Positive electrode active material for lithium ion batteries, positive electrode material, solid-state battery, and method for producing positive electrode active material for lithium ion batteries

Abstract

To provide a cathode active material for lithium-ion batteries capable of obtaining a battery with high initial discharge capacity and high capacity retention after repeated charging and discharging, a cathode active material for sodium-ion batteries, a cathode material, a solid-state battery, and a manufacturing method of cathode active material for lithium-ion batteries.SOLUTION: The cathode active material for lithium-ion batteries is obtained, in which, in the X-ray diffraction measurement, three or more peaks exist in the 2θ range of 64° to 70°, and one peak exists in the 2θ range of 15° to 20°, and belongs to the space group Cmca. Also, a cathode active material for sodium-ion batteries, a cathode material, a solid-state battery, and a manufacturing method of cathode active material for lithium-ion batteries are provided.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present disclosure relates to a positive electrode active material for a lithium-ion battery, a positive electrode active material for a sodium-ion battery, a positive electrode material, a solid battery, and a method for manufacturing a positive electrode active material for a lithium-ion battery.

Background Art

[0002] A positive electrode active material having at least one structure selected from an O2-type structure, a T#2-type structure, and an O6-type structure is stable up to a high potential, and thus has a large charge-discharge capacity in charge-discharge in a high potential region. Patent Document 1 discloses "a positive electrode active material used in a non-aqueous electrolyte secondary battery, which has a layered structure and contains a lithium-containing transition metal oxide in which the main arrangement of transition metal, oxygen, and lithium is represented by an O2 structure, and the lithium-containing transition metal oxide has Li, Mn, and element M in a lithium-containing transition metal layer in the layered structure, and has a general composition formula Li x [Li α (Mn a M b ) 1-α O2, where 0.5 < x < 1.1, 0.1 < α < 0.33, 0.67 < a < 0.97, 0.03 < b < 0.33, and M contains at least one element selected from the group consisting of Ni, Mg, Ti, Fe, Sn, Zr, Nb, Mo, W, and Bi, a positive electrode active material for a non-aqueous electrolyte secondary battery." has been proposed. Further, Patent Document 2 discloses "a lithium-containing layered oxide Li a N ab M c O 2±αThe proposed positive electrode active material is characterized in that, in the following range, the potential P (V) of (0.5≦a≦1.3, 0≦b≦0.01, 0.90≦c≦1.10, 0≦α≦0.3, M=at least one element selected from manganese, cobalt, nickel, iron, aluminum, molybdenum, zirconium, and magnesium) is 4.8≦P≦5.0 (vs. Li / Li+), the molar ratios of lithium and M are a and c, respectively, and when c is converted to 1.0, the ratio of a is in the range of 0.08≦a≦0.12. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-186937 [Patent Document 2] Japanese Patent Application Laid-Open No. 2010-92824 Summary of the Invention [Problem to be solved by the invention]

[0004] A positive electrode active material having at least one structure selected from an O2-type structure, a T#2-type structure, and an O6-type structure undergoes structural changes between the O2-type structure, the T#2-type structure, and the O6-type structure upon discharge and charging. Specifically, the structure changes in the order of O2-type structure, T#2-type structure, O6-type structure, and O2-type structure from the side with a high Li content to the side with a low Li content. This structural change causes the volume of the positive electrode active material to expand and contract significantly, which can lead to cracks in the positive electrode active material. This disrupts the electron conduction pathway, which can lead to a decrease in capacity retention after repeated discharge and charging.

[0005] Therefore, an object of one embodiment of the present disclosure is to provide a positive electrode active material for a lithium ion battery that can provide a battery having a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. Another embodiment of the present disclosure aims to solve a problem by providing a positive electrode active material for a sodium ion battery that can provide a battery having a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. Another problem to be solved by another embodiment of the present disclosure is to provide a positive electrode material that can provide a battery having a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. Another problem to be solved by another embodiment of the present disclosure is to provide a solid-state battery that has a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. Another embodiment of the present disclosure aims to solve a problem by providing a method for producing a positive electrode active material that can yield a battery having a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. [Means for solving the problem]

[0006] The means for solving the above problems include the following means. <1> In the X-ray diffraction measurement results, there are three or more peaks in the 2θ range of 64° or more and 70° or less, and one peak in the 2θ range of 15° or more and 20° or less, A positive electrode active material for lithium-ion batteries that belongs to the space group Cmca. <2> It is a compound represented by the following formula 1 <1> The positive electrode active material for a lithium ion battery according to claim 1. Formula 1: LiaNabMnx-pNiy-qCoz-rMp+q+rO2 (In the above formula 1, a, b, x, y, z, p, q, and r are numbers that satisfy 0≦a≦1, 0≦b≦0.05, x+y+z=1, and 0≦p+q+r≦0.20, M represents at least one selected from the group consisting of B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo, and W. <3> A positive electrode active material for a sodium ion battery, which is a compound represented by the following formula 2: Formula 2: NacMnx-pNiy-qCoz-rMp+q+rO2 (In the above formula 2, c, x, y, z, p, q, and r are numbers that satisfy 0.5≦c≦0.65, x+y+z=1, and 0≦p+q+r≦0.20, M represents at least one selected from the group consisting of Li, B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo, and W. <4> <1> or <2> A positive electrode material comprising the positive electrode active material for a lithium ion battery according to claim 1. <5> <1> or <2> A solid-state battery comprising the positive electrode active material for a lithium ion battery according to claim 1. <6> A method for producing a positive electrode active material for a lithium ion battery, comprising a step of ion-exchanging Na contained in a compound represented by the following formula 2 with Li: Formula 2: NacMnx-pNiy-qCoz-rMp+q+rO2 (In the above formula 2, c, x, y, z, p, q, and r are numbers that satisfy 0.5≦c≦0.65, x+y+z=1, and 0≦p+q+r≦0.20, M represents at least one selected from the group consisting of Li, B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo, and W. [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, there is provided a positive electrode active material for a lithium ion battery that can provide a battery with a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. According to another embodiment of the present disclosure, there is provided a positive electrode active material for a sodium ion battery that enables the production of a battery having a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. According to another embodiment of the present disclosure, there is provided a positive electrode material that can provide a battery that has a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. According to another embodiment of the present disclosure, there is provided a solid state battery that has a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. According to another embodiment of the present disclosure, there is provided a method for producing a positive electrode active material that can yield a battery that has a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present disclosure will be described. These descriptions and examples are intended to illustrate the embodiment and are not intended to limit the scope of the invention. In the present specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range. In addition, in the present specification, the upper or lower limit of a numerical range may be replaced with a value shown in the examples.

[0010] Each component may contain multiple types of the corresponding substance. When referring to the amount of each component in a composition, if there are multiple substances corresponding to each component in the composition, the amount refers to the total amount of those multiple substances present in the composition, unless otherwise specified. The term "process" includes not only independent processes but also processes that cannot be clearly distinguished from other processes as long as the intended effect of the process is achieved.

[0011] <Positive electrode active material for lithium-ion batteries> In an X-ray diffraction measurement, the positive electrode active material for a lithium ion battery according to the present disclosure has three or more peaks in the 2θ range of 64° or more and 70° or less, and one peak in the 2θ range of 15° or more and 20° or less, and is assigned to the space group Cmca.

[0012] The positive electrode active material for a lithium ion battery according to the present disclosure has the above-described configuration, and is a positive electrode active material for a lithium ion battery that can provide a battery having a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. The reason for this is presumed to be as follows.

[0013] In X-ray diffraction analysis, the lithium-ion battery positive electrode active material according to the present disclosure exhibits three or more peaks in the 2θ range of 64° to 70° and one peak in the 2θ range of 15° to 20°, and is assigned to the space group Cmca. This configuration results in a structure of the lithium-ion battery positive electrode active material approaching a single-phase T#2 structure. This suppresses structural changes between the O2 structure and the T#2 structure. This suppresses volumetric expansion and contraction of the lithium-ion battery positive electrode active material associated with structural changes. This reduces cracking in the positive electrode active material and suppresses a decrease in capacity retention after repeated charge and discharge. Furthermore, the structure of the lithium-ion battery positive electrode active material approaching a single-phase T#2 structure increases charge and discharge capacities.

[0014] The positive electrode active material for a lithium ion battery according to the present disclosure will be described below.

[0015] (Peak positions in X-ray diffraction measurement results) In X-ray diffraction measurement of the positive electrode active material for a lithium ion battery according to the present disclosure, three or more peaks are present in the 2θ range of 64° or more and 70° or less, and one peak is present in the 2θ range of 15° or more and 20° or less. In order to obtain a positive electrode active material for a lithium ion battery having this configuration, it is preferable to manufacture it by the method for manufacturing a positive electrode active material for a lithium ion battery according to the present disclosure.

[0016] The number of peaks present in the 2θ range of 64° to 70° and the number of peaks present in the 2θ range of 15° to 20° are measured by X-ray diffraction measurement. An X-ray diffraction measurement device, model RINT-2000 manufactured by Rigaku Corporation, can be used. The measurement procedure is described below. X-ray diffraction measurements are performed at 0.01° steps and 0.1 seconds / step or faster so that 2θ is in the range of at least 10° to 70°. WP / R eFitting is performed using the Rietveld method so that the σ is 1.3 or less, and the number of peaks separated during this process is counted as the number of peaks. Fitting is performed over the entire measurement range, including the 2θ range of 10° to 70°. From the fitting results, the number of peaks present in the 2θ range of 64° to 70° and the number of peaks present in the 2θ range of 15° to 20° are calculated.

[0017] (space group) The positive electrode active material for a lithium ion battery according to the present disclosure belongs to the space group Cmca. Here, whether or not a positive electrode active material belongs to the space group Cmca is determined from the results of fitting by the Rietveld method described above. If phases belonging to the space group Cmca account for 90% or more by volume of the phases included in the results of fitting by the Rietveld method, the positive electrode active material is determined to belong to the space group Cmca. In the positive electrode active material for a lithium ion battery, the phase belonging to the space group Cmca preferably accounts for 95% or more, more preferably 98% or more, by volume.

[0018] (Composition formula of positive electrode active material for lithium-ion batteries) From the viewpoint of the initial discharge capacity and the capacity retention rate, the positive electrode active material for a lithium ion battery according to the present disclosure is preferably a compound represented by the following formula 1. Formula 1: Li a Na b Mn x-p Ni y-q Co z-r M p+q+r O2 In the above formula 1, a, b, x, y, z, p, q, and r are numbers that satisfy the conditions 0≦a≦1, 0≦b≦0.05, x+y+z=1, and 0≦p+q+r≦0.20, M represents at least one selected from the group consisting of B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo and W.

[0019] x is preferably a number that satisfies 0≦x≦1, and more preferably a number that satisfies 0.1≦x≦1. y is preferably a number that satisfies 0≦y≦0.5, and more preferably a number that satisfies 0≦y≦0.33. It is preferable that z is a number that satisfies 0≦z≦1, and it is more preferable that z is a number that satisfies 0≦z≦0.67. It is preferable that p is a number that satisfies 0≦p≦0.10. It is preferable that q is a number that satisfies 0≦q≦0.10. It is preferable that r is a number that satisfies 0≦r≦0.10.

[0020] The positive electrode active material according to the present disclosure is specifically Li 0.60 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O2, Li 0.50 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O2, Li 0.60 Na 0.05 Mn 0.50 Ni 0.20 Co 0.30 O2, Li 0.60 Na 0.00 Mn 0.67 Ni 0.33 O2, Li 0.60 Na 0.00 Mn 0.40 Ni 0.20 Co 0.30 Cr 0.10 O2, Li .60 Na 0.00 Mn 0.50 Ni 0.10 Co 0.30 Mg 0.10 O2 etc.

[0021] <Method of manufacturing positive electrode active material for lithium-ion batteries> The method for producing a positive electrode active material for a lithium ion battery according to the present disclosure includes a step of ion-exchanging Na contained in a compound represented by the following formula 2 with Li (ion-exchange step).

[0022] Formula 2: Na c Mn x-p Niy-q Co z-r M p+q+r O2 In the above formula 2, c, x, y, z, p, q, and r are numbers that satisfy 0.5≦c≦0.65, x+y+z=1, and 0≦p+q+r≦0.20, M represents at least one selected from the group consisting of Li, B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo, and W.

[0023] x is preferably a number that satisfies 0≦x≦1, and more preferably a number that satisfies 0.1≦x≦1. y is preferably a number that satisfies 0≦y≦0.5, and more preferably a number that satisfies 0≦y≦0.33. It is preferable that z is a number that satisfies 0≦z≦1, and it is more preferable that z is a number that satisfies 0≦z≦0.67. It is preferable that p is a number that satisfies 0≦p≦0.10. It is preferable that q is a number that satisfies 0≦q≦0.10. It is preferable that r is a number that satisfies 0≦r≦0.10.

[0024] (Na-doped precursor synthesis process) The method for producing a positive electrode active material for a lithium ion battery according to the present disclosure may, if necessary, include a step of synthesizing a compound represented by the above formula 2 (hereinafter also referred to as a Na-doped precursor). The Na-doped precursor is synthesized by a known method.

[0025] The Na-doped precursor is specifically Na 0.60 Mn 0.5 Ni 0.2 Co 0.3 O2, Na 0.50 Mn 0.50 Ni 0.20 Co 0.30 O2, Na 0.60 Mn 0.67 Ni 0.33 O2, Na 0.60 Mn 0.40 Ni 0.20 Co 0.30 Cr0.10 O2, Na 0.60 Mn 0.50 Ni 0.10 Co 0.30 Mg 0.10 Examples include O2.

[0026] (Ion exchange process) The ion exchange step is a step of ion-exchanging Na contained in the Na-doped precursor with Li. Ion exchange of the Na-doped precursor can be performed using a molten salt bed containing a mixture of lithium nitrate and lithium chloride. The temperature conditions during ion exchange are preferably in the range of not less than the temperature at which the molten salt bed melts but less than 320°C.

[0027] <Cathode active material for sodium ion batteries> The compound represented by the following formula 2 can be effectively used as a positive electrode active material for sodium ion batteries. Formula 2: Na c Mn x-p Ni y-q Co z-r M p+q+r O2 In the above formula 2, c, x, y, z, p, q, and r are numbers that satisfy 0.5≦c≦0.65, x+y+z=1, and 0≦p+q+r≦0.20, M represents at least one selected from the group consisting of Li, B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo, and W.

[0028] Specific examples of the positive electrode active material for a sodium ion battery according to the present disclosure include Na 0.60 Mn 0.5 Ni 0.2 Co 0.3 O2, Na 0.50 Mn 0.50 Ni 0.20 Co 0.30 O2, Na 0.60 Mn 0.67 Ni 0.33 O2, Na 0.60 Mn 0.40 Ni 0.20 Co 0.30 Cr 0.10 O2, Na0.60 Mn 0.50 Ni 0.10 Co 0.30 Mg 0.10 Examples include O2.

[0029] The positive electrode active material for a sodium ion battery according to the present disclosure can be used as a Na-doped precursor in the method for producing a positive electrode active material for a lithium ion battery according to the present disclosure.

[0030] <Cathode materials> The positive electrode material according to the present disclosure contains a positive electrode active material for lithium ion batteries, and may contain a conductive additive, a solid electrolyte, a binder, and other components as necessary.

[0031] (Positive electrode active material for lithium-ion batteries) The positive electrode active material for lithium ion batteries contained in the positive electrode material according to the present disclosure is the positive electrode active material for lithium ion batteries according to the present disclosure, and preferred aspects are also the same.

[0032] The positive electrode active material for lithium ion batteries contained in the positive electrode material according to the present disclosure may contain a positive electrode active material for lithium ion batteries other than the positive electrode active material for lithium ion batteries according to the present disclosure. Another positive electrode active material for a lithium ion battery preferably contains a lithium composite oxide. The lithium composite oxide may contain at least one element selected from the group consisting of F, Cl, N, S, Br, and I. The lithium composite oxide may have a crystal structure belonging to at least one space group selected from the space groups R-3m, Immm, and P63-mmc (also referred to as P63mc or P6 / mmc). The lithium composite oxide may have an O2-type structure in which the transition metal, oxygen, and lithium are primarily arranged.

[0033] Examples of lithium composite oxides having a crystal structure belonging to R-3m include Li x Me y O α X β(Me represents at least one selected from the group consisting of Mn, Co, Ni, Fe, Al, Cu, V, Nb, Mo, Ti, Cr, Zr, Zn, Na, K, Ca, Mg, Pt, Au, Ag, Ru, W, B, Si, and P, and X represents at least one selected from the group consisting of F, Cl, N, S, Br, and I, and satisfy the conditions 0.5≦x≦1.5, 0.5≦y≦1.0, 1≦α<2, and 0<β≦1.)

[0034] Examples of lithium composite oxides having a crystal structure belonging to Immm include Li x1 M 1 A 1 2(1.5≦x1≦2.3, M 1 contains at least one selected from the group consisting of Ni, Co, Mn, Cu and Fe, and A 1 contains at least oxygen, and A 1 The ratio of oxygen in the oxide is 85 atomic % or more. x1 M 1A 1-x2 M 1B x2 O 2-y A 2 y (0≦x2≦0.5, 0≦y≦0.3, and at least one of x2 and y is not 0, M 1A represents at least one selected from the group consisting of Ni, Co, Mn, Cu, and Fe, and M 1B represents at least one selected from the group consisting of Al, Mg, Sc, Ti, Cr, V, Zn, Ga, Zr, Mo, Nb, Ta and W, and A2 represents at least one selected from the group consisting of F, Cl, Br, S and P.

[0035] Examples of lithium composite oxides having a crystal structure belonging to P63-mmc include M1 x M2 yO2 (where M1 represents an alkali metal (preferably at least one of Na and K), M2 represents a transition metal (preferably at least one selected from the group consisting of Mn, Ni, Co, and Fe), and 0 < x + y ≦ 2). Examples of the composite oxide include those represented by this formula.

[0036] As the lithium composite oxide having an O2-type structure, for example, Li x [Li α (Mn a Co b M c ) 1-α O2 (where 0.5 < x < 1.1, 0.1 < α < 0.33, 0.17 < a < 0.93, 0.03 < b < 0.50, 0.04 < c < 0.33, and M represents at least one selected from the group consisting of Ni, Mg, Ti, Fe, Sn, Zr, Nb, Mo, W, and Bi). Examples of such composite oxides include Li 0.744 [Li 0.145 Mn 0.625 Co 0.115 Ni 0.115 O2, etc.

[0037] A more preferred embodiment is that at least a part of the surface of the positive electrode active material is coated with a sulfide solid electrolyte, an oxide solid electrolyte, or a halide solid electrolyte. As the halide solid electrolyte for coating at least a part of the surface of the positive electrode active material, Li 6-(4-x)b (Ti 1-x Al x ) b F6 (where 0 < x < 1, 0 < b ≦ 1.5) [LTAF electrolyte] is preferred.

[0038] (Conductive aid) Examples of the conductive aid include carbon materials, metal materials, and conductive polymer materials. Examples of the carbon materials include carbon black (e.g., acetylene black, furnace black, ketjen black, etc.), fibrous carbon (e.g., vapor-grown carbon fiber, carbon nanotube, carbon nanofiber, etc.), graphite, carbon fluoride, etc. Examples of the metal materials include metal powder (e.g., aluminum powder, etc.), conductive whiskers (e.g., zinc oxide, potassium titanate, etc.), conductive metal oxides (e.g., titanium oxide, etc.), etc. Examples of the conductive polymer materials include polyaniline, polypyrrole, polythiophene, etc. The conductive aid may be used alone as only one kind, or may be used by mixing two or more kinds.

[0039] (Solid electrolyte) As the solid electrolyte, it is preferable to contain at least one solid electrolyte species selected from the group of solid electrolytes consisting of sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes.

[0040] As the sulfide solid electrolyte, it preferably contains sulfur (S) as the main component of the anion element, and further preferably contains, for example, Li element and A element. The A element is at least one selected from the group consisting of P, As, Sb, Si, Ge, Sn, B, Al, Ga, and In. The sulfide solid electrolyte may further contain at least one of O and halogen elements. Examples of the halogen element (X) include F, Cl, Br, I, etc. The composition of the sulfide solid electrolyte is not particularly limited, and examples include xLi2S·(100 - x)P2S5 (70 ≤ x ≤ 80), yLiI·zLiBr·(100 - y - z)(xLi^2S·(1 - x)P2S5) (0.7 ≤ x ≤ 0.8, 0 ≤ y ≤ 30, 0 ≤ z ≤ 30). The sulfide solid electrolyte may have a composition represented by the following general formula (1). Li 4-x Ge 1-x P x S4(0 < x < 1) ··· Formula (1) In formula (1), at least a portion of the Ge may be substituted with at least one selected from the group consisting of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. At least a portion of the P may be substituted with at least one selected from the group consisting of Sb, Si, Sn, B, Al, Ga, In, Ti, Zr, V, and Nb. At least a portion of the Li may be substituted with at least one selected from the group consisting of Na, K, Mg, Ca, and Zn. At least a portion of the S may be substituted with a halogen. The halogen is at least one of F, Cl, Br, and I.

[0041] The oxide solid electrolyte contains oxygen (O) as the main anion element, and may also contain Li and Q elements (Q represents at least one of Nb, B, Al, Si, P, Ti, Zr, Mo, W, and S). Examples of the oxide solid electrolyte include garnet-type solid electrolytes, perovskite-type solid electrolytes, Nasicon-type solid electrolytes, Li-PO-based solid electrolytes, and Li-BO-based solid electrolytes. Examples of the garnet-type solid electrolyte include Li7La3Zr2O 12 , Li 7-x La3(Zr 2-x Nb x )O 12 (0≦x≦2), Li5La3Nb2O 12 Examples of perovskite-type solid electrolytes include (Li,La)TiO3, (Li,La)NbO3, (Li,Sr)(Ta,Zr)O3, etc. Examples of Nasicon-type solid electrolytes include Li(Al,Ti)(PO4)3, Li(Al,Ga)(PO4)3, etc. Examples of Li-PO-based solid electrolytes include Li3PO4 and LIPON (a compound in which part of the O in Li3PO4 is substituted with N), and examples of Li-BO-based solid electrolytes include Li3BO3 and a compound in which part of the O in Li3BO3 is substituted with C, etc.

[0042] As the halide solid electrolyte, a solid electrolyte containing Li, M, and X (M represents at least one of Ti, Al, and Y, and X represents F, Cl, or Br) is suitable. 6-3z Y zX6 (where X represents Cl or Br, and z satisfies 0 < z < 2), Li 6-(4-x)b (Ti 1-x Al x ) b F6 (0 < x < 1, 0 < b ≤ 1.5) is preferred. Li 6-3z Y z Among X6, Li3YX6 (where X represents Cl or Br) is more preferred in terms of excellent lithium ion conductivity, and further Li3YCl6 is preferred. Also, Li 6-(4-x)b (Ti 1-x Al x ) b F6 (0 < x < 1, 0 < b ≤ 1.5) is preferably included together with a solid electrolyte such as a sulfide solid electrolyte from the viewpoint of, for example, suppressing the oxidative decomposition of the sulfide solid electrolyte.

[0043] (Binder) Examples of the binder include vinyl halide resins, rubbers, polyolefin resins, etc. Examples of the vinyl halide resin include polyvinylidene fluoride (PVdF), a copolymer of polyvinylidene fluoride and hexafluoropropylene (PVdF-HFP), etc. Examples of the polyolefin resin include butadiene rubber (BR), acrylate butadiene rubber (ABR), styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butyl rubber (isobutylene-isoprene rubber), etc. Examples of the polyolefin resin include polyethylene, polypropylene, etc. The binder may be a diene-based rubber containing a double bond in the main chain, for example, a butadiene-based rubber in which butadiene occupies 30 mol% or more of the whole.

[0044] (Other components) Examples of other components include oxide solid electrolytes, halide solid electrolytes, thickeners, surfactants, dispersants, wetting agents, defoamers, solvents, etc.

[0045] <Solid battery> The solid battery according to the present disclosure contains the positive electrode active material for a lithium ion battery according to the present disclosure. The solid-state battery according to the present disclosure preferably includes a positive electrode layer, a negative electrode layer, and an electrolyte layer or a separator disposed between the positive electrode layer and the negative electrode layer, and the positive electrode layer preferably contains the positive electrode material according to the present disclosure.

[0046] (Battery structure) Solid-state batteries include so-called all-solid-state batteries (in which the content of electrolytic solution as electrolyte is less than 10 mass % of the total amount of electrolyte) that use an inorganic solid electrolyte as the electrolyte. The structure of the solid-state battery of the present disclosure may include a positive electrode current collector, a positive electrode layer, a solid electrolyte layer, a negative electrode layer, and a negative electrode current collector in this order, for example, as shown in FIG. 1. The solid electrolyte layer B in FIG. 1 may have a two-layer structure. FIG. 1 is a schematic cross-sectional view showing an example of a solid-state battery. The solid-state battery shown in FIG. 1 includes an anode including a negative electrode current collector 113 and a negative electrode layer A, a solid electrolyte layer B, a positive electrode including a positive electrode current collector 115 and a positive electrode layer C, and anode layer A. The negative electrode layer A includes a negative electrode active material 101, a conductive additive 105, a binder 109, and a solid electrolyte 102. The positive electrode layer C includes a positive electrode active material 103, a binder 111, and a solid electrolyte 102.

[0047] When a set of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is defined as a power generation unit, the solid-state battery may have only one power generation unit or may have two or more power generation units. When the solid-state battery has two or more power generation units, the power generation units may be connected in series or in parallel.

[0048] The solid-state battery may be configured by sealing the end faces (side faces) of the stacked structure of the positive electrode layer / solid electrolyte layer / negative electrode layer with resin. The electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface. The shape of the solid-state battery is not particularly limited, and may be, for example, a coin type, a cylindrical type, a square type, a sheet type, a button type, a flat type, or a laminate type.

[0049] (Electrolyte layer and separator) A solid-state battery includes an electrolyte layer or separator.

[0050] The electrolyte layer may be a layer containing a solid electrolyte. In the case of a layer containing a solid electrolyte (solid electrolyte layer), the solid electrolyte layer preferably contains one selected from the group consisting of a sulfide solid electrolyte, an oxide solid electrolyte, and a halide solid electrolyte. Specific examples of the sulfide solid electrolyte, oxide solid electrolyte, and halide solid electrolyte are the same as those described above.

[0051] The solid electrolyte layer may have a single layer structure or a multi-layer structure of two or more layers.

[0052] The solid electrolyte layer may contain a binder, or may not contain a binder. The binder that can be contained in the solid electrolyte layer is the same as the binder described above.

[0053] As the separator, a porous sheet (film) made of a resin such as polyethylene (PE), polypropylene (PP), polyester, cellulose, or polyamide can be used.

[0054] (positive electrode layer) The solid-state battery includes a positive electrode layer, which includes the positive electrode material of the present disclosure.

[0055] (Positive electrode current collector) The solid-state battery may further include a positive electrode current collector. The positive electrode current collector collects current from the positive electrode layer. The positive electrode current collector is disposed on the opposite side of the positive electrode layer from the electrolyte layer (or separator). The positive electrode current collector may be made of, for example, stainless steel, aluminum, copper, nickel, iron, titanium, or carbon, and is preferably an aluminum alloy foil or aluminum foil. The aluminum alloy foil or aluminum foil may be manufactured using powder. The positive electrode current collector may be, for example, in the form of a foil or a mesh. The positive electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface thereof.

[0056] (negative electrode layer) The solid-state battery includes a negative electrode layer. The negative electrode layer contains a negative electrode active material. The negative electrode layer may contain at least one of a negative electrode solid electrolyte, a conductive additive, and a binder, as needed. Examples of negative electrode active materials include Li-based active materials such as metallic lithium, carbon-based active materials such as graphite, oxide-based active materials such as lithium titanate, and Si-based active materials such as elemental Si. The conductive additive, negative electrode solid electrolyte, and binder used in the negative electrode layer may be the same as those exemplified as the conductive additive contained in the positive electrode layer, the solid electrolyte contained in the solid electrolyte layer, and the binder.

[0057] (Negative electrode current collector) The solid-state battery may further include a negative electrode current collector. The negative electrode current collector collects current from the negative electrode layer. The negative electrode current collector is disposed on the opposite side of the negative electrode layer from the electrolyte layer (or separator). The negative electrode current collector may be made of, for example, stainless steel, aluminum, copper, nickel, iron, titanium, or carbon, with copper being preferred. The negative electrode current collector may be in the form of, for example, a foil or mesh. The negative electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on the surface thereof.

[0058] <Solid-state battery manufacturing method> A method for manufacturing a solid-state battery according to the present disclosure includes: a step of preparing a positive electrode layer, a negative electrode layer, and an electrolyte layer or a separator (preparation step); and a step of laminating a positive electrode layer, an electrolyte layer or a separator, and a negative electrode layer in this order (lamination step).

[0059] (preparation process) The preparation step is a step of preparing a positive electrode layer, a negative electrode layer, and an electrolyte layer or a separator.

[0060] The method for producing the positive electrode layer, the negative electrode layer, and the electrolyte layer is not particularly limited, and they are preferably produced by kneading components that can be contained in the positive electrode layer, the negative electrode layer, and the electrolyte layer to obtain a slurry, applying the slurry to a substrate, and pressing the dried film obtained by drying. The method for kneading the components that can be contained in the positive electrode layer when obtaining the slurry is not particularly limited, and examples thereof include a method of kneading using a kneading device, such as an ultrasonic homogenizer, a shaker, a thin film rotary mixer, a dissolver, a homomixer, a kneader, a roll mill, a sand mill, an attritor, a ball mill, a vibrator mill, or a high-speed impeller mill.

[0061] Methods for pressing the dried film include roll pressing and cold isostatic pressing (CIP).

[0062] The pressure during pressing is preferably 0.1 t / cm 2 More than 0.5t / cm 2 More preferably, 1 t / cm 2 The pressure during pressing is preferably 10 t / cm 2 Less than 8t / cm, preferably 8t / cm 2 Less than 6t / cm, more preferably 2 The following is the result.

[0063] A commercially available porous sheet (film) can be used as the separator.

[0064] (Lamination process) The lamination step is a step of laminating a positive electrode layer, an electrolyte layer or a separator, and a negative electrode layer in this order. In the lamination step, the positive electrode layer prepared in the preparation step, the electrolyte layer or separator, and the negative electrode layer are preferably laminated in this order, and pressed as necessary to obtain a laminate (electrode body).

[0065] It is preferable to fabricate the solid state battery according to the present disclosure through the above steps. [Example]

[0066] Examples will be described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, all "parts" and "%" are by mass.

[0067] Example 1 [Manufacturing positive electrode active materials for lithium-ion batteries] (Na-doped precursor synthesis process) Mn(NO3)2·6H2O, Ni(NO3)2·6H2O, and Co(NO3)2·6H2O were used as raw materials and dissolved in pure water to a molar ratio of Mn, Ni, and Co of 5:2:3. A 12% by mass Na2CO3 solution was prepared, and these two solutions were simultaneously titrated into a beaker. The titration rate was controlled so that the pH was between 7.0 and 7.1. After the titration, the mixed solution was stirred at 50°C and 300 rpm for 24 hours. The resulting reaction product was washed with pure water, and the precipitated powder was separated by centrifugation. The resulting powder was dried at 120°C for 48 hours and then crushed in an agate mortar to obtain a powder (hereinafter referred to as the "intermediate powder"). The obtained intermediate powder was mixed with Na2CO3 in a composition ratio of Na 0.60 Mn 0.5 Ni 0.2 Co 0.3 The mixed powder was pressed under a load of 2 tons by cold isostatic pressing to produce pellets. The pellets were pre-baked in air at 600°C for 6 hours and then sintered at 700°C for 24 hours. After that, they were cooled to 250°C at a rate of 3°C / min and allowed to cool to obtain the Na-doped precursor (Na 0.60 Mn 0.5 Ni 0.2 Co 0.3 O2) was synthesized.

[0068] (Ion exchange process) LiNO3 and LiCl were mixed at a mass ratio of 88:12 to obtain a mixed powder. The Na-doped precursor was weighed so that the ratio of the number of moles of Li contained in the mixed powder was 10 times the number of moles of Na-doped precursor. The Na-doped precursor and the mixed powder were mixed, and ion exchange was carried out in air at 280°C for 1 hour. After the ion exchange, water was added to dissolve the salt, and the mixture was washed with water to obtain a positive electrode active material for lithium-ion batteries with an O2 structure (Li 0.58 Mn 0.50 Ni 0.20 Co 0.30 O2) was obtained.

[0069] [Solid-state battery manufacturing] (preparation process) -Preparation of the positive electrode layer- 85 g of positive electrode active material 1 for sodium ion batteries (powdered by ball milling) and 10 g of carbon black (conductive additive) were added to 125 mL of n-methylpyrrolidone solution containing 5 g of polyvinylidene fluoride (PVDF) as a binder, and the mixture was kneaded until uniformly mixed to prepare a slurry. This slurry was applied to a 15 μm thick Al positive electrode current collector as a substrate in a weight ratio of 6 mg / cm. 2 The electrode was then pressed to a thickness of 45 μm and a density of 2.4 g / cm. 3 Finally, this electrode was cut into a piece having a diameter of 16 mm to obtain a positive electrode having a positive electrode layer and a positive electrode current collector.

[0070] -Preparation of the negative electrode layer- The Li foil was cut to a diameter of 19 mm to obtain a negative electrode layer.

[0071] -Preparing the separator- A porous PP sheet was prepared as a separator.

[0072] (Lamination process) A positive electrode, a separator, and a negative electrode layer were stacked in this order to obtain a laminate. The positive electrode was stacked so that the positive electrode layer faced the separator. The laminate and a nonaqueous electrolyte (a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate) in a volume ratio of 3:7, with lithium hexafluorophosphate (LiPF6) dissolved at a concentration of 1 mol / L as a supporting electrolyte) were placed in a coin cell to prepare a CR2032 coin cell battery.

[0073] <Example 2> [Manufacturing positive electrode active materials for lithium-ion batteries] In the (Na-doped precursor synthesis step), Na2CO3 was added to the intermediate powder, and Na 0.50 Mn 0.5 Ni 0.2 Co 0.3 A positive electrode active material for a lithium ion battery was obtained in the same manner as in Example 1, except that the sodium ion battery positive electrode active material was added so that the total amount of the positive electrode active material was O2. 0.52 Mn 0.50 Ni 0.20 Co 0.30 O2).

[0074] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries 2 in the (preparation step) - preparation of the positive electrode layer.

[0075] <Comparative Example 1> [Manufacturing positive electrode active materials for lithium-ion batteries] In the (Na-doped precursor synthesis step), Na2CO3 was added to the intermediate powder, and Na 0.70 Mn 0.5 Ni 0.2 Co 0.3 A positive electrode active material for a lithium ion battery was obtained in the same manner as in Example 1, except that the positive electrode active material for a lithium ion battery was added so that the amount of O2 was 0. 0.67 Mn 0.50 Ni 0.20 Co 0.30O2).

[0076] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that in the (preparation step) - preparation of the positive electrode layer -, the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries C1.

[0077] <Comparative Example 2> [Manufacturing positive electrode active materials for lithium-ion batteries] In the (Na-doped precursor synthesis step), Na2CO3 was added to the intermediate powder, and Na 0.40 Mn 0.5 Ni 0.2 Co 0.3 A positive electrode active material for a lithium ion battery was obtained in the same manner as in Example 1, except that the positive electrode active material for a lithium ion battery was added so that the amount of O2 was 0. 0.48 Mn 0.50 Ni 0.20 Co 0.30 O2).

[0078] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that in the (preparation step) - preparation of the positive electrode layer -, the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries C2.

[0079] <Comparative Example 3> [Manufacturing positive electrode active materials for lithium-ion batteries] In the (Na-doped precursor synthesis step), Na2CO3 was added to the intermediate powder, and Na 0.65 Mn 0.5 Ni 0.2 Co 0.3 A positive electrode active material for a lithium ion battery was obtained in the same manner as in Example 1, except that the positive electrode active material for a lithium ion battery was added so that the amount of O2 was 0. 0.62 Mn 0.50 Ni 0.20 Co 0.30 O2).

[0080] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that in the (preparation step) - preparation of the positive electrode layer -, the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries C3.

[0081] <Comparative Example 4> [Manufacturing positive electrode active materials for lithium-ion batteries] Lithium carbonate (Li2CO3), manganese oxide (MnO2), nickel oxide (NiO), and cobalt oxide (Co2O3) were mixed in a ball mill. The mixture was pressed under a load of 2 tons using cold isostatic pressing to produce pellets. The pellets were then fired in air at 1000°C for 24 hours to produce the cathode active material C4 for lithium-ion batteries (Li 1.0 Mn 0.33 Ni 0.33 Co 0.33 O2) was obtained.

[0082] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that in the (preparation step) - preparation of the positive electrode layer -, the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries C4.

[0083] <Comparative Example 5> [Manufacturing positive electrode active materials for lithium-ion batteries] Lithium nitrate (LiNO3) was used as the positive electrode active material C5 for lithium ion batteries.

[0084] [Solid-state battery manufacturing] A coin cell battery was produced in the same manner as in Example 1, except that in the (preparation step) - preparation of the positive electrode layer -, the positive electrode active material for lithium ion batteries 1 was changed to the positive electrode active material for lithium ion batteries C5.

[0085] <Evaluation> (Peak positions and space groups in X-ray diffraction measurement results) The results of calculations according to the procedures described above for the "number of peaks present in the 2θ range of 64° or more and 70° or less," "number of peaks present in the 2θ range of 15° or more and 20° or less," and "space group" of the sodium ion battery positive electrode active material contained in the battery obtained in each example are shown in Table 1.

[0086] (Initial discharge capacity) A charge-discharge test was carried out using a galvanostat under the conditions of a current of 0.1 C, a charge cut-off voltage of 4.8 V, and a discharge cut-off voltage of 2.0 V. Starting with charging, after the first charge was completed, the amount of current required for discharging down to 2.0 V was calculated, and the initial discharge capacity was calculated by dividing this by the weight of the active material used in the measurement.

[0087] (Capacity retention rate after 20 cycles) A charge-discharge test was carried out under the same conditions as above, and the first discharge capacity and the 20th discharge capacity were calculated. The 20th discharge capacity was divided by the first discharge capacity to obtain the capacity retention rate after 20 cycles.

[0088] [Table 1]

[0089] In Table 1, "Number of peaks at 2θ=64° to 70°" means the number of peaks present in the 2θ range of 64° or more and 70° or less. In Table 1, "Number of peaks at 2θ=15° to 20°" means the number of peaks present in the 2θ range of 15° or more and 20° or less.

[0090] From the above results, it is understood that the positive electrode active material for a lithium ion battery of this example can provide a battery having a high initial discharge capacity and a high capacity retention rate after repeated discharge and charge. [Explanation of symbols]

[0091] A negative electrode layer B Solid electrolyte layer C positive electrode layer 101 Negative electrode active material 102 Solid electrolyte 103 Cathode active material 105 Conductive additives 109,111 binders 113 Negative electrode current collector 115 Positive electrode current collector

Claims

1. In the X-ray diffraction measurement results, there are three or more peaks in the 2θ range of 64° or more and 70° or less, and there is one peak in the 2θ range of 15° or more and 20° or less, It is assigned to the space group Cmca, A positive electrode active material for a lithium ion battery, comprising Li, Ni, Co and Mn.

2. The positive electrode active material for a lithium ion battery according to claim 1, which is a compound represented by the following formula 1: Formula 1: Li ａ Na ｂ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (In the above formula 1, a, b, x, y, z, p, q, and r are numbers that satisfy 0<a≦1, 0≦b≦0.05, x+y+z=1, and 0≦p+q+r≦0.20, M represents at least one element selected from the group consisting of B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo, and W.

3. A positive electrode material comprising the positive electrode active material for a lithium ion battery according to claim 1 or 2.

4. A solid-state battery comprising the positive electrode active material for a lithium ion battery according to claim 1 or 2.

5. A method for producing a positive electrode active material for a lithium ion battery according to claim 1, comprising: A method for producing a positive electrode active material for a lithium ion battery, comprising a step of ion-exchanging Na contained in a compound represented by the following formula 2 with Li: Formula 2: Na ｃ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (In the above formula 2, c, x, y, z, p, q, and r are numbers that satisfy 0.5≦c≦0.65, x+y+z=1, and 0≦p+q+r≦0.20, M represents at least one element selected from the group consisting of Li, B, Mg, Al, K, Ca, Ti, Cr, Ga, Zr, Nb, Mo, and W.

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