Positive electrode material

Abstract

The present invention provides an oxide-based positive electrode material containing lithium, oxygen, sulfur, and at least one kind of transition metal as main constituents, the material containing (i) sulfate ions, (ii) Li2O, and (iii) an amorphous phase.

Description

Positive electrode material

[0001] The present disclosure relates to a positive electrode material.

[0002] As a positive electrode material for a lithium secondary battery or an all-solid-state lithium secondary battery, an amorphous positive electrode active material (LiMO ２ -Li ２ MnO ３ -Li ２ SO ４ ) to which a low-melting oxide is added is known (Patent Document 1).

[0003] International Publication No. 2017 / 169599

[0004] An object of the present disclosure is to provide a novel positive electrode material having excellent positive electrode characteristics.

[0005] The present disclosure includes the following aspects. [Item 1] An oxide-based positive electrode material containing lithium, oxygen, sulfur, and at least one transition metal as main constituent components, (i) containing sulfate ions, (ii) containing Li ２ O, (iii) containing an amorphous phase, Positive electrode material. [Item 2] The following formulas (a) and (b): (a) [S] / [M]≧0.1 (b) [Li]−2[S]−w>[M] [In the formula: [S] is the molar fraction of sulfur atoms in the positive electrode material, [M] is the molar fraction of transition metal atoms in the positive electrode material, [Li] is the molar fraction of lithium atoms in the positive electrode material, w is the molar fraction of tetravalent transition metal atoms in the transition metal.] The positive electrode material according to Item 1, which satisfies the above. [Item 3] The positive electrode material according to Item 1 or 2, wherein the transition metal includes transition metals of the fourth period. [Item 4] The positive electrode material according to any one of Items 1 to 3, wherein the transition metal includes at least one of Ni and Mn. [Item 5] The positive electrode material according to any one of Items 1 to 4, wherein the transition metal includes Ni and Mn. [Item 6] The following formula: (100−y−z)(Li １＋０．５ｘ M １ １－１．５ｘ MnO ｘ O ２ )·yLi ２ O·zLi ２ SO ４ [In the formula: M１ A positive electrode material represented by [formula] is a transition metal, x is between 0 and 0.5, y is between 1 and 50, and z is between 10 and 20. [Item 7] M １ [Clause 8] A cathode material according to Clause 6, wherein x is Ni. [Clause 9] A cathode material according to Clause 1 to 8, which is a cathode active material. [Clause 10] A cathode composite comprising a cathode material according to any one of Clauses 1 to 9 and a solid electrolyte. [Clause 11] An all-solid-state battery comprising a cathode material according to Clauses 1 to 9 or a cathode composite according to Clause 10. [Clause 12] A method for producing a cathode material according to any one of Clauses 1 to 9, comprising amorphousizing a composite of a lithium-transition metal composite oxide, lithium sulfate, and lithium oxide. [Clause 13] The method for producing a cathode material according to Clause 12, wherein the amorphous method is a mechanochemical method. [Item 14] A method for producing an amorphous oxide cathode material in which lithium, oxygen, sulfur, and at least two types of transition metals are the main constituent components, and the transition metals are homogeneously dispersed on a scale of several tens of nanometers, comprising amorphousizing a mixture of lithium transition metal oxide crystals containing lithium and all of the above transition metals and lithium sulfate to obtain an amorphous oxide cathode material. [Item 15] A method for producing a cathode material, characterized in that the amorphous oxide cathode material obtained by amorphousizing treatment in the production method described in Item 14 is further heat-treated at 200 to 500°C to precipitate crystallites with a crystallite size of 50 nm or less to obtain an amorphous and nanocrystalline nanocomposite cathode material having a homogeneous composition on a scale of several tens of nanometers.

[0006] The positive electrode material in this disclosure exhibits excellent battery properties as a positive electrode active material.

[0007] Figure 1 shows the results of the charge-discharge tests for Examples 1-9 and Comparative Examples 1-3. Figure 2 shows the results of the charge-discharge tests for Examples 10-1 and Comparative Examples 4-5. Figure 3 shows the results of the charge-discharge test for Comparative Example 6.

[0008] <Positive Electrode Material> The positive electrode material of this disclosure exhibits excellent battery characteristics as a positive electrode active material. Specifically, the positive electrode material of this disclosure exhibits a large initial charge capacity and can also exhibit excellent initial discharge capacity and cycle discharge capacity retention rate.

[0009] The cathode material in this disclosure is an oxide-based cathode material comprising lithium, oxygen, sulfur, and at least one transition metal as major constituent components, and (i) contains sulfate ions, and (ii) Li ２ It contains O, and (iii) contains an amorphous phase as the main phase.

[0010] The cathode material of this disclosure exhibits excellent charge-discharge characteristics by satisfying the above conditions (i), (ii), and (iii).

[0011] The presence of sulfate ions in the cathode material of this disclosure can be determined by X-ray photoelectron spectroscopy (XPS) or heat treatment. ２ SO ４ The separation and crystallization of these materials can be confirmed, preferably by X-ray photoelectron spectroscopy (XPS). The inclusion of sulfate ions in the positive electrode material improves the charge-discharge characteristics of batteries using such a positive electrode material.

[0012] For convenience, Li ２ It says it contains O, but this is Li ２ This does not mean that it contains O crystals, and it may also be contained in an amorphous form or in the form of a compound with other transition metals, and furthermore, "Li ２ "Contains O" is typically "Li ２ This means "having a composition that contains an excess of O." "Containing an excess" means that, in general terms, the lithium content is higher than that of typical cathode materials. ２ It means that it contains a large amount of O.

[0013] The cathode material disclosed herein is Li ２ Including O, especially Li ２ The presence of an excess of oxygen in the composition can be confirmed by measuring the ratio of Li to the transition metal through compositional analysis such as ICP emission spectroscopy. ２ By including oxygen, the initial charge capacity of a battery using such a positive electrode material can be improved, and the initial discharge capacity can also be improved.

[0014] The cathode material of this disclosure includes an amorphous phase (amorphous layer). In addition to the amorphous phase, the cathode material may also include a crystalline phase. Preferably, the cathode material of this disclosure includes an amorphous layer as the main phase. By including an amorphous layer, the resistance of the cathode material can be reduced. Furthermore, because the amorphous layer has a lower density than the crystalline layer, the cathode material's ability to follow volume changes during charging and discharging is improved. As a result, the generation of irreversible capacitance, such as non-conductive areas due to powdering, can be suppressed. In this specification, "main phase" means the phase that is most abundant in the overall structure of the cathode material. The phase structure of the cathode material can be determined based on the peak integrated intensity of each phase in XRD analysis. For example, when the amorphous layer is the main phase, the crystal peak is small and a broad spectrum appears in XRD.

[0015] The cathode material of this disclosure is typically Li ２ O-LiMO ２ -Li ２ MnO ３ -Li ２ SO ４ Composition, in more detail Li ２ O-LiMO ２ -Li (Li １／３ Mn ２／３ ) O ２ -Li ２ SO ４ It has a composition. This composition can be measured by XRD analysis.

[0016] The positive electrode material of this disclosure satisfies the following formulas (a) and (b): (a) [S] / [M] ≥ 0.1 (b) [Li] - 2[S] - w > [M] [wherein: [S] is the mole fraction of sulfur atoms in the positive electrode material, [M] is the mole fraction of transition metal atoms in the positive electrode material, [Li] is the mole fraction of lithium atoms in the positive electrode material, and w is the mole fraction of tetravalent transition metal atoms in the transition metal.]

[0017] (a) [S] / [M] ≥ 0.1 In the cathode material of this disclosure, the ratio of the mole fraction of sulfur atoms to the mole fraction of transition metal atoms is 0.1 or greater. Typically, in the cathode material of this disclosure, sulfur atoms exist as sulfate ions or sulfite ions. That is, in the cathode material of this disclosure, Li is present in the ratio of the mole fraction of transition metal atoms ２ SO ４ and Li ２ SO ３ The total ratio may be 0.1 or more. [S] / [M] is preferably 0.15 or more, for example 0.2 or more or 0.25 or more. Also, [S] / [M] is preferably 0.8 or less, more preferably 0.5 or less, for example 0.4 or less or 0.3 or less. [S] / [M] is preferably 0.1 to 0.8 or less, more preferably 0.15 to 0.5 or less, for example 0.2 to 0.4 or 0.2 to 0.3 or less. By setting [S] / [M] within the above range, the battery characteristics are improved.

[0018] (b) [Li]-2[S]-w>[M] In the cathode material of this disclosure, the value obtained by subtracting twice the mole fraction of sulfur atoms and the mole fraction of tetravalent transition metal atoms in the transition metal from the mole fraction of lithium atoms is greater than the mole fraction of transition metal atoms. That is, it contains an excess of lithium atoms.

[0019] The above transition metals preferably include transition metals of the fourth period. The transition metals of the fourth period are Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, and Zn.

[0020] The above transition metal preferably comprises at least one of Ni and Mn, more preferably Ni, and more preferably Ni and Mn.

[0021] The tetravalent transition metal is Ti, V, Cr, and Mn, preferably Mn.

[0022] In another embodiment, the cathode material of the present disclosure is given by the following formula: (100 - y - z) (Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ )・yLi ２ O.zLi ２SO ４ [In the formula: M １ It is a transition metal, x is between 0 and 0.5, y is between 1 and 50, and z is between 10 and 20. It is represented as [ ].

[0023] M １ It is preferably a trivalent transition metal. Furthermore, M １ The transition metal is preferably a fourth-period transition metal, more preferably Ni.

[0024] x is preferably greater than 0, more preferably 0.01 or greater, more preferably 0.05 or greater, more preferably 0.10 or greater, for example, 0.15 or greater or 0.20 or greater. x is preferably 0.40 or less, more preferably 0.30 or less. x is preferably greater than 0 and less than or equal to 0.50, more preferably 0.10 or greater and less than or equal to 0.40, more preferably 0.15 or greater and less than or equal to 0.30.

[0025] y is preferably 5 or more, more preferably 5 or more, even more preferably 7 or more, for example 13 or more, 16 or more, 19 or more, 21 or more, or 24 or more. y is preferably 45 or less, more preferably 35 or less, even more preferably 30 or less, for example 25 or less, 22 or less, or 20 or less. y is preferably 5 or more and 45 or less, more preferably 7 or more and 35 or less, even more preferably 7 or more and 30 or less.

[0026] z is preferably 10 or more, more preferably 13 or more, even more preferably 14 or more, for example 15 or more or 16 or more. z is preferably 40 or less, more preferably 30 or less, for example 25 or less or 20 or less. z is preferably 10 or more and 40 or less, more preferably 13 or more and 30 or less, even more preferably 14 or more and 25 or less.

[0027] y / (100-y-z) is preferably 0.05 or more, preferably 0.10 or more, more preferably 0.20 or more, for example 0.25 or more, 0.30 or more, or 0.35 or more. y / (100-y-z) is preferably 0.90 or less, more preferably 0.70 or less, even more preferably 0.60 or less, even more preferably 0.50 or less, for example 0.45 or less, or 0.30 or less. y / (100-y-z) is preferably 0.05 or more and 0.90 or less, more preferably 0.05 or more and 0.70 or less, even more preferably 0.10 or more and 0.60 or even more preferably 0.10 or more and 0.50 or less, for example 0.10 or more and 0.40 or 0.20 or more and 0.40 or less.

[0028] z / (100-y-z) is preferably 0.05 or more, preferably 0.10 or more, more preferably 0.20 or more, for example 0.25 or more, 0.30 or more, or 0.35 or more. z / (100-y-z) is preferably 0.90 or less, more preferably 0.70 or less, even more preferably 0.50 or less, even more preferably 0.40 or less, for example 0.30 or less, or 0.25 or less. z / (100-y-z) is preferably 0.05 or more and 0.50 or less, more preferably 0.10 or more and 0.40 or less, even more preferably 0.15 or more and 0.35 or even more preferably 0.15 or more and 0.25 or less.

[0029] In a preferred embodiment, x is between 0.1 and 0.4, y is between 5 and 35, and z is between 10 and 19.

[0030] The cathode material of this disclosure is preferably used as a cathode active material.

[0031] <Method for manufacturing the cathode material> The cathode material of this disclosure can be manufactured, for example, by a method that includes amorphousizing a composite oxide containing lithium and a transition metal, lithium sulfate, and lithium oxide.

[0032] The above amorphous process is not particularly limited as long as it can produce amorphous material, but is preferably carried out by a method including a mechanochemical process.

[0033] A more specific manufacturing method of the positive electrode material of the present disclosure will be described in detail by taking a positive electrode material of the (Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ )·Li ２ O·Li ２ SO ４ system as an example.

[0034] First, prepare LiNiO ２ and Li ２ MnO ３ .

[0035] Next, mix LiNiO ２ and Li ２ MnO ３ at a predetermined ratio. The mixing method is not particularly limited, and for example, it can be mixed in a mortar.

[0036] Next, the mixture of LiNiO ２ and Li ２ MnO ３ obtained above is subjected to mechanochemical treatment to obtain a mechanochemical treatment product of Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ . This operation is effective in reducing the heat treatment temperature and time of the next operation, but it can be omitted.

[0037] The obtained Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ is heat-treated at a high temperature, for example, 800°C to 1000°C for 1 to 24 hours, pulverized, and further dried under reduced pressure at 100 to 150°C for 1 to 24 hours to obtain Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ crystal powder.

[0038] The obtained Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ crystal powder is mixed with Li ２SO ４ and Li ２ O are mixed. The mixing method is not particularly limited, and for example, they can be mixed in a mortar.

[0039] Next, the Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ crystalline powder, the mixture of Li ２ SO ４ and Li ２ O is subjected to mechanochemical treatment to obtain the amorphous oxide cathode material (Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ )·Li ２ O·Li ２ SO ４ of the present disclosure.

[0040] By the above mechanochemical treatment, the cathode material of the present disclosure may contain an amorphous phase as the main phase.

[0041] [[ID=​​​​​<Battery Components / Batteries> [Types of Batteries, etc.] The positive electrode material in this disclosure can be suitably used as a positive electrode active material for batteries, particularly lithium-ion batteries. When the positive electrode material in this disclosure is used as a positive electrode active material, the lithium-ion battery may be a battery using a liquid electrolyte, a semi-solid battery, or a solid-state battery, and is preferably a solid-state battery.

[0044] There are no particular restrictions on the shape of the battery; cylindrical, rectangular, etc., are acceptable.

[0045] [All-solid-state secondary battery] An all-solid-state secondary battery includes at least a positive electrode, a negative electrode, and a solid electrolyte layer located between the positive and negative electrodes.

[0046] [Positive Electrode] The positive electrode includes a positive electrode active material which is the positive electrode material of this disclosure. The positive electrode may optionally include other components such as positive electrode active materials other than the positive electrode material of this disclosure, electrolytes, conductive additives, and binders.

[0047] Examples of positive electrode active materials other than the positive electrode material of this disclosure include materials capable of intercalating or releasing lithium ions during charging and discharging, such as lithium cobalt oxide, lithium nickel oxide, lithium manganese oxide, ternary lithium metal oxides containing nickel, manganese, and cobalt, lithium iron phosphate, and materials in which a portion of the trivalent transition metals in the above are substituted with Al, and a specific example is LiCoO ２ LiNiO ２ LiMn ２ O ４ Li ａ Ni ｘ Mn ｙ Co ｚ O ２ LiFePO ４ These are some examples.

[0048] The amount of the positive electrode material (active material) of this disclosure in the active material of the positive electrode may be 10% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 60% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more, preferably 50% by weight or more, or 75% by weight or more, more preferably 85% by weight or more, and even more preferably 90% by weight or more. Furthermore, the amount of the positive electrode material of this disclosure in the positive electrode may be 100% by weight or less, 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, or 20% by weight or less.

[0049] The total amount of positive electrode active material in the positive electrode may be 10% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 60% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more in the case of a lithium-ion battery, preferably 50% by weight or more, or 75% by weight or more, more preferably 85% by weight or more, and even more preferably 90% by weight or more. Furthermore, the amount of positive electrode material of this disclosure in the positive electrode may be 100% by weight or less, 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, or 20% by weight or less. For example, in the case of an all-solid-state battery, the amount may be 10% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 60% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more, preferably 50% by weight or more, or 60% by weight or more, more preferably 70% by weight or more. Furthermore, the amount of the positive electrode material of this disclosure in the positive electrode may be 100% by weight or less, 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, or 20% by weight or less.

[0050] Examples of solid electrolytes other than the cathode material of this disclosure include the electrolyte in the electrolyte layer described later.

[0051] The amount of electrolyte in the positive electrode may be 0.1% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, or 60% by weight or more. Alternatively, the amount of electrolyte in the positive electrode may be 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less. Preferably, the amount of electrolyte in the positive electrode is 0.2 to 60% by weight, and more preferably 1 to 50% by weight.

[0052] Examples of conductive additives include carbon materials such as graphite, coke, carbon black, acicular carbon, carbon fibers, and carbon nanotubes.

[0053] The amount of conductive additive in the positive electrode may be 0.1% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, or 20% by weight or more. Alternatively, the amount of conductive additive in the positive electrode may be 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less. Preferably, the amount of conductive additive in the positive electrode is 0.2 to 10% by weight, and more preferably 1 to 6% by weight.

[0054] Examples of binders include polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polytetrafluoroethylene (PTFE), polyimide (PI), polyamide, polyamide-imide, polyacrylic, styrene-butadiene rubber (SBR), styrene-ethylene-butylene-styrene copolymer (SEBS), and carboxymethylcellulose (CMC).

[0055] The amount of binder in the positive electrode may be 0.1% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, or 20% by weight or more. Alternatively, the amount of binder in the positive electrode may be 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less. Preferably, the amount of binder in the positive electrode is 0.2 to 10% by weight, and more preferably 0.4 to 2% by weight.

[0056] The positive electrode containing the above components is connected to a positive electrode current collector made of Al, Ni, stainless steel, carbon cloth, or the like. The positive electrode may also be formed by coating the surface of the current collector with a slurry of the above components mixed with an inert solvent and drying it.

[0057] [Negative Electrode] The negative electrode is not particularly limited. The negative electrode may consist only of a negative electrode active material, or it may be mixed with a binder, conductive agent, electrolyte, etc. Possible negative electrode active materials include metals such as Li, Na, In, and Sn, Li alloys, Na alloys, graphite, hard carbon, Li ４／３ Ti ５／３ O ４ Na ３ V ２ (PO ４ ) ３ Examples include various transition metal oxides such as SnO. The negative electrode may also contain other components such as an electrolyte, conductive additive, and binder, as needed.

[0058] The amount of negative electrode active material in the negative electrode may be 10% by weight or more, 20% by weight or more, 30% by weight or more, 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, or 95% by weight or more, preferably 50% by weight or more, more preferably 70% by weight or more, and even more preferably 90% by weight or more. The amount of negative electrode active material in the negative electrode may be 100% by weight or less, 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, or 20% by weight or less.

[0059] An example of an electrolyte is the electrolyte in the electrolyte layer described later.

[0060] The amount of electrolyte in the negative electrode may be 0.5% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, or 40% by weight or more. The amount of electrolyte in the negative electrode may be 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, or 3% by weight or less.

[0061] Examples of conductive additives include carbon materials such as graphite, coke, carbon black, acicular carbon, carbon fibers, and carbon nanotubes.

[0062] The amount of conductive additive in the negative electrode may be 0.1% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, or 20% by weight or more. The amount of conductive additive in the negative electrode may be 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less. The amount of conductive additive in the negative electrode is preferably 0.2 to 10% by weight, and more preferably 0.4 to 2% by weight.

[0063] Examples of binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polyimide (PI), polyamide, polyamide-imide, polyacrylic, styrene-butadiene rubber (SBR), styrene-ethylene-butylene-styrene copolymer (SEBS), and carboxymethylcellulose (CMC).

[0064] The amount of binder in the negative electrode may be 0.1% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, or 20% by weight or more. The amount of binder in the negative electrode may be 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less. The amount of binder in the negative electrode is preferably 0.2 to 10% by weight, and more preferably 0.4 to 2% by weight.

[0065] The negative electrode containing the above components is connected to a negative electrode current collector made of Al, Ni, Cu, stainless steel, carbon cloth, or the like. The negative electrode may also be formed by coating the surface of the current collector with a slurry of the above components mixed with an inert solvent and drying it.

[0066] [Electrolyte Layer] The electrolyte layer contains an electrolyte. The electrolyte layer may also contain other components such as a binder, if necessary. In a battery, the electrolyte layer is positioned to connect the positive electrode and the negative electrode.

[0067] Electrolyte layers can be broadly classified into liquid electrolyte layers, which primarily use liquid electrolytes, and solid electrolyte layers, which primarily use solid electrolytes.

[0068] (Liquid Electrolyte Layer) The liquid electrolyte layer preferably consists of a mixture of an electrolyte salt and a non-aqueous solvent that dissolves and disperses it.

[0069] An example of an electrolyte salt in a liquid electrolyte layer is LiClO ４ LiPF ６ LiBF ４ LiCF ３ SO ３ LiAsF ６ LiB(C) ６ H ５ ) ４ , LiCl, LiBr, CH ３ SO ３ Li, CF ３ SO ３ Li, LiN(SO ２ CF ３ ) ２ , LiN (SO ２ C ２ F５ ) ２ , LiC (SO ２ CF ３ ) ３ or LiN(SO ３ CF ３ ) ２ These are some examples.

[0070] Examples of non-aqueous solvents include carbonates, ethers, ketones, sulfolane compounds, lactones, nitriles, chlorinated hydrocarbons, amines, esters, amides, and phosphate ester compounds. Representative examples of these include 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, ethylene carbonate, vinylene carbonate, methyl formate, dimethyl sulfoxide, propylene carbonate, acetonitrile, γ-butyrolactone, dimethylformamide, dimethyl carbonate, diethyl carbonate, sulfolane, ethyl methyl carbonate, 1,4-dioxane, 4-methyl-2-pentanone, 1,3-dioxolane, 4-methyl-1,3-dioxolane, diethyl ether, sulfolane, methylsulfolane, propionitrile, benzonitrile, butyronitrile, valeronitrile, 1,2-dichloroethane, trimethyl phosphate, and triethyl phosphate. These can be used individually or in combination of two or more types.

[0071] The amount of electrolyte salt in the liquid electrolyte layer may be 0.5% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, 20% by weight or more, 30% by weight or more, or 40% by weight or more. The amount of electrolyte salt in the liquid electrolyte layer may be 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, or 3% by weight or less.

[0072] The amount of non-aqueous solvent in the liquid electrolyte layer may be 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, or 90% by weight or more. The amount of non-aqueous solvent in the liquid electrolyte layer may be 95% by weight or less, 90% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, or 50% by weight or less.

[0073] The liquid electrolyte layer may include a separator to prevent short circuits between the positive and negative electrodes. The separator can be made of materials such as polyethylene, polypropylene, or other polyolefin resins; fluororesins such as polyvinylidene fluoride; nylon; cellulose acetate; nitrocellulose; polysulfone; polyacrylonitrile; aromatic aramid; or inorganic glass. The material may be in the form of a porous membrane, nonwoven fabric, or woven fabric.

[0074] (Solid Electrolyte Layer) The solid electrolyte constituting the solid electrolyte layer is not particularly limited, and any solid electrolyte that can be used in an all-solid-state secondary battery can be used. The solid electrolyte can be composed of, for example, a sulfide-based solid electrolyte, an oxide-based solid electrolyte, or a halide-based solid electrolyte.

[0075] Examples of sulfide-based solid electrolytes include Li ２ S-P ２ S ５ Li ２ S-P ２ S ５ -LiI, Li ２ S-P ２ S ５ -LiI-LiBr, Li ２ S-P ２ S ５ -Li ２ O, Li ２ S-P ２ S ５ -Li ２ O-LiI, Li ２ S-SiS ２ Li ２ S-SiS ２ -LiI, Li ２ S-SiS ２ - LiBr, Li ２ S-SiS ２ -LiCl, Li ２ S-SiS２ -B ２ S ３ -LiI, Li ２ S-SiS ２ -P ２ S ５ -LiI, Li ２ S-B ２ S ３ Li ２ S-P ２ S ５ -GeS ２ LiI-Li ２ S-P ２ O ５ LiI-Li ３ PO ４ -P ２ S ５ Li ２ S-P ２ S ５ Li １０ GeP ２ S １２ Li ９．５４ Si １．７４ P １．４４ S １１．７ Cl ０．３ Li ７ P ３ S １１ Li ３ PS ４ Li ３．２５ P ０．７５ S ４ Li ６ PS ５ I, Li ６＋ｙ PS ５－ｙ Z １＋ｙ Examples include (Z = Cl or Br, y = 0 to 0.5). These sulfide-based solid electrolytes may be used individually or in combination of two or more types.

[0076] Examples of oxide-based solid electrolyte materials include, for example, Li ２ O-B ２ O ３ -P ２ O ３ Li ２ O-SiO ２ Li ２ O-P ２ O ５ Li ２ O-B２ O ３ -SiO ２ Li ５ La ３ Ta ２ O １２ Li ７ La ３ Zr ２ O １２ Li ６ BaLa ２ Ta ２ O １２ Li ３．６ Si ０．６ P ０．４ O ４ or Li ３ BO ３ -Li ２ SO ４ -Li ２ CO ３ These are some examples. These oxide-based solid electrolytes may be used individually or in combination of two or more types.

[0077] Examples of halide-based solid electrolytes include, for example, Li ６ YCl ６ Li ３ YBr ６ These are some examples.

[0078] Of the above, sulfide-based solid electrolytes are preferred, Li ６＋ｙ PS ５－ｙ Z １＋ｙ It is more preferable that the electrolyte is an argyrodite-type sulfide solid electrolyte such as (Z = Cl or Br, y = 0 to 0.5).

[0079] The amount of electrolyte in the solid electrolyte layer may be 40% by weight or more, 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 97.5% by weight or more, preferably 80% by weight or more, more preferably 95% by weight or more. The amount of electrolyte in the solid electrolyte layer may be 100% by weight or less, 95% by weight or less, 90% by weight or less, 85% by weight or less, 80% by weight or less, 70% by weight or less, 60% by weight or less, 50% by weight or less, 40% by weight or less, 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, or 3% by weight or less. The amount of electrolyte in the solid electrolyte layer is preferably 80 to 100% by weight, more preferably 95 to 100% by weight.

[0080] The electrolyte layer may contain other components besides the electrolyte material mentioned above, such as binders. Examples of binders include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), poly(vinylidene fluoride-co-hexafluoropropylene) (PVDF-HFP), polyimide (PI), polyamide, polyamide-imide, polyacrylic, styrene-butadiene rubber (SBR), styrene-ethylene-butylene-styrene copolymer (SEBS), and carboxymethylcellulose (CMC).

[0081] The amount of binder in the solid electrolyte layer may be 0.1% by weight or more, 0.3% by weight or more, 0.4% by weight or more, 0.5% by weight or more, 1% by weight or more, 3% by weight or more, 5% by weight or more, 10% by weight or more, or 20% by weight or more. The amount of binder in the solid electrolyte layer may be 30% by weight or less, 20% by weight or less, 10% by weight or less, 5% by weight or less, 3% by weight or less, 2% by weight or less, 1% by weight or less, or 0.5% by weight or less. The amount of binder in the solid electrolyte layer is preferably 0.2 to 10% by weight, and more preferably 0.4 to 2% by weight or less.

[0082] The solid electrolyte layer can be obtained by pressing the solid electrolyte to a predetermined thickness. The pressing pressure may be between 50 and 2000 MPa.

[0083] [Method for Manufacturing Batteries] (Liquid Electrolyte Batteries) When manufacturing batteries using a liquid electrolyte, for example, a sodium-ion battery or secondary battery can be obtained by inserting a laminate of a positive electrode, a separator, and a negative electrode into a battery case and pouring a mixture of the electrolyte and a non-aqueous solvent into the battery case. The positive electrode, separator, and negative electrode may be laminated or in a wound shape.

[0084] (All-Solid-State Battery) When manufacturing an all-solid-state battery, a cell is obtained by stacking a positive electrode, a solid electrolyte layer, a negative electrode, and a current collector, and then pressing them together. The thickness of each layer may be independently 0.1 μm or more, 1 μm or more, 10 μm or more, 100 μm or more, or 1000 μm or more. The thickness of each layer may be independently 50000 μm or less, 30000 μm or less, 10000 μm or less, 5000 μm or less, 1000 μm or less, 500 μm or less, 300 μm or less, or 100 μm or less. The thickness of each layer is independently preferably 1 to 1000 μm, more preferably 1 to 100 μm. The obtained cell is fixed to a housing as needed.

[0085] Although embodiments have been described above, it should be understood that various modifications to the form and details are possible without departing from the spirit and scope of the claims.

[0086] The present disclosure will be explained in detail below with reference to examples, but the present disclosure is not limited to these examples. <Experimental Method> Since we are mainly dealing with atmospherically unstable materials, the experiments are conducted in a glove box under a dry argon atmosphere unless otherwise specified below.

[0087] Examples 1-9 and Comparative Examples 1-3 [Production of Cathode Active Material] LiNiO ２ and Li ２ MnO ３ The two components were mixed in a mortar at a molar ratio of 75:25, and mechanochemical (MC) treatment was performed by ball milling using a Fritsch P-7 planetary ball mill under the following conditions, resulting in 75LiNiO ２ ・25Li ２ MnO ３ (mol%) (=Li １．１１ Ni ０．６７ Mn ０．２２O ２ A MC-treated powder of the following composition was prepared. It was then heat-treated at 900°C in air for 10 hours, ground using a mortar and pestle, and dried under reduced pressure at 120°C overnight to obtain Li １．１１ Ni ０．６７ Mn ０．２２ O ２ Crystal powder was obtained. １．１１ Ni ０．６７ Mn ０．２２ O ２ The crystalline powder was mixed with Li in a predetermined molar ratio in a glove box under an Ar atmosphere. ２ SO ４ and Li ２ O is mixed in a mortar and pestle, and ball milling is performed under the following conditions to obtain the samples (Li) of Examples 1 to 9 and Comparative Examples 1 to 3. １．１１ Ni ０．６７ Mn ０．２２ O ２ )-Li ２ O-Li ２ SO ４ The following was synthesized. The composition of each preparation is shown in the table below. Note that Li ２ O was calcined at 1000°C to achieve high purity. Li ２ SO ４ Li ２ SO ４ ・H ２ O was dehydrated by heating it at 300°C for 3 hours in an Ar atmosphere. XRD patterns were obtained from the resulting cathode material, confirming the presence of an amorphous phase. —Mechanochemical conditions— Rotation speed: 370 rpm Processing time: 50 hours Sample amount: 0.5 g ZrO ２ Pot: 45 mL ZrO ２ (YSZ) Ball (5mm diameter): 40g

[0088]

[0089] Apply the above Example 1 and Comparative Example 1 to the following formulas: (a) [S] / [M]≧0.1 (b) [Li]-2[S]-w>[M] (1) Comparative Example 1 [S]=20 [M]=(100-y-z)(1-1.5x+x))=80×0.89=71.2 [Li]=80×1.11+2×20=128.8 w=0.22 ・For formula (a), [S] / [M]=20 / 71.2=0.28>0.1 ・For formula (b), Left side=128.8-2×20-80×0.22=71.2 Right side=71.2 Left side=Right sideTherefore, formula (b) is not satisfied. (2) Example 1 [S] = 18.5 [M] = 74.1 × (0.67 + 0.22) = 65,949 [Li] = [74.1 × 1.11 + 7.4 × 2 + 18.5 × 2] = 134.05 w = 74.1 × 0.22 = 16.302 ・For equation (a), [S] / [M] = 18.5 / 65.949 = 0.28 > 0.1 ・For equation (b), Left side = 134.05 - 37 - 16.302 = 80.748 Right side = 65.949 Left side > Right side Therefore, both equations (a) and (b) are satisfied.

[0090] [Method for manufacturing all-solid-state batteries] The positive electrode materials of Examples 1 to 9 and Comparative Example 1 were used as positive electrode active materials. Li ６－ｘ PS ５－ｘ Cl １＋ｘ A solid electrolyte was used, and VGCF (manufactured by Showa Denko) was used as a conductive additive. The positive electrode active material, solid electrolyte, and conductive additive were mixed in a weight ratio of 83.4:15.5:1.1 to form the positive electrode composite. Li-In foil was used as the negative electrode. 120 mg of the solid electrolyte was weighed onto a 10 mm diameter stainless steel current collector surrounded on the sides by a polycarbonate cylinder, and the solid electrolyte was molded by pressing at 36 MPa. 10 mg of the positive electrode composite was weighed onto the molded solid electrolyte and densified by pressing at 180 MPa for 1 minute. After placing the negative electrode on the solid electrolyte opposite the positive electrode layer, the stainless steel current collector was placed on top and densified by pressing at 360 MPa for 5 minutes. Finally, it was restrained from above and below to form an all-solid-state battery.

[0091] [Charge / Discharge Test] The fabricated all-solid-state battery was subjected to a charge / discharge test at 25°C. In the charge / discharge test, the voltage range was 1.4 to 4.0 (vs Li-In), and the current density was 0.13 mAcm². －２ The stopping time was set to 15 minutes. The results are shown in Table 1 and Figure 1.

[0092]

[0093] From the above results, Li ２ It was confirmed that increasing the amount of O added increases the initial charge capacity. Also, Li ２ It was confirmed that the initial irreversible capacity increases when the amount of O added is 30% or more. This characteristic is useful in combination with negative electrodes that have a very large irreversible capacity or negative electrodes that enable high-performance charging and discharging in a composition range containing a lot of Li. Furthermore, Li ２ It was confirmed that the initial discharge capacity also increases when the amount of O added is 50% or less. ２ It was confirmed that the discharge capacity maintenance rate is high when the amount of oxygen added is 60% or less.

[0094] Examples 10-11 and Comparative Examples 4-5: All-solid-state batteries were prepared in the same manner as in Example 1, except that positive electrode materials having the respective compositional compositions shown in the table below were used as the positive electrode active material, and charge-discharge tests were performed. The results are shown in Figure 2.

[0095]

[0096] Based on the above results, Li ２ Examples 10 and 11, in which O was added, ２ It was confirmed that a larger charge / discharge capacity was obtained compared to Comparative Examples 4 and 5, which did not contain added oxygen.

[0097] Comparative Example 6: As the positive electrode active material, 77(Li １．１１ Ni ０．６７ Mn ０．２２ O ２ )・23Li ２ An all-solid-state battery was fabricated in the same manner as in Example 1, except that a positive electrode material having an O composition was used, and a charge-discharge test was performed. The results are shown in Figure 3.

[0098] From the above results, Li２ It was confirmed that even when oxygen is added, excellent properties cannot be obtained without adding Li2SO4.

[0099] Reference example 1 LiNiO ２ and Li ２ MnO ３ The two were mixed in a weight ratio of 75:25 and subjected to mechanochemical treatment. Then, it was heat-treated at 900°C for 10 hours, crushed, heated under reduced pressure at 120°C overnight, and Li １．１１ Ni ０．６７ Mn ０．２２ O ２ A crystalline powder of Li was obtained. Next, Li ２ SO ４ The mixture is subjected to mechanochemical treatment and heat-treated at 300°C for 1 hour, resulting in 80 (Li １．１１ Ni ０．６７ Mn ０．２２ O ２ )・20Li ２ SO ４ I obtained it.

[0100] Reference comparative example 1 LiNiO ２ Li ２ MnO ３ and Li ２ SO ４ The mixture was combined in a weight ratio of 60:20:20 and subjected to mechanochemical treatment. Subsequently, it was heat-treated at 300°C for 1 hour, resulting in 60LiNiO ２ ・20Li ２ MnO ３ ・20Li ２ SO ４ (Reference example 1 80 (Li １．１１ Ni ０．６７ Mn ０．２２ O ２ )・20Li ２ SO ４ (It has the same composition as) was obtained.

[0101] - Mechanochemical conditions - Rotation speed: 370 rpm Processing time: 50 hours Sample amount: 0.5 g ZrO ２ Pot: 45 mL Zr (YSZ) ball (5 mm diameter): 40 g

[0102] The samples obtained in Reference Example 1 and Reference Comparative Example 1 were observed using CP-SEM and EDS measurements were performed. Li ２ SO ４ In Reference Comparative Example 1, where Li was added from the beginning, Ni-rich regions of about 10-100 nm (white dots in the secondary electron image SE(L)) were observed. Separately, elemental mapping analysis using a transmission electron microscope (TEM-EELS) was performed, and the area ratio (= volume fraction) of white dots with a diameter of 20 nm or more was found to be approximately 11%. On the other hand, Li １．１１ Ni ０．６７ Mn ０．２２ O ２ Prepare a crystalline powder of Li ２ SO ４ In Reference Example 1, which included the addition of the above, the regions with different contrasts within the particles were minimal in the secondary electron image. Separately, identification using TEM-EELS confirmed that the Ni aggregation region had been significantly reduced.

[0103] The positive electrode material of this disclosure can be suitably used in solid-state batteries.

Claims

An oxide-based cathode material comprising lithium, oxygen, sulfur, and at least one transition metal as major constituent components, (i) containing sulfate ions, (ii) Li ２ Including O, (iii) containing amorphous phase, Cathode material. 　 The following equations (a) and (b): (a) [S] / [M]≧0.1 (b) [Li]-2[S]-w>[M] [In the formula: [S] is the mole fraction of sulfur atoms in the positive electrode material. [M] is the mole fraction of transition metal atoms in the positive electrode material. [Li] is the mole fraction of lithium atoms in the positive electrode material. w is the mole fraction of tetravalent transition metal atoms in the transition metal. A positive electrode material according to claim 1, satisfying the requirements. 　 The cathode material according to claim 1, wherein the transition metal includes a transition metal of the fourth period. 　 The cathode material according to claim 1, wherein the transition metal comprises at least one of Ni and Mn. 　 The cathode material according to claim 1, wherein the transition metal comprises Ni and Mn. 　 The following formula: (100-y-z)(Li １＋０．５ｘ M １ １－１．５ｘ Mn ｘ O ２ )・yLi ２ O・zLi ２ SO ４ [In the formula: M １ It is a transition metal, x is between 0 and 0.5, y is between 1 and 50, z is between 10 and 20 (inclusive). A positive electrode material represented by [this symbol]. M １ The positive electrode material according to claim 6, wherein is Ni. x is between 0.1 and 0.4, y is between 7 and 45, z is between 10 and 19. The positive electrode material according to claim 6. 　 The positive electrode material according to claim 1, which is a positive electrode active material. 　 A cathode composite comprising the cathode material and solid electrolyte according to any one of claims 1 to 9. 　 A solid-state battery comprising the positive electrode material described in claims 1 to 9 or the positive electrode composite described in claim 10. 　 A method for producing a cathode material according to any one of claims 1 to 9, comprising amorphousizing a composite oxide containing lithium and a transition metal, lithium sulfate, and lithium oxide. 　 The manufacturing method according to claim 12, wherein the amorphization method is a mechanochemical method. 　 A method for producing an amorphous oxide cathode material in which lithium, oxygen, sulfur, and at least two transition metals are the main constituent components, and the transition metals are homogeneously dispersed on a scale of several tens of nanometers, comprising amorphous treatment of a mixture of lithium transition metal oxide crystals containing lithium and all of the above transition metals and lithium sulfate to obtain an amorphous oxide cathode material. 　 A method for producing a cathode material, characterized in that the amorphous oxide cathode material obtained by the production method described in claim 14 is further heat-treated at 200 to 500°C to precipitate crystallites with a crystallite size of 50 nm or less, thereby obtaining an amorphous and nanocrystalline nanocomposite cathode material having a homogeneous composition on the scale of tens of nanometers.

Images