Composite particle, positive electrode, and all-solid-state battery

Abstract

A composite particle comprising a positive electrode active material particle and a coating film covering at least a portion of the surface of the positive electrode active material particle, wherein the coating film comprises a first layer covering at least a portion of the surface of the positive electrode active material particle and a second layer covering at least a portion of the surface of the first layer, wherein the first layer comprises an alkaline oxide comprising Li and M, where M is at least one of niobium and carbon, and the second layer comprises a phosphorus compound.

Description

Technology Field

[0001] The present disclosure relates to composite particles, positive electrodes, and all-solid-state batteries. Background Technology

[0002] Japanese Patent Publication No. 2010-135090 describes a compound containing a polyanion structure formed by a vapor phase method (e.g., PO4 3- A positive electrode active material for an all-solid-state battery is disclosed, comprising a reaction inhibition portion (coating film) made of a compound having an orthophosphate backbone.

[0003] Sulfide-based all-solid-state batteries (hereinafter abbreviated as "all-solid-state batteries") have been developed. All-solid-state batteries include a sulfide solid electrolyte. When the sulfide solid electrolyte comes into direct contact with positive electrode active material particles, the sulfide solid electrolyte may degrade. Degradation of the sulfide solid electrolyte (ion conduction path) can increase battery resistance. Therefore, it has been proposed to form a coating film on the surface of the positive electrode active material particles. By preventing direct contact between the positive electrode active material particles and the sulfide solid electrolyte through the coating film, the degradation of the sulfide solid electrolyte can be mitigated. Consequently, a reduction in battery resistance is expected.

[0004] However, when the coating film is composed of phosphorus compounds, there were cases where a high-resistance layer was formed due to the neutralization reaction between the highly acidic phosphorus compound (such as phosphate compounds) and the alkaline positive electrode active material during the coating film formation process or battery operation, causing the battery resistance (such as initial resistance) to increase.

[0005] The purpose of the present disclosure is to reduce battery resistance.

[0006] The technical configuration and effects of the present disclosure are described below. However, the mechanisms of operation described herein include presumptions. The mechanisms of operation do not limit the technical scope of the present disclosure.

[0007] (1) A positive electrode active material particle and a coating film covering at least a portion of the surface of the positive electrode active material particle, and

[0008] The coating film comprises a first layer covering at least a portion of the surface of the positive electrode active material particles and a second layer covering at least a portion of the surface of the first layer,

[0009] The first layer above comprises an alkaline oxide containing Li and M, wherein M is at least one of niobium (Nb) and carbon (C), and

[0010] The above second layer comprises a phosphorus compound,

[0011] Composite particles.

[0012] In the composite particle of (1) above, a first layer containing the alkaline oxide is interposed between the second layer containing the phosphorus compound and the positive electrode active material particle. As a result, the reaction between the phosphorus compound of the second layer and the positive electrode active material particle is suppressed, thereby reducing the battery resistance.

[0013] In addition, although the first layer has the characteristic of low resistance, if the first layer is in contact with a solid electrolyte present in the surroundings at the positive electrode, the alkaline oxide (a compound containing at least one of Li, Nb, and C) may decompose due to charging and discharging at high potential, thereby increasing the battery resistance (the rate of increase in battery resistance may increase). In contrast, in the composite particle of (1) above, since a second layer is interposed between the first layer and the solid electrolyte, the decomposition of the alkaline oxide of the first layer is suppressed. As a result, the battery resistance is reduced.

[0014] From the above, a reduction in battery resistance is expected in a battery using the composite particles of (1) above.

[0015] (2) The above alkaline oxide is lithium niobate (LiNbO3) or lithium carbonate (Li2CO3), a composite particle described in (1).

[0016] (3) The above-mentioned compound is a phosphate compound, a composite particle described in (1) or (2).

[0017] (4) A positive electrode comprising a composite particle described in any one of (1) to (3) and a sulfide solid electrolyte.

[0018] (5) A solid-state battery having a positive electrode, a negative electrode, and a separator as described in (4).

[0019] Hereinafter, embodiments of the present disclosure (hereinafter abbreviated as “present embodiments”) and examples of the present disclosure (hereinafter abbreviated as “present examples”) are described. However, the present embodiments and the present examples do not limit the technical scope of the present disclosure.

[0020] The above and other objects, features, aspects, and advantages of this invention will become clear from the following detailed description of this invention as understood in conjunction with the accompanying drawings. Brief explanation of the drawing

[0021] FIG. 1 is a conceptual diagram showing a composite particle in the present embodiment. FIG. 2 is a schematic flowchart of the method for manufacturing composite particles in the present embodiment. Figure 3a is a figure showing the results of STEM-EELS measurements. Figure 3b is a figure showing the results of STEM-EELS measurements. Figure 3c is a figure showing the elements detected at each point. Figure 4a is a figure showing the result of XPS measurement example 1. Figure 4b is a figure showing the result of XPS measurement example 1. Figure 5a is a figure showing the results of XPS measurement example 2. Figure 5b is a figure showing the results of XPS measurement example 2. Specific details for implementing the invention

[0022] Terms and Definitions, etc.

[0023] The descriptions "to provide," "to include," and "to have" are in an open-ended format. An open-ended format may or may not include additional elements in addition to the essential elements. The description "consists of" is in a closed format. However, even in a closed format, impurities that are incidental in the ordinary or additional elements unrelated to the present disclosure are not excluded.

[0024] Expressions such as "may" and "can" are used not in an obligatory sense meaning "must be done," but in a permissive sense meaning "having the possibility to do."

[0025] Elements expressed in the singular form include the plural form unless otherwise specified. For example, "particle" may mean not only "a single particle" but also "an aggregate of particles (powder, powder, group of particles)."

[0026] Unless otherwise specifically stated, the execution order of multiple steps, actions, and operations included in various methods is not limited to the order described. For example, multiple steps may proceed simultaneously. For example, multiple steps may be performed sequentially.

[0027] For example, numerical ranges such as “m to n%” include upper and lower limits unless otherwise specifically stated. That is, “m to n%” indicates a numerical range of “m% or more and n% or less.” Furthermore, “m% or more and n% or less” includes “greater than m% and less than n%.” Additionally, a numerical value arbitrarily selected from within the numerical range may become a new upper or lower limit. For example, a new numerical range may be established by arbitrarily combining a numerical value within the numerical range with a numerical value described in other parts of this specification, tables, drawings, etc.

[0028] When a compound is expressed by a stoichiometric formula (e.g., “LiCoO2”), said stoichiometric formula is merely a representative example of the compound. The compound may have a non-stoichiometric composition. For example, when lithium cobaltate is expressed as “LiCoO2,” unless specifically stated otherwise, lithium cobaltate is not limited to a compositional ratio of “Li / Co / O = 1 / 1 / 2” and may contain Li, Co, and O in any compositional ratio. Additionally, doping and substitution by trace elements may also be permitted.

[0029] "D50" represents the particle size at which the cumulative frequency from the smaller particle size side reaches 50% in a volume-based particle size distribution. D50 can be measured by laser diffraction.

[0030] <Composite Particle>

[0031] FIG. 1 is a conceptual diagram showing a composite particle in the present embodiment. The composite particle (100) may be called, for example, a “coated positive electrode active material.” The composite particle (100) includes a positive electrode active material particle (110) and a coating film (120). The composite particle (100) may, for example, form an aggregate. That is, one composite particle (100) may include two or more positive electrode active material particles (110). The composite particle (100) may, for example, have a D50 of 1 to 50 μm, have a D50 of 1 to 20 μm, or have a D50 of 5 to 15 μm.

[0032] Coating film

[0033] The coating film (120) is a shell of the composite particle (100). The coating film (120) covers at least a portion of the surface of the positive electrode active material particle (110). The coating film (120) includes a first layer (121) and a second layer (122). The first layer (121) covers at least a portion of the surface of the positive electrode active material particle (110). The second layer (122) covers at least a portion of the surface of the first layer (121).

[0034] In order to enhance the effect of the present disclosure, it is preferable that the first layer (121) substantially covers the entire surface of the positive electrode active material particles, and the second layer (122) substantially covers the entire surface of the first layer (121).

[0035] However, as long as it is within the range having the effect of the present disclosure, a portion of the surface of the positive electrode active material particle does not have to be covered with the first layer (121), and a portion of the surface of the first layer (121) does not have to be covered with the second layer (122).

[0036] For example, the first layer (121) and the second layer (122) may be overlapped entirely or partially. That is, within the scope of having the effects of the present disclosure, the coating film (120) may partially include a single-layer structure.

[0037] For example, the coverage rate of the first layer (121) may be higher than the coverage rate of the second layer (122). That is, within the range having the effect of the present disclosure, a portion of the first layer (121) may be exposed on the surface of the coating film (120).

[0038] For example, the coverage rate of the first layer (121) may be lower than the coverage rate of the second layer (122). That is, within the range having the effect of the present disclosure, a portion of the second layer (122) may be in contact with the surface of the positive electrode active material particle (110).

[0039] For example, the coating film (120) may each include a first layer (121) and a second layer (122) individually. For example, the coating film (120) may include a plurality of first layers (121) and a plurality of second layers (122). For example, the first layer (121) and the second layer (122) may be stacked alternately. The total of the first layer (121) and the second layer (122) may, for example, be 2 to 10 layers or 2 to 4 layers.

[0040] The coating film (120) may include additional layers as long as it includes the first layer (121) and the second layer (122). The coating film (120) may include, for example, a third layer and a fourth layer (not shown). The third layer and the fourth layer may have a composition different from that of the first layer (121) and the second layer (122).

[0041] 1st Floor

[0042] The first layer (121) comprises an alkaline oxide containing Li and M. M is at least one of niobium (Nb) and carbon (C). The alkaline oxide has a pH greater than 7 when the oxide or its precursor is dissolved in water.

[0043] The above alkaline oxide may be represented, for example, by the following formula (3) or the following formula (4).

[0044] Li y Nb z O x … (3)

[0045] Li y C z O x … (4)

[0046] In the above equations (3) and (4), y, z, and x are arbitrary numbers. y, z, and x can be determined, for example, by XPS, etc. y may satisfy, for example, the relationship 0 ≤ y < 2.5. A reduction in initial resistance is expected when y is less than 2.5. y may, for example, be 1.5 or less, 1 or less, or 0.5 or less.

[0047] Examples of alkaline oxides represented by equation (3) include LiNbO3, Li3NbO4, Li8Nb2O9, LiNb3O8, and LiNbO2.

[0048] As an alkaline oxide represented by Equation (4), Li2CO3 can be cited as an example. Additionally, the alkaline oxide may contain Li2CO3 as the main phase and may also contain some LiHCO3 which is likely to be generated from Li2CO3 in the atmosphere.

[0049] 2nd Floor

[0050] The second layer (122) contains a phosphorus compound. The phosphorus compound is a compound containing at least P.

[0051] As for the phosphorus compound, for example, a phosphoric acid compound may be cited. The second layer (122) may, for example, contain a phosphoric acid skeleton. The presence of the phosphoric acid skeleton can be confirmed by Time-of-Flight Secondary Ion Mass Spectrometry (TOF-SIMS). When the second layer (122) contains a phosphoric acid skeleton, in the TOF-SIMS of the composite particle (100), PO2 - , PO3 - Fragments such as the back can be detected.

[0052] The second layer (122) may further contain Li. The phosphorus compound may be represented, for example, by the following formula (5).

[0053] Li y PO x … (5)

[0054] In the above equation (5), y and x are arbitrary numbers. y and x can be determined, for example, by XPS, etc. y may satisfy, for example, the relationship 0 ≤ y < 2.5. A reduction in initial resistance is expected when y is less than 2.5. y may, for example, be 1.5 or less, 1 or less, 0.5 or less, or zero.

[0055] As for the phosphorus compound represented by formula (5), for example, Li 0.5 PO3 and PO x Examples include Li4P2O7 and Li3PO4.

[0056] Film thickness

[0057] The coating film (120) (the entire film) may, for example, have a thickness of 5 to 100 nm, a thickness of 5 to 50 nm, a thickness of 10 to 30 nm, or a thickness of 20 to 30 nm.

[0058] The thickness (t1) of the first layer (121) and the thickness (t2) of the second layer (122) may satisfy, for example, the relationship “t1 / t2=1 / 9 to 9 / 1”, the relationship “t1 / t2=3 / 7 to 7 / 3”, or the relationship “t1 / t2=4 / 6 to 6 / 4”.

[0059] The film thickness (thickness of the coating film) can be measured in the following order. A sample is prepared by embedding composite particles in a resin material. A cross-section is processed on the sample using an ion milling device. For example, an ion milling device manufactured by Hitachi High Technologies Co., Ltd., “Product Name: Arblade (Trademark) 5000” (or an equivalent thereof) may be used. The cross-section of the sample is observed by a Scanning Electron Microscope (SEM). For example, an SEM device manufactured by Hitachi High Technologies Co., Ltd., “Product Name: SU8030” (or an equivalent thereof) may be used. For 10 composite particles, the film thickness is measured at 20 fields of view for each. The arithmetic mean of the film thicknesses at a total of 200 locations is considered as the film thickness.

[0060] <Coverage Rate>

[0061] The coverage rate of the surface of the positive electrode active material particle (110) by the coating film (120) may be, for example, 95% or more. A reduction in initial resistance is expected by having a coverage rate of 95% or more. The coverage rate may be, for example, 95 to 100% or 96 to 100%.

[0062] The coverage rate can be measured, for example, by X-ray Photoelectron Spectroscopy (XPS). For example, the XPS device "PHI X-tool" (or an equivalent product) manufactured by ALVAC Pyssa may be used. A sample powder consisting of composite particles is set in the XPS. Narrow scan analysis is performed. The measurement data is processed by analysis software. For example, the analysis software "MulTiPak" (or an equivalent product) manufactured by ALVAC Pyssa may be used. Multiple elements are detected as the measurement data is analyzed. The ratio of each detected element is calculated from the area of ​​each peak. The coverage rate is calculated using the following formula.

[0063] θ={I1 / (I0+I1)}×100

[0064] θ : Coverage rate [%]

[0065] I0: Ratio of elements originating from core particles (positive electrode active material particles)

[0066] I1: Proportion of elements originating from the coating layer (coating film)

[0067] Positive electrode active material particles

[0068] The positive electrode active material particle (110) is the core of the composite particle (100). The positive electrode active material particle (110) may be a secondary particle (an aggregate of primary particles). The positive electrode active material particle (110) (secondary particle) may, for example, have a D50 of 1 to 50 μm, may have a D50 of 1 to 20 μm, or may have a D50 of 5 to 15 μm. The primary particle may, for example, have a maximum ferret diameter of 0.1 to 3 μm.

[0069] The positive electrode active material particle (110) (positive electrode active material) may include, for example, a transition metal oxide, a polyanion compound, etc. Within a single particle (positive electrode active material), the composition may be uniform or non-uniform. For example, the composition may be inclined from the surface of the particle toward the center. The composition may change continuously or discontinuously (stepwise).

[0070] <Transition Metal Oxide: Space Group R-3m>

[0071] Transition metal oxides may have any crystal structure. Transition metal oxides may include, for example, crystal structures belonging to the space group R-3m. For example, a compound represented by the general formula “LiMO2” may have a crystal structure belonging to the space group R-3m. Transition metal oxides may be represented, for example, by the following formula (C-1).

[0072] Li 1-a Ni x M 1-x O2… (C-1)

[0073] In the equation, the relationships -0.5≤a≤0.5 and 0≤x≤1 are satisfied.

[0074] M may include at least one type selected from the group consisting of, for example, Co, Mn and Al.

[0075] In the above equation (C-1), x is, for example, 0 <x≤0.1, 0.1≤x≤0.2, 0.2≤x≤0.3, 0.3≤x≤0.4, 0.4≤x≤0.5, 0.5≤x≤0.6, 0.6≤x≤0.7, 0.7≤x≤0.8, 0.8≤x≤0.9, 또는 0.9≤x≤1의 관계를 충족시키고 있어도 된다. a는, 예를 들면, -0.4≤a≤0.4, -0.3≤a≤0.3, -0.2≤a≤0.2, 또는 -0.1≤a≤0.1의 관계를 충족시키고 있어도 된다.

[0076] Transition metal oxides are, for example, LiCoO2, LiMnO2, LiNi 0.9 Co 0.1 O2, LiNi 0.9 Mn 0.1 It may include at least one selected from the group consisting of O2 and LiNiO2.

[0077] <ncm>

[0078] Transition metal oxides may be represented, for example, by the following formula (C-2). A compound represented by the following formula (C-2) may also be called an "NCM".

[0079] Li 1-a Ni x Co y Mn z O2… (C-2)

[0080] In the equation, -0.5≤a≤0.5, 0 <x<1, 0<y<1, 0<z<1, x+y+z=1의 관계가 충족된다.

[0081] In the above equation (C-2), x is, for example, 0 <x≤0.1, 0.1≤x≤0.2, 0.2≤x≤0.3, 0.3≤x≤0.4, 0.4≤x≤0.5, 0.5≤x≤0.6, 0.6≤x≤0.7, 0.7≤x≤0.8, 0.8≤x≤0.9, 또는 0.9≤x<1의 관계를 충족시키고 있어도 된다.

[0082] In the above equation (C-2), y is, for example, 0 <y≤0.1, 0.1≤y≤0.2, 0.2≤y≤0.3, 0.3≤y≤0.4, 0.4≤y≤0.5, 0.5≤y≤0.6, 0.6≤y≤0.7, 0.7≤y≤0.8, 0.8≤y≤0.9, 또는 0.9≤y<1의 관계를 충족시키고 있어도 된다.

[0083] In the above equation (C-2), z is, for example, 0 <z≤0.1, 0.1≤z≤0.2, 0.2≤z≤0.3, 0.3≤z≤0.4, 0.4≤z≤0.5, 0.5≤z≤0.6, 0.6≤z≤0.7, 0.7≤z≤0.8, 0.8≤z≤0.9, 또는 0.9≤z<1의 관계를 충족시키고 있어도 된다.

[0084] NCM is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.4 Co 0.3 Mn 0.3 O2, LiNi 0.3 Co 0.4 Mn 0.3 O2, LiNi 0.3 Co 0.3 Mn 0.4 O2, LiNi 0.5 Co 0.2 Mn 0.3 O2, LiNi 0.5 Co 0.3 Mn 0.2 O2, LiNi 0.5 Co 0.4 Mn 0.1 O2, LiNi 0.5 Co 0.1 Mn 0.4 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.6 Co 0.3 Mn 0.1 O2, LiNi 0.6 Co 0.1 Mn 0.3 O2, LiNi 0.7 Co 0.1 Mn 0.2 O2, LiNi 0.7 Co 0.2 Mn 0.1 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, and, LiNi 0.9 Co 0.05 Mn 0.05 It may include at least one type selected from the group consisting of O2.

[0085] <nca>

[0086] Transition metal oxides may be represented, for example, by the following formula (C-3). A compound represented by the following formula (C-3) may also be called "NCA".

[0087] Li 1-a Ni x Co y Al z O2… (C-3)

[0088] In the equation, -0.5≤a≤0.5, 0 <x<1, 0<y<1, 0<z<1, x+y+z=1의 관계가 충족된다.

[0089] In the above equation (C-3), x is, for example, 0 <x≤0.1, 0.1≤x≤0.2, 0.2≤x≤0.3, 0.3≤x≤0.4, 0.4≤x≤0.5, 0.5≤x≤0.6, 0.6≤x≤0.7, 0.7≤x≤0.8, 0.8≤x≤0.9, 또는 0.9≤x<1의 관계를 충족시키고 있어도 된다.

[0090] In the above equation (C-3), y is, for example, 0 <y≤0.1, 0.1≤y≤0.2, 0.2≤y≤0.3, 0.3≤y≤0.4, 0.4≤y≤0.5, 0.5≤y≤0.6, 0.6≤y≤0.7, 0.7≤y≤0.8, 0.8≤y≤0.9, 또는 0.9≤y<1의 관계를 충족시키고 있어도 된다.

[0091] In the above equation (C-3), z is, for example, 0 <z≤0.1, 0.1≤z≤0.2, 0.2≤z≤0.3, 0.3≤z≤0.4, 0.4≤z≤0.5, 0.5≤z≤0.6, 0.6≤z≤0.7, 0.7≤z≤0.8, 0.8≤z≤0.9, 또는 0.9≤z<1의 관계를 충족시키고 있어도 된다.

[0092] NCA is, for example, LiNi 0.7 Co 0.1 Al 0.2 O2, LiNi 0.7 Co 0.2 Al 0.1 O2, LiNi 0.8 Co 0.1 Al 0.1 O2, LiNi 0.8 Co 0.17 Al 0.03 O2, LiNi 0.8 Co 0.15 Al 0.05 O2, and, LiNi 0.9 Co 0.05 Al 0.05 It may include at least one type selected from the group consisting of O2.

[0093] Multicomponent system

[0094] The positive electrode active material may include, for example, two or more types of NCM, etc. The positive electrode active material may include, for example, NCM (0.6 ≤ x) and NCM (x < 0.6). "NCM (0.6 ≤ x)" represents a compound in which x (Ni ratio) in the above formula (C-2) is 0.6 or higher. NCM (0.6 ≤ x) may also be called, for example, "high-nickel material." NCM (0.6 ≤ x) is, for example, LiNi 0.8 Co 0.1 Mn 0.1 Includes O2, etc. "NCM(x<0.6)" represents a compound in which x (Ni ratio) is less than 0.6 in the above formula (C-2). NCM(x<0.6) is, for example, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 Includes O2, etc. The mixing ratio (mass ratio) of NCM (0.6 ≤ x) and NCM (x < 0.6) may be, for example, “NCM (0.6 ≤ x) / NCM (x < 0.6) = 9 / 1 to 1 / 9”, “NCM (0.6 ≤ x) / NCM (x < 0.6) = 9 / 1 to 4 / 6”, or “NCM (0.6 ≤ x) / NCM (x < 0.6) = 9 / 1 to 3 / 7”.

[0095] The positive electrode active material may include, for example, NCA and NCM. The mixing ratio (mass ratio) of NCA and NCM may be, for example, "NCA / NCM = 9 / 1 to 1 / 9", "NCA / NCM = 9 / 1 to 4 / 6", or "NCA / NCM = 9 / 1 to 3 / 7". The Ni ratio between NCA and NCM may be the same or different. The Ni ratio of NCA may be higher than the Ni ratio of NCM. The Ni ratio of NCA may be lower than the Ni ratio of NCM.

[0096] <Transition metal oxide : Space group C2 / m>

[0097] The transition metal oxide may include, for example, a crystal structure belonging to the space group C2 / m. The transition metal oxide may be represented, for example, by the following formula (C-4).

[0098] Li2MO3… (C-4)

[0099] In the formula, M may include at least one selected from the group consisting of, for example, Ni, Co, Mn, and Fe.

[0100] The positive electrode active material may include, for example, a mixture of LiMO2 (space group R-3m) and Li2MO3 (space group C2 / m). The positive electrode active material may include, for example, a solid solution of LiMO2 and Li2MO3 (Li2MO3-LiMO2), etc.

[0101] <Transition metal oxide: Space group Fd-3m>

[0102] The transition metal oxide may include, for example, a crystal structure belonging to the space group Fd-3m. The transition metal oxide may be represented, for example, by the following formula (C-5).

[0103] LiMn 2-x M x O4… (C-5)

[0104] In the equation, the relationship 0≤x≤2 is satisfied.

[0105] M may include at least one selected from the group consisting of, for example, Ni, Fe, and Zn.

[0106] LiM2O4 (space group Fd-3m) is, for example, LiMn2O4, and, LiMn 1.5 Ni 0.5 It may include at least one selected from the group consisting of O4. The positive electrode active material may include, for example, a mixture of LiMO2 (space group R-3m) and LiM2O4 (space group Fd-3m). The mixing ratio (mass ratio) of LiMO2 (space group R-3m) and LiM2O4 (space group Fd-3m) may be, for example, “LiMO2 / LiM2O4=9 / 1~9 / 1”, “LiMO2 / LiM2O4=9 / 1~5 / 5”, or “LiMO2 / LiM2O4=9 / 1~7 / 3”.

[0107] Polyanion compounds

[0108] The polyanion compound may include, for example, phosphates (e.g., LiFePO4), silicates, borates, etc. The polyanion compound may be represented, for example, by the following formulas (C-6) to (C-9).

[0109] LiMPO4… (C-6)

[0110] Li 2-x MPO4F … (C-7)

[0111] Li2MSiO4… (C-8)

[0112] LiMBO3… (C-9)

[0113] Among the above formulas (C-6) to (C-9), M may include at least one selected from the group consisting of, for example, Fe, Mn, and Co. Among the above formula (C-7), for example, the relationship 0≤x≤2 may be satisfied.

[0114] The positive electrode active material may include, for example, a mixture of LiMO2 (space group R-3m) and a polyanion compound. The mixing ratio (mass ratio) of LiMO2 (space group R-3m) and the polyanion compound may be, for example, “LiMO2 / polyanion compound = 9 / 1 to 9 / 1”, “LiMO2 / polyanion compound = 9 / 1 to 5 / 5”, or “LiMO2 / polyanion compound = 9 / 1 to 7 / 3”.

[0115] Dopant

[0116] A dopant may be added to the positive electrode active material. The dopant may be diffused throughout the particle or locally distributed. For example, the dopant may be localized on the particle surface. The dopant may be a substitutional solid solution atom or an interstitial solid solution atom. The amount of dopant added (molar fraction relative to the total positive electrode active material) may be, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%. One type of dopant may be added, or two or more types of dopants may be added. Two or more types of dopants may form a complex.

[0117] The dopant may include at least one selected from the group consisting of, for example, B, C, N, halogen, Si, Na, Mg, Al, Mn, Co, Cr, Sc, Ti, V, Cu, Zn, Ga, Ge, Se, Sr, Y, Zr, Nb, Mo, In, Pb, Bi, Sb, Sn, W, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, and actinoids.

[0118] For example, the set of “Zr, Mg, W, Sm”, the set of “Ti, Mn, Nb, Si, Mo”, or the set of “Er, Mg” may be added to NCA.

[0119] For example, Ti may be added to NCM. For example, a set of "Zr, W", a set of "Si, W", or a set of "Zr, W, Al, Ti, Co" may be added to NCM.

[0120] All-solid-state battery

[0121] The all-solid-state battery includes a power generation element. The power generation element includes a positive electrode containing the above-mentioned composite particles, a separator, and a negative electrode.

[0122] The all-solid-state battery may include an outer casing. The outer casing may house a power generation element and an electrolyte. The outer casing may have any shape. For example, the outer casing may be a metal case or a pouch made of a metal foil laminate film. The case may have any shape. For example, the case may be cylindrical, prismatic, flat, coin-shaped, etc. The outer casing may include, for example, Al. For example, the outer casing may house a single power generation element or multiple power generation elements. For example, the multiple power generation elements may form a series circuit or a parallel circuit. Within the outer casing, the multiple power generation elements may be stacked in the thickness direction of the all-solid-state battery (cell).

[0123] [Development Factors]

[0124] The power generation element includes a positive electrode and a negative electrode. The power generation element may further include a separator. The separator is placed between the positive electrode and the negative electrode. The power generation element may have any shape. For example, the power generation element may be of a stacked type. For example, the power generation element may be formed by alternately stacking the positive electrode and the negative electrode while inserting a separator between the positive electrode and the negative electrode. The power generation element may be of a wound type. For example, a laminate may be formed by stacking a strip-shaped positive electrode, a strip-shaped separator, and a strip-shaped negative electrode. The power generation element may be formed by winding the said laminate in a vortex shape. The wound-type power generation element may be formed into a flat shape after winding.

[0125] The power generation element may, for example, have an anode-free structure. An "anode-free structure" refers to a structure in which a solid negative electrode active material is not present prior to the initial charge. Of course, the power generation element does not have to be an anode-free structure.

[0126] Straight Drama

[0127] The positive electrode has a layered shape. The positive electrode may include, for example, a positive electrode active material layer and a positive electrode current collector. For example, the positive electrode active material layer may be formed by coating a positive electrode composite material on the surface of the positive electrode current collector. The positive electrode current collector may include, for example, an Al foil. The positive electrode current collector may have a thickness of, for example, 5 to 50 μm.

[0128] The positive electrode active material layer may have a thickness of, for example, 10 to 200 μm. The positive electrode active material layer is in close contact with the separator. The positive electrode active material layer includes a positive electrode composite material. The positive electrode composite material may include the above-mentioned composite particles (coated positive electrode active material) and a sulfide solid electrolyte.

[0129] The sulfide solid electrolyte can form an ion conduction path within the positive electrode active material layer. The amount of the sulfide solid electrolyte may be, for example, 1 to 200 volume parts, 50 to 150 volume parts, or 50 to 100 volume parts with respect to 100 volume parts of composite particles (positive electrode active material). The sulfide solid electrolyte contains sulfur (S). The sulfide solid electrolyte may contain, for example, Li, P, and S. The sulfide solid electrolyte may further contain, for example, oxygen (O), silicon (Si), etc. The sulfide solid electrolyte may further contain, for example, halogens, etc. The sulfide solid electrolyte may further contain, for example, iodine (I), bromine (Br), etc. The sulfide solid electrolyte may be, for example, of a glass ceramic type or of an azirodite type. The sulfide solid electrolyte may include, for example, at least one selected from the group consisting of LiI-LiBr-Li3PS4, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2O-Li2S-P2S5, LiI-Li2S-P2O5, LiI-Li3PO4-P2S5, Li2S-P2S5, and Li3PS4.

[0130] For example, “LiI-LiBr-Li3PS4” represents a sulfide solid electrolyte produced by mixing LiI, LiBr, and Li3PS4 in any molar ratio. For example, the sulfide solid electrolyte may be produced by a mechanochemical method. “Li2S-P2S5” contains Li3PS4. Li3PS4 can be produced, for example, by mixing Li2S and P2S5 in a ratio of “Li2S / P2S5 = 75 / 25 (molar ratio)”.

[0131] The positive electrode active material layer may further include, for example, a conductive material. The conductive material can form an electron conduction path within the positive electrode active material layer. The amount of the conductive material may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of the composite particle (positive electrode active material). The conductive material may include, for example, at least one selected from the group consisting of graphite, acetylene black (AB), Ketjen black (registered trademark), vapor-grown carbon fiber (VGCF), carbon nanotube (CNT), and graphene flake (GF).

[0132] The positive electrode active material layer may further include, for example, a binder. The amount of binder may be, for example, 0.1 to 10 parts by mass per 100 parts by mass of composite particles (positive electrode active material). The binder may include any component. The binder may include, for example, at least one selected from the group consisting of polyvinylidene fluoride (PVdF), vinylidene fluoride-hexafluoropropylene copolymer (PVdF-HFP), tetrafluoroethylene (PTFE), CMC, PAA, polyvinyl alcohol (PVA), polyvinylpyrrolidone (PVP), polyoxyethylene alkyl ether, and derivatives thereof.

[0133] 《Bugeuk》

[0134] The negative electrode has a layered shape. The negative electrode may include, for example, a negative electrode active material layer and a negative electrode current collector. For example, the negative electrode active material layer may be formed by coating a negative electrode composite material on the surface of the negative electrode current collector. The negative electrode current collector may include, for example, copper (Cu) foil, Ni foil, etc. The negative electrode current collector may have a thickness of, for example, 5 to 50 μm.

[0135] The negative electrode active material layer may have a thickness of, for example, 10 to 200 μm. The negative electrode active material layer is in close contact with the separator. The negative electrode active material layer includes a negative electrode composite material. The negative electrode composite material includes negative electrode active material particles and a sulfide solid electrolyte. The negative electrode composite material may further include a conductive material and a binder. Between the negative electrode composite material and the positive electrode composite material, the sulfide solid electrolyte may be of the same type or different type.

[0136] The negative electrode active material particles may include any component. The negative electrode active material particles (negative electrode active material) are, for example, natural graphite, artificial graphite, soft carbon, hard carbon, silicon (Si), SiO, Li-silicate, Si-based alloy, tin (Sn), SnO, Sn-based alloy, and Li4Ti5O 12 It may include at least one type selected from the group consisting of

[0137] Carbon-based active material

[0138] "Graphite" is a general term for natural graphite and artificial graphite. Graphite may be a mixture of natural graphite and artificial graphite. The mixing ratio (mass ratio) may be, for example, "natural graphite / artificial graphite = 1 / 9 to 9 / 1," "natural graphite / artificial graphite = 2 / 8 to 8 / 2," or "natural graphite / artificial graphite = 3 / 7 to 7 / 3."

[0139] The graphite may contain a dopant. The dopant may contain at least one selected from the group consisting of, for example, B, N, P, Li, and Ca. The amount added may be, in mole fraction, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1%.

[0140] The surface of the graphite may be coated, for example, with amorphous carbon. The surface of the graphite may be coated, for example, with a heterogeneous material. The heterogeneous material may include, for example, at least one selected from the group consisting of P, W, Al, and O. The heterogeneous material may include, for example, at least one selected from the group consisting of Al(OH)3, AlOOH, Al2O3, WO3, Li2CO3, LiHCO3, and Li3PO4.

[0141] Alloy-based active material

[0142] SiO may be represented, for example, by the following formula (A-1).

[0143] SiO x … (A-1)

[0144] During meal, 0 <x<2의 관계가 충족된다.

[0145] In the above equation (A-1), x may satisfy, for example, the relationship 0.5≤x≤1.5 or 0.8≤x≤1.2.

[0146] The Li silicate may include at least one selected from the group consisting of, for example, Li4SiO4, Li2SiO3, Li2Si2O5, and Li8SiO6. The second negative electrode active material may include, for example, a mixture of Si and Li silicate. The mixing ratio (mass ratio) may be, for example, “Si / Li silicate = 1 / 9 to 9 / 1”, “Si / Li silicate = 2 / 8 to 8 / 2”, “Si / Li silicate = 3 / 7 to 7 / 3”, or “Si / Li silicate = 4 / 6 to 6 / 4”.

[0147] The alloy-based active material (Si, SiO, etc.) may contain additives. The additives may be, for example, substitutional solid solution atoms or interstitial solid solution atoms. The additives may also be deposits attached to the surface of the alloy-based active material. The deposits may be, for example, elements, oxides, carbides, nitrides, halides, etc. The amount of additive may be, for example, 0.01 to 5%, 0.1 to 3%, or 0.1 to 1% in mole fraction. The additives may include, for example, at least one selected from the group consisting of Li, Na, K, Rb, Be, Mg, Ca, Sr, Fe, Ba, B, Al, Ga, In, C, Ge, Sn, Pb, N, P, As, Y, Sb, and S. That is, Mg or Na may be doped into SiO. For example, Mg silicate, Na silicate, etc. may be formed. For example, boron oxide (e.g., B2O3, etc.), yttrium oxide (e.g., Y2O3, etc.), etc. may be added to SiO.

[0148] <Si-C 복합 재료>

[0149] The second negative electrode active material may include, for example, a composite material of a carbon-based active material (graphite, etc.) and an alloy-based active material (Si, etc.). A composite material containing Si and carbon may also be called a "Si-C composite material." For example, Si fine particles may be dispersed within carbon particles. For example, Si fine particles may be dispersed within graphite particles. For example, Li-silicate particles may be coated by a carbon material (amorphous carbon, etc.). A mixture of the Si-C composite material and graphite may be used.

[0150] Multicomponent system

[0151] The second negative electrode active material may contain two or more components. The second negative electrode active material may contain a carbon-based active material (graphite, etc.) and an alloy-based active material (Si, SiO, etc.). The mixing ratio (mass ratio) of the carbon-based active material and the alloy-based active material may be, for example, “carbon-based active material / alloy-based active material = 1 / 9 to 9 / 1”, “carbon-based active material / alloy-based active material = 2 / 8 to 8 / 2”, “carbon-based active material / alloy-based active material = 3 / 7 to 7 / 3”, or “carbon-based active material / alloy-based active material = 4 / 6 to 6 / 4”.

[0152] Binder

[0153] The second negative electrode active material may be fixed to the negative electrode current collector (21), porous body (22), etc., by means of a binder, for example. The binder may include any component. The binder may include, for example, at least one selected from the group consisting of polyacrylic acid (PAA), carboxymethylcellulose (CMC), styrene butadiene rubber (SBR), acrylate butadiene rubber (ABR), polyacrylonitrile (PAN), and derivatives thereof.

[0154] Separator

[0155] A separator (layer) is interposed between the positive electrode and the negative electrode. The separator separates the positive electrode from the negative electrode. The separator contains a sulfide solid electrolyte. The separator may further contain a binder. Between the separator and the positive electrode composite material, the sulfide solid electrolyte may be of the same type or different type. Between the separator and the negative electrode composite material, the sulfide solid electrolyte may be of the same type or different type.

[0156] The present embodiment may be added to the first to third cell configurations, for example. The present embodiment may be combined with the first to third cell configurations, for example. The present embodiment may replace a part of the first to third cell configurations, for example. For example, the negative electrode in the first cell configuration may be replaced with the negative electrode in the present embodiment (negative electrode current collector (21), porous body (22)). For example, the negative electrode in the first cell configuration may be used in combination with the negative electrode in the present embodiment. There is a possibility that battery performance may be improved by combining the first to third cell configurations with the present embodiment.

[0157] Method for manufacturing composite particles

[0158] Hereinafter, an example of a method for manufacturing the above-mentioned composite particles will be described.

[0159] The method for manufacturing composite particles of the present embodiment is,

[0160] (a) preparation of positive electrode active material particles (preparation of positive electrode active material particles), and

[0161] (b) Formation of a coating film (manufacturing composite particles by forming a coating film on the surface of the positive electrode active material particles)

[0162] Includes,

[0163] The above (b) is,

[0164] (b1) forming the first layer by drying the first coating solution, and

[0165] (b2) Forming the second layer by drying the second coating solution

[0166] Includes

[0167] FIG. 2 is a schematic flowchart of a method for manufacturing composite particles according to the present embodiment. Hereinafter, the “method for manufacturing composite particles according to the present embodiment” may be abbreviated as “the present manufacturing method.” The present manufacturing method includes “(a) preparation of positive electrode active material particles” and “(b) formation of a coating film.” The present manufacturing method may further include, for example, “(c) heat treatment,” etc.

[0168] (a) Preparation of positive electrode active material particles

[0169] The present manufacturing method includes preparing positive electrode active material particles. The details of the positive electrode active material particles are as described above.

[0170] (b) Formation of coating film

[0171] The present manufacturing method comprises manufacturing composite particles by forming a coating film on the surface of positive electrode active material particles. The present manufacturing method comprises “(b1) formation of a first layer” and “(b2) formation of a second layer”.

[0172] <(b1) Formation of the first layer>

[0173] The present manufacturing method comprises forming a first layer by drying a first coating solution. A first coating solution is prepared. The first coating solution comprises a first solute and a first solvent. The first solute comprises a raw material for the first layer.

[0174] The mass of the solute may be, for example, 0.1 to 20 masses, 1 to 15 masses, or 5 to 10 masses with respect to 100 mass parts of the solvent. The first solvent may contain any component as long as the first solute can be dissolved. The first solvent may include, for example, water, alcohol, etc. The first solvent may include, for example, ion-exchanged water, ethanol, etc.

[0175] The first solute may include, for example, a lithium compound and a niobic acid compound.

[0176] Examples of lithium compounds include lithium hydroxide, lithium carbonate, and lithium nitrate.

[0177] Examples of niobic acid compounds include niobic acid [Nb2O5·3H2O].

[0178] A first mixture may be formed by mixing the first coating solution with positive electrode active material particles. The first mixture may be, for example, a suspension or a wet powder. For example, a suspension may be formed by dispersing positive electrode active material particles (powder) in the first coating solution. For example, a wet powder may be formed by spraying the first coating solution into the powder. In the present manufacturing method, any mixing device, assembly device, etc. may be used.

[0179] For example, a first layer can be formed by drying the first mixture. That is, a first layer can be formed by drying the first coating solution attached to the surface of the positive electrode active material particles. In the present manufacturing method, any drying method may be used.

[0180] For example, the first coating solution may be dried by a spray drying method. That is, a droplet is formed by spraying the suspension from a nozzle. The droplet contains positive electrode active material particles and the first coating solution. For example, a primary composite particle (intermediate product) may be formed by drying the droplet with hot air.

[0181] The solid content of the suspension for spray drying may be, for example, 1 to 50% or 10 to 30% by volume. The nozzle diameter may be, for example, 0.1 to 10 mm or 0.1 to 1 mm. The hot air temperature may be, for example, 100 to 200°C.

[0182] For example, a first mixture may be formed by a rotating fluidized bed coating device, and the first coating liquid may also be dried.

[0183] In addition, if the first layer is lithium carbonate, instead of the process of (b1) above, the first layer may be formed on the surface of the positive electrode active material particles by calcining the positive electrode active material particles under a carbon dioxide-containing atmosphere. When synthesizing the positive electrode active material, a compound such as LiOH is typically formed on its surface. Li2CO3 may be formed on the surface of the active material by reacting LiOH with carbon dioxide.

[0184] <(b2) Formation of the second layer>

[0185] The present manufacturing method comprises forming a second layer by drying a second coating solution. A second coating solution is prepared. The second coating solution comprises a second solute and a second solvent. The second solute comprises a raw material for the second layer.

[0186] The mass of the solute may be, for example, 0.1 to 20 masses, 1 to 10 masses, or 1 to 5 masses with respect to 100 mass parts of the solvent. The second solvent may contain any component as long as the second solute can be dissolved. The second solvent may include, for example, water, alcohol, etc. The second solvent may include, for example, ion-exchanged water, ethanol, etc.

[0187] The second solute may include, for example, a phosphoric acid compound. The second solute may include, for example, phosphoric anhydride (P2O5), orthophosphoric acid, pyrophosphoric acid, metaphosphoric acid [(HPO3) n It may include at least one selected from the group consisting of ], and polyphosphoric acid. The second solute may include, for example, at least one selected from the group consisting of metaphosphoric acid and polyphosphoric acid. Metaphosphoric acid and polyphosphoric acid may have long molecular chains compared to other phosphate compounds. It can be assumed that because the phosphate compound has long molecular chains, a continuous film (second layer) is easily formed. Because the second layer has continuity, for example, an improvement in the coverage rate is expected.

[0188] The second solute may further include, for example, a lithium compound. The second solute may include, for example, lithium hydroxide, lithium carbonate, lithium nitrate, etc.

[0189] The second solute may include, for example, a boric acid compound. The second solute may include, for example, at least one selected from the group consisting of orthoboric acid, metaboric acid, and tetraboric acid.

[0190] A second mixture may be formed by mixing the second coating solution and the primary composite particle (intermediate product). A second layer may be formed by drying the second mixture. That is, a second layer may be created by drying the second coating solution attached to the surface of the primary composite particle. A composite particle (secondary composite particle: final product) may be manufactured by creating the second layer. The composite particle corresponds to the composite particle (100) of FIG. 1. The second coating solution may be dried, for example, by a spray drying method, just like the first coating solution.

[0191] (c) Heat Treatment

[0192] The present manufacturing method may include performing heat treatment on primary composite particles (intermediate product) and composite particles (final product). Through heat treatment, a coating film (each layer) can be fixed. Heat treatment may also be referred to as "sintering." Any heat treatment device may be used in the present manufacturing method. The heat treatment temperature may be, for example, 150 to 300°C. The heat treatment time may be, for example, 1 to 10 hours. For example, heat treatment may be performed in air or under an inert atmosphere. Heat treatment may be performed on either the primary composite particles or the composite particles, or heat treatment may be performed on both the primary composite particles and the composite particles.

[0193] (Example)

[0194] <Composite Particle (Coated Positive Electrode Active Material)>

[0195] The composite particles (coated positive electrode active materials) of Comparative Examples 1 to 5 and Examples 1 to 6 below were prepared.

[0196] In Comparative Examples 1 to 5, composite particles (coated positive electrode active materials) having a coating film having a single-layer structure were prepared. That is, a single coating treatment was performed on the positive electrode active material particles.

[0197] Meanwhile, in Examples 1 to 6, composite particles were prepared having a coating film having a two-layer structure consisting of a first layer (inner layer) and a second layer (outer layer). That is, two coating treatments were performed on the positive electrode active material particles. The first layer comprises an alkaline oxide comprising Li and M (at least one of niobium and carbon). The second layer comprises a phosphorus compound.

[0198] Comparative Example 1

[0199] A solution was formed by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Junyaku Co., Ltd.) in 166 parts by mass of ion-exchanged water. Additionally, the molar ratio "n Li / n P A coating solution was prepared by dissolving lithium hydroxide monohydrate in the solution so that 」 becomes 0.45. In addition, n Li represents the molar concentration of Li in the coating solution. n P represents the molar concentration of P in the coating solution.

[0200] As a positive electrode active material particle, NCM (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) was prepared. A suspension was prepared by dispersing 50 parts by mass of powder of positive electrode active material particles in 40.3 parts by mass of coating solution. Powder of composite particles was prepared by supplying the suspension to a spray dryer (Product name: Mini Spray Dryer B-290, manufactured by BUCHI). The air supply temperature of the spray dryer was 200°C, and the air supply flow rate was 0.45 m³ / min. The composite particles were heat-treated in air. The heat treatment temperature was 200°C. The heat treatment time was 5 hours.

[0201] In this way, the composite particles of Comparative Example 1 were prepared.

[0202] The coating film of the composite particle of Comparative Example 1 is Li x PO y It can be considered to include (x and y are arbitrary numbers. For example, x is 0.5 and y is 3). The target thickness of the coating film is 15 nm.

[0203] Comparative Example 2

[0204] A coating solution was prepared by dissolving 10.8 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Junyaku Co., Ltd.) in 166 parts by mass of ion-exchanged water.

[0205] The composite particles of Comparative Example 2 were prepared in the same manner as Comparative Example 1, except for the other aspects.

[0206] The coating film of the composite particles of Comparative Example 2 is PO x It can be considered to include (x is an arbitrary number). The target thickness of the coating film is 15 nm.

[0207] Comparative Example 3

[0208] The composite particles of Comparative Example 3 were prepared in the same manner as Comparative Example 1, except that 50 parts by mass of the powder of the positive electrode active material particles were dispersed in 53.7 parts by mass of the coating solution.

[0209] The coating film of the composite particle of Comparative Example 3 is Li x PO y It can be considered to include (x and y are arbitrary numbers. For example, x is 0.5 and y is 3). The target thickness of the coating film is 20 nm.

[0210] Comparative Example 4

[0211] The composite particles of Comparative Example 4 were prepared in the same manner as Comparative Example 2, except that 50 parts by mass of the powder of the positive electrode active material particles were dispersed in 53.7 parts by mass of the coating solution.

[0212] The coating film of the composite particles of Comparative Example 4 is PO x It can be considered to include (x is an arbitrary number). The target thickness of the coating film is 20 nm.

[0213] Comparative Example 5

[0214] In Comparative Example 5, as the positive electrode active material particle, NCA (LiNi 0.8 Co 0.15 Al 0.05 O2) is ready.

[0215] The composite particles of Comparative Example 5 were prepared in the same manner as Comparative Example 1.

[0216] The coating film of the composite particles of Comparative Example 5 obtained in this way is a phosphate compound (Li 0.5 It can be assumed that it contains PO3). The target thickness of the coating film is 15 nm.

[0217] Example 1

[0218] (First coating solution)

[0219] 870.4 parts by mass of hydrogen peroxide (mass concentration: 30%) was added to the container. Next, 1974.8 parts by mass of ion-exchanged water and 44.2 parts by mass of niobic acid [Nb2O5·3H2O] were added to the container. Next, 87.9 parts by mass of ammonia water (mass concentration: 28%) were added to the container. A solution was formed by sufficiently stirring the contents of the container. The solution can be thought to contain a peroxo complex of Nb. Additionally, a first coating solution was prepared by dissolving 0.1 parts by mass of lithium hydroxide monohydrate (LiOH·H2O) into the solution.

[0220] (Second coating solution)

[0221] A solution was formed by dissolving 5.4 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Junyaku Co., Ltd.) in 166 parts by mass of ion-exchanged water. Additionally, the molar ratio "n Li / (n P +n E1 +n E2 A second coating solution was prepared by dissolving lithium hydroxide monohydrate in the solution so that )」 becomes 0.45.

[0222] [Formation of coating film]

[0223] (Formation of the first layer)

[0224] As a positive electrode active material particle, NCM (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2) was prepared. A suspension was prepared by dispersing 50 parts by mass of powder of positive electrode active material particles into 53.7 parts by mass of the first coating solution. Powder of primary composite particles (intermediate product) was prepared by supplying the suspension to a spray dryer (product name: Mini Spray Dryer B-290, manufactured by BUCHI). The air supply temperature of the spray dryer was 200°C, and the air supply volume was 0.45 m³ / min.

[0225] (Formation of the second layer)

[0226] A suspension was prepared by dispersing 50 parts by mass of the powder of the primary composite particles in 53.7 parts by mass of the second coating solution. The powder of the composite particles (final product) was produced by supplying the suspension to a spray dryer (product name: Mini Spray Dryer B-290, manufactured by BUCHI). The air supply temperature of the spray dryer was 200°C, and the air supply volume was 0.45 m³ / min.

[0227] (Heat treatment)

[0228] The composite particles were heat-treated in air. The heat treatment temperature was 200℃. The heat treatment time was 5 hours.

[0229] In this way, the composite particles of Example 1 were prepared.

[0230] The coating film of the composite particle of Example 1 comprises a first layer (inner layer) containing LiNbO3, and Li x PO y It can be thought of as being composed of a second layer (outer layer) containing (x and y are arbitrary numbers. For example, x is 0.5 and y is 3). The target thickness of the first layer is 5 nm, and the target thickness of the second layer is 10 nm.

[0231] Example 2

[0232] A second coating solution was prepared by dissolving 5.4 parts by mass of metaphosphoric acid (manufactured by Fujifilm Wako Junyaku Co., Ltd.) in 166 parts by mass of ion-exchanged water.

[0233] Except for that, the composite particles of Example 2 were prepared in the same manner as in Example 1.

[0234] The coating film of the composite particles of Example 2 comprises a first layer containing LiNbO3 and PO x It can be thought of as being composed of a second layer containing (x is an arbitrary number). The target thickness of the first layer is 5 nm, and the target thickness of the second layer is 10 nm.

[0235] Example 3

[0236] A first coating solution was prepared by dissolving 0.5 parts by mass of lithium carbonate (manufactured by Fujifilm Wako Junyaku Co., Ltd.) in 100 parts by mass of ion-exchanged water.

[0237] In the formation of the first layer, a suspension was prepared by dispersing 60 parts by mass of powder of positive electrode active material particles in 30.5 parts by mass of a coating solution.

[0238] Except for that, the composite particles of Example 3 were prepared in the same manner as in Example 1.

[0239] The coating film of the composite particle of Example 3 comprises a first layer containing Li2CO3 and Li x PO y It can be thought of as being composed of a second layer containing (x, y are arbitrary numbers. For example, x is 0.5 and y is 3). The target thickness of the first layer is 5 nm, and the target thickness of the second layer is 10 nm.

[0240] Example 4

[0241] 870.4 parts by mass of hydrogen peroxide (mass concentration: 30%) was added to the container. Next, 987.4 parts by mass of ion-exchanged water and 44.2 parts by mass of niobic acid [Nb2O5·3H2O] were added to the container. Next, 87.9 parts by mass of ammonia water (mass concentration: 28%) were added to the container. A solution was formed by sufficiently stirring the contents of the container. The solution can be thought to contain a peroxo complex of Nb. Additionally, a first coating solution was prepared by dissolving 0.1 parts by mass of lithium hydroxide monohydrate (LiOH·H2O) into the solution.

[0242] Except for that, the composite particles of Example 4 were prepared in the same manner as in Example 2.

[0243] The coating film of the composite particles of Example 4 comprises a first layer containing LiNbO3 and PO x It can be thought of as being composed of a second layer containing (x is an arbitrary number). The target thickness of the first layer is 10 nm, and the target thickness of the second layer is 10 nm.

[0244] Example 5

[0245] A first coating solution was prepared by dissolving 1.0 part by mass of lithium carbonate (manufactured by Fujifilm Wako Junyaku Co., Ltd.) in 100 parts by mass of ion-exchanged water.

[0246] Except for that, the composite particles of Example 5 were prepared in the same manner as in Example 3.

[0247] The coating film of the composite particle of Example 5 comprises a first layer containing Li2CO3 and Li x PO y It can be thought of as being composed of a second layer containing (x, y are arbitrary numbers. For example, x is 0.5 and y is 3). The target thickness of the first layer is 10 nm, and the target thickness of the second layer is 10 nm.

[0248] Example 6

[0249] In Example 6, as the positive electrode active material particle, NCA (LiNi 0.8 Co 0.15 Al 0.05 O2) is ready.

[0250] The composite particles of Example 6 were prepared in the same manner as in Example 3 except for the other aspects.

[0251] The coating film of the composite particle of Example 6 comprises a first layer (inner layer) containing Li2CO3, and Li x PO y It can be thought of as being composed of a second layer (outer layer) containing (x and y are arbitrary numbers. For example, x is 0.5 and y is 3). The target thickness of the first layer is 5 nm, and the target thickness of the second layer is 10 nm.

[0252] All-solid-state battery

[0253] The following materials have been prepared.

[0254] Sulfide solid electrolyte: 10LiI-15LiBr-75Li3PS4

[0255] Challenger: VGCF

[0256] Binder: SBR

[0257] Dispersion medium: heptane

[0258] Full house of serious dramas: Al Park

[0259] A positive electrode slurry was prepared by mixing the composite particles of the above examples and comparative examples, a sulfide solid electrolyte, a conductive material, a binder, and a dispersion medium. The mixing ratio of the composite particles to the sulfide solid electrolyte was “composite particles / sulfide solid electrolyte = 6 / 4 (volume ratio)”. The amount of conductive material added was 3 parts by mass per 100 parts by mass of composite particles. The amount of binder added was 3 parts by mass per 100 parts by mass of composite particles. The positive electrode slurry was sufficiently stirred by an ultrasonic homogenizer. A coating film was formed by coating the surface of the positive electrode current collector with the positive electrode slurry. The coating film was dried by a hot plate at 100°C for 30 minutes. By this, a positive electrode disc was manufactured. A disc-shaped positive electrode was cut out from the positive electrode disc. The area of ​​the positive electrode was 1 cm².

[0260] A negative electrode and a separator were prepared. The active material particles of the negative electrode were graphite. A homogeneous sulfide solid electrolyte was used between the positive electrode, the separator, and the negative electrode. A laminate was formed by stacking the positive electrode, the separator, and the negative electrode within a tubular jig. A power generation element was formed by pressing the laminate. An all-solid-state battery was formed by connecting terminals to the power generation element.

[0261] <Evaluation>

[0262] (Measurement of battery resistance)

[0263] The cell resistance (initial resistance) of the all-solid-state battery was measured. The measurement results of the cell resistance are shown in Table 1.

[0264]

[0265] From the results shown in Table 1, it can be seen that compared to the comparative example having a single-layer structure in which the coating film consists only of a layer of phosphorus compound (second layer), the cell resistance is clearly lower in the example having a laminated structure in which the coating film includes a layer of alkaline oxide (first layer) and a layer of phosphorus compound (second layer).

[0266] In addition, when the coating film is changed from a single-layer structure to a multi-layer structure to improve the durability of the coating film, the resistance of the coating film usually increases. However, in the case of the composite particles of the example having a two-layer structure, the overall resistance actually decreases, which is an unexpected result.

[0267] Structural Analysis of the Coating Film of Composite Particles

[0268] (1) STEM-EELS measurement of the positive pole

[0269] Regarding the composite particles of Example 1, the following analysis was performed to confirm that the coating film has a two-layer structure.

[0270] Regarding the positive electrode of the battery fabricated using the composite particles of Example 1 above, thinning and cross-sectioning were performed while cooling at -90°C using a concentrated ion beam (FIB) device (Hitachi Hitech, NB5000).

[0271] After cross-sectioning, the sample was transferred to a scanning transmission electron microscope (STEM) device (Hitachi High-Tech, HD-2700) using an atmosphere-blocking holder, and elemental analysis was performed using an electron energy loss spectroscopy (EELS) device (Ametec, GATAN Enfinium).

[0272] The analysis conditions for EELS are as follows.

[0273] · EELS mapping data was acquired in a 3 nm step, 47×21 pixel, 141×63 nm area.

[0274] · EELS line data accumulated in the x-direction from the mapping data was extracted.

[0275] · After background removal, the spectrum was displayed overlappingly in two ranges.

[0276] 30∼150eV: Nb-M2,3 Mn-M2,3 Co-M2,3 Li-K Ni-M2,3

[0277] 100∼400eV: P-L2,3 S-L2,3 BK Nb-M4,5 S-L1

[0278] The measurement results of STEM-EELS are shown in FIGS. 3a and 3b. In FIGS. 3a and 3b, the number following "Point" indicates the number of the measurement point when the range from the solid electrolyte on the outer side of the coating film to the positive electrode active material particle on the inner side of the coating film is measured in 3 nm increments.

[0279] From the results shown in FIGS. 3a and 3b, it can be confirmed that a coating film having a two-layer structure is formed, as shown in FIG. 3c.

[0280] (2) XPS measurement of composite particles

[0281] (2-1) Measurement Example 1

[0282] Example 3 (Coating film: Li2CO3 / PO x ) and Comparative Example 4 (coating film: PO x XPS measurements were performed on the composite particles (coated positive electrode active material). In addition, as Reference Example 1, XPS measurements were similarly performed on the composite particles formed by coating positive electrode active material particles (NCM) with a single layer coating film of Li2CO3. The measurement results are shown in Figures 4a and 4b.

[0283] In the results shown in FIGS. 4a and 4b, regarding the composite particles of Example 3, Li2CO3 and PO x From the fact that the peaks of both are confirmed, it can be seen that the coating film has a two-layer structure.

[0284] (2-2) Measurement Example 2

[0285] Example 2 (Coating film: LiNbO3 / PO x ) and Comparative Example 4 (coating film: PO x XPS measurements were performed on the composite particles (coated positive electrode active material). In addition, as Reference Example 2, XPS measurements were similarly performed on the composite particles formed by coating positive electrode active material particles (NCM) with a single layer coating film of Nb. The measurement results are shown in FIGS. 5a and 5b.

[0286] In the results shown in FIGS. 5a and 5b, regarding the composite particles of Example 2, LiNbO3 and PO x From the fact that the peaks of both are confirmed, it can be seen that the coating film has a two-layer structure.

[0287] The present embodiments and examples are illustrative in all respects. The present embodiments and examples are not limiting. The technical scope of the present disclosure includes all modifications within the equivalent meaning and scope of the claims. For example, any configuration may be derived from the present embodiments and examples, and any combination thereof is also intended from the outset.< / nca> < / ncm>

Claims

Claim 1 A positive electrode active material particle and a coating film covering at least a portion of the surface of the positive electrode active material particle are provided, wherein the coating film comprises a first layer covering at least a portion of the surface of the positive electrode active material particle and a second layer covering at least a portion of the surface of the first layer, wherein the first layer comprises an alkaline oxide comprising Li and M, where M is at least one of niobium and carbon, and the second layer comprises the general formula Li y PO x (0 <x, 0≤y<2.5)에 의해 나타내어지는 인 화합물을 포함하는,복합 입자. Claim 2 In claim 1, the alkaline oxide is a composite particle, which is lithium niobate or lithium carbonate. Claim 3 delete Claim 4 A positive electrode comprising a composite particle described in claim 1 or 2 and a sulfide solid electrolyte. Claim 5 An all-solid-state battery comprising a positive electrode, a negative electrode, and a separator as described in claim 4.

Images