Electrode active material, electrode battery, and battery

Abstract

Disclosed is a technique whereby the cycle characteristics of a battery can be improved when the battery is configured using an electrode active material having an O2-type structure. The electrode active material according to the present disclosure is characterized by containing an O2-type Li-containing oxide and lithium hydroxide, and the O1s spectrum of the electrode active material obtained by XPS satisfies 0.20 < = S1 / (S1 + S2) < = 0.73 (S1: the area of a peak derived from lithium hydroxide at 531.4 eV, S2: the area of a peak derived from the O2-type Li-containing oxide at 529.4 eV).

Description

Technical Field

[0001] The present application discloses an electrode active material, an electrode composite material and a battery. Background Art

[0002] As a battery active material, a battery active material having an O2 type structure is known. As disclosed in Patent Document 1, an electrode active material having an O2 type structure is obtained by exchanging at least a portion of Na in an oxide containing Na having a P2 type structure with Li.

[0003] Prior art literature

[0004] Patent Literature

[0005] Patent Document 1: Japanese Patent Application Publication No. 2010-092824 Summary of the invention

[0006] Problems to be solved by the invention

[0007] Regarding batteries using an electrode active material having an O2-type structure, there is room for improvement in cycle characteristics.

[0008] Means for solving problems

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

[0010] <Option 1>

[0011] An electrode active material comprises an O2-type Li-containing oxide and lithium hydroxide, wherein the O1s spectrum of the electrode active material obtained by XPS satisfies the following relationship (1):

[0012] 0.20≤S1 / (S1+S2)≤0.73 · · · (1)

[0013] S1: Area of ​​the peak derived from lithium hydroxide at 531.4 eV

[0014] S2: The area of ​​the peak derived from the O2-type Li-containing oxide at 529.4 eV.

[0015] <Option 2>

[0016] The electrode active material according to Scheme 1, wherein the O1s spectrum satisfies the following relationship (1A):

[0017] 0.39≤S1 / (S1+S2)≤0.68···(1A).

[0018] <Option 3>

[0019] An electrode composite material comprising the electrode active material of scheme 1 or 2.

[0020] <Option 4>

[0021] A battery comprising a positive electrode active material layer, an electrolyte layer and a negative electrode active material layer, wherein the positive electrode active material layer comprises the electrode active material of embodiment 1 or 2.

[0022] Effects of the Invention

[0023] When a battery is constructed using the electrode active material of the present disclosure, the cycle characteristics of the battery are likely to be improved. BRIEF DESCRIPTION OF THE DRAWINGS

[0024] Figure 1 An example of the cross-sectional structure of an electrode active material is schematically shown.

[0025] Figure 2 An example of a flow of a method for producing an electrode active material is shown.

[0026] Figure 3 An example of a battery configuration is schematically shown.

[0027] Figure 4 The XPS-O1s spectra of the electrode active materials in Examples 2, 4, Comparative Examples 1 and 3 are shown.

[0028] Figure 5 It shows the relationship between S1 / (S1+S2) and capacity maintenance rate.

[0029] Description of Reference Numerals

[0030] 1Electrode active material

[0031] 1a O2-type oxide containing Li

[0032] 1b Lithium hydroxide

[0033] 100 Batteries

[0034] 10 Positive electrode active material layer

[0035] 20 Electrolyte layer

[0036] 30 Negative electrode active material layer

[0037] 40 positive electrode collector

[0038] 50 Negative electrode collector DETAILED DESCRIPTION

[0039] Hereinafter, one embodiment of the electrode active material, the electrode composite material, and the battery disclosed herein will be described. However, the electrode active material, the electrode composite material, and the battery disclosed herein are not limited to the embodiment described below.

[0040] 1. Electrode active material

[0041] like Figure 1 As described in the above, an electrode active material 1 according to one embodiment includes an O2-type Li-containing oxide 1a and lithium hydroxide 1b. The O1s spectrum of the electrode active material 1 obtained by XPS satisfies the following relationship (1):

[0042] 0.20≤S1 / (S1+S2)≤0.73 · · · (1)

[0043] S1: Area of ​​the peak derived from lithium hydroxide at 531.4 eV

[0044] S2: The area of ​​the peak derived from the O2-type Li-containing oxide at 529.4 eV.

[0045] 1.1O2-type Li-containing oxides

[0046] 1.1.1 Crystal structure

[0047] The O2-type Li-containing oxide 1a has an O2-type structure as a crystal structure. The O2-type Li-containing oxide 1a may have a crystal structure other than the O2-type structure while having the O2-type structure. As a crystal structure other than the O2-type structure, for example, a T#2-type structure (belonging to the space group Cmca) formed when Li is deinserted from the O2-type structure, an O6-type structure (belonging to the space group R-3m, with a c-axis length of 2.5 nm or more and 3.5 nm or less, typically 2.9 nm or more and 3.0 nm or less, which is different from the O3-type structure also belonging to the space group R-3m), etc. can be cited. The O2-type Li-containing oxide 1a may have an O2-type structure as a main phase, or may have a crystal structure other than the O2-type structure (for example, an O6-type structure) as a main phase. For the O2-type Li-containing oxide 1a, the crystal structure that becomes the main phase may change depending on its charge and discharge state.

[0048] 1.1.2 Chemical composition

[0049] The O2-type Li-containing oxide 1a may contain, for example, at least one element of Mn, Ni, and Co, Li, and O as constituent elements. The O2-type Li-containing oxide 1a may contain, in particular, at least Li, Mn, one or both of Ni and Co, and O as constituent elements. In particular, higher performance is easily obtained when at least Li, Mn, Ni, Co, and O are contained as constituent elements. The O2-type Li-containing oxide 1a may have a Li a Na b Mn x-p Ni y-q Co z-r M p+q+r O2 (wherein 0<a≤1.00, 0≤b≤0.20, x+y+z=1, and 0≤p+q+r<0.17, and the element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W). In the case where the O2-type Li-containing oxide 1a has such a chemical composition, it is easy to maintain the O2-type structure. In the above chemical composition, a is greater than 0, and may be greater than 0.10, greater than 0.20, greater than 0.30, greater than 0.40, greater than 0.50 or greater than 0.60, and is less than 1.00, and may be less than 0.90, less than 0.80 or less than 0.70. In the above chemical composition, b is greater than or equal to 0, and may be greater than or equal to 0.01, greater than or equal to 0.02, or greater than or equal to 0.03, and is less than or equal to 0.20, and may be less than or equal to 0.15, or less than or equal to 0.10. In addition, x is greater than or equal to 0, and may be greater than or equal to 0.10, greater than or equal to 0.20, greater than or equal to 0.30, greater than or equal to 0.40, or greater than or equal to 0.50, and is less than or equal to 1.00, and may be less than or equal to 0.90, less than or equal to 0.80, less than or equal to 0.70, less than or equal to 0.60, or less than or equal to 0.50. In addition, y is greater than or equal to 0, and may be greater than or equal to 0.10, or greater than or equal to 0.20, and is less than or equal to 1.00, and may be less than or equal to 0.90, less than or equal to 0.80, less than or equal to 0.70, less than or equal to 0.60, less than or equal to 0.50, less than or equal to 0.40, less than or equal to 0.30, or less than or equal to 0.20. In addition, z is greater than 0, and may be greater than 0.10, greater than 0.20, or greater than 0.30, and is less than 1.00, and may be less than 0.90, less than 0.80, less than 0.70, less than 0.60, less than 0.50, less than 0.40, or less than 0.30. Element M contributes little to charge and discharge. In this regard, in the above-mentioned chemical composition, it is easy to ensure a high charge and discharge capacity by having p+q+r be less than 0.17. p+q+r may be less than 0.16, less than 0.15, less than 0.14, less than 0.13, less than 0.12, less than 0.11, or less than 0.10. On the other hand, by including element M, the O2 type structure is easily stabilized. In the above chemical composition, p+q+r is greater than 0, and may be greater than 0.01, greater than 0.02, greater than 0.03, greater than 0.04, greater than 0.05, greater than 0.06, greater than 0.07, greater than 0.08, greater than 0.09, or greater than 0.10. The composition of O is approximately 2, and is not limited to being precisely 2.0, but is indefinite.

[0050] 1.2 Lithium hydroxide

[0051] The electrode active material 1 includes an O2-type Li-containing oxide 1a and lithium hydroxide 1b. Figure 1 As described above, the electrode active material 1 may include an O2-type Li-containing oxide 1a and lithium hydroxide 1b covering at least a portion of the surface of the O2-type Li-containing oxide 1a. The amount of lithium hydroxide 1b contained in the electrode active material 1 may satisfy the relationship (1) described below.

[0052] 1.3 O1s spectrum of electrode active material obtained by XPS

[0053] The amount of lithium hydroxide 1b in the electrode active material 1 can be measured by X-ray photoelectron spectroscopy (XPS). XPS is a method of analyzing the constituent elements and their electronic states on the sample surface by irradiating the sample surface with X-rays and measuring the energy of the released photoelectrons. The spectrum obtained by XPS shows a peak area proportional to the pattern and amount of the substance, so qualitative and quantitative analysis of the substance can be performed. When the O1s spectrum of the electrode active material 1 obtained by XPS satisfies the above relationship (1), it can be said that lithium hydroxide 1b is appropriately precipitated on the surface of the O2-type Li-containing oxide 1a. When lithium hydroxide 1b is appropriately precipitated on the surface of the O2-type Li-containing oxide 1a, when the electrode active material 1 is used to construct a battery and the battery is charged to a high potential region, the Li conduction path between the active material and the electrolyte is ensured, and the lithium hydroxide 1b prevents the O2-type Li-containing oxide 1a from contacting the electrolyte, so that the degradation and decomposition of the electrolyte during charging can be easily suppressed. That is, by constituting a battery using the electrode active material 1, a battery having excellent cycle characteristics can be obtained.

[0054] In particular, when the O1s spectrum of the electrode active material 1 obtained by XPS satisfies the following relationship (1A), the cycle characteristics improvement effect becomes more significant.

[0055] 0.39≤S1 / (S1+S2)≤0.68···(1A)

[0056] It is to be noted that in the above-mentioned O1s energy spectrum, the peak from lithium hydroxide at 531.4 eV and the peak from the O2-type Li-containing oxide at 529.4 eV can be overlapped. Therefore, when determining the areas S1 and S2 of the above-mentioned peaks, the polarity adopts waveform separation by curve fitting (typically, fitting based on nonlinear least squares method). Thus, the peak at the position of 531.4 eV with a binding energy of 529.4 eV can be separated from the peak at the position, and the area of ​​each peak can be determined. As for waveform separation, for example, it can be implemented by using the software "MultiPak" made by Albuck PHI. It is to be noted that the "peak at the position of 531.4 eV" and the "peak at the position of 529.4 eV" allow for deviations (± 0.1 eV) in the position of the peak top that may occur due to measurement conditions, etc.

[0057] 1.4 Others

[0058] As for the electrode active material 1, as described later, after replacing Na of the oxide containing Na with a P2 type structure with Li to obtain an O2 type oxide containing Li 1a, lithium hydroxide 1b is precipitated, thereby obtaining it. Among them, the P2 type structure is a hexagonal system, the diffusion coefficient of Na ions is large, and crystals are easily grown in a specific direction. In particular, as a transition metal element constituting the P2 type structure, when at least one of Mn, Ni and Co is included, it is easy to grow crystals into a plate shape in a specific direction. Therefore, for the oxide containing Na with a P2 type structure, it usually becomes a plate-like particle with a large aspect ratio in which the growth direction of the crystal is biased toward a specific direction. The electrode active material 1 can be obtained based on such a plate-like oxide particle containing Na, or it can be obtained based on a spherical oxide particle containing Na. That is, the shape of the electrode active material 1 can be a plate-like particle or a spherical particle. In the case where the electrode active material 1 is a spherical particle, the reaction resistance is reduced due to the reduction of the crystallite size, and the diffusion resistance inside the particle is easily reduced. Furthermore, when applied to batteries, it is believed that: due to spheroidization, the curvature is reduced and the lithium ion conduction resistance is reduced. As a result, for example, the rate characteristics are improved and the reversible capacity is easily increased. It should be noted that in the present application, the so-called "spherical particles" refer to particles with a circularity of 0.80 or more. The circularity of the particles may be greater than 0.81, greater than 0.82, greater than 0.83, greater than 0.84, greater than 0.85, greater than 0.86, greater than 0.87, greater than 0.88, greater than 0.89 or greater than 0.90. The circularity of the particles is expressed by 4πS / L 2Definition. Wherein, S is the orthographic projection area of ​​the particle, and L is the perimeter of the orthographic projection image of the particle. The circularity of the particle can be obtained by observing the appearance of the particle using a scanning electron microscope (SEM), a transmission electron microscope (TEM), or an optical microscope.

[0059] As for the electrode active material 1, for example, it can be a solid particle, a hollow particle, or a particle with a void. The size of the particles of the electrode active material 1 is not particularly limited, and it is believed that the smaller the size, the more advantageous it is. For example, the average particle size (D50) of the particles of the electrode active material 1 can be greater than 0.1 μm and less than 10 μm, greater than 1.0 μm and less than 8.0 μm, or greater than 2.0 μm and less than 6.0 μm. It should be noted that the average particle size (D50) is the particle size (D50, median diameter) at the cumulative value 50% in the volume-based particle size distribution measured by the laser diffraction scattering method.

[0060] 2. Method for producing electrode active material

[0061] The electrode active material 1 can be produced, for example, by the following method. Figure 2 As described in, a method for producing an electrode active material 1 according to one embodiment may include:

[0062] S1: Obtaining a transition metal oxide containing Na having a P2-type structure;

[0063] S2: replacing at least a portion of Na in the above-mentioned Na-containing oxide with Li by ion exchange to obtain a Li-containing oxide having an O2 type structure;

[0064] S3: further doping the Li-containing oxide with Li in a process different from the ion exchange process; and

[0065] S4: Lithium hydroxide is precipitated on the surface of the Li-doped Li-containing oxide.

[0066] 2.1S1

[0067] In S1, the transition metal oxide containing Na and having a P2 type structure can be produced, for example, by the following method:

[0068] S11: obtaining a precursor (for example, a precursor containing at least one element of Mn, Ni and Co);

[0069] S12: coating the surface of the precursor with a Na source to obtain a composite; and

[0070] S13: sintering the composite body.

[0071] Wherein, the above S13 may include:

[0072] S13-1: pre-sintering the composite at a temperature of 300° C. or higher and less than 700° C. for a period of 2 hours or higher and 10 hours or lower;

[0073] S13-2: Following the pre-sintering, the composite is subjected to main sintering at a temperature of 700° C. to 1100° C. for a period of 30 minutes to 48 hours; and

[0074] S13-3: Following the main calcination, the composite body is rapidly cooled from a temperature T1 of 200°C or higher to a temperature T2 of 100°C or lower.

[0075] 2.1.1 Preparation of precursor

[0076] The precursor may contain at least Mn, and one or both of Ni and Co, and may contain at least Mn, Ni and Co. The precursor may be a salt containing at least one element of Mn, Ni and Co. For example, the precursor may be at least one of carbonate, sulfate, nitrate and acetate. Alternatively, the precursor may be a compound other than a salt. For example, the precursor may be a hydroxide. The precursor may be a hydrate. The precursor may be a combination of multiple compounds. The precursor may be in various shapes. For example, the precursor may be in the form of particles, or may be spherical particles as described later. There is no particular limitation on the particle size of the particles formed by the precursor.

[0077] In S11, an ion source that can form a precipitate with transition metal ions in an aqueous solution and a transition metal compound containing at least one element of Mn, Ni and Co are used to obtain a precipitate as the above-mentioned precursor by a coprecipitation method. Thus, spherical particles as a precursor are easily obtained. As for the "ion source that can form a precipitate with transition metal ions in an aqueous solution", for example, it can be at least one selected from sodium salts such as sodium carbonate and sodium nitrate, sodium hydroxide and sodium oxide. The transition metal compound can be the above-mentioned salt, hydroxide, etc. containing at least one element of Mn, Ni and Co. Specifically, in S11, after the ion source and the transition metal compound are made into solutions respectively, each solution is added dropwise and mixed, thereby obtaining a precipitate as a precursor. At this time, as a solvent, for example, water is used. At this time, as a base, various sodium compounds can be used, and in addition, an ammonia solution can be added to adjust the alkalinity. In the case of the coprecipitation method, for example, an aqueous solution of a transition metal compound and an aqueous solution of sodium carbonate are prepared, and each aqueous solution is added dropwise and mixed, thereby obtaining a precipitate as a precursor. Alternatively, the precursor may be obtained by a sol-gel method. In particular, spherical particles as a precursor can be easily obtained by a coprecipitation method.

[0078] In S11, the precursor may contain element M. Element M is at least one selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W. As for these elements M, for example, they have the function of stabilizing the P2 type structure and the O2 type structure. There is no particular limitation on the method for obtaining the precursor containing element M. In the case where the precursor is obtained by coprecipitation in S11, for example, an aqueous solution of a transition metal compound containing at least one of Mn, Ni and Co, an aqueous solution of sodium carbonate, and an aqueous solution of a compound of element M are prepared, and each aqueous solution is added dropwise and mixed, thereby obtaining a precursor containing at least one of Mn, Ni and Co and also containing element M. Alternatively, in the manufacturing method disclosed in the present invention, element M is not added in S11, and element M may be doped during the solid Na doping sintering in S2 and S3 described later.

[0079] 2.1.2 Fabrication of the complex

[0080] In S12, the surface of the precursor obtained by S11 is coated with a Na source to obtain a composite. The Na source can be a salt containing Na such as a carbonate, a nitrate, or a compound other than a salt such as sodium oxide, sodium hydroxide, etc. In S12, the amount of the Na source coated on the surface of the precursor can be determined by taking into account the disappearance of Na during subsequent calcination. In S12, there is no particular limitation on the coverage rate of the Na source on the surface of the precursor. In S12, there is no particular limitation on the method of coating the surface of the above-mentioned precursor with a Na source. For example, the precursor and the Na source can be mixed by a mortar or a mixing device, or a rolling flow coating method, a spray drying method, etc. can be used to dry the solution containing the Na source after contacting the precursor.

[0081] In S12, the precursor may be coated with an M source together with a Na source. For example, in S12, the precursor obtained by S11, the Na source, and the M source containing at least one element M selected from B, Mg, Al, K, Ca, Ti, V, Cr, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo, and W may be mixed to obtain a composite. The M source may be, for example, a salt containing the element M such as a carbonate or a sulfate, or a compound other than a salt such as an oxide or a hydroxide. The amount of the M source relative to the precursor may be determined based on the chemical composition of the oxide containing Na after sintering.

[0082] 2.1.3 Firing of the composite

[0083] In S13, the composite obtained by S12 is calcined to obtain an oxide containing Na having a P2 type structure. S13 may include the above-mentioned S13-1, S13-2 and S13-3. By adjusting the conditions in S13-1, S13-2 and S13-3, the crystallinity and shape (plate-like particles or spherical particles) of the P2 type oxide containing Na obtained by S13 can be adjusted.

[0084] In S13-1, the above-mentioned composite is pre-fired at a temperature of 300°C to less than 700°C for a time of 2 hours to 10 hours. In S13-1, the pre-fired can be carried out after the above-mentioned composite is arbitrarily formed. The pre-fired is carried out at a temperature lower than that of the main calcination. If the pre-fired in S13-1 is insufficient, the formation of the P2 phase in the finally obtained Na-containing oxide may become insufficient. In S13-1, by setting the pre-fired temperature to 300°C to less than 700°C and the pre-fired time to 2 hours to 10 hours, the composite can be sufficiently pre-fired, the thermal uniformity is improved, and the Na-containing oxide obtained through S13-2 and S13-3 described later can easily become a suitable oxide. The pre-firing temperature may be 400°C to less than 700°C, 450°C to less than 700°C, 500°C to less than 700°C, 550°C to less than 700°C, or 550°C to less than 650°C. In addition, the pre-firing time may be 2 hours to 8 hours, 3 hours to 8 hours, 4 hours to 8 hours, 5 hours to 8 hours, or 5 hours to 7 hours. The pre-firing atmosphere is not particularly limited, and may be, for example, an oxygen-containing atmosphere.

[0085] In S13-2, following the above-mentioned pre-calcination, the above-mentioned composite is subjected to main calcination at a temperature of 700°C to 1100°C for 30 minutes to 48 hours. In S13-2, the main calcination temperature of the composite can be 800°C to 1000°C. If the main calcination temperature is too low, the P2 phase is not generated. If the main calcination temperature is too high, the O3 phase is easily generated instead of the P2 phase. There is no particular limitation on the heating conditions from the pre-calcination temperature to the main calcination temperature. In S13-2, the shape of the oxide containing Na can be controlled by the main calcination time. If the main calcination time is too short, the generation of the P2 phase becomes insufficient. On the other hand, if the main calcination time is too long, the P2 phase grows excessively, and the particles are easily coarsened into a plate shape.

[0086] In S13-3, following the above-mentioned main calcination, the above-mentioned composite is rapidly cooled (cooled at a temperature reduction rate of 20°C / min or more) from a temperature T1 of more than 200°C to a temperature T2 of less than 100°C. The above-mentioned preliminary calcination and main calcination are performed, for example, in a heating furnace. In step S13-3, for example, after the main calcination of the composite is performed in a heating furnace, it is cooled to an arbitrary temperature T1 of more than 200°C in the heating furnace. After reaching the temperature T1, the calcined product is taken out of the heating furnace and rapidly cooled outside the furnace to an arbitrary temperature T2 of less than 100°C. Temperature T1 is an arbitrary temperature of more than 200°C, and can be an arbitrary temperature of more than 250°C. Temperature T2 is an arbitrary temperature of less than 100°C, and can be an arbitrary temperature of less than 50°C, and can be the cooling end temperature. In the specified temperature range from temperature T1 to temperature T2, moisture easily penetrates into the interlayers of the P2 type structure due to atomic vibration, molecular motion, etc. When cooling the composite body (Na-containing oxide having a P2-type structure) after the main firing, by making the time in the temperature region where moisture easily penetrates short (i.e., performing high-speed cooling), it is considered that the amount of moisture penetrating into the interlayers of the P2-type structure is reduced. In this regard, in step S13-3, when cooling the composite body after the main firing, from an arbitrary temperature T1 above 200°C to an arbitrary temperature T2 below 100°C, for example, natural cooling is performed in a dry atmosphere outside the furnace, whereby the cooling rate from temperature T1 to temperature T2 becomes high (e.g., 20°C / min or more), moisture becomes difficult to penetrate into the interlayers of the P2-type structure, and the collapse of the P2-type structure can be suppressed. As a result, Na can be effectively ion-exchanged for Li in S2.

[0087] By S13, it is possible to manufacture an oxide containing Na having a P2 type structure and a predetermined chemical composition. The oxide containing Na contains at least one transition metal element among Mn, Ni and Co, Na, and O as constituent elements. In particular, in the case of containing at least Na; at least one of Mn, Ni and Co; and O as constituent elements, the performance of the positive electrode active material is likely to be further improved. The oxide containing Na may have a composition consisting of Na c Mn x-p Ni y-q Co z-r M p+q+rThe chemical composition represented by O2. Wherein, 0<c<1.00, x+y+z=1 and 0≤p+q+r<0.17. In addition, M is at least one element selected from B, Mg, Al, K, Ca, Ti, V, Cr, Fe, Cu, Zn, Ga, Ge, Sr, Y, Zr, Nb, Mo and W. In the case where the oxide containing Na has such a chemical composition, it is easy to further maintain the P2 type structure. In the above chemical composition, c is greater than 0, and can be greater than 0.10, greater than 0.20, greater than 0.30, greater than 0.40, greater than 0.50 or greater than 0.60, and is less than 1.00, and can be less than 0.90, less than 0.80 or less than 0.70. x is 0 or more, and may be 0.10 or more, 0.20 or more, 0.30 or more, 0.40 or more, or 0.50 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, or 0.50 or less. In addition, y is 0 or more, and may be 0.10 or more, or 0.20 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, 0.30 or less, or 0.20 or less. In addition, z is 0 or more, and may be 0.10 or more, 0.20 or more, or 0.30 or more, and is 1.00 or less, and may be 0.90 or less, 0.80 or less, 0.70 or less, 0.60 or less, 0.50 or less, 0.40 or less, or 0.30 or less. Element M has a small contribution to charge and discharge. In this respect, in the above-mentioned chemical composition, by p+q+r being less than 0.17, it is easy to ensure a high charge and discharge capacity. p+q+r may be less than 0.16, less than 0.15, less than 0.14, less than 0.13, less than 0.12, less than 0.11 or less than 0.10. On the other hand, by including the element M, the P2 type structure and the O2 type structure are easily stabilized. In the above-mentioned chemical composition, p+q+r is greater than 0, and may be greater than 0.01, greater than 0.02, greater than 0.03, greater than 0.04, greater than 0.05, greater than 0.06, greater than 0.07, greater than 0.08, greater than 0.09 or greater than 0.10. The composition of O is approximately 2, is not limited to being exactly 2.0, and is indefinite.

[0088] 2.2S2

[0089] In S2, at least a portion of the Na of the oxide containing Na obtained by S1 is ion-exchanged with Li, thereby obtaining an oxide containing Li having an O2 type structure. In ion exchange, for example, there is a method using an aqueous solution containing lithium halide, and a method using a mixture of lithium halide and other lithium salts (such as a molten salt). From the viewpoint that the P2 type structure is easily destroyed due to the intrusion of water and the viewpoint of crystallinity, the method using a molten salt is preferred among the above two methods. That is, the above-mentioned oxide containing Na with a P2 type structure is mixed with the molten salt and heated to a temperature above the melting point of the molten salt, thereby at least a portion of the Na of the oxide containing Na can be replaced with Li by ion exchange. The lithium halide constituting the molten salt is preferably at least one of lithium chloride, lithium bromide and lithium iodide. The other lithium salts constituting the molten salt are preferably lithium nitrate. By using a molten salt, the melting point is lowered compared to the case where lithium halide or other lithium salts are used alone, and ion exchange at a lower temperature becomes possible. The temperature during ion exchange may be, for example, above the melting point of the molten salt and below 600° C., below 500° C., below 400° C., or below 300° C. If the temperature during ion exchange is too high, an O3 type structure as a stable phase rather than an O2 type structure is easily generated. On the other hand, from the viewpoint of shortening the time taken for ion exchange, the temperature during ion exchange may be as high as possible.

[0090] 2.3S3

[0091] In S3, for the oxide containing Li obtained by the above-mentioned S2, a process different from the above-mentioned ion exchange is adopted to further dope Li, thereby being able to increase the molar ratio of Li in the oxide containing Li (the above-mentioned a). In S3, for example, for the oxide containing Li, a process different from the above-mentioned ion exchange can be adopted to further dope Li without imparting a driving force generated by a voltage. For example, the oxide containing Li can be doped with Li by contacting a Li doping source with the oxide containing Li. Specifically, in S3, it is preferred that: for the oxide containing Li, a reducing solution containing Li ions is contacted, thereby further doping Li with the oxide containing Li by a process different from the ion exchange. The so-called "reducing solution" means a reducing solution, for example, a solution containing an electrophilic reagent. As for the reducing solution, for example, it can be a solution obtained by dissolving an electrophilic reagent and a Li source in a solvent. The solvent can be various organic solvents that can dissolve electrophilic reagents and Li sources. As for the solvent, for example, ether solvents such as tetrahydrofuran and dimethoxyethane are preferred. Electrophilic reagents can be various substances that are dissolved in the above-mentioned solvents. Electrophilic reagents are preferably aromatic organic compounds such as biphenyl. Li sources can be various substances that are dissolved in the above-mentioned solvents to generate Li ions. The Li source can be metallic lithium or a Li compound. The concentration of electrophilic reagents and Li ions contained in the reducing solution can be appropriately determined according to the target doping amount. In S3, for example, only by contacting the above-mentioned reducing solution with the oxide containing Li, the oxide containing Li can be doped with Li. There is no particular limitation on the contact form between the reducing solution and the oxide containing Li. For example, the transition metal oxide containing Li can be impregnated with the reducing solution, or the transition metal oxide containing Li can be sprayed with the reducing solution. There is no particular limitation on the temperature during contact, and it can be heated or not. In addition, the oxide containing Li can be stirred after being immersed in the reducing solution. There is no particular limitation on the time for contacting the reducing solution with the oxide containing Li, and it can be appropriately determined according to the target doping amount.

[0092] 2.4S4

[0093] In S4, for example, lithium hydroxide is precipitated on the surface of the Li-containing oxide by exposing the Li-doped oxide in the above-mentioned S3 to an arbitrary dew point environment. That is, lithium hydroxide is precipitated on the surface of the Li-containing oxide by reacting a portion of the Li contained in the Li-containing oxide with water or the like, thereby obtaining the above-mentioned electrode active material 1. Here, the amount of lithium hydroxide precipitated on the surface of the Li-containing oxide can be adjusted by adjusting the dew point environment, exposure time, etc. In S4, it is sufficient to adjust the dew point environment, exposure time, etc. so that the electrode active material 1 obtained after exposure satisfies the above-mentioned relationship (1).

[0094] 3. Electrode composite materials

[0095] The electrode composite involved in one embodiment includes the electrode active material 1 disclosed above. There is no particular limitation on the components other than the electrode active material 1 contained in the electrode composite, and they can be appropriately determined according to the target performance. The electrode composite involved in one embodiment may include at least one of the electrode active material 1 disclosed above, an electrolyte, a conductive aid and a binder. The electrode composite 5 involved in one embodiment may optionally include other additives. As for the content of each of the active material, electrolyte, conductive aid and binder in the electrode composite, it can be appropriately determined according to the target battery performance. For example, the solid content contained in the electrode composite as a whole is set to 100% by mass, and the content of the electrode active material can be greater than 40% by mass and less than 100% by mass.

[0096] 3.1 Active substances

[0097] As for the active material contained in the electrode composite, it can be composed of only the electrode active material 1 disclosed above, or it can contain active materials (other active materials) other than the electrode active material 1. From the viewpoint of further improving the effect of the technology disclosed in the present invention, the proportion of other active materials in the overall active material contained in the electrode composite can be a small amount. For example, the overall active material contained in the electrode composite is set to 100 mass%, and the content of the electrode active material 1 disclosed above can be more than 50 mass% and less than 100 mass%, more than 60 mass% and less than 100 mass%, more than 70 mass% and less than 100 mass%, more than 80 mass% and less than 100 mass%, more than 90 mass% and less than 100 mass%, more than 95 mass% and less than 100 mass%, or, more than 99 mass% and less than 100 mass%. As for other active materials that can be contained in the electrode composite, all can be used as substances known as active materials.

[0098] 3.2 Electrolytes

[0099] The electrode composite may contain an electrolyte while containing the electrode active material 1 described above. The electrolyte that can be contained in the electrode composite may be a solid electrolyte, a liquid electrolyte, or a combination thereof. As a solid electrolyte, a solid electrolyte known as a solid electrolyte for a battery can be used. The solid electrolyte may be an inorganic solid electrolyte or an organic polymer electrolyte. In particular, the ion conductivity and heat resistance of the inorganic solid electrolyte are excellent. As an inorganic solid electrolyte, for example, oxide solid electrolytes, sulfide solid electrolytes, and ionic inorganic solid electrolytes can be listed. In particular, when the electrode composite 5 contains a sulfide solid electrolyte as a solid electrolyte, it is easy to ensure higher performance. As for the sulfide solid electrolyte, for example, at least Li, S, and P can be included as constituent elements. Alternatively, the electrode composite 5 may contain an ionic solid electrolyte as a solid electrolyte, for example, a solid electrolyte containing at least Li, Y, and halogen (at least one of Cl, Br, I, and F) as constituent elements. The solid electrolyte may be amorphous or crystalline. The solid electrolyte may be in the form of particles. The average particle size (D50) of the solid electrolyte can be, for example, greater than 10 nm and less than 10 μm. One solid electrolyte can be used alone or in combination of two or more. The liquid electrolyte (electrolyte) is a liquid containing lithium ions as carrier ions. The electrolyte can be an aqueous electrolyte or a non-aqueous electrolyte. As for the composition of the electrolyte, it can be the same as the composition known as the electrolyte of a lithium ion battery. The electrolyte can be a product of dissolving a lithium salt in water or a non-aqueous solvent. As a non-aqueous solvent, for example, various carbonate solvents can be listed. As a lithium salt, for example, lithium amide salts, LiPF6, etc. can be listed.

[0100] 3.3 Conductive additives

[0101] As the conductive aid that can be contained in the electrode composite material, for example, carbon materials such as vapor grown carbon fiber (VGCF), acetylene black (AB), Ketjen black (KB), carbon nanotubes (CNT), and carbon nanofibers (CNF); metal materials such as nickel, titanium, aluminum, and stainless steel can be listed. The conductive aid can be, for example, in the form of particles or fibers, and its size is not particularly limited. The conductive aid can be used alone or in combination of two or more.

[0102] 3.4 Binder

[0103] As the binder that can be contained in the electrode composite material, for example, butadiene rubber (BR) based binders, butylene rubber (IIR) based binders, acrylate butadiene rubber (ABR) based binders, styrene butadiene rubber (SBR) based binders, polyvinylidene fluoride (PVdF) based binders, polytetrafluoroethylene (PTFE) based binders, polyimide (PI) based binders, etc. can be listed. The binder can be used alone or in combination of two or more.

[0104] 3.5 Others

[0105] The electrode composite material may contain various additives in addition to the above-mentioned components, such as a dispersant, a lubricant, and the like.

[0106] 4. Battery

[0107] The electrode active material 1 can be used as a positive electrode active material of a battery, for example. Figure 3 As described above, a battery 100 according to one embodiment includes a positive electrode active material layer 10, an electrolyte layer 20, and a negative electrode active material layer 30. The positive electrode active material layer 10 includes the electrode active material 1 of the present disclosure.

[0108] 4.1 Positive electrode active material layer

[0109] The positive electrode active material layer 10 contains at least the electrode active material 1 disclosed above, and may further optionally contain an electrolyte, a conductive aid, a binder, etc. Furthermore, the positive electrode active material layer 10 may also contain various additives. In other words, the positive electrode active material layer 10 may be composed of the above-mentioned electrode composite material. In particular, when the positive electrode active material layer 10 contains a liquid electrolyte (electrolyte), a higher effect can be expected. There is no particular limitation on the shape of the positive electrode active material layer 10, for example, it may be a sheet-shaped positive electrode active material layer 10 having a substantially flat surface. There is no particular limitation on the thickness of the positive electrode active material layer 10, for example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 2 mm or less than 1 mm.

[0110] 4.2 Electrolyte layer

[0111] The electrolyte layer 20 is arranged between the positive electrode active material layer 10 and the negative electrode active material layer 30. The electrolyte layer 20 contains at least an electrolyte. The electrolyte layer 20 may contain at least one of a solid electrolyte and a liquid electrolyte, and may further optionally contain a binder, etc. There is no particular limitation on the content of the electrolyte and the binder, etc. in the electrolyte layer 20. Alternatively, the electrolyte layer 20 may have a separator, etc., for preventing the positive electrode active material layer 10 from contacting the negative electrode active material layer 30 while maintaining the liquid electrolyte. There is no particular limitation on the thickness of the electrolyte layer 20, for example, it may be 0.1 μm or more or 1 μm or more, or it may be 2 mm or less or 1 mm or less.

[0112] As the electrolyte contained in the electrolyte layer 20, it is sufficient to appropriately select the electrolyte (solid electrolyte and / or liquid electrolyte) exemplified as the electrolyte that can be contained in the above-mentioned positive electrode active material layer 10 (electrode composite). In particular, when the electrolyte layer 20 contains a liquid electrolyte (electrolyte), a higher effect can be expected. In addition, for the binder that can be contained in the electrolyte layer 20, it is sufficient to appropriately select the binder exemplified as the binder that can be contained in the above-mentioned positive electrode active material layer. Electrolytes and binders can be used alone or in combination of two or more. The separator can be any separator commonly used in batteries, for example, separators composed of resins such as polyethylene (PE), polypropylene (PP), polyester and polyamide can be listed. The separator can be a single-layer structure or a multi-layer structure. As a separator of a multi-layer structure, for example, a separator of a two-layer structure of PE / PP, or a separator of a three-layer structure of PP / PE / PP or PE / PP / PE can be listed. The spacer can be made of nonwoven fabric such as cellulose nonwoven fabric, resin nonwoven fabric, or glass fiber nonwoven fabric.

[0113] 4.3 Negative electrode active material layer

[0114] The negative electrode active material layer 30 contains at least a negative electrode active material. In addition, the negative electrode active material layer 30 may optionally contain an electrolyte, a conductive aid, a binder, and various additives. As for the content of each component in the negative electrode active material layer 30, it can be appropriately determined according to the target battery performance. For example, the solid content of the negative electrode active material layer 30 is set to 100% by mass, and the content of the negative electrode active material can be 40% by mass or more, 50% by mass or more, 60% by mass or more, or 70% by mass or more, and can be 100% by mass or less, less than 100% by mass, 95% by mass or less, or 90% by mass or less. Alternatively, the negative electrode active material layer 30 is set to 100% by volume, and a total of 85% by volume or more, 90% by volume or more, or 95% by volume or more of the negative electrode active material and optional electrolytes, conductive aids, and binders can be included, and the balance can be voids or other components. There is no particular limitation on the shape of the negative electrode active material layer 30, for example, it can be a sheet with a roughly flat surface. The thickness of the negative electrode active material layer 30 is not particularly limited, and may be, for example, 0.1 μm or more, 1 μm or more, 10 μm or more, or 30 μm or less, or 2 mm or less, 1 mm or less, 500 μm or less, or 100 μm or less.

[0115] As for the negative electrode active material, any material known as the negative electrode active material of the battery can be used. Among the known active materials, various materials that have a potential (charge and discharge potential) for absorbing and releasing ions as a lower potential than the above-mentioned positive electrode active material can be used. For example, silicon-based active materials such as Si, Si alloys, and silicon oxide; carbon-based active materials such as graphite and hard carbon; various oxide-based active materials such as lithium titanate; metallic lithium, lithium alloys, etc. can be used. Among them, when the negative electrode active material layer 30 contains Si as a negative electrode active material, the performance of the battery 100 is easily improved. The negative electrode active material can be used alone or in combination of two or more. As for the shape of the negative electrode active material, as long as it is a general shape of the negative electrode active material of the battery, it can be used. For example, the negative electrode active material can be in a particle shape. The negative electrode active material particles can be primary particles or secondary particles formed by the aggregation of multiple primary particles. The average particle size (D50) of the negative electrode active material particles may be, for example, 1 nm or more, 5 nm or more, or 10 nm or more, and may be 500 μm or less, 100 μm or less, 50 μm or less, or 30 μm or less. Alternatively, the negative electrode active material may be in the form of a sheet (foil, film) such as lithium foil. That is, the negative electrode active material layer 30 may be composed of a sheet of the negative electrode active material.

[0116] As the electrolyte that can be contained in the negative electrode active material layer 30, for example, the above-mentioned solid electrolyte, liquid electrolyte or a combination thereof can be listed. In particular, when the negative electrode active material layer 30 contains a liquid electrolyte (electrolyte), a higher effect can be expected. As for the conductive aid that can be contained in the negative electrode active material layer 30, for example, it is sufficient to appropriately select from the conductive aids exemplified as the conductive aids that can be contained in the above-mentioned positive electrode active material layer 10 (electrode composite 5). As for the binder that can be contained in the negative electrode active material layer 30, for example, it is sufficient to appropriately select from the binders exemplified as the binders that can be contained in the above-mentioned positive electrode active material layer 10 (electrode composite 5). The electrolyte, the conductive aid, and the binder can be used alone or in combination of two or more.

[0117] 4.4 Positive electrode collector

[0118] like Figure 3 As shown in , the battery 100 may include a positive electrode collector 40 in contact with the positive electrode active material layer 10. As for the positive electrode collector 40, any general positive electrode collector as a positive electrode collector of a battery can be used. In addition, the positive electrode collector 40 may have at least one shape selected from foil, plate, mesh, punched metal, and foam. The positive electrode collector 40 may be composed of a metal foil or a metal mesh. In particular, the metal foil has excellent handling properties. The positive electrode collector 40 may be composed of a plurality of foils. As a metal constituting the positive electrode collector 40, at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel can be listed. In particular, from the perspective of ensuring oxidation resistance, the positive electrode collector 40 may contain Al. The positive electrode current collector 40 may have some coating on its surface for the purpose of adjusting resistance, etc. For example, the positive electrode current collector 40 may have a carbon coating. In addition, the positive electrode current collector 40 may be a product of plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the positive electrode current collector 40 is composed of a plurality of metal foils, there may be some layers between the plurality of metal foils. There is no particular limitation on the thickness of the positive electrode current collector 40. For example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 1 mm or less than 100 μm.

[0119] 4.5 Negative Electrode Collector

[0120] like Figure 3As shown in , the battery 100 may include a negative electrode collector 50 in contact with the negative electrode active material layer 30. As for the negative electrode collector 50, any general negative electrode collector as a negative electrode collector of a battery can be used. In addition, the negative electrode collector 50 may be in the form of a foil, a plate, a mesh, a punched metal, a foam, etc. The negative electrode collector 50 may be a metal foil or a metal mesh, or may be a carbon sheet. In particular, the metal foil has excellent handling properties. The negative electrode collector 50 may be composed of a plurality of foils and sheets. As the metal constituting the negative electrode collector 50, at least one selected from Cu, Ni, Cr, Au, Pt, Ag, Al, Fe, Ti, Zn, Co, V, Mg, Pb, Ge, In, Sn, Zr, and stainless steel can be listed. In particular, from the viewpoint of ensuring reduction resistance and the viewpoint of being difficult to alloy with lithium, the negative electrode collector 50 may contain at least one metal selected from Cu, Ni, and stainless steel. The negative electrode current collector 50 may have some coating on its surface for the purpose of adjusting resistance, etc. For example, the negative electrode current collector 50 may have a carbon coating. The negative electrode current collector 50 may be an aluminum foil having a carbon coating. In addition, the negative electrode current collector 50 may be a product obtained by plating or vapor-depositing the above-mentioned metal on a metal foil or a substrate. In addition, when the negative electrode current collector 50 is composed of a plurality of metal foils, there may be some layers between the plurality of metal foils. There is no particular limitation on the thickness of the negative electrode current collector 50. For example, it may be greater than 0.1 μm or greater than 1 μm, and may be less than 1 mm or less than 100 μm.

[0121] 4.6 Other components

[0122] As for the battery 100, in addition to the above-mentioned structure, it can have a general structure as a battery. For example, it is a pole piece, a terminal, etc. The battery 100 can be a product in which the above-mentioned structures are housed inside an outer casing. As for the outer casing, any outer casing known as an outer casing of a battery can be adopted. In addition, a plurality of batteries 100 can be electrically connected arbitrarily, and can be overlapped arbitrarily to form a battery pack. In this case, the battery pack can be accommodated inside a known battery casing. As the shape of the battery 100, for example, a coin type, a stacked body type, a cylindrical type, a square type, etc. can be listed. The battery 100 can be a secondary battery.

[0123] The battery 100 can be manufactured by applying a known method, in addition to using the above-mentioned specific electrode active material 1. For example, it can be manufactured as follows. However, the manufacturing method of the battery 100 is not limited to the following method, and each layer can be formed by dry molding, etc.

[0124] (1) The electrode active material 1 constituting the positive electrode active material layer is dispersed in a solvent to obtain a positive electrode layer slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The positive electrode layer slurry is applied to the surface of the positive electrode collector using a scraper or the like, and then dried to form a positive electrode active material layer on the surface of the positive electrode collector to form a positive electrode.

[0125] (2) The negative electrode active material constituting the negative electrode active material layer is dispersed in a solvent to obtain a negative electrode layer slurry. The solvent used in this case is not particularly limited, and water or various organic solvents can be used. The negative electrode layer slurry is applied to the surface of the negative electrode collector using a scraper or the like, and then dried to form a negative electrode active material layer on the surface of the negative electrode collector to prepare a negative electrode.

[0126] (3) The layers are stacked in such a way that the electrolyte layer (solid electrolyte layer or separator) is sandwiched between the negative electrode and the positive electrode to obtain a laminate having a negative electrode collector, a negative electrode active material layer, an electrolyte layer, a positive electrode active material layer and a positive electrode collector in this order. Other components such as terminals are installed on the laminate as needed.

[0127] (4) The stack is housed in a battery case, and in the case of an electrolyte battery, the battery case is filled with an electrolyte, the stack is immersed in the electrolyte, and the stack is sealed in the battery case, thereby forming a secondary battery. In the case of an electrolyte battery, in the above-mentioned stage (3), the negative electrode active material layer, the separator, and the positive electrode active material layer may contain an electrolyte.

[0128] 5. Vehicles

[0129] The battery of the present disclosure has excellent cycle characteristics by using the electrode active material 1. Such a battery can be preferably used in at least one vehicle selected from a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV) and an electric vehicle (BEV). That is, the technology of the present disclosure also has the following aspects: a vehicle having a battery, the battery having a positive electrode active material layer, an electrolyte layer and a negative electrode active material layer, and the positive electrode active material layer contains the electrode active material 1 of the present disclosure.

[0130] Example

[0131] As described above, an embodiment of an electrode active material, etc. has been described, but the technology of the present disclosure can be variously modified outside the above-mentioned embodiment without departing from its main purpose. Below, examples are shown to explain the technology of the present disclosure in more detail, but the technology of the present disclosure is not limited to the following examples.

[0132] 1. Preparation of electrode active materials

[0133] 1.1 Preparation of P2-type Na-containing oxides

[0134] 1.1.1 Preparation of precursor

[0135] (1) MnSO4·5H2O, NiSO4·6H2O, and CoSO4·7H2O were weighed to obtain a target composition ratio (Mn:Ni:Co=5:2:3), and dissolved in distilled water to a concentration of 1.2 mol / L to obtain a first solution. In addition, Na2CO3 was dissolved in distilled water in another container to a concentration of 1.2 mol / L to obtain a second solution.

[0136] (2) 1000 mL of pure water was placed in a reaction container (with a baffle), and 500 mL of the first solution and 500 mL of the second solution were added dropwise at a rate of about 4 mL / min.

[0137] (3) After the dropwise addition was completed, the mixture was stirred at room temperature at a stirring speed of 150 rpm for 1 hour to obtain a product.

[0138] (4) The product is washed with pure water, separated into solid and liquid using a centrifuge, and the precipitate is recovered.

[0139] (5) The obtained precipitate was dried at 120° C. overnight, crushed in a mortar, and separated into coarse particles and fine particles by air flow classification. The fine particles were removed to obtain coarse particles as precursor particles.

[0140] 1.1.2 Fabrication of the complex

[0141] (1) Na 2 CO 3 and distilled water were weighed to give a concentration of 1150 g / L, and then stirred with a stirrer until the mixture was completely dissolved, thereby preparing a Na 2 CO 3 aqueous solution.

[0142] (2) The Na2CO3 aqueous solution and the precursor particles are weighed and mixed so that the composition after calcination described later becomes Na 0.8 Mn 0.5 Ni 0.2 Co 0.3 O2, thereby obtaining a slurry.

[0143] (3) The slurry was dried by spray drying to obtain a composite. Specifically, a spray drying device DL410 was used at a slurry feeding rate of 30 mL / min, an inlet temperature of 200°C, and a circulating air volume of 0.8 m 3 The slurry was air-dried under the conditions of 0.5047 W / min and a spray pressure of 0.3 MPa, thereby coating the surfaces of the precursor particles with Na2CO3 to obtain a composite.

[0144] 1.1.3 Firing of the composite

[0145] The composite was placed in an alumina crucible and sintered in an air atmosphere to obtain an oxide containing Na and having a P2 type structure. The sintering conditions were as follows (1) to (7).

[0146] (1) An alumina crucible containing the above-mentioned composite is placed in a heating furnace in an air atmosphere.

[0147] (2) The temperature in the heating furnace was raised from room temperature (25°C) to 600°C over 115 minutes.

[0148] (3) The temperature in the heating furnace is maintained at 600° C. for 360 minutes for preliminary calcination.

[0149] (4) After the preliminary firing, the temperature in the heating furnace was raised to 900°C and maintained at 900°C for 60 minutes for the main firing.

[0150] (5) After the main firing, the temperature in the heating furnace was lowered from the main firing temperature to 250°C, and the alumina crucible was taken out of the heating furnace at 250°C and naturally cooled outside the furnace in a dry atmosphere to 25°C in 10 minutes.

[0151] The fired product after natural cooling is pulverized in a dry atmosphere using a mortar, thereby obtaining oxide particles containing Na having a P2 type structure (P2 type particles).

[0152] 1.2 Ion Exchange

[0153] (1) LiNO 3 and LiCl were weighed to a molar ratio of 50:50, and mixed with the above-mentioned P2 type particles at a molar ratio of 10 times the minimum amount of Li required for ion exchange to obtain a mixture.

[0154] (2) Using an alumina crucible, ion exchange was performed in an air atmosphere at 280° C. for 1 hour to obtain a product containing an oxide containing Li.

[0155] (3) The salt remaining in the product is washed with pure water, and solid-liquid separation is performed by vacuum filtration to obtain a precipitate.

[0156] (4) The obtained precipitate was dried at 120°C overnight to obtain intermediate particles A. The intermediate particles A are composed of Li 0.6 Mn 0.5 Ni 0.2 Co 0.3 An oxide containing Li represented by O2. In addition, the crystal phase contained in the intermediate particle A was confirmed by XRD, and as a result, the intermediate particle A had an O2 type structure.

[0157] 1.3Li doping

[0158] (1) In a glove box (Ar atmosphere), biphenyl was mixed and dissolved in tetrahydrofuran (THF) so as to have a concentration of 1 mol / L to obtain a biphenyl solution.

[0159] (2) Li foil in an amount equal to the mole of biphenyl was added to the biphenyl solution and stirred for 2 hours to obtain a reducing solution containing 1 mol / L of Li ions.

[0160] (3) The intermediate particles A were added to the obtained reducing solution, and the mixture was immersed and stirred for 24 hours. The amount of the intermediate particles A was adjusted so that the ratio of the molar number of dissolved Li ions to the molar number of the intermediate particles A (Li / O2) was 0.4.

[0161] (4) The stirred intermediate particles A were washed with THF and vacuum filtered to separate the solid and liquid. The obtained precipitate was dried at 120°C overnight to obtain intermediate particles B. The intermediate particles B were composed of Li 0.98 Mn 0.5 Ni 0.2 Co 0.3 An oxide containing Li represented by O2. In addition, the crystal phase contained in the intermediate particle B was confirmed by XRD. As a result, the intermediate particle B had an O2 type structure.

[0162] 1.4 Precipitation of lithium hydroxide

[0163] (1) The obtained intermediate particles B were sealed in a screw bottle under an Ar environment and moved out of the glove box.

[0164] (2) The intermediate particles B are exposed under an arbitrary dew point environment to precipitate lithium hydroxide on the surface of the intermediate particles B to obtain an electrode active material for evaluation. By adjusting the dew point environment and exposure time, a variety of electrode active materials with different amounts of lithium hydroxide precipitation can be obtained.

[0165] (3) The various electrode active materials obtained were each sealed in a screw bottle again, moved into a glove box, and stored.

[0166] 2. Evaluation of the amount of lithium hydroxide precipitated in the electrode active material

[0167] For each of the above-mentioned multiple electrode active materials, an O1s spectrum was obtained by X-ray photoelectron spectroscopy (XPS). The measurement conditions of XPS are as follows. It should be noted that in the XPS measurement, the measurement point of 527.5eV was set as the starting point, the measurement point of 534eV was set as the end point, and the Shirley method was used to implement background processing.

[0168] Measurement device: Scanning X-ray photoelectron spectrometer (u-XPS) Quantera II (manufactured by Albuck PHI Co., Ltd.)

[0169] X-ray source used: mono-AlKa ray (1486.6V)

[0170] Photoelectron extraction angle: 35°

[0171] X-ray beam diameter: about 100 μm

[0172] Neutralizing gun conditions: 1.0V, 20μA

[0173] For each O1s spectrum obtained, waveform separation was performed using curve fitting (fitting based on the nonlinear least squares method), and the peak at the position of the binding energy of 531.4 eV and the peak at the position of 529.4 eV were separated to determine the areas S1 and S2 of each peak. It should be noted that the waveform separation was performed using the software "MultiPak" manufactured by Albuck PHI.

[0174] 3. Production of coin battery

[0175] Using each electrode active material, a coin battery (CR2032) was produced. The procedure for producing the coin battery is as follows.

[0176] (1) The electrode active material, acetylene black (AB) as a conductive aid, and polyvinylidene fluoride (PVdF) as a binder are weighed so that the mass ratio is electrode active material: AB: PVdF = 85:10:5, and dispersed and mixed in N-methyl-2-pyrrolidone to obtain a positive electrode composite slurry. The positive electrode composite slurry is coated on an aluminum foil and vacuum dried at 120° C. overnight to obtain a positive electrode as a laminate of a positive electrode active material layer and a positive electrode collector.

[0177] (2) In a mixed solvent of trifluoropropylene carbonate (TFPC) and trifluoromethyl ethyl carbonate (TFEMC) at a ratio of TFPC:TFEMC=30 volume %:70 volume %, LiPF6 was dissolved at a concentration of 1 M to obtain an electrolyte solution.

[0178] (3) As a negative electrode, prepare a metal lithium foil.

[0179] (4) Use the positive electrode, electrolyte and negative electrode to make a coin battery (CR2032).

[0180] 4. Evaluation of the charge and discharge characteristics of coin batteries

[0181] Each coin cell was tested in a thermostatic chamber maintained at 25°C over a voltage range of 2.0 to

[0182] The charge and discharge were repeated for 30 cycles at 4.8 V and 0.1 C rate (1 C = 240 mA / g), and the ratio of the discharge capacity after 30 cycles to the initial discharge capacity (capacity retention rate (%)) was determined.

[0183] 5. Evaluation results

[0184] In the following Table 1, for each electrode active material, the "area S1 of the peak from lithium hydroxide at 531.4 eV", "area S2 of the peak from O2-type Li-containing oxide at 529.4 eV" and "ratio of S1 to the sum of S1 and S2 (S1 / (S1+S2))" of the O1s energy spectrum obtained by XPS are shown. In addition, the "initial discharge capacity", "discharge capacity after 30 cycles" and "capacity retention rate" of each coin battery are shown in the following Table 1.

[0185]

Table 1

[0186]

[0187] exist Figure 4 The XPS-O1s spectra of the electrode active materials of Examples 2, 4, Comparative Examples 1 and 3 are shown in FIG. Figure 5 The relationship between S1 / (S1+S2) and the capacity maintenance rate is shown in FIG.

[0188] From Table 1, Figure 4 and 5 The results shown in show that when S1 / (S1+S2) in the XPS-O1s spectrum of the electrode active material is greater than 0.20 and less than 0.73, the capacity retention rate of the battery increases. In particular, when S1 / (S1+S2) is greater than 0.39 and less than 0.68, the capacity retention rate is significantly improved. It is believed that this is because, on the surface of the electrode active material, a moderate amount of lithium hydroxide is precipitated, thereby preventing contact between the active material and the electrolyte in the high potential region during charging, and inhibiting the decomposition of the electrolyte. On the other hand, if S1 / (S1+S2) exceeds 0.70, the capacity retention rate of the battery decreases. It is believed that this is because, on the surface of the electrode active material, lithium hydroxide is precipitated excessively, locally hindering the Li conduction between the active material and the electrolyte, and the active material located in the active material-electrolyte that does not hinder Li conduction is overused.

[0189] It is explained that, for the electrolyte (LiPF6) generally used in liquid system batteries, hydrogen fluoride is produced due to the trace amount of water in the battery. It is believed that the lithium hydroxide precipitated on the surface of the electrode active material reacts with hydrogen fluoride in the battery to become lithium fluoride. That is, in the above-mentioned coin battery, it is believed that a lithium fluoride layer is formed on the surface of the electrode active material, and it is believed that the stability of the potential is further improved.

[0190] 6. Summary

[0191] From the above results, it can be said that the cycle characteristics of a battery can be improved by configuring a battery using an electrode active material that satisfies the following (1) and (2).

[0192] (1) The electrode active material contains an O2-type Li-containing oxide and lithium hydroxide.

[0193] (2) The O1s spectrum of the electrode active material obtained by XPS satisfies the following relationship (1).

[0194] 0.20≤S1 / (S1+S2) ≤0.73 · · · (1)

[0195] S1: Area of ​​the peak derived from lithium hydroxide at 531.4 eV

[0196] S2: The area of ​​the peak derived from the O2-type Li-containing oxide at 529.4 eV.

Claims

1. An electrode active material comprising an O2-type Li-containing oxide and lithium hydroxide, The O1s energy spectrum of the electrode active material obtained by XPS satisfies the following relationship (1): 0.20≤S1 / (S1+S2)≤0.73 · · · (1) S1: Area of ​​the peak derived from lithium hydroxide at 531.4 eV S2: The area of ​​the peak derived from the O2-type Li-containing oxide at 529.4 eV.

2. The electrode active material according to claim 1, wherein The O1s energy spectrum satisfies the following relationship (1A): 0.39≤S1 / (S1+S2)≤0.68···(1A).

3. An electrode composite material comprising the electrode active material according to claim 1 or 2. 4 . A battery comprising a positive electrode active material layer, an electrolyte layer, and a negative electrode active material layer, wherein the positive electrode active material layer comprises the electrode active material according to claim 1 .

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