Positive electrode active material and method for manufacturing positive electrode active material

Abstract

To provide a positive electrode material capable of obtaining a battery with a high initial discharge capacity and a high capacitance maintaining ratio after repetition of a charging and a discharging, a positive electrode, a solid-state battery, and a manufacturing method of the positive electrode material.SOLUTION: The present invention provides a positive electrode material, a positive electrode, a solid-state battery, and a manufacturing method of the positive electrode material, satisfying the following condition 1 and the following condition 2 by an X-ray photoelectron spectroscopy of an oxygen atom 1s orbit obtained by an X-ray photoelectron spectroscopy measurement. The condition 1 is that a peak top of a binding energy is not existed in a region that is 525 eV or more and is less than 531 eV, and the peak top of the binding energy is existed in the region that is 531 eV or more and is less than 538 eV. The condition 2 is that a ratio of a discharge photoelectron intensity Ihe in the peak top existed in the region of which the binding energy is 531 eV or more and is 538 eV or less against a discharge photoelectron intensity Ile is 525 eV or more and is less than 531 eV is 1 or more.SELECTED DRAWING: Figure 1

Description

Technical Field

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

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. 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±α (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, magnesium). When the potential P(V) is in the range of 4.8 ≦ P ≦ 5.0 (vs. Li / Li+), and the molar ratios of lithium and M are a and c, respectively, and c is converted to 1.0, the ratio of a is in the range of 0.08 ≦ a ≦ 0.12. A positive electrode active material for a non-aqueous electrolyte secondary battery." has been proposed.

Prior Art Documents

[0003] [Patent Document 1] Japanese Patent Publication No. 2014-186937 [Patent Document 2] Japanese Patent Publication No. 2010-92824 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] Positive electrode active materials having at least one structure selected from O2-type, T#2-type, and O6-type structures expand and contract during charging and discharging, which can cause cracks in the positive electrode active material. This disrupts the electron conduction paths, leading to a decrease in capacity retention after repeated charging and discharging.

[0005] Therefore, one embodiment of this disclosure aims to solve the problem of providing a positive electrode active material that can produce a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. Another embodiment of the present disclosure aims to solve the problem of providing a positive electrode that yields a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. Another embodiment of the present disclosure aims to solve the problem of providing a solid-state battery that has a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. Another embodiment of the present disclosure aims to solve the problem of a positive electrode active material that can be obtained to produce a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. [Means for solving the problem]

[0006] The means to solve the above problems include the following: <1> A positive electrode active material whose X-ray photoelectron spectroscopy spectrum of the oxygen atom 1s orbital, obtained by X-ray photoelectron spectroscopy, satisfies either condition 1 or condition 2 below. Condition 1: No peak top exists in the region where the bond energy is between 525 eV and 531 eV, and a peak top exists in the region where the bond energy is between 531 eV and 538 eV. Condition 2: Emitted photoelectron intensity I at the peak top where the binding energy is in the region between 525 eV and 531 eV le The emitted photoelectron intensity I at the peak top where the binding energy is in the region between 531 eV and 538 eV is relative to the bound energy. he The ratio is 1 or greater. <2> The compound is represented by the following formula 1. <1> The positive electrode active material described above. Equation 1: Li a Na b Mn x-p Ni y-q Co z-r M p+q+r O 2ーδ (In equation 1 above, a, b, x, y, z, p, q, r, and δ are numbers that satisfy 0≦a≦1, 0≦b≦0.05, x+y+z=1, 0≦p+q+r≦0.20, and 0≦δ≦0.3.) 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> In the above formula 1, M is Al. <2> The positive electrode active material described above. <4> A positive electrode layer containing a positive electrode active material, It has a positive electrode current collector, A positive electrode in which, after being placed in a battery and subjected to discharge and charging, kink bands are formed on 10% or more of the positive electrode active material. <5> The content of the positive electrode active material is 70% by mass or more of the total positive electrode layer. <4> The positive electrode as described. <6> <1> ~ <3> Contains a positive electrode active material as described in any one of the following: <4> The positive electrode as described. <7> <4> ~ <6> A solid-state battery having a positive electrode as described in any one of the following. <8> The first step is to heat a compound represented by the following formula 2 at 400°C or higher to obtain a Na-doped precursor, or to obtain a Na-doped precursor represented by the following formula 3, A method for producing a positive electrode active material, comprising the step of ion-exchanging Na contained in the Na-doped precursor for Li. Equation 2: Na c Mn x-p Ni y-q Co z-r M p+q+r O2 (In equation 2 above, 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. Equation 3: Na c Mn x-p Ni y-q Co z-r Al p+q+r O2 (In equation 3 above, c, x, y, z, p, q, and r are numbers that satisfy 0.5 ≤ c ≤ 0.65, x + y + z = 1, and 0.05 ≤ p + q + r ≤ 0.20.) [Effects of the Invention]

[0007] According to one embodiment of the present disclosure, a positive electrode active material is provided that yields a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. According to another embodiment of the present disclosure, a positive electrode is provided that yields a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging cycles. According to another embodiment of the present disclosure, a solid-state battery is provided that has a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. Another embodiment of the present disclosure provides a method for manufacturing a positive electrode active material that yields a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging cycles. [Brief explanation of the drawing]

[0008] [Figure 1] Figure 1 is a schematic cross-sectional view showing an example of a solid-state battery. [Modes for carrying out the invention]

[0009] The following describes an example of an embodiment of this disclosure. These descriptions and examples are illustrative and do not limit the scope of the invention. In numerical ranges described stepwise within this specification, the upper or lower limit of one numerical range may be replaced with the upper or lower limit of another numerical range described stepwise. Furthermore, in numerical ranges described within this specification, the upper or lower limit of that range may be replaced with the values ​​shown in the examples.

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

[0011] <Cathode active material> The positive electrode active material relating to this disclosure is a positive electrode active material whose X-ray photoelectron spectroscopy spectrum of the oxygen atom 1s orbital, obtained by X-ray photoelectron spectroscopy measurement, satisfies either condition 1 or condition 2 below. Condition 1: No peak top exists in the region where the bond energy is between 525 eV and 531 eV, and a peak top exists in the region where the bond energy is between 531 eV and 538 eV. Condition 2: Emitted photoelectron intensity I at the peak top where the binding energy is in the region between 525 eV and 531 eV le The emitted photoelectron intensity I at the peak top where the binding energy is in the region between 531 eV and 538 eV is relative to the bound energy. he The ratio is 1 or greater.

[0012] The positive electrode active material relating to this disclosure, with the above configuration, is a positive electrode active material that can produce a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. The reason for this is presumed to be as follows.

[0013] Positive electrode active materials whose X-ray photoelectron spectroscopy spectrum of the oxygen atom 1s orbital, obtained by X-ray photoelectron spectroscopy, satisfies either condition 1 or condition 2 above, are prone to kink formation when charged and discharged. Therefore, even if cracks occur in the positive electrode active material due to expansion and contraction caused by charging and discharging, the conductive path is less likely to be interrupted, the decrease in capacity retention rate after repeated charging and discharging is suppressed, and the initial discharge capacity is increased.

[0014] (X-ray photoelectron spectroscopy spectrum of the oxygen atom's 1s orbital) The positive electrode active material relating to this disclosure satisfies either condition 1 or condition 2 below when the X-ray photoelectron spectroscopy spectrum of the oxygen atom 1s orbital obtained by X-ray photoelectron spectroscopy measurement is determined. Condition 1: No peak top exists in the region where the bond energy is between 525 eV and 531 eV, and a peak top exists in the region where the bond energy is between 531 eV and 538 eV. Condition 2: Emitted photoelectron intensity I at the peak top where the binding energy is in the region between 525 eV and 531 eV le The emitted photoelectron intensity I at the peak top where the binding energy is in the region between 531 eV and 538 eV is relative to the bound energy. he The ratio is 1 or greater.

[0015] The X-ray photoelectron spectroscopy spectrum of the oxygen atom's 1s orbital can be obtained by X-ray photoelectron spectroscopy. For example, the PHI VersaProbe, manufactured by ULVAC-PHI, Inc., can be used as an X-ray photoelectron spectroscopy instrument. The procedure for obtaining the X-ray photoelectron spectroscopy spectrum of the oxygen atom's 1s orbital is described below. With the potential relative to Li controlled to be 3.0V or less, the positive electrode (including the positive electrode layer and positive electrode current collector) containing the positive electrode active material is removed from the battery. The positive electrode layer containing the positive electrode active material is used as the upper surface, and the surface of the positive electrode layer is sputtered in the thickness direction by 100 nm or more using a method such as argon sputtering. In the sputtered region, X-ray photoelectron spectroscopy measurements are performed in the bond energy range of 525 eV to 538 eV to obtain the X-ray photoelectron spectroscopy spectrum of the oxygen atom 1s orbital. Simultaneously, X-ray photoelectron spectroscopy measurements are performed in the range including the bond energy range of 280 eV to less than 295 eV, and all spectra are shifted so that the largest peak among the obtained peaks is 284.5 eV. Then, the obtained X-ray photoelectron spectroscopy spectrum is checked to see if it has peaks in the region where the binding energy is between 525 eV and 531 eV, and in the region where the binding energy is between 531 eV and 538 eV. Here, if there is no peak top in the region where the binding energy is between 525 eV and 531 eV, and there is a peak top in the region where the binding energy is between 531 eV and 538 eV, then condition 1 above is satisfied. Furthermore, if peaks exist in both the region where the binding energy is 525 eV or more and less than 531 eV, and the region where the binding energy is 531 eV or more and less than 538 eV, the emitted photoelectron intensity I at the peak top in the region where the binding energy is 525 eV or more and less than 531 eV le and the emitted photoelectron intensity I at the peak top where the binding energy is in the region between 531 eV and 538 eV he Each of these is calculated. Then, the emitted photoelectron intensity I le Relative to the emitted photoelectron intensity I he The ratio (I he / I le The value of ) is calculated, and if this value is 1 or greater, the above condition 2 is considered to be satisfied.

[0016] (Composition formula of positive electrode active material) From the viewpoint of initial discharge capacity and capacity retention rate, the positive electrode active material is preferably a compound represented by the following formula 1. Equation 1: Li a Nab Mn x-p Ni y-q Co z-r M p+q+r O 2ーδ In equation 1 above, a, b, x, y, z, p, q, r, and δ are numbers satisfying 0≦a≦1, 0≦b≦0.05, x+y+z=1, 0≦p+q+r≦0.20, and 0≦δ≦0.3. 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.

[0017] It is preferable that x is a number that satisfies 0 ≤ x ≤ 1, and more preferably that x is a number that satisfies 0.1 ≤ x ≤ 1. It is preferable that y is a number that satisfies 0 ≤ y ≤ 0.5, and more preferably that y is a number that satisfies 0 ≤ y ≤ 0.33. z is preferably a number that satisfies 0 ≤ z ≤ 1, and more preferably 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.

[0018] Here, in equation 1 above, when M is K, it is preferable that 3 ≤ 4x + 2y + 3z - 3p - q - 2r ≤ 3.5 is satisfied. In the above formula 1, if M is at least one selected from the group consisting of Mg and Ca, it is preferable that 3 ≤ 4x + 2y + 3z - 2p - r ≤ 3.5 is satisfied. In the above formula 1, if M is at least one selected from the group consisting of B, Al, Cr, and Ga, it is preferable that 3 ≤ 4x + 2y + 3z - p + q ≤ 3.5 is satisfied. In the above formula 1, if M is at least one selected from the group consisting of Ti, Zr, and Mo, it is preferable that 3 ≤ 4x + 2y + 3z + 2q + r ≤ 3.5 is satisfied. In equation 1 above, when M is Nb, it is preferable that 3 ≤ 4x + 2y + 3z + p + 3q + 2r ≤ 3.5 is satisfied. In the above formula (1), when M is W, it is preferable to satisfy 3 ≤ 4x + 2y + 3z + 2p + 4q + 3r ≤ 3.5. In the above formula (1), when p + q + r = 0, it is preferable to satisfy 0.02 ≤ δ ≤ 0.3.

[0019] From the viewpoints of the initial discharge capacity and the capacity retention rate, in the above formula (1), it is preferable that M is Al. When M is Al in the above formula (1), a kink band is likely to be formed during charge and discharge.

[0020] The positive electrode active material according to the present disclosure is specifically Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O 1.98 、Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O 1.90 、Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O 1.80 、Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.30 O 1.70 、Li 0.70 Na 0.05 Mn 0.50 Ni 0.20 Co 0.30 O 1.90 、Li 0.70 Na 0.00 Mn 0.67 Ni 0.33 O 1.90 、Li 0.70 Na 0.00 Mn 0.67 Ni 0.33 O 1.80 、Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2、Li 0.60 [[ID=0.00 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2, Li 0.70 Na 0.05 Mn 0.50 [[ID=1S]]Ni 0.20 Co 0.20 Al 0.10 O2, Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.10 Al 0.20 O2, Li 0.70 Na 0.00 Mn 0.45 Ni 0.15 Co 0.30 Al 0.10 O2, Li 0.70 Na 0.00 Mn 0.50 Ni 0.20 Co 0.25 Al 0.05 Examples include O2, etc. [[ID=SS]]

[0021] <Method for manufacturing a positive electrode active material> The method for manufacturing a positive electrode active material according to the present disclosure includes a first step of heating a compound represented by the following formula 2 at 400°C or higher to obtain a Na-doped precursor, or a step of obtaining a Na-doped precursor represented by the following formula 3, and a step of ion-exchanging Na contained in the Na-doped precursor with Li (ion-exchange step).

[0022] 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 satisfying 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] It is preferable that x is a number that satisfies 0 ≤ x ≤ 1, and more preferably that x is a number that satisfies 0.1 ≤ x ≤ 1. It is preferable that y is a number that satisfies 0 ≤ y ≤ 0.5, and more preferably that y is a number that satisfies 0 ≤ y ≤ 0.33. z is preferably a number that satisfies 0 ≤ z ≤ 1, and more preferably 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] Equation 3: Na c Mn x-p Ni y-q Co z-r Al p+q+r O2 In equation 3 above, c, x, y, z, p, q, and r are numbers that satisfy 0.5 ≤ c ≤ 0.65, x + y + z = 1, and 0.05 ≤ p + q + r ≤ 0.20.

[0025] It is preferable that x is a number that satisfies 0 ≤ x ≤ 1, and more preferably that x is a number that satisfies 0.1 ≤ x ≤ 1. It is preferable that y is a number that satisfies 0 ≤ y ≤ 0.5, and more preferably that y is a number that satisfies 0 ≤ y ≤ 0.33. z is preferably a number that satisfies 0 ≤ z ≤ 1, and more preferably 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. p and q are 0 ≤ p = q ≤ 0.05

[0026] (Synthesis process of the compound represented by formula 2) In the method for producing a positive electrode active material according to this disclosure, if the first step is a step of heating the compound represented by Formula 2 above at 400°C or higher to obtain a Na-doped precursor, the method may optionally include a step of synthesizing the compound represented by Formula 2 above. The compound represented by formula 2 above is synthesized by known methods.

[0027] Specifically, the compound represented by the above formula 2 is Na 0.70 Mn 0.5 Ni 0.2 Co 0.3 O2, Na 0.80 Mn 0.5 Ni 0.2 Co 0.3 O 2、 Na 0.70 Mn 0.67 Ni 0.33 O2, Na 0.70 Mn 0.40 Ni 0.20 Co 0.30 Cr 0.10 O2, Na 0.70 Mn 0.50 Ni 0.10 Co 0.30 Mg 0.10 Examples include O2.

[0028] (1st step) The first step is to heat the compound represented by formula 2 above at 400°C or higher to obtain a Na-doped precursor, or to obtain a Na-doped precursor represented by formula 3 above. This process makes it easier to obtain the positive electrode active material related to this disclosure.

[0029] -A step of heating the compound represented by the above formula 2 at 400°C or higher to obtain a Na-doped precursor- First, we will explain the process of obtaining a Na-doped precursor by heating the compound represented by the above formula 2 at 400°C or higher (oxygen vacancy introduction process). The oxygen vacancy introduction process is preferably carried out at 100 Pa or less, more preferably at 10 Pa or less, and even more preferably at 1 Pa or less.

[0030] The pressure during the oxygen vacancy introduction process is measured using a pressure gauge. Examples of pressure gauges include Pirani vacuum gauges and ionization vacuum gauges.

[0031] The oxygen vacancy introduction process is preferably carried out at a temperature of 400°C to 600°C, more preferably at 400°C to 500°C, and even more preferably at 400°C to 450°C.

[0032] The temperature during the oxygen vacancy introduction process is measured using a thermometer.

[0033] The oxygen vacancy introduction process may be carried out under air, or under a mixture of air and hydrogen. When the oxygen vacancy introduction process is carried out under a mixture of air and hydrogen, the air content relative to the total volume of the mixture is preferably 80% to 99% by volume, and more preferably 90% to 95% by volume.

[0034] The oxygen vacancy introduction process is preferably carried out for 10 to 20 hours, more preferably for 11 to 15 hours, and even more preferably for 12 to 13 hours.

[0035] -Steps to obtain a Na-doped precursor represented by formula 3 above- Next, we will explain the process of obtaining the Na-doped precursor represented by the above formula 3 (direct Na-doped precursor synthesis process). This step is to obtain the compound represented by formula 3 above. The obtained compound is then used as a Na-doped precursor. The compound represented by formula 3 above is synthesized according to known methods.

[0036] Specifically, the compound represented by the above formula 3 is Na 0.70 Mn 0.5 Ni 0.2 Co 0.3 O2, Na 0.70 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10O2, Na 0.70 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2, Na 0.75 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2, Na 0.70 Mn 0.50 Ni 0.20 Co 0.10 Al 0.20 O2, Na 0.70 Mn 0.45 Ni 0.15 Co 0.30 Al 0.10 O2, Na 0.70 Mn 0.50 Ni 0.20 Co 0.25 Al 0.05 Examples include O2.

[0037] (Ion exchange process) The ion exchange process is a step in which the sodium contained in the sodium-doped precursor is exchanged for lithium through ion exchange. Ion exchange of the Na-doped precursor can be performed using a molten salt bed containing a mixture of lithium nitrate and lithium chloride. For example, it is preferable to mix the Na-doped precursor into the molten salt bed and heat it. The temperature conditions during ion exchange are preferably in the range of above the melting temperature of the molten salt bed and below 320°C.

[0038] <Positive electrode> The positive electrode according to this disclosure comprises a positive electrode layer containing positive electrode active material and a positive electrode current collector, and after being placed in a battery and subjected to discharge and charging, kink bands are formed on 10% or more of the positive electrode active material.

[0039] The positive electrode relating to this disclosure, with the above configuration, is a positive electrode that can produce a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. The reason for this is presumed to be as follows.

[0040] The electrode according to this disclosure, after being placed in a battery and subjected to discharge and charging, forms kinks in 10% or more of the positive electrode active material. Therefore, even if cracks occur in the positive electrode active material due to expansion and contraction caused by charging and discharging, the conductive path is less likely to be interrupted, the decrease in capacity retention rate after repeated charging and discharging is suppressed, and the initial discharge capacity is increased.

[0041] (Positive electrode layer) The positive electrode layer contains a positive electrode active material and may optionally contain conductive additives, solid electrolytes, binders, and other components.

[0042] -Cathode active material- From the viewpoint of initial discharge capacity and capacity retention rate, it is preferable that the positive electrode active material contains the positive electrode active material described above in this disclosure.

[0043] The positive electrode layer relating to this disclosure may contain other positive electrode active materials other than the positive electrode active material relating to this disclosure. The other positive electrode active material preferably includes a lithium composite oxide. The lithium composite oxide may contain at least one selected from the group consisting of F, Cl, N, S, Br, and I. The lithium composite oxide may also have a crystal structure belonging to at least one space group selected from the space groups R-3m, Immmm, and P63-mmc (also called P63mc or P6 / mmc). Furthermore, the lithium composite oxide may have an O2-type structure in which the main arrangement of the transition metal, oxygen, and lithium is located.

[0044] Examples of lithium composite oxides having a crystal structure belonging to R-3m include Li x Me y O α X βExamples of compounds represented by (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, satisfying 0.5≦x≦1.5, 0.5≦y≦1.0, 1≦α<2, and 0<β≦1) include.

[0045] Examples of lithium composite oxides having a crystal structure belonging to Immm include Li x1 M 1 A 1 2(satisfying 1.5 ≤ x1 ≤ 2.3, M 1 It includes at least one selected from the group consisting of Ni, Co, Mn, Cu, and Fe, A 1 It contains at least oxygen, A 1 The proportion of oxygen in it is 85 atomic percent or more. (Examples of complex oxides represented by ) (Li2NiO2), Li 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, M 1B A1 represents at least one element 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 element selected from the group consisting of F, Cl, Br, S, and P. Examples of composite oxides represented by this formula include:

[0046] 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 include composite oxides represented by this formula.

[0047] 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 include composite oxides represented by this formula, and specific examples include Li 0.744 [Li 0.145 Mn 0.625 Co 0.115 Ni 0.115 O2 and the like.

[0048] 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 (0 < x < 1, 0 < b ≦ 1.5) [LTAF electrolyte] is preferred.

[0049] From the viewpoints of the initial discharge capacity and the capacity retention rate, the content of the positive electrode active material is preferably 70% by mass or more, more preferably 75% to 90% by mass, and still more preferably 80% to 85% by mass based on the entire positive electrode layer.

[0050] -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 whisker (e.g., zinc oxide, potassium titanate, etc.), conductive metal oxide (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 two or more kinds may be mixed and used.

[0051] -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.

[0052] 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)(xLi2S·(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 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. Also, at least a portion of 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. A portion of Li may be substituted with at least one selected from the group consisting of Na, K, Mg, Ca, and Zn. A portion of S may be substituted with a halogen. The halogen is at least one of F, Cl, Br, and I.

[0053] Oxide solid electrolytes contain oxygen (O) as the main component of the anionic 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 oxide solid electrolytes include garnet-type solid electrolytes, perovskite-type solid electrolytes, NASICON-type solid electrolytes, Li-PO-based solid electrolytes, and Li-BO-based solid electrolytes. An example of a garnet-type solid electrolyte is Li7La3Zr2O 12 Li 7-x La3(Zr 2-x Nb x )O 12 (0≦x≦2), Li5La3Nb2O 12 Examples include the following. Perovskite-type solid electrolytes include (Li,La)TiO3, (Li,La)NbO3, and (Li,Sr)(Ta,Zr)O3. Nasicone-type solid electrolytes include the following: Li(Al,Ti)(PO4)3 and Li(Al,Ga)(PO4)3. Li-PO-based solid electrolytes include Li3PO4 and LIPON (a compound in which some of the O in Li3PO4 is replaced with N), and Li-BO-based solid electrolytes include Li3BO3 and a compound in which some of the O in Li3BO3 is replaced with C.

[0054] As a halide solid electrolyte, a solid electrolyte containing Li, M, and X (where M represents at least one of Ti, Al, and Y, and X represents F, Cl, or Br) is preferred. Specifically, Li 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 suppressing, for example, the oxidative decomposition of the sulfide solid electrolyte.

[0055] -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.

[0056] -Other Components- Examples of the other components include oxide solid electrolytes, halide solid electrolytes, thickeners, surfactants, dispersants, wetting agents, defoamers, solvents, etc.

[0057] (Positive Electrode Current Collector) Solid-state batteries have a positive electrode current collector. The positive electrode current collector collects current from the positive electrode layer. The positive electrode current collector is positioned on the opposite side of the electrolyte layer (or separator) from the positive electrode layer. Examples of materials for the positive electrode current collector include stainless steel, aluminum, copper, nickel, iron, titanium, and carbon, with aluminum alloy foil or aluminum foil being preferred. Aluminum alloy foil and aluminum foil may be manufactured using powder. The shape of the positive electrode current collector can be, for example, foil-like or mesh-like. The positive electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer on its surface.

[0058] (Kink band) The positive electrode according to this disclosure, after being placed in a battery and subjected to discharge and charging, develops kink bands in 10% or more of the positive electrode active material. Here, a kink band refers to a deformed band formed by the lattice bending by 1° or more, where one side of the kink band and the opposite side are not mirror-symmetric. In particular, in positive electrode active materials for Li-ion batteries having a layered structure, it is formed as a plane with an angle of 30° or more with respect to (001).

[0059] From the viewpoint of initial discharge capacity and capacity retention rate, the positive electrode according to this disclosure preferably has kink bands formed on 10% or more of the positive electrode active material after being placed in a battery and discharged and charged, more preferably on 10% to 50% of the positive electrode active material, and even more preferably on 20% to 40% of the positive electrode active material.

[0060] • Procedure for calculating the kink zone formation rate Here, the formation of kinks in the positive electrode active material after it has been placed in a battery and subjected to discharge and charging is confirmed from the limited-field diffraction pattern of the positive electrode active material. The limited-field diffraction pattern is obtained by observing the positive electrode active material with a transmission electron microscope. For example, the JEM-ARM200F manufactured by JEOL Ltd. can be used as a transmission electron microscope. The procedure for calculating the kink formation rate of the positive electrode active material after it has been placed in a battery and subjected to discharge and charging is described below. First, the battery containing the positive electrode to be measured is discharged and charged. If one discharge and charge cycle is defined as one cycle, the maximum number of cycles will be 20. The discharge and charge conditions will be as follows: Discharge conditions: 0.1C, 2.0V Charging conditions: 0.1C, 4.8V

[0061] Next, the positive electrode is removed from the battery after discharge and charging. More than 100 particles of positive electrode active material contained in the positive electrode layer of the removed electrode are observed using a transmission electron microscope, and a limited-field diffraction pattern is obtained for each particle. A total of 100 limited-field diffraction patterns are observed, and the number of limited-field diffraction patterns in which two or more diffraction patterns of an O2 type structure rotated by 1°C or more, a T#2 type structure rotated by 1°C or more, or an O6 type structure rotated by 1°C or more are observed overlapping is counted. If the number is 10 or more, it is determined that kink bands have formed in 10% or more of the positive electrode active material as a whole.

[0062] <Solid battery> The solid-state battery relating to this disclosure has the positive electrode relating to this disclosure. The solid battery according to this disclosure preferably comprises a positive electrode, a negative electrode, and an electrolyte layer or separator disposed between the positive electrode and the negative electrode. The positive electrode to which the positive electrode according to this disclosure is applied comprises a positive electrode layer and a positive electrode current collector. The negative electrode has a negative electrode layer and may optionally have a negative electrode current collector.

[0063] (Battery structure) Solid-state batteries include so-called all-solid-state batteries (where the electrolyte content is less than 5% by mass of the total electrolyte amount) that use an inorganic solid electrolyte as the electrolyte. Figure 1 is a schematic cross-sectional view showing an example of a solid-state battery. The solid-state battery shown in Figure 1 comprises a negative electrode including a negative electrode current collector 113 and a negative electrode layer A, a solid electrolyte layer B, and a positive electrode including a positive electrode current collector 115 and a positive electrode layer C. 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. The solid electrolyte layer B may have a two-layer structure as shown in Figure 1, a single-layer structure, or a multi-layer structure of two or more layers.

[0064] When a set of a positive electrode layer, a solid electrolyte layer, and a negative electrode layer is considered a power generation unit, a solid-state battery may have only one power generation unit or two or more. If a solid-state battery has two or more power generation units, these units may be connected in series or in parallel.

[0065] Solid-state batteries may be constructed by sealing the laminated ends (sides) of a positive electrode layer / solid electrolyte layer / negative electrode layer with resin. The current collector of the electrode may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer on its surface. The shape of the solid-state battery is not particularly limited and may be, for example, coin-shaped, cylindrical, prismatic, sheet-shaped, button-shaped, flat, or stacked.

[0066] (positive electrode) The solid-state battery relating to this disclosure has the positive electrode relating to this disclosure, and the preferred embodiment is the same.

[0067] (Electrolyte layer and separator) A solid-state battery comprises an electrolyte layer or a separator.

[0068] The electrolyte layer may also be a layer containing a solid electrolyte. In the case of a layer containing a solid electrolyte (solid electrolyte layer), it is preferable that the solid electrolyte layer contains one selected from the group consisting of sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes. The same examples of sulfide solid electrolytes, oxide solid electrolytes, and halide solid electrolytes described above apply.

[0069] The solid electrolyte layer may be a single layer or a multilayer structure of two or more layers.

[0070] The solid electrolyte layer may or may not contain a binder. The binder that may be included in the solid electrolyte layer is the same as that described above.

[0071] As separators, porous sheets (films) made of resins such as polyethylene (PE), polypropylene (PP), polyester, cellulose, and polyamide can be used.

[0072] (Negative electrode layer) A solid-state battery comprises a negative electrode layer. The negative electrode layer contains a negative electrode active material. The negative electrode layer may optionally contain at least one of a negative electrode solid electrolyte, a conductive additive, and a binder. 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. Examples of conductive additives, negative electrode solid electrolytes, and binders used in the negative electrode layer are the same as those exemplified for the conductive additive contained in the positive electrode layer, the solid electrolyte contained in the solid electrolyte layer, and the binder.

[0073] (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 positioned on the opposite side of the electrolyte layer (or separator) from the negative electrode layer. Examples of materials for the negative electrode current collector include stainless steel, aluminum, copper, nickel, iron, titanium, and carbon, with copper being preferred. The shape of the negative electrode current collector can be, for example, foil-like or mesh-like. The negative electrode current collector may have a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer on its surface.

[0074] <Method of manufacturing solid-state batteries> The method for manufacturing a solid battery relating to this disclosure is: A process of preparing the positive electrode, the negative electrode, and the electrolyte layer or separator (preparation process), The process includes a step (lamination step) of stacking a positive electrode, an electrolyte layer or separator, and a negative electrode in that order.

[0075] (preparation process) The preparation process involves preparing the positive electrode, the negative electrode, and the electrolyte layer or separator.

[0076] The method for producing the positive electrode, negative electrode, and electrolyte layer is not particularly limited, but it is preferable to knead the components that may be contained in the positive electrode layer, negative electrode layer, and electrolyte layer to obtain a slurry, apply the slurry to a substrate, and press the dried film obtained by drying. The method for mixing components that may be contained in the cathode layer when obtaining a slurry is not particularly limited, and examples include mixing using a mixing device. Examples of mixing devices include ultrasonic homogenizers, shakers, thin-film spiral mixers, dissolvers, homomixers, kneaders, roll mills, sand mills, attritors, ball mills, vibrator mills, and high-speed impeller mills.

[0077] Methods for pressing dried films include roll pressing and cold isostatic pressing (CIP).

[0078] The pressing pressure is preferably 0.1 t / cm². 2 More preferably 0.5 t / cm 2 More preferably 1 t / cm 2That concludes the explanation. The pressing pressure is preferably 10 t / cm². 2 More preferably 8 t / cm 2 More preferably 6 t / cm 2 The following applies:

[0079] A commercially available porous sheet (film) can be used as the separator.

[0080] (Lamination process) The lamination process involves stacking the positive electrode, the electrolyte layer or separator, and the negative electrode in that order. In the lamination process, it is preferable to obtain a laminate (electrode body) by laminating the positive electrode prepared in the preparation process, the electrolyte layer or separator, and the negative electrode in that order, and pressing as necessary.

[0081] It is preferable to manufacture the solid-state battery according to this disclosure through the above steps. [Examples]

[0082] Examples are described below, but the present invention is not limited to these examples. In the following description, unless otherwise specified, "parts" and "%" all refer to mass.

[0083] <Example 1> [Manufacturing of positive electrode active material] (Synthesis process of the compound represented by formula 2) Mn(NO3)2·6H2O, Ni(NO3)2·6H2O, and Co(NO3)2·6H2O were used as raw materials and dissolved in pure water in a molar ratio of 5:2:3 for Mn, Ni, and Co. A 12% by mass Na2CO3 solution was prepared, and these two solutions were titrated simultaneously into a beaker. During this titration, the titration rate was controlled so that the pH was between 7.0 and less than 7.1. After the titration was completed, the mixed solution was stirred at 50°C and 300 rpm for 24 hours. The resulting reaction product was washed with pure water, and only 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 the obtained intermediate powder, Na2CO3 was added, with a composition ratio of Na 0.75 Mn 0.5 Ni 0.2 Co 0.3 O2 was added and mixed. The mixed powder was pressed with a load of 2 tons using the cold isostatic pressing method to produce pellets. The obtained pellets were pre-calcined in air at 600°C for 6 hours, then calcined at 700°C for 24 hours, cooled to 250°C at 3°C / min, and allowed to cool to form the compound represented by formula 2 (Na 0.75 Mn 0.5 Ni 0.2 Co 0.3 O2) was synthesized.

[0084] (Oxygen vacancy introduction process) By holding the compound represented by formula 2, synthesized using the above procedure, in a vacuum (1 Pa) at 400°C for 12 hours, oxygen vacancies were introduced, yielding a Na-doped precursor.

[0085] (Ion exchange process) A mixed powder was obtained by mixing LiNO3 and LiCl in a mass ratio of 88:12. The mixed powder was weighed so that the ratio of moles of Li to moles of Na-doped precursor was 10 times. The Na-doped precursor and the mixed powder were mixed and ion exchange was performed in air at 280°C for 1 hour. After ion exchange, water was added to dissolve the salt, and further washing with water was performed to obtain a positive electrode active material 1(Li) having an O2 type structure. 0.68 Mn 0.50 Ni 0.20 Co 0.30 O2 was obtained.

[0086] [Manufacturing of solid-state batteries] (preparation process) -Preparing the positive electrode- 5 g of polyvinylidene fluoride (PVDF) as a binder was dissolved in 125 mL of n-methylpyrrolidone solvent. 85 g of the positive electrode active material 1 (powder after ball milling) obtained using the above procedure, and 10 g of carbon black as a conductive additive were added and kneaded until uniformly mixed to prepare a slurry. This slurry was then applied to a 15 μm thick Al positive electrode current collector at a basis weight of 6 mg / cm².2 The electrode was obtained by coating one side and drying it. Then, this electrode was pressed, resulting in a positive electrode layer thickness of 45 μm and a positive electrode layer density of 2.4 g / cm³. 3 Finally, the positive electrode was obtained by cutting this electrode to a diameter of 16 mm.

[0087] -Preparing the negative electrode- A negative electrode was obtained by cutting a piece of lithium foil to a diameter of 19 mm.

[0088] -Preparing the separator- A porous sheet made of PP was prepared as a separator.

[0089] (Lamination process) A laminate was obtained by stacking a positive electrode, a separator, and a negative electrode in this order. The positive electrode was stacked so that the positive electrode layer faced the separator. The laminate and a non-aqueous electrolyte (a mixture of EC (ethylene carbonate) and DMC (dimethyl carbonate) in a volume ratio of 3:7, with lithium hexafluoride phosphate (LiPF6) dissolved as a supporting salt at a concentration of 1 mol / L) were placed in a coin cell to fabricate a CR2032 type coin cell battery.

[0090] <Example 2> [Manufacturing of positive electrode active material] In the (oxygen vacancy introduction step), the compound represented by formula 2 was held at 400°C for 12 hours in an atmosphere of 95% air and 5% hydrogen to introduce oxygen vacancies and obtain a Na-doped precursor. The positive electrode active material was obtained using the same procedure as in Example 1. 0.67 Mn 0.50 Ni 0.20 Co 0.30 Let's assume O2.

[0091] [Manufacturing of solid-state batteries] In the (Preparation Process) - Preparation of the positive electrode - a coin cell battery was manufactured using the same procedure as in Example 1, except that positive electrode active material 1 was changed to positive electrode active material 2.

[0092] <Example 3> [Manufacturing of positive electrode active material] (Direct Na-doped precursor synthesis process) Mn(NO3)2·6H2O, Ni(NO3)2·6H2O, Co(NO3)2·6H2O, and Al(NO3)3·9H2O were used as raw materials and dissolved in pure water in a molar ratio of Mn, Ni, Co, and Al of 5:2:2:1. A 12% by mass Na2CO3 solution was prepared, and these two solutions were titrated simultaneously into a beaker. During this titration, the titration rate was controlled so that the pH was between 7.0 and less than 7.1. After the titration was complete, the mixed solution was stirred at 50°C and 300 rpm for 24 hours. The resulting reaction product was washed with pure water, and only 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 the obtained intermediate powder, Na2CO3 was added, with a composition ratio of Na 0.75 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2 was added and mixed. The mixed powder was pressed with a load of 2 tons using the cold isostatic pressing method to produce pellets. The obtained pellets were pre-calcined in air at 600°C for 6 hours, then calcined at 700°C for 24 hours, cooled to 250°C at 3°C / min, and allowed to cool to form the compound represented by formula 3 (Na 0.71 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2) was synthesized and used as a Na-doped precursor.

[0093] (Oxygen vacancy introduction process) By holding the compound represented by formula 3, synthesized using the above procedure, in a vacuum (1 Pa) at 400°C for 12 hours, oxygen vacancies were introduced, yielding a Na-doped precursor.

[0094] (Ion exchange process) A mixed powder was obtained by mixing LiNO3 and LiCl in a mass ratio of 88:12. The mixed powder was weighed so that the ratio of moles of Li to moles of Na-doped precursor was 10 times. The Na-doped precursor and the mixed powder were mixed and ion exchange was performed in air at 280°C for 1 hour. After ion exchange, water was added to dissolve the salt, and further washing with water was performed to obtain a positive electrode active material 3(Li) having an O2-type structure. 0.67 Mn 0.50 Ni 0.20 Co 0.20 Al 0.10 O2 was obtained.

[0095] [Manufacturing of solid-state batteries] In the (Preparation Process) - Preparation of the positive electrode - a coin cell battery was manufactured using the same procedure as in Example 1, except that positive electrode active material 1 was changed to positive electrode active material 3.

[0096] <Example 4> [Manufacturing of positive electrode active material] Using the same procedure as in Example 1, the positive electrode active material 1 (Li 0.68 Mn 0.50 Ni 0.20 Co 0.30 O2 was obtained.

[0097] [Manufacturing of solid-state batteries] Except for the preparation of the positive electrode, the amount of positive electrode active material 1 added was set to 70g and the amount of carbon black added to 25g in the preparation of the positive electrode, but a coin cell battery was prepared using the same procedure as in Example 1.

[0098] <Comparative Example 1> [Manufacturing of positive electrode active material] The positive electrode active material was obtained using the same procedure as in Example 1, except that the oxygen vacancy introduction step was omitted. This positive electrode active material was used to obtain positive electrode active material C1(Li 0.68 Mn 0.50 Ni 0.20 Co 0.30 Let's assume O2.

[0099] [Manufacturing of solid-state batteries] In the (Preparation Process) - Preparation of the positive electrode - a coin cell battery was manufactured using the same procedure as in Example 1, except that positive electrode active material 1 was changed to positive electrode active material C1.

[0100] <Rating> (X-ray photoelectron spectroscopy spectrum of the oxygen atom's 1s orbital) X-ray photoelectron spectroscopy spectra of the oxygen atom 1s orbital of the positive electrode active material obtained in each example were obtained according to the procedure described above. Then, it was checked whether the obtained X-ray photoelectron spectroscopy spectra of the oxygen atom 1s orbital had peaks in the region where the binding energy is between 525 eV and less than 531 eV, and in the region where the binding energy is between 531 eV and 538 eV. If peaks were present, the emitted photoelectron intensity at the peak top of the peak was determined. The results are shown in Table 1. If there is no peak in the region where the binding energy is between 525 eV and less than 531 eV, or in the region where the binding energy is between 531 eV and 538 eV, it is indicated as "None," and if there is a peak, it is indicated as "Present." Furthermore, if a peak is present, the emitted photoelectron intensity at the peak top of that peak is recorded. Note that the emitted photoelectron intensity at the peak top in the region where the binding energy is between 525 eV and 531 eV is indicated as "Intensity I" in Table 1. le The emitted photoelectron intensity at the peak top, where the binding energy is in the region between 531 eV and 538 eV, is shown as "Intensity I" in Table 1. he "

[0101] (Kink formation rate) The batteries obtained in each example were placed in a battery using the same procedure as described in "Procedure for Calculating the Proportion of Kink Formation," and after discharging and charging, the proportion of positive electrode active material in which kinks were formed relative to the total positive electrode active material was calculated. The results are shown in Table 1.

[0102] (Initial discharge capacity) A galvanostat was used to conduct charge-discharge tests under the conditions of a current of 0.1C, a charge termination voltage of 4.8V, and a discharge termination voltage of 2.0V. Starting with charging, after the first charge cycle was completed, the amount of current required to discharge down to 2.0V was calculated, and the initial discharge capacity was calculated by dividing this amount by the weight of the active material used in the measurement.

[0103] (Capacity retention rate after 20 cycles) A charge-discharge test was conducted under the same conditions as described above, and the discharge capacity after the first discharge and the discharge capacity after the 20th discharge were calculated. The capacity retention rate after 20 cycles was obtained by dividing the discharge capacity after the 20th discharge by the discharge capacity after the first discharge.

[0104] [Table 1]

[0105] In Table 1, "Positive electrode active material content (mass%)" refers to the content of the positive electrode active material relative to the entire positive electrode layer.

[0106] From the above results, it can be seen that the positive electrode active material and positive electrode of this embodiment produce a battery with a high initial discharge capacity and a high capacity retention rate after repeated charging and discharging. [Explanation of Symbols]

[0107] 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 additive 109,111 binders 113 Negative electrode current collector 115 Positive electrode current collector

Claims

1. The X-ray photoelectron spectroscopy spectrum of the oxygen atom 1s orbital obtained by X-ray photoelectron spectroscopy satisfies either condition 1 or condition 2 below. A positive electrode active material that is a compound represented by the following formula 1 and has an O2-type structure. Condition 1: No peak top exists in the region where the bond energy is between 525 eV and 531 eV, and a peak top exists in the region where the bond energy is between 531 eV and 538 eV. Condition 2: Emitted photoelectron intensity I at the peak top where the binding energy is in the region between 525 eV and 531 eV ｌｅ The emitted photoelectron intensity I at the peak top where the binding energy is in the region between 531 eV and 538 eV. ｈｅ The ratio is 1 or greater. Formula 1: Li ａ Na ｂ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ーδ (In equation 1 above, a, b, x, y, z, p, q, r, and δ are numbers that satisfy 0 ≤ a ≤ 1, 0 ≤ b ≤ 0.05, x + y + z = 1, 0 ≤ p + q + r ≤ 0.20, and 0 ≤ δ ≤ 0.3.) (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.)

2. The positive electrode active material according to claim 1, wherein M is Al in formula 1.

3. A method for producing a positive electrode active material in which, after being placed in a battery and subjected to discharge and charging, the proportion of positive electrode active material in which a kink band is formed is 10% or more of the total positive electrode active material, The first step is to obtain a Na-doped precursor by heating a compound represented by the following formula 2 under vacuum, at a temperature of 400°C or higher, for 10 to 20 hours, or by heating a compound represented by the following formula 3 under vacuum, at a temperature of 400°C or higher, for 10 to 20 hours. A method for producing a positive electrode active material, comprising the step of ion-exchanging Na contained in the Na-doped precursor for Li. Formula 2: Na ｃ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ M ｐ＋ｑ＋ｒ O ２ (In equation 2 above, c, x, y, z, p, q, and r are numbers that satisfy 0.5 ≤ c ≤ 0.80, 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. Formula 3: Na ｃ Mn ｘ－ｐ Ni ｙ－ｑ Co ｚ－ｒ Al ｐ＋ｑ＋ｒ O ２ (In equation 3 above, c, x, y, z, p, q, and r are numbers that satisfy 0.5 ≤ c ≤ 0.75, x + y + z = 1, and 0.05 ≤ p + q + r ≤ 0.20.)

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