, already described in Example 5, are as follows.

[0169] - Positive electrode composite material: LTFS-β-Li3PS4 composite material (70:30 by weight)

[0170] - Solid electrolyte: β-Li3PS4

[0171] - Negative electrode: Li-In alloy (indium on a copper disk).

[0172] After being left to stand open for 5 hours, this battery was cycled at room temperature at a rate of C / 50 relative to Li / Li. + Cycle within a voltage window of 1.9V to 4.3V.

[0173] like Figure 6 As shown, apart from the irreversibility of the first cycle mentioned above, no specific capacity (mAh·g) was observed. -1 Significant changes in the potential (relative to Li / Li) were observed, and the curve shape remained stable. Specifically, at the upper limit potential (relative to Li / Li), + Capacity at approximately 4.3V (~200mAh·g) -1 It remained stable after 3 cycles.

[0174] This result demonstrates that LTFS can withstand the voltage window of commercially available oxide NMC 622.

[0175] Test battery B

[0176] This battery was tested to demonstrate the electrochemical stability of the selected Li-active sulfide LTFS at the operating voltage of the Li-active layered oxide in the presence of the oxide. The selected Li-active oxide was LiNi. 0.6 Mn 0.2 Co 0.2 O2(NMC622).

[0177] Details of each component of this type of battery, which has already been described in Example 5, are as follows:

[0178] - Positive electrode composite material: NMC 622–LTFS (1:1 weight ratio) and β-Li3PS4 were mixed by hand grinding at a weight ratio of 70:30 (70% NMC 622 / LTFS mixture, 30% β-Li3PS4);

[0179] - Solid electrolyte: β-Li3PS4;

[0180] - Negative electrode: Li-In alloy (indium on a copper disk).

[0181] After being left to stand open for 5 hours, this battery cycles at room temperature at a rate of C / 50 and relative to Li / Li + Cycling within a voltage window from 1.9V to 4.3V.

[0182] refer to Figure 7 The potential-to-capacity plot shows two regions. In relation to Li / Li + Between 1.9 and 2.5 V, LTFS is electrochemically active, while NMC 622 is electrochemically active relative to Li / Li + It is active in the range of 3 to 4.3 V. Good reversibility of the materials (LTFS and NMC) used as part of the electrodes of the test battery B was observed in two significantly different potential ranges.

[0183] Figure 8 The specific capacity evolution of test battery B after 10 cycles in a delithiation state is shown. However, due to the irreversibility between the first and second cycles, the capacity remains stable at 125 mAh·g. -1 The specific capacity evolution of test battery B after 10 cycles in a delithiation state is shown.

[0184] These results indicate that when mixed with commercially available Li-active oxides, Li-active sulfides LTFS are electrochemically stable over the operating voltage range of the oxides.

[0185] Example 9: Electrochemical characterization 2 - Commercially available Li-active oxides mixed with Li-active sulfides LTFS are superior to those without. Oxides with LTFS

[0186] Two solid-state batteries were constructed, one without LTFS in the positive electrode material (validation battery A), and the other with a mixture of Li-active oxide and Li-active sulfide (LTFS) materials as the positive electrode (validation battery B). In both cases, electrochemical tests were performed at the operating voltage of the oxide NMC 622, i.e., relative to Li / Li + The voltage range is 2.6 to 4.3V.

[0187] Details of each component of this type of battery, which has already been described in Example 5, are as follows:

[0188] Verified battery A without LTFS

[0189] - Positive electrode composite material: NMC 622 and β-Li3PS4 were mixed by hand grinding at a weight ratio of 70:30 (70% NMC 622, 30% β-Li3PS4).

[0190] - Solid electrolyte: β-Li3PS4

[0191] - Negative electrode: Li-In alloy (indium on a copper disk).

[0192] Verify battery B

[0193] - Positive electrode composite material: NMC 622–LTFS (9:1 weight ratio) and β-Li3PS4 were mixed by hand milling at a weight ratio of 70:30 (70% NMC 622 / LTFS mixture, 30% β-Li3PS4).

[0194] - Solid electrolyte: β-Li3PS4

[0195] - Negative electrode: Li-In alloy (indium on a copper disk).

[0196] After being left to stand for 5 hours in an open circuit, the mixture was circulated at room temperature at a rate of C / 50 and relative to Li / Li + Within a voltage window of 2.1 to 4.3V, two batteries, verification A and verification B, were tested, with each test performed 5 cycles. Figure 9 The NMC 622 / LTFS 9:1 mixture (verification battery B) is shown to have a reversible capacity (verification battery B is 111 mAh·g). -1 The battery A was verified to have a capacity of 71 mAh·g. -1 The battery exhibits improved cycle performance in terms of overvoltage (polarization at 130 mAh / g: 180 mV for verification battery B and 300 mV for verification battery A). The beneficial effects of LTFS are thus demonstrated.

[0197] Example 10: Electrochemical Characterization 3 - Electrochemical Impedance Spectroscopy (EIS)

[0198] Verification batteries A and B were used for electrochemical impedance spectroscopy (EIS). EIS measurements involve exciting an electrochemical system with a sinusoidal electrical signal around a fixed value (i.e., a fixed potential or current). By detecting the system's response to this sinusoidal signal, the impedance evolution (Z = V / I, in complex units) can be observed. Higher impedance indicates greater interfacial resistance. Another advantage of this technique is that it allows for the differentiation of phenomena occurring within the electrochemical cell across a wide frequency range. Furthermore, EIS can be considered non-destructive for low-amplitude signals.

[0199] In this example, the excitation signal amplitude was chosen to be 10 mV in potential mode. To avoid evolution of the electrochemical system during measurement, EIS spectra were obtained in the frequency range of 100 kHz to 100 MHz to probe the cathode-solid-electrolyte interface at the end of the first charge at a C / 50 rate (16 points per decathode) (in the delithiated state). Measurements were performed after a 15-minute relaxation period, and the OCV of battery A (NMC) was verified to be approximately 3.9 V, and the OCV of battery B (NMC / LTFS) was verified to be approximately 4.1 V. Figure 10 The evolution of impedance Z in the Nyquist plan (-Im(Z) vs. Re(Z)) is shown. The semicircles represent contributions from different regions of the electrochemical cell according to the frequency range.

[0200] For example,

[0201] - In the mid-frequency range (frequency range of 100mHz to 100kHz): Phenomena occurring at the interface between the solid electrolyte and the positive electrode.

[0202] - At lower frequency ranges (below 100 mHz): Phenomena observed at the interface between the solid electrolyte and the negative electrode (not shown)

[0203] - In the higher frequency range (above 100 kHz): Phenomena occurring near the electrolyte (not shown) (see Zhang et al.).

[0204] Figure 10 The curves shown correspond to the mid-frequency range and therefore to the interface between the solid electrolyte and the positive electrode composite material. The results clearly show that the curve radius and shape of verification battery B are smaller than those of verification battery A, indicating a lower cathode / SE interface resistance in verification battery B. These results are consistent with the galvanostatic measurements performed in Example 9.

[0205] References cited

[0206] 1. Janek, J. et al., A solid future for battery development. Natural Energy, 1, 16141 (2016).

[0207] 2. Kanno, R. et al., “Lithium Ionic Conductor Thio-LISICON: The Li2S-GeS2-P2S5 System”, Journal of Electrochem. Soc., 148, (2001).

[0208] 3. Kamaya, N. et al., “A lithium superionic conductor”, Nature Materials, 10, 682-686 (2011).

[0209] 4. Koerver, R. et al. Redox-active positive electrode interphases in solid-state batteries. Journal of Materials Chemistry A, 5, 22750–22760 (2017).

[0210] 5. Takada, K. et al., "Interfacial phenomenon in solid-state lithium battery with sulphide solid electrolyte", Solid State Ionics, 225, 594–597 (2012).

[0211] 6. Haruyama, J. et al., "Space-Charge Layer Effect at Interface between Oxide Positive Electrode and Solid Electrolyte in All-Solid-State Lithium-Ion Battery", Chem. Mater. 26, 4248-4255 (2014).

[0212] 7. Culver, SP et al., "On the Functionality of Coatings for Positive Electrode Active Materials in Thiophosphate-Based All-Solid-State Batteries." *Advanced Energy Materials* (2019). doi:10.1002 / aenm.201900626

[0213] 8. Xiao, Y, Miara, LJ, Wang, Y. & Ceder, G, "Computational Screening of Positive Electrode Coatings for Solid-State Batteries", Joule (2019). doi:10.1016 / JouleJournal2019.02.006

[0214] 9. Liu, Z. et al., “Anomalous high ionic conductivity of nanoporous β-Li3PS4”. Journal of the American Chemical Society (J. Am. Chem. Soc.) 135, 975–978 (2013).

[0215] 10. Busche, MR et al., "Fast Lithium-ion Conductor Li7P3S in Hot Pressing Devices" 11 In-situ monitoring of fast Li-Ion conductor Li7P3S crystallization 11 Crystallization Inside a Hot-Press Setup. Chemical Materials, 28, 6152–6165 (2016).

[0216] 11. Janek, J. et al., "Interfacial Processes and Influence of Composite Positive Electrode Microstructure Controlling the Performance of All-Solid-State Lithium Batteries." ACS Appl. Mater. Interfaces, 9, 17835–17845 (2017).

[0217] 12. Takada, K, et al., "Lithium iron sulfide as an electrode material in a solid state lithium battery." Solid State Ionics, Vol. 117, No. 3-4, February 2, 1999, Abstract.

Claims

1. One formula is Li 1.13 Ti 0.33 Fe 0.57 The use of S2 ternary transition metal sulfide compounds combined with oxide compounds as active materials for the positive electrode of solid-state batteries. The oxide mentioned is LiNi 0.6 Mn 0.2 Co 0.2 O2, LiNiMnO2, or mixtures thereof.

2. A compound containing Li, which is ultimately mixed with an electrolyte material. 1.13 Ti 0.33 Fe 0.57 S2 is a composite material of ternary transition metal sulfide compounds and oxide compounds. The oxide mentioned is LiNi 0.6 Mn 0.2 Co 0.2 O2, LiNiMnO2, or mixtures thereof.

3. The composite material of claim 2, wherein the electrolyte material is in the form of powder or compacted powder.

4. An electrochemical cell comprising at least a positive electrode and a negative electrode in contact with an electrolyte material, wherein the positive electrode comprises, according to claim 2, a material containing the formula Li. 1.13 Ti 0.33 Fe 0.57 S2 is a composite material of ternary transition metal sulfide compounds and oxide compounds.

5. A solid-state battery comprising at least one electrochemical cell according to claim 4 and an external connector.

6. The solid-state battery according to claim 5, wherein the battery is a solid-state lithium battery.

7. The solid-state battery of claim 6, wherein the battery is capable of cycling within an allowable cutoff voltage range of 1.5 to 4.5 V relative to Li / Li+.

8. The solid-state battery of claim 7, wherein the battery is capable of cycling within an allowable cutoff voltage range of 1.9 to 4.3 V relative to Li / Li+.

9. The solid-state battery of claim 7, wherein the battery is capable of cycling within an allowable cutoff voltage range of 2 to 4 V relative to Li / Li+.

10. One formula is Li 1.13 Ti 0.33 Fe 0.57 The use of S2 ternary transition metal sulfide compounds as positive electrode active materials for solid-state batteries.

11. The use according to claim 10, wherein the use comprises mixing the ternary transition metal sulfide compound in powder form with a solid electrolyte material, also in powder form.

12. A positive electrode for a solid-state battery, the electrode comprising the formula Li 1.13 Ti 0.33 Fe 0.57 S2 is a ternary transition metal sulfide and ultimately comprises a solid electrolyte material.

13. An electrochemical cell comprising at least one positive electrode and a negative electrode in contact with an electrolyte material, wherein the positive electrode is as described in claim 12.

14. A solid-state battery comprising at least one electrochemical cell according to claim 13 and an external connector.

15. The solid-state battery of claim 14, wherein the battery comprises one or more of the batteries.

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