Solid-state battery and manufacturing method for solid-state battery

Abstract

To provide a solid-state battery with high performance.SOLUTION: A solid-state battery 1 includes a positive electrode active material particle 41 containing Li, Co, P, and O, and a complex 42 provided on a surface 41a of the positive electrode active material particle 41 and containing LiCo(PO4), Li3(PO4), and AlPO4. For example, in a positive electrode layer 11 stacked on an electrolyte layer 13 of the solid-state battery 1, a surface covered positive electrode active material particle 40 including the positive electrode active material particle 41 and the complex 42 provided on the surface 41a thereof is applied. By the complex 42, the contact between the positive electrode active material particle 41 and a solid electrolyte 50 included in the positive electrode layer 11 or the electrolyte layer 13 and the resulting reaction are suppressed, and the increase in resistance of the positive electrode layer 11 or the solid-state battery 1 including the same is suppressed.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to a solid-state battery and a method for manufacturing a solid-state battery. [Background technology]

[0002] Regarding lithium ion secondary batteries using an electrolyte solution, a technique is known that uses coated or partially coated positive electrode active material particles in which the surfaces of lithium transition metal composite oxide particles are entirely or partially coated with Li3PO4 (Patent Document 1).

[0003] In addition, with regard to lithium ion electrochemical batteries, a technique is known in which a lithium transition metal oxide composition containing core-shell particles is used as a cathode composition, and a coating composition having LiCoPO4 is used as the shell layer (Patent Document 2). [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Patent Publication No. 2021-44099 [Patent Document 2] Special Publication No. 2016-528707 Summary of the Invention [Problem to be solved by the invention]

[0005] Meanwhile, a solid-state battery using a solid electrolyte as an electrolyte material is known as one type of lithium-ion battery. The solid-state battery includes, for example, a positive electrode layer including a positive electrode active material and a solid electrolyte, a negative electrode layer including a negative electrode active material and a solid electrolyte, and an electrolyte layer including the solid electrolyte and disposed between the positive electrode layer and the negative electrode layer.

[0006] Here, in a solid-state battery, the positive electrode active material of the positive electrode layer may be, for example, a material containing Li, Co, P, and O. However, when such a material is used for the positive electrode active material, the positive electrode active material may react with the solid electrolyte during operation of the solid-state battery, which may result in an increase in resistance or other deterioration in the performance of the solid-state battery.

[0007] In one aspect, the present invention aims to realize a high-performance solid-state battery. [Means for solving the problem]

[0008] In one embodiment, a solid-state battery is provided that includes positive electrode active material particles containing Li, Co, P, and O, and a composite provided on a surface of the positive electrode active material particles, the composite including LiCo(PO), Li(PO), and AlPO.

[0009] In another aspect, a method for producing such a solid-state battery is provided. Effect of the Invention

[0010] On the one hand, it will be possible to realize high-performance solid-state batteries. [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a diagram illustrating an example of a solid-state battery. [Diagram 2] FIG. 4 is a diagram illustrating an example of a positive electrode layer. [Diagram 3] FIG. 1 is a diagram showing an example of an X-ray diffraction measurement result. [Figure 4] FIG. 13 is a diagram showing an example of the relationship between the number of cycles and resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] FIG. 1 is a diagram for explaining an example of a solid-state battery. FIG. 1(A) schematically shows an external perspective view of the main part of an example of a solid-state battery. FIG. 1(B) schematically shows a cross-sectional view of the main part of an example of a solid-state battery. FIG. 1(B) is an example of a cross-sectional schematic view along line L1 of FIG. 1(A).

[0013] The solid-state battery 1 shown in FIGS. 1(A) and 1(B) is an example of a lithium-ion battery. The solid-state battery 1 includes a battery body 10, and a positive electrode terminal 20 and a negative electrode terminal 30 provided at both ends thereof, respectively.

[0014] As shown in FIG. 1(B), the battery body 10 has a laminate 14 in which a positive electrode layer 11 and a negative electrode layer 12 are laminated via an electrolyte layer 13, and an insulating layer 15 covering the laminate 14. Note that the number of layers of the positive electrode layer 11, the negative electrode layer 12, and the electrolyte layer 13 included in the laminate 14 is not limited to that shown in FIG. 1(B). The positive electrode layer 11 and the negative electrode layer 12 are provided so as to partially overlap each other via the electrolyte layer 13. A part (side surface) of the positive electrode layer 11 is exposed from one end surface 10a of the battery body 10, and a part (side surface) of the negative electrode layer 12 is exposed from the other end surface 10b of the battery body 10. The positive electrode terminal 20 is provided so as to cover one end surface 10a of the battery body 10 and is connected to a part of the positive electrode layer 11 exposed from the end surface 10a. The negative electrode terminal 30 is provided so as to cover the other end surface 10b of the battery body 10 and is connected to a part of the negative electrode layer 12 exposed from the end surface 10b.

[0015] The electrolyte layer 13 of the battery body 10 contains a solid electrolyte. For example, an oxide solid electrolyte is used as the solid electrolyte of the electrolyte layer 13. As the oxide solid electrolyte of the electrolyte layer 13, for example, LAGP, which is a type of NASICON (Na super ionic conductor) type (also referred to as "NASICON type") oxide solid electrolyte, is used. LAGP is an oxide solid electrolyte represented by the general formula Li 1+x Al x Ge 2-x (PO4)3 (0 < x ≦ 1).

[0016] The positive electrode layer 11 of the battery body 10 includes a positive electrode active material and a solid electrolyte. The solid electrolyte of the positive electrode layer 11 is an oxide solid electrolyte, for example, the same type of material as the solid electrolyte used in the electrolyte layer 13. The positive electrode active material of the positive electrode layer 11 is, for example, Li2CoP2O7 (also called "LCPO") or the like, which contains Li, Co, P, and O. In addition to the positive electrode active material and the solid electrolyte, the positive electrode layer 11 may further include a conductive assistant. The conductive assistant of the positive electrode layer 11 is, for example, a carbon material or the like.

[0017] The negative electrode layer 12 of the battery body 10 includes a negative electrode active material and a solid electrolyte. The solid electrolyte of the negative electrode layer 12 is an oxide solid electrolyte, for example, the same type of material as the solid electrolyte used in the electrolyte layer 13. The negative electrode active material of the negative electrode layer 12 is, for example, TiO2, Nb2O5, or the like. In addition to the negative electrode active material and the solid electrolyte, the negative electrode layer 12 may further include a conductive assistant. The conductive assistant of the negative electrode layer 12 is, for example, a carbon material, or the like.

[0018] Although not shown here, the positive electrode layer 11 and the negative electrode layer 12 may each be provided with a current collector layer so as to be in contact with each other. Such a current collector layer may contain a conductive assistant such as a carbon material. When the current collector layer contains a conductive assistant, the positive electrode layer 11 and the negative electrode layer 12 may be configured to contain or not contain a conductive assistant.

[0019] When the solid-state battery 1 is charged, lithium ions are conducted from the positive electrode layer 11 through the electrolyte layer 13 to the negative electrode layer 12 and are incorporated therein, and when the solid-state battery 1 is discharged, lithium ions are conducted from the negative electrode layer 12 to the positive electrode layer 11 through the electrolyte layer 13 and are incorporated therein. In the solid-state battery 1, charging and discharging operations are realized by such lithium ion conduction caused by predetermined current application to the positive electrode terminal 20 and the negative electrode terminal 30 connected to the positive electrode layer 11 and the negative electrode layer 12, respectively.

[0020] For the insulating layer 15, various insulating materials having insulating properties are used. The insulating properties of the insulating material used for the insulating layer 15 refer to a property that has no or sufficiently low influence on the lithium ion conduction and electron conduction in the laminate 14 including the positive electrode layer 11, the negative electrode layer 12, and the electrolyte layer 13. For the insulating layer 15, it is preferable to use a material that has low moisture and gas permeability and good sealing properties. Among them, it is preferable to use a material that has a linear expansion coefficient similar to that of each layer constituting the laminate 14 of the battery body 10 and has good adhesion to each layer for the insulating layer 15. For example, glass, ceramics, solid electrolytes, etc. are used as the insulating material for the insulating layer 15.

[0021] The positive electrode layer 11 and the negative electrode layer 12 of the battery body 10 are also referred to as "electrode layers" or "internal electrode layers." The insulating layer 15 of the battery body 10 is also referred to as a "cover layer." Of the insulating layer 15, a portion adjacent to the side of the electrolyte layer 13, a portion adjacent to the side of the positive electrode layer 11, and a portion adjacent to the side of the negative electrode layer 12 are also referred to as "embedded layers."

[0022] The solid-state battery 1 is manufactured, for example, by the following method. First, for example, a paste containing a solid electrolyte is prepared as a paste for forming the electrolyte layer 13. For example, a paste containing a positive electrode active material and a solid electrolyte or further a conductive assistant is prepared as a paste for forming the positive electrode layer 11. For example, a paste containing a negative electrode active material and a solid electrolyte or further a conductive assistant is prepared as a paste for forming the negative electrode layer 12. For example, a paste containing a glass, ceramics, or a solid electrolyte is prepared as a paste for forming the insulating layer 15.

[0023] Then, the prepared pastes are laminated by printing to form a structure as shown in FIG. 1(B), or sheets formed by printing from the pastes are laminated to form a structure as shown in FIG. 1(B). After lamination, thermocompression bonding, cutting, etc. may be performed. Then, a predetermined heat treatment, that is, a heat treatment for removing (degreasing) organic components in the paste, and further a heat treatment for baking (sintering, crystallization) the solid electrolyte, etc. are performed. For example, in order to remove the organic components, a heat treatment is performed in an air atmosphere at a temperature of about 300°C to 600°C. For example, in order to bake the solid electrolyte, etc., a heat treatment is performed in an air atmosphere or a non-oxidizing gas atmosphere at a temperature of about 600°C to 800°C, for example at 600°C. As a result, a battery body 10 having a structure as shown in FIG. 1(B), that is, a battery body 10 including a laminate 14 including a positive electrode layer 11, a negative electrode layer 12, and an electrolyte layer 13, and an insulating layer 15 covering the laminate, is formed.

[0024] The battery body 10 may include a current collector layer formed so as to be in contact with the positive electrode layer 11 and the negative electrode layer 12, respectively, and the current collector layer may be configured to include a conductive assistant. When the current collector layer includes a conductive assistant, the paste for forming the positive electrode layer 11 and the negative electrode layer 12 of the battery body 10 may be configured to include or not include a conductive assistant.

[0025] 1(B), after the battery body 10 is formed, a positive electrode terminal 20 and a negative electrode terminal 30 are formed on an end face 10a where a part of the positive electrode layer 11 is exposed and an end face 10b where a part of the negative electrode layer 12 is exposed, so as to be connected to the exposed positive electrode layer 11 and negative electrode layer 12, respectively. For example, a conductive paste containing a conductive material such as Ag is applied to the end face 10a and the end face 10b of the battery body 10 and baked, or various metals are deposited using a sputtering method, a plating method, or the like, to form the positive electrode terminal 20 and the negative electrode terminal 30.

[0026] By the above-described method, a solid-state battery 1 is manufactured, which includes a battery body 10 including a laminate 14 including the positive electrode layer 11, the negative electrode layer 12, and the electrolyte layer 13, and an insulating layer 15 covering the laminate, as well as a positive electrode terminal 20 and a negative electrode terminal 30 provided on the end face 10a and the end face 10b, respectively.

[0027] Here, in the positive electrode layer 11 of the solid battery 1, if the positive electrode active material such as LCPO contained in the positive electrode layer 11 is in contact with the solid electrolyte such as LAGP, a reaction between the positive electrode active material and the solid electrolyte may occur at the contact site with the operation of the solid battery 1. Alternatively, in the positive electrode layer 11 of the solid battery 1, if the positive electrode active material such as LCPO contained in the positive electrode layer 11 is in contact with the solid electrolyte such as LAGP contained in the electrolyte layer 13, a reaction between the positive electrode active material and the solid electrolyte may occur at the contact site with the operation of the solid battery 1. For example, if the solid battery 1 is operated under relatively severe conditions such as a high temperature cycle, the unstable positive electrode active material may react with the solid electrolyte in contact with it. If such a reaction between the positive electrode active material and the solid electrolyte occurs, the performance of the solid battery 1 may be deteriorated, such as by increasing the resistance.

[0028] In view of this, the solid-state battery 1 uses, for example, a positive electrode layer 11 as shown in the following FIG. FIG. 2 is a diagram for explaining an example of a positive electrode layer. FIG. 2(A) is a schematic cross-sectional view of a main part of an example of a positive electrode layer laminated with an electrolyte layer. FIG. 2(B) is a schematic cross-sectional view of an example of a surface-coated positive electrode active material particle included in the positive electrode layer. FIG. 2(A) is an example of a schematic cross-sectional view corresponding to the P1 portion of FIG. 1(B) above.

[0029] 2(A), the solid-state battery 1 includes an electrolyte layer 13 and a positive electrode layer 11 laminated thereon. The electrolyte layer 13 includes a solid electrolyte 50. The positive electrode layer 11 includes surface-coated positive electrode active material particles 40 and the solid electrolyte 50.

[0030] For the solid electrolyte 50 of the electrolyte layer 13 and the positive electrode layer 11, a solid electrolyte containing Li, Al, Ge, P, and O is used. For example, for the solid electrolyte 50 of the electrolyte layer 13 and the positive electrode layer 11, Li 1+x Al x Ge 2-x (PO4)3(0 < x ≦ 1), that is, LAGP is used. For the solid electrolyte 50 of the electrolyte layer 13 and the positive electrode layer 11, the same type of solid electrolyte may be used for each other, or different types of solid electrolytes may be used for each other. For the solid electrolyte 50 of the electrolyte layer 13 and the positive electrode layer 11, as long as it contains Li, Al, Ge, P, and O, a solid electrolyte containing another element may also be used.

[0031] The surface-coated positive electrode active material particles 40 of the positive electrode layer 11 include, as shown in Fig. 2(A), positive electrode active material particles 41 and a composite 42 provided on its surface 41a. The solid electrolytes 50 of the electrolyte layer 13 and the positive electrode layer 11 are sintered and crystallized by firing in the manufacturing process of the solid battery 1 as described above. The positive electrode layer 11 has a configuration in which the surface-coated positive electrode active material particles 40, that is, the positive electrode active material particles 41 provided with the composite 42 on the surface 41a, are integrated with the solid electrolyte 50 and included.

[0032] The surface-coated positive electrode active material particles 40 will be further described. The surface-coated positive electrode active material particles 40 include, as shown in Fig. 2(A) and Fig. 2(B), positive electrode active material particles 41 and a composite 42 provided on its surface 41a.

[0033] For the positive electrode active material particles 41, positive electrode active material particles containing Li, Co, P, and O are used. For example, for the positive electrode active material particles 41, Li2Co 1-x M x P 2-y A y Positive electrode active material particles containing O7 (M is at least one of Ti, V, Cr, Ni, and Fe, A is at least one of B, C, Al, Si, Ga, and Ge, 0 ≦ x < 1, 0 ≦ y ≦ 0.07) are used. As an example, for the positive electrode active material particles 41, positive electrode active material particles containing Li2CoP2O7, that is, LCPO, are used.

[0034] The composite 42 provided on the surface 41a of the positive electrode active material particle 41 includes LiCo(PO4), Li3(PO4), and AlPO4. LiCo(PO4), Li3(PO4), and AlPO4 may be included in the composite 42 in a mixed or dispersed state. LiCo(PO4), Li3(PO4), and AlPO4 may be included in the composite 42 in a localized state or a mixed state of those locally present. The contents of LiCo(PO4), Li3(PO4), and AlPO4 in the composite 42 may be the same as or different from each other. As an example, the composite 42 is provided so as to cover the entire surface 41a of the positive electrode active material particle 41. The composite 42 is provided thinly on the surface 41a of the positive electrode active material particle 41. This is because if the composite 42 becomes thick, it may cause an increase in the resistance of the positive electrode layer 11 or the solid battery 1 including the same. The composite 42 is contained in an amount of, for example, 1 wt % to 10 wt % of the plurality of positive electrode active material particles 41 (powder) contained in the positive electrode layer 11. In other words, the composite 42 is provided on the surfaces 41a of the positive electrode active material particles 41 contained in the positive electrode layer 11 with a coating amount falling within this range.

[0035] In this way, the positive electrode layer 11 includes the positive electrode active material particles 41 having the composite 42 on the surface 41a, which are integrated with the solid electrolyte 50. The positive electrode active material particles 41 containing Li, Co, P, and O such as LCPO may react relatively easily with the solid electrolyte 50 such as LAGP during a predetermined operation of the solid battery 1, for example, during operation under relatively severe conditions such as a high-temperature cycle. In contrast, the LiCo(PO4), Li3(PO4), and AlPO4 contained in the composite 42 react relatively less with the solid electrolyte 50 such as LAGP than the positive electrode active material particles 41 such as LCPO during a predetermined operation of the solid battery 1. Therefore, by providing the composite 42 on the surface 41a of the positive electrode active material particles 41, the positive electrode active material particles 41 and the solid electrolyte 50 are prevented from coming into direct contact with each other, and the positive electrode active material particles 41 and the solid electrolyte 50 are prevented from reacting with each other due to the contact. The composite 42 suppresses contact and reaction between the positive electrode active material particles 41 and the solid electrolyte 50, thereby suppressing an increase in resistance of the positive electrode layer 11 or the solid-state battery 1 including the positive electrode layer 11. This allows a high-performance solid-state battery 1 to be realized.

[0036] The positive electrode active material particles 41 are provided with the composite 42 on their surfaces 41a, thereby suppressing contact with and reaction caused by the solid electrolyte 50 contained in the positive electrode layer 11 together with the positive electrode active material particles 41. Furthermore, the positive electrode active material particles 41 are provided with the composite 42 on their surfaces 41a, thereby suppressing contact with and reaction caused by the solid electrolyte 50 contained in the electrolyte layer 13, for example, the solid electrolyte 50 present at or near the boundary with the positive electrode layer 11. This suppresses an increase in resistance of the positive electrode layer 11 or the solid battery 1 including the positive electrode layer 11, thereby achieving a high-performance solid battery 1.

[0037] Although the solid electrolyte 50 is illustrated as individual particles in FIGS. 2(A) and 2(B) for the sake of convenience, the solid electrolyte 50 does not necessarily have to be in the form of individual particles. For example, a plurality of particles of the solid electrolyte 50 may be sintered into an integrated state by a heat treatment such as firing.

[0038] The cross-sectional shapes of the positive electrode active material particles 41 and the surface-coated positive electrode active material particles 40 including the positive electrode active material particles 41 are not limited to the circular shapes shown in Fig. 2(A) and Fig. 2(B) and may be various shapes. In addition, the positive electrode layer 11 may contain a plurality of surface-coated positive electrode active material particles 40 in a state of contact with each other.

[0039] 2(A) and 2(B) show an example in which the entire surface 41a of the positive electrode active material particle 41 is covered with the composite 42. By covering the entire surface 41a of the positive electrode active material particle 41 with the composite 42, the contact between the positive electrode active material particle 41 and the solid electrolyte 50 and the reaction caused by the contact are effectively suppressed. However, the composite 42 does not necessarily have to be provided so as to cover the entire surface 41a of the positive electrode active material particle 41. The composite 42 may be provided so as to partially cover the surface 41a of the positive electrode active material particle 41, in other words, a part of the surface 41a of the positive electrode active material particle 41 may be exposed from the composite 42. Even if a part of the surface 41a of the positive electrode active material particle 41 is exposed from the composite 42, the other part of the surface 41a is covered with the composite 42, so that a certain effect of suppressing the contact between the positive electrode active material particle 41 and the solid electrolyte 50 and the reaction caused by the contact can be obtained.

[0040] The surface-coated positive electrode active material particles 40 as shown in FIG. 2(A) and FIG. 2(B) are formed, for example, by using the following method. First, a Li compound and an Al compound are attached to positive electrode active material particles 41 containing Li, Co, P, and O, such as LCPO. For example, a powder of the positive electrode active material particles 41 is immersed in a solution in which a Li compound and an Al compound are dissolved in a solvent, thereby causing the Li compound and the Al compound to adhere to the positive electrode active material particles 41.

[0041] The Li compound to be attached to the positive electrode active material particles 41 may be any of various Li compounds, such as inorganic acid salts or organic acid salts of Li. The Al compound to be attached to the positive electrode active material particles 41 may be any of various Al compounds, such as inorganic acid salts or organic acid salts of Al. As an example, a Li organic acid salt such as lithium citrate is used as the Li compound, an Al inorganic acid salt such as aluminum nitrate is used as the Al compound, and an alcohol such as ethanol is used as the solvent. The powder of the positive electrode active material particles 41 is immersed in the mixed solution and stirred. As a result, lithium citrate and aluminum nitrate are attached to the positive electrode active material particles 41 as the Li compound and Al compound.

[0042] Next, the positive electrode active material particles 41 to which the Li compound and the Al compound are attached are dried. For example, after removing a certain amount of the solvent or solution as necessary, the powder of the positive electrode active material particles 41 to which the Li compound and the Al compound are attached is dried using a spray dryer or the like.

[0043] Next, the dried positive electrode active material particles 41 to which the Li compound and Al compound are attached are subjected to heat treatment under predetermined conditions. For example, the powder of the dried positive electrode active material particles 41 to which the Li compound and Al compound are attached is placed in a container such as a crucible and heat treated in a heat treatment furnace. As an example, the heat treatment is performed in an N2 gas flow atmosphere at 200°C for 1 hour, 350°C for 1 hour, and a heating rate of 100°C / hour.

[0044] This heat treatment produces a composite 42 containing LiCo(PO4), Li3(PO4) and AlPO4 using as precursors the Li compound and Al compound attached to the positive electrode active material particles 41 containing Li, Co, P and O. For example, the composite 42 containing LiCo(PO4), Li3(PO4) and AlPO4 is produced by the reaction of the Li compound and Al compound or their decomposition products with the positive electrode active material particles 41 during the heat treatment. This produces a surface-coated positive electrode active material particle 40 as shown in Fig. 2(A) and Fig. 2(B), that is, a surface-coated positive electrode active material particle 40 in which a composite 42 containing LiCo(PO4), Li3(PO4) and AlPO4 is formed on the surface 41a of the positive electrode active material particle 41.

[0045] For example, when the above-mentioned solid-state battery 1 is manufactured, the powder of the surface-coated cathode active material particles 40 thus formed is used as the cathode active material, and a paste for forming the cathode layer 11, that is, a paste containing the cathode active material and the solid electrolyte or further a conductive assistant, is prepared. Then, such a paste for forming the cathode layer 11 and each paste for forming the anode layer 12, the electrolyte layer 13, and the insulating layer 15 prepared together with the paste are used, and a structure as shown in FIG. 1(B) is obtained, and a predetermined heat treatment (degreasing, firing) is performed to form the battery body 10. That is, the battery body 10 is formed, which includes the laminate 14 including the cathode layer 11, the anode layer 12, and the electrolyte layer 13, and the insulating layer 15 covering the laminate. It can also be said that the surface-coated positive electrode active material particle 40, in which a composite 42 containing LiCo(PO4), Li3(PO4) and AlPO4 is formed on the surface 41a of the positive electrode active material particle 41, is integrated with the solid electrolyte 50 contained in the positive electrode layer 11, or is integrated with the solid electrolyte 50 contained in the positive electrode layer 11 and the electrolyte layer 13, and is subjected to a predetermined heat treatment (degreasing, firing).

[0046] A positive electrode terminal 20 and a negative electrode terminal 30 are formed on an end face 10a where a part of the positive electrode layer 11 is exposed and an end face 10b where a part of the negative electrode layer 12 is exposed of the battery body 10 formed in this manner so as to be connected to the exposed positive electrode layer 11 and negative electrode layer 12, respectively, to manufacture a solid-state battery 1. In the solid-state battery 1 manufactured in this manner, the contact between the positive electrode active material particles 41 and the solid electrolyte 50 and the reaction caused thereby are suppressed by the composite 42. This suppresses an increase in the resistance of the positive electrode layer 11 or the solid-state battery 1 including the positive electrode layer 11, thereby realizing a high-performance solid-state battery 1.

[0047] The following describes evaluations of the above-described composite 42 and the solid-state battery 1 to which the composite 42 is applied. [Evaluation of the composite] First, the evaluation of compound 42 will be described.

[0048] For the evaluation of the composite 42, a single composite was prepared according to the above example. Specifically, a solution was prepared by dissolving the Li compound and the Al compound in a solvent, using lithium citrate as the Li compound, aluminum nitrate as the Al compound, and ethanol as the solvent. The solution was then dried using a spray dryer, placed in a crucible, and heat-treated in a heat treatment furnace in an N2 gas flow atmosphere at 200°C for 1 hour, 350°C for 1 hour, and a heating rate of 100°C / hour. In this manner, a single composite was prepared.

[0049] The prepared simple compound and a powder of positive electrode active material particles 41 containing Li, Co, P, and O, for example, LCPO powder, were mixed in a ratio of 50 wt%:50 wt%, and heat-treated in air at 600°C (heating rate 100°C / 1 hour). X-ray diffraction measurement was performed on the mixture after the heat treatment. The results are shown in FIG. 3.

[0050] FIG. 3 is a diagram showing an example of the results of X-ray diffraction measurement. Figure 3 shows the results of X-ray diffraction measurement of a mixture of the above-mentioned simple compound and LCPO powder that was heat-treated at 600°C (indicated as "Mixture after 600°C treatment" in Figure 3). Figure 3 also shows information on the positions and intensities of X-ray diffraction peaks attributable to LiCo(PO4), Li3(PO4), and AlPO4 (in Figure 3, indicated as "LiCo(PO4)," "Li3(PO4)," and "AlPO4," respectively).

[0051] It can be seen from Figure 3 that the X-ray diffraction spectrum of the "mixture after 600°C treatment" contains X-ray diffraction peaks belonging to "LiCo(PO4)", "Li3(PO4)" and "AlPO4". This confirmed that a compound containing LiCo(PO4), Li3(PO4) and AlPO4 was formed when the mixture of the simple compound and LCPO powder was heat-treated at 600°C.

[0052] Regarding surface-coated positive electrode active material particles 40 obtained by immersing positive electrode active material particles 41 in a solution in which a Li compound and an Al compound are dissolved, followed by drying and heat treatment, it can be said that the composite 42 formed on the surface 41a of the positive electrode active material particles 41 contains LiCo(PO4), Li3(PO4) and AlPO4.

[0053] [Evaluation of solid-state batteries] Next, the evaluation of the solid-state battery 1 will be described. For evaluation, solid state batteries 1 as shown in the following Comparative Example 1 and Example 1-2 were prepared.

[0054] Comparative Example 1 A laminate 14 including a positive electrode layer 11, an electrolyte layer 13, and a negative electrode layer 12 was obtained using LCPO as a positive electrode active material, LAGP as a solid electrolyte, and TiO2 as a negative electrode active material. In Comparative Example 1, LCPO particles, which are positive electrode active material particles 41, were used as the positive electrode active material of the positive electrode layer 11, and LCPO particles not provided with the composite 42 including LiCo(PO4), Li3(PO4), and AlPO4 as described above were used on the surface 41a. An insulating layer 15 was formed so as to cover the laminate 14 including such a positive electrode layer 11, and degreasing was performed at 500°C in an air atmosphere, and further sintering was performed at 600°C in an N2 atmosphere to obtain a battery body 10. Then, a positive electrode terminal 20 connected to the positive electrode layer 11 and a negative electrode terminal 30 connected to the negative electrode layer 12 were formed on the end surface 10a and the end surface 10b of the battery body 10, respectively, to obtain a solid battery 1 of Comparative Example 1.

[0055] Example 1 A laminate 14 including a positive electrode layer 11, an electrolyte layer 13, and a negative electrode layer 12 was obtained using LCPO as a positive electrode active material, LAGP as a solid electrolyte, and TiO2 as a negative electrode active material. In Example 1, a composite 42 including LiCo(PO4), Li3(PO4), and AlPO4 was provided on the surface 41a of an LCPO particle, which is a positive electrode active material particle 41, as the positive electrode active material of the positive electrode layer 11. In Example 1, the amount of the composite 42 was set to 1 wt% with respect to the positive electrode active material particle 41 (LCPO particle) group included in the positive electrode layer 11. An insulating layer 15 was formed so as to cover the laminate 14 including such a positive electrode layer 11, and degreasing was performed at 500°C in an air atmosphere, followed by firing at 600°C in an N2 atmosphere, to obtain a battery body 10. Then, a positive electrode terminal 20 connected to the positive electrode layer 11 and a negative electrode terminal 30 connected to the negative electrode layer 12 were formed on the end face 10a and the end face 10b of the battery body 10, respectively, to form the solid-state battery 1 of Example 1.

[0056] Example 2 A laminate 14 including a positive electrode layer 11, an electrolyte layer 13, and a negative electrode layer 12 was obtained using LCPO as a positive electrode active material, LAGP as a solid electrolyte, and TiO2 as a negative electrode active material. In Example 2, a composite 42 including LiCo(PO4), Li3(PO4), and AlPO4 was provided on the surface 41a of an LCPO particle, which is a positive electrode active material particle 41, as the positive electrode active material of the positive electrode layer 11. In Example 2, the amount of the composite 42 was set to 10 wt% with respect to the positive electrode active material particle 41 (LCPO particle) group included in the positive electrode layer 11. An insulating layer 15 was formed so as to cover the laminate 14 including such a positive electrode layer 11, and degreasing was performed at 500°C in an air atmosphere, and further sintering was performed at 600°C in an N2 atmosphere, to obtain a battery body 10. A positive electrode terminal 20 connected to the positive electrode layer 11 and a negative electrode terminal 30 connected to the negative electrode layer 12 were formed on the end face 10a and the end face 10b of the battery body 10, respectively, to form the solid-state battery 1 of Example 2.

[0057] [Performance evaluation] For each of the solid-state batteries 1 of Comparative Example 1 and Example 1-2, charging and discharging under predetermined conditions was defined as one cycle, and this cycle was repeated multiple times. Charging was performed by CCCV charging, in which CV (constant voltage) charging was performed when the voltage reached 3.3V during CC (constant current) charging. Discharging was performed by CC discharging. The temperature during charging and discharging was 105°C. For each of the solid-state batteries 1 of Comparative Example 1 and Example 1-2, the resistance at the start of each discharge during multiple repeated charge and discharge (cycles) was measured. The results are shown in FIG. 4.

[0058] Fig. 4 is a diagram showing an example of the relationship between the number of cycles and resistance, in which the horizontal axis represents the number of charge / discharge cycles [times], and the vertical axis represents the resistance [kΩ] at the start of discharge. As shown in FIG. 4, in the solid-state battery 1 of Comparative Example 1 in which a composite 42 was not provided on the surface 41a of the positive electrode active material particle 41 (LCPO particle), a tendency was observed in which the resistance increased with an increase in the number of cycles, and in particular, a tendency was observed in which the rate of increase in resistance became relatively large from about the fourth cycle.

[0059] 4, in the solid-state battery 1 of Example 1 in which the composite 42 set at an amount of 1 wt % was provided on the surface 41a of the positive electrode active material particles 41 (LCPO particles), a tendency for the resistance to increase with an increase in the number of cycles was observed. However, in the solid-state battery 1 of Example 1, the resistance was lower than that of the solid-state battery 1 of Comparative Example 1, and the rate of increase in resistance with an increase in the number of cycles was significantly lower than that of the solid-state battery 1 of Comparative Example 1.

[0060] As shown in FIG. 4, in the solid-state battery 1 of Example 2 in which the composite 42 set at an amount of 10 wt % was provided on the surface 41 a of the positive electrode active material particle 41 (LCPO particle), a similar tendency was observed in the change in resistance with respect to the number of cycles as in the solid-state battery 1 of Example 1.

[0061] Here, in the solid battery 1 of Example 2 in which a larger amount of the composite 42 is provided than in the solid battery 1 of Example 1, even if the number of cycles is relatively large, such as more than 6 times, the resistance increase tends to be suppressed more than in the solid battery 1 of Example 1. However, in the solid battery 1 of Example 2, when the number of cycles is relatively small, such as less than 6 times, the resistance tends to be slightly higher than that of the solid battery 1 of Example 1. From this, the following is considered. That is, as described above, the composite 42 has the effect of suppressing the contact and reaction of the positive electrode active material particles 41 with the solid electrolyte 50, but it is considered that if the amount of the composite 42 increases, it can also become a resistance layer. On the other hand, if the amount of the composite 42 increases, it is considered that the effect of suppressing the contact and reaction of the positive electrode active material particles 41 with the solid electrolyte 50 and the effect of suppressing the increase in resistance are further enhanced even if the number of cycles increases.

[0062] By providing the composite 42 containing LiCo(PO4), Li3(PO4) and AlPO4 on the surface 41a of the positive electrode active material particle 41 contained in the positive electrode layer 11, the positive electrode active material particle 41 and the solid electrolyte 50 are prevented from coming into direct contact with each other, and the positive electrode active material particle 41 and the solid electrolyte 50 are prevented from reacting with each other due to the contact, thereby preventing an increase in resistance. From FIG. 4, it can be said that the solid battery 1 containing the composite 42 in the range of 1 wt% to 10 wt% of the positive electrode active material particle 41 contained in the positive electrode layer 11 can effectively prevent an increase in resistance with an increase in the number of charge / discharge cycles in a relatively high temperature environment, compared to a battery without the composite 42. By providing a predetermined amount of the composite 42 on the surface 41a of the positive electrode active material particle 41, a high-performance solid battery 1 with a small increase in resistance and high durability can be realized. [Explanation of symbols]

[0063] 1 solid state battery 10 Battery body 10a, 10b end face 11 Positive electrode layer 12 Negative electrode layer 13 Electrolyte layer 14 Laminate 15 Insulating layer 20 Positive terminal 30 Negative terminal 40 Surface coated with positive electrode active material particles 41 Positive electrode active material particles 41a Surface 42 Complex 50 Solid Electrolyte

Claims

1. Positive electrode active material particles containing Li, Co, P, and O; LiCo(PO ４ ), Li ３ (P.O. ４ ) and AlPO ４ and [0023] A solid-state battery comprising:

2. The positive electrode active material particles are ２ Co １－ｘ M ｘ P ２－ｙ A ｙ O ７ 2. The solid-state battery according to claim 1, wherein M is at least one of Ti, V, Cr, Ni, and Fe, A is at least one of B, C, Al, Si, Ga, and Ge, and 0≦x<1, 0≦y≦0.

07.

3. The positive electrode active material particles include a plurality of the positive electrode active material particles, The solid-state battery according to claim 1 , wherein the composite is contained in an amount in the range of 1 wt % to 10 wt % with respect to the plurality of positive electrode active material particles.

4. 10. The solid-state battery of claim 1, comprising a solid electrolyte comprising Li, Al, Ge, P, and O integrated with the cathode active material particles provided with the composite.

5. preparing positive electrode active material particles containing Li, Co, P, and O; The surface of the positive electrode active material particle is coated with LiCo(PO ４ ), Li ３ (P.O. ４ ) and AlPO ４ forming a composite comprising: A method for manufacturing a solid-state battery, comprising:

6. The step of forming the composite includes: A step of attaching a Li compound and an Al compound to the positive electrode active material particles; subjecting the positive electrode active material particles to which the Li compound and the Al compound are attached to a heat treatment; The method for producing the solid-state battery according to claim 5 , comprising:

7. The method for producing a solid-state battery according to claim 5 , further comprising a step of integrating the positive electrode active material particles in which the composite is formed with a solid electrolyte containing Li, Al, Ge, P, and O, and subjecting the solid electrolyte to a heat treatment.

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