Covering active material, method for producing covering active material, positive electrode material, and battery

Abstract

A coated active material (100) according to the present disclosure is provided with a positive electrode active material (11), lithium carbonate present on the surface of the positive electrode active material (11), and a coating layer (12) that covers at least a portion of the surface of the positive electrode active material (11), the coating layer (12) containing a lithium-containing fluoride, and when the mass of the lithium carbonate present on the surface of the positive electrode active material (11) is measured by neutralization titration, the mass of the lithium carbonate is less than the mass of the lithium carbonate present on the surface of the positive electrode active material (11). The ratio (R1) of the mass of the lithium carbonate to the mass of the positive electrode active material (11) is from 0.43% to 1.4% (inclusive).

Description

Technical Field

[0001] This disclosure relates to active materials, methods for manufacturing active materials, cathode materials, and batteries. Background Technology

[0002] Patent Document 1 discloses a positive electrode material comprising a positive electrode active material and a halide solid electrolyte. In Patent Document 1, as a halide solid electrolyte, a solid electrolyte comprising lithium, yttrium, and at least one selected from chlorine, bromine, and iodine is disclosed.

[0003] Existing technical documents Patent documents Patent Document 1: International Publication No. 2019 / 135322 Patent Document 2: International Publication No. 2021 / 187391 Patent Document 3: International Publication No. 2023 / 037776 Summary of the Invention

[0004] The problem that the invention aims to solve This disclosure provides a covering active material that can reduce the internal resistance of a battery.

[0005] Methods for solving problems One aspect of this disclosure relates to a covering active substance, which comprises: Positive electrode active material, Lithium carbonate, which is present on the surface of the positive electrode active material, and A capping layer that covers at least a portion of the surface of the positive electrode active material; The coating layer contains lithium fluoride. When the mass of the lithium carbonate is determined by neutralization titration, the ratio R1 of the mass of the lithium carbonate to the mass of the positive electrode active material is 0.43% or more and 1.4% or less.

[0006] Invention Effects According to this disclosure, the internal resistance of the battery can be reduced. Attached Figure Description

[0007] Figure 1 This is a cross-sectional view showing the general structure of the covering active substance 100 in Embodiment 1.

[0008] Figure 2 This is a flowchart illustrating the manufacturing method of covering the active substance 100.

[0009] Figure 3 It is LiNi that has not undergone carbonic acid annealing treatment. 0.8 Co 0.15 Al0.05 O2 is obtained by TG-MS determination of water ion chromatogram.

[0010] Figure 4 This is a cross-sectional view showing the general structure of the positive electrode material 200 in Embodiment 2.

[0011] Figure 5 This is a cross-sectional view showing the general configuration of the battery 300 in Embodiment 3. Detailed Implementation

[0012] (The insights that form the basis of this disclosure) Patent document 1 describes a positive electrode material comprising a positive electrode active material and a halide solid electrolyte, wherein the halide solid electrolyte comprises lithium, yttrium and at least one selected from chlorine, bromine and iodine.

[0013] However, in batteries using halide solid electrolytes as cathode materials, the halide solid electrolytes undergo oxidative decomposition during charging. The products of this oxidative decomposition function as a resistive layer, causing an increase in the battery's internal resistance during charging. It can be inferred that the increase in the battery's internal resistance during charging is due to the oxidation reaction of at least one element selected from chlorine, bromine, and iodine contained in the halide solid electrolyte. Therefore, the oxidation resistance of halide solid electrolytes presents a challenge.

[0014] Patent document 2 describes a battery using a positive electrode active material covered with a material containing lithium fluoride, which exhibits excellent oxidation resistance. Such a positive electrode active material can suppress the increase in the battery's internal resistance during charging. The detailed mechanism is not yet clear, but it can be speculated as follows: Fluorine has the highest electronegativity among the halogens. Therefore, fluorine is strongly bonded to cations. Consequently, in lithium fluoride, the oxidation reaction of fluorine, i.e., the side reaction that removes electrons from fluorine, is difficult to occur. As a result, it is difficult to form a resistive layer through oxidative decomposition.

[0015] On the other hand, the inventors studied the resistance of batteries using positive electrode active materials covered with materials containing lithium fluorides. As a result, a problem of high output resistance during discharge was discovered. The detailed mechanism is not yet clear, but it can be speculated as follows: When the positive electrode active material is covered with a material containing lithium fluorides, the lithium-containing alkaline component present on the surface of the positive electrode active material reacts with the lithium fluoride, sometimes causing a portion of the lithium fluoride-containing coating layer to deteriorate. Here, the lithium-containing alkaline component present on the surface of the positive electrode active material refers to a component that does not function as a positive electrode active material, i.e., a component that does not directly contribute to the insertion and extraction of lithium ions. If the coating layer deteriorates, a resistive layer is formed at the interface between the positive electrode active material and the coating layer. This resistive layer increases the internal resistance of the battery during charging and discharging. Thus, when the positive electrode active material is covered with a material containing lithium fluorides, the deterioration of the lithium fluoride caused by the alkaline component on the surface of the positive electrode active material, and the accompanying increase in battery resistance, becomes a problem.

[0016] Patent document 3 describes a method of reducing the amount of alkaline components on the surface of a positive electrode active material by cleaning it with a water-soluble organic solvent.

[0017] Based on these insights, the inventors conceived of the technology disclosed herein.

[0018] The embodiments of this disclosure will now be described with reference to the accompanying drawings.

[0019] The following descriptions illustrate both general and specific examples. The numerical values, composition, shape, thickness, electrical properties, secondary battery structure, electrode materials, etc., shown below are merely examples and are not intended to limit the scope of this disclosure. Furthermore, any constituent elements not described in the independent claims representing the highest-level concept are optional constituent elements.

[0020] (Implementation Method 1) Figure 1This is a cross-sectional view showing the schematic structure of the covering active material in Embodiment 1. The covering active material 100 in Embodiment 1 includes a positive electrode active material 11, lithium carbonate (not shown) present on the surface of the positive electrode active material 11, and a covering layer 12. The covering layer 12 covers at least a portion of the surface of the positive electrode active material 11. The covering layer 12 is in direct contact with the positive electrode active material 11. The covering layer 12 contains a lithium-containing fluoride. When the mass of lithium carbonate (Li2CO3) present on the surface of the positive electrode active material 11 is determined by neutralization titration, the ratio R1 of the mass of lithium carbonate to the mass of the positive electrode active material 11 is 0.43% or more and 1.4% or less. In other words, when the mass of the positive electrode active material 11 is set to M1 and the mass of lithium carbonate present on the surface of the positive electrode active material 11 is set to M2, the value obtained by the formula 100×(M2 / M1) is in the range of 0.43 or more and 1.4 or less.

[0021] The alkaline component on the surface of the positive electrode active material 11 is, for example, a strongly alkaline component such as lithium hydroxide, formed by the adsorption of water onto the surface of the positive electrode active material 11 and the reaction of the residual lithium salt with lithium ions dissolved from the positive electrode active material 11 and water. During the generation of this strongly alkaline component, lithium ion-proton exchange occurs on the surface of the positive electrode active material 11, forming a Li-deficient layer (e.g., a NiO layer) on the surface of the positive electrode active material 11. It can be inferred that the presence of this Li-deficient layer also affects the output resistance. The strongly alkaline component absorbs carbon dioxide from the atmosphere to form lithium carbonates such as lithium bicarbonate, but as long as water and carbon dioxide are present, the generation of the strongly alkaline component and the formation of the Li-deficient layer will repeatedly occur. Here, lithium carbonate has relatively low solubility in water. Therefore, by controlling the amount of lithium carbonate on the surface of the positive electrode active material 11, and ensuring that the mass ratio R1 of lithium carbonate on the surface of the positive electrode active material 11 to the mass of the positive electrode active material 11 is within the aforementioned range, the reaction between lithium ions and water on the surface of the positive electrode active material 11, i.e., the exchange between lithium ions and protons on the surface of the positive electrode active material 11, can be suppressed, thereby reducing the formation of a Li-deficient layer on the surface of the positive electrode active material 11. Furthermore, it can be deduced that by controlling the amount of lithium carbonate on the surface of the positive electrode active material 11 within the aforementioned range, when the surface of the positive electrode active material 11 is covered with the capping layer 12, the deterioration of the capping layer 12 caused by the reaction between the lithium-containing alkaline components on the surface of the positive electrode active material 11 and the lithium-containing fluoride contained in the capping layer 12 can be suppressed. In other words, it can be deduced that the formation of a resistive layer at the interface between the positive electrode active material 11 and the capping layer 12 caused by the deterioration of the capping layer 12 can be suppressed. Therefore, according to the capping active material 100, the internal resistance of the battery can be reduced.

[0022] The ratio R1 can also be 0.43% or higher and 1.0% or lower. With this configuration, the internal resistance of the battery can be further reduced. The ratio R1 can be either 0.45% or higher and 1.0% or lower, or 0.48% or higher and 1.0% or lower.

[0023] When determining the mass of lithium originating from the lithium-containing alkaline component present on the surface of the positive electrode active material 11 by neutralization titration, the ratio R2 of the mass of lithium originating from the lithium-containing alkaline component present on the surface of the positive electrode active material 11 to the mass of the positive electrode active material 11 can also exceed 0.30% and be less than 0.40%. In other words, when the mass of the positive electrode active material 11 is set as M1 and the mass of lithium originating from the lithium-containing alkaline component present on the surface of the positive electrode active material 11 is set as M3, the value obtained by the formula 100×(M3 / M1) can also be in the range of exceeding 0.30 and being less than 0.40.

[0024] The ratio R2 can also be greater than 0.30% and less than 0.35%. With this configuration, the internal resistance of the battery can be further reduced. The ratio R2 can also be greater than 0.31% and less than 0.35%.

[0025] Ratios R1 and R2 can be calculated using the following neutralization titration. On the surface of the positive electrode active material 11, lithium hydroxide (LiOH), lithium carbonate (Li₂CO₃) as a lithium carbonate, and trace amounts of lithium bicarbonate (LiHCO₃) exist as lithium-containing alkaline components. Here, in the neutralization titration, the lithium-containing alkaline components present on the surface of the positive electrode active material 11 can be considered to consist only of lithium hydroxide and lithium carbonate. By measuring the mass of lithium hydroxide and the mass of lithium carbonate, ratios R1 and R2 are calculated.

[0026] Neutralization titration can be performed based on the Warder method. A specified amount (e.g., 2 g) of the positive electrode active material 11 powder is added to a specified amount (e.g., 200 mL) of deionized water, stirred thoroughly (e.g., for 30 minutes), and then allowed to stand (e.g., for 10 minutes). Next, the supernatant is filtered through a 0.2 μm syringe filter, and the resulting filtrate is used as the test solution. Phenolphthalein solution is added to the test solution as an indicator, and neutralization titration is performed using a 0.1 mol / L aqueous HCl solution under a nitrogen atmosphere. After the endpoint is detected with phenolphthalein, methyl orange solution is added to the test solution as an indicator, and neutralization titration is performed using a 0.1 mol / L aqueous HCl solution under a nitrogen atmosphere.

[0027] Based on the amount of HCl required until the endpoint of each reaction, the mass of lithium hydroxide (LiOH) and the mass of lithium carbonate (Li₂CO₃) contained in the test solution can be calculated. The mass of lithium derived from lithium hydroxide can be calculated from the mass of lithium hydroxide. The mass of lithium derived from lithium carbonate can be calculated from the mass of lithium carbonate. Thus, the total mass of lithium derived from lithium hydroxide and lithium derived from lithium carbonate, determined by neutralization titration, is taken as the mass of lithium derived from the lithium-containing alkaline component present on the surface of the positive electrode active material 11.

[0028] In this disclosure, "the mass of lithium carbonate present on the surface of the positive electrode active material 11" essentially refers to the mass of lithium carbonate present within the range that can be extracted by the above-described method. In this disclosure, "the mass of lithium originating from lithium-containing alkaline components present on the surface of the positive electrode active material 11" essentially refers to the mass of lithium originating from lithium-containing alkaline components present within the range that can be extracted by the above-described method.

[0029] When determining the mass of lithium hydroxide (LiOH) present on the surface of the positive electrode active material 11 by the above-described neutralization titration, the ratio R3 of the mass of lithium hydroxide to the mass of the positive electrode active material 11 can be 1.0% or less. The ratio R3 can also be 0.1% or more and 1.0% or less, 0.3% or more and 0.9% or less, 0.4% or more and 0.8% or less, or 0.56% or more and 0.73% or less. With this configuration, the internal resistance of the battery can be further reduced.

[0030] (Covering layer) The material constituting the capping layer 12 will be referred to as the "capping material". The capping active material 100 includes the positive electrode active material 11 and the capping material. The capping material contains lithium fluoride.

[0031] Lithium-containing fluorides can also be composed of Li, F, and at least one selected from Zr, Ti, and Al. Examples of such lithium-containing fluorides include Li₂ZrF₆, Li₃ZrF₇, Li₄ZrF₈, Li₃AlF₆, and Li₂TiF₆. With this configuration, the ionic conductivity of the lithium-containing fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0032] Lithium-containing fluorides may also include Li, Me1, Al, and F. Here, Me1 is selected from at least one of Ti and Zr. With this configuration, the ionic conductivity of the lithium-containing fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0033] Lithium-containing fluorides can also be composed of Li, Me1, Al, and F. Here, Me1 is selected from at least one of Ti and Zr. "Composed of Li, Me1, Al, and F" means that, apart from unavoidable impurities, no materials other than Li, Me1, Al, and F are intended to be added. With such a composition, the ionic conductivity of the lithium-containing fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0034] Lithium-containing fluorides can also be represented by the following composition formula (1).

[0035] Li 6-（m-mx+3x）b (Me1) 1-x Me2 x ) b Formula F6 (1) In the composition (1), Me1 is at least one selected from Ti and Zr, Me2 is at least one selected from Al and Y, and m is the valence of Me1, satisfying 0 < x < 1 and 0 < b ≤ 3.

[0036] Furthermore, in the case where Me1 contains multiple elements, in composition formula (1), m is the sum of the product of the composition ratio of each element and the valence of that element. For example, when Me1 contains elements M1 and M2, the composition ratio of element M1 is a1 and its valence is m1, the composition ratio of element M2 is a2 and its valence is m2, m is represented by m1a1 + m2a2.

[0037] This configuration improves the ionic conductivity of lithium-containing fluorides. As a result, the internal resistance of the battery can be further reduced.

[0038] In the composition formula (1), it can satisfy 0<x<1 and 0<b≤1.5, as well as 0.1≤x≤0.9 and 0.8≤b≤1.2.

[0039] In formula (1), 0.5 ≤ xb < 1 can also be satisfied. Based on this configuration, the ionic conductivity of the lithium fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0040] In the composition formula (1), the following conditions can also be met: 2.5 ≤ 6 - (m - mx + 3x)b ≤ 2.9, 0.1 ≤ (1 - x)b ≤ 0.5, and 0.5 ≤ xb ≤ 0.9. Based on this configuration, the ionic conductivity of the lithium fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0041] Me2 can also contain Al. Me2 can also be Al.

[0042] Lithium-containing fluorides can also be represented by the following composition formula (2).

[0043] Li α Me1 β Al γ Formula F6 (2) In the composition formula (2), Me1 is at least one of Ti and Zr, and α, β and γ satisfy α+4β+3γ=6 and γ>0.

[0044] In composition (2), γ can also satisfy 0.5 ≤ γ < 1. Based on this configuration, the ionic conductivity of lithium-containing fluorides can be improved. As a result, the internal resistance of the battery can be further reduced.

[0045] In composition (2), α, β, and γ can also satisfy 2.5≤α≤2.9, 0.1≤β≤0.5, and 0.5≤γ≤0.9. Based on this configuration, the ionic conductivity of lithium-containing fluorides can be improved. As a result, the internal resistance of the battery can be further reduced.

[0046] Me1 can also be Ti. Me1 can also be Zr. With this configuration, the ionic conductivity of lithium-containing fluorides can be improved. As a result, the internal resistance of the battery can be further reduced.

[0047] Lithium-containing fluorides can also be selected from Li 2.7 Ti 0.3 Al 0.7 F6 and Li 2.8 Zr 0.2 Al 0.8 At least one of F6. This configuration improves the ionic conductivity of lithium-containing fluorides. As a result, the internal resistance of the battery can be further reduced.

[0048] Lithium-containing fluorides are not limited to substances that strictly satisfy the above composition formula. For example, in addition to the constituent elements represented by composition formula (1), they may also include substances containing trace amounts of impurities. For example, in lithium-containing fluorides, impurities other than the constituent elements represented by composition formula may be less than 10% by mass.

[0049] Lithium-containing fluorides can also be represented by the following composition formula (3).

[0050] Li 6-（4-x-ny）b (Ti) 1-x-y Al x Me3 y ) b F 6-2z O z (3) Here, Me3 is selected from at least one of Zr, Ni, Fe and Cr, n is the valence of Me3, and satisfies 0.1 < x < 0.9, 0 ≤ y < 0.1, 0 ≤ z < 0.1 and 0.8 < b ≤ 1.2.

[0051] Furthermore, in the case that Me3 contains multiple elements, in composition formula (3), n is the sum of the product of the composition ratio of each element and the valence of that element. For example, when Me3 contains elements M1 and M2, the composition ratio of element M1 is a1 and its valence is n1, the composition ratio of element M2 is a2 and its valence is n2, n is represented by n1a1 + n2a2.

[0052] The covering material may also contain lithium fluoride as a main component. That is, the covering material may, for example, contain lithium fluoride at a mass ratio of 50% or more relative to the total mass of the covering layer 12.

[0053] The covering material may also contain lithium fluoride in a mass ratio of 70% or more relative to the total mass of the covering layer 12.

[0054] The covering material contains lithium fluoride as the main component, and may further contain unavoidable impurities, or starting materials, by-products and decomposition products used in the synthesis of lithium fluoride.

[0055] The covering material, for example, may contain lithium fluoride at a mass ratio of 100% relative to the total mass of the covering layer 12, except for unavoidable impurities. As mentioned above, the covering material may also consist solely of lithium fluoride.

[0056] The covering material can also be sulfur-free.

[0057] In the covering active material 100, the ratio of the volume of the covering layer 12 to the total volume of the positive electrode active material 11 and the covering layer 12 can be 1% or more and 10% or less. In other words, the ratio of the volume V2 of the covering layer 12 to the total volume (V1+V2) of the positive electrode active material 11 and the covering layer 12 (V2 / (V1+V2)) can also be in the range of 0.01 or more and 0.1 or less. If the ratio of the volume of the covering layer 12 to the total volume of the positive electrode active material 11 and the covering layer 12 is 1% or more, the surface of the positive electrode active material 11 can be sufficiently covered by the covering layer 12, thereby effectively suppressing the formation of a resistive layer between the positive electrode active material 11 and the covering layer 12. If the ratio of the volume of the covering layer 12 to the total volume of the positive electrode active material 11 and the covering layer 12 is 10% or less, the surface of the positive electrode active material 11 can be prevented from being over-covered by the covering layer 12. As a result, electron conduction channels between particles of the positive electrode active material 11 can be adequately ensured. Furthermore, the volume V1 of the positive electrode active material 11 refers to the total volume of the positive electrode active material 11 within the particle group covering the active material 100. The volume V2 of the capping layer 12 refers to the total volume of the capping layer 12 within the particle group covering the active material 100.

[0058] Based on the above structure, the internal resistance of the battery can be further reduced.

[0059] The ratio of the volume of the capping layer 12 to the total volume of the positive electrode active material 11 and the capping layer 12 can be calculated, for example, by averaging the ratios of 20 randomly selected volume values ​​obtained from cross-sectional SEM images of the capping active material 100 obtained using a scanning electron microscope (SEM). When the volume of the positive electrode active material 11 is defined as V1, the volume of the capping layer 12 as V2, and the volume of the capping active material 100 as V3, the volume V2 of the capping layer 12 is calculated in the form of V3-V1. Therefore, the ratio of the volume of the capping layer 12 to the total volume of the positive electrode active material 11 and the capping layer 12 is calculated in the form of (V3-V1) / V3.

[0060] The volume V1 of the positive electrode active material 11 can be calculated using the following method: The area of ​​the positive electrode active material 11 is calculated from the outline of the positive electrode active material 11 extracted from the cross-sectional SEM image. The radius (equivalent circle radius) r1 of the circle with an area equivalent to this area is calculated. The positive electrode active material 11 can be considered as a sphere with an equivalent circle radius r1, and the volume V1 of the positive electrode active material 11 is calculated from the equivalent circle radius r1. The volume V3 of the covering active material 100 can be calculated using the following method: The area of ​​the covering active material 100 is calculated from the outline of the covering active material 100 extracted from the cross-sectional SEM image. The radius (equivalent circle radius) r3 of the circle with an area equivalent to this area is calculated. The covering active material 100 can be considered as a sphere with an equivalent circle radius r3, and the volume V3 of the covering active material 100 is calculated from the equivalent circle diameter r3. The volume V3 of the covering active material 100 can also be calculated using the following method. The average thickness of the capping layer 12 is added to the equivalent circular radius r1 of the positive electrode active material 11 calculated from the cross-sectional SEM image, and this is considered as the equivalent circular radius r3 of the capping active material 100. The capping active material 100 can be regarded as a sphere with an equivalent circular radius r3, and the volume V3 of the capping active material 100 is calculated from the equivalent circular diameter r3. The average thickness of the capping layer 12 can be obtained, for example, by measuring the thickness of the capping layer 12 at 20 randomly selected points from the cross-sectional SEM image of the capping active material 100, and calculating the average value from these measurements.

[0061] The average thickness of the capping layer 12 can be 1 nm or more and 300 nm or less. If the average thickness of the capping layer 12 is 1 nm or more, the surface of the positive electrode active material 11 can be sufficiently covered by the capping layer 12, thus effectively suppressing the formation of a resistive layer between the positive electrode active material 11 and the capping layer 12. If the average thickness of the capping layer 12 is 300 nm or less, the surface of the positive electrode active material 11 can be prevented from being over-covered by the capping layer 12. As a result, the electron conduction channels between the particles of the positive electrode active material 11 can be appropriately ensured.

[0062] Based on the above structure, the internal resistance of the battery can be further reduced.

[0063] The covering layer 12 covers the positive electrode active material 11, suppressing the formation of an oxide film during battery charging caused by the oxidative decomposition of other solid electrolytes (such as the first solid electrolyte 21 described later). Therefore, according to the above configuration, the covering active material 100 can reduce the internal resistance of the battery.

[0064] The active material 100 is coated with particles, for example. The shape of the particles of the active material 100 is not particularly limited. The particles of the active material 100 can be needle-like, scale-like, spherical, or ellipsoidal.

[0065] The types and quantities of elements contained in the active substance 100 can be determined using known chemical analysis methods.

[0066] <Method for manufacturing lithium fluorides> The lithium-containing fluoride contained in the capping layer 12 can be manufactured, for example, by the following methods.

[0067] Prepare the raw material powder in a proportion that forms the target composition. For example, in the production of Li 2.7 Ti 0.3 Al 0.7 In the case of F6, LiF, AlF3 and TiF4 are prepared in a molar ratio of 2.7:0.7:0.3. In addition, the values ​​of “α”, “β” and “γ” in the above composition formula (2) can be adjusted by adjusting the raw materials, the proportions and the synthesis process.

[0068] After mixing the raw material powders, a mechanical-chemical grinding method is used to mix, pulverize, and react the powders. Alternatively, after mixing the raw material powders, calcination can be carried out in a vacuum or an inert atmosphere. For example, calcination can be carried out at a temperature range of 100°C to 800°C for more than 1 hour. This yields a lithium-containing fluoride with the above-described composition.

[0069] The composition (crystal structure) of the crystalline phase in lithium fluorides can be determined by adjusting the reaction method and reaction conditions between the raw material powders.

[0070] (Positive electrode active material) The positive electrode active material 11 includes, for example, a material that has the property of being able to insert and extract metal ions such as lithium ions.

[0071] Examples of positive electrode active materials 11 include lithium-containing transition metal oxides, transition metal fluorides, polyanionic materials, fluorinated polyanionic materials, transition metal sulfides, transition metal sulfides, or transition metal nitrides. Examples of polyanionic and fluorinated polyanionic materials include LiFePO4, LiCoPO4, Li2CoPO4F, Li2MnSiO4, and Li2FeSiO4. Examples of lithium-containing transition metal oxides include Li(Ni,Co,Al)O2, Li(Ni,Co,Mn)O2, or LiCoO2, which have a layered rock salt structure. For example, using lithium-containing transition metal oxides as the positive electrode active material 11 can reduce the manufacturing cost of the positive electrode and increase the average discharge voltage.

[0072] In this disclosure, when an element in a formula is represented as "(Ni,Co,Al)", the representation indicates that at least one element is selected from the group of elements enclosed in parentheses. That is, "(Ni,Co,Al)" is synonymous with "at least one element selected from Ni, Co, and Al". The same applies to other elements.

[0073] The positive electrode active material 11 has, for example, a particle shape.

[0074] The positive electrode active material 11 may also contain lithium nickel oxide.

[0075] The positive electrode active material 11 may also contain lithium nickel cobalt aluminum oxide.

[0076] Based on the above structure, the energy density of the battery can be increased.

[0077] The positive electrode active material 11 can also be Li(Ni,Co,Al)O2.

[0078] Li(Ni,Co,Al)O2 is a substance containing at least one additional element besides Li, Ni, Co, and Al. The additional element may be at least one or more elements selected from boron (B), sodium (Na), magnesium (Mg), silicon (Si), phosphorus (P), sulfur (S), potassium (K), calcium (Ca), titanium (Ti), vanadium (V), chromium (Cr), manganese (Mn), iron (Fe), copper (Cu), zinc (Zn), gallium (Ga), germanium (Ge), zirconium (Zr), niobium (Nb), molybdenum (Mo), indium (In), tin (Sn), tungsten (W), lanthanum (La), and cerium (Ce).

[0079] <Method for manufacturing the active substance> The active material 100 in Embodiment 1 can be manufactured, for example, by the method described below.

[0080] Figure 2 This is a flowchart illustrating a method for manufacturing the active material 100. The method for manufacturing the active material 100 includes: annealing the positive electrode active material 11 in a carbon dioxide atmosphere at a temperature of 100°C or higher and 700°C or lower (step S1), and covering at least a portion of the surface of the positive electrode active material 11 with a covering material containing lithium fluoride (step S4).

[0081] First, the positive electrode active material 11 is annealed in a carbon dioxide atmosphere at a temperature of 100°C or higher and 700°C or lower (step S1). Hereinafter, the annealing treatment in a carbon dioxide atmosphere is sometimes referred to as "carbonic acid annealing treatment".

[0082] In step S1, to control the amount of alkaline components on the surface of the positive electrode active material 11, the positive electrode active material 11 is annealed under a carbon dioxide atmosphere. Through carbonic acid annealing, the surface of the positive electrode active material 11 is covered with lithium carbonate components. This reduces the internal resistance of the battery. When determining the mass of lithium carbonate present on the surface of the positive electrode active material 11 by neutralization titration, the positive electrode active material 11 can be annealed with carbonic acid in such a way that the ratio of the mass of lithium carbonate present on the surface of the positive electrode active material 11 to the mass of the positive electrode active material 11 is 0.43% or more and 1.4% or less.

[0083] By annealing the positive electrode active material 11 under a carbon dioxide atmosphere, the alkaline component on the surface of the positive electrode active material 11 is controlled, stabilizing it in the form of lithium carbonate. This eliminates the reaction with water, thus preventing the intermittent and continuous reaction between lithium ions and water on the surface of the positive electrode active material 11. In other words, it reduces the exchange of lithium ions and protons on the surface of the positive electrode active material 11, thereby reducing factors that hinder lithium ion insertion and extraction. Furthermore, by forming a coating film of lithium carbonate that does not decompose at high potential on the surface of the positive electrode active material 11, oxidation resistance is increased.

[0084] The control of the lithium-containing alkaline components on the surface of the positive electrode active material 11 based on carbonic acid annealing can be conceived to follow the following mechanism. Figure 3 It is LiNi that has not undergone carbonic acid annealing treatment. 0.8 Co 0.15 Al 0.05 The ion chromatogram of water obtained by TG-MS determination of O2 shows a change in spectral shape around 150°C, indicating that water on the surface of the positive electrode active material 11 begins to be removed in this temperature range. Therefore, it can be inferred that the alkaline components on the surface of the positive electrode active material 11 are controlled from this temperature range. A series of water release behaviors converge around 400°C. Above 400°C, almost no water release from the surface of the positive electrode active material 11 occurs. Therefore, it can be seen that the alkalinity on the surface of the positive electrode active material 11 can be controlled by performing carbonic acid annealing treatment at a temperature above 100°C and below 700°C. The carbonic acid annealing temperature can also be above 100°C and below 600°C, above 150°C and below 500°C, or above 150°C and below 400°C. By controlling the lithium-containing alkaline components on the surface of the positive electrode active material 11 through step S1, a positive electrode active material 11 suitable for reducing the internal resistance of the battery can be obtained.

[0085] When the temperature of carbonic acid annealing is above 800℃, the positive electrode active material itself deteriorates, making it unsuitable for reducing the internal resistance of the battery.

[0086] There is no particular limitation on the time of carbonic acid annealing. The treatment time can be sufficient to control the lithium-containing alkaline components present on the surface of the positive electrode active material 11. The treatment time can also be more than 0.5 hours and less than 10 hours.

[0087] There are no particular limitations on the apparatus used to perform step S1. For example, an electric furnace, a gas furnace, or a high-frequency induction heating furnace can be used.

[0088] After step S1, the mass of lithium carbonate present on the surface of the positive electrode active material 11 can also be determined by neutralization titration (step S2).

[0089] After step S2, it can also be determined whether the mass ratio of lithium carbonate present on the surface of the positive electrode active material 11 to the mass of the positive electrode active material 11 is greater than or equal to 0.43% and less than or equal to 1.4% (step S3). Steps S1 to S3 can be repeated until the mass ratio of lithium carbonate present on the surface of the positive electrode active material 11 to the mass of the positive electrode active material 11 becomes greater than or equal to 0.43% and less than or equal to 1.4%.

[0090] After step S3, a covering material containing lithium fluoride is used to cover at least a portion of the surface of the positive electrode active material 11, where the mass ratio of lithium carbonate present on the surface of the positive electrode active material 11 to the mass of the positive electrode active material 11 is 0.43% or more and 1.4% or less (step S4). Step S4 is performed by composited positive electrode active material 11 and covering material. Through step S4, a covering layer 12 covering at least a portion of the surface of the positive electrode active material 11 is formed. Thus, the covered active material 100 is obtained.

[0091] The composite of the positive electrode active material 11 and the coating material is carried out, for example, by a dry particle composite method. In the dry particle composite method, the positive electrode active material 11 and the coating material are mixed in an appropriate ratio, and after grinding, the mixture is given mechanical energy. The grinding process can be carried out using a mixing device such as a ball mill. In order to suppress the oxidation of the material, the grinding process can also be carried out in a dry and inert atmosphere.

[0092] The dry particle composite process can also involve simultaneously applying mechanical energies such as impact, compression, and shear to a mixture containing the positive electrode active material 11 and the coating material while stirring. According to the dry particle composite process, the coating active material 100 can be efficiently manufactured.

[0093] The device that can be used in step S4 is any device that can impart mechanical energy such as impact, compression, or shear to the mixture; there are no particular limitations.

[0094] According to the above manufacturing method, the mass ratio of lithium present on the surface of the positive electrode active material 11 to the mass of the positive electrode active material 11 can be controlled within the aforementioned range. Therefore, when the surface of the positive electrode active material 11 is covered with a covering material, the deterioration of the covering layer 12 due to the reaction between the lithium-containing alkaline components present on the surface of the positive electrode active material 11 and the lithium-containing fluoride contained in the covering material can be suppressed. In other words, the formation of a resistive layer at the interface between the positive electrode active material 11 and the covering layer 12 due to the deterioration of the covering layer 12 can be suppressed. Therefore, the internal resistance of the battery can be reduced by using the covering active material 100 manufactured by the above manufacturing method.

[0095] (Implementation Method 2) The following describes Embodiment 2. Descriptions that are repeated in Embodiment 1 are omitted as appropriate.

[0096] [Cathode Material] Figure 4 This is a cross-sectional view showing the general structure of the positive electrode material 200 in Embodiment 2.

[0097] The positive electrode material 200 in Embodiment 2 includes the covering active material 100 of Embodiment 1 and the first solid electrolyte 21. The covering active material 100 can be manufactured using the manufacturing method described above. The first solid electrolyte 21 is, for example, in particle shape. Based on the first solid electrolyte 21, high ionic conductivity can be achieved in the positive electrode material 200.

[0098] (First solid electrolyte) The first solid electrolyte 21 comprises a solid electrolyte with high ionic conductivity. The first solid electrolyte 21 may also comprise a halide solid electrolyte. Halide solid electrolytes possess high ionic conductivity and excellent high potential stability. Furthermore, halide solid electrolytes have low electronic conductivity and high oxidation resistance, thus they are difficult to oxidize and decompose upon contact with the covering active material 100. Therefore, by comprising a halide solid electrolyte in the first solid electrolyte 21, the output characteristics of the battery can be improved.

[0099] Examples of halide solid electrolytes include Li3(Ca,Y,Gd)X6, Li2MgX4, Li2FeX4, Li(Al,Ga,In)X4, Li3(Al,Ga,In)X6, and LiI. In these halide solid electrolytes, element X is selected from at least one of Cl, Br, and I.

[0100] Halogenated solid electrolytes may also be sulfur-free.

[0101] The first solid electrolyte 21 may also include a sulfide solid electrolyte. Sulfide solid electrolytes have excellent ionic conductivity and flexibility. With this configuration, the characteristics of the battery can be improved.

[0102] As sulfide solid electrolytes, for example, Li₂S-P₂S₅, Li₂S-SiS₂, Li₂S-B₂S₃, Li₂S-GeS₂, and Li₂S-P₂S₅ can be used. 3.25 Ge 0.25 P 0.75 S4, Li 10 GeP2S 12 And so on. Among them, LiX, Li₂O, and MO can also be added. q Li p MO q And so on. Here, element X in "LiX" is at least one element selected from F, Cl, Br, and I. "MO" q "and "Li p MO q The element M in "MO" is at least one element selected from P, Si, Ge, B, Al, Ga, In, Fe, and Zn. q "and "Li p MO q In the equation, p and q are independent natural numbers.

[0103] The first solid electrolyte 21 can also be a sulfide solid electrolyte. That is, the first solid electrolyte 21 can also be composed of a sulfide solid electrolyte. "Composed of a sulfide solid electrolyte" means that, apart from unavoidable impurities, no materials other than the sulfide solid electrolyte are intended to be added. For example, the sulfide solid electrolyte can also contain lithium sulfide and phosphorus sulfide. For example, the sulfide solid electrolyte can also be Li2S-P2S5.

[0104] The shape of the first solid electrolyte 21 is not particularly limited; for example, it can be spherical, ellipsoidal, scaly, or fibrous. For example, the shape of the first solid electrolyte 21 can also be particles.

[0105] When the first solid electrolyte 21 is in the form of particles (e.g., spheres), the median particle size can be 100 μm or less. If the median particle size is 100 μm or less, the covering active material 100 and the first solid electrolyte 21 can form a good dispersion in the positive electrode material 200. As a result, the charge-discharge characteristics of the battery are improved. The median particle size of the first solid electrolyte 21 can also be 10 μm or less.

[0106] In this specification, "median particle size" refers to the particle size at which the cumulative volume of the particle size distribution in the volumetric reference is equal to 50%. The particle size distribution in the volumetric reference can be determined, for example, using a laser diffraction measuring device or an image analysis device.

[0107] The median particle size of the first solid electrolyte 21 can also be smaller than the median particle size of the covering active material 100. With this configuration, the covering active material 100 and the first solid electrolyte 21 can form a better dispersion in the cathode material 200.

[0108] The median particle size of the covering active material 100 can be 0.1 μm or more and 100 μm or less. If the median particle size of the covering active material 100 is 0.1 μm or more, the covering active material 100 and the first solid electrolyte 21 can form a good dispersion state in the positive electrode material 200. As a result, the charge and discharge characteristics of the battery are improved. In addition, if the median particle size of the covering active material 100 is 100 μm or less, the lithium diffusion rate inside the positive electrode active material 11 is improved. Therefore, the battery can operate at high output.

[0109] The median particle size of the covering active material 100 can also be larger than the median particle size of the first solid electrolyte 21. Even with this configuration, a good dispersion of the covering active material 100 and the first solid electrolyte 21 can be formed in the cathode material 200.

[0110] In cathode material 200, such as Figure 4 As shown, the first solid electrolyte 21 and the covering active material 100 can also be in contact with each other. At this time, the covering layer 12 and the first solid electrolyte 21 are also in contact with each other. The particles of the first solid electrolyte 21 can also be buried between the particles of the covering active material 100.

[0111] In the active material 100, the capping layer 12 can also uniformly cover the positive electrode active material 11. In other words, the active material 100 can be formed by covering the entire surface of the positive electrode active material 11 with the capping layer 12. The capping layer 12 inhibits direct contact between the positive electrode active material 11 and the first solid electrolyte 21, and inhibits the formation of an oxide film caused by the oxidative decomposition of the first solid electrolyte 21. Therefore, with this configuration, the internal resistance of the battery is further reduced.

[0112] In the active material 100, the capping layer 12 may also cover only a portion of the surface of the positive electrode active material 11. In other words, the active material 100 can also be formed by using the capping layer 12 to cover only a portion of the surface of the positive electrode active material 11.

[0113] The cathode material 200 may also include multiple first solid electrolytes 21 and multiple covering active materials 100.

[0114] The content of the first solid electrolyte 21 relative to the positive electrode material 200 can be the same as or different from the content of the covering active material 100 relative to the positive electrode material 200.

[0115] <Manufacturing Method of Cathode Material> A positive electrode material 200 can be obtained by mixing the active coating material 100 with the first solid electrolyte 21. There are no particular limitations on the method of mixing the active coating material 100 and the first solid electrolyte 21. For example, a mortar and pestle or a ball mill or a similar mixing apparatus can be used to mix the active coating material 100 and the first solid electrolyte 21. There are no particular limitations on the mixing ratio of the active coating material 100 and the first solid electrolyte 21.

[0116] (Implementation Method 3) The following describes Embodiment 3. Descriptions that are repeated in Embodiments 1 and 2 are omitted as appropriate.

[0117] Figure 5 This is a cross-sectional view showing the schematic configuration of the battery 300 in Embodiment 3. The battery 300 in Embodiment 3 includes a positive electrode 31, an electrolyte layer 32, and a negative electrode 33. The electrolyte layer 32 is disposed between the positive electrode 31 and the negative electrode 33.

[0118] The positive electrode 31 comprises the positive electrode material 200 of Embodiment 2. That is, the positive electrode 31 comprises covering active material 100 and a first solid electrolyte 21. The positive electrode 31 comprises a material having the property of being able to insert and extract metal ions (e.g., lithium ions).

[0119] Based on the above configuration, the charging and discharging efficiency of battery 300 can be improved.

[0120] Regarding the ratio "v1:100-v1" between the volume of the positive electrode active material 11 contained in the positive electrode 31 and the total volume of the covering material and the first solid electrolyte 21, it is also possible to satisfy 30≤v1≤95. Here, v1 represents the volume ratio of the positive electrode active material 11 when the total volume of the positive electrode active material 11, the covering material, and the first solid electrolyte 21 contained in the positive electrode 31 is set to 100. When 30≤v1 is satisfied, it is easy to ensure sufficient energy density of the battery 300. When v1≤95 is satisfied, it becomes easier for the battery 300 to operate at high output.

[0121] The thickness of the positive electrode 31 can be greater than 10 μm and less than 500 μm. If the thickness of the positive electrode 31 is greater than 10 μm, the energy density of the battery 300 can be sufficiently ensured. If the thickness of the positive electrode 31 is less than 500 μm, the battery 300 can operate at high output.

[0122] Electrolyte layer 32 is a layer containing an electrolyte. This electrolyte is, for example, a solid electrolyte. The solid electrolyte contained in electrolyte layer 32 is referred to as a second solid electrolyte. That is, electrolyte layer 32 may also contain a second solid electrolyte layer.

[0123] As the second solid electrolyte, at least one selected from halide solid electrolytes, sulfide solid electrolytes, oxide solid electrolytes, polymer solid electrolytes, and coordination hydride solid electrolytes may be used.

[0124] The second solid electrolyte may also include a solid electrolyte having the same composition as the solid electrolyte contained in the first solid electrolyte 21 of Embodiment 2.

[0125] When the second solid electrolyte includes a halide solid electrolyte, the second solid electrolyte may also include a halide solid electrolyte having the same composition as the halide solid electrolyte contained in the first solid electrolyte 21 of Embodiment 2. That is, the electrolyte layer 32 may also include a halide solid electrolyte having the same composition as the halide solid electrolyte contained in the first solid electrolyte 21 of Embodiment 2 described above. With this configuration, the characteristics of the battery can be further improved.

[0126] The second solid electrolyte may also include a solid electrolyte having a composition different from that contained in the first solid electrolyte 21 of Embodiment 2.

[0127] When the second solid electrolyte comprises a halide solid electrolyte, the second solid electrolyte may also comprise a halide solid electrolyte having a composition different from that contained in the first solid electrolyte 21 of Embodiment 2. That is, the electrolyte layer 32 may also comprise a halide solid electrolyte having a composition different from that contained in the first solid electrolyte 21 of Embodiment 2. With such a configuration, the characteristics of the battery 300 can be further improved.

[0128] The second solid electrolyte may also include a sulfide solid electrolyte. The second solid electrolyte may also include a sulfide solid electrolyte having the same composition as the sulfide solid electrolyte contained in the first solid electrolyte 21 of Embodiment 2. That is, the electrolyte layer 32 may also include a sulfide solid electrolyte having the same composition as the sulfide solid electrolyte contained in the first solid electrolyte 21 of Embodiment 2. Based on the above configuration, the electrolyte layer 32 includes a sulfide solid electrolyte with excellent reduction stability, therefore the negative electrode 33 can use a low-potential negative electrode material such as graphite or lithium metal. This improves the energy density of the battery 300. Furthermore, when the electrolyte layer 32 includes a sulfide solid electrolyte having the same composition as the sulfide solid electrolyte contained in the first solid electrolyte 21 of Embodiment 2, the characteristics of the battery 300 can be further improved.

[0129] The second solid electrolyte can also include oxide solid electrolytes. Examples of oxide solid electrolytes include NASICON-type solid electrolyte materials represented by LiTi2(PO4)3 and its elemental substitutes, (LaLi)TiO3-based perovskite-type solid electrolyte materials, and Li... 14 ZnGe4O 16 LISICON-type solid electrolyte materials, represented by Li4SiO4, LiGeO4 and their elemental substitutes, and Li7La3Zr2O 12 Garnet-type solid electrolyte materials, represented by its elemental substitutes, Li3PO4 and its N-substitutes, glass based on Li-BO compounds such as LiBO2 and Li3BO3 with added Li2SO4, Li2CO3, etc., and glass ceramics, etc.

[0130] The second solid electrolyte can also include a polymeric solid electrolyte. For example, a compound of a polymer and a lithium salt can be used as a polymeric solid electrolyte. The polymeric compound can also have an ethylene oxide structure. Polymers with an ethylene oxide structure can contain a higher proportion of lithium salt, thus further improving ionic conductivity. Lithium salts such as LiPF6, LiBF4, LiSbF6, LiAsF6, LiSO3CF3, LiN(SO2F)2, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(SO2C4F9), and LiC(SO2CF3)3 can be used. A single lithium salt can be used, or two or more can be used in combination.

[0131] The second solid electrolyte may also include a coordination hydride solid electrolyte. Examples of coordination hydride solid electrolytes include LiBH4-LiI and LiBH4-P2S5.

[0132] The electrolyte layer 32 may also contain a second solid electrolyte as a main component. That is, the electrolyte layer 32 may also contain a second solid electrolyte in a mass ratio of 50% or more (i.e., 50% by mass) relative to the total mass of the electrolyte layer 32.

[0133] Based on the above configuration, the characteristics of battery 300 can be further improved.

[0134] The electrolyte layer 32 may also contain a second solid electrolyte comprising 70% or more (i.e., 70% by mass) of the electrolyte layer 32 as a percentage of the total mass of the electrolyte layer 32.

[0135] Based on the above configuration, the characteristics of battery 300 can be further improved.

[0136] The electrolyte layer 32 contains a second solid electrolyte as the main component, and may further contain unavoidable impurities, or starting materials, by-products and decomposition products used in the synthesis of the second solid electrolyte.

[0137] Apart from unavoidable impurities, the electrolyte layer 32 may also contain a second solid electrolyte comprising 100% (i.e., 100% by mass) of the electrolyte layer 32 as a percentage of the total electrolyte layer 32. In other words, the electrolyte layer 32 may also be composed of a second solid electrolyte. Based on this configuration, the characteristics of the battery 300 can be further improved.

[0138] The electrolyte layer 32 may also contain two or more materials, selected as solid electrolytes, as a second solid electrolyte. The two or more solid electrolytes have different compositions. For example, the electrolyte layer 32 may also contain a halide solid electrolyte and a sulfide solid electrolyte as the second solid electrolyte.

[0139] The thickness of the electrolyte layer 32 can be 1 μm or more and 300 μm or less. If the thickness of the electrolyte layer 32 is 1 μm or more, the possibility of a short circuit between the positive electrode 31 and the negative electrode 33 is reduced. Furthermore, if the thickness of the electrolyte layer 32 is 300 μm or less, the battery 300 can operate more easily under high output conditions. In other words, by appropriately adjusting the thickness of the electrolyte layer 32, sufficient safety of the battery 300 can be ensured, and the battery 300 can operate under high output conditions.

[0140] The negative electrode 33 comprises a material having the property of being able to insert and extract metal ions (e.g., lithium ions). The negative electrode 33 may, for example, comprise a negative electrode active material (e.g., negative electrode active material particles).

[0141] The negative electrode active material can be a metal, carbon, oxide, nitride, tin compound, or silicon compound. The metal can be an elemental metal or an alloy. Examples of metal materials include lithium metal or lithium alloys. Examples of carbon materials include natural graphite, coke, graphitizable carbon, carbon fibers, spherical carbon, artificial graphite, or amorphous carbon. Examples of oxides include Li₄Ti₅O. 12 Examples of suitable materials include LiTi2O4 and TiO2. From a capacity density perspective, silicon, tin, silicon compounds, or tin compounds are preferred.

[0142] The negative electrode 33 may also contain a solid electrolyte. The solid electrolyte that can be contained in the negative electrode 33 is referred to as the third solid electrolyte. That is, the negative electrode 33 may also contain a third solid electrolyte. With this configuration, the lithium-ion conductivity inside the negative electrode 33 is improved, and the battery 300 can operate at high output. As the third solid electrolyte that can be contained in the negative electrode 33, materials exemplified as the second solid electrolyte in the electrolyte layer 32 can be used.

[0143] The median particle size of the negative electrode active material can also be larger than the median particle size of the third solid electrolyte contained in the negative electrode 33. This allows for a good dispersion of the negative electrode active material and the third solid electrolyte.

[0144] Regarding the ratio of the volume of the negative electrode active material contained in the negative electrode 33 to the volume of the third solid electrolyte, "v2:100-v2", it can also satisfy 30≤v2≤95. Here, v2 represents the volume ratio of the negative electrode active material when the total volume of the negative electrode active material and the third solid electrolyte contained in the negative electrode 33 is set to 100. When 30≤v2 is satisfied, it is easy to ensure sufficient energy density of the battery 300. When v2≤95 is satisfied, it becomes easier for the battery 300 to operate at high output.

[0145] The thickness of the negative electrode 33 can be greater than 10 μm and less than 500 μm. If the thickness of the negative electrode 33 is greater than 10 μm, it is easy to ensure sufficient energy density of the battery 300. If the thickness of the negative electrode 33 is less than 500 μm, it is easier for the battery 300 to operate at high output.

[0146] For the purpose of improving the adhesion between particles, at least one of the materials selected from the positive electrode 31, the electrolyte layer 32, and the negative electrode 33 may also include a binder. The binder is used to improve the adhesion of the materials constituting the electrode. Examples of binders include polyvinylidene fluoride, polytetrafluoroethylene, polyethylene, polypropylene, aromatic polyamide resin, polyamide, polyimide, polyamide-imide, polyacrylonitrile, polyacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polymethacrylic acid, polymethyl methacrylate, polyethyl methacrylate, polyhexyl methacrylate, polyvinyl acetate, polyvinylpyrrolidone, polyether, polyethersulfone, polyhexafluoropropylene, styrene-butadiene rubber, carboxymethyl cellulose, etc. Alternatively, a copolymer of two or more materials selected from tetrafluoroethylene, hexafluoroethylene, hexafluoropropylene, perfluoroalkyl vinyl ether, vinylidene fluoride, trifluorochloroethylene, ethylene, propylene, pentafluoropropylene, fluoromethyl vinyl ether, acrylic acid, and hexadiene can be used as a binder. Alternatively, two or more of these materials can be mixed and used as a binder.

[0147] For the purpose of improving electronic conductivity, at least one of the positive electrode 31 and the negative electrode 33 may also contain a conductive additive. Examples of conductive additives include graphite-based materials such as natural or artificial graphite, carbon black such as acetylene black and Ketjen black, conductive fibers such as carbon fibers or metal fibers, metal powders such as fluorinated carbon and aluminum, conductive whiskers such as zinc oxide or potassium titanate, conductive metal oxides such as titanium oxide, and conductive polymers such as polyaniline, polypyrrole, and polythiophene. Using carbon-based conductive additives can reduce the cost of battery 300.

[0148] Battery 300 can be configured into various shapes such as coin-shaped, cylindrical, square, sheet-shaped, button-shaped, flat, and stacked.

[0149] Battery 300 can be manufactured, for example, using the following methods.

[0150] The positive electrode material 200, the electrolyte layer 32 forming material, and the negative electrode 33 forming material are prepared separately in Embodiment 2. A laminate in which the positive electrode 31, electrolyte layer 32, and negative electrode 33 are sequentially arranged is fabricated using a known method. Thus, the battery 300 can be obtained.

[0151] The area of ​​the main surface of battery 300 is, for example, 1 cm². 2 Above and 100cm 2 The following applies. In this case, battery 300 can be used, for example, in portable electronic devices such as smartphones and digital cameras. Alternatively, the area of ​​the main surface of battery 300 can also be 100 cm². 2 Above and 1000cm 2Below. In this case, battery 300 can be used, for example, as a power source for large mobile devices such as electric vehicles. "Main surface" refers to the surface with the largest area in battery 300.

[0152] (Other implementation methods) (Postscript) The following technology is disclosed through the above description of the embodiments.

[0153] (Technology 1) A coating active substance comprising: Positive electrode active material, Lithium carbonate, which is present on the surface of the positive electrode active material, and A capping layer that covers at least a portion of the surface of the positive electrode active material; The coating layer contains lithium fluoride. When the mass of the lithium carbonate is determined by neutralization titration, the ratio R1 of the mass of the lithium carbonate to the mass of the positive electrode active material is 0.43% or more and 1.4% or less.

[0154] Based on this configuration, the internal impedance of the battery can be reduced.

[0155] (Technology 2) The active material covering according to Technology 1, wherein the ratio R1 is 1.0% or less. With this configuration, the internal resistance of the battery can be further reduced.

[0156] (Technology 3) The active material according to Technology 1 or 2, wherein the lithium-containing fluoride comprises Li, Me1, Al, and F, wherein Me1 is at least one selected from Ti and Zr. With this configuration, the ionic conductivity of the lithium-containing fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0157] (Technology 4) The covering active material according to Technology 1 or 2, wherein, The lithium-containing fluoride is represented by the following compositional formula (1), Li 6-（m-mx+3x）b (Me1) 1-x Me2 x ) b Formula F6 (1) Here, Me1 is at least one selected from Ti and Zr, Me2 is at least one selected from Al and Y, and m is the valence of Me1, satisfying 0 < x < 1 and 0 < b ≤ 3. With this configuration, the ionic conductivity of lithium fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0158] (Technology 5) The active material according to Technology 4, wherein in the composition (1), 0.5 ≤ xb < 1 is satisfied. With this configuration, the ionic conductivity of the lithium fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0159] (Technology 6) The active material according to Technology 4 or 5, wherein in the composition (1), 2.5 ≤ 6 - (m - mx + 3x)b ≤ 2.9, 0.1 ≤ (1 - x)b ≤ 0.5, and 0.5 ≤ xb ≤ 0.9 are satisfied. With this configuration, the ionic conductivity of the lithium fluoride can be improved. As a result, the internal resistance of the battery can be further reduced.

[0160] (Technology 7) The covering active material according to any one of Technologies 4 to 6, wherein, in the composition (1), Me2 is Al. With such a configuration, the internal resistance of the battery can be further reduced.

[0161] (Technology 8) The coating active material according to any one of Technologies 1 to 7, wherein the lithium-containing fluoride is selected from Li 2.7 Ti 0.3 Al 0.7 F6 and Li 2.8 Zr 0.2 Al 0.8 At least one of F6. This configuration allows for further reduction of the battery's internal resistance.

[0162] (Technology 9) The covering active material according to any one of Technologies 1 to 8, wherein the positive electrode active material comprises a lithium nickel oxide. With this configuration, the internal resistance of the battery can be reduced.

[0163] (Technology 10) The covering active material according to any one of Technologies 1 to 9, wherein the positive electrode active material comprises lithium nickel cobalt aluminum oxide. With this configuration, the energy density of the battery can be improved.

[0164] (Technology 11) A method for manufacturing a coating active substance, comprising the following steps: The positive electrode active material is annealed in a carbon dioxide atmosphere at a temperature above 100°C and below 700°C. At least a portion of the surface of the positive electrode active material is covered with a covering material containing lithium fluoride; The coating is achieved by combining the positive electrode active material with the coating material.

[0165] Based on this structure, it is possible to manufacture a covering active material that can reduce the internal resistance of the battery.

[0166] (Technology 12) The method for manufacturing a covering active material according to Technology 11, wherein the annealing temperature is 150°C or higher and 400°C or lower. With this configuration, a covering active material capable of further reducing the internal resistance of the battery can be manufactured.

[0167] (Technology 13) A method for manufacturing a coating active material according to Technology 11 or 12, comprising a step of determining the mass of lithium carbonate present on the surface of the positive electrode active material by neutralization titration between the annealing treatment and the coating process. With this configuration, a coating active material capable of reducing the internal resistance of the battery can be manufactured.

[0168] (Technology 14) The method for manufacturing a coating active material according to Technology 13 includes a step of determining, between performing the measurement and performing the coating, whether the ratio of the mass of lithium carbonate to the mass of the positive electrode active material is 0.43% or more and 1.4% or less. With this configuration, a coating active material capable of reducing the internal resistance of the battery can be manufactured.

[0169] (Technology 15) A cathode material comprising: The covering active substance described in any one of techniques 1 to 10, and The first solid electrolyte.

[0170] Based on this configuration, the internal impedance of the battery can be reduced.

[0171] (Technology 16) The positive electrode material according to Technology 15, wherein the first solid electrolyte comprises a halide solid electrolyte. With this configuration, the internal characteristics of the battery can be improved.

[0172] (Technology 17) The positive electrode material according to Technology 15 or 16, wherein the first solid electrolyte comprises a sulfide solid electrolyte. With this configuration, the internal characteristics of the battery can be further improved.

[0173] (Technology 18) A battery comprising: A positive electrode comprising the positive electrode material described in any one of techniques 15 to 17.

[0174] Based on this configuration, the internal resistance can be reduced.

[0175] (Technology 19) A battery comprising: The positive electrode comprises the positive electrode material described in any one of techniques 15 to 17. Negative electrode, and An electrolyte layer is disposed between the positive electrode and the negative electrode.

[0176] Based on this configuration, the internal resistance can be reduced.

[0177] (Technology 20) The battery according to Technology 19, wherein the electrolyte layer comprises a second solid electrolyte, the second solid electrolyte comprising a halide solid electrolyte having the same composition as the solid electrolyte contained in the first solid electrolyte. With this configuration, output characteristics can be improved.

[0178] (Technology 21) The battery according to Technology 19 or 20, wherein the electrolyte layer comprises a second solid electrolyte, the second solid electrolyte comprising a halide solid electrolyte having a composition different from that of the solid electrolyte contained in the first solid electrolyte. With such a configuration, output characteristics can be improved.

[0179] (Technology 22) The battery according to any one of Technologies 19 to 21, wherein the electrolyte layer comprises a second solid electrolyte, the second solid electrolyte comprising a sulfide solid electrolyte. With this configuration, output characteristics can be further improved.

[0180] Example The following examples illustrate the details of this disclosure. These examples are illustrative and the disclosure is not limited to them.

[0181] (Example 1) [Carbon dioxide annealing treatment of positive electrode active material] As the positive electrode active material, Li(Ni,Co,Al)O2 (hereinafter referred to as NCA) with an average particle size of 5 μm was prepared. 500 g of NCA was placed inside a small tubular furnace. The internal temperature of the small tubular furnace was set to 150°C, and the NCA was annealed for 2 hours with carbon dioxide gas flowing into the furnace at a rate of 10 mL / min. Thus, the positive electrode active material of Example 1 was obtained.

[0182] [Preparation of Covering Material (Containing Lithium Fluoride)] In a glove box under an argon atmosphere with a dew point controlled below -60°C and an oxygen value controlled below 5 ppm, LiF, AlF3, and TiF4 raw material powders were weighed to achieve a molar ratio of LiF:AlF3:TiF4 = 2.7:0.7:0.3. These raw material powders were then mixed in an agate mortar to obtain a mixture. Next, the mixture was ground using a planetary ball mill (Fritsch P-7 type) at 500 rpm for 12 hours. This yielded a product using LiF... 2.7 Ti 0.3 Al 0.7The composition of F6 (hereinafter referred to as LTAF) is represented by the following formula. The compound was mixed with an appropriate amount of solvent and milled using a planetary ball mill at 200 rpm for 20 minutes. The solvent was then removed by drying. Thus, LTAF powder (containing lithium fluoride) was obtained as a coating material. The average particle size of the LTAF powder was 0.5 μm.

[0183] The average particle size of LTAF was calculated from a planar SEM image of LTAF obtained using a scanning electron microscope (Keyence, 3D Real SurfaceView microscope, VE-8800, 5000x magnification). Specifically, the average value of the equivalent circle radii of 50 randomly selected particles in the planar SEM image of LTAF was calculated as the average particle size.

[0184] [Preparation of the active ingredient] In Example 1, the coating of the positive electrode active material with LTAF was performed using a particle recombination apparatus (Hosokawa Micron, NOBILTA NOB-MINI). 48.5 g of the positive electrode active material and 1.5 g of LTAF were placed in the NOB-MINI container. The NCA and LTAF were recombinated under conditions of 6000 rpm, 60 minutes of operation, and 550 W–740 W power. This yielded the coated active material of Example 1. The volume ratio of LTAF to the total volume of NCA and LTAF was 4.6%.

[0185] (Example 2) In the carbonic acid annealing treatment of the positive electrode active material, the internal temperature of the small tubular furnace was set to 400°C. Otherwise, the same as in Example 1, the covered active material of Example 2 was obtained.

[0186] (Comparative Example 1) In the carbonic acid annealing treatment of the positive electrode active material, the internal temperature of the small tubular furnace was set to 800°C. Otherwise, the same as in Example 1, the covering active material of Comparative Example 1 was obtained.

[0187] (Comparative Example 2) LTAF was coated onto NCA that had not undergone carbonic acid annealing, otherwise, the same as in Example 1, was used to obtain the active material of Comparative Example 2.

[0188] (Determination of the mass of lithium-containing alkaline components present on the surface of the positive electrode active material) For the positive electrode active material before coating in both the examples and comparative examples, the following procedures were performed. 2g of the positive electrode active material and 200mL of deionized water were placed in a beaker, stirred for 30 minutes, and then allowed to stand for 10 minutes. Next, the supernatant was filtered through a 0.2μm syringe filter, and the resulting filtrate was used as the test solution. Phenolphthalein solution was added to the test solution as an indicator, and neutralization titration was performed using a 0.1mol / L HCl aqueous solution under a nitrogen atmosphere. After detecting the endpoint with phenolphthalein, methyl orange solution was added to the test solution as an indicator, and neutralization titration was performed using a 0.1mol / L HCl aqueous solution under a nitrogen atmosphere. Assuming the presence of lithium hydroxide (LiOH) and lithium carbonate (Li₂CO₃) on the surface of the positive electrode active material, the mass of lithium hydroxide and the mass of lithium carbonate in the test solution were calculated from the amount of HCl required to reach the endpoint of each reaction. This mass of lithium carbonate is the mass of lithium carbonate present on the surface of the positive electrode active material. Furthermore, the mass of lithium derived from lithium carbonate was calculated from the mass of lithium carbonate. The mass of lithium originating from lithium hydroxide was calculated from the mass of lithium hydroxide. The total mass of lithium originating from lithium hydroxide and lithium originating from lithium carbonate was the mass of lithium originating from the lithium-containing alkaline component present on the surface of the positive electrode active material. Based on the calculated values ​​and the mass of the positive electrode active material, the mass ratios R1 (lithium carbonate to positive electrode active material), R2 (lithium originating from the lithium-containing alkaline component to positive electrode active material), and R3 (lithium hydroxide to positive electrode active material) were calculated. The results are shown in Table 1.

[0189] [Evaluation of battery manufacturing] The following processes were carried out using the active covering substances from the examples and comparative examples, respectively.

[0190] (Preparation of slurry for the positive electrode layer) 4.0 g of the covering active material, 0.094 g of VGCF as the conductive material, 1.024 g of LiI-LiBr-Li2S-P2S5 glass-ceramic (10LiI·15LiBr·75(0.75Li2S·0.25P2O5)) as the first solid electrolyte, 0.017 g of butadiene rubber binder, and 2.77 g of tetrahydronaphthalene were weighed and mixed using an ultrasonic homogenizer (SMT Corporation, UH-50). The resulting mixture was used as the slurry for the positive electrode layer. "VGCF" is a registered trademark of Showa Denko Corporation.

[0191] (Preparation of slurry for negative electrode layer) Weigh 3.0g of Li4Ti5O as the negative electrode active material. 12Particles (density 3.5 g / cc), 0.033 g of conductive carbon (density 2 g / cc), 0.039 g of butadiene rubber binder (density 0.9 g / cc), and 3.71 g of tetrahydronaphthalene were mixed for 30 minutes using an ultrasonic homogenizer (SMT UH-50). Then, 1.0 g of a LiI-LiBr-Li2S-P2S5 glass-ceramic (10LiI·15LiBr·75 (0.75Li2S·0.25P2O5), density 2 g / cc) as a sulfide-based solid electrolyte was added to the resulting slurry, and the mixture was again mixed for 30 minutes using an ultrasonic homogenizer (SMT UH-50). The resulting mixture was used as the slurry for the negative electrode layer.

[0192] (Preparation of slurry for electrolyte layer) Heptane, a heptane solution containing 5% by mass of butadiene rubber-based binder, and 1.0 g of LiI-LiBr-Li2S-P2S5 glass-ceramic with an average particle size of 2.5 μm as the second solid electrolyte were added to a polypropylene container and mixed for 30 seconds using an ultrasonic homogenizer (SMT UH-50). The container was then vibrated for 3 minutes to obtain a slurry for the solid electrolyte layer.

[0193] (Fabrication of an all-solid-state lithium-ion secondary battery) Using a coating machine, a slurry for the positive electrode layer was applied to the positive current collector (Al foil, 15 μm thick) using a doctor blade method. After coating, it was dried on a hot plate at 100°C for 30 minutes to obtain a positive electrode with a positive active material layer on the surface of the aluminum foil. Similarly, a slurry for the negative electrode layer was applied to the negative current collector (Ni foil, 22 μm thick) and dried to obtain a negative electrode with a negative active material layer on the surface of the Ni foil. In Examples 1-2 and Comparative Examples 1-2, the weight per unit area of ​​the negative active material layer was adjusted to achieve a specific charge capacity of 1.15 times that of the negative electrode when the specific charge capacity of the positive electrode was set to 185 mAh / g.

[0194] The above-mentioned positive electrode is pre-pressed. A solid electrolyte layer slurry is then applied to the surface of the pre-pressed positive electrode's active material layer using a die-coating machine and dried on a hot plate at 100°C for 30 minutes. Then, it is dried at 2 tons / cm². 2 Rolling is performed to obtain a positive electrode side laminate with a solid electrolyte layer on the surface of the positive electrode.

[0195] The aforementioned negative electrode is pre-pressed. A solid electrolyte layer slurry is then applied to the surface of the pre-pressed negative electrode's active material layer using a die-coating machine and dried on a hot plate at 100°C for 30 minutes. Then, a coating is applied at 2 ton / cm². 2Roll pressing is performed to obtain a negative electrode side laminate with a solid electrolyte layer on the surface of the negative electrode.

[0196] The positive electrode-side laminate and the negative electrode-side laminate are respectively punched to make the solid electrolyte layers adhere and overlap each other. Here, an unpressed solid electrolyte layer (using slurry for the solid electrolyte layer) is overlapped between the solid electrolyte layers of the positive electrode-side laminate and the solid electrolyte layers of the negative electrode-side laminate in a transfer state. Then, it is pressed at 160°C at 2 ton / cm 2 The cells are pressed to obtain a power generation unit having a positive electrode, a solid electrolyte layer, and a negative electrode in sequence. The obtained power generation unit is laminated and packaged, and fixed at 0.5 MPa, thereby producing an all-solid-state lithium-ion secondary battery (battery stack) for evaluation.

[0197] (evaluate) The test batteries of the embodiments and comparative examples were evaluated through the following steps.

[0198] (Initial resistance) The secondary battery was placed in a constant-temperature bath at 25°C. The constant-current, constant-voltage (CCCV) charging and CCCV discharging procedures described below were repeated twice. Constant-current charging was performed at a current value of 0.33C relative to the battery's theoretical capacity until the voltage reached 2.7V, followed by constant-voltage charging at 2.7V. Charging was stopped at a current value reaching a rate of 0.01C. Next, constant-current discharging was performed at a current value of 0.33C until the voltage reached 1.5V, followed by constant-voltage discharging at 1.5V. Discharging was stopped at a current value reaching a rate of 0.01C.

[0199] Next, the state of charge of the test battery was adjusted using the following CCCV charging method. Constant current charging was performed at a current value of 0.33C relative to the theoretical capacity of the battery until the voltage reached 2.0V, followed by constant voltage charging at 2.0V. Charging was terminated at a current value reaching a rate of 0.01C.

[0200] After adjusting the charging state, at 12mA / cm 2 The test battery was discharged for 2 seconds using a given current. The internal resistance of the battery was calculated by dividing the voltage change by the discharge current. The results are shown in Table 1.

[0201] (result) Compared to Comparative Example 2, which did not undergo carbonic acid annealing treatment of the positive electrode active material, Examples 1 and 2 showed a decrease in resistance. Furthermore, compared to Comparative Example 1, which underwent carbonic acid annealing treatment at 800°C, Examples 1 and 2 also showed a decrease in resistance. As described above, water in the positive electrode active material is removed starting at 150°C, therefore it can be inferred that carbonic acid annealing treatment at 150°C can control the alkaline components on the surface of the positive electrode active material. Additionally, it can be inferred that since water release converges around 400°C, performing carbonic acid annealing treatment with water near the surface removed can achieve more effective surface control. Through these effects, the internal resistance of the battery is reduced. In temperature regions above 400°C, water release from the surface of the positive electrode active material does not occur, but annealing treatment in high-temperature regions such as 800°C can cause changes in the crystal structure of the NCA itself, therefore it can be inferred that the resistance increases.

[0202] On the other hand, it can be inferred that even if the annealing temperature is above 400°C, within a range that does not cause changes in the crystal structure of the active material that would lead to an increase in battery resistance, a resistance of less than 6.8 Ωcm can still be achieved. 2 The resistance. Regarding the positive electrode active material before it is covered by the covering material, when the ratio R1 of the mass of lithium carbonate present on the surface of the positive electrode active material to the mass of the positive electrode active material is 0.43% or more and 1.4% or less, the internal resistance of the battery is reduced by controlling the alkaline component on the surface of the positive electrode active material.

[0203] Industrial availability The battery disclosed herein can be used, for example, as an all-solid-state lithium secondary battery.

Claims

1. A coating active substance, comprising: Positive electrode active material, Lithium carbonate, which is present on the surface of the positive electrode active material, and A capping layer that covers at least a portion of the surface of the positive electrode active material; The coating layer contains lithium fluoride. When the mass of the lithium carbonate is determined by neutralization titration, the ratio R1 of the mass of the lithium carbonate to the mass of the positive electrode active material is 0.43% or more and 1.4% or less.

2. The active material according to claim 1, wherein, The ratio R1 is below 1.0%.

3. The covering active material according to claim 1, wherein, The lithium-containing fluoride includes Li, Me1, Al, and F. The Me1 is selected from at least one of Ti and Zr.

4. The active material according to claim 1, wherein, The lithium-containing fluoride is represented by the following compositional formula (1), Li 6-（m-mx+3x）b (Me1) 1-x Me2 x ) b Formula F6 (1) Here, Me1 is at least one selected from Ti and Zr, Me2 is at least one selected from Al and Y, and m is the valence of Me1, satisfying 0 < x < 1 and 0 < b ≤ 3.

5. The active material according to claim 4, wherein, In the composition (1), 0.5 ≤ xb < 1 is satisfied.

6. The coating active material according to claim 4, wherein, In the composition (1), the following conditions are met: 2.5≤6-(m-mx+3x)b≤2.9, 0.1≤(1-x)b≤0.5 and 0.5≤xb≤0.

9.

7. The covering active material according to claim 4, wherein, In the composition formula (1), Me2 is Al.

8. The covering active material according to claim 1, wherein, The lithium-containing fluoride is selected from Li 2.7 Ti 0.3 Al 0.7 F6 and Li 2.8 Zr 0.2 Al 0.8 At least one of F6.

9. The covering active material according to claim 1, wherein, The positive electrode active material contains lithium nickel oxide.

10. The coating active material according to claim 1, wherein, The positive electrode active material comprises lithium nickel cobalt aluminum oxide.

11. A method for manufacturing a coating active substance, comprising the following steps: The positive electrode active material is annealed in a carbon dioxide atmosphere at a temperature above 100°C and below 700°C. At least a portion of the surface of the positive electrode active material is covered with a covering material containing lithium fluoride; The coating is achieved by combining the positive electrode active material with the coating material.

12. The method for manufacturing the coating active substance according to claim 11, wherein, The annealing temperature is above 150°C and below 400°C.

13. The method for manufacturing the coating active substance according to claim 11, wherein, The step includes determining the mass of lithium carbonate present on the surface of the positive electrode active material by neutralization titration between the annealing process and the covering process.

14. The method for manufacturing the coating active substance according to claim 13, wherein, The method includes a step of determining whether the mass ratio of the lithium carbonate to the mass of the positive electrode active material is greater than 0.43% and less than 1.4% between performing the measurement and performing the covering.

15. A cathode material comprising: The covering active substance according to any one of claims 1 to 10, and The first solid electrolyte.

16. The cathode material according to claim 15, wherein, The first solid electrolyte comprises a halide solid electrolyte.

17. The cathode material according to claim 15, wherein, The first solid electrolyte comprises a sulfide solid electrolyte.

18. A battery having a positive electrode comprising the positive electrode material of claim 15.

19. A battery comprising: The positive electrode comprises the positive electrode material as described in claim 15. Negative electrode, and An electrolyte layer is disposed between the positive electrode and the negative electrode.

20. The battery according to claim 19, wherein, The electrolyte layer contains a second solid electrolyte. The second solid electrolyte comprises a halide solid electrolyte having the same composition as the solid electrolyte contained in the first solid electrolyte.

21. The battery according to claim 19, wherein, The electrolyte layer contains a second solid electrolyte. The second solid electrolyte comprises a halide solid electrolyte having a composition different from that contained in the first solid electrolyte.

22. The battery according to claim 19, wherein, The electrolyte layer contains a second solid electrolyte. The second solid electrolyte comprises a sulfide solid electrolyte.

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