Lithium ion battery and method for manufacturing lithium ion battery

Abstract

The invention relates to a lithium ion battery and a method for manufacturing a lithium ion battery. The purpose of the present invention is to suppress an increase in the resistance of a battery when a battery is configured using a positive electrode active material having a Li-defect O2-type structure. This battery has a positive electrode active material layer containing a sulfide solid electrolyte and a positive electrode active material having a Li-defect O2-type structure, an electrolyte layer, and a negative electrode active material layer. The Raman spectrum of the positive electrode active material layer satisfies the relationships IR1 / IR < 2 > < = 0.20 and IR3 / IR < 2 > < = 0.20 (IR1: peak intensity derived from P2S6 < 4-> in the Raman spectrum, IR < 2 >: peak intensity derived from PS43 <-> in the Raman spectrum, and IR < 3 >: peak intensity derived from S-S in the Raman spectrum).

Description

Technical Field

[0001] The present application discloses a lithium ion battery and a method for manufacturing the lithium ion battery. Background Art

[0002] Patent Document 1 discloses a positive electrode active material having an O2-type structure (O: Octahedral) as a positive electrode active material for an all-solid-state battery. The positive electrode active material having an O2-type structure is obtained by exchanging at least a portion of Na in an oxide containing Na having a P2-type structure with Li. The positive electrode active material thus obtained has an O2-type structure of Li-deficient type. That is, the composition ratio of Li to O constituting the O2-type structure, Li / O, is usually less than 0.5.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2022-085829 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Lithium-ion batteries using positive electrode active materials having a Li-deficient O2-type structure still have room for improvement in terms of resistance.

[0008] Means for solving problems

[0009] The present application discloses the following multiple solutions as means for solving the above-mentioned problems.

[0010] <Option 1>

[0011] A lithium-ion battery having a positive electrode active material layer, an electrolyte layer and a negative electrode active material layer, wherein the positive electrode active material layer comprises a positive electrode active material having a Li-deficient O2-type structure and a sulfide solid electrolyte, and the Raman spectrum of the positive electrode active material layer satisfies the following relations (1) and (2):

[0012] I R1 / I R2 ≤0.20···(1)

[0013] I R3 / I R2 ≤0.20···(2)

[0014] I R1 : The Raman spectrum from P 2 S 6 4- The peak intensity

[0015] IR2 : The Raman spectrum from PS 4 3- The peak intensity

[0016] I R3 : The peak intensity from SS in the Raman spectrum.

[0017] <Option 2>

[0018] The lithium ion battery according to scheme 1, wherein the XPS spectrum of the positive electrode active material layer satisfies the following relations (3) and (4):

[0019] I X1 / I X2 ≤1.20···(3)

[0020] I X3 / I X4 ≤1.60···(4)

[0021] I X1 : The peak intensity from PSP in the XPS spectrum of S2p

[0022] I X2 : The XPS spectrum of S2p from PS 4 3- The peak intensity

[0023] I X3 : Regarding the XPS spectrum of P2p, the x S 4-x 3- The peak intensity

[0024] I X4 : The XPS spectrum of P2p from PS 4 3- The peak intensity.

[0025] <Option 3>

[0026] The lithium ion battery according to claim 1 or 2, wherein, when the entire solid content contained in the positive electrode active material layer is set to 100 mass %, the content of the positive electrode active material is 40 mass % or more and less than 100 mass %, and the content of the sulfide solid electrolyte is greater than 0 mass % and less than 60 mass %.

[0027] <Option 4>

[0028] The lithium ion battery according to any one of embodiments 1 to 3, wherein the positive electrode active material comprises Li a Na b Mn x-pNi y-q Co z-r M p+q+r O 2 The chemical composition represented by the invention is as follows, wherein 0<a<1.00, 0≤b≤0.20, x+y+z=1, and 0≤p+q+r<0.17, and the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W.

[0029] <Option 5>

[0030] The lithium ion battery according to any one of aspects 1 to 4, wherein the electrolyte layer contains a solid electrolyte.

[0031] <Option 6>

[0032] A method for manufacturing a lithium-ion battery comprises: mixing a positive electrode active material having a Li-deficient O2-type structure and a sulfide solid electrolyte to obtain a positive electrode composite; and pressing the positive electrode composite at a temperature of less than 165° C. to obtain a positive electrode active material layer.

[0033] Effects of the Invention

[0034] The lithium ion battery of the present disclosure has low electrical resistance. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 An example of the structure of a lithium ion battery is schematically shown.

[0036] Figure 2 An example of a flow of a method for producing a lithium ion battery is shown.

[0037] Figure 3 The Raman spectra of each positive electrode active material layer of Examples 1 to 2, Comparative Examples 1 to 3, and Reference Example are shown.

[0038] Figure 4 The XPS spectra (P2p) of the positive electrode active material layers of Examples 1 to 2, Comparative Examples 1 to 3, and Reference Example are shown.

[0039] Figure 5 The XPS spectra (S2p) of the positive electrode active material layers of Examples 1 to 2, Comparative Examples 1 to 3, and Reference Example are shown.

[0040] Description of Reference Numerals

[0041] 100 Lithium-ion battery

[0042] 10 Positive electrode active material layer

[0043] 11 Positive electrode active material with Li-deficient O2-type structure

[0044] 12 Sulfide Solid Electrolyte

[0045] 15. Positive electrode composite material

[0046] 20 Electrolyte layer

[0047] 30 Negative electrode active material layer

[0048] 40 positive electrode collector

[0049] 50 Negative electrode collector DETAILED DESCRIPTION

[0050] An embodiment of the lithium ion battery and the method for manufacturing the same according to the present disclosure will be described below. However, the lithium ion battery and the method for manufacturing the same according to the present disclosure are not limited to the embodiment described below.

[0051] 1. Lithium-ion battery

[0052] like Figure 1 As shown, a lithium ion battery 100 according to one embodiment includes a positive electrode active material layer 10, an electrolyte layer 20, and a negative electrode active material layer 30. The positive electrode active material layer 10 includes a positive electrode active material having a Li-deficient O2-type structure and a sulfide solid electrolyte. The Raman spectrum of the positive electrode active material layer 10 satisfies the following relationships (1) and (2):

[0053] I R1 / I R2 ≤0.20···(1)

[0054] I R3 / I R2 ≤0.20···(2)

[0055] I R1 : The Raman spectrum from P 2 S 6 4- The peak intensity

[0056] I R2 : The Raman spectrum from PS 4 3- The peak intensity

[0057] I R3 : The peak intensity from SS in the Raman spectrum.

[0058] The lithium ion battery 100 satisfying the relations (1) and (2) has low resistance.

[0059] 1.1 Positive electrode active material layer

[0060] The positive electrode active material layer 10 includes a sulfide solid electrolyte and a positive electrode active material having a Li-deficient O2-type structure. The positive electrode active material layer 10 may optionally include other positive electrode active materials, other electrolytes, conductive aids, adhesives, etc. In addition, the positive electrode active material layer 10 may include various additives. The respective contents of the positive electrode active material, electrolyte, conductive aid, adhesive, etc. in the positive electrode active material layer 10 can be appropriately determined according to the target battery performance. For example, when the solid component contained in the positive electrode active material layer 10 is set to 100% by mass as a whole, the content of the positive electrode active material having a Li-deficient O2-type structure can be 40% by mass or more and less than 100% by mass, and the content of the sulfide solid electrolyte can be more than 0% by mass and less than 60% by mass. The content of the positive electrode active material with a Li-deficient O2-type structure may be 50% by mass or more, 60% by mass or more, 70% by mass or more, or 80% by mass or more, and may be 90% by mass or less, and the content of the sulfide solid electrolyte may be 10% by mass or more, and may be 50% by mass or less, 40% by mass or less, 30% by mass or less, or 20% by mass or less. These lower limits and upper limits may be arbitrarily combined.

[0061] 1.1.1 Positive electrode active material with Li-deficient O2-type structure

[0062] The positive electrode active material layer 10 includes a positive electrode active material having a Li-deficient O2-type structure (belonging to the space group P63mc). In other words, the positive electrode active material layer 10 includes an oxide containing Li having a Li-deficient O2-type structure as a positive electrode active material. The so-called "Li-deficient type" means that the composition ratio Li / O of Li and O in the chemical composition of the positive electrode active material is less than 0.5 (for example, "a" in the composition formula described later is less than 1.0).

[0063] 1.1.1.1 Crystal structure

[0064] The positive electrode active material involved in one embodiment may have a crystal structure other than the O2 type structure while having an O2 type structure. As a crystal structure other than the O2 type structure, for example, the T#2 type structure (belonging to the space group Cmca) formed when Li is inserted into the O2 type structure / Li is separated from the O2 type structure, and the O6 type structure (belonging to the space group R-3m, the c-axis length is greater than 2.5nm and less than 3.5nm, typically greater than 2.9nm and less than 3.0nm, which is different from the O3 type structure also belonging to the space group R-3m) and the like can be listed. For any crystal structure, it can be a Li-deficient crystal structure. The positive electrode active material involved in one embodiment may have an O2 type structure as the main phase, and may also have a crystal structure other than the O2 type structure (for example, an O6 type structure) as the main phase. The positive electrode active material involved in one embodiment may change the crystal structure that becomes the main phase according to its charge and discharge state.

[0065] 1.1.1.2 Microcrystal

[0066] The positive electrode active material having a Li-deficient O2-type structure may be a single crystal consisting of one microcrystal, or a polycrystal having a plurality of microcrystals. For example, the surface of the positive electrode active material involved in one embodiment may be composed of a plurality of microcrystals. In other words, the positive electrode active material may have a structure in which a plurality of microcrystals are connected to each other on its surface. In the case where the surface of the positive electrode active material is composed of a plurality of microcrystals, there are grain boundaries on the surface. Among them, the grain boundaries sometimes become the entrance and exit of the intercalation. That is, in the case where the positive electrode active material is a polycrystal having a plurality of microcrystals, it is possible to expect the effect of increasing the entrance and exit of the intercalation, thereby reducing the reaction resistance, shortening the movement distance of lithium ions, thereby reducing the diffusion resistance, and reducing the absolute amount of expansion and contraction during charge and discharge, thereby making it difficult to produce cracks. The size of the microcrystal may be large or small. It is believed that when the size of the microcrystal is small, the grain boundaries increase, and it is easy to exert the above-mentioned favorable effects. For example, if the diameter of the microcrystal constituting the positive electrode active material is less than 1 μm, it is easy to obtain higher performance. Furthermore, "crystals" and "crystal diameters" can be obtained by observing the surface of the positive electrode active material using a scanning electron microscope (SEM) or a transmission electron microscope (TEM). That is, when observing the surface of the positive electrode active material and observing a closed area surrounded by grain boundaries, the area is regarded as a "crystal". For the crystallite, the maximum Feret diameter is calculated and regarded as the "crystal diameter". Furthermore, if the positive electrode active material is composed of single crystal particles, the particle itself can be said to be a crystallite, and the maximum Feret diameter of the particle is the "crystal diameter". If the diameter of the crystallite of the positive electrode active material is less than 1 μm, it is easy to exert higher performance. The crystallites constituting the positive electrode active material may have a first surface exposed on the surface of the oxide, and the first surface may be planar. That is, the surface of the positive electrode active material may have a structure in which multiple planes are connected. As described later, when producing a Na-containing oxide that is a raw material of a Li-containing oxide as a positive electrode active material, crystallites having a planar first surface are easily obtained by growing crystallites on the surface of particles until one crystallite is linked to another.

[0067] 1.1.1.3 Chemical composition

[0068] The positive electrode active material having a Li-deficient O2-type structure may, for example, contain at least one element of Mn, Ni and Co, Li, and O as constituent elements. Among them, when the positive electrode active material contains at least Li, Mn, one or both selected from Ni and Co, and O as constituent elements, in particular, when at least Li, Mn, Ni, Co, and O are contained as constituent elements, higher performance is easily obtained.

[0069] The positive electrode active material having a Li-deficient O2-type structure may have a Li a Nab Mn x-p Ni y-q Co z-r M p+q+r O 2 (wherein, 0<a<1.00, 0≤b≤0.20, x+y+z=1 and 0≤p+q+r<0.17, element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W). In the case where the positive electrode active material has such a chemical composition, it is easy to maintain the O2 type structure. In the above chemical composition, a is greater than 0, and may be greater than 0.10, greater than 0.20, greater than 0.30, greater than 0.40, greater than 0.50 or greater than 0.60, and is less than 1.00, and may be less than 0.90, less than 0.80 or less than 0.70. In the above chemical composition, b is greater than 0, and may be greater than 0.01, greater than 0.02 or greater than 0.03, and is less than 0.20, and may be less than 0.15 or less than 0.10. In addition, x is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. In addition, y is 0 or more, and may be 0.10 or more, or 0.20 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.20 or less. In addition, z is 0 or more, and may be 0.10 or more, 0.20 or more, or 0.30 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less. Element M contributes little to charge and discharge. In this regard, in the above-mentioned chemical composition, by p+q+r being less than 0.17, it is easy to ensure a high charge and discharge capacity. p+q+r may be less than 0.16, less than 0.15, less than 0.14, less than 0.13, less than 0.12, less than 0.11 or less than 0.10. On the other hand, by including element M, the O2 type structure is easily stabilized. In the above-mentioned chemical composition, p+q+r is greater than 0, and may be greater than 0.01, greater than 0.02, greater than 0.03, greater than 0.04, greater than 0.05, greater than 0.06, greater than 0.07, greater than 0.08, greater than 0.09 or greater than 0.10. The composition of O is approximately 2, but is not limited to exactly 2.0, and is indefinite (variable).

[0070] 1.1.1.4 Shape

[0071] As described later, the positive electrode active material having a Li-deficient O2-type structure can be obtained by replacing Na of an oxide containing Na with a P2-type structure with Li. Among them, the P2-type structure is a hexagonal system, the diffusion coefficient of Na ions is large, and it is easy to crystallize and grow in a specific direction. In particular, as a transition metal element constituting the P2-type structure, when at least one of Mn, Ni and Co is included, it is easy to crystallize and grow into a plate in a specific direction. Therefore, the oxide containing Na with a P2-type structure usually becomes a plate-like particle with a large aspect ratio in which the growth direction of the crystal is biased toward a specific direction. The positive electrode active material involved in one embodiment may be a product obtained based on such a plate-like oxide particle containing Na, or, as described later, may be a product obtained based on a spherical oxide particle containing Na. That is, with respect to the shape of the positive electrode active material, it may be a plate-like particle or a spherical particle. In the case where the positive electrode active material is a spherical particle, due to the reduction in the crystallite size, the reaction resistance is reduced, and the diffusion resistance inside the particle is easily reduced. Furthermore, in the case of application to batteries, it is believed that by spheroidization, the curvature is reduced and the lithium ion conduction resistance is reduced. As a result, for example, the rate characteristics are improved and the reversible capacity is easily increased. Furthermore, in this application, the so-called "spherical particles" refer to particles with a circularity of 0.80 or more. The circularity of the particles may be greater than 0.81, greater than 0.82, greater than 0.83, greater than 0.84, greater than 0.85, greater than 0.86, greater than 0.87, greater than 0.88, greater than 0.89 or greater than 0.90. The circularity of the particles is expressed by 4πS / L 2 Definition. Wherein, S is the orthographic projection area of ​​the particle, and L is the perimeter of the orthographic projection image of the particle. The circularity of the particle can be obtained by observing the appearance of the particle using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an optical microscope.

[0072] The positive electrode active material having a Li-deficient O2-type structure may be, for example, a solid particle, a hollow particle, or a particle having voids. There is no particular limitation on the size of the positive electrode active material particles, and it is believed that the smaller the size, the more advantageous it is. For example, the average particle size (D50) of the positive electrode active material particles may be greater than 0.1 μm and less than 10 μm, greater than 1.0 μm and less than 8.0 μm, or greater than 2.0 μm and less than 6.0 μm. It should be noted that the average particle size (D50) is the particle size (D50, median diameter) at the cumulative value of 50% in the volume-based particle size distribution obtained by the laser diffraction and scattering method.

[0073] 1.1.1.5 Method for manufacturing positive electrode active material having Li-deficient O2-type structure

[0074] The positive electrode active material having a Li-deficient O2-type structure can be manufactured, for example, by the following method. That is, the manufacturing method of the positive electrode active material according to one embodiment includes:

[0075] S1: obtaining a precursor (for example, a precursor containing at least one element of Mn, Ni and Co),

[0076] S2: coating the surface of the precursor with a Na source to obtain a composite,

[0077] S3: calcining the composite to obtain an oxide containing Na having a P2 type structure, and

[0078] S4: Ion-exchanging at least a portion of Na in the Na-containing oxide with Li, thereby obtaining a Li-containing oxide having an O2 type structure.

[0079] Wherein, the S3 includes:

[0080] S3-1: the composite is subjected to preliminary calcination at a temperature of 300° C. or higher and lower than 700° C. for 2 hours or higher and 10 hours or lower.

[0081] S3-2: After the preliminary calcination, the composite is subjected to main calcination at a temperature of 700° C. to 1100° C. for 30 minutes to 48 hours, and

[0082] S3-3: Following the main sintering, the composite is heated from a temperature T above 200°C to 1 Rapid cooling to a temperature below 100°C 2 .

[0083] In S1, a precursor containing at least one element of Mn, Ni and Co is obtained. The precursor may contain at least Mn, and one or both selected from Ni and Co, and may contain at least Mn, Ni and Co. The precursor may be a salt containing at least one element of Mn, Ni and Co. For example, the precursor may be at least one of carbonate, sulfate, nitrate and acetate. Alternatively, the precursor may be a compound other than a salt. For example, the precursor may be a hydroxide. The precursor may be a hydrate. The precursor may be a combination of multiple compounds. The precursor may be in various shapes. For example, the precursor may be in the form of particles, or may be spherical particles as described later. There is no particular limitation on the particle size of the particles formed by the precursor.

[0084] In S1, an ion source that can form a precipitate with transition metal ions in an aqueous solution and a transition metal compound containing at least one element of Mn, Ni and Co can be used to obtain a precipitate as the above-mentioned precursor by a coprecipitation method. Thus, spherical particles as a precursor can be easily obtained. "An ion source that can form a precipitate with transition metal ions in an aqueous solution" can be, for example, at least one selected from sodium salts such as sodium carbonate and sodium nitrate, sodium hydroxide and sodium oxide. The transition metal compound can be the above-mentioned salt, hydroxide, etc. containing at least one element of Mn, Ni and Co. Specifically, in S1, after the ion source and the transition metal compound are made into solutions respectively, each solution is dripped and mixed, thereby obtaining a precipitate as a precursor. At this time, as a solvent, for example, water is used. At this time, as an alkali, various sodium compounds can be used, and in addition, an ammonia solution can be added to adjust the alkalinity. In the case of the coprecipitation method, for example, an aqueous solution of a transition metal compound and an aqueous solution of sodium carbonate can be prepared, and each aqueous solution is dripped and mixed, thereby obtaining a precipitate as a precursor. Alternatively, a sol-gel method can also be used to obtain a precursor. In particular, according to the coprecipitation method, spherical particles as a precursor can be easily obtained.

[0085] In S1, the precursor may contain element M. Element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W. These elements M, for example, have the function of stabilizing P2-type structure and O2-type structure. There is no particular limitation on the method for obtaining the precursor containing element M. In the case where the precursor is obtained by coprecipitation method in S1, for example, an aqueous solution of a transition metal compound containing at least one of Mn, Ni and Co, an aqueous solution of sodium carbonate, and an aqueous solution of a compound of element M are prepared, and each aqueous solution is dripped and mixed to obtain a precursor containing at least one of Mn, Ni and Co and also containing element M. Alternatively, in the manufacturing method of the present disclosure, element M may not be added in S1, and element M may be doped during Na-doping sintering in S2 and S3 described later.

[0086] In S2, the surface of the precursor obtained by S1 is coated with a Na source to obtain a composite. The Na source can be a salt containing Na such as carbonates and nitrates, or a compound other than salts such as sodium oxide and sodium hydroxide. In S2, the amount of the Na source coated on the surface of the precursor can be determined by adding the Na disappearance portion during subsequent calcination.

[0087] In S2, there is no particular limitation on the coverage of the Na source on the surface of the precursor. For example, in S2, the above-mentioned composite can be obtained by covering more than 40 area %, more than 50 area %, more than 60 area % or more than 70 area % of the surface of the above-mentioned precursor with a Na source. Wherein, in the case where the precursor obtained by S1 is a spherical particle, and the composite obtained by S2 is obtained by covering more than 40 area % of the surface of the precursor with the Na source, in S3 described later, the oxide containing Na with a P2 type structure tends to become spherical particles. If the coverage of the Na source is small, then when the composite is fired, on the surface of the composite, P2 type crystals tend to grow, and the oxide containing Na tends to become plate-like. In the case where the coverage of the Na source is large, when the composite is fired, the crystallites of the P2 type crystals tend to become smaller, and the oxide containing Na tends to become spherical particles corresponding to the shape of the precursor.

[0088] In S2, the method for coating the surface of the above-mentioned precursor with a Na source is not particularly limited. As mentioned above, when more than 40% by area of ​​the surface of the precursor is coated with a Na source, various methods can be cited as the method. For example, a tumbling flow coating method and a spray drying method can be cited. That is, a coating solution in which the Na source is dissolved is prepared, and the surface of the precursor is dried while contacting the coating solution or after contact. By adjusting the conditions (temperature, time, number of times, etc.) of the coating, more than 40% by area of ​​the surface of the precursor can be coated with a Na source.

[0089] In S2, for the precursor, the M source can be coated together with the Na source (the Na source and the M source can be coated simultaneously). For example, in S2, the precursor obtained by S1, the Na source, and the M source containing at least one element M selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W can be mixed to obtain a composite. The M source can be, for example, a salt containing the element M such as a carbonate or a sulfate, or a compound other than a salt such as an oxide or a hydroxide. The amount of the M source relative to the precursor can be determined according to the chemical composition of the oxide containing Na after sintering.

[0090] In S3, the composite obtained in S2 is fired to obtain an oxide containing Na and having a P2 type structure. S3 includes the above-mentioned S3-1, S3-2 and S3-3.

[0091] In S3-1, the composite is pre-fired at a temperature of 300°C to 700°C for 2 hours to 10 hours. In S3-1, the pre-fired can be performed after the composite is arbitrarily formed. The pre-fired is performed at a temperature lower than that of the main calcination. If the pre-fired in S3-1 is insufficient, the formation of the P2 phase in the finally obtained Na-containing oxide may become insufficient. In S3-1, by setting the pre-fired temperature to 300°C to 700°C and the pre-fired time to 2 hours to 10 hours, the composite can be sufficiently pre-fired, the thermal uniformity is improved, and the Na-containing oxide obtained through S3-2 and S3-3 described later can easily become a suitable oxide. The pre-firing temperature may be 400°C to less than 700°C, 450°C to less than 700°C, 500°C to less than 700°C, 550°C to less than 700°C, or 550°C to less than 650°C. In addition, the pre-firing time may be 2 hours to 8 hours, 3 hours to 8 hours, 4 hours to 8 hours, 5 hours to 8 hours, or 5 hours to 7 hours. The pre-firing atmosphere is not particularly limited, and may be, for example, an oxygen-containing atmosphere.

[0092] In S3-2, following the above-mentioned pre-calcination, the composite is subjected to main calcination at a temperature of 700°C to 1100°C for 30 minutes to 10 hours. In S3-2, the main calcination temperature of the composite is 700°C to 1100°C, preferably 800°C to 1000°C. If the main calcination temperature is too low, the P2 phase is not generated, and if the main calcination temperature is too high, the O3 phase is easily generated instead of the P2 phase. There is no particular limitation on the temperature increase conditions from the pre-calcination temperature to the main calcination temperature. There is no particular limitation on the main calcination time, for example, it can be 30 minutes to 48 hours. However, the shape of the oxide containing Na can be controlled by the main calcination time. As described above, in the method disclosed herein, when the coverage of the Na source in the composite is 40% by area or more, when the composite is calcined, it is easy to form a P2 type crystal with small crystallites on its surface. In the method disclosed in the present invention, by interconnecting one P2 type microcrystal with another P2 type microcrystal, the P2 type crystal is grown along the surface of the particle, so that the shape of the oxide containing Na corresponds to the shape of the precursor. For example, in the case where the precursor is a spherical particle, the oxide containing Na can also become a spherical particle. If the main firing time is too short, the generation of the P2 phase becomes insufficient. On the other hand, if the main firing time is too long, the P2 phase grows excessively and becomes a plate-like particle instead of a spherical one. According to the inventors, when the main firing time is more than 30 minutes and less than 3 hours, spherical particles of the oxide containing Na are easily obtained. The oxide containing Na obtained after the main firing may have a plurality of microcrystals on the surface and have a structure in which the microcrystals are connected.

[0093] In S3-3, following the main sintering, the composite is sintered from a temperature T above 200°C. 1 Rapid cooling (cooling at a rate of more than 20°C / min) to a temperature below 100°C T 2 The above-mentioned preliminary firing and main firing are performed, for example, in a heating furnace. In step S3-3, for example, after the composite is mainly fired in a heating furnace, it is cooled in the heating furnace to an arbitrary temperature T above 200°C. 1 , becomes the temperature T 1 After that, the fired product is taken out of the heating furnace and rapidly cooled outside the furnace to an arbitrary temperature T below 100°C. 2 Temperature T 1 The temperature T is any temperature above 200°C, and may be any temperature above 250°C. 2 It can be any temperature below 100°C, any temperature below 50°C, or the cooling end temperature. 1 Until reaching temperature T 2In the specified temperature range between 200°C and 200°C, water easily penetrates into the interlayers of the P2 type structure due to atomic vibration, molecular motion, etc. It is believed that by shortening the time period during which such a temperature range is easily penetrated by water when cooling the composite body (the oxide containing Na having the P2 type structure) after the main sintering (i.e., performing rapid cooling), the amount of water penetrating into the interlayers of the P2 type structure is reduced. In this regard, in step S3-3, when cooling the composite body after the main sintering, the temperature T is set to 200°C or higher. 1 Until reaching any temperature T below 100°C 2 For example, by cooling in a dry atmosphere outside the furnace, the temperature T 1 Until reaching temperature T 2 The cooling rate during the cooling process becomes high (for example, 20°C / min or more), and moisture becomes difficult to penetrate between the layers of the P2 type structure, which can suppress the collapse of the P2 type structure. As a result, Na can be effectively ion-exchanged for Li in S4.

[0094] By using S3, it is possible to manufacture an oxide containing Na having a P2 type structure and a prescribed chemical composition. The oxide containing Na contains at least one transition metal element among Mn, Ni and Co, Na, and O as constituent elements. Among them, when at least Na, Mn, at least one selected from Ni and Co, and O are contained as constituent elements, in particular, when at least Na, Mn, Ni, Co, and O are contained as constituent elements, the performance of the positive electrode active material is likely to be further improved. The oxide containing Na may have a composition consisting of Na c Mn x-p Ni y-q Co z-r M p+q+r O 2The chemical composition represented by . Wherein, 0<c<1.00, x+y+z=1 and 0≤p+q+r<0.17. In addition, M is at least one element selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W. In the case where the oxide containing Na has such a chemical composition, it is easy to further maintain the P2 type structure. In the above chemical composition, c is greater than 0, and can be greater than 0.10, greater than 0.20, greater than 0.30, greater than 0.40, greater than 0.50 or greater than 0.60, and is less than 1.00, and can be less than 0.90, less than 0.80 or less than 0.70. x is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. In addition, y is 0 or more, and may be 0.10 or more, or 0.20 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.20 or less. In addition, z is 0 or more, and may be 0.10 or more, 0.20 or more, or 0.30 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less. Element M has a small contribution to charge and discharge. In this respect, in the above-mentioned chemical composition, by p+q+r being less than 0.17, it is easy to ensure a high charge and discharge capacity. p+q+r may be less than 0.16, less than 0.15, less than 0.14, less than 0.13, less than 0.12, less than 0.11 or less than 0.10. On the other hand, by including the element M, the P2 type structure and the O2 type structure are easily stabilized. In the above-mentioned chemical composition, p+q+r is greater than 0, and may be greater than 0.01, greater than 0.02, greater than 0.03, greater than 0.04, greater than 0.05, greater than 0.06, greater than 0.07, greater than 0.08, greater than 0.09 or greater than 0.10. The composition of O is approximately 2, and is not limited to exactly 2.0, but is indefinite.

[0095] In S4, by exchanging at least a portion of the Na of the Na-containing oxide obtained by S3 with Li, an oxide containing Li having a Li-deficient O2-type structure is obtained. Regarding ion exchange, for example, there is a method using an aqueous solution containing lithium halide, and a method using a mixture of lithium halide and other lithium salts (such as a molten salt). From the viewpoint that the P2-type structure is easily destroyed by the intrusion of water and the viewpoint of crystallinity, the method using a molten salt is preferred among the above two methods. That is, by mixing the above-mentioned Na-containing oxide having a P2-type structure with the molten salt, heating to a temperature above the melting point of the molten salt, at least a portion of the Na of the Na-containing oxide can be replaced with Li by ion exchange. The lithium halide constituting the molten salt is preferably at least one of lithium chloride, lithium bromide and lithium iodide. The other lithium salts constituting the molten salt are preferably lithium nitrate. By using a molten salt, the melting point is reduced compared to the case where lithium halide or other lithium salts are used alone, and ion exchange can be performed at a lower temperature. The temperature in the ion exchange may be, for example, above the melting point of the molten salt and below 600° C., below 500° C., below 400° C., or below 300° C. If the temperature in the ion exchange is too high, an O3 type structure is easily generated as a stable phase instead of an O2 type structure. On the other hand, from the viewpoint of shortening the time taken for the ion exchange, the temperature in the ion exchange may be as high as possible.

[0096] 1.1.1.6 Protection layer

[0097] An ion-conductive protective layer may be formed on the surface of a positive electrode active material having a Li-deficient O2-type structure. That is, the positive electrode active material layer 10 may include a composite of the positive electrode active material and the protective layer, in which at least a portion of the surface of the positive electrode active material may be covered by the protective layer. Furthermore, according to the knowledge of the inventors, even when a protective layer is formed on the surface of a positive electrode active material having a Li-deficient O2-type structure, the reaction between the positive electrode active material and the sulfide solid electrolyte may not be suppressed. As described later, in the present disclosure, the reaction between the positive electrode active material and the sulfide solid electrolyte is suppressed by controlling the pressing temperature of the positive electrode active material layer.

[0098] The ion-conductive protective layer may contain various ion-conductive compounds, such as at least one selected from ion-conductive oxides and ion-conductive halides.

[0099] The ion conductive oxide may contain, for example, at least one element selected from B, C, Al, Si, P, S, Ti, La, Zr, Nb, Mo, Zn, and W, Li, and O. The ion conductive oxide may be an oxynitride containing N. More specifically, the ion conductive oxide may be selected from Li 3 BO3 、LiBO 2 , Li 2 CO 3 、LiAlO 2 , Li 4 SiO 4 , Li 2 SiO 3 , Li 3 PO 4 , Li 2 SO 4 , Li 2 TiO 3 , Li 4 Ti 5 O 12 , Li 2 Ti 2 O 5 , Li 2 ZrO 3 、LiNbO 3 , Li 2 MoO 4 , Li 2 WO 4 、LiPON、Li 2 O-LaO 2 , Li 2 O-ZnO 2 At least one of the following. The ion conductive oxide may be a product obtained by replacing a part of the elements with various doping elements.

[0100] The ion-conductive halide may be, for example, at least one of the various compounds exemplified as the halide solid electrolyte described later. The ion-conductive halide may contain, for example, at least one element selected from Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb, and Sm, at least one halogen element selected from Cl, Br, I, and F, and Li. The ion-conductive halide may contain at least one element selected from Ti, Al, Gd, Ca, Zr, and Y, at least one selected from Cl, Br, I, and F, and Li. In addition, the ion-conductive halide may contain at least one element selected from Ti and Al, at least one element selected from Cl, Br, I, and F, and Li. In addition, the ion-conductive halide may be, for example, a composite halide of Li and Ti and Al and F.

[0101] The coverage (area ratio) of the protective layer on the surface of the positive electrode active material may be, for example, 70% or more, 80% or more, or 90% or more. The thickness of the protective layer may be, for example, 0.1 nm or more, 1 nm or more, or 100 nm or less, or 20 nm or less.

[0102] 1.1.2 Sulfide solid electrolyte

[0103] The positive electrode active material layer 10 contains the above-mentioned positive electrode active material having the Li-deficient O2-type structure and a sulfide solid electrolyte. The method for manufacturing a sulfide solid electrolyte is well known. That is, the desired sulfide solid electrolyte can be manufactured by selecting and weighing raw materials according to the target chemical composition, and then mixing the raw materials.

[0104] 1.1.2.1 Crystallinity

[0105] The sulfide solid electrolyte may be a glass-based sulfide solid electrolyte (sulfide glass), a glass-ceramic sulfide solid electrolyte, or a crystalline sulfide solid electrolyte. Sulfide glass is amorphous. Sulfide glass may have a glass transition temperature (Tg). In addition, when the sulfide solid electrolyte has a crystalline phase, examples of the crystalline phase include Thio-LISICON type crystalline phase, LGPS type crystalline phase, and Argentum type crystalline phase.

[0106] 1.1.2.2 Chemical composition

[0107] The sulfide solid electrolyte may contain, for example, Li element, P element, and S element. The sulfide solid electrolyte may further contain X element (X is at least one of As, Sb, Si, Ge, Sn, B, Al, Ga, and In). In addition, the sulfide solid electrolyte may further contain at least one of O element and halogen element. In addition, the sulfide solid electrolyte may contain S element as the main component of the anion element. The sulfide solid electrolyte may be, for example, selected from Li 2 SP 2 S 5 , Li 2 SP 2 S 5 -LiI, Li 2 SP 2 S 5 -GeS 2 , Li 2 SP 2 S 5 -Li 2 O. Li 2 SP 2 S 5 -Li 2 O-LiI、Li 2 SP 2 S 5 -LiI-LiBr, Li 2 S-SiS 2 -P 2 S5 -LiI, Li 2 SP 2 S 5 -ZmSn (wherein m and n are positive numbers. Z is any one of Ge, Zn and Ga.), Li 2 S-SiS 2 -Li 3 PO 4 , Li 2 S-SiS 2 -Li x MO y (wherein x and y are positive numbers. M is at least one of P and any one of Si, Ge, B, Al, Ga, and In.) Alternatively, the sulfide solid electrolyte is not particularly limited, and may have a sulfide electrolyte selected from xLi 2 S·(100-x)P 2 S 5 (70≤x≤80),yLiI·zLiBr·(100-yz)(xLi 2 S·(1-x)P 2 S 5 )(0.7≤x≤0.8, 0≤y≤30, 0≤z≤30), etc. Alternatively, the sulfide solid electrolyte may have a general formula: Li 4-x Ge 1-x P x S 4 (0<x<1). In the above general formula, at least a portion of Ge may be replaced by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. In the above general formula, a portion of P may be replaced by at least one of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V and Nb. In the above general formula, a portion of Li may be replaced by at least one of Na, K, Mg, Ca and Zn. In the above general formula, a portion of S may be replaced by halogen (at least one of F, Cl, Br and I). Alternatively, the sulfide solid electrolyte may have a Li 7-a PS 6-a X a (X is at least one of Cl, Br and I, and a is a number greater than or equal to 0 and less than or equal to 2). a may be 0 or greater than 0. In the latter case, a may be greater than or equal to 0.1, greater than or equal to 0.5, or greater than or equal to 1. In addition, a may be less than or equal to 1.8, or less than or equal to 1.5.

[0108] 1.1.2.3 Shape

[0109] The sulfide solid electrolyte may be in a particle form. The average particle size (D50) of the sulfide solid electrolyte may be, for example, 10 nm or more and 100 μm or less.

[0110] 1.1.3 Other ingredients

[0111] The positive electrode active material layer 10 may optionally contain other positive electrode active materials, other electrolytes, a conductive aid, a binder, and the like.

[0112] 1.1.3.1 Other positive electrode active materials

[0113] The positive electrode active material contained in the positive electrode active material layer 10 may be composed only of the above-mentioned positive electrode active material with the O2 type structure of the Li deficiency type, or may also include the positive electrode active material (other positive electrode active material) other than the positive electrode active material while including the positive electrode active material. From the viewpoint of further improving the effect of the technology disclosed in the present invention, the proportion of other positive electrode active materials in the positive electrode active material as a whole may be a small amount. For example, when the whole of the positive electrode active material is set to 100% by mass, the content of the positive electrode active material with the O2 type structure of the Li deficiency type described above may be 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 99% by mass or more and 100% by mass or less.

[0114] As for other positive electrode active materials that may be contained in the positive electrode active material layer 10, all positive electrode active materials known as positive electrode active materials for lithium ion batteries can be used. Other positive electrode active materials may be, for example, at least one of various lithium compounds, elemental sulfur and sulfur compounds other than the above-mentioned Li-containing oxides having a Li-deficient O2-type structure. The lithium compound as other positive electrode active materials may be an oxide containing Li containing at least one element M, Li, and O. The element M may be, for example, at least one selected from Mn, Ni, Co, Al, Mg, Ca, Sc, V, Cr, Cu, Zn, Ga, Ge, Y, Zr, Sn, Sb, W, Pb, Bi, Fe and Ti, and may be at least one selected from Mn, Ni, Co, Al, Fe and Ti. More specifically, the oxide containing Li as other positive electrode active materials may be selected from lithium cobaltate, lithium nickelate, lithium manganate, lithium nickel cobaltate, lithium nickel manganate, lithium cobalt manganate, lithium nickel cobalt manganate (Li 1±α Ni x Co y Mn z O 2±δ (for example, 0<x<1, 0<y<1, 0<z<1, x+y+z=1)), spinel lithium compounds (composed of Li1+x Mn 2-x-y M y O 4 (M is one or more selected from Al, Mg, Co, Fe, Ni and Zn) represented by a different element substitution Li-Mn spinel, etc.), lithium nickel cobalt aluminum oxide (for example, Li 1±α Ni p Co q Al r O 2±δ (e.g., p+q+r=1)), lithium titanate, lithium metal phosphate (LiMPO 4 Etc., M is at least one selected from Fe, Mn, Co and Ni) etc. In particular, when other positive electrode active materials include at least one selected from Ni, Co and Mn, Li, and O as constituent elements containing oxides containing Li, the performance of lithium ion batteries is easy to further improve. Alternatively, when other positive electrode active materials include at least one selected from Ni, Co and Al, Li, and O as constituent elements containing oxides containing Li, the performance of lithium ion batteries is also easy to further improve. Other positive electrode active materials can be used alone or in combination of two or more. As for the shape of other positive electrode active materials, as long as it is a general shape of positive electrode active materials for lithium ion batteries. Other positive electrode active materials may be, for example, in the form of particles. Other positive electrode active materials may be solid or have voids, for example, may be porous or hollow. Other positive electrode active materials may be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle diameter D50 of other positive electrode active materials may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less.

[0115] 1.1.3.2 Other electrolytes

[0116] The electrolyte contained in the positive electrode active material layer 10 may be composed only of the above-mentioned sulfide solid electrolyte, or may include electrolytes other than the sulfide solid electrolyte together with the sulfide solid electrolyte. From the viewpoint of further improving the effect of the technology disclosed in the present invention, the proportion of other electrolytes in the electrolyte contained in the positive electrode active material layer 10 as a whole may be a small amount. For example, when the total amount of the electrolyte contained in the positive electrode active material layer 10 is set to 100% by mass, the content of the above-mentioned sulfide solid electrolyte may be 50% by mass or more and 100% by mass or less, 60% by mass or more and 100% by mass or less, 70% by mass or more and 100% by mass or less, 80% by mass or more and 100% by mass or less, 90% by mass or more and 100% by mass or less, 95% by mass or more and 100% by mass or less, or 99% by mass or more and 100% by mass or less.

[0117] Other electrolytes that may be contained in the positive electrode active material layer 10 may be solid electrolytes, liquid electrolytes, or combinations thereof. As a solid electrolyte, a solid electrolyte known as a solid electrolyte for lithium ion batteries can be used. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, the ion conductivity and heat resistance of the inorganic solid electrolyte are excellent. As inorganic solid electrolytes other than the above-mentioned sulfide solid electrolytes, for example, oxide solid electrolytes and ionic inorganic solid electrolytes can be listed. Among the ionic solid electrolytes, the performance of a solid electrolyte containing at least Li, Y and halogen (at least one of Cl, Br, I and F) as constituent elements is high. Other solid electrolytes may be amorphous or crystalline. Other solid electrolytes may be in particulate form. The average particle size (D50) of other solid electrolytes may be, for example, greater than 10 nm and less than 10 μm. One solid electrolyte may be used alone, or two or more may be used in combination.

[0118] The oxide solid electrolyte may be selected from lithium lanthanum zirconate, LiPON, Li 1+X Al X Ge 2-X (PO 4 ) 3 , Li—SiO-based glass, Li—Al—SO-based glass, etc. In addition, when an oxide solid electrolyte is combined with a liquid electrolyte, ion conductivity can be improved.

[0119] The ionic solid electrolyte may, for example, contain at least one element selected from Mg, Ca, Sr, Ba, Zn, Sn, Al, Sc, Ga, Bi, Sb, Zr, Hf, Ti, Ta, Nb, W, Y, Gd, Tb and Sm. These elements can generate cations in water. In addition, the ionic solid electrolyte material may, for example, further contain at least one halogen element selected from Cl, Br, I and F. These elements can generate anions in water. The ionic solid electrolyte may contain at least one selected from Gd, Ca, Zr and Y, at least one selected from Cl, Br, I and F, and Li. In addition, the ionic solid electrolyte contains Li and Y, and may contain at least one selected from Cl, Br, I and F. More specifically, the ionic solid electrolyte may contain Li and Y and Cl and Br, may contain Li and Ca and Y and Gd and Cl and Br, or may contain Li and Zr and Y and Cl. More specifically, the ionic solid electrolyte may be Li 3 Yb 2 Cl 4 , Li 2.8 Ca 0.1 Y 0.5G 0.5 Br 2 Cl 4 , and Li 2.5 Y 0.5 Zr 0.5 Cl 6 At least one of .

[0120] The ionic solid electrolyte may be a halide solid electrolyte. The halide solid electrolyte has excellent ion conductivity. As a halide solid electrolyte, for example, it may have a halide solid electrolyte represented by formula (A):

[0121] Li α M β X γ ···(A)

[0122] The composition represented by . Wherein, α, β and γ are each independently a value greater than 0, M is at least one selected from metal elements and semi-metal elements other than Li, and X is at least one selected from Cl, Br and I. Furthermore, the "semi-metal element" may be at least one selected from B, Si, Ge, As, Sb and Te. In addition, the "metal element" may include (i) all elements contained in the first to twelfth groups of the periodic table (however, excluding hydrogen) and (ii) all elements contained in the thirteenth to sixteenth groups of the periodic table (however, excluding B, Si, Ge, As, Sb, Te, C, N, P, O, S and Se.). The metal element forms an inorganic compound together with the halide ion and can become a cation.

[0123] In formula (A), M may include Y (ie, yttrium). The halide solid electrolyte including Y may have a a Me b Y c X 6 (wherein, a+mb+3c=6, c>0, Me is at least one selected from metal elements and semi-metal elements other than Li and Y, and m is the valence of Me). Me can be, for example, at least one selected from Mg, Ca, Sr, Ba, Zn, Sc, Al, Ga, Bi, Zr, Hf, Ti, Sn, Ta, and Nb.

[0124] The halide solid electrolyte may have a structure represented by formula (A1): Li 6-3d Y d X 6 In formula (A1), X is one or more elements selected from Cl, Br and I. d may satisfy 0<d<2, and may be d=1. The halide solid electrolyte may have a composition represented by formula (A2): Li 3-3δ Y 1+δ Cl 6In formula (A2), 0<δ≤0.15 may be satisfied. The halide solid electrolyte may have a composition represented by formula (A3): Li 3-3δ Y 1+δ Br 6 In formula (A3), 0<δ≤0.25 may be satisfied. The halide solid electrolyte may have a composition represented by formula (A4): Li 3-3δ+a Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A4), Me may be at least one selected from Mg, Ca, Sr, Ba and Zn. In formula (A4), for example, -1<δ<2, 0<a<3, 0<(3-3δ+a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6 and (x+y)≤6 are satisfied. The halide solid electrolyte may have a composition represented by formula (A5): Li 3-3δ Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A5), Me may be at least one selected from Al, Sc, Ga and Bi. In formula (A5), -1<δ<1, 0<a<2, 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6. The halide solid electrolyte may have a composition represented by formula (A6): Li 3-3δ-a Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A6), Me may be at least one selected from Zr, Hf and Ti. In formula (A6), -1<δ<1, 0<a<1.5, 0<(3-3δ-a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6. The halide solid electrolyte may have a composition represented by formula (A7): Li 3-3δ-2a Y 1+δ-a Me a Cl 6-x-y Br x I y In formula (A7), Me may be at least one selected from Ta and Nb. In formula (A7), -1<δ<1, 0<a<1.2, 0<(3-3δ-2a), 0<(1+δ-a), 0≤x≤6, 0≤y≤6, and (x+y)≤6.

[0125] The ionic solid electrolyte may be a complex hydride solid electrolyte. The complex hydride solid electrolyte may be composed of Li ions and complex ions containing H. The complex ions containing H may, for example, have an element M containing at least one of a non-metallic element, a semi-metallic element, and a metal element, and H bound to the element M. In addition, in the case of the complex ion containing H, the element M as the central element and the H surrounding the element M may be bound to each other via covalent bonds. In addition, the complex ion containing H may be composed of (M m H n ) α- Indicated. In this case, m is an arbitrary positive number, and n and α can be arbitrary positive numbers according to m, the valence of the element M, etc. The element M can be a non-metallic element or a metal element that can form a complex ion. For example, the element M can contain at least one of B, C and N as a non-metallic element, and can contain B. In addition, for example, the element M can contain at least one of Al, Ni and Fe as a metal element. In particular, when the complex ion contains B, or contains C and B, it is easy to ensure higher ion conductivity. As specific examples of complex ions containing H, (CB 9 H 10 ) - , (CB 11 H 12 ) - ,(B 10 H 10 ) 2- ,(B 12 H 12 ) 2- ,(BH 4 ) - NH 2 ) - 、(AlH 4 ) - , and combinations thereof. In particular, when using (CB 9 H 10 ) - , (CB 11 H 12 ) - , or a combination thereof, it is easy to ensure higher ion conductivity. That is, the complex hydride solid electrolyte may contain Li, C, B and H.

[0126] The liquid electrolyte is a liquid containing lithium ions as carrier ions. The electrolyte may be an aqueous electrolyte or a non-aqueous electrolyte. The composition of the electrolyte may be the same as the composition of the electrolyte of a lithium ion battery. The electrolyte may be a product of dissolving a lithium salt in water or a non-aqueous solvent. Examples of the non-aqueous solvent include various carbonate-based solvents. Examples of the lithium salt include lithium amide salts, LiPF 6 wait.

[0127] 1.1.3.3 Conductive additives

[0128] As the conductive aid that can be contained in the positive electrode active material layer 10, for example, carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); and metal materials such as nickel, titanium, aluminum, and stainless steel can be listed. The conductive aid can be, for example, in the form of particles or fibers, and there is no particular limitation on the size. The conductive aid can be used alone or in combination of two or more.

[0129] 1.1.3.4 Adhesives

[0130] As the binder that can be contained in the positive electrode active material layer 10, for example, butadiene rubber (BR)-based binders, butylene rubber (IIR)-based binders, acrylate butadiene rubber (ABR)-based binders, styrene butadiene rubber (SBR)-based binders, polyvinylidene fluoride (PVdF)-based binders, polytetrafluoroethylene (PTFE)-based binders, polyimide (PI)-based binders, etc. can be listed. Only one type of binder can be used alone, or two or more types can be used in combination.

[0131] 1.1.3.5 Others

[0132] The positive electrode active material layer 10 may contain various additives, such as a dispersant and a lubricant, in addition to the above-mentioned components.

[0133] 1.1.4 Raman spectroscopy of the positive electrode active material layer

[0134] The Raman spectrum of the positive electrode active material layer 10 satisfies the following relations (1) and (2).

[0135] I R1 / I R2 ≤0.20···(1)

[0136] I R3 / I R2 ≤0.20···(2)

[0137] I R1 : The Raman spectrum from P 2 S 6 4- The peak intensity

[0138] I R2 : The Raman spectrum from PS 4 3- The peak intensity

[0139] I R3 : The peak intensity from SS in the Raman spectrum

[0140] Among them, the peak intensity I R1 Equivalent to 385cm in Raman spectroscopy -1 In addition, the peak intensity I R2 Equivalent to 420cm in Raman spectroscopy -1 In addition, the peak intensity I R3 Equivalent to 475cm in Raman spectroscopy -1 For Raman spectroscopy, 300 cm -1 The peak intensity at was set to 0 for normalization (background processing).

[0141] In the past, when the positive electrode active material layer was obtained, it was pressed at the highest possible temperature to improve the compactness of the positive electrode active material layer, thereby reducing the resistance of the positive electrode active material layer. However, according to the new understanding of the present inventors, when the positive electrode active material layer contains a positive electrode active material with a Li-deficient O2-type structure and a sulfide solid electrolyte, if the positive electrode active material layer is pressed at a high temperature, the positive electrode active material with a Li-deficient O2-type structure reacts with the sulfide solid electrolyte, and the PS of the sulfide solid electrolyte 4 The skeleton collapses, which increases the resistance. Such a problem occurs particularly when a positive electrode active material with a Li-deficient O2-type structure is used in combination with a sulfide solid electrolyte in the positive electrode active material layer. Such a problem does not occur when a Li-free positive electrode active material (e.g., a product in which Li is doped in a positive electrode active material with an O2-type structure, a positive electrode active material with an O3-type structure) is used in combination with a sulfide solid electrolyte.

[0142] According to the new findings of the present inventors, the PS of the sulfide solid electrolyte contained in the positive electrode active material layer 4 When the skeleton collapses, if the Raman spectrum of the positive electrode active material layer is obtained, P 2 S 6 4- The smaller the Raman peaks derived from the reaction products, the higher the PS content of the sulfide solid electrolyte contained in the positive electrode active material layer. 4 The more the skeleton is maintained, the more the reaction between the positive electrode active material having a Li-deficient O2-type structure and the sulfide solid electrolyte is suppressed.

[0143] According to the new knowledge of the present inventors, when the Raman spectrum of the positive electrode active material layer 10 is obtained, if the peak intensity is greater than I R1 / I R2 is less than 0.20 and the peak intensity ratio I R3 / IR2 If the PS value of the sulfide solid electrolyte in the positive electrode active material layer 10 is less than 0.20, it can be said that the PS value of the sulfide solid electrolyte in the positive electrode active material layer 10 is less than 0.20. 4 The skeleton is properly maintained and the resistance can be kept low. R1 / I R2 It can be 0.15 or less, 0.10 or less, or 0.05 or less. R3 / I R2 It may be 0.15 or less, 0.10 or less, or 0.05 or less. In particular, when the peak intensity ratio I R1 / I R2 is less than 0.10, and the peak intensity ratio I R3 / I R2 When the peak intensity ratio is 0.10 or less, a more significant resistance reduction effect can be easily obtained. R1 / I R2 and peak intensity ratio I R3 / I R2 The lower limits of are not particularly limited, and are each greater than 0, and may be greater than 0.01.

[0144] 1.1.5 XPS spectrum of positive electrode active material layer

[0145] The XPS spectrum of the positive electrode active material layer 10 may satisfy the following relations (3) and (4):

[0146] I X1 / I X2 ≤1.20···(3)

[0147] I X3 / I X4 ≤1.60···(4)

[0148] I X1 : The peak intensity from PSP in the XPS spectrum for S2p

[0149] I X2 : The XPS spectrum of S2p from PS 4 3- The peak intensity

[0150] I X3 : The XPS spectrum of P2p from PO x S 4-x 3- The peak intensity

[0151] I X4 : The XPS spectrum of P2p from PS 4 3- The peak intensity.

[0152] Among them, the peak intensity ratio I X1 / I X2 This corresponds to the peak intensity I at 162.9 eV in the XPS spectrum of S2p. X1 The peak intensity I at 161.6 eV in the XPS spectrum of S2p X2 Ratio I X1 / I X2 In addition, the peak intensity ratio I X3 / I X4 This corresponds to the peak intensity I at 133.6 eV in the XPS spectrum of P2p. X3 The peak intensity I at 132.2 eV in the XPS spectrum of P2p X4 Ratio I X3 / I X4 In addition, the XPS spectrum was normalized by setting the peak intensities at 138 eV and 170 eV to 0 (background processing).

[0153] According to the new knowledge of the present inventors, based on the above mechanism, the PS of the sulfide solid electrolyte in the positive electrode active material layer 4 When the skeleton collapses, the XPS spectrum of the positive electrode active material layer is obtained, and it is confirmed that the PSP and PO x S 4-x 3- It can be said that the smaller the XPS peak derived from the reaction product, the higher the PS content of the sulfide solid electrolyte contained in the positive electrode active material layer. 4 The more the skeleton is maintained, the more the reaction between the positive electrode active material having a Li-deficient O2-type structure and the sulfide solid electrolyte is suppressed.

[0154] According to the new knowledge of the present inventors, when the XPS spectrum of the positive electrode active material layer 10 is obtained, if the peak intensity ratio is X1 / I X2 is less than 1.20 and the peak intensity ratio I X3 / I X4 is 1.60 or less, it can be said that the PS of the sulfide solid electrolyte in the positive electrode active material layer 10 is 4 The skeleton is more properly maintained, and lower resistance can be maintained. X1 / I X2 It may be 1.10 or less, 1.00 or less, 0.90 or less, 0.80 or less, 0.70 or less, or 0.60 or less. X3 / I X4 It may be 1.40 or less, 1.20 or less, 1.00 or less, 0.80 or less, 0.60 or less, or 0.40 or less. In particular, when the peak intensity ratio IX1 / I X2 is less than 0.70 and the peak intensity ratio I X3 / I X4 When the peak intensity ratio is 0.50 or less, a more significant resistance reduction effect can be easily obtained. X1 / I X2 and peak intensity ratio I X3 / I X4 The lower limits of each are not particularly limited, and each is greater than 0. X1 / I X2 It may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more. X3 / I X4 It may be 0.10 or more, 0.20 or more, or 0.30 or more.

[0155] 1.1.6 Shape of the positive electrode active material layer

[0156] The shape of the positive electrode active material layer 10 is not particularly limited, and may be, for example, a substantially flat sheet-shaped positive electrode active material layer 10. The thickness of the positive electrode active material layer 10 is not particularly limited, and may be, for example, 0.1 μm or more or 1 μm or less, and may be 2 mm or less or 1 mm or less.

[0157] 1.2 Electrolyte layer

[0158] The electrolyte layer 20 is arranged between the positive electrode active material layer 10 and the negative electrode active material layer 30. The electrolyte layer 20 contains at least an electrolyte. The electrolyte layer 20 may contain at least one of a solid electrolyte and an electrolyte solution, and may further optionally contain a binder, etc. In particular, when the electrolyte layer 20 contains a solid electrolyte, it is easy to ensure higher performance. There is no particular limitation on the content of the electrolyte and the binder, etc. in the electrolyte layer 20. Alternatively, the electrolyte layer 20 may have a diaphragm (separator) for preventing the positive electrode active material layer 10 from contacting the negative electrode active material layer 30 while maintaining the electrolyte solution. There is no particular limitation on the thickness of the electrolyte layer 20, for example, it may be 0.1 μm or more or 1 μm or more, or it may be 2 mm or less or 1 mm or less.

[0159] The electrolyte layer 20 may be composed of one layer or a plurality of layers. For example, the electrolyte layer 20 may include a first layer disposed on the positive electrode active material layer 10 side and a second layer disposed on the negative electrode active material layer 30 side, the first layer may include a first electrolyte, and the second layer may include a second electrolyte. The first electrolyte and the second electrolyte may be different types from each other. The first electrolyte and the second electrolyte may each be at least one selected from the above-mentioned oxide solid electrolyte, sulfide solid electrolyte and ionic solid electrolyte. For example, the first layer may include an ionic solid electrolyte, and the second layer may include at least one of an ionic solid electrolyte and a sulfide solid electrolyte.

[0160] As the electrolyte contained in the electrolyte layer 20, it is sufficient to select appropriately from the electrolyte (solid electrolyte and / or liquid electrolyte) exemplified as the electrolyte that can be contained in the above-mentioned positive electrode active material layer 10. In addition, for the binder that can be contained in the electrolyte layer 20, it is sufficient to select appropriately from the binder exemplified as the binder that can be contained in the above-mentioned positive electrode active material layer. Electrolytes and binders can be used alone or in combination of two or more. The separator can be a separator commonly used in lithium-ion batteries, for example, separators composed of resins such as polyethylene (PE), polypropylene (PP), polyester and polyamide can be listed. The separator can be a single-layer structure or a multi-layer structure. As a multi-layer structure separator, for example, a 2-layer structure separator of PE / PP, or a 3-layer structure separator of PP / PE / PP or PE / PP / PE can be listed. The separator can be composed of non-woven fabrics such as cellulose non-woven fabrics, resin non-woven fabrics, and glass fiber non-woven fabrics.

[0161] 1.3 Negative electrode active material layer

[0162] The negative electrode active material layer 30 contains at least a negative electrode active material. In addition, the negative electrode active material layer 30 may optionally contain an electrolyte, a conductive aid, a binder, and various additives. The content of each component in the negative electrode active material layer 30 can be appropriately determined according to the target battery performance. For example, when the solid content of the negative electrode active material layer 30 is set to 100% by mass, the content of the negative electrode active material may be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, and may be 100% by mass or less, less than 100% by mass, 95% by mass or less, or 90% by mass or less. Alternatively, when the negative electrode active material layer 30 is set to 100% by volume, it may contain a total of 85% by volume or more, 90% by volume or more, or 95% by volume or more of a negative electrode active material and optional electrolytes, conductive aids, and binders, and the remainder may be voids or other components. The shape of the negative electrode active material layer 30 is not particularly limited, for example, it may be a sheet with a substantially flat surface. The thickness of the negative electrode active material layer 30 is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or less, or 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0163] 1.3.1 Negative electrode active material

[0164] As for the negative electrode active material, any material known as the negative electrode active material of the lithium ion battery can be used. Various materials whose potential for absorbing and releasing lithium ions (charge and discharge potential) is lower than that of the above-mentioned positive electrode active material can be used. For example, silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, etc. can be used. Among them, when the negative electrode active material layer 30 contains Si as the negative electrode active material, the performance of the lithium ion battery 100 is easily improved. The negative electrode active material can be used alone or in combination of two or more. The shape of the negative electrode active material is sufficient as long as it is a general shape of the negative electrode active material of the lithium ion battery. For example, the negative electrode active material can be in the form of particles. The negative electrode active material particles can be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle size (D50) of the negative electrode active material particles may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material may be in the form of a sheet (foil, film) such as lithium foil. That is, the negative electrode active material layer 30 may be composed of a sheet of the negative electrode active material.

[0165] 1.3.2 Others

[0166] As the electrolyte that can be contained in the negative electrode active material layer 30, for example, the above-mentioned solid electrolyte, electrolyte solution or a combination thereof can be listed. The conductive aid that can be contained in the negative electrode active material layer 30 can be appropriately selected from the conductive aids exemplified as the conductive aids that can be contained in the above-mentioned positive electrode active material layer. The binder that can be contained in the negative electrode active material layer 30 can be appropriately selected from the binders exemplified as the binders that can be contained in the above-mentioned positive electrode active material layer. The electrolyte, the conductive aid, and the binder can be used alone or in combination of two or more.

[0167] 1.4 Positive electrode collector

[0168] like Figure 1 As shown, the lithium ion battery 100 may include a positive electrode collector 40 in contact with the positive electrode active material layer 10. As for the positive electrode collector 40, any positive electrode collector generally used as a positive electrode collector of a lithium ion battery can be used. In addition, the positive electrode collector 40 may have a shape selected from at least one of foil, plate, mesh, punched metal, and foam. The positive electrode collector 40 may be composed of a metal foil or a metal mesh. In particular, the metal foil has excellent handling properties. The positive electrode collector 40 may be composed of a plurality of foils. As the metal constituting the positive electrode collector 40, at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel can be listed. In particular, from the perspective of ensuring oxidation resistance, the positive electrode collector 40 may contain Al. The positive electrode current collector 40 may have some coating on its surface for the purpose of adjusting resistance, etc. For example, the positive electrode current collector 40 may have a carbon coating. In addition, the positive electrode current collector 40 may be a product obtained by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the positive electrode current collector 40 is composed of a plurality of metal foils, there may be some layers between the plurality of metal foils. There is no particular limitation on the thickness of the positive electrode current collector 40. For example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 1 mm or less than 100 μm.

[0169] 1.5 Negative electrode collector

[0170] like Figure 1As shown, the lithium ion battery 100 may include a negative electrode collector 50 in contact with the negative electrode active material layer 30. As for the negative electrode collector 50, any negative electrode collector generally used as a negative electrode collector of a lithium ion battery can be used. In addition, the negative electrode collector 50 may be in the form of a foil, a plate, a mesh, a punched metal, a foam, etc. The negative electrode collector 50 may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, the metal foil has excellent handling properties. The negative electrode collector 50 may be composed of a plurality of foils or sheets. As the metal constituting the negative electrode collector 50, at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel may be listed. In particular, from the viewpoint of ensuring reduction resistance and difficulty in alloying with lithium, the negative electrode collector 50 may include at least one metal selected from Cu, Ni and stainless steel. The negative electrode collector 50 may have some coating on its surface for the purpose of adjusting resistance, etc. For example, the negative electrode collector 50 may have a carbon coating. The negative electrode collector 50 may be an aluminum foil with a carbon coating. In addition, the negative electrode collector 50 may be a product obtained by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the negative electrode collector 50 is composed of a plurality of metal foils, there may be some layers between the plurality of metal foils. There is no particular limitation on the thickness of the negative electrode collector 50. For example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 1 mm or less than 100 μm.

[0171] 1.6 Other components

[0172] In addition to the above-mentioned structures, the lithium-ion battery 100 may include a general structure as a battery. For example, pole pieces, terminals, etc. The lithium-ion battery 100 may be a product in which the above-mentioned structures are housed inside an outer packaging body. As for the outer packaging body, any outer packaging body known as an outer packaging body of a battery can be adopted. In addition, a plurality of batteries 100 can be electrically connected arbitrarily, and can be overlapped arbitrarily to form a battery pack. In this case, the battery pack can be accommodated inside a known battery casing. As the shape of the lithium-ion battery 100, for example, a coin type, a laminate type, a cylindrical type, and a square type can be listed. The lithium-ion battery 100 can be a secondary battery.

[0173] 2. Manufacturing method of lithium-ion battery

[0174] The lithium ion battery 100 can be manufactured, for example, by the following method. Figure 2 As shown, a method for manufacturing a lithium-ion battery 100 according to one embodiment includes:

[0175] A positive electrode active material 11 having a Li-deficient O2-type structure and a sulfide solid electrolyte 12 are mixed to obtain a positive electrode composite material 15; and

[0176] The positive electrode mixture 15 is pressed at a temperature lower than 165° C. to obtain the positive electrode active material layer 10 .

[0177] 2.1 Mixing

[0178] There is no particular limitation on the mixing method of the positive electrode active material 11 and the sulfide solid electrolyte 12. The positive electrode active material 11 and the sulfide solid electrolyte 12 may be mixed in a dry manner or in a wet manner using a solvent. There is no particular limitation on the mixing means. For example, various mechanical mixing means such as a ball mill may be used. As described above, the positive electrode active material layer 10 may contain optional components in addition to the positive electrode active material 11 and the sulfide solid electrolyte 12. That is, by mixing the optional components together with the positive electrode active material 11 and the sulfide solid electrolyte 12, a positive electrode composite 15 may be obtained. The positive electrode composite 15 may be dispersed in a solvent to form a slurry. The solvent used in this case is not particularly limited, and water and various organic solvents can be used. As Figure 2 As shown, the slurry is applied to the surface of the positive electrode current collector 40 using a doctor blade or the like and then dried, so that the positive electrode mixed material 15 can be stacked on the surface of the positive electrode current collector 40 .

[0179] 2.2 Suppression

[0180] The positive electrode composite material 15 is pressed at a temperature lower than 165° C. Thus, the positive electrode active material layer 10 is obtained. Figure 2 As shown, the positive electrode composite material 15 can be stacked on the surface of the positive electrode collector 40, and then the positive electrode composite material 15 and the positive electrode collector 40 are pressed together in the stacking direction to form the positive electrode active material layer 10 on the surface of the positive electrode collector 40. The pressing temperature needs to be less than 165°C. When the pressing temperature is above 165°C, the positive electrode active material 11 reacts with the sulfide solid electrolyte 12, and the PS of the sulfide solid electrolyte 12 4The skeleton collapses and the above-mentioned relationships (1) to (4) are no longer satisfied. The pressing temperature may be below 160°C, below 155°C or below 150°C. On the other hand, there is no particular limitation on the lower limit of the pressing temperature. The pressing temperature may be above room temperature (25°C), above 50°C, above 75°C, above 100°C or above 125°C. There is no particular limitation on the pressure during pressing, as long as it is a pressure that densifies the positive electrode composite 15 and can form the positive electrode active material layer 10. The pressing means may be any pressing means that can appropriately press the positive electrode composite 15. For example, various pressing means such as roller pressing may be used. Furthermore, the pressing of the positive electrode composite 15 may be performed together with the electrolyte layer 20 and the negative electrode active material layer 30 described later. That is, in one embodiment, after obtaining a stacked body including the positive electrode current collector 40 , the positive electrode composite material 15 , the electrolyte layer 20 , the negative electrode active material layer 30 , and the negative electrode current collector 50 in this order, the stacked body may be pressed in the stacking direction.

[0181] After the above mixing and pressing, the positive electrode active material layer 10 is obtained. By combining the positive electrode active material layer 10 obtained in this way with the electrolyte layer 20 and the negative electrode active material layer 30, the lithium ion battery 100 can be manufactured. For example, as follows.

[0182] (1) The negative electrode active material constituting the negative electrode active material layer is dispersed in a solvent to obtain a negative electrode layer slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The negative electrode layer slurry is applied to the surface of the negative electrode collector 50 using a scraper or the like, and then dried and optionally pressed, so that the negative electrode active material layer 30 can be formed on the surface of the negative electrode collector 50.

[0183] (2) The layers are stacked in such a manner that the positive electrode active material layer 10 and the negative electrode active material layer 30 sandwich the electrolyte layer 20 (solid electrolyte layer or separator), thereby obtaining a stack having the positive electrode collector 40, the positive electrode active material layer 10, the electrolyte layer 20, the negative electrode active material layer 30, and the negative electrode collector 50 in this order. When a solid electrolyte layer is used as the electrolyte layer 20, the solid electrolyte layer can be formed on a peelable substrate and then transferred to the positive electrode active material layer 10 and the negative electrode active material layer 30, thereby obtaining a stack. Other components such as terminals are installed on the stack as needed.

[0184] (3) The stacked body is housed in a battery case. When the battery case contains an electrolyte, the electrolyte is filled in the battery case, and the stacked body is sealed in the battery case so that the stacked body is immersed in the electrolyte. In this way, the lithium ion battery 100 is obtained.

[0185] 3. Vehicles with lithium-ion batteries

[0186] As described above, the lithium-ion battery of the present disclosure has low resistance. Such a lithium-ion battery can be preferably used in a vehicle selected from at least one of a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV) and an electric vehicle (BEV). That is, the technology of the present disclosure also has the following aspects: a vehicle, which is a vehicle having a lithium-ion battery, wherein the lithium-ion battery has a positive electrode active material layer, an electrolyte layer and a negative electrode active material layer, wherein the positive electrode active material layer comprises a positive electrode active material having an O2-type structure of a Li-deficient type, and a sulfide solid electrolyte, and the Raman spectrum of the positive electrode active material layer satisfies the above-mentioned relationships (1) and (2).

[0187] Example

[0188] As described above, one embodiment of a lithium ion secondary battery and the like has been described, but the technology disclosed herein can be variously modified outside of the above embodiment without departing from the gist thereof. The following examples are shown to further describe the technology disclosed herein, but the technology disclosed herein is not limited to the following examples.

[0189] 1. Preparation of positive electrode active material with Li-deficient O2-type structure

[0190] 1.1 Preparation of precursor

[0191] (1) Weighing MnSO 4 ·5H 2 O、NiSO 4 6H 2 O. CoSO 4 7H 2 O was dissolved in distilled water at a target composition ratio to a concentration of 1.2 mol / L to obtain a first solution. 2 CO 3 This was dissolved in distilled water to a concentration of 1.2 mol / L to obtain a second solution.

[0192] (2) 1000 mL of pure water was placed in a reaction container (with baffles), and 500 mL of the first solution and 500 mL of the second solution were added dropwise thereto at a rate of about 4 mL / min.

[0193] (3) After the dropwise addition was completed, the mixture was stirred at room temperature at a stirring speed of 100 rpm for 1 hour to obtain a product.

[0194] (4) The product is washed with pure water, separated into solid and liquid using a centrifuge, and the precipitate is recovered.

[0195] (5) The obtained precipitate was dried at 120°C overnight, crushed in a mortar, and then separated into coarse particles and fine particles by air flow classification. Here, both the coarse particles and the fine particles are composite salts containing Mn, Ni and Co. In this embodiment, coarse particles among the coarse particles and the fine particles were used as precursor particles. The coarse particles were spherical particles with an average particle size D50 of 3.5 μm.

[0196] 1.2 Fabrication of the complex

[0197] (1) Weigh Na to obtain 1150 g / L 2 CO 3 After adding distilled water, stir with a stirrer until it is completely dissolved to produce Na 2 CO 3 Aqueous solution.

[0198] (2) The above Na 2 CO 3 The aqueous solution and the above-mentioned precursor particles are weighed and mixed so that the composition after calcination described below becomes Na 0.8 Mn 0.5 Ni 0.2 Co 0.3 O 2 , thereby obtaining a slurry.

[0199] (3) The slurry was dried by spray drying to obtain a composite. Specifically, a spray drying device DL410 was used at a slurry feeding rate of 30 mL / min, an inlet temperature of 200°C, and a circulating air volume of 0.8 m 3 The slurry was dried under the conditions of 0.5 % slurry / min and 0.3 MPa spray pressure, thereby the surface of the precursor particles was treated with Na 2 CO 3 In the composite, more than 70% by area of ​​the surface of the precursor particles is covered with Na 2 CO 3 Covered.

[0200] 1.3 Firing of the composite

[0201] The composite was placed in an alumina crucible and sintered in an air atmosphere to obtain an oxide containing Na and having a P2 type structure. The sintering conditions were as described below (1) to (5).

[0202] (1) An alumina crucible containing the above-mentioned composite is placed in a heating furnace in an air atmosphere.

[0203] (2) The temperature in the heating furnace was raised from room temperature (25°C) to 600°C over 115 minutes.

[0204] (3) The temperature in the heating furnace is maintained at 600° C. for 360 minutes for preliminary calcination.

[0205] (4) After the preliminary firing, the temperature in the heating furnace was raised to 900°C and maintained at 900°C for 60 minutes for the main firing.

[0206] (5) After the main firing, the temperature in the heating furnace was lowered from 900°C to 250°C, and the alumina crucible was taken out of the heating furnace at 250°C and allowed to cool outside the furnace in a dry atmosphere to 25°C over 10 minutes.

[0207] The fired product after cooling was pulverized using a mortar in a dry atmosphere to obtain Na-containing oxide particles having a P2 type structure (P2 type particles).

[0208] 1.4 Ion Exchange

[0209] (1) Weighing LiNO 3 The P2 type particles were mixed with LiCl at a molar ratio of 50:50 and a molar ratio of 10 times the minimum amount of Li required for ion exchange to obtain a mixture.

[0210] (2) Using an alumina crucible, ion exchange was performed in an air atmosphere at 280° C. for 1 hour to obtain a product containing an oxide containing Li.

[0211] (3) The salt remaining in the product was washed with pure water, and solid-liquid separation was performed by vacuum filtration to obtain a precipitate.

[0212] (4) The obtained precipitate was dried at 120°C overnight to obtain a positive electrode active material. The chemical composition of the positive electrode active material is Li 0.7 Mn 0.5 Ni 0.2 Co 0.3 O 2 In addition, the crystal phase contained in the positive electrode active material was confirmed by XRD, and as a result, the positive electrode active material had an O2 type structure. That is, the positive electrode active material had a Li-deficient O2 type structure.

[0213] 2. Preparation of Li-free (Li-doped) positive electrode active material

[0214] The above-mentioned positive electrode active material with a Li-deficient O2-type structure was doped with Li to produce a Li-non-deficient positive electrode active material. Specifically, 9-fluorenone was mixed in tetrahydrofuran (THF) in a glove box (Ar atmosphere) to a concentration of 1 mol / L, dissolved, and a fluorenone solution was obtained. Li foil in an amount equal to the mole of fluorenone was further added to the fluorenone solution and stirred for 2 hours to obtain a reduced solution containing 1 mol / L of Li ions. The above-mentioned positive electrode active material was added to the obtained reduced solution, immersed, and stirred for 24 hours. After stirring, the positive electrode active material was washed with THF, and solid-liquid separation was performed by vacuum filtration. The obtained precipitate was dried at 120°C overnight to obtain a Li-non-deficient positive electrode active material. The chemical composition of the positive electrode active material is Li 1.0 Mn 0.5 Ni 0.2 Co 0.3 O 2 In addition, the crystal phase contained in the positive electrode active material was confirmed by XRD, and as a result, the positive electrode active material had an O2 type structure.

[0215] 3. Preparation of positive electrode active material with O3 type structure

[0216] As a positive electrode active material having an O3 type structure without Li deficiency, a commercially available NCA-based positive electrode active material was prepared.

[0217] 4. Preparation of battery cells for evaluation

[0218] Using each of the above-mentioned positive electrode active materials, a battery cell for evaluation was produced. The production procedure of the battery cell for evaluation is as follows.

[0219] (1) The positive electrode active material and the sulfide solid electrolyte (Li 2 SP 2 S 5 -LiI-LiBr), PVDF, VGCF were weighed and mixed to form a positive electrode active material: sulfide solid electrolyte: PVDF: VGCF = 81.1: 15.9: 0.6: 2.4 (mass ratio), thereby obtaining a positive electrode composite. The obtained positive electrode composite was dispersed in a solvent (butyl butyrate) to obtain a positive electrode slurry. The obtained positive electrode slurry was applied to a positive electrode collector (Al foil) and dried. Then, a roll press was used to press at a pressing temperature shown in Table 1 below and with a linear pressure of 100 kN to form a positive electrode active material layer on the surface of the positive electrode collector.

[0220] (2) The negative electrode active material (lithium titanate) and the sulfide solid electrolyte (Li 2 SP 2 S 5-LiI-LiBr), PVDF and VGCF were weighed and mixed to form a negative electrode active material: sulfide solid electrolyte: PVDF: VGCF = 72.1: 22.7: 3.5: 1.7 (mass ratio), thereby obtaining a negative electrode composite. The obtained negative electrode composite was dispersed in a solvent (butyl butyrate) to obtain a negative electrode slurry. The obtained negative electrode slurry was applied to the negative electrode collector (Cu foil) and dried. Then, a negative electrode active material layer was formed on the surface of the negative electrode collector by roller pressing at room temperature (25°C) and a linear pressure of 60kN.

[0221] (3) Sulfide solid electrolyte (Li 2 SP 2 S 5 -LiI-LiBr), and acrylate butadiene rubber (ABR) were weighed and mixed so as to become sulfide solid electrolyte: ABR = 99.4:0.6 (mass ratio), thereby obtaining an electrolyte composite material.

[0222] (4) An electrolyte composite is sandwiched between the positive electrode active material layer and the negative electrode active material layer to obtain a laminate having a positive electrode collector, a positive electrode active material layer, a solid electrolyte layer, a negative electrode active material layer and a negative electrode collector in sequence. The obtained laminate is pressed at room temperature (25° C.) and a surface pressure of 50 kN to obtain a battery cell (solid battery) for evaluation.

[0223] 4. Raman and XPS measurements

[0224] In the glove box, the positive electrode current collector (Al foil) was peeled off from the above-mentioned evaluation battery cell to expose the positive electrode active material layer. Raman measurement and XPS measurement were performed on the outermost surface of the positive electrode active material layer to obtain the Raman spectrum and XPS spectrum (S2p, P2p). In addition, as a reference example, the positive electrode composite material was stacked on the surface of the positive electrode current collector without pressing, and the Raman spectrum and XPS spectrum of the positive electrode composite material were directly obtained. It should be noted that in the Raman measurement, 300cm -1 The intensity at 138 eV and 170 eV was normalized to 0 (background processing). In the XPS measurement, the peak intensities at 138 eV and 170 eV were normalized to 0 (background processing).

[0225] exist Figure 3 The Raman spectra of each of the embodiments, comparative examples and reference examples are shown in FIG. Figure 4 The XPS spectra (P2p) of the embodiments, comparative examples and reference examples are shown in FIG. Figure 5 The XPS spectra (S2p) of each of the examples, comparative examples and reference examples are shown in FIG.

[0226] As the Raman spectrum from P 2S 6 4- The peak intensity I R1 , determined to be 385cm -1 In addition, as the peak intensity from PS in this Raman spectrum 4 3- The peak intensity I R2 , determined 420cm -1 In addition, as the peak intensity I from SS in the Raman spectrum R3 , the Raman spectrum at 475 cm -1 The peak intensity ratio I is shown in the following Table 1. R1 / I R2 and I R3 / I R2 The respective calculation results.

[0227] As the peak intensity I from PSP in the XPS spectrum for S2p X1 , the peak intensity at 162.9 eV was determined. In addition, as the peak intensity from PS in the XPS spectrum for S2p 4 3- The peak intensity I X2 , the peak intensity at 161.6 eV was determined. The peak intensity ratio I is shown in the following Table 1 X1 / I X2 The calculation result of .

[0228] As for P2p, the XPS spectrum from PO x S 4-x 3- The peak intensity I X3 , the peak intensity at 133.6 eV was determined. In addition, as the peak intensity from PS in the XPS spectrum for P2p 4 3- The peak intensity I X4 , the peak intensity at 132.2 eV was determined. The peak intensity ratio I is shown in the following Table 1 X3 / I X4 The calculation result of .

[0229] 5. Evaluation of charge and discharge characteristics

[0230] For each evaluation battery cell, a charge and discharge test was performed for 2 cycles at 0.1C (1C = 220 mA / g) in a voltage range of 1.8-4.6V in a thermostatic chamber maintained at 25°C. Then, in a thermostatic chamber maintained at 25°C, a current equivalent to 3C was applied for 10 seconds at SOC50% (2.35V vs. LTO), thereby measuring the DCIR resistance. The measurement results are shown in Table 1 below.

[0231] 6. Evaluation results

[0232] For Examples 1 to 2 and Comparative Example 1 (a case where a positive electrode active material with a Li-deficient O2-type structure is used), Comparative Example 2 (a case where a positive electrode active material with a Li-free (Li-doped) O2-type structure is used), Comparative Example 3 (a case where a positive electrode active material with a Li-free O3-type structure is used), and Reference Example (positive electrode composite), the type of positive electrode active material, the presence or absence of pressing of the positive electrode composite and the pressing temperature, the peak intensity ratio I in the Raman spectrum are shown respectively. R1 / I R2 and I R3 / I R2 , the peak intensity ratio I in the XPS spectrum X1 / I X2 and I X3 / I X4 , and resistance measurement results.

[0233]

Table 1

[0234] (Table 1)

[0235]

[0236] From Table 1 and Figures 3 to 5 The results shown show the following.

[0237] I R1 / I R2 0.20 or less, I R3 / I R2 0.20 or less, I X1 / I X2 is less than 1.20, and I X3 / I X4 The evaluation battery cells according to Examples 1 and 2 with a value of 1.60 or less and I R1 / I R2 Greater than 0.20, I R3 / I R2 Greater than 0.20, I X1 / I X2 Greater than 1.20, I X3 / I X4 Compared with the evaluation battery cell involved in Comparative Example 1, which is greater than 1.60, it has a lower resistance. From the comparison between Examples 1 to 2 and Comparative Example 1, it can be seen that when the positive electrode active material having a Li-deficient O2-type structure is combined with a sulfide solid electrolyte in the positive electrode composite and the positive electrode composite is pressed at a temperature above 165°C, the positive electrode active material reacts with the sulfide solid electrolyte, and the PS of the sulfide solid electrolyte is 4The skeleton collapsed and byproducts were generated. In Comparative Example 1, it is considered that the resistance of the evaluation battery cell increased due to the byproducts.

[0238] On the other hand, in Comparative Examples 2 and 3 using a positive electrode active material with no Li deficiency, no by-products were observed even when the positive electrode composite was pressed at 165°C, and the PS of the sulfide solid electrolyte 4 That is, it can be understood that the problem of resistance increase caused by the reaction between the positive electrode active material and the sulfide solid electrolyte is unique to the case where a positive electrode active material having a Li-deficient O2-type structure and a sulfide solid electrolyte are combined in the positive electrode active material layer.

[0239] 7. Supplement

[0240] Furthermore, in the above-mentioned embodiment, as the positive electrode active material having a Li-deficient O2-type structure, a positive electrode active material having a specific chemical composition is exemplified, but the chemical composition of the positive electrode active material is not limited thereto. In addition, the chemical composition of the sulfide solid electrolyte is not limited to the above-mentioned chemical composition. It is believed that when a positive electrode active material having a Li-deficient O2-type structure and a sulfide solid electrolyte are used to form a positive electrode active material layer, the same effect can be achieved regardless of the chemical composition of the positive electrode active material and the sulfide solid electrolyte.

[0241] 8. Summary

[0242] As described above, in a lithium ion battery having a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, when the following characteristics (A) and (B) are satisfied, the lithium ion battery can be said to have a low resistance.

[0243] (A) The positive electrode active material layer includes a positive electrode active material having a Li-deficient O2-type structure and a sulfide solid electrolyte.

[0244] (B) The Raman spectrum of the positive electrode active material layer satisfies the following relations (1) and (2):

[0245] I R1 / I R2 ≤0.20···(1)

[0246] I R3 / I R2 ≤0.20···(2)

[0247] I R1 : The Raman spectrum from P 2 S 6 4- The peak intensity

[0248] I R2 : The Raman spectrum from PS 4 3- The peak intensity

[0249] I R3 : The peak intensity from SS in the Raman spectrum.

[0250] Furthermore, when the following feature (C) is satisfied in addition to the above features (A) and (B), it can be said that the lithium ion battery becomes a battery having lower resistance.

[0251] (C) The XPS spectrum of the positive electrode active material layer satisfies the following relations (3) and (4):

[0252] I X1 / I X2 ≤1.20···(3)

[0253] I X3 / I X4 ≤1.60···(4)

[0254] I X1 : The peak intensity from PSP in the XPS spectrum of S2p

[0255] I X2 : The XPS spectrum of S2p from PS 4 3- The peak intensity

[0256] I X3 : Regarding the XPS spectrum of P2p, the x S 4-x 3- The peak intensity

[0257] I X4 : The XPS spectrum of P2p from PS 4 3- The peak intensity.

Claims

1. A lithium-ion battery comprising a positive electrode active material layer, an electrolyte layer and a negative electrode active material layer, wherein the positive electrode active material layer comprises a positive electrode active material having a Li-deficient O2-type structure and a sulfide solid electrolyte, and the Raman spectrum of the positive electrode active material layer satisfies the following relationships (1) and (2): I R1 / I R2 ≤0.20 · · · (1) I R3 / I R2 ≤0.20 · · · (2) I R1 :The Raman spectrum from P2S6 4- The peak intensity I R2 : The Raman spectrum from PS4 3- The peak intensity I R3 : The peak intensity from SS in the Raman spectrum.

2. The lithium ion battery according to claim 1, wherein The XPS spectrum of the positive electrode active material layer satisfies the following relations (3) and (4): I X1 / I X2 ≤1.20 · · · (3) I X3 / I X4 ≤1.60 · · · (4) I X1 : The peak intensity from PSP in the XPS spectrum of S2p I X2 : The XPS spectrum of S2p from PS4 3- The peak intensity I X3 : Regarding the XPS spectrum of P2p, the x S 4-x 3- The peak intensity I X4 : The XPS spectrum of P2p from PS4 3- The peak intensity.

3. The lithium ion battery according to claim 1 or 2, wherein: When the entire solid content contained in the positive electrode active material layer is 100 mass %, the content of the positive electrode active material is 40 mass % or more and less than 100 mass %, and the content of the sulfide solid electrolyte is greater than 0 mass % and 60 mass % or less.

4. The lithium ion battery according to any one of claims 1 to 3, wherein The positive electrode active material has Li a Na b Mn x-p Ni y-q Co z-r M p+q+r O2 represents a chemical composition, wherein 0<a<1.00, 0≤b≤0.20, x+y+z=1, and 0≤p+q+r<0.17, and the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W.

5. The lithium ion battery according to any one of claims 1 to 4, wherein The electrolyte layer includes a solid electrolyte.

6. A method for manufacturing a lithium-ion battery, comprising: A positive electrode active material having a Li-deficient O2-type structure and a sulfide solid electrolyte are mixed to obtain a positive electrode composite material; and The positive electrode composite material is pressed at a temperature lower than 165° C. to obtain a positive electrode active material layer.

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