Positive electrode active material for lithium secondary batteries, electrodes for lithium secondary batteries, and lithium secondary batteries

Abstract

To provide a positive electrode active material for a lithium secondary battery with high discharge capacity.SOLUTION: A positive electrode active material for a lithium secondary battery having a layered structure containing secondary particles that are aggregates of primary particles includes an element M1 and an element M2, the element M1 is at least one element selected from the group consisting of Nb, W, Mo, Ta, La, B and P, and the element M2 is at least one element M2 selected from the group consisting of Ni, Co, and Mn, and (1) and (2) are satisfied.SELECTED DRAWING: None

Description

[Technical Field]

[0001] This invention relates to a positive electrode active material for lithium secondary batteries, an electrode for lithium secondary batteries, and a lithium secondary battery. [Background technology]

[0002] A known configuration of a lithium secondary battery includes a positive electrode having a positive electrode active material, a negative electrode, and an electrolyte in contact with both the positive and negative electrodes.

[0003] Electrolytes used in lithium-ion batteries include electrolytes containing organic solvents and solid electrolytes. In the following explanation, electrolytes and solid electrolytes will sometimes be collectively referred to as "electrolytes."

[0004] At the interface between the positive electrode and the electrolyte, the positive electrode active material of the positive electrode is in contact with the electrolyte. In lithium secondary batteries, lithium ions are released from the positive electrode active material into the electrolyte and inserted from the electrolyte into the positive electrode active material during charging and discharging. Therefore, the physical properties of the surface of the positive electrode active material are closely related to the insertion and release of lithium ions.

[0005] On the other hand, it is known that direct contact between the positive electrode active material and the electrolyte can cause side reactions during charging and discharging, leading to a decrease in battery performance. Examples of such side reactions include the oxidative decomposition of the electrolyte (when the electrolyte is a liquid electrolyte), which generates gas. This gas can cause the battery to swell.

[0006] Furthermore, if the electrolyte is a solid electrolyte, a side reaction may occur where the solid electrolyte is altered at the point of contact between the positive electrode active material and the solid electrolyte, forming a resistive layer. The formed resistive layer inhibits the movement of lithium ions. Here, "resistive layer" refers to, for example, a layer that does not have lithium ion conductivity.

[0007] To prevent degradation of battery characteristics, conventional methods have been considered that involve providing a reaction suppression section with lithium ion conductivity between the positive electrode active material and the electrolyte. The reaction suppression section protects the positive electrode active material and suppresses the above-mentioned side reactions. For example, Patent Document 1 discloses active material particles having a reaction suppression section on its surface, with lithium niobate as the forming material. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Publication No. 2010-170715 [Overview of the project] [Problems that the invention aims to solve]

[0009] When a reaction-inhibiting portion is provided on the surface of the positive electrode active material, the side reactions exemplified above become less likely to occur. However, positive electrode active materials equipped with a reaction-inhibiting portion tend to have high lithium-ion conduction resistance on the surface, and their charge / discharge capacity tends to decrease. Therefore, there is room for further improvement in order to achieve high capacity while suppressing side reactions.

[0010] The present invention has been made in view of the above circumstances, and aims to provide a positive electrode active material for a lithium secondary battery that has a compound with excellent lithium ion conductivity on the surface and inside of the secondary particles, which allows lithium ions to move smoothly and has a high discharge capacity. Furthermore, the present invention aims to provide an electrode for a lithium secondary battery and a lithium secondary battery using the positive electrode active material for a lithium secondary battery. [Means for solving the problem]

[0011] To solve the above problems, the present invention encompasses the following embodiments. [1] A positive electrode active material for a lithium secondary battery having a layered structure and comprising secondary particles which are aggregates of primary particles, comprising elements M1 and M2, wherein element M1 is at least one element selected from the group consisting of Nb, W, Mo, Ta, La, B and P, and element M2 is at least one element selected from the group consisting of Ni, Co and Mn, and satisfying (1) and (2) below. (1) The ratio α, which is the ratio of the atomic concentration (atomic%) of element M1 present on the surface of the secondary particle to the total amount of atomic concentrations (atomic%) of element M2 and element M1 present on the surface of the secondary particle, obtained by X-ray photoelectron spectroscopy (XPS) analysis, is 0.6 or more and 1 or less. (2) The ratio β, which is the ratio of the atomic concentration (atomic%) of element M1 present inside the secondary particle to the total amount of atomic concentration (atomic%) of element M2 and element M1 present inside the secondary particle, obtained by the X-ray photoelectron spectroscopy (XPS) analysis, is 0.08 or more and 0.20 or less. [2] The positive electrode active material for a lithium secondary battery according to [1], having a concentrated portion of element M1 at the grain boundary of the primary particle in the cross-section of the secondary particle as observed by transmission electron microscope-energy dispersive X-ray spectroscopy. [3] The positive electrode active material for lithium secondary batteries according to [1] or [2], wherein the content of Mn is 0.03 mol or more per 1 mol of the total amount of the element M2. [4] A positive electrode active material for lithium secondary batteries, represented by the following composition formula (I), as described in any one of [1] to [3]. Li x (Ni a Co b Mn c Z d M1 e )O δ (I) (The compositional formula (I) satisfies 0.98 ≦ x ≦ 1.80, 0.3 < a ≦ 1, 0 ≦ b ≦ 0.3, 0.03 ≦ c ≦ 0.7, 0 ≦ d ≦ 0.05, 0 < e ≦ 0.05, a + b + c + d + e = 1, and 2 ≦ δ < 3, Z is at least one element selected from the group consisting of Al, Zr, and Ti, and M1 is at least one element selected from the group consisting of Nb, W, Mo, Ta, La, B, and P.) [5] S, which is the ratio of the atomic concentration of Li present on the surface of the secondary particles to the atomic concentration of the element M1 present on the surface of the secondary particles, obtained by the X-ray photoelectron spectroscopy (XPS) analysis Li is 1 or more and 4 or less, and is the positive electrode active material for a lithium secondary battery according to any one of [1] to [4]. [6] I, which is the ratio of the atomic concentration of Li present inside the secondary particles to the atomic concentration of the element M1 present inside the secondary particles, obtained by the X-ray photoelectron spectroscopy (XPS) analysis Li is 10 or more and 50 or less, and is the positive electrode active material for a lithium secondary battery according to any one of [1] to [5]. [7] The BET specific surface area is 0.2 m 2 / g or more and 2 m 2 / g or less, and is the positive electrode active material for a lithium secondary battery according to any one of [1] to [6]. [8] D 10 , D 50 and D 90 satisfy the following (II), and are the positive electrode active material for a lithium secondary battery according to any one of [1] to [7]. (D 90 - D 10 ) / D 50 ≦ 1.0 (II) (D 10 is the 10% cumulative volume particle size of the positive electrode active material for the lithium secondary battery, D 50 is the 50% cumulative volume particle size of the positive electrode active material for the lithium secondary battery, and D 90 is the 90% cumulative volume particle size of the positive electrode active material for the lithium secondary battery.) [9] The positive electrode active material for a lithium secondary battery according to any one of [1] to [8], which is for a solid lithium secondary battery. A lithium secondary battery electrode containing a positive electrode active material for lithium secondary batteries as described in any one of

[10] [1] to [9]. A lithium secondary battery including the lithium secondary battery electrodes described in

[11]

[10] . [Effects of the Invention]

[0012] According to the present invention, a positive electrode active material for a lithium secondary battery is provided, comprising a compound with excellent lithium ion conductivity on the surface and inside of secondary particles, which allows lithium ions to move smoothly and provides a high discharge capacity. Furthermore, an electrode for a lithium secondary battery and a lithium secondary battery using the positive electrode active material for a lithium secondary battery can be provided. [Brief explanation of the drawing]

[0013] [Figure 1] This is a schematic diagram showing an example of a lithium-ion secondary battery. [Figure 2] This is a schematic diagram showing an example of an all-solid-state lithium secondary battery. [Modes for carrying out the invention]

[0014] In this specification, metal composite compounds (MCCs) are hereinafter referred to as "MCCs". Cathode Active Material for lithium secondary batteries will be referred to as "CAM" below.

[0015] The CAM in this embodiment includes secondary particles, which are aggregates of primary particles, and has a layered structure. In this embodiment, CAM is an aggregate of multiple particles. One form of CAM in this embodiment is a powder. In this embodiment, the aggregate of multiple particles may consist only of secondary particles, or it may be a mixture of primary and secondary particles.

[0016] In this embodiment, "primary particle" refers to a particle that does not have visible grain boundaries when observed at a field of view of 1,000x to 30,000x using a scanning electron microscope or the like. In this specification, "secondary particle" means a particle formed by the three-dimensional aggregation of multiple primary particles with gaps between them. In other words, a secondary particle is an aggregate of primary particles.

[0017] The notation "Li" indicates the element Li, not the metallic Li unless otherwise specified. The same applies to the notation of other elements such as Ni, Co, Mn, Nb, W, Mo, Ta, La, B, and P.

[0018] When a numerical range is written as, for example, "1-10μm" or "1~10μm," it means the range from 1μm to 10μm, including the lower limit of 1μm and the upper limit of 10μm.

[0019] <Active material for positive electrode in lithium secondary batteries> The CAM of this embodiment includes elements M1 and M2. Element M1 is at least one element selected from the group consisting of Nb, W, Mo, Ta, La, B, and P, and element M2 is at least one element selected from the group consisting of Ni, Co, and Mn. Preferably, element M1 is at least one element selected from the group consisting of Nb, W, and B, and preferably element M2 includes Ni and at least one element selected from the group consisting of Co and Mn.

[0020] In this embodiment, element M1 is present on the surface and inside the secondary particles of the CAM. An example of the inside of a secondary particle is the grain boundary between primary particles. When element M1 is present on the surface of a secondary particle, the area where element M1 is present can function as a protective film that suppresses side reactions. When element M1 is present inside a secondary particle, lithium ion conductivity inside the secondary particle is improved in the area where element M1 is present.

[0021] This invention optimizes the uneven distribution of element M1 on the surface and within secondary particles. Specifically, in this embodiment, the CAM contains elements M1 and M2 in specific ratios on the surface and inside the secondary particles.

[0022] (1) In this embodiment, the CAM has an α defined below that is between 0.6 and 1. α is the ratio of the atomic concentration (atomic%) of element M1 present on the surface of a secondary particle to the total atomic concentration (atomic%) of element M1 and element M2 present on the surface of the secondary particle (element M1 + element M2). In other words, α is the atomic concentration ratio "element M1 / (element M1 + element M2)" on the surface of the secondary particle.

[0023] In this specification, the "surface" of a secondary particle refers to a range of approximately 10 nm in the depth direction from the surface of the secondary particle contained in the CAM toward the center of the particle.

[0024] The value of α is preferably 0.65 or higher, more preferably 0.70 or higher, and even more preferably 0.74 or higher. It is also preferably 0.98 or lower, more preferably 0.96 or lower, and even more preferably 0.95 or lower. The above upper and lower limits can be combined in any way. In this embodiment, 0.65-0.98 is preferred, 0.70-0.96 is more preferred, and 0.75-0.95 is even more preferred.

[0025] If α is above the lower limit mentioned above, it means that the proportion of element M2 exposed on the surface of secondary particles contained in CAM is small. In this case, the decomposition of CAM between CAM and the electrolyte is suppressed, making it easier to obtain a high discharge capacity.

[0026] If α is below the above upper limit, it means that the depth of the region containing element M1 on the surface of the secondary particles in CAM is shallow. During the charge-discharge reaction, lithium ions move between the electrolyte and CAM as the valence of element M2 ions changes. In this case, if α is below the above upper limit, the distance between the element M2 ions and the electrolyte is short, meaning that the distance lithium ions travel is short and they diffuse easily. Lithium ions that diffuse easily can easily penetrate from the surface into the interior of the secondary particles, making it easier to obtain a high discharge capacity.

[0027] [Method for measuring α] Elements M1 and M2 are present on the secondary particle surface of CAM. Therefore, when CAM is analyzed by X-ray photoelectron spectroscopy (XPS), photoelectrons corresponding to the binding energies of elements M1 and M2 are detected. The atomic concentrations of elements M1 and M2 on the secondary particle surface are determined from the analysis results using XPS. Specifically, XPS analysis of CAM is performed under the following conditions, and the peaks corresponding to each element are identified from the resulting narrow scan spectrum of CAM. Note that the peak originating from the CC bond of C1s is corrected for charge at 286.4 eV before peak identification. Measurement method: X-ray photoelectron spectroscopy (XPS) X-ray source: AlKα ray (1486.6eV) X-ray spot diameter: 100 μm PassEnergy: 112eV Step: 0.1eV Dwelltime: 50ms Neutralization conditions: Neutralization electron gun (acceleration voltage adjusted according to the element, current 100 μA)

[0028] For example, the ULVAC-PHI PHI5000 VersaProbe III X-ray photoelectron spectrometer can be used.

[0029] Under the above conditions, the detection depth of XPS is approximately 10 nm in the depth direction from the surface of the CAM toward the center of the particle.

[0030] The peaks corresponding to each element can be identified using existing databases.

[0031] The photoelectron intensity of element M1, Nb, is taken from the integral value of the waveform of Nb3d.

[0032] The photoelectron intensity of element M1, Ta, is taken from the integral value of the Ta4f waveform.

[0033] The photoelectron intensity of element M1, Mo, is obtained by using the integral value of the waveform of Mo3d.

[0034] The photoelectron intensity of element M1, B, is taken from the integral value of the B1s waveform.

[0035] The photoelectron intensity of element M1, P, is taken from the integral value of the P2p waveform.

[0036] The photoelectron intensity of element M1, W, is obtained by using the integral value of the waveform of W4f or W4d.

[0037] The photoelectron intensity of La, which is element M1, is obtained by using the integral value of the La3d waveform.

[0038] For element M2, Ni, the integral value of the Ni2p3 / 2 waveform is used as the photoelectron intensity.

[0039] For the photoelectron intensity of Co, which is element M2, the integral value of the Co2p3 / 2 waveform is used.

[0040] For element M2, the photoelectron intensity of Mn is taken from the integral value of the Mn2p1 / 2 waveform.

[0041] The integral value of the Li1s waveform is used as the photoelectron intensity of Li.

[0042] The photoelectron intensity of O is taken from the integral value of the O1s waveform.

[0043] If an elemental peak overlaps with the peaks of other elements, the atomic concentration of that element is calculated by using the peaks of other orbitals.

[0044] The atomic concentrations of elements M1, M2, and Li are determined as follows: First, the equivalent number of atoms for each element is determined by combining the integral value of the photoelectron peak of each element with a sensitivity coefficient specific to the instrument. Then, the atomic concentration is calculated by combining the equivalent number of atoms. If the CAM has multiple elements M1 or M2, the atomic concentration of element M1 or element M2 is the sum of the atomic concentrations of each element M1 or each element M2.

[0045] The atomic concentration (atomic%) of element M1 is calculated using the following formula. Atomic concentration of element M1 = (Converted number of atoms of element M1 / ​​(Converted number of atoms of element M2 + Converted number of atoms of element M1 + Converted number of atoms of Li + Converted number of atoms of O))

[0046] The atomic concentration (atomic%) of element M2 is calculated using the following formula. Atomic concentration of element M2 = (Converted number of atoms of element M2 / (Converted number of atoms of element M2 + Converted number of atoms of element M1 + Converted number of atoms of Li + Converted number of atoms of O))

[0047] The atomic concentration (atomic%) of Li is calculated using the following formula. Li atomic concentration = (Converted number of Li atoms / (Converted number of element M2 atoms + Converted number of element M1 atoms + Converted number of Li atoms + Converted number of O atoms))

[0048] α is calculated from the atomic concentrations of element M1 and element M2.

[0049] (2) In this embodiment, the CAM has a β value of 0.08-0.20, as defined below. β is the ratio of the atomic concentration (atomic%) of element M1 present inside the secondary particle to the total atomic concentration (atomic%) of element M2 present inside the secondary particle (element M1 + element M2). In other words, β is the atomic concentration ratio "element M1 / (element M1 + element M2)" inside the secondary particle.

[0050] β is preferably 0.08 or higher, more preferably 0.09 or higher. Furthermore, 0.18 or lower is preferred, and 0.15 or lower is more preferred. The above upper and lower limits can be combined in any way. In this embodiment, 0.08-0.18 is preferred, and 0.09-0.15 is more preferred.

[0051] A CAM in which β is greater than or equal to the lower limit above means that a moderate amount of a compound containing element M1 and exhibiting excellent lithium-ion conductivity is present inside the secondary particles. In this case, during the charge-discharge reaction, lithium ions can move from the surface to the interior of the CAM via the compound containing element M1 and exhibiting excellent lithium-ion conductivity present inside the secondary particles of the CAM, allowing the charge-discharge reaction to proceed smoothly and thus increasing the discharge capacity of the lithium-ion battery.

[0052] Furthermore, if β is below the above upper limit, it means that there is a high proportion of M2 ions that are continuously linked together within the secondary particles of CAM. Ions of element M2 undergo a change in valence during charge-discharge reactions within the secondary particles of CAM. When M2 ions are continuously linked together, electrons can move through the M2 ions that can change valence, which can increase the discharge capacity of the lithium-ion battery.

[0053] [Method for measuring beta] In this embodiment, elements M1 and M2 are also present inside the secondary particles of the CAM. Therefore, XPS analysis of the CAM subjected to the Ar ion sputtering treatment described below detects photoelectrons corresponding to the binding energies of elements M1 and M2 inside the secondary particles.

[0054] In this specification, "interior" refers to the region exposed by performing Ar ion sputtering on secondary particles in the CAM under the same conditions as sputtering to a depth of 100 nm in the case of an SiO2 film using an XPS internal apparatus. The etching rate for an SiO2 film is, for example, about 25 nm / min.

[0055] XPS analysis and calculation of the atomic concentrations of each element are performed on the interior of the CAM secondary particles exposed by the Ar ion sputtering process described above, similar to the method for measuring α described above. This allows us to obtain the atomic concentrations of element M2 and element M1 present inside the secondary particles. By calculating the ratio of these concentrations, β can be determined.

[0056] (3) The CAM of this embodiment is defined as S Li It is preferable that conditions 1-4 are met. S Li This is the ratio of the atomic concentration of Li present on the surface of the secondary particle to the atomic concentration of element M1 present on the surface of the secondary particle, obtained by the aforementioned XPS analysis. That is, S Li This is the atomic concentration ratio "Li / element M1" on the surface of the secondary particle.

[0057] S Li A value of 1.2 or higher is more preferable, 1.4 or higher is even more preferable, and 1.6 or higher is particularly preferable. Also, S Li A value of 3.8 or less is more preferable, 3.6 or less is even more preferable, and 3.4 or less is particularly preferable.

[0058] S Li The above upper and lower limits can be combined in any way. Examples of combinations include S Li These are 1.2-3.8, 1.4-3.6, and 1.6-3.4.

[0059] S Li If the value is above the lower limit mentioned above, it is easier to obtain a CAM with excellent lithium-ion conductivity and high discharge capacity. Also, SLi If the value is below the above upper limit, the resulting CAM tends to have fewer surface residues such as lithium carbonate and lithium hydroxide, which in turn tends to increase the discharge capacity. S Li This can be calculated from the atomic concentration of element M1 and the atomic concentration of Li, using the same procedure as described in [Method for measuring α] above.

[0060] (4) The CAM of this embodiment is defined as I Li It is preferable that the value is between 10 and 50. I Li This is the ratio of the atomic concentration of Li present inside the secondary particle to the atomic concentration of element M1 present inside the secondary particle, obtained by the aforementioned XPS analysis. That is, I Li This is the atomic concentration ratio "Li / element M1" within the secondary particle.

[0061] I Li It is more preferable that it be 12 or more, and even more preferable that it be 14 or more. Also, I Li It is more preferable that the value be 45 or less, and even more preferable that it be 40 or less.

[0062] I Li The above upper and lower limits can be combined in any way. Examples of combinations include, Li The values ​​are 12-45 and 14-40.

[0063] I Li If the value is above the lower limit mentioned above, the interior of the secondary particles is rich in Li, making it easier to obtain a CAM with excellent lithium ion conductivity and high discharge capacity. Also, I Li If the value is below the above upper limit, it means that there is a sufficient amount of element M1, which assists lithium ion conduction, making it easier to obtain a CAM with excellent lithium ion conductivity and high discharge capacity. I Li This can be calculated from the atomic concentration of element M1 and the atomic concentration of Li, using the same procedure as described in the [Method for Measuring β] above.

[0064] ≪Concentration section≫ In this embodiment, it is preferable that the CAM has a concentration of element M1 at the grain boundaries of primary particles in the cross-section of secondary particles observed by transmission electron microscopy-energy dispersive X-ray spectroscopy.

[0065] "There is an element M1-enriched region at the grain boundary of the primary particle" means that there is a region on the surface of the primary particle, or in the gap between primary particles, where element M1 is concentrated. If the concentrated region is located on the surface of the primary particle, element M1 may be present as a solid solution on the surface of the primary particle. If the concentrated region is located in the gaps between primary particles, a compound containing element M1 may be present at the grain boundaries between primary particles.

[0066] The cross-section of secondary particles can be obtained using the following method.

[0067] [How to obtain a cross-section] In this specification, the "cross-section" of a secondary particle refers to the exposed region when CAM is thin-sectioned using a focused ion beam (FIB).

[0068] [How to check the concentrated portion] Grain boundaries and concentrated regions can be identified, for example, by a common transmission electron microscope (TEM)-energy dispersive X-ray spectroscopy (EDX) technique.

[0069] Specifically, the cross-section obtained using the method described above [Method for obtaining the cross-section] is observed using TEM at an appropriate magnification. In the obtained TEM observation image, for example, adjacent primary particles A and B are continuously analyzed using EDX from the interior of primary particle A to the interior of primary particle B, and E1, which is the concentration ratio of element M1 to element M2, is determined.

[0070] Next, we determine the ratio of element M1 to element M2, E2, when performing surface analysis using EDX on the interior of a single primary particle, i.e., the region without grain boundaries. Areas where the E1 / E2 ratio is greater than 1 are considered to have a concentrated region. Areas where the E1 / E2 ratio is less than 1 are considered to have no concentrated region.

[0071] The presence of element M1-enriched regions at the grain boundaries of the primary particles constituting the secondary particles allows lithium ion desorption and insertion to proceed smoothly along these enriched regions. In this case, the utilization rate of CAM within the positive electrode is improved, making it easier to reduce resistance and improve discharge capacity.

[0072] For transmission electron microscopes, for example, the JEM-2100F manufactured by JEOL Ltd. can be used. For EDX, the Centurio manufactured by JEOL Ltd. can be used.

[0073] ≪BET specific surface area≫ The BET specific surface area of ​​CAM is 0.2-2m². 2 / g is preferred. The BET specific surface area is 0.3m². 2 More preferably 0.4m / g or more, 2 A value of 1.8 m² or more is even more preferable. Furthermore, a BET specific surface area of ​​1.8 m² is desirable. 2 More preferably less than / g, and 1.5m 2 It is more preferable that the condition be less than or equal to / g.

[0074] The above upper and lower limits for the BET specific surface area can be combined in any way. For example, the BET specific surface area is 0.3-1.8 m². 2 / g, 0.4-1.5m 2 It is / g.

[0075] Using a CAM whose BET specific surface area is greater than or equal to the lower limit mentioned above increases the reaction interface of the CAM, making it easier for lithium ions to enter and exit, thus tending to increase the discharge capacity. When a CAM with a BET specific surface area below the above upper limit is used, the contact area between the CAM and the electrolyte does not increase easily, and film formation due to electrolyte decomposition is less likely to occur. With less of this film, lithium ion conductivity is less likely to be inhibited, and thus the discharge capacity tends to be higher.

[0076] [Measurement of BET specific surface area] The BET specific surface area of ​​CAM can be measured using a BET specific surface area measuring device. For example, the Macsorb® manufactured by Mountec can be used as a BET specific surface area measuring device. When measuring powdered CAM, it is preferable to pre-treat it by drying it in a nitrogen atmosphere at 105°C for 30 minutes.

[0077] ≪D 10 , D 90 and D 50 ≫ CAM is D 10 , D 90 and D 50 It is preferable that the following (II) is satisfied. (D 90 -D 10 ) / D 50 ≤1.0 ···(II) ((II) Medium, D 10 This is the 10% cumulative volume particle size of CAM, and D 50 This is the 50% cumulative volume particle size of CAM, and D 90 This represents the 90% cumulative volume particle size of CAM.

[0078] D 10 , D 90 and D 50 (II)-1 is preferred, and (II)-2 is more preferred. 0.2≦(D 90 -D 10 ) / D 50 ≤0.8 ···(II)-1 0.2≦(D 90 -D 10 ) / D 50 ≤0.6 ···(II)-2

[0079] CAMs that satisfy (II) are easier to fill when manufacturing the positive electrode and have good contact with the conductive additive, so the discharge capacity tends to be improved.

[0080] [D 10 , D 90 and D 50 [Measurement] In this specification, the D of CAM 10 (μm), D 50 (μm) and D 90 (μm) can be measured by the following dry method.

[0081] Specifically, first, the dry particle size distribution is measured using a laser diffraction particle size analyzer with CAM2g to obtain a volume-based cumulative particle size distribution curve. In the obtained cumulative particle size distribution curve, the particle diameter values ​​at 10%, 50%, and 90% accumulation from the fine particle side are D, respectively. 10 , D 50 , D 90 That is the case. For example, the Malvern MS2000 laser diffraction particle size analyzer can be used.

[0082] In this embodiment, the CAM preferably contains 0.03 mol or more of Mn per 1 mol of the total amount of element M2, and more preferably 0.03-0.7 mol. When the proportion of Mn is above the aforementioned lower limit, the lithium secondary battery becomes highly thermally stable.

[0083] CAM is preferably represented by the following compositional formula (I). Li x (Ni a Co b Mn c Z d M1 e )O δ …(I) (The compositional formula (I) satisfies 0.98 ≦ x ≦ 1.80, 0.3 < a ≦ 1, 0 ≦ b ≦ 0.3, 0.03 ≦ c ≦ 0.7, 0 ≦ d ≦ 0.05, 0 < e ≦ 0.05, a + b + c + d + e = 1, and 2 ≦ δ < 3. Z is at least one element selected from the group consisting of Al, Zr, and Ti, and M1 is at least one element selected from the group consisting of Nb, W, Mo, Ta, La, B, and P.)

[0084] x preferably satisfies 1.00 ≦ x ≦ 1.60. Also, from the perspective of obtaining a lithium secondary battery with high cycle characteristics, x in the compositional formula (I) is more preferably 1.01 or more, and even more preferably 1.03 or more. Further, from the perspective of suppressing the formation of the resistance layer, x in the compositional formula (I) is more preferably 1.50 or less, and even more preferably 1.30 or less.

[0085] The upper and lower limit values of x can be arbitrarily combined. As examples of the combination, x is 1.01 - 1.50, 1.03 - 1.30.

[0086] Also, from the perspective of obtaining a lithium-ion secondary battery with a high capacity, a in the compositional formula (I) preferably exceeds 0.40, more preferably is 0.45 or more, even more preferably is 0.50 or more, and particularly preferably is 0.55 or more. Further, from the perspective of obtaining a lithium secondary battery with high thermal stability, a in the compositional formula (I) is more preferably 0.98 or less, even more preferably is 0.95 or less, and even more preferably is 0.90 or less.

[0087] The upper and lower limit values of a can be arbitrarily combined. In the compositional formula (I), a may be 0.45 - 0.98, may be 0.50 - 0.95, or may be 0.55 - 0.90.

[0088] b preferably satisfies 0 ≦ b ≦ 0.25. Also, from the perspective of obtaining a lithium secondary battery with high cycle characteristics, b in the compositional formula (I) more preferably exceeds 0, and even more preferably exceeds 0 and is 0.25 or less.

[0089] From the perspective of obtaining a lithium secondary battery with high cycle characteristics, c in the composition formula (I) is preferably 0.05 or more, more preferably 0.10 or more, still more preferably 0.20 or more, and particularly preferably 0.25 or more. Further, from the perspective of obtaining a lithium secondary battery with high storage stability at high temperature (for example, in an environment of 60°C), c in the composition formula (I) is preferably 0.50 or less, more preferably 0.40 or less, and still more preferably 0.30 or less. The upper limit value and the lower limit value of c can be arbitrarily combined. In the composition formula (I), c may be 0.05 - 0.50, may be 0.20 - 0.40, or may be 0.25 - 0.30.

[0090] It is preferable that c satisfies 0.05 ≤ c ≤ 0.50.

[0091] It is preferable that d satisfies 0 ≤ d ≤ 0.03.

[0092] It is preferable that e satisfies 0 < e ≤ 0.03.

[0093] [Composition analysis] The composition analysis of CAM (composition formula (I), the content of the above-mentioned Mn) can be carried out using an inductively coupled plasma optical emission spectrometer (for example, SPS3000 manufactured by SII NanoTechnology Inc.) after dissolving CAM in hydrochloric acid.

[0094] (Crystal structure) In this specification, the "layered structure" means a hexagonal crystal structure or a monoclinic crystal structure.

[0095] The hexagonal crystal structure is P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P 31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P62, P64, P63 It belongs to one of the space groups selected from the group consisting of P-6, P6 / m, P63 / m, P622, P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P63 / mcm, and P63 / mmc.

[0096] Furthermore, monoclinic crystal structures belong to one of the space groups selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c, and C2 / c.

[0097] Of these, in order to obtain a lithium secondary battery with a high discharge capacity, the crystal structure is preferably either a hexagonal crystal structure belonging to the space group R-3m, or a monoclinic crystal structure belonging to C2 / m, or both.

[0098] [How to confirm layered structure] Whether or not CAM has a layered structure can be confirmed by observing the crystal structure using a powder X-ray diffraction analyzer (for example, Ultima IV manufactured by Rigaku Corporation).

[0099] It is preferable that a compound containing the elements M1 and Li is present on the surface of the secondary particles of CAM. Specifically, examples include lithium niobate, lithium tantalate, lithium lanthanum oxides such as lithium lanthanum zirconium oxide and lithium lanthanum titanium oxide, lithium tungstate, lithium phosphate, and lithium borate.

[0100] [Measurement of initial discharge capacity] In this embodiment, the initial discharge capacity using CAM can be measured by the following method. This document describes a method for evaluating the initial discharge capacity of a solid-state lithium-ion battery, using solid-state lithium-ion batteries as an example.

[0101] <Manufacturing of solid-state lithium-ion secondary batteries> Perform the following operations inside a glove box under an argon atmosphere.

[0102] (Preparation of positive electrode composite material) Weigh out 1.000 g of CAM, 0.0543 g of conductive material (acetylene black), and 8.6 mg of solid electrolyte (MSE, Li6PS5Cl). Mix the CAM, conductive material, and solid electrolyte in a mortar for 15 minutes to prepare the positive electrode mixture powder.

[0103] (Battery making) A solid electrolyte powder is placed in a polyethylene terephthalate tube (PET tube, inner diameter 10 mm) into which a SUS rod (diameter 10 mm) has been inserted. Then, the SUS rod is inserted from above and pressed at 10 MPa to form a solid electrolyte layer with a diameter of 10 mm. After that, the SUS rod inserted from above is removed, 15 mg of the above-mentioned positive electrode composite powder is placed on top of the solid electrolyte layer, a SUS plate (diameter 10 mm) to be used as a current collector foil is placed on top, and then the SUS rod is inserted. Furthermore, indium foil and lithium metal foil are placed on top of the solid electrolyte layer opposite to the positive electrode composite powder, and after uniaxial pressing at 14 MPa, the assembly is restrained at 6 MPa to produce a solid lithium-ion battery.

[0104] <Charge / Discharge Test> Using the solid lithium-ion battery prepared by the method described above, charge and discharge tests will be conducted under the following conditions.

[0105] (Charge / discharge conditions) Test temperature: 60℃ (charge / discharge) Maximum charging voltage 3.68V, charging current density 0.1C, cutoff current density 0.02C, constant current-constant voltage charging. Minimum discharge voltage 1.88V, discharge current density 0.1C, constant current discharge.

[0106] If the initial discharge capacity measured by the above method is 172 mAh / g or more, it is evaluated as "having a high discharge capacity".

[0107] <Manufacturing method of CAM> The manufacturing method of CAM of this embodiment includes a step of introducing a coating material raw material containing element M1 two or more times. Specifically, it includes the manufacturing process (A) or manufacturing process (B) described later, and a step of mixing the obtained fired product and the coating material raw material containing element M1.

[0108] In manufacturing CAM, first, it is preferable to prepare MCC containing at least one element M2 selected from the group consisting of Ni, Co, and Mn, and fire the MCC with an appropriate lithium compound. As MCC, metal composite hydroxide or metal composite oxide is preferable.

[0109] Hereinafter, an example of the manufacturing method of CAM will be described separately for the manufacturing process of MCC and the manufacturing process of CAM.

[0110] (Manufacturing process of MCC) MCC can usually be manufactured by a known coprecipitation method. As the coprecipitation method, a generally known batch-type coprecipitation method or continuous coprecipitation method can be used. Hereinafter, the manufacturing method of MCC will be described in detail using a metal composite hydroxide containing Ni, Co, and Mn as an example.

[0111] First, by the coprecipitation method, particularly the continuous coprecipitation method described in JP-A2002-201028, a nickel salt solution, a cobalt salt solution, a manganese salt solution, and a complexing agent are reacted to produce a metal composite hydroxide represented by Ni a Co b Mn c (OH)2 (where 0 < a + b + c ≦ 1).

[0112] The nickel salt as the solute of the nickel salt solution is not particularly limited, and for example, any one or two or more of nickel sulfate, nickel nitrate, nickel chloride, and nickel acetate can be used.

[0113] As the cobalt salt which is the solute of the above cobalt salt solution, for example, any one or two or more of cobalt sulfate, cobalt nitrate, cobalt chloride, and cobalt acetate can be used.

[0114] As the manganese salt which is the solute of the above manganese salt solution, for example, any one or two or more of manganese sulfate, manganese nitrate, manganese chloride, and manganese acetate can be used.

[0115] The above metal salts are used in a ratio corresponding to the composition ratio of the above Ni a Co b Mn c (OH)2. That is, each metal salt is used in an amount such that the molar ratio of Ni in the solute of the nickel salt solution, Co in the solute of the cobalt salt solution, and Mn in the solute of the manganese salt solution is Ni a Co b Mn c (OH)2 corresponds to a:b:c.

[0116] Moreover, the solvents of the nickel salt solution, the cobalt salt solution, and the manganese salt solution are water. That is, the solvents of the nickel salt solution, the cobalt salt solution, and the manganese salt solution are aqueous solutions.

[0117] The complexing agent is a compound capable of forming a complex with nickel ions, cobalt ions, and manganese ions in an aqueous solution. Examples of the complexing agent include ammonium ion donors (ammonium salts such as ammonium hydroxide, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, etc.), hydrazine, ethylenediaminetetraacetic acid, nitrilotriacetic acid, uracil diacetic acid, and glycine.

[0118] When a complexing agent is used, the amount of complexing agent in a mixture containing the nickel salt solution, the arbitrary metal salt solution, and the complexing agent should, for example, have a molar ratio to the total number of moles of the metal salt that is greater than 0 and 2.0 or less.

[0119] In the coprecipitation method, to adjust the pH of the mixture containing the nickel salt solution, the arbitrary metal salt solution, and the complexing agent, an alkali metal hydroxide is added to the mixture before its pH changes from alkaline to neutral. Examples of alkali metal hydroxides include sodium hydroxide or potassium hydroxide. In this specification, the pH value is defined as the value measured when the temperature of the mixture is 40°C. The pH of the mixture is measured when the temperature of the mixture sampled from the reaction vessel reaches 40°C.

[0120] When the above nickel salt solution, cobalt salt solution, and manganese salt solution, along with a complexing agent, are continuously supplied to the reaction vessel, Ni, Co, and Mn react, and Ni a Co b Mn c (OH)2 is produced.

[0121] During the reaction, the temperature of the reaction vessel is controlled to be within a range of, for example, 20-80°C, preferably 30-70°C.

[0122] Furthermore, during the reaction, the pH value in the reaction vessel is controlled to be within the range of, for example, pH 9-13, preferably pH 11-13.

[0123] The substances in the reaction vessel should be stirred and mixed as needed. In the continuous coprecipitation method, a reaction vessel of the type that allows for overflow of the formed reaction precipitate for separation can be used.

[0124] In addition to controlling the above conditions, various gases, such as inert gases like nitrogen, argon, and carbon dioxide, oxidizing gases like air and oxygen, or mixtures thereof, may be supplied into the reaction vessel.

[0125] More specifically, the reaction vessel may be kept in an inert atmosphere. An inert atmosphere in the reaction vessel suppresses the aggregation of elements in the mixture that are more easily oxidized than Ni, preventing them from condensing before Ni. Therefore, a uniform metal composite hydroxide can be obtained.

[0126] After the above reaction, the resulting reaction precipitate is washed with water and then dried to obtain MCC. In this embodiment, nickel cobalt manganese hydroxide is obtained as MCC. If impurities from the mixed solution remain after washing the reaction precipitate with water alone, the reaction precipitate may be washed with weakly acidic water or an alkaline solution as needed. Examples of alkaline solutions include aqueous solutions containing sodium hydroxide or potassium hydroxide.

[0127] In the example above, nickel-cobalt-manganese composite hydroxide is produced, but nickel-cobalt-manganese composite oxide may also be prepared.

[0128] When producing metal composite oxides (MCCs), metal composite oxides can be produced by oxidizing metal composite hydroxides. For example, nickel-cobalt-manganese composite oxide can be prepared by oxidizing nickel-cobalt-manganese composite hydroxide. When preparing metal composite oxides, oxidation may be carried out at a temperature of 300-800°C for a range of 1-30 hours. The heating rate during oxidation is preferably 180°C / hour or higher, more preferably 200°C / hour or higher, and particularly preferably 250°C / hour or higher.

[0129] Furthermore, the reaction vessel may have a moderately oxidizing atmosphere. This oxidizing atmosphere may be an oxygen-containing atmosphere obtained by mixing an oxidizing gas with an inert gas, and an oxidizing agent may be present under an inert gas atmosphere. Having a moderately oxidizing atmosphere in the reaction vessel makes it easier to control the morphology of the metal composite oxide.

[0130] In an oxidizing atmosphere, oxygen and oxidizing agents only need to contain enough oxygen atoms to oxidize the transition metal element.

[0131] As oxidizing agents, peroxides such as hydrogen peroxide, peroxide salts such as permanganate, perchlorates, hypochlorites, nitric acid, halogens, and ozone can be used.

[0132] When the oxidizing atmosphere is an oxygen-containing atmosphere, the atmosphere inside the reaction vessel can be controlled by methods such as circulating oxidizing gas through the vessel or bubbling oxidizing gas into the mixture.

[0133] (CAM manufacturing process) The CAM of this embodiment can be obtained by a manufacturing method that includes the following manufacturing step (A) or manufacturing step (B), and a step of mixing the obtained calcined product with the coating material containing element M1, using a coating material raw material containing element M1. Manufacturing process (A): A process to obtain a mixture containing MCC, a coating material raw material containing element M1, and a lithium compound, and a process to obtain a calcined product by calcining the mixture. Manufacturing process (B): A process of first firing a mixture of MCC and a lithium compound to obtain a primary fired product, and a process of mixing the primary fired product with a coating material containing element M1 and firing it to obtain a fired product.

[0134] One embodiment of the manufacturing process for CAM includes a manufacturing step (A) and a step of mixing the obtained calcined product with a coating material containing element M1. One embodiment of the manufacturing process for CAM includes a manufacturing process (B) and a process of mixing the obtained calcined product with a coating material containing element M1.

[0135] [Manufacturing process (A)] (A process to obtain a mixture containing MCC, a coating material raw material containing element M1, and a lithium compound.) First, MCC, a coating material raw material containing element M1, and a lithium compound are mixed to obtain a mixture containing MCC, a coating material raw material containing element M1, and a lithium compound. For example, one method is to add and mix the coating material raw material to MCC, then mix in the lithium compound to obtain the mixture.

[0136] The mixing method for MCC and coating material raw materials can be either a dry method or a wet method, but the wet method is preferred. If the mixing of MCC and coating material raw materials is carried out by the wet method, a drying step may be performed in addition. By mixing MCC and coating material raw materials by the wet method, concentrated M1 regions are more easily formed at the grain boundaries of primary particles inside secondary particles.

[0137] Using a wet process improves the dispersibility of the coating material raw material within the secondary particles of CAM and prevents aggregation of the coating material raw material. In the wet process, the above effects can be enhanced by performing the mixing of MCC and the coating material raw material, stirring, and drying in the same process.

[0138] The coating material is a material containing at least one element M1 selected from the group consisting of Nb, Ta, B, Mo, W, La, and P.

[0139] When carried out by a wet process, the coating material raw material is preferably an additive solution containing a Li source, an element M1 source, and a solvent. Examples of element M1 sources include oxides, hydroxides, carbonates, nitrates, sulfates, halides, oxalates, alkoxides, or complexes of element M1.

[0140] Examples of Li sources include Li alkoxides, Li inorganic salts, and Li hydroxides.

[0141] Examples of Li-alkoxides include ethoxylithium and methoxylithium.

[0142] Examples of the Li inorganic salts include lithium nitrate, lithium sulfate, and lithium acetate. Examples of the Li hydroxides include lithium hydroxide and lithium hydroxide hydrate.

[0143] When the element M1 is Nb, examples of the Nb source include Nb alkoxide, Nb inorganic salt, Nb hydroxide, and Nb complex.

[0144] Examples of the Nb alkoxide include pentaethoxynb, pentamethoxynb, penta-i-propoxynb, penta-n-propoxynb, penta-i-butoxynb, penta-n-butoxynb, and penta-sec-butoxynb.

[0145] Examples of the Nb inorganic salt include niobium acetate and the like. A hydrate may be used as the niobium oxide.

[0146] Examples of the Nb hydroxide include niobium hydroxide.

[0147] Examples of the Nb complex include a peroxo complex of Nb (peroxoniobate complex, [Nb(O2)4] 3- ).

[0148] The additive solution containing the peroxo complex of Nb has an advantage that the amount of gas generation is less than that of the additive solution containing Nb alkoxide.

[0149] Examples of the method for preparing the additive solution containing the peroxo complex of Nb include a method of adding hydrogen peroxide solution and aqueous ammonia to Nb oxide or Nb hydroxide. The amounts of the hydrogen peroxide solution and the aqueous ammonia added may be appropriately adjusted so that a transparent solution (homogeneous solution) is obtained.

[0150] When the element M1 is Ta, an example of the Ta source is tantalum oxide.

[0151] If element M1 is B, then boron oxide can be considered a source of B.

[0152] If element M1 is Mo, then molybdenum oxide is a possible source of Mo.

[0153] If element M1 is W, then W sources include tungsten oxide and lithium tungstate.

[0154] If element M1 is La, then lanthanum oxide can be considered a source of La.

[0155] If element M1 is P, then possible sources of P include diammonium hydrogen phosphate and ammonium dihydrogen phosphate.

[0156] The type of solvent used in the additive solution is not particularly limited, but examples include alcohol, water, etc.

[0157] Examples of alcohols include methanol, ethanol, propanol, and butanol. When the added solution contains Nb alkoxide, the solvent is preferably anhydrous or dehydrated alcohol. On the other hand, when the added solution contains, for example, a Nb peroxo complex, the solvent is preferably water.

[0158] When mixing MCC and coating material raw materials, the mixing apparatus is not limited as long as uniform mixing is achieved, but it is preferable to use, for example, a Redigge mixer or a rolling fluidizer. These apparatuses can spray-mix the coating material raw materials while the MCC is flowing, and can also stir and dry them. For rolling fluidizers, the MP-01 manufactured by Powrec is a suitable choice.

[0159] MCC and coating material raw materials are used in proportions corresponding to the composition ratio of the composition formula (I) above.

[0160] As lithium compounds, one or more of the following can be used: lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium hydroxide hydrate, lithium oxide, lithium chloride, and lithium fluoride. Of these, lithium hydroxide, lithium hydroxide hydrate, and lithium carbonate, or both, are preferred.

[0161] The lithium compound and MCC are used in proportion to the composition ratio of the final product. The lithium compound and the MCC are used in proportions corresponding to the composition ratio of the composition formula (I) above. Furthermore, if Li is in excess (molar ratio greater than 1) in the final product CAM, the lithium compound is mixed in proportion to the metal element in the MCC so that the molar ratio of Li to MCC is greater than 1. This results in S Li and I Li The value of can be controlled within the range of this embodiment.

[0162] (A process of firing a mixture to obtain a fired product) Next, a calcined product is obtained by calcining a mixture containing MCC, coating material raw materials, and a lithium compound.

[0163] By firing the above mixture, the MCC and lithium compound react to grow primary particles, which then aggregate and sinter, forming secondary particles with grain boundaries. Element M1 is present at the grain boundaries of the primary particles, and regions of element M1 are formed.

[0164] For example, a lithium-nickel-cobalt-manganese composite oxide can be obtained by calcining a mixture of a nickel-cobalt-manganese composite compound and a lithium compound. Depending on the desired composition, dry air, an oxygen atmosphere, or an inert atmosphere can be used for calcination.

[0165] Specifically, the holding temperature during firing can be in the range of 600-1150°C, with 650-1050°C being preferred and 700-1000°C being more preferred. The holding time at the holding temperature can be 0.1-20 hours, with 0.5-10 hours being preferred. In addition, the atmosphere used for firing can be air, oxygen, nitrogen, argon, or a mixture of these gases.

[0166] The firing process may be carried out multiple times. For example, a mixture containing MCC, coating material raw materials, and a lithium compound may be subjected to primary firing, followed by a main firing at a higher temperature than the primary firing. The holding temperature and holding time during primary and main firing are within the ranges described in [Manufacturing Process (B)] below.

[0167] [Manufacturing process (B)] (A process of first calcining a mixture of MCC and a lithium compound to obtain a primary calcined product.) The MCC obtained in the (MCC manufacturing process) is mixed with a lithium compound to obtain a mixture of MCC and a lithium compound. As the lithium compound, the compounds listed in [Manufacturing Process (A)] can be used. The lithium compound and MCC are used in proportions corresponding to the composition ratio of the above composition formula (I).

[0168] Next, the mixture of MCC and lithium compound is subjected to primary calcination to obtain a primary calcined product. Specifically, the holding temperature for the primary firing can be in the range of 300°C to 750°C, preferably 400°C to 700°C, and more preferably 450°C to 680°C. The holding time at the primary firing temperature is typically between 0.1 hours and 20 hours, with a preference of between 0.5 hours and 10 hours. The heating rate to reach the holding temperature is typically between 50°C / hour and 400°C / hour, and the cooling rate from the holding temperature to room temperature is typically between 10°C / hour and 400°C / hour. The atmosphere for primary firing can be air, oxygen, nitrogen, argon, or a mixture thereof.

[0169] (A process in which the primary calcined product is mixed with the coating material containing element M1, and then calcined to obtain the calcined product.) The primary calcined material is mixed with a coating material raw material containing element M1, and then the main calcination is performed. This yields the calcined product (main calcined product). When mixing the primary calcined product and the coating material raw materials, either a dry or wet method may be used, but the wet method is preferred. When mixing the primary calcined product and the coating material raw materials using the wet method, a drying step may be carried out further. Examples of coating material raw materials and mixing equipment include the materials and mixing equipment listed in [Manufacturing Process (A)].

[0170] The primary calcined material is a secondary particle with grain boundaries formed when MCC and lithium compounds react, causing primary particles to aggregate and sinter. By mixing the primary calcined material with the coating material raw materials and performing the final calcination, element M1 diffuses into the grain boundaries, forming a concentrated region of element M1.

[0171] Specifically, the holding temperature during the final firing can be in the range of 600°C to 1150°C, preferably 650°C to 1050°C, and more preferably 700°C to 1000°C.

[0172] Furthermore, the holding time at the firing temperature is typically between 0.1 hours and 20 hours, with 0.5 hours and 10 hours being preferred. The heating rate to reach the holding temperature is usually between 50°C / hour and 400°C / hour, and the cooling rate from the holding temperature to room temperature is usually between 10°C / hour and 400°C / hour. In addition, the atmosphere used for firing can be air, oxygen, nitrogen, argon, or a mixture thereof.

[0173] (Optional grinding process) It is preferable to pulverize the calcined material obtained in manufacturing process (A) or manufacturing process (B). By pulverizing the calcined material, the material is pulverized starting from the large pores. As a result, a CAM with a low proportion of large pores can be obtained.

[0174] The calcined material may be pulverized, and the resulting pulverized material may be further calcined. Alternatively, the pulverized material may be dried. By calcining the material after grinding, foreign substances such as lithium carbonate that have formed on the surface of the ground material can be removed.

[0175] Examples of pulverizers used in crushing processes include mascolloider-type pulverizers.

[0176] The rotational speed of the crusher is preferably in the range of 500 rpm to 2000 rpm.

[0177] Through the above process, a fired product (final fired product) is obtained.

[0178] By using the calcined product obtained in manufacturing process (A) or manufacturing process (B), β and S of CAM can be used. Li and I Li The value can be controlled within the range described above.

[0179] [A process of mixing the calcined product with the coating material raw material containing element M1] Coated CAM is obtained by mixing the calcined material (or pulverized material if a pulverization process is performed) obtained by the above-described manufacturing process (A) or manufacturing process (B) with a coating material raw material containing element M1, and then heat-treating it as necessary. A wet method is preferred for mixing the calcined material and the coating material raw material. Specifically, the calcined material and the coating material raw material are mixed by spraying the coating material raw material onto the calcined material. The coating material raw material and equipment used in the coating process are those listed in [Manufacturing Process (A)]. A wet method using a rolling fluidizer is preferred as the coating method, and a material containing Nb is preferred as the coating material raw material.

[0180] When using a rolling fluidizer in the coating process, it is preferable to use a two-fluid spray nozzle that atomizes the coating material raw material with high-pressure air when adding the coating material raw material. To adjust α and β of CAM to the above range, it is preferable to control the flow rate of high-pressure air in the range of 10-80 NL / min.

[0181] The calcined material contains secondary particles formed by the aggregation of primary particles. By keeping the flow rate of high-pressure air below the above upper limit, the newly formed surfaces inside the secondary particles are less likely to be exposed when the secondary particles are crushed. By making it less likely for new surfaces to form inside the secondary particles where element M1 is absent, the values ​​of α and β of CAM can be controlled to be above the lower limit.

[0182] On the other hand, by increasing the flow rate of the high-pressure air above the lower limit mentioned above, the droplet diameter of the coating material becomes uniformly smaller, allowing droplets to adhere uniformly to the surface of the fired product, thus enabling the control of CAM's α to be above the lower limit.

[0183] Furthermore, by increasing the flow rate of the high-pressure air above the lower limit, the coating material raw material is less likely to penetrate excessively into the secondary particles in the fired product, and the β of CAM can be controlled to be below the upper limit. In addition, when the flow rate of the high-pressure air above the lower limit, the aggregation of secondary particles can be loosened, and when it is below the upper limit, the pulverization of secondary particles by crushing can be suppressed. As a result, (D 90 -D 10 ) / D 50 Furthermore, the BET specific surface area can be adjusted to the range of this embodiment.

[0184] The calcined product and the coating material raw materials can be mixed in proportions corresponding to the composition ratio of the above composition formula (I).

[0185] The coating material raw materials and the fired product may be mixed and then heat-treated. The heat treatment conditions are adjusted according to the type of coating material raw materials. Examples of heat treatment conditions include the heat treatment temperature and the heat treatment holding time.

[0186] For example, if the coating material contains Nb, it is preferable to heat-treat it at a temperature range of 200°C to 800°C for 4 to 10 hours. A heat treatment temperature within this range prevents the coating material from solid-solubilizing with the fired product. A heat treatment time within this range allows the coating material to sufficiently diffuse into the fired product.

[0187] In this specification, the heat treatment temperature refers to the temperature of the atmosphere inside the heating furnace and is the highest temperature at which the temperature is maintained during the heat treatment process.

[0188] CAM can be obtained by mixing the coating material raw materials and the fired product and heat-treating them under the heat treatment conditions described above.

[0189] CAM may be crushed and classified as appropriate.

[0190] By going through manufacturing process (A) or manufacturing process (B) and a process of mixing the obtained calcined product with a coating material raw material containing element M1, element M1 is present without bias in the interior or on the surface of the secondary particles of CAM, so that CAM can be obtained in which α and β are within the range of this embodiment.

[0191] <Lithium-ion secondary battery> A suitable positive electrode for a lithium secondary battery when using the CAM of this embodiment will be described. Hereinafter, the positive electrode for a lithium secondary battery may be referred to simply as the positive electrode. Furthermore, we will describe lithium secondary batteries that are suitable for use as a positive electrode.

[0192] A suitable example of a lithium secondary battery using the CAM of this embodiment includes a positive electrode and a negative electrode, a separator sandwiched between the positive electrode and the negative electrode, and an electrolyte placed between the positive electrode and the negative electrode.

[0193] Figure 1 is a schematic diagram showing an example of a lithium secondary battery. For example, a cylindrical lithium secondary battery 10 is manufactured as follows.

[0194] First, as shown in the partially enlarged view of Figure 1, a pair of strip-shaped separators 1, a strip-shaped positive electrode 2 having a positive electrode lead 21 at one end, and a strip-shaped negative electrode 3 having a negative electrode lead 31 at one end are stacked in the order of separator 1, positive electrode 2, separator 1, negative electrode 3, and then wound to form an electrode group 4.

[0195] The positive electrode 2, as an example, has a positive electrode active material layer 2a containing CAM and a positive electrode current collector 2b on which the positive electrode active material layer 2a is formed on one surface. Such a positive electrode 2 can be manufactured by first preparing a positive electrode mixture containing CAM, a conductive material, and a binder, and then supporting the positive electrode mixture on one surface of the positive electrode current collector 2b to form the positive electrode active material layer 2a.

[0196] The negative electrode 3 can be, as an example, an electrode in which a negative electrode mixture containing a negative electrode active material (not shown) is supported on a negative electrode current collector, or an electrode consisting of the negative electrode active material alone, and can be manufactured in the same manner as the positive electrode 2.

[0197] Next, the electrode group 4 and an insulator (not shown) are placed in the battery can 5, the bottom of the can is sealed, the electrode group 4 is impregnated with electrolyte 6, and the electrolyte is placed between the positive electrode 2 and the negative electrode 3. Furthermore, the top of the battery can 5 is sealed with a top insulator 7 and a sealing body 8 to manufacture the lithium secondary battery 10.

[0198] As for the shape of the electrode group 4, for example, a columnar shape can be given such that the cross-sectional shape when the electrode group 4 is cut perpendicular to the winding axis is a circle, an ellipse, a rectangle, or a rectangle with rounded corners.

[0199] Furthermore, the shape of the lithium secondary battery having such electrode group 4 can be one of those specified in IEC60086 or JIS C 8500, which are battery standards established by the International Electrotechnical Commission (IEC). For example, cylindrical or prismatic shapes can be used.

[0200] Furthermore, lithium secondary batteries are not limited to the wound configuration described above; they may also have a stacked configuration in which a stacked structure of positive electrode, separator, negative electrode, separator is repeatedly stacked. Examples of stacked lithium secondary batteries include so-called coin-type batteries, button-type batteries, or paper-type (or sheet-type) batteries.

[0201] Regarding the positive electrode, separator, negative electrode, and electrolyte solution constituting the lithium secondary battery, for example, the configurations, materials, and manufacturing methods described in

[0113] to

[0140] of WO2022 / 113904A1 can be used.

[0202] <All-solid-state lithium secondary battery> The CAM of the present embodiment can be used as the CAM of an all-solid-state lithium secondary battery.

[0203] FIG. 2 is a schematic diagram showing an example of an all-solid-state lithium secondary battery. The all-solid-state lithium secondary battery 1000 shown in FIG. 2 includes a laminate 100 having a positive electrode 110, a negative electrode 120, and a solid electrolyte layer 130, and an exterior body 200 that houses the laminate 100. Further, the all-solid-state lithium secondary battery 1000 may have a bipolar structure in which the CAM and the negative electrode active material are arranged on both sides of the current collector. As a specific example of the bipolar structure, for example, the structure described in JP-A-2004-95400 can be mentioned.

[0204] The positive electrode 110 has a positive electrode active material layer 111 and a positive electrode current collector 112. The positive electrode active material layer 111 contains the above-described CAM and solid electrolyte. Further, the positive electrode active material layer 111 may contain a conductive material and a binder.

[0205] The negative electrode 120 has a negative electrode active material layer 121 and a negative electrode current collector 122. The negative electrode active material layer 121 contains a negative electrode active material. Further, the negative electrode active material layer 121 may contain a solid electrolyte and a conductive material.

[0206] The laminate 100 may have an external terminal 113 connected to the positive electrode current collector 112 and an external terminal 123 connected to the negative electrode current collector 122. In addition, the all-solid-state lithium secondary battery 1000 may have a separator between the positive electrode 110 and the negative electrode 120.

[0207] The all-solid-state lithium secondary battery 1000 further includes an insulator (not shown) that insulates the laminate 100 and the exterior body 200, and a sealing body (not shown) that seals the opening 200a of the exterior body 200.

[0208] For the outer package 200, a container formed of a highly corrosion-resistant metal material such as aluminum, stainless steel, or nickel-plated steel can be used. Also, as the outer package 200, a container obtained by processing a laminate film having corrosion-resistant processing on at least one surface into a bag shape can be used.

[0209] Examples of the shape of the all-solid-state lithium secondary battery 1000 include coin type, button type, paper type (or sheet type), cylindrical type, square type, or laminate type (pouch type).

[0210] As an example, the all-solid-state lithium secondary battery 1000 is illustrated in a form having one laminate 100, but the present embodiment is not limited thereto. The all-solid-state lithium secondary battery 1000 may have a configuration in which the laminate 100 is used as a unit cell and a plurality of unit cells (laminates 100) are sealed inside the outer package 200.

[0211] For the all-solid-state lithium secondary battery, for example, the configurations, materials, and manufacturing methods described in

[0151] to

[0181] of WO2022 / 113904A1 can be used.

[0212] In the lithium secondary battery having the above-described configuration, since the CAM of the present embodiment is used, a lithium secondary battery capable of maintaining the discharge capacity even when charging and discharging are repeated can be provided.

[0213] Also, since the positive electrode having the above-described configuration has the CAM of the above-described configuration, the discharge capacity can be maintained even when charging and discharging of the lithium secondary battery are repeated.

[0214] Furthermore, since the lithium secondary battery having the above-described configuration has the above-described positive electrode, it becomes a secondary battery capable of maintaining the discharge capacity even when charging and discharging are repeated.

[0215] Preferred embodiments of the present invention have been described above with reference to the attached drawings, but the present invention is not limited to these examples. The shapes and combinations of the constituent members shown in the above examples are merely examples, and can be modified in various ways based on design requirements, etc., without departing from the spirit of the present invention.

[0216] Furthermore, the present invention may encompass the following embodiments.

[21] A CAM having a layered structure, comprising secondary particles which are aggregates of primary particles, comprising the elements M1 and M2, and satisfying the following (1) and (2). (1) The above α is 0.70-0.96. (2) The above β is 0.08-0.18.

[22] The CAM according to

[21] , having a concentrated region of element M1 at the grain boundaries between primary particles in the cross-section of the secondary particles as observed by transmission electron microscopy-energy dispersive X-ray spectroscopy.

[23] The CAM according to

[21] or

[22] , wherein the content of Mn is 0.03-0.7 mol per 1 mol of the total amount of the element M2.

[24] The CAM represented by the above compositional formula (I) as described in any one of

[21] to

[23] .

[25] The above S Li The CAM is one of the following, as described in 1.6-3.4,

[21] -

[24] .

[26] The above I Li The CAM is 14-40, as listed in any one of

[21] -

[25] .

[27] BET specific surface area is 0.4-1.5m 2 The CAM listed in any one of

[21] to

[26] is / g.

[28] D 10 , D 50 and D 90 A CAM according to any one of

[21] to

[27] that satisfies (II)-2 above.

[29] A CAM described in any one of

[21] to

[28] for solid lithium secondary batteries. An electrode for a lithium secondary battery containing the CAM described in any one of

[30] ,

[21] , or

[29] . A lithium secondary battery comprising the electrode for a lithium secondary battery described in

[31]

[30] .

Example

[0217] The present invention will be described below with reference to examples, but the present invention is not limited to these examples.

[0218] <Measurement of α and β> XPS analysis of the CAM was performed by the methods described in the above [Measurement method of α] and [Measurement method of β] to measure α and β.

[0219] <S Li and I Li Measurement> XPS analysis of the CAM was performed by the methods described in the above [Measurement method of α] and [Measurement method of β] to measure S Li and I Li was measured.

[0220] <Method for confirming the concentration part> The cross-section of the CAM was obtained by the method described in the above [Method for obtaining cross-section], TEM analysis was performed, and confirmation was carried out according to the method described in [Method for confirming the concentration part].

[0221] <Composition analysis of CAM> Composition analysis of the CAM was performed by the method described in the above [Composition analysis].

[0222] [Measurement of BET specific surface area]​​​​​​​​​​​​​​​​​​​​​​​The method described in [Method for confirming layered structure] above was used to confirm whether or not the CAM had a layered structure.

[0225] A solid lithium-ion secondary battery was manufactured using the method described in [Measurement of Initial Discharge Capacity] above. A charge-discharge test was then performed on the manufactured solid lithium-ion secondary battery using the method described in <Charge-Discharge Test> above, and the battery performance was evaluated based on the discharge capacity value.

[0226] <Example 1> (Manufacturing of CAM1) After adding water to a reaction vessel equipped with a stirrer and overflow pipe, an aqueous sodium hydroxide solution was added, and the liquid temperature was maintained at 50°C. Mixed raw material solution 1 was prepared by mixing nickel sulfate aqueous solution, cobalt sulfate aqueous solution, and manganese sulfate aqueous solution in a ratio of Ni, Co, and Mn of 0.6:0.2:0.2.

[0227] Next, mixed raw material solution 1 and ammonium sulfate aqueous solution were continuously added to the reaction vessel under stirring conditions. Sodium hydroxide aqueous solution was added dropwise as needed to obtain a reaction precipitate under conditions where the pH of the mixed solution in the reaction vessel was 12.1 (when the temperature of the aqueous solution was 40°C).

[0228] After washing the resulting reaction precipitate, it was dehydrated using a centrifuge, and then washed, dehydrated, isolated, and dried at 105°C for 20 hours to obtain MCC1, a nickel-cobalt-manganese composite hydroxide.

[0229] (Preparation process for coating material raw material 1) 133 g of 30% by mass H2O2 water, 151 g of pure water, and 6.8 g of niobium oxide hydrate Nb2O5·3H2O (72% by mass content) were mixed. Next, 13 g of 28% by mass ammonia water was added and stirred. Furthermore, 1.9 g of LiOH·H2O was added to obtain coating material raw material 1 containing Nb.

[0230] Using a rolling fluidizer (Pawrec Co., Ltd., MP-01), coating material 1 was sprayed onto MCC1 at a ratio of Nb / (Ni+Co+Mn)=1mol%.

[0231] Subsequently, lithium hydroxide monohydrate powder was weighed and mixed in a ratio of Li / (Ni+Co+Mn)=1.03, and the mixture was subjected to primary calcination at 650°C for 5 hours under an oxygen atmosphere.

[0232] Next, the material was fired at 840°C in an oxygen atmosphere for 5 hours to obtain the fired product 1.

[0233] The resulting calcined product 1 was crushed using a mass colloider type crusher to obtain crushed product 1.

[0234] The pulverized material 1 was dried at 120°C for 10 hours under a vacuum atmosphere. Then, using the rolling fluidization apparatus described above, the coating material raw material 1 was sprayed onto the pulverized material 1 at a ratio of Nb / (Ni+Co+Mn) = 0.61 mol%. At this time, the flow rate of high-pressure air in the two-fluid spray nozzle of the rolling fluidization apparatus was 30 NL / min.

[0235] (Heat treatment process) CAM1 was obtained by heat-treating 1, which was sprayed with coating material raw material 1, at 200°C for 5 hours under an oxygen atmosphere.

[0236] [CAM1 Evaluation] The α value of CAM1 was 0.79, and the β value was 0.13. The BET specific surface area was 0.5 m². 2 / g was (D 90 -D 10 ) / D 50 The ratio was 0.56. The Mn content relative to 1 mol of the total amount of element M2 was 0.20 mol. The discharge capacity of the solid lithium secondary battery CAM1 was 176 mAh / g. CAM1 had a layered structure. In the composition formula (I) of CAM1, x, a, b, c, d, e, δ, element M1, element M2, element Z, S Li and I Li The presence or absence of a concentrated portion is indicated in Table 1. The same Table 1 is used for subsequent examples and comparative examples.

[0237] <Example 2> (Manufacturing of CAM2) MCC1 and lithium hydroxide monohydrate powder were weighed and mixed in a molar ratio of Li / (Ni+Co+Mn)=1.03. Then, the mixture was subjected to primary calcination at 650°C for 5 hours under an oxygen atmosphere to obtain primary calcined product 2.

[0238] Using a rolling fluid apparatus similar to that in Example 1, coating material 1 was sprayed onto the primary calcined product 2 at a ratio of Nb / (Ni+Co+Mn)=1mol%, and then the product was calcined at 860°C for 5 hours under an oxygen atmosphere to obtain the final calcined product 2.

[0239] The resulting calcined product 2 was crushed using a mass colloider type crusher to obtain crushed product 2.

[0240] The pulverized material 2 was dried in a vacuum atmosphere at 120°C for 10 hours. Subsequently, the coating material raw material 1 was sprayed onto the pulverized material 2 using the rolling fluidization apparatus at a ratio of Nb / (Ni+Co+Mn) = 0.48 mol%. At this time, the flow rate of high-pressure air in the two-fluid spray nozzle of the rolling fluidization apparatus was 30 NL / min.

[0241] (Heat treatment process) CAM2 was obtained by heat-treating 2, which was sprayed with coating material raw material 1, at 200°C for 5 hours under an oxygen atmosphere.

[0242] [CAM2 Evaluation] The α value of CAM2 was 0.74, and the β value was 0.09. The BET specific surface area was 0.4 m². 2 / g was (D 90 -D 10 ) / D 50 The ratio was 0.59. The Mn content relative to the total amount of element M2 was 0.19 mol. The discharge capacity of the CAM2 solid lithium secondary battery was 179 mAh / g. CAM2 had a layered structure.

[0243] <Example 3> (Manufacturing of CAM3) (Preparation process for coating material raw material 2) 3300g of pure water and 100g of tungsten oxide (WO3) were mixed. Furthermore, 110g of LiOH·H2O was added to obtain coating material 2 containing W.

[0244] Using a rolling fluidizer similar to that in Example 1, coating material 2 was sprayed onto MCC1 at a ratio of W / (Ni+Co+Mn)=1mol%.

[0245] Furthermore, lithium hydroxide monohydrate powder was weighed and mixed in a ratio of Li / (Ni+Co+Mn)=1.03, and then primary calcination was performed at 650°C for 5 hours under an oxygen atmosphere. Subsequently, final calcination was performed at 840°C for 5 hours under an oxygen atmosphere to obtain final calcined product 3.

[0246] The resulting calcined product 3 was crushed using a mass colloider type crusher to obtain crushed product 3.

[0247] The pulverized material 3 was dried at 120°C for 10 hours under a vacuum atmosphere. Then, using the rolling fluidization apparatus described above, the coating material raw material 1 was sprayed onto the pulverized material 3 at a ratio of Nb / (Ni+Co+Mn) = 0.99 mol%. At this time, the flow rate of high-pressure air in the two-fluid spray nozzle of the rolling fluidization apparatus was 30 NL / min.

[0248] (Heat treatment process) CAM3 was obtained by heat-treating the pulverized material 3, to which coating material raw material 1 had been sprayed, at 200°C for 5 hours under an oxygen atmosphere.

[0249] [CAM3 Review] The α value of CAM3 was 0.87, and the β value was 0.15. The BET specific surface area was 0.4 m². 2 / g was (D 90 -D 10 ) / D 50 The ratio was 0.62. The Mn content relative to the total amount of element M2 was 0.20 mol. The discharge capacity of the CAM3 solid lithium secondary battery was 175 mAh / g. CAM3 had a layered structure.

[0250] <Comparative Example 1> (Manufacturing of CAM-C1) MCC1 and lithium hydroxide monohydrate powder were weighed and mixed in a molar ratio of Li / (Ni+Co+Mn)=1.03. Then, the mixture was subjected to primary calcination at 650°C for 5 hours under an oxygen atmosphere to obtain primary calcined product C1.

[0251] Using a rolling fluidization apparatus similar to that in Example 1, coating material 1 was sprayed onto the primary calcined product C1 at a ratio of Nb / (Ni+Co+Mn)=1mol%. Then, the product was calcined at 860°C for 5 hours under an oxygen atmosphere to obtain the final calcined product C1.

[0252] The resulting calcined product C1 was pulverized using a mass colloider type pulverizer to obtain CAM-C1.

[0253] [CAM-C1 Evaluation] The α value for CAM-C1 was 0.20, and the β value was 0.04. The BET specific surface area was 0.4 m². 2 / g was (D 90 -D 10 ) / D 50 The value was 0.57. The Mn content relative to the total amount of element M2 was 0.19 mol. The discharge capacity of the CAM-C1 solid lithium secondary battery was 161 mAh / g. CAM-C1 had a layered structure.

[0254] <Comparative Example 2> (Manufacturing of CAM-C2) Using a rolling fluidizer similar to that in Example 1, coating material 1 was sprayed onto MCC1 at a ratio of Nb / (Ni+Co+Mn)=1 mol%. Furthermore, lithium hydroxide monohydrate powder was weighed and mixed at a molar ratio of Li / (Ni+Co+Mn)=1.03, and then primary calcination was performed at 650°C for 5 hours under an oxygen atmosphere. Next, the material was calcined at 840°C for 5 hours under an oxygen atmosphere to obtain the calcined product C2.

[0255] The resulting calcined material was pulverized using a mass colloider type pulverizer to obtain CAM-C2.

[0256] [CAM-C2 Evaluation] The α value for CAM-C2 was 0.08, and the β value was 0.02. The BET specific surface area was 0.7 m². 2 / g was (D 90 -D 10 ) / D 50 The ratio was 0.55. The Mn content relative to the total amount of element M2 was 0.20 mol. The discharge capacity of the CAM-C2 solid lithium secondary battery was 152 mAh / g. CAM-C2 had a layered structure.

[0257] <Comparative Example 3> (Manufacturing of CAM-C3) MCC1 and lithium hydroxide monohydrate powder were weighed and mixed in a molar ratio of Li / (Ni+Co+Mn)=1.03, and then subjected to primary calcination at 650°C for 5 hours under an oxygen atmosphere. Subsequently, the mixture was subjected to final calcination at 840°C for 5 hours under an oxygen atmosphere to obtain the final calcined product C3.

[0258] The obtained calcined product C3 was crushed using a mass colloider type pulverizer to obtain pulverized product C3.

[0259] The pulverized material C3 was dried in a vacuum atmosphere at 120°C for 10 hours. Using a rolling fluidization apparatus similar to that in Example 1, the coating material raw material 1 was sprayed onto the pulverized material C3 at a ratio of Nb / (Ni+Co+Mn) = 1.5 mol%. At this time, the flow rate of high-pressure air in the two-fluid spray nozzle of the rolling fluidization apparatus was 100 NL / min.

[0260] (Heat treatment process) The pulverized material C3, to which coating material raw material 1 was sprayed, was heat-treated at 200°C for 5 hours under an oxygen atmosphere to obtain CAM-C3.

[0261] [CAM-C3 Review] The α value for CAM-C3 was 0.42, and the β value was 0.05. The BET specific surface area was 2.4 m². 2 / g was (D 90 -D 10 ) / D 50 The ratio was 0.62. The Mn content relative to the total amount of element M2 was 0.19 mol. The discharge capacity of the CAM-C3 solid lithium secondary battery was 171 mAh / g. CAM-C3 had a layered structure.

[0262] <Comparative Example 4> (Manufacturing of CAM-C4) MCC1 and lithium hydroxide monohydrate powder were weighed and mixed in a molar ratio of Li / (Ni+Co+Mn)=1.03, and then subjected to primary calcination at 650°C for 5 hours under an oxygen atmosphere. Subsequently, the mixture was subjected to final calcination at 840°C for 5 hours under an oxygen atmosphere to obtain the final calcined product C4.

[0263] The obtained calcined product C4 was crushed using a mass colloider type crusher to obtain crushed product C4.

[0264] The pulverized material C4 was dried in a vacuum atmosphere at 120°C for 10 hours. Using a rolling fluidization apparatus similar to that in Example 1, coating material raw material 1 was sprayed onto the pulverized material C4 at a ratio of Nb / (Ni+Co+Mn) = 0.80 mol%, thereby obtaining CAM-C4. At this time, the amount of high-pressure air in the two-fluid apparatus was 30 NL / min.

[0265] [CAM-C4 Review] The α value for CAM-C4 was 0.64, and the β value was 0.07. The BET specific surface area was 1.0 m². 2 / g was (D 90 -D 10 ) / D 50 The ratio was 0.68. The Mn content relative to the total amount of element M2 was 0.22 mol. The discharge capacity of the CAM-C4 solid lithium secondary battery was 171 mAh / g. CAM-C4 had a layered structure.

[0266] Table 1 below shows the physical properties and composition of Examples 1-3 and Comparative Examples 1-4.

[0267] [Table 1]

[0268] Examples 1 to 3, manufactured by a method including manufacturing process (A) or manufacturing process (B) and a step of mixing the obtained calcined product with the coating material raw material, showed that α and β of CAM satisfied the scope of the present invention, and elements M1 and M2 were present in specific ratios on the surface and inside the secondary particles. Using such CAM, it was confirmed that the initial discharge capacity of the lithium secondary battery was 172 mAh / g or higher.

[0269] Comparative Examples 1 and 2, which were manufactured without performing manufacturing process (A) or manufacturing process (B), and Comparative Examples 3 and 4, which were manufactured without mixing the calcined product and the coating material raw material, did not satisfy the scope of the present invention for CAM α and β. It was confirmed that using such CAMs resulted in an initial discharge capacity of approximately 150-170 mAh / g for the lithium secondary battery. [Explanation of Symbols]

[0270] 1: Separator, 2: Positive electrode, 2a: Positive electrode active material layer, 2b: Positive electrode current collector layer, 3: Negative electrode, 4: Electrode group, 5: Battery can, 6: Electrolyte, 7: Top insulator, 8: Sealing body, 10: Lithium secondary battery, 21: Positive electrode lead, 31: Negative electrode lead, 100: Laminate, 110: Positive electrode, 111: Positive electrode active material layer, 112: Positive electrode current collector, 113: External terminal, 120: Negative electrode, 121: Negative electrode active material layer, 122: Negative electrode current collector, 123: External terminal, 130: Solid electrolyte layer, 200: Outer casing, 200a: Opening, 1000: All-solid-state lithium secondary battery

Claims

1. A positive electrode active material for a lithium secondary battery, comprising secondary particles which are aggregates of primary particles and having a layered structure, Containing elements M1 and M2, The element M1 is Nb, or the element M1 is Nb and W. The element M2 is at least one element selected from the group consisting of Ni, Co, and Mn. A positive electrode active material for lithium secondary batteries that satisfies the following conditions (1) and (2). (1) The ratio α, which is the ratio of the atomic concentration (atomic%) of element M1 present on the surface of the secondary particle to the total amount of atomic concentration (atomic%) of element M2 present on the surface of the secondary particle, obtained by X-ray photoelectron spectroscopy (XPS) analysis, is 0.6 or more and 1 or less. (2) The ratio β, which is the ratio of the atomic concentration (atomic%) of element M1 present inside the secondary particle to the total amount of atomic concentration (atomic%) of element M2 present inside the secondary particle, obtained by the X-ray photoelectron spectroscopy (XPS) analysis, is 0.08 or more and 0.20 or less.

2. The positive electrode active material for a lithium secondary battery according to claim 1, wherein the grain boundaries of the primary particles in the cross-section of the secondary particles observed by transmission electron microscopy-energy dispersive X-ray spectroscopy have a concentration of element M1.

3. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the content of Mn is 0.03 mol or more relative to 1 mol of the total amount of element M2.

4. A positive electrode active material for a lithium secondary battery according to claim 1 or 2, represented by the following compositional formula (I). Li ｘ (Ni ａ Co ｂ Mn ｃ Z ｄ M1 ｅ ) O δ (I) (The composition formula (I) satisfies 0.98 ≤ x ≤ 1.80, 0.3 < a ≤ 1, 0 ≤ b ≤ 0.3, 0.03 ≤ c ≤ 0.7, 0 ≤ d ≤ 0.05, 0 < e ≤ 0.05, a + b + c + d + e = 1, and 2 ≤ δ < 3, where Z is at least one element selected from the group consisting of Al, Zr, and Ti, and M1 is Nb, or M1 is Nb and W.)

5. S is the ratio of the atomic concentration of Li present on the surface of the secondary particle to the atomic concentration of element M1 present on the surface of the secondary particle, obtained by the aforementioned X-ray photoelectron spectroscopy (XPS) analysis. Ｌｉ The positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein is 1 or more and 4 or less.

6. I, which is the ratio of the atomic concentration of Li present inside the secondary particles to the atomic concentration of the element M1 present inside the secondary particles, obtained by the X-ray photoelectron spectroscopy (XPS) analysis Ｌｉ is from 10 to 50, and is the positive electrode active material for a lithium secondary battery according to claim 1 or 2.

7. BET specific surface area is 0.2 m² ２ / g or more 2m ２ A positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the amount is less than or equal to / g.

8. D １０ , D ５０ and D ９０ A positive electrode active material for a lithium secondary battery according to claim 1 or 2, wherein the following (II) is satisfied. (0) ９０ -0 １０ ( / D) ５０ ≦1.0 (II) (D １０ D is the 10% cumulative volume particle size of the positive electrode active material for the lithium secondary battery. ５０ This is the 50% cumulative volume particle size of the positive electrode active material for the lithium secondary battery, and D ９０ This represents the 90% cumulative volume particle size of the positive electrode active material for the lithium secondary battery.

9. The positive electrode active material for a lithium secondary battery according to claim 1 or 2, which is for use in a solid lithium secondary battery.

10. An electrode for a lithium secondary battery comprising the positive electrode active material for a lithium secondary battery according to claim 1 or 2.

11. A lithium secondary battery comprising an electrode for a lithium secondary battery as described in claim 10.

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