Positive electrode active material precursor for lithium ion secondary battery and method for producing same, Positive electrode active material for lithium ion secondary battery and method for producing same

Abstract

To provide a positive electrode active material precursor for a lithium ion secondary battery capable of forming a positive electrode active material for a lithium ion secondary battery having higher spheroidity and a smaller particle size.SOLUTION: A precursor is a nickel-manganese carbonate complex composed of Ni:Mn:M=x:y:t in terms of substance amount ratio (however, in the equation, x+y+t=1, 0.2≤x≤0.3, 0.7≤y≤0.8, 0≤t≤0.2 are satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W), and the precursor has spheroidity, and the average particle size of the precursor is 3 to 15 μm.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a positive electrode active material precursor for a lithium ion secondary battery and a method for producing the same, and a positive electrode active material for a lithium ion secondary battery and a method for producing the same. [Background technology]

[0002] In recent years, with the widespread use of small information terminals such as smartphones and tablet PCs, there is a strong demand for the development of small, lightweight lithium-ion secondary batteries with high energy density, as well as high-output secondary batteries for use as large batteries for driving motors, etc.

[0003] Lithium ion secondary batteries are a type of secondary battery that meets these requirements. Lithium ion secondary batteries are composed of a negative electrode, a positive electrode, an electrolyte, etc., and use materials capable of desorbing and inserting lithium as the negative electrode active material and the positive electrode active material.

[0004] Currently, research and development of lithium-ion secondary batteries is being actively conducted. In particular, lithium-ion secondary batteries that use layered or spinel-type lithium metal composite oxides as the positive electrode material can achieve a high voltage of about 4V, and are therefore being put to practical use as batteries with high energy density.

[0005] Currently, the positive electrode materials for such lithium-ion secondary batteries include lithium cobalt composite oxide (LiCoO2), which is relatively easy to synthesize, lithium nickel composite oxide (LiNiO2), which uses nickel, which is cheaper than cobalt, and lithium nickel cobalt manganese composite oxide (LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2), lithium manganese composite oxide (LiMn2O4), lithium nickel manganese composite oxide (LiNi 0.5 Mn 0.5 O2), lithium-rich nickel-cobalt-manganese composite oxide (Li2MnO3-LiNi x Mn y Coz Lithium composite oxides such as CrO2 have been proposed.

[0006] Among these positive electrode active materials, nickel-manganese composite oxides with a spinel structure have been attracting attention in recent years as a material that can achieve a high voltage of about 5 V, which is even higher than that of conventional lithium-ion batteries.

[0007] A method for producing a precursor for obtaining a nickel-manganese composite oxide having a spinel structure is disclosed in, for example, Patent Document 1. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] JP 2019-021610 A Summary of the Invention [Problem to be solved by the invention]

[0009] In order to increase the output of a lithium-ion secondary battery, it is effective to increase the ratio of the positive electrode active material per electrode, and it is useful to use a positive electrode active material with high sphericity and small particle size. However, since the particles in Patent Document 1 are particles with a porous structure, the tap density is not high and the ratio of the positive electrode active material per electrode is considered to be low.

[0010] In view of the problems associated with the above-described conventional techniques, an object of the present invention is to provide a positive electrode active material precursor for a lithium ion secondary battery, which is capable of forming a positive electrode active material for a lithium ion secondary battery having higher sphericity and smaller particle size. [Means for solving the problem]

[0011] The positive electrode active material precursor for a lithium ion secondary battery according to one embodiment of the present invention has a substance amount ratio of Ni:Mn:M=x:y:t (wherein, x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2 are satisfied, and M is any one of Mg, Ca, Al, Ti, V, Cr, Fe 、C U, Zn, Zr, Nb 、W and wherein the additive element is one or more selected from the group consisting of nickel manganese carbonate composites, the composites being made up of secondary particles (excluding porous particles) formed by agglomeration of a plurality of primary particles, the primary particles having the crystallinity of the carbonate, the secondary particles having spherical shape, and the average particle size of the secondary particles being 3 to 15 μm. Effect of the Invention

[0012] According to one aspect of the present invention, it is possible to provide a precursor of a positive electrode active material for a lithium ion secondary battery, which is capable of forming a positive electrode active material for a lithium ion secondary battery having higher sphericity and smaller particle size. [Brief description of the drawings]

[0013] [Figure 1] FIG. 2 is a diagram showing an example of a flow of a method for producing a positive electrode active material precursor for a lithium ion secondary battery according to an embodiment of the present invention. [Diagram 2] FIG. 4 is a diagram showing another example of the flow of the method for producing a positive electrode active material precursor for a lithium ion secondary battery according to an embodiment of the present invention. [Diagram 3] 1 is a SEM observation image of a precursor obtained in an example according to the present invention. [Figure 4] 1 is a SEM observation image of a positive electrode active material for a lithium ion secondary battery obtained in an example according to the present invention. [Diagram 5] FIG. 2 is an explanatory diagram of a cross-sectional configuration of a coin battery produced in an example according to the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0014] Hereinafter, the form for carrying out the present invention will be described with reference to the drawings. However, the present invention is not limited to the following embodiment, and various modifications and substitutions can be made to the following embodiment without departing from the scope of the present invention.

[0015] [Positive electrode active material precursor for lithium-ion secondary batteries] In this embodiment, first, a configuration example of a positive electrode active material precursor for a lithium ion secondary battery will be described.

[0016] The precursor of the present embodiment is a nickel manganese carbonate composite composed of Ni:Mn:M=x:y:t in terms of substance ratio (wherein, x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2 are satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W).

[0017] The positive electrode active material precursor for a lithium ion secondary battery of this embodiment (hereinafter also simply referred to as "precursor") can include substantially spherical secondary particles formed by aggregation of a plurality of primary particles, and can also be composed of the secondary particles.

[0018] The precursor of this embodiment made of a nickel manganese carbonate composite has a highly uniform particle size and is a fine crystal, and can be used as a raw material, i.e., a precursor, for a positive electrode active material for a lithium ion secondary battery.

[0019] The precursor of this embodiment will be specifically described below.

[0020] (composition) The nickel manganese carbonate compound contained in the precursor of this embodiment is a nickel manganese compound in the form of a basic carbonate having a composition of Ni:Mn:M=x:y:t in terms of the substance amount ratio, as described above.

[0021] In the above substance amount ratio, x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2 are satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W.

[0022] The precursor of this embodiment may include compounds of variable composition that are mixtures of carbonates and hydroxides, such as those represented by general formula 1: xMn2(CO3)3·yMn(OH)3 and general formula 2: Ni4CO3(OH)6(H2O)4.

[0023] When the precursor of the present embodiment is used as a positive electrode active material precursor for a lithium ion secondary battery, in order to further improve battery characteristics such as cycle characteristics and output characteristics, one or more additive elements can be added to the nickel manganese carbonate composite as described above.

[0024] It is preferable that one or more types of added elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W are uniformly distributed inside the secondary particles and / or uniformly cover the surfaces of the secondary particles within a predetermined substance amount ratio t.

[0025] However, in the case of a nickel manganese carbonate compound, if the substance amount ratio t of the added element exceeds 0.2, the metal element that contributes to the oxidation-reduction reaction (Redox reaction) decreases, which may result in a decrease in battery capacity.

[0026] In addition, even if the nickel manganese carbonate composite does not contain an additive element, the positive electrode active material prepared using the precursor of this embodiment has sufficient battery characteristics such as cycle characteristics and output characteristics. Therefore, it is not necessary to contain an additive element. Therefore, the additive element is adjusted so that the substance amount ratio t is within the range of 0≦t≦0.2.

[0027] (particle size) The average particle size of the precursor in this embodiment is preferably 3.0 μm or more and 15.0 μm or less, and more preferably 5.0 μm or more and 12.0 μm or less. The average particle size of the synthesized positive electrode active material is close to the average particle size of the precursor. The desirable average particle size of the precursor depends on the design of the target battery and positive electrode active material, but generally, if the average particle size of the precursor is less than 3.0 μm, the coating property may decrease when manufacturing an electrode using the positive electrode active material obtained from the precursor, and the packing density of the positive electrode active material in the positive electrode may decrease. On the other hand, if the average particle size of the precursor exceeds 15.0 μm, it may be difficult to uniformly synthesize the positive electrode active material obtained from the precursor throughout the particles, which may deteriorate the battery characteristics. Therefore, the average particle size of the precursor is preferably in the above range. If the average particle size of the precursor is within the above range, the average particle size of the obtained positive electrode active material can also be controlled to the above optimal range. The average particle size refers to the volume average particle size Mv based on the effective diameter, and the average particle size is measured, for example, by laser diffraction / scattering method or dynamic light scattering method.

[0028] (shape) The precursor particles of this embodiment are composed of secondary particles formed by agglomeration of a plurality of primary particles. The secondary particles have a substantially spherical shape and have high sphericity. The shape of the synthesized positive electrode active material is usually close to the shape of the precursor, so that a positive electrode active material having high sphericity can be obtained as described later.

[0029] [Method of manufacturing a positive electrode active material precursor for lithium ion secondary batteries] Next, a configuration example of the method for producing a positive electrode active material precursor for a lithium ion secondary battery according to this embodiment (hereinafter, also simply referred to as "precursor production method") will be described.

[0030] In the method for producing a precursor according to the present embodiment, a precursor can be obtained by a crystallization reaction, and the obtained precursor can be washed and dried as necessary.

[0031] Specifically, the method for producing a precursor of the present embodiment relates to a method for producing a positive electrode active material precursor for a lithium ion secondary battery, which is a nickel manganese carbonate composite composed of a substance ratio of Ni:Mn:M=x:y:t (wherein, x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2 are satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W), and can have the following steps.

[0032] The method for producing a precursor according to the present embodiment may include a crystallization step of generating nuclei in a mixed aqueous solution obtained by mixing an initial aqueous solution containing an alkaline substance of carbonate and an ammonium ion donor, an aqueous solution containing nickel as a metal component, and an aqueous solution containing manganese as a metal component in the presence of carbonate ions, and growing the generated nuclei. The crystallization step may be performed by controlling the pH value of the mixed aqueous solution to 5.4 to 9.0 at a reaction temperature of 40° C. as a reference, and controlling the dissolved oxygen concentration in the mixed aqueous solution to 10% or less.

[0033] An example of a flow of the method for producing a precursor according to the present embodiment is shown in Figure 1. As shown in Figure 1, the method for producing a precursor according to the present embodiment includes a crystallization step.

[0034] (1) Crystallization process An example of a flow of the method for producing a precursor according to the present embodiment is shown in Figure 1. As shown in Figure 1, the method for producing a precursor according to the present embodiment includes a crystallization step.

[0035] As shown in FIG. 1, in the crystallization step, first, ion-exchanged water (water), an alkaline substance of carbonate, and an ammonium ion donor are mixed in a reaction tank to prepare an initial aqueous solution.

[0036] The ammonium ion donor is not particularly limited, but is preferably one or more selected from an aqueous solution of ammonium carbonate, aqueous ammonia, an aqueous solution of ammonium chloride, and an aqueous solution of ammonium sulfate.

[0037] The alkaline substance of the carbonate is not particularly limited, but is preferably one or more selected from sodium carbonate, sodium hydrogen carbonate, and potassium carbonate.

[0038] The initial aqueous solution is adjusted to 9.0 or less at a reaction temperature of 40° C. by adding an acidic substance as necessary. By setting the pH value of the initial aqueous solution within the above range, it is possible to suppress the remaining impurities, and therefore it is possible to obtain a precursor with a small amount of remaining impurities. In this case, the pH value of the initial aqueous solution is preferably adjusted to 5.4 or more and 9.0 or less, more preferably adjusted to 6.4 or more and 8.0 or less, and even more preferably adjusted to 6.4 or more and 7.4 or less. The pH in this case can be adjusted, for example, by adding a pH adjusting aqueous solution described later.

[0039] During the crystallization step, the pH value of the mixed aqueous solution described below is preferably within the above range. Since the pH value of the mixed aqueous solution fluctuates slightly during the crystallization step, the maximum pH value of the mixed aqueous solution during the crystallization step can be set as the pH value of the mixed aqueous solution in the crystallization step.

[0040] During the crystallization process, the pH value of the mixed aqueous solution is preferably controlled to fluctuate within 0.2 above or below the center value (set pH value). This is because if the pH value of the mixed aqueous solution fluctuates widely, the growth of the particles contained in the precursor of this embodiment may not be constant, and uniform particles with a narrow particle size distribution may not be obtained.

[0041] The acidic substance is not particularly limited, and for example, sulfuric acid can be preferably used. Note that, as the acidic substance, it is preferable to use an acid of the same type as the metal salt used in preparing the aqueous solution containing the metal component to be added to the initial aqueous solution.

[0042] In the crystallization step, carbonate ions are present in the reaction tank. The method of supplying carbonate ions is not particularly limited, and for example, carbonate ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with an oxygen-free gas described later into the reaction tank. Carbonate ions can also be supplied by using a carbonate salt when preparing the initial aqueous solution or the pH-adjusted aqueous solution.

[0043] In the crystallization process, an oxygen-free gas is blown into the reaction tank in which the initial aqueous solution is prepared, thereby controlling the dissolved oxygen concentration in the mixed aqueous solution to 10% or less. Thereafter, as described below, an aqueous solution containing metal components, such as an aqueous solution containing nickel as a metal component and an aqueous solution containing manganese (hereinafter also referred to as "aqueous solution containing nickel, etc."), is supplied into the reaction tank at a constant flow rate, for example, and the pH value of the mixed aqueous solution is controlled to be within a predetermined range. In this manner, under an environment in which the inclusion of oxygen is suppressed and blocked, the reaction between oxygen and the crystallized product is suppressed, and fine particles close to single crystals of carbonate are generated. These particles become the nuclei (nuclear particles) of the precursor. The particle size of the secondary particles can be controlled by the reaction time of the crystallization process. In addition, the secondary particles obtained by the crystallization process have an approximately spherical shape and high sphericity, as described above. Although the detailed reason is unclear, it is considered that a precursor with high sphericity is crystallized due to the crystallinity of carbonate.

[0044] As the oxygen-free gas, for example, an inert gas such as nitrogen gas or argon gas, or carbon dioxide gas can be used.

[0045] When an oxygen-free gas is supplied to the reaction tank, the supply amount of the oxygen-free gas can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution. During the crystallization process, it is desirable to maintain the dissolved oxygen concentration at 10% or less. Since the dissolved oxygen in the mixed aqueous solution is consumed during the crystallization process, if the dissolved oxygen concentration in the mixed aqueous solution is 10% or less, the incorporation of oxygen can be sufficiently suppressed.

[0046] In the crystallization step, an oxygen-free gas may be continuously supplied into the reaction tank while an aqueous solution containing a metal component, such as an aqueous solution containing nickel as the metal component, is being added to the initial aqueous solution.

[0047] In addition, the initial aqueous solution and the mixed aqueous solution can be appropriately stirred using a stirring device such as a stirring blade with a power within the range described below, whereby the dissolved oxygen concentrations in the initial aqueous solution and the mixed aqueous solution as a whole can be made more uniform.

[0048] The stirring power required in the reaction tank is 1.0 kW / m 3 More than 10.0kW / m 3 It is preferable to adjust it to 2.0kW / m or less. 3 More than 8.0kW / m 3 It is more preferable to adjust the stirring power required in the reaction vessel to the above value, because it is possible to reduce particle aggregation and reduce the particle size of secondary particles contained in the obtained precursor.

[0049] Next, in the crystallization step, an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, is added to and mixed with the initial aqueous solution in a reaction tank to produce a mixed aqueous solution. This produces fine particles (primary particles) that will become the nuclei (nuclear particles) of the precursor in the initial aqueous solution containing the metal component. As a result, a mixed aqueous solution containing the primary particles that will become the nucleus particles is obtained. Whether or not a predetermined amount of nucleus particles has been produced can be determined by the amount of metal salt contained in the mixed aqueous solution.

[0050] When adding an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, to the initial aqueous solution, the pH value of the resulting mixed aqueous solution is preferably controlled within a predetermined range as described above. For this reason, it is preferable to gradually drip the aqueous solution containing the metal component into the initial aqueous solution rather than adding it all at once. This allows the solution containing the metal component or the mixed aqueous solution containing the metal component described below to be supplied to the reaction tank at a constant flow rate, for example.

[0051] In order to maintain the pH of the mixed aqueous solution within a predetermined range, it is preferable to drop a pH-adjusting aqueous solution when supplying the aqueous solution containing the metal component or the mixed aqueous solution containing the metal component described below. The pH-adjusting aqueous solution is not particularly limited, but for example, an aqueous solution containing an alkaline substance of carbonate and an ammonium ion donor can be used.

[0052] The alkaline substance of the carbonate is not particularly limited, but is preferably one or more selected from sodium carbonate, sodium hydrogen carbonate, and potassium carbonate.

[0053] The ammonium ion donor is not particularly limited, but is preferably one or more selected from an aqueous solution of ammonium carbonate, aqueous ammonia, an aqueous solution of ammonium chloride, and an aqueous solution of ammonium sulfate.

[0054] The method for supplying the pH-adjusted aqueous solution into the reaction tank is not particularly limited, and for example, the aqueous solution may be added while thoroughly stirring the resulting mixed aqueous solution using a pump capable of controlling the flow rate, such as a metering pump, so that the pH value of the mixed aqueous solution is maintained within a predetermined range.

[0055] Here, the aqueous solution containing nickel as a metal component and the aqueous solution containing manganese as a metal component in the aqueous solution containing metal components, which are added to the initial aqueous solution in the crystallization step, will be described.

[0056] An aqueous solution containing nickel as a metal component and an aqueous solution containing manganese as a metal component can contain a metal compound containing each metal component. That is, for example, an aqueous solution containing manganese as a metal component can contain a metal compound containing manganese.

[0057] As the metal compound, it is preferable to use a water-soluble metal compound, and examples of the water-soluble metal compound include nitrates, sulfates, hydrochlorides, etc. Specifically, for example, nickel sulfate, manganese sulfate, etc. can be preferably used.

[0058] The aqueous solution containing nickel as the metal component and the aqueous solution containing manganese as the metal component may be mixed in part or whole in advance, and the mixed aqueous solution containing the metal components may be added to the initial aqueous solution.

[0059] The composition ratio of each metal in the obtained precursor is the same as the composition ratio of each metal in the metal component-containing mixed aqueous solution. Therefore, it is preferable to prepare the metal component-containing mixed aqueous solution by, for example, adjusting the ratio of the dissolved metal compounds so that the composition ratio of each metal contained in the metal component-containing mixed aqueous solution added to the initial aqueous solution in the nucleation step is equal to the composition ratio of each metal in the generated precursor.

[0060] In addition, in cases where mixing multiple metal compounds causes certain metal compounds to react with each other and generate unnecessary compounds, aqueous solutions containing the respective metal components may be added to the initial aqueous solution at the same time in a predetermined ratio.

[0061] The aqueous solutions containing the metal components may be added individually to the initial aqueous solution without being mixed. In this case, it is preferable to prepare the aqueous solutions containing the metal components so that the composition ratio of the metal components contained in the aqueous solution as a whole containing the metal components to be added is equal to the composition ratio of the metal components in the precursor to be generated.

[0062] In this case, the concentration of the metal compound in the mixed aqueous solution is preferably 1 mol / L or more and 2.6 mol / L or less, and more preferably 1.5 mol / L or more and 2.2 mol / L or less.

[0063] This is because if the concentration of the metal compound in the mixed aqueous solution is less than 1 mol / L, the amount of crystallized material per reaction tank will be small, which is undesirable as it will reduce productivity, whereas if the concentration of the metal compound in the mixed aqueous solution exceeds 2.6 mol / L, it may exceed the saturation concentration at room temperature, causing crystals to reprecipitate and clog the piping of the equipment.

[0064] The concentration of the metal compounds means the concentration of the metal compounds derived from the aqueous solution containing nickel as a metal component, the aqueous solution containing manganese as a metal component, and, in some cases, the aqueous solution containing an additional element added to the mixed aqueous solution.

[0065] As described above, the precursor produced by the method for producing a precursor according to the present embodiment is a nickel manganese carbonate composite composed of Ni:Mn:M=x:y:t in terms of the amount of substances (wherein x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2 are satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W).

[0066] That is, the precursor of this embodiment can further contain an additive element in addition to nickel and manganese.

[0067] For this reason, in the crystallization step, if necessary, an aqueous solution containing one or more types of additive elements (hereinafter also simply referred to as "additive elements") selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W (hereinafter also simply referred to as "aqueous solution containing additive elements") can also be added to the initial aqueous solution.

[0068] In addition, when an aqueous solution containing nickel as a metal component is mixed to prepare a metal component-containing mixed aqueous solution and then added to the initial aqueous solution, an aqueous solution containing an additive element may be added and mixed to the metal component-containing mixed aqueous solution.

[0069] Furthermore, when an aqueous solution containing nickel as a metal component is added to the initial aqueous solution separately without being mixed, an aqueous solution containing an additive element can be added separately to the initial aqueous solution together with the aqueous solution.

[0070] Here, the aqueous solution containing the additive element can be prepared using, for example, a compound containing the additive element. Examples of the compound containing the additive element include magnesium sulfate, calcium sulfate, sodium aluminate, titanium sulfate, ammonium peroxotitanate, potassium titanium oxalate, vanadium sulfate, ammonium vanadate, chromium sulfate, potassium chromate, iron sulfate, cobalt sulfate, copper sulfate, zinc sulfate, zirconium sulfate, zirconium nitrate, niobium oxalate, ammonium molybdate, sodium tungstate, and ammonium tungstate, and the compound can be selected according to the element to be added.

[0071] As described above, it is preferable that the additive element is uniformly distributed inside the core particle contained in the precursor and / or that the surface of the core particle is uniformly coated with the additive element.

[0072] By adding an aqueous solution containing the above-mentioned additive element to the mixed aqueous solution, the additive element can be uniformly dispersed inside the core particles contained in the precursor.

[0073] In order to uniformly coat the surfaces of the secondary particles of the precursor with the additive element, for example, a coating step of coating with the additive element can be carried out after completion of the particle growth step described below. The coating step will be described later.

[0074] The temperature of the mixed aqueous solution is preferably maintained at 20° C. or higher, and more preferably at 30° C. or higher. The upper limit of the temperature of the mixed aqueous solution is not particularly limited, but is preferably, for example, 70° C. or lower, and more preferably 50° C. or lower.

[0075] This is because, in the crystallization step, if the temperature of the mixed aqueous solution is less than 20° C., the solubility is low, so that nucleation is likely to occur and control may become difficult.

[0076] On the other hand, if the temperature of the mixed aqueous solution exceeds 70° C. in the crystallization step, distortion may occur in the primary crystals, resulting in a low tap density.

[0077] In the crystallization step, the ammonium ion concentration in the mixed aqueous solution is preferably 1 g / L or more and 20 g / L or less, and is particularly preferably maintained at a constant value.

[0078] This is because, if ammonia is not added, a large number of fine particles are generated during nucleation, and the resulting particles are in the form of agglomerates of a large number of primary particles, which may lead to a decrease in tap density. In addition, by setting the concentration of ammonium ions to 1 g / L or more, the generation and aggregation of fine particles can be further suppressed, and the decrease in tap density can be further suppressed. In addition, the particle size distribution of the precursor can be narrowed.

[0079] By setting the ammonium ion concentration at 20 g / L or less, the precursor particle nuclei can be grown uniformly. Also, by maintaining the ammonium ion concentration at a constant value in the crystallization process, the solubility of the metal ions can be stabilized, and the growth of uniform precursor particles can be promoted.

[0080] The ammonium ion concentration in the mixed aqueous solution is preferably adjusted to 1 g / L or more and 20 g / L or less, for example, by using an ammonium ion donor in the initial aqueous solution or the pH-adjusted aqueous solution and adjusting the supply amount thereof.

[0081] The pH value, ammonium ion concentration, and amount of dissolved oxygen in the initial aqueous solution and the mixed aqueous solution can be measured using a general pH meter, ion meter, and dissolved oxygen meter, respectively.

[0082] By completing the addition of the metal component-containing mixed aqueous solution to the initial aqueous solution, the mixed aqueous solution can become a precursor particle-containing aqueous solution that contains sufficiently grown precursor particles.

[0083] In this way, in the crystallization process, fine particles (primary particles) that are the nuclei (core particles) of the precursor can be generated and grown in the precursor particle-containing aqueous solution. The crystallization process is then continued until the core particles grow to a desired particle size, and the core particles are grown to obtain a precursor having secondary particles of a desired particle size. Furthermore, in the crystallization process according to the precursor manufacturing method of this embodiment, a precursor with high sphericity can be obtained.

[0084] In order to uniformly coat the surfaces of the secondary particles, which are the precursors, with the additive element, for example, a coating step of coating with the additive element may be carried out after the crystallization step is completed. The coating step will be described later.

[0085] (Other aspects of the crystallization process) In the method for producing a precursor according to the present embodiment, the crystallization step is composed of one step as shown in Fig. 1, but is not limited thereto. For example, the crystallization step can include a nucleation step and a particle growth step.

[0086] Specifically, the method for producing a precursor according to the present embodiment may include the following steps.

[0087] The method for producing a precursor according to the present embodiment can have two steps: a nucleation step for generating nuclei in a mixed aqueous solution obtained by mixing an initial aqueous solution containing an alkaline carbonate substance and an ammonium ion donor, an aqueous solution containing nickel as a metal component, and an aqueous solution containing manganese as a metal component in the presence of carbonate ions, and a particle growth step for growing the nuclei formed in the nucleation step. The nucleation step can be performed by controlling the pH value of the mixed aqueous solution to 5.4 to 7.5 at a reaction temperature of 40° C. and controlling the dissolved oxygen concentration in the mixed aqueous solution to 10% or less.

[0088] A description will now be given of one configuration example of the flow of the method for producing a precursor according to this embodiment, shown in Fig. 2. As shown in Fig. 2, the method for producing a precursor according to this embodiment includes (A) a nucleation step, and (B) a particle growth step in which precursor particles are produced by a coprecipitation method after the nucleation step.

[0089] Hereinafter, each step of the method for producing a precursor according to the present embodiment will be specifically described. (2-1) Nucleation process The nucleation step will be described with reference to FIG.

[0090] As shown in FIG. 2, in the nucleation step, first, ion-exchanged water (water), an alkaline substance of carbonate, and an ammonium ion donor are mixed in a reaction tank to prepare an initial aqueous solution.

[0091] The ammonium ion donor is not particularly limited as in the case of the crystallization step described above, but is preferably one or more selected from an aqueous ammonium carbonate solution, an aqueous ammonia solution, an aqueous ammonium chloride solution, and an aqueous ammonium sulfate solution.

[0092] Similarly to the crystallization step described above, the alkaline carbonate is not particularly limited, but is preferably at least one selected from sodium carbonate, sodium hydrogen carbonate, and potassium carbonate.

[0093] In the nucleation step, it is preferable to maintain the pH value of the mixed aqueous solution obtained by adding an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, to the initial aqueous solution at a lower value than that of the particle growth step described below. This is because maintaining the pH value of the mixed aqueous solution low makes it possible to make the nuclei in the mixed aqueous solution smaller and to increase their number, thereby making it possible to reduce the particle size of the secondary particles contained in the obtained precursor.

[0094] Therefore, the pH value of the initial aqueous solution is preferably adjusted to 5.4 to 7.5, more preferably 6.4 to 7.4, by adding an acidic substance as necessary. In particular, the pH value is more preferably adjusted to 6.4 to 7.1.

[0095] During the nucleation step, the pH value of the mixed aqueous solution is preferably in the above range. Since the pH value of the mixed aqueous solution fluctuates slightly during the nucleation step, the maximum pH value of the mixed aqueous solution during the nucleation step can be set as the pH value of the mixed aqueous solution in the nucleation step, and it is preferable that the pH value of the mixed aqueous solution is in the above range.

[0096] The acidic substance is not particularly limited, and for example, sulfuric acid can be preferably used. Note that, as the acidic substance, it is preferable to use an acid of the same type as the metal salt used in preparing the aqueous solution containing the metal component to be added to the initial aqueous solution.

[0097] During the nucleation step, the pH value of the mixed aqueous solution is preferably controlled within 0.2 above or below the center value (set pH value). This is because, if the H value of the mixed aqueous solution fluctuates widely, the nucleation of particles containing the precursor of this embodiment may not be constant, and uniform particles may not be obtained.

[0098] In the nucleation step, an oxygen-free gas is blown into the reaction tank in which the initial aqueous solution is prepared to control the dissolved oxygen concentration in the initial aqueous solution to 10% or less, and then an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, described below, is supplied at a constant flow rate, for example, to control the pH value of the mixed aqueous solution to fall within a predetermined range. This reduces the dissolved oxygen concentration in the mixed aqueous solution, suppressing the reaction between oxygen and the crystallized product, and fine particles similar to single crystals of carbonate are generated as nuclei.

[0099] As the oxygen-free gas, for example, an inert gas such as nitrogen gas or argon gas, or carbon dioxide gas can be used.

[0100] In the nucleation step, an oxygen-free gas can be continuously supplied into the reaction tank while an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, is being added to the initial aqueous solution.

[0101] When an oxygen-free gas is supplied to the reaction tank, the amount of the oxygen-free gas supplied can be confirmed by measuring the dissolved oxygen concentration in the mixed aqueous solution, and it is desirable to maintain it at 10% or less. Since the dissolved oxygen in the mixed aqueous solution is consumed during the crystallization process, if the dissolved oxygen concentration in the mixed aqueous solution is 10% or less, the incorporation of oxygen can be sufficiently suppressed.

[0102] In addition, by appropriately stirring the initial aqueous solution and the mixed aqueous solution described below using a stirring device such as a stirring blade with a power within the range described below, the dissolved oxygen concentrations in the initial aqueous solution and the entire mixed aqueous solution can be made more uniform.

[0103] The stirring power required in the reaction tank is 1.0 kW / m 3 More than 10.0kW / m 3 It is preferable to adjust it to 2.0kW / m or less. 3 More than 8.0kW / m 3 It is more preferable to adjust the stirring power required in the reaction vessel to the above value, because it is possible to reduce particle aggregation and reduce the particle size of secondary particles contained in the obtained precursor.

[0104] In the nucleation step, an aqueous solution containing nickel as a metal component and an aqueous solution containing manganese as a metal component are added to and mixed with the initial aqueous solution in a reaction tank to generate a mixed aqueous solution.

[0105] When an aqueous solution containing nickel or the like as a metal component is added to the initial aqueous solution, the pH value of the resulting mixed aqueous solution is preferably controlled to 5.4 to 7.5, more preferably 6.4 to 7.4, and even more preferably 6.4 to 7.1, based on a reaction temperature of 40° C. For this reason, it is preferable to gradually dropwise add an aqueous solution containing a metal component, such as an aqueous solution containing nickel, to the initial aqueous solution, rather than adding it all at once.

[0106] In addition, in order to control the pH of the mixed aqueous solution, a pH-adjusting aqueous solution can be added dropwise in conjunction with the dropping of an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component. The pH-adjusting aqueous solution in this case is not particularly limited, but for example, an aqueous solution containing an alkaline substance of carbonate and an ammonium ion donor can be used. The alkaline substance of carbonate and the ammonium ion donor are not particularly limited, but the same substances as those described in the initial aqueous solution can be used. The method of supplying the pH-adjusting aqueous solution into the reaction tank is not particularly limited, and for example, the mixed aqueous solution obtained may be added with a pump capable of flow rate control, such as a metering pump, while thoroughly stirring the resulting mixed aqueous solution so that the pH value of the mixed aqueous solution is maintained within a predetermined range.

[0107] Then, as described above, precursor nuclei can be generated in a mixed aqueous solution obtained by adding an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, to the initial aqueous solution. Whether or not a predetermined amount of nuclei has been generated in the mixed aqueous solution can be determined based on the amount of metal salt contained in the mixed aqueous solution.

[0108] As for the aqueous solution containing nickel as a metal component, the aqueous solution containing manganese as a metal component, and the aqueous solution containing an additive element, which are added to the initial aqueous solution in the nucleation step, the same aqueous solutions as those in the crystallization step described above can be suitably used.

[0109] In order to uniformly coat the surfaces of the secondary particles of the precursor with the additive element as described above, for example, a coating step of coating with the additive element can be carried out after completion of the particle growth step described below. The coating step will be described later.

[0110] In the nucleation step, an aqueous solution containing nickel as a metal component is added to the initial aqueous solution in the presence of carbonate ions, and mixed to form a mixed aqueous solution, in which nuclei can be generated. In this case, the method of supplying carbonate ions is not particularly limited, and for example, carbonate ions can be supplied to the initial aqueous solution or the mixed aqueous solution by supplying carbon dioxide gas together with an oxygen-free gas described below into the reaction tank. Carbonate can also be used to supply carbonate ions when preparing the initial aqueous solution or the pH-adjusted aqueous solution.

[0111] As described above, in the nucleation step, an aqueous solution containing nickel as a metal component is added to and mixed with the initial aqueous solution in the presence of carbonate ions to prepare a mixed aqueous solution, and nuclei can be generated in the mixed aqueous solution.

[0112] In this case, the concentration of the metal compound in the mixed aqueous solution is preferably 1 mol / L or more and 2.6 mol / L or less, and more preferably 1.5 mol / L or more and 2.2 mol / L or less.

[0113] This is because if the concentration of the metal compound in the mixed aqueous solution is less than 1 mol / L, the amount of crystallized material per reaction tank will be small, which is undesirable as it will reduce productivity, whereas if the concentration of the metal compound in the mixed aqueous solution exceeds 2.6 mol / L, it may exceed the saturation concentration at room temperature, causing crystals to reprecipitate and clog the piping of the equipment.

[0114] The concentration of the metal compounds means the concentration of the metal compounds derived from an aqueous solution containing nickel as a metal component, an aqueous solution containing manganese as a metal component, and an aqueous solution containing an additional element added in some cases, which are added to the mixed aqueous solution.

[0115] In the nucleation step, the temperature of the mixed aqueous solution is preferably maintained at 20° C. or higher, and more preferably at 30° C. or higher. The upper limit of the temperature of the mixed aqueous solution in the nucleation step is not particularly limited, but is preferably, for example, 70° C. or lower, and more preferably 50° C. or lower.

[0116] This is because, in the nucleation step, if the temperature of the mixed aqueous solution is less than 20° C., the solubility is low, so nucleation is likely to occur and control may become difficult.

[0117] On the other hand, if the temperature of the mixed aqueous solution exceeds 70° C. in the nucleation step, distortion may occur in the primary crystals, resulting in a low tap density.

[0118] In the nucleation step, the ammonium ion concentration in the mixed aqueous solution is preferably 1 g / L or more and 20 g / L or less, and is particularly preferably kept at a constant value. By setting the ammonium ion concentration at 20 g / L or less, fine particles (primary particles) that are the nuclei (nuclear particles) of the precursor can be uniformly generated. In addition, by maintaining the ammonium ion concentration at a constant value, the solubility of metal ions can be stabilized, and the generation of uniform precursor nuclei (nuclear particles) can be promoted.

[0119] This is because, when ammonia is not added, many fine particles are generated during nucleation, and the resulting nuclei are in the form of agglomerates of many primary particles, which may lead to a decrease in tap density. In addition, by setting the concentration of ammonium ions to 1 g / L or more, the generation and aggregation of fine particles can be further suppressed, and the decrease in tap density can be further suppressed. In addition, the particle size distribution of the precursor obtained after the particle growth process described below can be made narrower.

[0120] The ammonium ion concentration in the mixed aqueous solution is preferably adjusted to 1 g / L or more and 20 g / L or less, for example, by using an ammonium ion donor in the initial aqueous solution or the pH-adjusted aqueous solution and adjusting the supply amount thereof.

[0121] The pH value, ammonium ion concentration, and amount of dissolved oxygen in the initial aqueous solution and the mixed aqueous solution can be measured using a general pH meter, ion meter, and dissolved oxygen meter, respectively.

[0122] After the nucleation step is completed, i.e., after the addition of the metal component-containing mixed aqueous solution to the initial aqueous solution is completed, it is preferable to continue stirring the mixed aqueous solution and crush the generated nuclei (nucleus crushing step). When the nucleus crushing step is performed, it is preferable to perform the step for 1 minute or more, and more preferably for 3 minutes or more. By performing the nucleus crushing step, it is possible to more reliably suppress the generated nuclei from agglomerating, the particle size from becoming coarse, and the density inside the particles from decreasing.

[0123] (2-2) Particle growth process Next, the particle growth step will be described with reference to FIG.

[0124] In the particle growth step, the nuclei generated in the nucleation step can be grown.

[0125] Specifically, for example, as shown in FIG. 2, in the particle growth step, the pH value of the mixed aqueous solution obtained in the nucleation step can be adjusted first.

[0126] In this case, the pH value of the mixed aqueous solution can be adjusted to, for example, 6.0 to 9.0 at a reaction temperature of 40° C. In this case, the pH value of the mixed aqueous solution is more preferably adjusted to 6.4 to 8.0, and even more preferably adjusted to 6.4 to 7.5. In this case, the pH can be adjusted, for example, by adding the above-mentioned pH adjusting aqueous solution.

[0127] This is because by adjusting the pH value of the mixed aqueous solution to 6.0 or more and 9.0 or less, it is possible to suppress the impurity cations from remaining.

[0128] The particle growth step can be a step of adding and mixing an aqueous solution containing nickel as a metal component and an aqueous solution containing manganese as a metal component in the presence of carbonate ions to the mixed aqueous solution obtained after the nucleation step.

[0129] The mixed aqueous solution after the nucleation step may be a mixed aqueous solution whose pH has been adjusted after the nucleation step as described above.

[0130] In addition, the aqueous solution containing nickel as a metal component and the aqueous solution containing manganese as a metal component may be mixed in part or in whole, as in the nucleation step, to form a mixed aqueous solution containing metal components, and added to the mixed aqueous solution. In addition, in cases where mixing a plurality of metal compounds causes specific metal compounds to react with each other to generate unnecessary compounds, the aqueous solutions containing the respective metal components may be added individually to the mixed aqueous solution.

[0131] Furthermore, when an aqueous solution containing nickel as a metal component is added to the mixed aqueous solution, an aqueous solution containing an additive element can be added at the same time, as in the nucleation step. As described above, an aqueous solution containing an additive element can be mixed and added to the mixed aqueous solution containing the metal components. In addition, when the aqueous solutions containing each metal component are added individually to the mixed aqueous solution, an aqueous solution containing an additive element can also be added individually to the mixed aqueous solution.

[0132] The aqueous solution containing nickel as a metal component and the aqueous solution containing manganese as a metal component may be the same as those used in the nucleation step. The concentrations, etc., may be adjusted separately.

[0133] When adding an aqueous solution containing nickel as a metal component to the mixed aqueous solution, the pH value of the resulting mixed aqueous solution is preferably controlled within a predetermined range as described below. Therefore, the aqueous solution containing nickel as a metal component can be gradually dropped into the mixed aqueous solution rather than being added all at once. Therefore, the aqueous solution containing these metal components or the mixed aqueous solution containing the metal components can be supplied to a reaction tank at a constant flow rate, for example.

[0134] In the particle growth step, an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, can be added to the mixed aqueous solution after the pH value adjustment as described above. In this case, for the same reason as in the case of adjusting the pH value before the start of the particle growth step, the pH value of the mixed aqueous solution is preferably maintained in the same range as that of the mixed aqueous solution after the pH value adjustment, that is, 6.0 to 9.0, more preferably 6.4 to 8.0, and even more preferably 6.4 to 7.5. In addition, as described in the nucleation step, in the particle growth step, it is preferable to control the pH value of the mixed aqueous solution to a higher pH value than that in the nucleation step.

[0135] In the particle growth step, a precursor with a small amount of remaining impurities can be obtained by controlling the pH value of the mixed aqueous solution within the above-mentioned range.

[0136] In addition, since the pH value of the mixed aqueous solution fluctuates slightly during the particle growth process, the maximum pH value of the mixed aqueous solution during the particle growth process can be used as the pH value of the mixed aqueous solution in the particle growth process, and it is preferable that the pH value of the mixed aqueous solution is in the above-mentioned range.

[0137] In particular, during the particle growth process, it is preferable to control the fluctuation range of the pH value of the mixed aqueous solution to within 0.2 above or below the center value (set pH value). This is because if the fluctuation range of the pH value of the mixed aqueous solution is large, the growth of the particles containing the precursor will not be constant, and uniform particles with a narrow particle size distribution range may not be obtained.

[0138] When the aqueous solution containing metal components or the mixed aqueous solution containing metal components obtained by mixing these components is supplied to the mixed aqueous solution as described above, it is preferable to add a pH-adjusting aqueous solution so that the pH of the mixed aqueous solution can be maintained within a predetermined range. The pH-adjusting aqueous solution can be the same as that used in the nucleation step, and is not particularly limited. For example, an aqueous solution containing an alkaline substance of carbonate and an ammonium ion donor can be used. The alkaline substance of carbonate and the ammonium ion donor are not particularly limited, and the same substances as those described in the nucleation step can be used. The method of supplying the pH-adjusting aqueous solution into the reaction tank is not particularly limited, and for example, the mixed aqueous solution obtained can be added with a pump capable of flow control, such as a metering pump, while thoroughly stirring the resulting mixed aqueous solution so that the pH value of the mixed aqueous solution is maintained within a predetermined range.

[0139] In the particle growth step, the ammonium ion concentration in the mixed aqueous solution is preferably 1 g / L or more and 20 g / L or less, and is particularly preferably kept at a constant value. This is because by making the ammonium ion concentration 1 g / L or more, it is possible to suppress the generation of new nuclei in the particle growth step and to narrow the particle size distribution of the precursor.

[0140] This is because the ammonium ion concentration of 20 g / L or less allows the nuclei of the precursor particles to grow uniformly, and because the ammonium ion concentration is maintained at a constant value in the particle growth process, the solubility of the metal ions can be stabilized, and the particle growth of the uniform precursor particles can be promoted.

[0141] The ammonium ion concentration in the mixed aqueous solution is preferably adjusted to 1 g / L or more and 20 g / L or less, for example, by using an ammonium ion donor in the pH-adjusted aqueous solution and adjusting the supply amount thereof.

[0142] In the particle growth step, an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, can be added to and mixed with the mixed aqueous solution in the presence of carbonate ions. In this case, the method of supplying carbonate ions is not particularly limited, and for example, carbonate ions can be supplied to the mixed aqueous solution by supplying carbon dioxide gas together with an oxygen-free gas described below into the reaction tank. In addition, carbonate ions can be supplied by using a carbonate salt when preparing the pH-adjusted aqueous solution.

[0143] In the particle growth step, an oxygen-free gas is blown into the reaction tank to control the dissolved oxygen concentration in the initial aqueous solution to 10% or less, while an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, is supplied at a constant flow rate, for example, to control the pH value of the mixed aqueous solution to fall within a predetermined range. This reduces the dissolved oxygen concentration in the mixed aqueous solution, suppressing the reaction between oxygen and the crystallized product, so that the fine crystals generated in the nucleation step further aggregate to generate large secondary particles. In addition, the secondary particles obtained in the particle growth step have an approximately spherical shape and high sphericity, similar to those in the crystallization step. Although the detailed reason is unclear, it is thought that the secondary particles grow to be highly spherical due to the crystallinity of carbonate.

[0144] The oxygen-free gas can be supplied in the same manner as in the nucleation step described above.

[0145] The mixed aqueous solution can be stirred using a stirring device such as a stirring blade. The stirring power required in the particle growth step may be the same as that in the nucleation step, but since aggregation hardly occurs once the particles have grown to a certain extent, there is no problem if the reaction is carried out with a stirring power required smaller than that in the nucleation step.

[0146] The particle size of the secondary particles contained in the precursor can be controlled by the reaction time of the particle growth step.

[0147] That is, in the particle growth step, if the reaction is continued until the particles grow to a desired particle size, a precursor having secondary particles of a desired particle size can be obtained.

[0148] As described above, by carrying out the crystallization step shown in FIG. 1 and the nucleation step and particle growth step shown in FIG. 2, an aqueous solution of precursor particles, which is a slurry containing precursor particles, is obtained.

[0149] In the method for producing a precursor according to the present embodiment, it is preferable to use an apparatus that does not recover the precursor product until the reaction in the crystallization step or the reaction from the nucleation step to the particle growth step is completed. Such an apparatus may be, for example, a batch reaction tank that is normally used and equipped with an agitator. By adopting such an apparatus, unlike a continuous crystallization apparatus that recovers a product by general overflow, the problem of the particles being grown being recovered simultaneously with the overflow liquid does not occur, and it is preferable to obtain particles with a narrow particle size distribution and a uniform particle size.

[0150] In order to control the atmosphere in the reaction vessel, it is preferable to use an apparatus capable of controlling the atmosphere, such as a sealed apparatus.

[0151] By using an apparatus capable of controlling the atmosphere in the reaction tank, it is possible to give particles containing the precursors the structure described above, and also to proceed the coprecipitation reaction almost uniformly, so that it is possible to obtain particles with an excellent particle size distribution, i.e., particles with a narrow particle size distribution range.

[0152] In the crystallization process, the pH value of the mixed aqueous solution is adjusted to be within a predetermined range, and an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, is further added to the mixed aqueous solution, thereby making it possible to obtain uniform precursor particles.

[0153] In addition, in the particle growth process, the pH value of the mixed aqueous solution obtained in the nucleation process is adjusted to be within a predetermined range, and an aqueous solution containing a metal component, such as an aqueous solution containing nickel as a metal component, is added to the mixed aqueous solution, thereby making it possible to obtain uniform precursor particles.

[0154] (Coating process) The method for producing a precursor according to the present embodiment may further include a coating step of coating the surfaces of the particles of the precursor obtained in the crystallization step or particle growth step with an additive element as described above after the precursor is obtained in the crystallization step or particle growth step. That is, the method for producing a precursor according to the present embodiment may further include a coating step of coating the particles (secondary particles) of the precursor obtained in the crystallization step or particle growth step with an additive element.

[0155] The coating step can be, for example, any of the following steps.

[0156] For example, a step can be performed in which an aqueous solution containing the additive element is first added to a slurry in which the precursor particles are suspended, and the additive element is precipitated on the surfaces of the precursor particles by a crystallization reaction.

[0157] In addition, the slurry in which the precursor particles are suspended is preferably made into a slurry of the precursor particles using an aqueous solution containing an additive element. In addition, when the aqueous solution containing the additive element is added to the slurry in which the precursor particles are suspended, the pH of the mixed aqueous solution of the slurry and the aqueous solution containing the additive element is preferably controlled to be 6.0 or more and 9.0 or less. This is because the surface of the precursor particles can be particularly uniformly coated with the additive element by controlling the pH of the mixed aqueous solution of the slurry and the aqueous solution containing the additive element to the above range.

[0158] The coating step can also be a step of spraying an aqueous solution or a slurry containing the additive element onto the precursor particles and then drying them.

[0159] Alternatively, the coating step may be a step of spraying a slurry in which the precursor particles and a compound containing the additive element are suspended, and then drying the slurry.

[0160] Alternatively, the precursor particles and a compound containing the additive element may be mixed by a solid phase method.

[0161] As for the aqueous solution containing the additive element described here, the same aqueous solution as that described in the crystallization step and the nucleation step can be used. In addition, in the coating step, an alkoxide solution containing the additive element may be used instead of the aqueous solution containing the additive element.

[0162] As described above, in the crystallization step, nucleation step, and particle growth step, when an aqueous solution containing an additive element is added to the initial aqueous solution or the mixed aqueous solution, and the coating step is performed to coat the surface of the precursor particle with the additive element, it is preferable to reduce the amount of additive element ions added to the initial aqueous solution or the mixed aqueous solution in the crystallization step, nucleation step, and particle growth step by the amount of coating. This is because by reducing the amount of the aqueous solution containing the additive element added to the mixed aqueous solution by the amount of coating, the substance amount ratio of the additive element contained in the obtained precursor to other metal components can be made to a desired value.

[0163] The coating step of coating the surfaces of the precursor particles with the additive element as described above may be carried out on the precursor particles after heating, following the crystallization step and particle growth step.

[0164] By carrying out the above crystallization step and particle growth step, a precursor particle aqueous solution, which is a slurry containing precursor particles, is obtained. After the crystallization step shown in Fig. 1 or the particle growth step shown in Fig. 2 is completed, a washing step and a drying step can also be carried out.

[0165] (3) Cleaning process The washing step will now be described. In the washing step, the slurry containing the precursor particles obtained in the above-mentioned crystallization step and particle growth step can be washed.

[0166] In the washing step, first, the slurry containing the precursor particles can be filtered, then washed with water, and filtered again.

[0167] The filtration may be carried out by a commonly used method, for example, a centrifuge or a suction filter.

[0168] The washing with water may be carried out by a method that is usually used, as long as it is possible to remove excess raw materials and the like contained in the precursor particles.

[0169] In order to prevent the incorporation of impurities, it is preferable to use water with as low an impurity content as possible for the water used in washing, and it is more preferable to use pure water.

[0170] (4) Drying process The drying step will now be described: In the drying step, the precursor particles washed in the washing step can be dried.

[0171] First, in the drying step, the washed precursor particles can be dried at a drying temperature of, for example, 80° C. or higher and 230° C. or lower.

[0172] After the drying step, the precursor of this embodiment can be obtained.

[0173] According to the method for producing a precursor of the present embodiment, it is possible to obtain a precursor capable of forming a positive electrode active material for a lithium ion secondary battery containing particles with higher sphericity and smaller particle size.

[0174] Furthermore, in the method for producing a precursor according to this embodiment shown in FIG. 1, the crystal size of the precursor particles obtained by the crystallization reaction can be controlled.

[0175] Furthermore, according to the method for producing a precursor of this embodiment shown in FIG. 2, the time during which a nucleation reaction mainly occurs (nucleation step) and the time during which a particle growth reaction mainly occurs (particle growth step) are clearly separated, so that even if both steps are carried out in the same reaction tank, precursor particles (secondary particles) having a narrow particle size distribution can be obtained.

[0176] Therefore, according to the method for producing a precursor of this embodiment, it is possible to obtain a precursor having a small primary particle size, high secondary particle size uniformity, and high density (tap density).

[0177] In addition, in the precursor production method of this embodiment, the nucleation process and the particle growth process can be separately carried out in one reaction tank by simply adjusting the pH of the reaction solution. Therefore, the precursor production method of this embodiment is easy and suitable for large-scale production, and therefore it can be said that its industrial value is extremely great.

[0178] [Positive electrode active material for lithium-ion secondary batteries] Next, a configuration example of the positive electrode active material for a lithium ion secondary battery according to this embodiment (hereinafter, also simply referred to as "positive electrode active material") will be described.

[0179] The positive electrode active material of the present embodiment relates to a positive electrode active material for lithium ion secondary batteries that contains a lithium metal composite oxide. The lithium metal composite oxide can be expressed in terms of a substance ratio of Li:Ni:Mn:M=α:x:y:t (0.48≦α≦0.65, x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2, M is an additive element and is one or more elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W).

[0180] The positive electrode active material of this embodiment may contain a lithium metal composite oxide having a spinel crystal structure represented by LiM2O4, more specifically, a lithium nickel manganese composite oxide. The positive electrode active material of this embodiment may also be composed of the lithium metal composite oxide.

[0181] In the above formula, M is a metal element containing at least nickel and manganese, the metal element being adjusted to have an average valence of 3.5.

[0182] As already described in the precursor, in order to further improve the battery characteristics such as the cycle characteristics and output characteristics of the positive electrode active material of the lithium ion secondary battery, the lithium metal composite oxide may contain one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Co, Cu, Zn, Zr, Nb, Mo, and W. For the reasons already described in the precursor, the content of the additive element is preferably adjusted so that the substance amount ratio t is within the range of 0≦t≦0.2.

[0183] The tap density of the positive electrode active material of this embodiment is not particularly limited, but is preferably 1.5 g / cm 3 It is preferable that the content is 2.0 g / cm or more. 3 More preferably, the tap density of the positive electrode active material is greater than or equal to the tap density of the positive electrode active material. When the positive electrode constituting the secondary battery is fabricated, the packing density of the positive electrode active material in the positive electrode can be increased. Furthermore, when the packing density of the positive electrode active material in the positive electrode is greater, a positive electrode of the same volume can achieve a larger charge / discharge capacity.

[0184] (particle size) The average particle size of the positive electrode active material of this embodiment is preferably 3.0 μm or more and 15.0 μm or less, and more preferably 5.0 μm or more and 12.0 μm or less, similar to the average particle size of the precursor. As described above, generally, if the average particle size of the positive electrode active material is less than 3.0 μm, the coating property during electrode production and the packing density of the positive electrode active material in the positive electrode are reduced. On the other hand, if the average particle size of the positive electrode active material exceeds 15.0 μm, it becomes difficult to synthesize the positive electrode active material uniformly throughout the particles, which reduces the battery characteristics. The average particle size refers to the volume average particle size Mv based on the effective diameter, similar to the average particle size of the precursor described above.

[0185] (shape) The particles of the positive electrode active material of this embodiment have substantially spherical secondary particles, and like the precursor of this embodiment, the particles of the positive electrode active material have high sphericality.

[0186] When the positive electrode active material of this embodiment is used in the positive electrode of a 2032-type coin battery, for example, it is preferable that the positive electrode active material has a high initial discharge capacity of 135 mAh / g or more.

[0187] [Method of manufacturing positive electrode active material for lithium ion secondary batteries] Next, a configuration example of the method for producing a positive electrode active material for a lithium ion secondary battery according to this embodiment (hereinafter, also simply referred to as a "method for producing a positive electrode active material") will be described.

[0188] The method for producing the positive electrode active material of the present embodiment is not particularly limited as long as it can produce a positive electrode active material having the particle structure of the positive electrode active material described above. However, it is preferable to employ the following method, since it can produce the positive electrode active material more reliably.

[0189] The method for producing the positive electrode active material of the present embodiment may include the following steps.

[0190] The method can include three steps: a heat treatment step of heat-treating the positive electrode active material precursor for lithium ion secondary batteries obtained by the above-described method for producing a positive electrode active material precursor for lithium ion secondary batteries at a temperature of 80° C. or more and 600° C. or less; a mixing step of adding a lithium compound to the particles obtained by the heat treatment step and mixing them to form a lithium mixture; and a firing step of firing the lithium mixture in an oxidizing atmosphere at a temperature of 600° C. or more and 1000° C. or less.

[0191] Each step will be described below.

[0192] (1) Heat treatment process In the heat treatment step, the precursor described above can be heat treated at a temperature of 80° C. or higher and 600° C. or lower. By carrying out the heat treatment, moisture contained in the precursor can be removed, and the proportions of the metal substance amount and the lithium substance amount in the finally obtained positive electrode active material can be prevented from varying.

[0193] It is not necessary to convert all of the precursor into nickel-manganese composite oxide, since it is sufficient to remove moisture to such an extent that there is no variation in the ratio of the amount of substance of metal or the amount of substance of lithium in the positive electrode active material. However, in order to further reduce the above-mentioned variation, it is preferable to convert all of the precursor particles into composite oxide particles by setting the heating temperature at 500°C or higher.

[0194] In the heat treatment step, the heat treatment temperature is set to 80°C or higher because if the heat treatment temperature is lower than 80°C, excess moisture in the precursor particles cannot be removed, and there is a risk that the above-mentioned variations cannot be suppressed.

[0195] On the other hand, the heat treatment temperature is set to 600° C. or lower because if the heat treatment temperature exceeds 600° C., the particles may be sintered by roasting, making it difficult to obtain composite oxide particles with a uniform particle size.

[0196] The above-mentioned variations can be suppressed by determining in advance by analysis the metal components contained in the precursor particles corresponding to the heat treatment conditions and determining the substance amount ratio with respect to the lithium compound.

[0197] The heat treatment atmosphere is not particularly limited as long as it is a non-reducing atmosphere, but it is preferable to perform the heat treatment in an air stream, which is easy to carry out.

[0198] The heat treatment time is not particularly limited, but if it is less than one hour, excess moisture in the precursor particles may not be sufficiently removed, so it is preferably at least one hour, and more preferably 2 to 15 hours.

[0199] The equipment used for the heat treatment is not particularly limited as long as it can heat the precursor particles in a non-reducing atmosphere, preferably in an air flow, and an electric furnace that does not generate gas is preferably used.

[0200] (2)Mixing process The mixing step is a step of adding and mixing a lithium compound to the heat-treated particles obtained by heating in the heat treatment step to form a lithium mixture.

[0201] The heat-treated particles obtained by the heat treatment in the heat treatment step contain nickel manganese carbonate composite particles and / or nickel manganese composite oxide particles.

[0202] The heat-treated particles and the lithium compound are preferably mixed so that the ratio (Li / Me) of the amount of substance of metals other than lithium in the lithium mixture, i.e., the sum of the amounts of substance of nickel, manganese and additive elements (Me) to the amount of substance of lithium (Li) is 0.48 to 0.65. In this case, it is more preferable to mix so that Li / Me is 0.50 to 0.60.

[0203] In other words, since the Li / Me ratio does not change before and after the firing process, the Li / Me mixed in this mixing process becomes the Li / Me ratio in the positive electrode active material, and the Li / Me ratio in the lithium mixture is mixed so as to be the same as the Li / Me ratio in the positive electrode active material to be obtained.

[0204] The lithium compound used to form the lithium mixture is not particularly limited, but since it is easily available, for example, one or more selected from lithium hydroxide, lithium nitrate, and lithium carbonate can be preferably used.

[0205] In particular, in consideration of ease of handling and stability of quality, it is more preferable to use one or more types of lithium compounds selected from lithium hydroxide and lithium carbonate as the lithium compound used in forming the lithium mixture.

[0206] For mixing, a general mixer can be used, such as a shaker mixer, a Loedige mixer, a Julia mixer, or a V blender.

[0207] (3) Firing process The calcination step is a step of calcining the lithium mixture obtained in the mixing step to obtain a positive electrode active material. When the mixed powder is calcined in the calcination step, lithium in the lithium compound is diffused into the heat-treated particles, so that a lithium nickel manganese composite oxide is formed.

[0208] The calcination temperature for the lithium mixture in this case is not particularly limited, but is preferably, for example, from 600° C. to 1000° C.

[0209] This is because setting the sintering temperature to 600°C or higher sufficiently promotes the diffusion of lithium into the heat-treated particles, suppresses the residue of excess lithium and unreacted particles, and ensures sufficient battery characteristics when used in a battery.

[0210] However, if the firing temperature exceeds 1000°C, the composite oxide particles may be sintered violently, and abnormal grain growth may occur, resulting in coarse particles after firing. Such a positive electrode active material has a reduced specific surface area, and therefore when used in a battery, the resistance of the positive electrode increases and the battery capacity decreases. In addition, since a positive electrode active material having a spinel crystal structure is prone to taking an octahedral shape, if the firing temperature exceeds 1000°C, the number of octahedral particles may increase. By setting the firing temperature to 1000°C or less, the yield of a positive electrode active material having high sphericity can be increased.

[0211] The calcination temperature of the lithium mixture also affects the specific surface area of ​​the resulting positive electrode active material, and therefore can be selected from the above-mentioned temperature range according to the specific surface area required for the positive electrode active material. For example, when it is particularly required to suppress the specific surface area of ​​the positive electrode active material, it is preferable to set the calcination temperature at a higher temperature, for example, 900°C or higher and 950°C or lower.

[0212] From the viewpoint of uniformly carrying out the reaction between the heat-treated particles and the lithium compound, it is preferable to raise the temperature to the above-mentioned temperature at a rate of 2° C. / min to 10° C. / min.

[0213] Furthermore, the reaction can be made more uniform by maintaining the temperature at about the melting point of the lithium compound for about 1 hour to 5 hours. When the temperature is maintained at about the melting point of the lithium compound, the temperature can be increased to a predetermined baking temperature.

[0214] During the firing time, the holding time at the firing temperature is preferably 1 hour or more, and more preferably 2 hours or more and 24 hours or less.

[0215] This is because holding the material at the firing temperature for 2 hours or more can sufficiently promote the formation of lithium nickel manganese composite oxide. In addition, since the positive electrode active material having a spinel crystal structure is prone to take on an octahedral shape, holding the material for more than 24 hours may increase the number of octahedral particles. Holding the material for less than 24 hours can increase the yield of positive electrode active material with high sphericity.

[0216] After the holding time at the firing temperature has ended, although there are no particular limitations, in the case where the lithium mixture is loaded into a sagger and fired, it is preferable to cool the atmosphere to 200°C or less at a temperature drop rate of 2°C / min or more and 10°C / min or less in order to prevent deterioration of the sagger.

[0217] The firing atmosphere is preferably an oxidizing atmosphere, more preferably an atmosphere with an oxygen concentration of 18% by volume or more and 100% by volume or less, and particularly preferably an atmosphere of a mixture of oxygen and an inert gas with the oxygen concentration. That is, firing is preferably carried out in air or an oxygen-containing gas.

[0218] As described above, the atmosphere having an oxygen concentration of 18% by volume or more is preferable because the crystallinity of the lithium nickel manganese composite oxide can be sufficiently increased by setting the oxygen concentration to 18% by volume or more.

[0219] In particular, in consideration of the battery characteristics, it is preferable to carry out the reaction in an oxygen stream.

[0220] The furnace used for the calcination is not particularly limited as long as it can heat the lithium mixture in the air or in an oxygen-containing gas, but an electric furnace that does not generate gas is preferable from the viewpoint of keeping the atmosphere in the furnace uniform. In addition, either a batch type or a continuous type furnace can be used.

[0221] When lithium hydroxide or lithium carbonate is used as the lithium compound, the mixture may be calcined after the mixing step and before the calcination step. The calcination temperature is lower than the calcination temperature and is preferably 350° C. to 800° C., more preferably 450° C. to 780° C.

[0222] The calcination time is preferably about 1 hour or more and 10 hours or less, and more preferably 3 hours or more and 6 hours or less.

[0223] The calcination is preferably performed by maintaining the calcination temperature, particularly at a reaction temperature between lithium hydroxide or lithium carbonate and the heat-treated particles.

[0224] When the calcination is carried out, lithium is sufficiently diffused into the heat-treated particles, and a uniform lithium nickel manganese composite oxide can be obtained, which is preferable.

[0225] The lithium nickel manganese composite oxide particles obtained by the firing step may be aggregated or slightly sintered.

[0226] In this case, the mixture may be crushed to obtain the positive electrode active material of this embodiment that contains the lithium nickel manganese composite oxide.

[0227] Crushing refers to an operation in which mechanical energy is applied to an agglomerate of multiple secondary particles that is formed due to sintering necking between the secondary particles during firing, thereby separating the secondary particles with almost no destruction of the secondary particles themselves, thereby breaking down the agglomerates.

[0228] [Lithium-ion secondary battery] Next, a configuration example of the lithium ion secondary battery of this embodiment will be described. The lithium ion secondary battery of this embodiment can have a positive electrode using the above-mentioned positive electrode active material.

[0229] First, the structure of the lithium ion secondary battery of this embodiment will be described.

[0230] The lithium ion secondary battery of this embodiment (hereinafter also simply referred to as "secondary battery") can have substantially the same structure as a general lithium ion secondary battery, except that the positive electrode active material described above is used as the positive electrode material.

[0231] The secondary battery of this embodiment may have a structure including, for example, a case, and a positive electrode, a negative electrode, a non-aqueous electrolyte, and a separator housed in the case.

[0232] More specifically, the secondary battery of this embodiment may have an electrode body in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween, and the electrode body may be impregnated with a non-aqueous electrolyte, and the positive electrode current collector of the positive electrode and the positive electrode terminal connected to the outside, and the negative electrode current collector of the negative electrode and the negative electrode terminal connected to the outside may be connected by using current collecting leads or the like, and the battery may be sealed in a case.

[0233] It goes without saying that the structure of the secondary battery of this embodiment is not limited to the above example, and the external shape of the battery may be of various shapes, such as a cylindrical shape or a laminated shape.

[0234] (positive electrode) First, the positive electrode, which is a feature of the secondary battery of this embodiment, will be described. The positive electrode is a sheet-like member, and is formed by applying a positive electrode mixture paste containing the above-mentioned positive electrode active material onto the surface of a current collector made of, for example, aluminum foil, and then drying the applied paste.

[0235] The positive electrode is appropriately processed according to the battery to be used, for example, by cutting to a size appropriate for the intended battery, or by compressing with a roll press or the like to increase the electrode density.

[0236] The positive electrode mixture paste can be formed by adding a solvent to the positive electrode mixture and kneading the mixture. The positive electrode mixture can be formed by mixing the above-mentioned positive electrode active material in powder form with a conductive agent and a binder.

[0237] The conductive agent is added to the electrode to give it suitable electrical conductivity. The conductive agent is not particularly limited, but examples thereof include graphite (natural graphite, artificial graphite, expanded graphite, etc.) and carbon black materials such as acetylene black and ketjen black.

[0238] The binder plays a role of binding the positive electrode active material particles together. The binder used in this positive electrode mixture is not particularly limited, but examples thereof include polyvinylidene fluoride (PVDF), polytetrafluoroethylene (PTFE), fluororubber, ethylene propylene diene rubber, styrene butadiene, cellulose-based resin, polyacrylic acid, and the like.

[0239] In addition, activated carbon or the like may be added to the positive electrode mixture, and by adding activated carbon or the like, the electric double layer capacity of the positive electrode can be increased.

[0240] The solvent dissolves the binder and disperses the positive electrode active material, the conductive agent, the activated carbon, etc. in the binder. This solvent is not particularly limited, but for example, an organic solvent such as N-methyl-2-pyrrolidone can be used.

[0241] The mixing ratio of each material in the positive electrode mixture paste is not particularly limited. For example, when the solid content of the positive electrode mixture excluding the solvent is 100 parts by mass, the content of the positive electrode active material can be 60 parts by mass or more and 95 parts by mass or less, the content of the conductive agent can be 1 part by mass or more and 20 parts by mass or less, and the content of the binder can be 1 part by mass or more and 20 parts by mass or less, similar to the positive electrode of a general lithium ion secondary battery.

[0242] (Negative electrode) The negative electrode is a sheet-like member formed by applying a negative electrode mixture paste to the surface of a metal foil current collector such as copper, and then drying it. Although the components constituting the negative electrode mixture paste and their blending, the material of the current collector, and the like, of this negative electrode are different, they are formed in substantially the same manner as the positive electrode, and are subjected to various treatments as necessary, in the same manner as the positive electrode.

[0243] The negative electrode mixture paste is prepared by adding a suitable solvent to a negative electrode mixture, which is a mixture of a negative electrode active material and a binder, to form a paste.

[0244] The negative electrode active material may be, for example, a material containing lithium, such as metallic lithium or a lithium alloy, or an occlusion material capable of occluding and desorbing lithium ions.

[0245] The storage material is not particularly limited, and may be, for example, natural graphite, artificial graphite, a calcined organic compound such as phenolic resin, or a powder of a carbon material such as coke. When such a storage material is used as the negative electrode active material, a fluorine-containing resin such as PVDF may be used as the binder, as in the case of the positive electrode, and an organic solvent such as N-methyl-2-pyrrolidone may be used as the solvent for dispersing the negative electrode active material in the binder.

[0246] (Separator) The separator is sandwiched between the positive electrode and the negative electrode, and has the function of separating the positive electrode and the negative electrode and retaining the electrolyte. The separator may be, for example, a thin membrane such as polyethylene or polypropylene having a large number of fine pores, but is not particularly limited as long as it has the above function.

[0247] (Non-aqueous electrolyte) The non-aqueous electrolyte is a solution in which a lithium salt as a supporting salt is dissolved in an organic solvent. A non-aqueous electrolyte can be used as the non-aqueous electrolyte. For example, the non-aqueous electrolyte may be a solution in which a lithium salt as a supporting salt is dissolved in an organic solvent. The non-aqueous electrolyte may be a solution in which a lithium salt is dissolved in an ionic liquid. The ionic liquid refers to a salt that is composed of cations and anions other than lithium ions and that is liquid even at room temperature.

[0248] The organic solvent may be one selected from the group consisting of cyclic carbonates such as ethylene carbonate, propylene carbonate, butylene carbonate, and trifluoropropylene carbonate; chain carbonates such as diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, and dipropyl carbonate; ether compounds such as tetrahydrofuran, 2-methyltetrahydrofuran, and dimethoxyethane; sulfur compounds such as ethyl methyl sulfone and butane sultone; and phosphorus compounds such as triethyl phosphate and trioctyl phosphate, and may be used alone or in combination of two or more.

[0249] As the supporting salt, LiPF6, LiBF4, LiClO4, LiAsF6, LiN(CF3SO2)2, and composite salts thereof can be used.

[0250] The non-aqueous electrolyte may contain a radical scavenger, a surfactant, a flame retardant, etc., in order to improve the battery characteristics.

[0251] The non-aqueous electrolyte may be a solid electrolyte. The solid electrolyte has a property of being able to withstand high voltage. Examples of the solid electrolyte include inorganic solid electrolytes and organic solid electrolytes.

[0252] As the inorganic solid electrolyte, an oxide-based solid electrolyte, a sulfide-based solid electrolyte, or the like is used.

[0253] The oxide-based solid electrolyte is not particularly limited, and any oxide-based solid electrolyte that contains oxygen (O) and has lithium ion conductivity and electronic insulation can be used. Examples of oxide-based solid electrolytes include lithium phosphate (Li3PO4), Li3PO4N X , LiBON X , LiNbO3, LiTaO3, Li2SiO3, Li4SiO4-Li3PO4, Li4SiO4-Li3VO4, Li2O-B2O3-P2O5, Li2O-SiO2, Li2O-B2O3-ZnO, Li 1+X Al X Ti 2-X (PO4)3(0≦X≦1), Li 1+X Al X Ge 2-X (PO4)3(0≦X≦1), LiTi2(PO4)3, Li 3X La 2 / 3-X TiO3(0≦X≦2 / 3), Li5La3Ta2O 12 , Li7La3Zr2O 12 , Li6BaLa2Ta2O 12 , Li 3.6 S 0.6 P 0.4 Examples include O4.

[0254] The sulfide-based solid electrolyte is not particularly limited, and any electrolyte that contains sulfur (S) and has lithium ion conductivity and electronic insulation can be used. Examples of sulfide-based solid electrolytes include Li2S-P2S5, Li2S-SiS2, LiI-Li2S-SiS2, LiI-Li2S-P2S5, LiI-Li2S-B2S3, Li3PO4-Li2S-Si2S, Li3PO4-Li2S-SiS2, LiPO4-Li2S-SiS, LiI-Li2S-P2O5, and LiI-Li3PO4-P2S5.

[0255] As the inorganic solid electrolyte, materials other than those mentioned above may be used, for example, Li3N, LiI, Li3N-LiI-LiOH, etc. may be used.

[0256] The organic solid electrolyte is not particularly limited as long as it is a polymer compound exhibiting ion conductivity, and examples of the organic solid electrolyte that can be used include polyethylene oxide, polypropylene oxide, copolymers thereof, etc. The organic solid electrolyte may also contain a supporting salt (lithium salt).

[0257] (Characteristics of the Lithium-Ion Secondary Battery of the Present Embodiment) The lithium ion secondary battery of the present embodiment can have, for example, the above-described configuration, and has a positive electrode using the above-described positive electrode active material, so that a high initial discharge capacity and low positive electrode resistance can be obtained, resulting in high capacity and high output.

[0258] (Use of the secondary battery of this embodiment) Since the secondary battery of this embodiment has the above properties, it is suitable as a power source for small portable electronic devices (such as notebook personal computers and mobile phone terminals) that always require high capacity.

[0259] The secondary battery of this embodiment is also suitable as a battery for use as a power source for driving a motor that requires high output. As the size of a battery increases, it becomes difficult to ensure safety, and an expensive protection circuit is indispensable. However, the secondary battery of this embodiment has excellent safety, so not only does it become easier to ensure safety, but it also simplifies the expensive protection circuit and reduces costs. Furthermore, because it can be made smaller and has a higher output, it is suitable as a power source for transportation equipment that is subject to space restrictions. EXAMPLES

[0260] The present invention will be described in more detail below with reference to examples, although the present invention is not limited to the following examples.

[0261] The preparation conditions of the samples and the evaluation results in each of the examples and comparative examples will be described below.

[0262] [Example 1] 1. Preparation and Characterization of Precursors First, a precursor was prepared by the following procedure.

[0263] In all of the Examples and Comparative Examples, the precursors, the positive electrode active materials, and the secondary batteries were prepared using special-grade reagents manufactured by Wako Pure Chemical Industries, Ltd., unless otherwise specified.

[0264] (Crystallization process) The crystallization process was carried out in a step including a nucleation step and a particle growth step, as shown in Fig. 2. The nucleation step and the particle growth step will be described below.

[0265] (Nucleation process) (1) Preparation of the initial aqueous solution First, water was poured into a reaction tank (6 L) up to a volume of about 1.1 L, and the temperature inside the tank was set to 40° C. while stirring, and the mixed aqueous solution was controlled to be 40° C. in the following nucleation step and particle growth step. The temperatures of the initial aqueous solution and the mixed aqueous solution were controlled by adjusting the temperature of the heated water for the reaction tank provided around the reaction tank.

[0266] Then, an appropriate amount of 25% by mass ammonia water was added to the water in the reaction tank to adjust the ammonium ion concentration in the initial aqueous solution to 5 g / L.

[0267] The initial aqueous solution was further added with 64% sulfuric acid to adjust the pH to 6.4.

[0268] Nitrogen gas with an oxygen concentration of 9 ppm was supplied from a nitrogen gas cylinder at 4 L / min into the reaction tank as an oxygen-free gas to block oxygen, and the tank was purged to make the dissolved oxygen concentration of the initial aqueous solution 10% or less. The dissolved oxygen in the initial aqueous solution was confirmed with a dissolved oxygen meter (WA2017SD, manufactured by FUSO Corporation). The supply of nitrogen gas was continued until the particle growth process was completed, and it was confirmed that the dissolved oxygen concentration of the initial aqueous solution or the mixed aqueous solution was 10% or less until the particle growth process described below was completed.

[0269] (2) Preparation of mixed aqueous solution containing metal components Next, nickel sulfate and manganese sulfate were dissolved in water to prepare a metal component-containing mixed aqueous solution with a metal ion concentration of 1.9 mol / L. In this metal component-containing mixed aqueous solution, the mass ratio of each metal was adjusted to Ni:Mn=0.25:0.75.

[0270] (3) Preparation of pH-adjusted aqueous solution Sodium carbonate and ammonium carbonate were dissolved in water to prepare a pH-adjusted aqueous solution with a carbonate ion concentration of 2.2 mol / L. The sodium carbonate and ammonium carbonate in the pH-adjusted aqueous solution were added so that the substance amount ratio was 9:2.

[0271] (4) Addition of the mixed aqueous solution containing metal components to the initial aqueous solution and mixing The metal component-containing mixed aqueous solution was added to the initial aqueous solution in the reaction vessel at a rate of 10.3 mL / min to obtain a mixed aqueous solution.

[0272] (5) Agitation in the reaction vessel The stirring power required for the reaction vessel is 2.7kW / m 3 It was made so that:

[0273] When the metal component-containing mixed aqueous solution was added, a pH-adjusting aqueous solution was added at the same time to control the pH value of the mixed aqueous solution in the reaction vessel so as not to exceed 6.4 (nucleation pH value), and crystallization was carried out for 4 minutes to carry out the nucleation process. During the nucleation process, the pH value of the mixed aqueous solution fluctuated within a range of 0.2 above and below the central value (set pH value) of 6.2.

[0274] (Particle growth process) In the particle growth step, the same metal component-containing mixed aqueous solution and pH-adjusted aqueous solution as in the nucleation step were used. The procedure for the particle growth step is explained below.

[0275] (1) Adjustment of pH of the mixed solution In the particle growth step, first, a pH-adjusting aqueous solution was added to the mixed aqueous solution obtained in the nucleation step to adjust the pH value to 7.1 (based on a liquid temperature of 40° C.).

[0276] (2) Addition of a mixed aqueous solution containing a metal component to the mixed aqueous solution, and mixing The metal component-containing mixed aqueous solution was added to the mixed aqueous solution after the pH adjustment at a rate of 10.3 mL / min.

[0277] At this time, the amounts of the metal component-containing mixed aqueous solution and the pH adjusting aqueous solution added were controlled so that the pH value of the mixed aqueous solution did not exceed 7.1 at a reaction temperature of 40°C.

[0278] After maintaining this state for 110 minutes, stirring was stopped to terminate the crystallization.

[0279] The product obtained in the particle growth step was washed with water, filtered, and dried to obtain precursor particles (washing and drying steps).

[0280] In the particle growth process, the pH value was controlled by adjusting the supply amount of the pH-adjusted aqueous solution using a pH controller, and the pH value of the mixed aqueous solution fluctuated within a range of 0.2 above or below the central value (set pH value) of 6.9.

[0281] In addition, the ammonium ion concentration in the mixed aqueous solution was maintained at 5 g / L in the nucleation step and the particle growth step.

[0282] (Precursor evaluation) The obtained precursor was dissolved in an inorganic acid and then chemically analyzed by ICP atomic emission spectrometry, and it was confirmed that the composition was a carbonate having Ni:Mn=0.25:0.75.

[0283] In addition, the average particle size of the precursor particles is d 50 The average particle size was measured using a laser diffraction scattering type particle size distribution measuring device (Microtrack HRA, manufactured by Nikkiso Co., Ltd.), and it was confirmed that the average particle size was 5.5 μm.

[0284] Next, the obtained precursor particles were observed with a SEM (Hitachi High-Technologies Corporation, scanning electron microscope S-4700) (magnification: 5000 times), and it was confirmed that the obtained precursor particles were approximately spherical and had a nearly uniform particle size. In this case, in Table 1, a form having spherical properties is evaluated as ◯, and a form not having spherical properties is evaluated as △.

[0285] The results of SEM observation of the obtained precursor are shown in FIG.

[0286] 2. Production and evaluation of positive electrode active materials Next, the obtained precursor was used to produce a positive electrode active material and evaluate it.

[0287] (Production of positive electrode active material) The precursor was heat-treated in an air stream (oxygen: 21% by volume) at 500° C. for 2 hours to convert it into composite oxide particles, which were heat-treated particles, and then recovered.

[0288] Next, the heat-treated particles were mixed with a lithium compound to obtain a lithium mixture.

[0289] Specifically, lithium carbonate was weighed so that the resulting lithium mixture would have a Li / Me ratio of 0.5, and was mixed with the heat-treated particles to prepare a lithium mixture.

[0290] Mixing was performed using a shaker mixer device (TURBULA Type T2C, manufactured by WAB).

[0291] The obtained lithium mixture was calcined at 500°C for 5 hours in the air (oxygen: 21% by volume), then heated to 950°C at a temperature increase rate of 3°C / min and held at that temperature for 7 hours for firing, cooled to room temperature at a temperature decrease rate of 3°C / min, and then crushed to obtain a positive electrode active material.

[0292] The composition of the obtained positive electrode active material was expressed as Li:Ni:Mn=0.50:0.25:0.75.

[0293] (Evaluation of Positive Electrode Active Material) The particle size distribution of the obtained positive electrode active material was measured in the same manner as in the case of the precursor particles, and it was confirmed that the average particle size was 8.9 μm.

[0294] In addition, a cross-section of the positive electrode active material was observed by SEM.

[0295] The surface of the positive electrode active material was observed in the same manner as for the precursor.

[0296] It was confirmed that the secondary particles were covered with plate-like particles, and the sphericity of the precursor was maintained. In this case, in Table 1, the sphericity was evaluated as ◯, and the non-sphericity was evaluated as △.

[0297] FIG. 4 shows the results of SEM observation of the obtained positive electrode active material.

[0298] Furthermore, the tap density was measured and found to be 2.1 g / cm 3 It was confirmed that this was the case.

[0299] The tap density was measured by filling a 20 mL measuring cylinder with the obtained positive electrode active material, and then densely filling the measuring cylinder by repeatedly subjecting the cylinder to free fall from a height of 2 cm 500 times.

[0300] 3. Manufacturing and evaluation of lithium-ion secondary batteries [Secondary battery manufacturing] Using the obtained positive electrode active material, a 2032 type coin battery was fabricated and evaluated.

[0301] The configuration of the produced coin-type battery will be described with reference to Figure 5. Figure 5 is a schematic cross-sectional view of the coin-type battery.

[0302] As shown in FIG. 5, the coin battery 10 is composed of a case 11 and an electrode 12 housed within the case 11.

[0303] Case 11 has a hollow positive electrode can 111 with one end open, and a negative electrode can 112 placed in the opening of positive electrode can 111, and is configured so that when negative electrode can 112 is placed in the opening of positive electrode can 111, a space for accommodating electrode 12 is formed between negative electrode can 112 and positive electrode can 111.

[0304] Electrode 12 consists of a positive electrode 121, a separator 122, and a negative electrode 123, which are stacked in this order and are housed in case 11 so that positive electrode 121 contacts the inner surface of positive electrode can 111 and negative electrode 123 contacts the inner surface of negative electrode can 112.

[0305] Case 11 is provided with gasket 113, which fixes positive electrode can 111 and negative electrode can 112 so as to maintain an electrically insulated state between them. Gasket 113 also has the function of sealing the gap between positive electrode can 111 and negative electrode can 112 to provide an airtight and liquidtight barrier between the inside of case 11 and the outside.

[0306] This coin-type battery 10 was produced as follows. First, 52.5 mg of the obtained positive electrode active material, 15 mg of acetylene black, and 7.5 mg of polytetrafluoroethylene resin (PTFE) were mixed together with a solvent (N-methyl-2-pyrrolidone), and pressed at a pressure of 100 MPa to produce a positive electrode 121 with a diameter of 11 mm and a thickness of 100 μm. The produced positive electrode 121 was dried in a vacuum dryer at 120° C. for 12 hours. Using this positive electrode 121, negative electrode 123, separator 122, and electrolyte, a coin-type battery 10 was produced in a glove box in an Ar atmosphere with a dew point controlled at −80° C.

[0307] The negative electrode 123 was made of graphite powder with an average particle size of about 20 μm punched into a disk shape with a diameter of 14 mm and a negative electrode sheet in which polyvinylidene fluoride was applied to copper foil. A polyethylene porous film with a film thickness of 25 μm was used for the separator 122. An equal mixture of ethylene carbonate (EC) and diethyl carbonate (DEC) with 1M LiClO4 as the supporting electrolyte (manufactured by Toyama Pharmaceutical Co., Ltd.) was used as the electrolyte.

[0308] [Battery evaluation] The performance of the obtained coin-type battery 10 was evaluated by the initial discharge capacity, which was defined as follows.

[0309] The initial discharge capacity was determined by leaving the coin battery 10 for about 24 hours after its production, and after the open circuit voltage OCV stabilized, charging the battery to a cutoff voltage of 5.0 V at a current density of 0.05 C (270 mA / g is defined as 1 C) to the positive electrode, and then resting for 1 hour. The capacity at the time of discharging the battery to a cutoff voltage of 3.0 V was defined as the initial discharge capacity.

[0310] When a battery evaluation was carried out on a coin-type battery having a positive electrode formed using the above positive electrode active material, the initial discharge capacity was 142 mAh / g.

[0311] The properties of the precursor and the positive electrode active material obtained in this example, and the evaluation results of the coin-type battery produced using this positive electrode active material are shown in Table 1. The same contents are also shown in the same table for the following Comparative Examples 1 to 3.

[0312] [Example 2] Mixing power required: 6.4kW / m 3 A precursor, a positive electrode active material, and a secondary battery were produced and evaluated in the same manner as in Example 1, except for the above.

[0313] [Comparative Example 1] A precursor, a positive electrode active material, and a secondary battery were produced and evaluated in the same manner as in Example 1, except that the gas blown into the reaction tank during the production of the precursor was changed to air. It was also confirmed by the same method as in Example 1 that the dissolved oxygen concentration of the initial aqueous solution or the mixed aqueous solution exceeded 10% from the start of the nucleation step to the end of the particle growth step. The results are shown in Table 1.

[0314] [Comparative Example 2] Mixing power required: 0.8kW / m 3 A precursor, a positive electrode active material, and a secondary battery were produced and evaluated in the same manner as in Example 1, except for the above.

[0315] [Comparative Example 3] A precursor, a positive electrode active material, and a secondary battery were produced and evaluated in the same manner as in Example 1, except that sodium carbonate was used as the pH-adjusted aqueous solution.

[0316] Table 1 shows the products, carbonate ion donors, stirring power requirements, average particle diameters d50 and sphericity of the precursor and positive electrode active material, as well as the tap density of the positive electrode active material and the initial discharge capacity of the secondary battery in the examples and comparative examples.

[0317] [Table 1]

[0318] From the results in Table 1, it was confirmed that the positive electrode active materials obtained from the precursor particles of Examples 1 and 2 had high tap density due to their spherical shape and small particle size. It was also confirmed that the improved tap density and the increased ratio of active material per electrode resulted in improved discharge capacity.

[0319] It was also confirmed that the secondary batteries manufactured using the positive electrode active materials shown in Comparative Examples 1-3 had inferior initial discharge capacities compared to the cases of Examples 1-2.

[0320] In Comparative Example 1, the nucleation step and particle growth step were performed in an oxygen-containing atmosphere, and the dissolved oxygen in the initial aqueous solution and the mixed aqueous solution reacted with the nickel and manganese contained in the initial aqueous solution and the mixed aqueous solution to generate and aggregate amorphous fine particles, which made the precursor and the positive electrode active material particles porous. This is thought to be the reason why the tap density and initial discharge capacity were lower than those of the Examples.

[0321] In addition, in Comparative Example 2, the stirring power required is low, so it is believed that the precursors are aggregated. Therefore, the overall shape of the aggregated particles is not spherical, and it is believed that the tap density and initial discharge capacity are lower than those of the Examples. In addition, since the particles become coarse due to aggregation, the synthesis of the positive electrode active material does not proceed uniformly throughout the particles, and it is believed that the initial discharge capacity is lowered.

[0322] In addition, in Comparative Example 3, since ammonium ions were not supplied to the initial aqueous solution and the mixed aqueous solution, multiple fine particles were generated during nucleation, and the resulting nuclei were considered to be in the form of aggregates of multiple primary particles. This is considered to be the reason why the tap density and initial discharge capacity were lower than those of the Examples.

[0323] Although the embodiments and examples of the present invention have been described in detail above, those skilled in the art will easily understand that many modifications are possible without substantially departing from the novel features and effects of the present invention. Therefore, all such modifications are intended to be included within the scope of the present invention.

[0324] For example, a term described at least once in the specification or drawings together with a different term having a broader or synonymous meaning can be replaced with the different term anywhere in the specification or drawings. The configurations and operations of the positive electrode active material precursor for lithium ion secondary batteries and the method for producing the same, and the positive electrode active material for lithium ion secondary batteries and the method for producing the same are not limited to those described in the embodiments and examples of the present invention, and various modifications are possible. [Explanation of symbols]

[0325] 10 coin cell battery, 11 case, 12 electrode, 111 positive electrode can, 112 negative electrode can, 113 gasket, 121 positive electrode, 122 separator, 123 negative electrode

Claims

1. A positive electrode active material precursor for a lithium ion secondary battery, comprising: The precursor is a nickel manganese carbonate compound having a substance ratio of Ni:Mn:M=x:y:t (wherein, x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2 are satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, and W), It is composed of secondary particles (excluding porous particles) formed by agglomeration of multiple primary particles, the primary particles have the crystallinity of the carbonate, The secondary particles have spherical shape, The secondary particles have an average particle size of 3 to 15 μm.

2. A positive electrode active material for a lithium ion secondary battery comprising a lithium metal composite oxide, The lithium metal composite oxide has a substance ratio of Li:Ni:Mn:M=α:x:y:t (0.48≦α≦0.65, x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2, M is an additive element and is one or more elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, and W), and has a spinel crystal structure, It is composed of secondary particles (excluding porous particles) formed by agglomeration of multiple primary particles, The secondary particles have spherical shape, The positive electrode active material for a lithium ion secondary battery is characterized in that the secondary particles have an average particle size of 3 to 15 μm.

3. Tap density is 1.5 g / cm ３ The positive electrode active material for a lithium ion secondary battery according to claim 2 , characterized in that

4. A method for producing a positive electrode active material precursor for a lithium ion secondary battery, comprising: The method includes a crystallization step of generating nuclei in a mixed aqueous solution obtained by mixing an initial aqueous solution containing an alkaline substance of carbonate and an ammonium ion donor, an aqueous solution containing nickel as a metal component, and an aqueous solution containing manganese as a metal component in the presence of carbonate ions, and growing the generated nuclei; The crystallization step includes controlling the pH value of the mixed aqueous solution to 5.4 or more and 9.0 or less at a reaction temperature of 40° C., In the crystallization step, the stirring power required for the mixed aqueous solution is set to 1.0 kW / m ３ More than 10.0kW / m ３ Adjust it within the following range: The crystallization step includes controlling the dissolved oxygen concentration in the mixed aqueous solution to 10% or less, a method for producing a precursor of a positive electrode active material for a lithium ion secondary battery, the method being characterized in that the precursor is a nickel manganese carbonate composite composed of Ni:Mn:M=x:y:t (wherein x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2 are satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, and W) in terms of an amount of substance ratio.

5. A method for producing a positive electrode active material precursor for a lithium ion secondary battery, comprising: a nucleation step of generating nuclei in a mixed aqueous solution obtained by mixing an initial aqueous solution containing an alkaline substance of carbonate and an ammonium ion donor, an aqueous solution containing nickel as a metal component, and an aqueous solution containing manganese as a metal component in the presence of carbonate ions; a particle growth step of growing the nuclei generated in the nucleation step, In the nucleation step, the pH values ​​of the initial aqueous solution and the mixed aqueous solution are controlled to be 5.4 or more and 7.5 or less at a reaction temperature of 40° C., The nucleation step includes controlling the dissolved oxygen concentration in the mixed aqueous solution to 10% or less, In the nucleation step, the stirring power required for the initial aqueous solution and the mixed aqueous solution is set to 1.0 kW / m ３ More than 10.0kW / m ３ Adjust it within the following range: a method for producing a precursor of a positive electrode active material for a lithium ion secondary battery, the method being characterized in that the precursor is a nickel manganese carbonate composite composed of Ni:Mn:M=x:y:t (wherein x+y+t=1, 0.2≦x≦0.3, 0.7≦y≦0.8, 0≦t≦0.2 are satisfied, and M is one or more additive elements selected from Mg, Ca, Al, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, and W) in terms of an amount of substance ratio.

6. The ammonium ion donor is at least one selected from an ammonium carbonate aqueous solution, an ammonia water, an ammonium chloride aqueous solution, and an ammonium sulfate aqueous solution; 6. The method for producing a positive electrode active material precursor for a lithium ion secondary battery according to claim 4, wherein the alkaline substance of the carbonate is at least one selected from the group consisting of sodium carbonate, sodium hydrogen carbonate, and potassium carbonate.

7. The particle growth step is a step of adding and mixing an aqueous solution containing nickel as a metal component and an aqueous solution containing manganese as a metal component in the presence of carbonate ions to the mixed aqueous solution obtained after the nucleation step, In the particle growth step, the pH value of the mixed aqueous solution is controlled to be 6.0 or more and 9.0 or less at a reaction temperature of 40° C., and the pH value is higher than the pH values ​​of the initial aqueous solution and the mixed aqueous solution in the nucleation step; 6. The method for producing a positive electrode active material precursor for a lithium ion secondary battery according to claim 5, wherein the concentration of ammonium ions in the mixed aqueous solution during the particle growth step is 1 g / L or more and 20 g / L or less.

8. The method for producing a positive electrode active material precursor for a lithium ion secondary battery according to claim 5 or 7, wherein the temperature of the mixed aqueous solution is maintained at 30°C or higher in the nucleation step.

9. A heat treatment step of heat-treating the positive electrode active material precursor for a lithium ion secondary battery obtained by the method for producing a positive electrode active material precursor for a lithium ion secondary battery according to any one of claims 4 to 8 at a temperature of 80°C or higher and 600°C or lower; a mixing step of adding and mixing a lithium compound to the particles obtained by the heat treatment step to form a lithium mixture; A calcination step of calcining the lithium mixture in an oxidizing atmosphere at a temperature of 600° C. or more and 1000° C. or less, a ratio (Li / Me) of a sum of substance amounts of metals other than lithium (Me) in the lithium mixture to a substance amount of lithium (Li) is 0.48 or more and 0.65 or less.

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