Active material composite particle and battery

Abstract

To improve coverage and durability of a coating layer in an active material composite particle in which the coating layer is provided on an active material particle.SOLUTION: The active material includes an active material particle 141 and a coating layer 142 in contact with at least a part of the surface of the active material particle. The coating layer contains a first ingredient 142a composed of an oxide-based ion conductor containing at least a crystal phase and a second ingredient 142b different from the first ingredient. The particles constituting the first component have a higher particle strength than the particles constituting the second component. The second component contains at least an amorphous phase and has a higher content ratio of the amorphous phase than the first component.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present disclosure relates to active material composite particles and a battery using the same. [Background technology]

[0002] Patent Document 1 discloses that a coating layer containing lithium niobate (LiNbO3) is formed on the surface of active material particles made of oxide-based ceramic particles to suppress reaction between the active material particles and a sulfide-based solid electrolyte. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 6380221 Summary of the Invention [Problem to be solved by the invention]

[0004] However, the LiNbO3 used for the coating layer in Patent Document 1 has high ionic conduction resistance, and the coating layer needs to be made thin to reduce its resistance. In this case, the mechanical strength of the coating layer decreases, causing it to peel off from the active material particles, reducing the coverage of the active material particles with the coating layer and making it easier for the solid electrolyte to come into contact with the active material particles.

[0005] In view of the above, an object of the present disclosure is to improve the coverage and durability of a coating layer in an active material composite particle in which a coating layer is provided on an active material particle. [Means for solving the problem]

[0006] In order to achieve the above object, the first and second aspects of the present disclosure comprise active material particles (141) and a coating layer (142) in contact with at least a portion of the surface of the active material particles, and the coating layer contains a first component (142a) made of an oxide-based ion conductor having at least a crystalline phase, and a second component (142b) different from the first component.

[0007] The crystalline first component contained in the coating layer functions as an anchor and a filler, thereby improving the adhesion and contact of the coating layer with the active material particles and improving the durability of the coating layer.

[0008] In the first aspect of the present disclosure, the particles constituting the first component have a higher particle strength than the particles constituting the second component. By including the second component in the coating layer, which has a particle strength lower than that of the first component, the second component is more easily deformed than the first component. This improves the contact between the active material particles and the coating layer, thereby improving the coverage of the active material particles with the coating layer.

[0009] In a second aspect of the present disclosure, the second component contains at least an amorphous phase and has a higher amorphous phase content than the first component. This makes the second component, which has a higher amorphous phase content, more deformable than the first component. This improves contact between the active material particles and the coating layer, thereby improving the coverage of the active material particles with the coating layer.

[0010] The reference numerals in parentheses for the above components indicate the corresponding relationship with the specific means described in the embodiments to be described later. [Brief explanation of the drawings]

[0011] [Figure 1] 1 is a cross-sectional view showing a configuration of a secondary battery according to an embodiment of the present disclosure. [Figure 2] 1A and 1B are diagrams showing specific examples of a positive electrode active material and a coating layer. [Figure 3] 1A and 1B are diagrams showing specific examples of a positive electrode active material and a coating layer. [Figure 4] 1A and 1B are diagrams showing specific examples of a positive electrode active material and a coating layer. [Figure 5] FIG. 1 is a diagram showing the crystal structure of a pyrochlore-type oxide. [Figure 6] 1A to 1C are diagrams illustrating a manufacturing process of a pyrochlore-type oxide. [Figure 7] 1 is an SEM image of the coating layer. [Figure 8] 1 is an SEM image of an active material composite particle. [Figure 9] 1 is an SEM image of an active material composite particle. [Figure 10] 1 is an SEM image of an active material composite particle. [Figure 11] FIG. 2 is a graph showing the coverage, discharge characteristics, and durability characteristics of active material composite particles of Examples and Comparative Examples. DETAILED DESCRIPTION OF THE INVENTION

[0012] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. In this embodiment, an active material composite particle 140 is used as a positive electrode active material of a secondary battery 10. The secondary battery 10 of this embodiment is a lithium ion battery in which lithium ions are conducted as conduction ions.

[0013] As shown in FIG. 1, a secondary battery 10 includes a negative electrode current collector 11, a negative electrode 12, a positive electrode current collector 13, a positive electrode 14, and an electrolyte layer 15.

[0014] An electrolyte layer 15 is sandwiched between the positive electrode 14 and the negative electrode 12. The negative electrode 12 and the electrolyte layer 15 are in contact with each other. The positive electrode 14 and the electrolyte layer 15 are in contact with each other. The negative electrode 12 and the positive electrode 14 are connected via the electrolyte layer 15. The secondary battery 10 of this embodiment is charged and discharged by lithium ions moving between the negative electrode 12 and the positive electrode 14 via the electrolyte layer 15.

[0015] Any material that can be used as a current collector for a lithium ion battery can be used for the negative electrode current collector 11 and the positive electrode current collector 13. In this embodiment, Cu is used for the negative electrode current collector 11, and Al is used for the positive electrode current collector 13.

[0016] Any material that can be used as an anode active material for a lithium ion battery can be used as the anode material constituting the anode 12. Examples of the anode material that can be used include carbon-based anode materials, oxide-based anode materials, and metal-based anode materials.

[0017] The positive electrode 14 releases lithium ions when the secondary battery 10 is charged and receives lithium ions when the secondary battery 10 is discharged. The positive electrode 14 contains active material composite particles 140. The positive electrode 14 may contain a conductive additive and a binder. The positive electrode 14 may further contain an electrolyte solution or a polymer. The active material composite particles 140 will be described in detail later.

[0018] The electrolyte layer 15 has ion conductivity and can move lithium ions between the negative electrode 12 and the positive electrode 14. In this embodiment, a solid electrolyte is used as the electrolyte material of the electrolyte layer 15. As the solid electrolyte, for example, an oxide-based solid electrolyte or a sulfide-based solid electrolyte can be used. The electrolyte layer 15 may contain a binder. Furthermore, the electrolyte layer 15 may contain an electrolytic solution or a polymer. As the electrolytic solution, for example, ethylene carbonate can be used. The electrolytic solution may be an ionic liquid. As the polymer, for example, polyethylene oxide can be used.

[0019] Next, the active material composite particle 140 of this embodiment will be described. Figures 2 to 4 show different aspects of the coating layer 142 of the active material composite particle 140.

[0020] 2 to 4, the active material composite particle 140 is a ceramic composite particle containing active material particles 141 and a coating layer 142 that coats the active material particles 141. The coating layer 142 needs to be in contact with at least a part of the surface of the active material particles 141, and needs to coat at least a part of the surface of the active material particles 141.

[0021] The active material particles 141 are positive electrode active materials. The active material particles 141 are ceramic particles that undergo an oxidation-reduction reaction, and release or accept lithium ions, which are conductive ions, through the oxidation-reduction reaction.

[0022] Any material that can be used as a positive electrode active material for a lithium ion battery can be used as the active material particles 141, such as a layered rock salt type active material, an olivine type active material, or a spinel type active material. x Co y Mn z O2(NCM), LiNi x Co y Al z Ternary positive electrode materials such as LiFePO4 (LFP), LiMnO2 (NCA) can be used. 1-x Fe x Examples of spinel active materials that can be used include LiMn2O4 (LMO), LiNi 0.5 Mn 1.5 In addition, the active material particles 141 may be LiO4 (LNMO) containing Nb. 1.3 Nb 0.3 Mn 0.4 Li2MnO containing O2 and F 1.5 F 1.5 can be used.

[0023] Coat layer 142 is a composite having multiple components including at least first component 142a and second component 142b. First component 142a and second component 142b are each particulate components. First component 142a can be referred to as a first phase, and second component 142b can be referred to as a second phase. Coat layer 142 contains at least one compound consisting of an amorphous phase.

[0024] In this embodiment, the first component 142a is a crystalline oxide-based ion conductor, and the second component 142b is at least one of an amorphous ion conductor and an amorphous electronic conductor. The amorphous ion conductor used as the second component 142b is a different type of ion conductor from the crystalline ion conductor used as the first component 142a.

[0025] Coat layer 142 may contain a third component different from first component 142a and second component 142b, or may contain three or more components. When coat layer 142 contains a third component, first component 142a may be a crystalline oxide-based ion conductor, one of second component 142b and the third component may be an amorphous ion conductor, and the other may be an amorphous electron conductor.

[0026] The oxide ion conductor constituting the first component 142a only needs to contain at least a crystalline phase, and may be entirely crystalline, or may contain both amorphous and crystalline phases. The amorphous ion conductor constituting the second component 142b only needs to contain at least an amorphous phase, and may be entirely amorphous, or may contain both amorphous and crystalline phases. When the material constituting the second component 142b contains both an amorphous phase and a crystalline phase, it is desirable that the volume ratio of the amorphous phase be equal to or greater than the volume ratio of the crystalline phase. The second component 142b has a higher amorphous phase content than the first component 142a.

[0027] The crystalline first component 142a contained in the coating layer 142 exerts an anchoring effect on the active material particles 141. Furthermore, the first component 142a acts as a filler, thereby improving the adhesion and contact of the coating layer 142 with the active material particles 141 and improving the durability of the coating layer 142.

[0028] The amorphous second component 142b contained in the coating layer 142 is more easily deformed than the crystalline first component 142a, which improves the contact between the active material particles 141 and the coating layer 142, thereby improving the coverage of the active material particles 141 with the coating layer 142.

[0029] As the crystalline oxide-based ion conductor constituting the first component 142a, for example, a pyrochlore-type oxide can be suitably used. 1.25 La 0.58 Nb2O6F(LLNOF) and Li 1.25 La 0.58 Ta2O6F(LLTOF) can be used. The pyrochlore oxide of this embodiment has high ionic conductivity. The pyrochlore oxide will be described in detail later.

[0030] The amorphous ion conductor used as the second component 142b may be, for example, amorphous LiNbO3 or amorphous LiF. The amorphous electron conductor used as the second component 142b may be, for example, amorphous carbon, such as carbon black.

[0031] 2, 3, and 4, the first component 142a and the second component 142b can be provided in various forms in the coating layer 142 of the active material composite particle 140. Form 1 in FIG. 2, Form 2 in FIG. 3, and Form 3 in FIG. 4 differ in the configuration of the first component 142a and the second component 142b inside the coating layer 142 of the active material composite particle 140. Of the forms of the active material composite particle 140 shown in FIGS. 2, 3, and 4, the random structure shown in FIG. 2 is the most preferable form from the viewpoint of increasing the contact ratio between the second component 142b and the active material 141 and the first component 142a.

[0032] The coating layer 142 of Form 1 shown in FIG. 2 has a random structure in which a first component 142a and a second component 142b are randomly mixed. The coating layer 142 is exposed as the outer surface of the active material particle 141. In Form 1, the outer surface of the active material particle 141 is in contact with the first component 142a and the second component 142b of the coating layer 142. In Form 1, the randomly structured coating layer 142 is in contact with the entire outer surface of the active material particle 141, so that the entire outer surface of the active material particle 141 is covered with the coating layer 142. The first component 142a of Form 1 is in a particulate form, and the periphery of the first component 142a is covered with the second component 142b. In the randomly structured coating layer 142, particles of the first component 142a and the second component 142b are dispersed and present in a composite dispersed state.

[0033] The coating layer 142 of Form 2 shown in FIG. 3 is configured by core-shell particles having a core-shell structure in which the outer surface of a particulate first component 142a that forms a core is coated with a second component 142b that forms a shell, and these core-shell particles are layered on the active material particles 141. In Form 2, the active material particles 141 are in contact with the second component 142b of the core-shell particles. Also, in Form 2, the entire outer surface of the active material particles 141 is covered with the coating layer 142. In Form 2, the particulate first component 142a is individually coated with the second component 142b to form core-shell particles. The coating layer 142 of the core-shell structure exists in a layered state in which the first component 142a and the second component 142b are layered on top of each other.

[0034] The coating layer 142 of Form 3 shown in Fig. 4 has a laminated structure in which a first component 142a and a second component 142b are formed in layers. In Form 3, the outer surface of the active material particle 141 is coated with the first component 142a, and the outer surface of the first component 142a is coated with the second component 142b. In Fig. 4, the first component 142a and the second component 142b are shown as being laminated in separate layers, but the second component 142b is present so as to fill in the gaps in the first component 142a.

[0035] The first component 142a is the main component of the coating layer 142. The volume ratio of the first component 142a in the coating layer 142 is equal to or greater than the volume ratios of the components other than the first component 142a, and the volume ratio of the first component 142a in the coating layer 142 is 50% or greater. In other words, the volume ratio of the first component 142a in the coating layer 142 is equal to or greater than the volume ratio of the second component 142b. When the coating layer 142 contains a third component, the volume ratio of the first component 142a in the coating layer 142 is equal to or greater than the combined volume ratio of the second component 142b and the third component. By increasing the volume ratio of the first component 142a, which has high ionic conductivity, in the coating layer 142, the ionic conductivity of the coating layer 142 can be made as high as possible.

[0036] In this embodiment, the particle strength of the active material particles 141 is higher than the particle strength of the first component 142a and the second component 142b of the coating layer 142. The crystalline first component 142a usually has a higher particle strength than the amorphous second component 142b. Therefore, the particle strengths of the active material particles 141, the first component 142a, and the second component 142b have the following relationship: active material particles 141 > first component 142a > second component 142b. The particle strengths of the active material particles 141, the first component 142a, and the second component 142b can be measured using the "Method for measuring fracture strength and deformation strength of microparticles" specified in JIS Z8844.

[0037] For example, the particle strength of the active material particles 141 is preferably in the range of 200 MPa to 250 MPa. An example of the active material particles 141 having the above particle strength is NCM. The particle strength of the first component 142a of the coating layer 142 is preferably in the range of 130 MPa to 180 MPa. An example of the first component 142a having the above particle strength is LLNOF. The particle strength of the second component 142b of the coating layer 142 is preferably 50 MPa or less. For reference, the particle strength of LLZ, which is an oxide-based ion conductor, is about 300 MPa.

[0038] Since the particle strength of the active material particles 141 is greater than the particle strength of the first component 142a and the second component 142b of the coating layer 142, when stress is applied to the active material composite particle 140, the coating layer 142 is damaged preferentially over the active material particles 141. This makes it possible to prevent the active material particles 141 from being damaged when stress is applied to the active material composite particle 140.

[0039] Furthermore, in the coating layer 142, the second component 142b, which has a particle strength lower than that of the first component 142a, is more easily deformed than the first component 142a, and can improve the contact between the active material particles 141 and the coating layer 142. This can improve the coverage of the active material particles 141 with the coating layer 142.

[0040] The particle diameter of the first component 142a of the coating layer 142 is preferably smaller than the particle diameter of the active material particles 141. When the particle diameter of the first component 142a is smaller than the particle diameter of the active material particles 141, the contact area between the particle surface of the active material particles 141 and the first component 142a can be increased, and the coverage rate of the positive electrode active material 141 by the coating layer 142 can be improved.

[0041] Furthermore, it is desirable that the first component 142a of the coating layer 142 has a larger BET specific surface area than the active material particles 141. The BET specific surface area is a specific surface area calculated by the BET method, which calculates the specific surface area by measuring the amount of gas physically adsorbed on the particle surface at low temperature. The fact that the first component 142a of the coating layer 142 has a larger BET specific surface area than the active material particles 141 also achieves the same effect as when the particle diameter of the first component 142a of the coating layer 142 is smaller than the particle diameter of the active material particles 141. In other words, the fact that the first component 142a of the coating layer 142 has a larger BET specific surface area than the active material particles 141 increases the contact area between the first component 142a and the particle surface of the active material particles 141, thereby improving the coverage of the positive electrode active material 141 with the coating layer 142.

[0042] The coating layer 142 is in contact with at least a portion of the surface of the active material particle 141. The coating layer 142 comes into contact with the active material particle 141, thereby covering at least a portion of the active material particle 141. By covering the surface of the active material particle 141, the coating layer 142 can prevent the active material particle 141 from coming into contact with other materials such as the electrolyte of the electrolyte layer 15 and reacting with them.

[0043] The coating layer 142 may cover the entire surface of the active material particle 141, or may cover only a portion of the surface of the active material particle 141. To prevent the active material particle 141 from coming into contact with and reacting with the electrolyte layer 15, etc., it is desirable that the coverage of the outer surface of the active material particle 141 with the coating layer 142 be as high as possible. In this embodiment, the coverage of the active material particle 141 with the coating layer 142 is set to 70% or more.

[0044] In terms of battery capacity, it is desirable to make the volume ratio of the active material particles 141 as high as possible in the positive electrode 14. On the other hand, if the volume ratio of the coating layer 142 is reduced, the coverage of the active material particles 141 by the coating layer 142 decreases. In this embodiment, the volume ratio of the coating layer 142 to the active material particles 141 is set within a range of 5 to 50%.

[0045] It is desirable that the thickness of the coating layer 142 be as thin as possible to increase the volume ratio of the active material particles 141. On the other hand, if the thickness of the coating layer 142 is thin, the coverage of the active material particles 141 by the coating layer 142 decreases. In this embodiment, the thickness of the coating layer 142 is set within a range of 1 to 100 nm.

[0046] At least one of the first component 142a and the second component 142b of the coating layer 142 is preferably a compound containing the same element as the element contained in the active material particles 141. Examples of elements contained in the first component 142a or the second component 142b of the coating layer 142 that are the same element as the element contained in the active material particles 141 include Li and Nb.

[0047] When LLNOF or LLTOF is used as the first component 142a and LiNbO3 is used as the second component 142b, Li is contained in both the first component 142a and the second component 142b of the coating layer 142. In this case, the inclusion of Li in the active material particles 141 and the coating layer 142 can improve lithium ion conductivity.

[0048] When LLNOF is used as the first component 142a and LiNbO3 is used as the second component 142b, Nb is contained in both the first component 142a and the second component 142b of the coating layer 142. In this case, the inclusion of Nb in the active material particles 141 and the coating layer 142 can improve the adhesion and contact of the coating layer 142 to the active material particles 141 due to diffusion between the same elements.

[0049] Next, the pyrochlore oxide used as the first component 142a will be described. The pyrochlore oxide used in this embodiment has the composition formula "Aa 2-α Ab (1+α) / 3 B2O 7-β X γ " In the above composition formula, O is an oxygen atom, and Aa, Ab, B, and X represent any element or group. Aa, Ab, and B are each different types of cations, and O and X are each different types of anion. Aa is an alkali metal cation. Pyrochlore-type oxides contain multiple cations in their composition, consisting of the alkali metal cation Aa and multiple cations other than the alkali metal cation Aa, Ab, and B. In other words, pyrochlore-type oxides contain multiple cations in their composition, including the alkali metal cation Aa.

[0050] As shown in Figure 5, pyrochlore oxides have a crystal structure in which a three-dimensional network of octahedra consisting of BO6 (NbO6, TaO6) is formed. BO6 is centered around cation B, with O at each vertex, and the vertex is shared with an adjacent BO6. In the three-dimensional network consisting of BO6, a hexagonal tunnel structure is formed in which cations A and anions X are arranged.

[0051] In the above composition formula, 0.6<α<2.0, 0<β≦1, and 0<γ≦1. Changing α changes the composition ratio of Aa and Ab, and changing β and γ changes the composition ratio of O and X.

[0052] The cation Aa is an alkali metal cation. The alkali metal represented by Aa can be any of Li, Na, K, Rb, and Cs. The cation Aa may also be Mg or H, other than alkali metals. That is, the cation Aa contains at least one selected from Li, Na, K, Rb, Cs, Mg, and H. In this embodiment, Li is used as Aa. The composition ratio (2-α) of Aa is within the range of 0<(2-α)<1.4.

[0053] The cation Ab contains at least a lanthanoid. The lanthanoid represented by Ab can be at least one of La, Ce, Nd, and Sm. In this embodiment, La is used as Ab. The composition ratio (1+α) / 3 of Ab is within the range of 0.53<(1+α) / 3<1.

[0054] The basic structure of the cation Ab is a lanthanoid, and a portion of the lanthanoid constituting Ab may be substituted with an alkaline earth metal (Ca, Mg, Sr, etc.). In the pyrochlore oxide of this embodiment, the pyrochlore structure in the above composition formula, where 0.6<α<2.0 and 0<β≦1, contains a lanthanoid, which is thought to cause defects in the crystal structure and improve ionic conductivity. In this embodiment, La is used as Ab.

[0055] In the pyrochlore oxide of this embodiment, the cation A in the general pyrochlore structure formula "A2B2O7" is a composite cation of lithium metal and lanthanoid, which is thought to contribute to the improvement of the ionic conductivity of the pyrochlore oxide.

[0056] The cation B is a metal cation different from Aa and Ab, and is a transition metal or a metal selected from Groups 13 to 15 elements. B forms an octahedron surrounded by six O atoms in the crystal. As the transition metal represented by B, a Group 4 transition metal or a Group 5 transition metal can be used, and more specifically, at least one of Nb, Ta, Ti, Zr, Hf, and V can be used. As the Group 13 element represented by B, Al, Ga, and In can be used, as the Group 14 element, Ge and Sn can be used, and as the Group 15 element, Sb and Bi can be used. In this embodiment, Nb or Ta is used as B.

[0057] The anion X is an anion that can substitute for the O atoms that constitute the pyrochlore structure. X has electronegativity and polarizability different from those of the O atoms. At least one of O, F, Cl, Br, I, S, OH, and P can be used as the anion represented by X. The composition ratio γ of X is in the range of 0<γ≦1, and at least a portion of the O atoms that constitute the pyrochlore structure are substituted with X. In this embodiment, F is used as X.

[0058] The pyrochlore oxide of this embodiment has a defect structure in which lattice defects are present in the crystal due to some of the O atoms constituting the pyrochlore structure being substituted with anions that have different electronegativity and polarizability from the O atoms. It is believed that the pyrochlore oxide of this embodiment has improved ionic conductivity due to the presence of a defect structure in the pyrochlore structure.

[0059] In the pyrochlore oxide of this embodiment, a defect structure is formed in which a portion of Aa and Ab is missing. The compositional formula of a general pyrochlore structure is "A2B2O7," and the composition ratio of the cation A is 2. In contrast, in the pyrochlore oxide of this embodiment, the composition ratios of Aa and Ab are "2-α" and "(1+α) / 3," respectively, and since 0.6<α<2.0, the sum of the composition ratios of Aa and Ab is less than 2. In other words, in the crystal structure of the pyrochlore oxide of this embodiment, at least a portion of Aa and Ab is missing. The composition ratio corresponding to the missing portions of Aa and Ab is (2α-1) / 3.

[0060] In addition to the deviation in the composition ratio, a defect structure can also be formed by making the sum of the valences of the cations consisting of Aa, Ab, and B and the anions consisting of O and X in the above composition formula negative.

[0061] Furthermore, the pyrochlore oxide of this embodiment is a mixed anion compound in which the pyrochlore structure contains multiple anions such as O and X. Because the anion represented by X is present in the BO6 coordination octahedron structure, the alkali metal Aa can be positioned in the center of the space between the BO6 coordination octahedron and the BO6 coordination octahedron, rather than moving closer to it. This is thought to be why the pyrochlore oxide of this embodiment exhibits high ionic conductivity when used in an electric field, such as in a battery.

[0062] Furthermore, since the α, β, and γ in the composition formula affect lattice defects and ionic conductivity, it is desirable to use them within appropriate ranges. Large values ​​of α, β, and γ increase the defect concentration in the crystal lattice, but if they exceed a certain amount, the concentration of the alkali metal represented by Aa decreases, resulting in a decrease in ionic conductivity. For this reason, it is desirable to control α within the range of 0.6<α<2.0, β within the range of 0<β≦1, and γ within the range of 0<γ≦1.

[0063] In this embodiment, the pyrochlore-type oxide is “Li 1.25 La 0.58 Nb2O6F(LLNOF)" or "Li1.25 La 0.58 The pyrochlore oxide used is represented by Ta2O6F(LLTOF). That is, Li is used as the cation Aa, La as the cation Ab, Nb or Ta as the cation B, and F as the anion X, with α=0.75, β=1, and γ=1.

[0064] The pyrochlore oxide of this embodiment has a surface area of ​​1×10 -3 The pyrochlore-type oxide of this embodiment has an ionic conductivity significantly higher than that of other oxide-type solid electrolytes such as garnet-type oxides.

[0065] Next, a method for producing the pyrochlore oxide of this embodiment will be described. When amorphous LiF is used as the second component 142b of the coating layer 142 in the active material composite particle 140, amorphous LiF can be formed simultaneously when the pyrochlore oxide is produced. For example, in the pyrochlore oxide production process, by adding an excess amount of LiF, a raw material for producing the pyrochlore oxide, of the pyrochlore oxide, it is possible to form amorphous LiF as the second component 142b on the surface of the pyrochlore oxide as the first component 142a.

[0066] 6 shows the method for producing a pyrochlore oxide according to this embodiment, which includes a first mixing step S10, a first firing step S11, a second mixing step S12, a forming step S13, and a second firing step S14, performed in this order.

[0067] First, a lanthanum source, a lithium source, and either a niobium source or a tantalum source are prepared as raw materials for the pyrochlore oxide, and a first mixing step S10 is performed in which these are mixed. Metal oxides or metal carbonates can be used as the lanthanum source, lithium source, niobium source, and tantalum source. In this embodiment, La2O3 is used as the lanthanum source, Li2CO3 as the lithium source, Nb2O5 as the niobium source, and Ta2O5 as the tantalum source. In the first mixing step, La2O3, Li2CO3, and either Nb2O5 or Ta2O5 are mixed in a predetermined ratio.

[0068] Next, the mixture prepared in the first mixing step is fired in the first firing step S11. In the first firing step S11, two firing steps are performed. In the first step, the mixture is pre-fired in air at 500°C for 6 hours. Pre-fire removes moisture and other substances from the mixture, increasing its reactivity. Following pre-fire, the mixture is fired in air at 1200°C for 4 hours. This produces a precursor of the target product, Li. 0.5 La 0.5 Nb2O6 or Li 0.5 La 0.5 Either Ta2O6 can be obtained.

[0069] Next, a second mixing step S12 is performed in which a fluorine source is prepared as a raw material and mixed with the precursor. Metal fluorides can be used as the fluorine source. In this embodiment, LiF and LaF3 are used as the fluorine source. LiF is a fluorine source and a lithium source, and LaF3 is a fluorine source and a lanthanum source. In the second mixing step, LiF and LaF3 are mixed with the precursor in a predetermined ratio. When amorphous LiF is used as the second component 142b of the coating layer 142, LiF is added in excess of the amount required to produce a pyrochlore-type oxide.

[0070] Next, the mixed powder of the precursor, LiF, and LaF3 is processed into a pellet shape and a molding step S13 is performed in which the mixed powder is pressed at 100 MPa, thereby molding the mixture of the precursor, LiF, and LaF3 into a pellet shape.

[0071] Next, a second firing step S14 is performed to fire the mixture of the precursor, LiF, and LaF. In the second firing step S14, the mixture of the precursor, LiF, and LaF is heated to 1000°C for 6 hours in a nitrogen atmosphere. In the second firing step S14, firing may be performed in a sealed state or in a state covered with mother powder to prevent composition deviation due to volatilization of the Li and F elements.

[0072] By cooling the product of the second firing step, the composition formula "Li 1.25 La 0.58 Nb2O6F(LLNOF)" or "Li 1.25 La 0.58 A pyrochlore-type oxide represented by Ta2O6F(LLTOF) is obtained. The pyrochlore-type oxide produced is in the form of particles. If an excess of LiF is added in the second mixing step S12, the outer surface of the pyrochlore-type oxide is coated with LiF, and particles with a core-shell structure having a core phase of pyrochlore-type oxide and a shell phase of LiF can be obtained.

[0073] The amorphization of LiF can be promoted by controlling the cooling conditions after the second firing step. Specifically, the amorphization of LiF can be promoted by increasing the cooling rate of the product, thereby increasing the volume fraction of amorphous material.

[0074] By changing the mixing ratio of La2O3, Li2CO3, Nb2O5 or Ta2O5, LiF, and LaF3 in the above manufacturing process, 2-α La (1+α) / 3 NbO 7-β F γ " or "Li 2-α La (1+α) / 3 Ta2O 7-β F γIt is possible to obtain a pyrochlore-type solid electrolyte represented by the formula: ". By changing the mixing ratio of La2O3, Li2CO3, Nb2O5 or Nb2O5, LiF, and LaF3, it is possible to adjust the α, β, and γ in the composition formula. Furthermore, part of the material sublimes during firing. Therefore, it is possible to adjust the α, β, and γ by changing the firing conditions, furnace atmosphere, and furnace size in the first and second firing steps.

[0075] Figure 7 shows SEM images of crystalline LLNOF and amorphous LiF, which are pyrochlore-type oxides. In Figure 7, the left side shows a random structure in which crystalline LLNOF and amorphous LiF are randomly mixed, and the right side shows a core-shell structure in which crystalline LLNOF is covered with amorphous LiF. The manufacturing method of this embodiment yields a composite of crystalline LLNOF and amorphous LiF shown in Figure 7.

[0076] Next, a description will be given of a method for producing the active material composite particles 140. As a method for producing the active material composite particles 140, for example, a mechanochemical method or a tumbling flow method can be used.

[0077] First, a description will be given of the case where amorphous LiNbO3 is used as the second component 142b of the coating layer 142. When amorphous LiNbO3 is used as the second component 142b of the coating layer 142, the following steps are performed in order: a first coating step in which crystalline LLNOF is coated on particulate active material particles 141 by a mechanochemical method; a second coating step in which a LiNbO3 precursor is coated on the particles produced in the first coating step by a tumbling flow method; and a heat treatment step in which amorphous LiNbO3 is obtained from the precursor.

[0078] In the first coating step, in which the active material particles 141 are coated with crystalline LLNOF particles, the active material particles and pyrochlore-type oxide particles are mixed in a predetermined ratio and subjected to a strong shear treatment at 10,000 rpm for 5 minutes using a mechanochemical device. The treatment conditions vary depending on the type of mechanochemical device. The first coating step results in composite particles in which the active material particles 141 are coated with crystalline LLNOF particles.

[0079] When coating by the mechanochemical method, it is desirable that there is a significant difference in particle size between the coating particles that make up the coating layer 142 and the particles to be coated that make up the active material particles 141. Specifically, it is desirable that the particle size of the coating particles be 1 / 10 or less of the particles to be coated.

[0080] Since the active material particles 141, which are the particles to be coated, are generally in the range of 1 to 10 μm, the coating particles must be at most 1 μm or less. However, if 1 μm coating particles are used, the thickness of the coating layer 142 increases, leading to an increase in resistance, so in order to form a coating layer 142 of 100 nm or less, it is more desirable that the coating particles be 100 nm or less.

[0081] Following the first coating step, a second coating step is performed in which the composite particles obtained in the first coating step are coated with LiNbO3 precursor using a tumbling fluidization method. In the second coating step, an alkoxide solution is prepared by mixing and stirring ethoxylithium and pentaethoxyniobium in ethanol so that the elemental ratio of lithium to niobium is 1:1. Then, using a tumbling fluidization device, a predetermined ratio of active material particles is spray-coated onto the particles obtained in the first coating step using the alkoxide solution in air at 80°C.

[0082] Next, a heat treatment process is carried out to obtain LiNbO3 from the LiNbO3 precursor. In this heat treatment process, the active material particles coated with the LiNbO3 precursor are heat treated in air at 300°C for 2 hours to obtain LiNbO3 containing an amorphous phase.

[0083] Next, a case where amorphous carbon particles (amorphous carbon) are used as the second component 142b of the coating layer 142 will be described. When carbon particles are used as the second component 142b of the coating layer 142, a first coating step is performed in which crystalline LLNOF is coated on the particulate active material particles 141 by a mechanochemical method, and a second coating step is performed in which carbon particles, which are the second component 142b, are coated on the particles produced in the first coating step by a mechanochemical method. The first coating step can be performed using the same procedure as when amorphous LiNbO3 is used as the second component 142b.

[0084] Following the first coating process, a second coating process is carried out to coat the carbon particles using a mechanochemical method. In the second coating process, the composite particles obtained in the first coating process and carbon particles are mixed in a predetermined ratio and subjected to strong shear treatment at 5000 rpm for 3 minutes using a mechanochemical device. The treatment conditions vary depending on the type of mechanochemical device.

[0085] 8, 9, and 10 are SEM images of the active material composite particle 140. Fig. 8 and Fig. 9 show SEM images of the active material composite particle 140 of the present embodiment. Fig. 10 shows an SEM image of the active material composite particle 140 of a comparative example. Fig. 8 shows a cross section of the active material composite particle 140. Fig. 9 and Fig. 10 show the appearance of the active material composite particle 140 in the upper row, and the cross section of the active material composite particle 140 in the lower row.

[0086] The active material composite particle 140 in Fig. 8 uses NCM as the active material particles 141, crystalline LLNOF as the first component 142a of the coating layer 142, and amorphous LiF as the second component 142b. The coating layer 142 has a random structure in which the first component 142a and the second component 142b are randomly mixed. The configuration of the active material composite particle 140 in Fig. 8 corresponds to Example 4 described below.

[0087] The active material composite particle 140 shown on the left side of Fig. 9 uses NCM as the active material particles 141, crystalline LLNOF as the first component 142a of the coating layer 142, and amorphous LiNbO3 as the second component 142b. The configuration of the active material composite particle 140 shown on the left side of Fig. 9 corresponds to Example 1 described below.

[0088] The active material composite particle 140 shown on the right side of Fig. 9 uses NCM as the active material particle 141, crystalline LLNOF as the first component 142a of the coating layer 142, amorphous LiF as the second component 142b, and amorphous carbon as the third component. The configuration of the active material composite particle 140 shown on the right side of Fig. 9 corresponds to Example 8 described below.

[0089] The active material composite particle 140 shown on the left side of Fig. 10 uses NCM as the active material particles 141 and amorphous LiNbO3 as the second component 142b of the coating layer 142. The configuration of the active material composite particle 140 shown on the left side of Fig. 10 corresponds to Comparative Example 1, which will be described later.

[0090] The active material composite particle 140 shown on the right side of Fig. 10 uses NCM as the active material particles 141 and crystalline LLNOF as the first component 142a of the coating layer 142. The configuration of the active material composite particle 140 shown on the right side of Fig. 10 corresponds to Comparative Example 2 described below.

[0091] Next, the coverage of the active material composite particles 140 and the discharge characteristics and durability characteristics of the secondary battery 10 using the active material composite particles 140 will be described using an example and a comparative example shown in FIG.

[0092] Examples 1 to 10 and Comparative Examples 1 to 8 differ in the type of active material particle 141 or the type of coating layer 142. The coverage in FIG. 11 is the proportion of the area of ​​the active material particle 141 that is covered with the coating layer 142 relative to the total surface area of ​​the active material particle 141. The discharge characteristics in FIG. 11 are the dischargeable time until the secondary battery 10 reaches a lower limit voltage when discharged at 5 C. The durability characteristics in FIG. 11 indicate the battery capacity retention rate of the secondary battery 10 after a cycle charge / discharge test was carried out at 60°C and 0.5 C. In FIG. 11, the coverage, discharge characteristics, and durability characteristics are shown as relative values ​​with the value of Comparative Example 1 set to 100%.

[0093] In Examples 1 to 6, 8 to 10 and Comparative Examples 1 to 8, the active material particles 141 were LiNi 0.8 Co 0.1 Mn 0.1 In Example 7, LiMnO2 (NCM811) was used as the active material particles 141. 0.6 Fe 0.4 PO4 (LMFP) is used.

[0094] In Examples 1 to 10 and Comparative Examples 2 to 3 and 5 to 8, a crystalline ion conductor is used as the first component 142a of the coating layer 142. In Comparative Examples 1 and 4, the first component 142a of the coating layer 142 is not provided.

[0095] In Examples 1 to 5, 7 to 10 and Comparative Examples 2, 6, and 7, crystalline LLNOF was used as the first component 142a of the coating layer 142. In Example 6 and Comparative Example 3, crystalline LLTOF was used as the first component 142a of the coating layer 142. In Comparative Examples 5 and 8, crystalline LLZ was used as the first component 142a of the coating layer 142.

[0096] In Examples 1 to 9 and Comparative Examples 1, 6, and 8, an amorphous ion conductor is used as the second component 142b of the coating layer 142. In Example 10, an amorphous electron conductor is used as the second component 142b of the coating layer 142. In Comparative Examples 4 and 7, a crystalline ion conductor is used as the second component 142b of the coating layer 142. In Comparative Examples 2, 3, and 5, the second component 142b of the coating layer 142 is not provided.

[0097] In Examples 1 to 3 and 9, amorphous LiNbO3 is used as the second component 142b of the coating layer 142. In Example 4, amorphous LiF is used as the second component 142b of the coating layer 142. In Example 5, LiF containing crystalline and amorphous components is used as the second component 142b of the coating layer 142. In Example 10, amorphous carbon is used as the second component 142b of the coating layer 142.

[0098] In Examples 8 and 9, the third component is contained in the coating layer 142. In Examples 8 and 9, amorphous carbon is used as the third component of the coating layer 142.

[0099] In Examples 1, 4 to 7, and 10, the volume ratio of the first component 142a to the second component 142b of the coating layer 142 was 90:10. In Example 2, the volume ratio of the first component 142a to the second component 142b of the coating layer 142 was 70:30. In Example 3, the volume ratio of the first component 142a to the second component 142b of the coating layer 142 was 50:50. In Examples 8 and 9, the volume ratio of the first component 142a to the second component 142b to the third component of the coating layer 142 was 89:8:3.

[0100] In Comparative Examples 1 and 4, the volume ratio of the first component 142a to the second component 142b of the coating layer 142 is 0:100. In Comparative Examples 2, 3, and 5, the volume ratio of the first component 142a to the second component 142b of the coating layer 142 is 100:0. In Comparative Examples 6 to 8, the volume ratio of the first component 142a to the second component 142b of the coating layer 142 is 90:10.

[0101] In Examples 1 to 10 and Comparative Examples 2, 3, and 5 to 8 having the first component 142a of the coating layer 142, the particle size of the active material particles 141 is larger than the particle size of the first component 142a of the coating layer 142.

[0102] In Examples 1 to 10 and Comparative Examples 6 and 7, the particle strengths have the relationship of active material particles 141 > first component 142a > second component 142b. In Comparative Examples 1 and 4, the particle strengths have the relationship of active material particles 141 > second component 142b. In Comparative Examples 2 and 3, the particle strengths have the relationship of active material particles 141 > first component 142a. In Comparative Example 5, the particle strengths have the relationship of first component 142a > active material particles 141. In Comparative Example 8, the particle strengths have the relationship of first component 142a > active material particles 141 > second component 142b.

[0103] 11, in Examples 1 to 10, the coverage, discharge characteristics, and durability characteristics all exceed 100%. In contrast, in Comparative Examples 2, 3, and 4 to 8, the coverage, discharge characteristics, and durability characteristics all fall below 100%. In Comparative Examples 4 and 8, the coverage exceeds 100%, but the discharge characteristics and durability characteristics fall below 100%.

[0104] In Examples 1 to 10, a high coverage was achieved because the coating layer 142 contained the second component 142b, which had a lower particle strength than the first component 142a, and the coating layer 142 contained the second component 142b, which had a higher amorphous phase content than the first component 142a.

[0105] Furthermore, in Examples 1 to 10, it is believed that high discharge characteristics were obtained because the coating layer 142 contains the first component 142a, which is an ionic conductor, and the second component 142b, which is at least one of an ionic conductor and an electronic conductor.

[0106] Furthermore, in Examples 1 to 10, it is believed that the high durability was achieved because the crystalline first component 142a contained in the coating layer 142 functions as an anchor and a filler.

[0107] According to the present embodiment described above, the coating layer 142 of the active material composite particle 140 contains the crystalline first component 142a and the second component 142b having a particle strength lower than that of the first component 142a or the amorphous second component 142b, thereby improving the durability and coverage of the coating layer 142. Peeling of the coating layer 142 from the active material particles 141 is likely to occur during kneading during electrode production or during expansion and contraction of the secondary battery 10 due to charge and discharge. In contrast, by using the active material composite particle 140 of this embodiment, the coating layer 142 can effectively prevent the active material particles 141 from reacting with other materials.

[0108] Since the coating layer 142 contains the first component 142a made of a crystalline ion conductor, the first component 142a functions as an anchor and a filler. This can improve the adhesion and contact of the coating layer 142 with the active material particles 141, and can improve the durability of the coating layer 142. Furthermore, by using a material with high ion conductivity as the first component 142a, the ion conductivity of the coating layer 142 can be improved, and the discharge characteristics can be improved.

[0109] Furthermore, since the coating layer 142 contains the second component 142b, which has a particle strength lower than that of the first component 142a, the second component 142b is more easily deformed than the first component 142a. This improves the contact between the active material particles 141 and the coating layer 142, and improves the coverage of the active material particles 141 with the coating layer 142.

[0110] Furthermore, since the coating layer 142 contains the amorphous second component 142b, the amorphous second component 142b is more easily deformed than the crystalline first component 142a. This improves the contact between the active material particles 141 and the coating layer 142, thereby improving the coverage of the active material particles 141 with the coating layer 142.

[0111] In other words, the coating layer 142 contains a crystalline first component 142a and a second component 142b that is different from the first component, and the second component 142b has a lower particle strength than the first component 142a, or the second component 142b is amorphous, thereby improving the durability and coverage of the coating layer 142.

[0112] Furthermore, in this embodiment, the particle strength of the active material particles 141 is higher than the particle strength of the first component 142a and the second component 142b of the coating layer 142. As a result, when stress is applied to the active material composite particle 140, the coating layer 142 is damaged preferentially over the active material particles 141, and damage to the active material particles 141 can be suppressed.

[0113] Furthermore, the coating layer 142 of this embodiment contains a compound (e.g., LiNbO3, LiF) made of an amorphous phase component having ion conductivity as the second component 142b, which can improve the ion conductivity of the coating layer 142 and can improve the lithium ion conductivity of the positive electrode 14.

[0114] Furthermore, according to this embodiment, the coating layer 142 contains a compound containing the same element as the element contained in the active material particles 141. For example, when the coating layer 142 contains a compound containing Li as the same element as the element contained in the active material particles 141, the lithium ion conductivity of the coating layer 142 can be improved. When the coating layer 142 contains a compound containing Nb as the same element as the element contained in the active material particles 141, the adhesion and contact of the coating layer 142 to the active material particles 141 can be improved due to diffusion between the same elements.

[0115] Furthermore, according to this embodiment, by using a pyrochlore oxide as the crystalline ion conductor constituting the first component 142a of the coating layer 142, the ionic conductivity of the coating layer 142 can be improved.

[0116] Furthermore, according to this embodiment, the particle diameter of the first component 142a of the coating layer 142 is smaller than the particle diameter of the active material particles 141. This increases the contact area between the particle surfaces of the active material particles 141 and the first component 142a, thereby improving the coverage of the positive electrode active material 141 by the coating layer 142.

[0117] Furthermore, according to this embodiment, the BET specific surface area of ​​the first component 142a of the coating layer 142 is larger than that of the active material particles 141. This also increases the contact area between the particle surfaces of the active material particles 141 and the first component 142a, thereby improving the coverage of the positive electrode active material 141 by the coating layer 142.

[0118] Furthermore, according to this embodiment, the volume ratio of the first component 142a in the coating layer 142 is equal to or greater than the volume ratios of the other components. By increasing the volume ratio of the first component 142a, which has high ionic conductivity, in the coating layer 142, the ionic conductivity of the coating layer 142 can be made as high as possible.

[0119] In this embodiment, the active material composite particles 140 are applied to the secondary battery 10. The active material particles are prone to deterioration when the secondary battery 10 is charged. Therefore, by using the active material composite particles 140 of this embodiment in the secondary battery 10, deterioration of the active material particles 141 during charging can be effectively suppressed.

[0120] Furthermore, when a sulfide-based solid electrolyte is used as the electrolyte layer 15, the active material particles 141 are prone to deterioration. Therefore, by using the active material composite particles 140 of this embodiment in a secondary battery 10 that uses a sulfide-based solid electrolyte as the electrolyte layer 15, deterioration of the active material particles 141 can be effectively suppressed.

[0121] (Other embodiments) The present disclosure is not limited to the above-described embodiments, and various modifications can be made as follows without departing from the spirit of the present disclosure. Furthermore, the means disclosed in the above-described embodiments may be combined as appropriate within the scope of feasibility.

[0122] For example, in the above embodiment, an example was described in which the active material composite particles of the present disclosure were applied to the active material of a secondary battery, but the active material composite particles of the present disclosure can also be applied to the active material of a primary battery.

[0123] In the above embodiment, the active material composite particles of the present disclosure are applied to a lithium ion battery in which the conductive ions are lithium ions, but they may also be applied to secondary batteries in which the conductive ions are different. Specifically, the active material composite particles of the present disclosure can be applied to a potassium ion battery in which potassium ions are conductive, a sodium ion battery in which sodium ions are conductive, or the like.

[0124] Furthermore, in the above embodiment, an example was described in which the active material composite particle 140 of the present disclosure is applied to the positive electrode 14 and a positive electrode active material is used as the active material particles 141 of the active material composite particle 140, but the active material composite particle of the present disclosure may also be applied to the negative electrode 12 and a negative electrode active material may be used as the active material particles of the active material composite particle.

[0125] Furthermore, in the above embodiment, an example was described in which the active material composite particles of the present disclosure were applied to a secondary battery 10 in which a negative electrode 12 was previously provided, but the active material composite particles of the present disclosure may also be applied to an anode-free battery. In an anode-free battery, in the initial state, the negative electrode 12 is not formed on the negative electrode current collector 11, and lithium ions that migrate from the positive electrode 14 during charging cause lithium metal to deposit on the negative electrode current collector 11, forming the negative electrode 12. Then, the lithium metal that constitutes the negative electrode 12 migrates to the positive electrode 14 as lithium ions during discharge.

[0126] Furthermore, in the above embodiment, an example has been described in which the active material composite particle 140 of the present disclosure is applied to an all-solid-state battery that uses a solid electrolyte as the electrolyte layer 15, but the active material composite particle 140 of the present disclosure can be applied to different types of secondary batteries.

[0127] For example, the active material composite particles 140 of the present disclosure may be applied to a liquid secondary battery provided with an electrolyte and a separator. The electrolyte may be, for example, ethylene carbonate or an ionic liquid. The separator may be, for example, a porous material.

[0128] The active material composite particles 140 of the present disclosure may also be applied to semi-solid batteries. Examples of semi-solid batteries include a gel polymer type that uses a gelled electrolyte, a clay type in which the electrolyte is kneaded into a clay-like substance, and a liquid-added type in which a small amount of electrolyte solution is impregnated into an electrode member.

[0129] The active material composite particles 140 of the present disclosure may also be applied to a bipolar battery. A bipolar battery has a structure in which multiple battery cells are stacked and connected in series, and adjacent battery cells share a current collector. In other words, the current collector in contact with the positive electrode of one adjacent battery cell is in contact with the negative electrode of the other adjacent battery cell.

[0130] The active material composite particles and batteries disclosed in this specification have the following characteristics. (Item 1) Active material particles (141); a coating layer (142) in contact with at least a portion of the surface of the active material particles, the coating layer contains a first component (142a) made of an oxide-based ion conductor including at least a crystalline phase, and a second component (142b) different from the first component; The particles constituting the first component have a particle strength higher than that of the particles constituting the second component. (Item 2) Active material particles (141); a coating layer (142) in contact with at least a portion of the surface of the active material particles, the coating layer contains a first component (141a) made of an oxide-based ion conductor including at least a crystalline phase, and a second component (142b) different from the first component; The second component contains at least an amorphous phase, and has a higher amorphous phase content than the first component. (Item 3) 3. The active material composite particle according to item 2, wherein the particles constituting the first component have a particle strength higher than that of the particles constituting the second component. (Item 4) 4. The active material composite particle according to any one of items 1 to 3, wherein the active material particles have a particle strength higher than that of the particles constituting the first component. (Item 5) 5. The active material composite particle according to any one of items 1 to 4, wherein the second component is at least one of an ion conductor and an electron conductor. (Item 6) 6. The active material composite particle according to any one of items 1 to 5, wherein the first component and the second component are present in a layered state or a dispersed state inside the coating layer. (Item 7) 7. The active material composite particle according to any one of items 1 to 6, wherein the coating layer contains a compound containing the same element as an element contained in the active material particle. (Item 8) 8. The active material composite particles according to any one of items 1 to 7, wherein the oxide-based ion conductor is a pyrochlore-type oxide. (Item 9) The composition formula of the pyrochlore oxide is Aa 2-α Ab (1+α) / 3 B2O 7-β X γ Item 9. An active material composite particle according to item 8, wherein Aa is an alkali metal, Ab contains at least a lanthanoid, B is a cation different from Aa and Ab, X is an anion that can be substituted for an O atom constituting the pyrochlore-type oxide, and in the composition formula, α is in the range of 0.6<α<2.0, β is in the range of 0<β≦1, and γ is in the range of 0<γ≦1, and the active material composite particle contains a defect structure. (Item 10) 10. The active material composite particles according to any one of items 1 to 9, wherein the particles constituting the first component have a particle size smaller than that of the active material particles. (Item 11) 11. The active material composite particles according to any one of items 1 to 10, wherein the particles constituting the first component have a higher BET specific surface area than the active material particles. (Item 12) 12. The active material composite particle according to any one of items 1 to 11, wherein the volume ratio of the first component in the coating layer is equal to or greater than the volume ratio of components other than the first component in the coating layer. (Item 13) 4. The active material composite particle according to item 1 or 3, wherein the particle strength of the particles constituting the first component is in the range of 130 MPa to 180 MPa, and the particle strength of the particles constituting the second component is 50 MPa or less. (Item 14) a positive electrode (14) having a positive electrode active material and a negative electrode (12) having a negative electrode active material; 14. A battery in which the active material composite particle according to any one of items 1 to 13 is used as at least one of the positive electrode active material and the negative electrode active material. [Explanation of symbols]

[0131] 12 Negative electrode 14 Positive electrode 140 Active material composite particles 141 Active material particles 142 Coat layer 142a 1st component 142b Second component

Claims

1. Active material particles (141), a coating layer (142) in contact with at least a portion of the surface of the active material particles; the coating layer contains a first component (142a) made of an oxide-based ion conductor including at least a crystalline phase, and a second component (142b) different from the first component; The particles constituting the first component have a particle strength higher than that of the particles constituting the second component.

2. Active material particles (141), a coating layer (142) in contact with at least a portion of the surface of the active material particles; the coating layer contains a first component (141a) made of an oxide-based ion conductor including at least a crystalline phase, and a second component (142b) different from the first component; The second component contains at least an amorphous phase, and has a higher amorphous phase content than the first component.

3. 3. The active material composite particle according to claim 2, wherein the particles constituting the first component have a particle strength higher than that of the particles constituting the second component.

4. 3. The active material composite particle according to claim 1, wherein the active material particles have a particle strength higher than that of the particles constituting the first component.

5. 3. The active material composite particle according to claim 1, wherein the second component is at least one of an ion conductor and an electron conductor.

6. 3. The active material composite particle according to claim 1, wherein the first component and the second component are present in a layered state or a dispersed state inside the coating layer.

7. 3. The active material composite particle according to claim 1, wherein the coating layer contains a compound containing the same element as an element contained in the active material particle.

8. 3. The active material composite particle according to claim 1, wherein the oxide-based ion conductor is a pyrochlore-type oxide.

9. The composition formula of the pyrochlore oxide is Aa ２－α Ab （１＋α）／３ B ２ O ７－β X γ wherein Aa is an alkali metal, Ab contains at least a lanthanoid, B is a cation different from Aa and Ab, X is an anion that can be substituted for an O atom that constitutes the pyrochlore-type oxide, and in the composition formula, α is in the range of 0.6<α<2.0, β is in the range of 0<β≦1, and γ is in the range of 0<γ≦1, and the active material composite particle according to claim 8 contains a defect structure.

10. 3. The active material composite particle according to claim 1, wherein the particles constituting the first component have a particle size smaller than that of the active material particles.

11. 3. The active material composite particle according to claim 1, wherein the particles constituting the first component have a larger BET specific surface area than the active material particles.

12. 3. The active material composite particle according to claim 1, wherein a volume ratio of the first component in the coating layer is equal to or greater than a volume ratio of components other than the first component in the coating layer.

13. 4. The active material composite particle according to claim 1, wherein the particle strength of the particles constituting the first component is in the range of 130 MPa to 180 MPa, and the particle strength of the particles constituting the second component is 50 MPa or less.

14. The battery comprises a positive electrode (14) having a positive electrode active material and a negative electrode (12) having a negative electrode active material, A battery comprising the active material composite particle according to claim 1 or 2 as at least one of the positive electrode active material and the negative electrode active material.

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