Precursor of positive electrode active material

Abstract

A precursor of a positive electrode active material, wherein the precursor is particles of a nickel-cobalt-manganese composite hydroxide, and the precursor has a peak A and a peak B in which a peak attributed to a (100) plane of a space group R3-m is split into two in XRD analysis.

Description

Technical Field

[0001] This invention relates to precursors of positive electrode active materials. Background Technology

[0002] Various technologies have been proposed for positive electrode active materials disclosed in Japanese Patent Application Publication No. 2021-24764 and Japanese Patent Application Publication No. 2014-139119. Summary of the Invention

[0003] In the past, various positive electrode active materials have been proposed in order to obtain positive electrodes with high battery characteristics such as high cycle performance and high output performance.

[0004] For example, Japanese Patent Application Publication No. 2021-24764 discloses a nickel composite hydroxide in which, in a micropore distribution determination based on nitrogen adsorption, the average diameter of the micropores is 50 Å or more and 60 Å or less, and the integral intensity ratio of diffraction peaks appearing in the range of 2θ = 51.9 ± 1.0° to diffraction peaks appearing in the range of 2θ = 19.1 ± 1.0° is 0.40 or more and 0.50 or less. In the composition of the nickel composite hydroxide of Japanese Patent Application Publication No. 2021-24764, the molar ratio of Ni:Co:Mn:M is expressed as 1-xyz:x:y:z. 0 < x ≤ 0.15, 0 < y ≤ 0.15, 0 ≤ z ≤ 0.05, and M refers to one or more additive elements selected from the group consisting of Al, Fe, Ti, and Zr.

[0005] The nickel composite hydroxide described in Japanese Patent Application Publication No. 2021-24764 is a precursor for positive electrode active materials, which can be produced by calcining with lithium compounds. However, the positive electrode active material obtained from the nickel composite hydroxide described in Japanese Patent Application Publication No. 2021-24764 has room for improvement in terms of capacity retention. This is because repeated charging and discharging causes alternating cation mixing of lithium ions and other metal ions within the positive electrode active material, leading to a decrease in capacity.

[0006] This invention was made in view of the above-mentioned actual situation, and its main objective is to provide a precursor for a positive electrode active material that can produce a positive electrode active material with excellent capacity retention. Specifically, this invention includes the following methods.

[0007] <1>

[0008] A precursor, which is a precursor of a positive electrode active material, wherein the precursor is a particle of nickel cobalt manganese composite hydroxide, and the precursor has a peak belonging to the (100) plane of space group R3-m split into two peaks A and B in XRD analysis.

[0009] <2>

[0010] According to the precursor described in <1>, wherein the angle difference C between the diffraction angles of the peaks of the above-mentioned peaks A and B is greater than 0.31° and less than 0.68°, the integral intensity I of the above-mentioned peak B is obtained by fitting the above-mentioned peaks A and B based on the Gaussian function and the Lorentz function. B The integral intensity I relative to the above peak A A The integral intensity I of peak B above B The total ratio D (the following formula) is greater than 0 and less than 0.63.

[0011] Ratio D=I B / (I A +I B )

[0012] According to the present invention, a precursor of a positive electrode active material that can produce a positive electrode active material with excellent capacity retention can be provided. Attached Figure Description

[0013] Hereinafter, the features, advantages, and technical and industrial significance of exemplary embodiments of the present invention will be described with reference to the accompanying drawings, wherein the same symbols denote the same elements.

[0014] Figure 1 This is an example of the XRD diffraction pattern obtained by XRD analysis of the precursor of the present invention (the precursor of Example 4).

[0015] Figure 2 It is Figure 1 The enlarged view of the area enclosed by the dashed quadrilateral.

[0016] Figure 3 Yes Figure 2 The image is obtained by fitting the XRD diffraction pattern with Gaussian and Lorentz functions. Detailed Implementation

[0017] The embodiments of the present invention will be described below. It should be noted that matters necessary for the implementation of the present invention, other than those specifically mentioned in this specification, can be understood as design considerations for those skilled in the art based on prior art. For example, matters necessary for the implementation of the present invention, other than those specifically mentioned in this specification, include the general structure and manufacturing process of positive electrode active materials and their precursors that do not impart features to the present invention. The present invention can be implemented based on the disclosures in this specification and common technical knowledge in the art.

[0018] In this invention, a precursor is provided, which is a precursor of a positive electrode active material, wherein the precursor is a particle of nickel-cobalt-manganese composite hydroxide. In XRD analysis, the precursor exhibits a peak belonging to the (100) plane of space group R3-m that splits into two peaks, A and B.

[0019] An example of the XRD diffraction pattern obtained by XRD (X-ray diffraction) analysis of the precursor of the present invention (the precursor of Example 4) is shown below. Figure 1 .in addition, Figure 2 It is Figure 1 The enlarged view of the area enclosed by the dashed quadrilateral. Figure 1 and Figure 2 Within the area enclosed by the dashed quadrilateral, there exists a peak belonging to the (100) surface of the space group R3-m. Figure 1 and Figure 2 It can be seen that peak splitting was confirmed in the precursor of the present invention within the area enclosed by the dashed quadrilateral. That is, the precursor of the present invention has a peak A and a peak B that split from the peak of the (100) surface belonging to the space group R3-m.

[0020] Of the two peaks, peak A, with a relatively small diffraction angle (2θ), originates from a region with a relatively high proportion of nickel (Ni) and a relatively low proportion of manganese (Mn) (Mn-poor region). On the other hand, peak B, with a relatively large diffraction angle (2θ), originates from a region with a relatively high proportion of manganese and a relatively low proportion of nickel (Mn-rich region).

[0021] That is, the precursor of the positive electrode active material of the present invention is nickel-cobalt-manganese composite hydroxide particles having Mn-poor and Mn-rich regions as described above. In addition, the precursor of the present invention has a peak belonging to space group R3-m, and therefore has a structure belonging to R3-m (layered rock salt structure).

[0022] When nickel-cobalt-manganese composite hydroxides and lithium compounds are calcined, lithium-nickel-cobalt-manganese composite oxides, which are positive electrode active materials, can be obtained. It is known that during repeated charge-discharge cycles, alternating cation mixing of lithium ions and other metal ions such as nickel occurs within this positive electrode active material, leading to a decrease in capacity. This is because, in lithium-nickel-cobalt-manganese composite oxides with a layered structure belonging to space group R3-m, nickel exists in a divalent state (Ni...). 2+ When present, nickel has an ionic radius close to that of lithium, thus increasing the proportion of nickel entering lithium sites. Divalent nickel (Ni 2+ It is not produced when nickel is present alone, but rather when manganese (Mn) is in the tetravalent state. 4+ It is generated when they coexist.

[0023] As described above, the precursor of the positive electrode active material of the present invention is a nickel-cobalt-manganese composite hydroxide particle, which has a Mn-depleted region and a Mn-rich region. In the Mn-depleted region, the composition ratio of nickel (Ni) is relatively high and the composition ratio of manganese (Mn) is relatively low. In the Mn-rich region, the composition ratio of manganese is relatively high and the composition ratio of nickel is relatively low. In the precursor of the present invention, in the Mn-depleted region, nickel (Ni) exists in a trivalent state. 3+The proportion of nickel (Ni) increases, and nickel exists in a divalent state. 2+ The proportion of nickel cations decreases, thus suppressing nickel cation mixing. Furthermore, in Mn-rich regions, the proportion of nickel in contact with manganese is relatively lower, leading to a higher proportion of nickel (Ni) existing in a divalent state. 2+ The proportion of nickel cations decreases, thus suppressing nickel cation mixing.

[0024] As described above, by using the precursor of the present invention, a positive electrode active material in which cation mixing is suppressed can be obtained. That is, according to the present invention, a positive electrode active material with excellent capacity retention can be provided.

[0025] The precursor of this invention is a nickel-cobalt-manganese composite hydroxide particle.

[0026] In this invention, the particles can be primary particles or secondary particles formed by the aggregation of multiple primary particles. The shape of the particles is not particularly limited; for example, approximately spherical or approximately elliptical shapes are possible. The size of the particles is not particularly limited. The size of the particles can be determined, for example, by measuring the cross-sectional dimensions of multiple particles in TEM (Transmission Electron Microscope) or SEM (Scanning Electron Microscope) images and calculating their average value.

[0027] Furthermore, in this invention, the nickel-cobalt-manganese composite hydroxide is a composite hydroxide containing nickel (Ni), cobalt (Co), and manganese (Mn) as essential metal species. Additionally, in this invention, the nickel-cobalt-manganese composite hydroxide may contain other metal species besides nickel, cobalt, and manganese. These other metal species may be at least one selected from the group consisting of Zr, Mo, Mg, Ca, Na, Fe, Cr, Zn, Si, Sn, and Ag. The molar ratio (Ni / NiCoMn ratio) of the nickel-cobalt-manganese composite hydroxide is not particularly limited. The molar ratio of the nickel-cobalt-manganese composite hydroxide may be as follows: Ni / NiCoMn may be 0.5 or more and less than 1.0; Co / NiCoMn may be greater than 0 and less than 0.3; and Mn / NiCoMn may be greater than 0 and less than 0.3.

[0028] XRD analysis can be performed, for example, by powder XRD determination using a known XRD analysis apparatus such as Rigaku SmartLab II. Specific analytical conditions can be listed below, for example.

[0029] [XRD Analysis Conditions]

[0030] • Analysis method: Wide-angle method

[0031] • Measurement angle: 10°~120°

[0032] • Tube ball: Cu

[0033] Optical system: Kα

[0034] Voltage: 45kV

[0035] Current: 200mA

[0036] • Determination method: Continuous method

[0037] • Step size: 0.02°

[0038] • Scanning speed: 2° / minute

[0039] ·IS: 1 / 2

[0040] RS: 20mm

[0041] • Detection mode: One-dimensional

[0042] In the XRD analysis of the precursor of this invention, the splitting patterns of peaks A and B are not particularly limited.

[0043] For example, the angle difference C between the peaks of the (100) plane belonging to the space group R3-m splitting into two peaks, A and B, can be greater than 0.31° and less than 0.68°.

[0044] The peaks belonging to the (100) plane of space group R3-m can be peaks with diffraction angles (2θ) in the range of 33.30 ± 2.00°. Here, the diffraction angle (2θ) at the peak of peak A is... A The diffraction angle (2θ) at the peak of peak B. B The following calculation is performed. The XRD pattern obtained through XRD analysis is processed using a polynomial approximation. The one-dimensional data is differentiated, and the points intersecting with 0 are taken as peaks (the peaks of peak A and peak B). Then, this diffraction angle is taken as the diffraction angle of each peak (2θ). A 2θ B ).

[0045] The diffraction angle at the peak of peak A (2θ) A The diffraction angle (2θ) at the peak of peak B. B The angular difference C (°, degrees) is calculated using the following formula.

[0046] C=2θ B -2θ A

[0047] Furthermore, the integral intensity I of peak B is obtained by fitting peaks A and B based on Gaussian and Lorentz functions. B Integral intensity I relative to peak A A The integral intensity I of peak BB The total ratio D (as shown in the formula below) can be greater than 0 and less than 0.63. The ratio D can be greater than 0.06 and less than 0.63.

[0048] Ratio D=I B / (I A +I B )

[0049] The integral intensity I of peak A is obtained by fitting based on Gaussian and Lorentz functions. A The integral intensity I of peak B B It can be calculated as follows. It should be noted that the integral intensity I of peak A, obtained by fitting based on the Gaussian and Lorentz functions, is... A Sometimes simply referred to as "the integral intensity I of peak A" A The integral intensity I of peak B is obtained by fitting based on Gaussian and Lorentz functions. B Sometimes simply referred to as "the integral intensity I of peak B" B ".

[0050] First, the XRD diffraction pattern obtained from XRD analysis is processed using a polynomial approximation to remove background noise. The one-dimensional data is then differentiated, and the points intersecting with 0 are taken as peaks (the peaks of peak A and peak B). Next, the composite function of the Gaussian and Lorentz functions, expressed by the following formula, is used as a peak. Peaks A and B are fitted together, and the integral intensity (I) of each peak is calculated. A I B In other words, calculate the area of ​​the integral intensity.

[0051] Composite function = (Gaussian function) α + (Lorentz function) (1-α)

[0052] In the above formula, α represents the mixing ratio of the function, which can be set appropriately.

[0053] Figure 3 The middle shows the Figure 2 The image was obtained by fitting the XRD diffraction pattern with Gaussian and Lorentz functions. Figure 3 In this context, the integral intensity (Ii) can be calculated based on the area formed by the curves, which are displayed as a "global fit". A I B ).

[0054] The integral intensity I of peak A, calculated as described above, can be used. A The integral intensity I of peak B B Calculate the integral intensity I B Relative to integral intensity IA and integral intensity I B The total ratio D.

[0055] In this invention, the angle difference C between the diffraction angles of the peaks A and B can be greater than 0.31° and less than 0.68°. The ratio D can be greater than 0 and less than 0.63. The ratio D is obtained by fitting the above-mentioned peaks A and B to the integral intensity I of peak B based on Gaussian and Lorentz functions. B The integral intensity I relative to the above peak A A The integral intensity I of peak B above B The total ratio.

[0056] The method for manufacturing the precursor of the positive electrode active material of the present invention is not particularly limited, and the following methods can be listed as examples.

[0057] First, prepare an aqueous NiCo solution by dissolving a water-soluble nickel source (nickel compound) and a water-soluble cobalt source (cobalt compound) in ion-exchanged water, and an aqueous Mn solution by dissolving a water-soluble manganese source (manganese compound) in ion-exchanged water. At this point, regarding the amounts of nickel and cobalt in the NiCo aqueous solution and the amounts of manganese in the Mn aqueous solution, when these NiCo and Mn aqueous solutions are mixed, the stoichiometric ratio (mol%) of nickel, cobalt, and manganese relative to the total stoichiometric ratio (mol%) of nickel, cobalt, and manganese is typically equal to the stoichiometric ratio (mol%) of nickel, cobalt, and manganese constituting the nickel-cobalt-manganese complex hydroxide. There are no particular limitations on the water-soluble metal compounds used; for example, sulfates can be included. The concentrations of the NiCo and Mn aqueous solutions can be appropriately set.

[0058] Next, a certain amount of NH3 aqueous solution (ammonium ion donor) is added to the reaction vessel, and nitrogen is used to replace the nitrogen while stirring with a stirrer to form a non-oxidizing atmosphere.

[0059] Next, add an aqueous sodium hydroxide solution to the reaction vessel, maintaining the pH at an alkaline level (e.g., pH 12), while simultaneously adding the aforementioned NiCo, Mn, and NH3 aqueous solutions dropwise into the vessel. The dropping rates of each aqueous solution can be set appropriately. The reaction temperature is not particularly limited; for example, it can be set to 60°C.

[0060] After the reaction is complete, a drying process is performed. This drying process can be carried out, for example, at 120°C for 1 hour under an inert gas atmosphere.

[0061] The precursor of the positive electrode active material of the present invention can be used as a positive electrode active material for batteries such as lithium-ion batteries by, for example, by conversion into lithium nickel cobalt manganese composite oxide.

[0062] The lithium nickel cobalt manganese composite oxide can be manufactured, for example, from the precursor of the present invention by the following method: mixing a nickel cobalt manganese composite hydroxide, which is the precursor of the present invention, with a lithium compound that serves as a lithium source, and then calcining the resulting mixture.

[0063] Examples of lithium compounds include at least one selected from lithium carbonate, lithium nitrate, lithium acetate, lithium hydroxide, lithium oxide, and lithium chloride.

[0064] Regarding the ratio of lithium compounds to precursors in the mixture, the molar percentage (mol%) of lithium and other metals in the target cathode active material relative to the total stoichiometry (mol%) of lithium and metals contained in the precursor is typically equal to the molar percentage (mol%) of lithium and other metals in the mixture. There are no particular limitations on the mixing method; known methods may be used.

[0065] The resulting mixture can be used to obtain lithium nickel cobalt manganese composite oxide, for example, by calcining at 700°C to 950°C for 8 to 10 hours. Calcination can be performed using a known calcining furnace such as a muffle furnace.

[0066] It is believed that the positive electrode active material obtained by sintering the precursor of the present invention is usually composed of single crystal particles.

[0067] Here, a single crystal particle is a single particle that does not constitute a secondary particle; it refers to a particle that is essentially composed of a single crystal. Since grain boundaries cannot be identified in the SEM image, it can be confirmed that it is a single crystal particle.

[0068] The precursor of the positive electrode active material provided by the present invention can be used, for example, as a precursor of the positive electrode active material constituting the positive electrode of a battery (such as a lithium-ion battery). That is, in the present invention, a battery in which a positive electrode, an electrolyte layer, and a negative electrode are stacked in sequence can be provided, wherein the positive electrode contains the positive electrode active material obtained from the precursor of the present invention.

[0069] The following is an explanation of the battery.

[0070] The positive electrode has a positive electrode layer and, if necessary, a positive electrode current collector.

[0071] The positive electrode layer is a layer containing at least a positive electrode active material. The positive electrode active material may contain only the positive electrode active material obtained from the precursor of the present invention described above, or it may further contain other active materials. The content of the positive electrode active material in the positive electrode layer is not particularly limited, and may, for example, be 20% to 80% by mass.

[0072] The positive electrode layer may contain at least one of an electrolyte, a conductive material, and a binder, as needed.

[0073] As an electrolyte, examples include solid electrolytes. Solid electrolytes can be inorganic solid electrolytes such as sulfide solid electrolytes, halide solid electrolytes, oxide solid electrolytes, and complexed hydride solid electrolytes, or organic solid electrolytes such as gel electrolytes. The proportion of solid electrolyte in the positive electrode layer can be, for example, 10% to 60% by mass.

[0074] Examples of conductive materials include carbon materials, metal particles, and conductive polymers. Examples of carbon materials include particulate carbon materials such as acetylene black (AB) and Ketjen black (KB). Other examples of carbon materials include fibrous carbon materials such as fumed carbon fiber (VGCF), carbon nanotubes (CNTs), and carbon nanofibers (CNFs). The proportion of conductive material in the positive electrode layer can be, for example, 0.1% to 5% by mass.

[0075] Examples of binders include styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber (NBR), butadiene rubber (BR), and polyvinylidene fluoride (PVDF). Furthermore, examples of binders include polytetrafluoroethylene (PTFE), styrene-isoprene-styrene block copolymer (SIS), and ethylene-propylene-diene copolymer (EPDM). The proportion of binder in the positive electrode layer can be, for example, 0.5% to 5% by mass.

[0076] Materials used as positive current collectors include, for example, SUS, Cr, Au, Pt, Zn, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the positive current collector is, for example, 0.1 μm or more and 100 μm or less. The shape of the positive current collector can be foil-like or plate-like. The top view shape of the positive current collector is not particularly limited; for example, it can be circular, elliptical, rectangular, or any polygonal shape. The positive current collector can also be composed of a buffer layer, an elastic layer, or a PTC (Positive Temperature Coefficient) thermistor layer disposed on its surface.

[0077] The negative electrode has a negative electrode layer and, if necessary, a negative electrode current collector.

[0078] The negative electrode layer is a layer containing at least a negative electrode active material. Additionally, the negative electrode layer may contain at least one of an electrolyte, a conductive material, and a binder, depending on requirements. Examples of negative electrode active materials for lithium-ion batteries include carbon materials such as natural graphite, elemental Li, and Li alloys.

[0079] Regarding the electrolyte, conductive material, and binder used in the negative electrode layer, the same substances as those described in the positive electrode layer can be listed.

[0080] Materials used as negative electrode current collectors include, for example, SUS, aluminum, copper, nickel, iron, titanium, and carbon. The thickness of the negative electrode current collector is, for example, 0.1 μm or more and 100 μm or less. The shape of the negative electrode current collector can be foil-like or plate-like. The top view shape of the negative electrode current collector is not particularly limited; for example, it can be circular, elliptical, rectangular, or any polygonal shape. The negative electrode current collector can be composed of a buffer layer, an elastic layer, or a PTC thermistor layer disposed on its surface.

[0081] The electrolyte layer is a layer formed between the positive electrode layer and the negative electrode layer, and it contains at least an electrolyte. Examples of electrolytes, besides the solid electrolytes described in the positive electrode layer above, include liquid electrolytes.

[0082] Electrolytes can be aqueous or non-aqueous. They can be used alone or in combination.

[0083] Aqueous electrolytes contain water as a main solvent. That is, based on the total amount of solvent (liquid component) constituting the electrolyte (100 mol%), water can account for 50 mol% or more, particularly 70 mol% or more, and further 90 mol% or more. On the other hand, there is no particular upper limit to the proportion of water in the solvent.

[0084] The solvent contains water as the main component, but may also contain solvents other than water. Examples of solvents other than water include one or more selected from ethers, carbonates, nitriles, alcohols, ketones, amines, amides, sulfur compounds, and hydrocarbons. Based on the total amount (100 mol%) of the solvent (liquid component) constituting the electrolyte, the solvents other than water may be 50 mol% or less, particularly 30 mol% or less, and further, 10 mol% or less.

[0085] Aqueous electrolytes contain electrolytes. Electrolytes used in aqueous electrolytes can be conventionally known electrolytes. Examples of electrolytes include lithium salts, nitrates, acetates, and sulfates of imide compounds. Specific examples include lithium bis(fluorosulfonyl)imide (LiFSI) and lithium bis(trifluoromethanesulfonyl)imide (LiTFSI). Furthermore, specific examples include lithium bis(pentafluoroethanesulfonyl)imide (LiBETI) and lithium bis(nonafluorobutanesulfonyl)imide. Further, specific examples include lithium nonafluoro-N-[(trifluoromethanesulfonyl)butanesulfonamide] and lithium N,N-hexafluoro-1,3-disulfonylimide. Further, specific examples include CH3COOLi, LiPF6, LiBF4, Li2SO4, and LiNO3.

[0086] The concentration of the electrolyte in an aqueous electrolyte can be appropriately set according to the required battery characteristics, within a range that does not exceed the saturation concentration of the electrolyte relative to the solvent. This is because, in the case of residual solid electrolyte in an aqueous electrolyte, the solid may hinder the battery reaction.

[0087] For example, when using LiTFSI as the electrolyte, the aqueous electrolyte may contain more than 1 mol of LiTFSI per 1 kg of the aforementioned water, particularly more than 5 mol, and further more than 7.5 mol. There is no particular upper limit, for example, it may be less than 25 mol.

[0088] As a non-aqueous electrolyte, a non-aqueous electrolyte containing lithium salt and non-aqueous solvent is usually used.

[0089] Examples of lithium salts include inorganic lithium salts such as LiPF6, LiBF4, LiClO4, and LiAsF6. Furthermore, examples of organic lithium salts include organic lithium salts such as LiCF3SO3, LiN(SO2CF3)2(Li-TFSI), LiN(SO2C2F5)2, and LiC(SO2CF3)3.

[0090] Examples of non-aqueous solvents include ethylene carbonate (EC), propylene carbonate (PC), butyl carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (EMC), γ-butyrolactone, sulfolane, acetonitrile (AcN), dimethoxymethane, 1,2-dimethoxyethane (DME), 1,3-dimethoxypropane, diethyl ether, tetraethylene glycol dimethyl ether (TEGDME), tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide (DMSO), and mixtures thereof. From the viewpoint of ensuring high dielectric constant and low viscosity, non-aqueous solvents can be mixtures of cyclic carbonate compounds such as EC, PC, and BC, which have high dielectric constants and high viscosity, and chain carbonate compounds such as DMC, DEC, and EMC, which have low dielectric constants and low viscosity. A mixture of EC and DEC can also be a non-aqueous solvent.

[0091] The concentration of lithium salt in non-aqueous electrolytes can be, for example, 0.3M to 5M.

[0092] Non-aqueous electrolytes can contain ionic liquids. Ionic liquids can include, for example, sulfonium salts, ammonium salts, and pyridine. Salt, piperidine Salt, pyrrolidine Salt, Morpholine Salt, Salt, imidazole At least one of the group consisting of salts and their derivatives.

[0093] In the electrolyte layer, a membrane that is impregnated with the electrolyte and prevents the positive electrode layer from contacting the negative electrode layer can also be used.

[0094] The material used for the membrane is not particularly limited as long as it is a porous membrane; examples include resins such as polyethylene (PE), polypropylene (PP), polyester, polyvinyl alcohol, cellulose, and polyamide. The membrane material can be polyethylene or polypropylene. Furthermore, the aforementioned membrane can be a single-layer structure or a multi-layer structure. Examples of multi-layer membranes include two-layer PE / PP membranes, or three-layer PP / PE / PP or PE / PP / PE membranes.

[0095] The diaphragm can be made of resin nonwoven fabric, glass fiber nonwoven fabric, or other nonwoven fabrics.

[0096] The battery may further include constraint clamps that apply constraint pressure to the positive electrode layer, electrolyte layer, and negative electrode layer along the thickness direction. The constraint pressure can be, for example, 0.1 MPa to 100 MPa.

[0097] There are no particular limitations on the type of battery; generally, they are batteries in which metal ions conduct electricity between the positive and negative electrode layers. Lithium-ion batteries are an example of such batteries. Furthermore, a battery can be a primary battery or a secondary battery, with the latter being more suitable for repeated charging and discharging, making it useful, for example, as a vehicle battery.

[0098] There are no particular limitations on the shape of the battery; for example, it can be coin-shaped, cylindrical, square, sheet-shaped, button-shaped, flat, or stacked.

[0099] Batteries can be used in various applications, including as power sources for vehicles such as hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), battery electric vehicles (BEVs), gasoline vehicles, and diesel vehicles. Specifically, they can also be used as power sources for driving hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), or battery electric vehicles (BEVs). Furthermore, batteries can be used as power sources for mobile bodies other than vehicles (such as trains, ships, and airplanes), and also as power sources for electrical products such as information processing devices.

[0100] Examples 1 to 4

[0101] Synthesis of precursors for positive electrode active materials

[0102] A NiCo aqueous solution was prepared by dissolving NiSO4 and CoSO4 in ion-exchanged water, and a Mn aqueous solution was prepared by dissolving MnSO4 in ion-exchanged water. Regarding the Ni / Co / Mn ratio, when the NiCo and Mn aqueous solutions were mixed, the Ni / Co / Mn ratio, expressed as a mole percent, was 80 / 10 / 10.

[0103] A certain amount of NH3 aqueous solution was added to the reaction vessel, and the mixture was stirred while the reaction vessel was purged with nitrogen. NaOH aqueous solution was then added to the reaction vessel to maintain an alkaline pH (pH=12), while the aforementioned NiCo aqueous solution, Mn aqueous solution, and NH3 aqueous solution were added dropwise. The reaction temperature was set to 60℃. After the reaction was completed, the mixture was dried at 120℃ for 1 hour under an inert gas atmosphere.

[0104] In Examples 1 to 4, the concentration and dropping rate of the Mn aqueous solution were changed to synthesize the various precursors.

[0105] XRD analysis of precursors of positive electrode active materials

[0106] The precursors obtained in Examples 1 to 4 were subjected to powder XRD analysis using a Rigaku Smart Lab II XRD apparatus via the wide-angle method. The analytical conditions are described below. Figures 1-3 The results of XRD analysis of the precursor of Example 4 are shown in the figure.

[0107] XRD analysis conditions

[0108] • Measurement angle: 10°~120°

[0109] • Tube ball: Cu

[0110] Optical system: Kα

[0111] Voltage: 45kV

[0112] Current: 200mA

[0113] • Determination method: Continuous method

[0114] • Step size: 0.02°

[0115] • Scanning speed: 2° / minute

[0116] ·IS: 1 / 2

[0117] RS: 20mm

[0118] • Detection mode: One-dimensional

[0119] XRD analysis confirmed that each precursor in Examples 1 to 4 had a peak belonging to the (100) plane of space group R3-m split into two peaks, A and B. Furthermore, the diffraction angles (2θ) at the peak apex of peaks A and B obtained through XRD analysis were... A 2θ B The angle difference C of these diffraction angles, and the integral intensity I of peak B. B Integral intensity I relative to peak AA The integral intensity I of peak B B The total ratio D is shown in Table 1.

[0120] Comparative Example 1

[0121] Synthesis of precursors for positive electrode active materials

[0122] NiSO4, CoSO4, and MnSO4 were dissolved in ion-exchanged water to prepare an aqueous solution of the metal raw materials. The Ni / Co / Mn ratio in the aqueous solution was 80 / 10 / 10 (mol%). The concentration of the aqueous solution (the ratio of all raw materials to the aqueous solution) was 1.5 mol%.

[0123] A certain amount of NH3 aqueous solution was added to the reaction vessel, and the mixture was stirred while nitrogen was purged from the vessel. NaOH aqueous solution was then added to the reaction vessel to maintain an alkaline pH (pH=12), while the above-mentioned metal raw material aqueous solution and NH3 aqueous solution were added dropwise. The reaction temperature was set at 60℃, and the reaction time was set at 10 hours.

[0124] After the reaction is complete, the mixture is dried at 120°C for 1 hour under an inert gas atmosphere.

[0125] XRD analysis of precursors of positive electrode active materials

[0126] XRD analysis was performed in the same manner as in the above embodiment, and a peak belonging to the (100) plane of space group R3-m was observed, but no splitting of the peak was observed. The diffraction angle at the peak apex was 33.30°.

[0127] It should be noted that in Table 1, regarding Comparative Example 1, since the splitting of the aforementioned peaks was not observed, the diffraction angle 2θ was set to... A and diffraction angle 2θ B Considering it as 33.30°, set the angle difference C and the integral intensity ratio D to zero.

[0128] Synthesis of positive electrode active material

[0129] The precursors synthesized in Examples 1-4 and Comparative Example 1 were mixed with a lithium compound (LiOH) as a lithium source using a mortar. The resulting mixtures were calcined in a calcining furnace at 950°C for 10 hours, thereby synthesizing the positive electrode active material (LiNi) of Examples 1-4 and Comparative Example 1. 0.8 Co 0.1 Mn 0.1 O2).

[0130] Battery cell fabrication

[0131] Using the positive electrode active materials of Examples 1 to 4 and Comparative Example 1, small laminated battery cells of Examples 1 to 4 and Comparative Example 1 were fabricated.

[0132] Specifically, firstly, using a coating applicator with film thickness adjustment function, a positive electrode composite paste containing a positive electrode active material, acetylene black as a conductive material, and PVDF (4% by mass) as a binder is coated onto the surface of a metal foil serving as the positive electrode current collector. The coating applicator with film thickness adjustment function is manufactured by AllGlide Co., Ltd. Then, it is dried at 80°C for 5 minutes using a dryer to create a positive electrode with a positive electrode layer on the positive electrode current collector.

[0133] On the other hand, using a coating applicator (manufactured by AllGlide Co., Ltd.) with a film thickness adjustment function, a negative electrode composite material containing natural graphite as the negative electrode active material is coated onto the surface of a metal foil serving as the negative electrode current collector. Then, it is dried at 80°C for 5 minutes using a dryer to produce a negative electrode with a negative electrode layer on the negative electrode current collector.

[0134] Prepare a 1M LiPF6 solution containing LiPF6 as the electrolyte, ethylene carbonate (EC), dimethyl carbonate (DMC), and ethyl methyl carbonate (EMC) as the solvent in a volume ratio of EC / DMC / EMC = 3 / 4 / 3.

[0135] The above-mentioned positive electrode, separator and negative electrode are stacked, and the above-mentioned electrolyte is impregnated in the separator to produce a small laminated battery cell of Examples 1 to 4 and Comparative Example 1.

[0136] Evaluation of battery cells

[0137] For each small laminated battery cell fabricated, the discharge capacity was measured before and after a cycle test. The cycle test was conducted for 100 cycles under the following conditions.

[0138] <Discharge Capacity Measurement Conditions>

[0139] • C ratio: 0.1C

[0140] • Measurement mode: CCCV discharge

[0141] Temperature: 25℃

[0142] <Loop Condition>

[0143] • C ratio: 0.3C

[0144] • Mode: CC charge / discharge

[0145] Temperature: 50℃

[0146] The capacity retention rate after the cycle test is calculated using the measured values ​​of discharge capacity before and after the cycle test, and the values ​​of discharge capacity before and after the cycle test are used.

[0147] Capacity retention (%) = (Discharge capacity after cycle test) / (Discharge capacity before cycle test) × 100

[0148] Based on the capacity retention rate of Comparative Example 1, the capacity retention rates of Examples 1 to 4 were standardized using the following formula.

[0149] Standardized capacity maintenance rate = (Capacity maintenance rate of each embodiment) / (Capacity maintenance rate of Comparative Example 1)

[0150] The results are shown in Table 1.

[0151] (Table 1)

[0152] As shown in Table 1, compared with Comparative Example 1, Examples 1 to 4, which used precursors whose peaks of the (100) plane belonging to space group R3-m split into two, showed improved capacity retention. In Comparative Example 1, a precursor whose peaks of the (100) plane belonging to space group R3-m were not split was used. In the precursors of Examples 1 to 4, the angle difference C between the diffraction angles of the peaks A and B was 0.31° or more and 0.68° or less. In the precursors of Examples 1 to 4, the integral intensity I of peak B was... B Integral intensity I relative to peak A A The integral intensity I of peak B B The total ratio D is greater than 0 and less than 0.63.

[0153] Furthermore, in Comparative Example 1, where an aqueous solution of metal raw materials, consisting of NiSO4, CoSO4, and MnSO4 dissolved in ion-exchanged water, was added dropwise to the reaction vessel during precursor synthesis, the peak belonging to the (100) plane of space group R3-m did not split into two. On the other hand, in Examples 1 to 4, an aqueous solution of NiCo, consisting of NiSO4 and CoSO4 dissolved in ion-exchanged water, and an aqueous solution of Mn, consisting of MnSO4 dissolved in ion-exchanged water, were added dropwise to the reaction vessel respectively. In these Examples 1 to 4, the peak belonging to the (100) plane of space group R3-m split into two. Therefore, it can be seen that in the nickel-cobalt-manganese composite hydroxide, the aforementioned peak splits when the aqueous solutions of NiCo and Mn are added dropwise to the reaction vessel respectively.

Claims

1. A precursor of a positive electrode active material, wherein, The precursor is a nickel-cobalt-manganese composite hydroxide particle. The precursor, in XRD analysis, has a peak belonging to the (100) surface of space group R3-m split into two peaks, A and B.

2. The precursor according to claim 1, wherein, The angle difference C between the diffraction angles of the peaks of peak A and peak B is greater than 0.31° and less than 0.68°. The integral intensity I of peak B is obtained by fitting peak A and peak B with a Gaussian function and a Lorentz function. B The integral intensity I relative to peak A A and the integral intensity I of peak B B The total ratio D, which is greater than 0 and less than 0.63, is expressed in the following formula. Ratio D=I B / ( I A +I B ).

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