JP2019032941A - Method of deciding manufacturing condition of composite particle for positive electrode and method of manufacturing composite particle for positive electrode - Google Patents

Abstract

To provide a method of deciding manufacturing conditions of composite particles for positive electrode capable of increasing bonding force between positive electrode active material particles, each having a surface of a core part coated with a surface layer of a different material from the core part, and conductive assistant particles while suppressing the positive electrode active material particles from being damaged, and a method of manufacturing the composite particles for positive electrode.SOLUTION: A method of deciding manufacturing conditions of composite particles 10 for positive electrode has: a manufacturing process (S2) of setting a peripheral speed of a rotary body 120 and a processing time of mixing processing (S1) and manufacturing the composite particles for positive electrode; a conductivity measuring process (S3) of measuring conductivity of the composite particles for positive electrode; a pH measuring process (S5) of measuring pH of a solution having the composite particles for positive electrode dispersed in water; and determination processes (S4, S6) of determining, based upon results obtained through the conductivity measuring process and pH measuring process, whether the peripheral speed of the rotary body and the processing time of the mixing processing set in the manufacturing process indicate effective set values.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a method for determining production conditions for composite particles for positive electrode and a method for producing composite particles for positive electrode.

  Secondary batteries are becoming increasingly important as on-vehicle power supplies. The secondary battery includes, for example, a positive electrode in which a layer of a positive electrode active material capable of reversibly occluding and releasing metal ions such as lithium ions is formed on a positive electrode current collector. The positive electrode active material may be used as a mixture with a conductive auxiliary agent in order to ensure conductivity.

  For example, the following Patent Document 1 discloses a method of producing composite particles for positive electrodes by mixing powders of positive electrode active material particles and powders of conductive additive particles with a mixing device that mixes powders in a dry manner. Has been. According to this method, the mechanical energy at the time of mixing is made to act on each powder, The positive electrode active material particle and the conductive support agent particle are combined by mechanochemical reaction. According to the mechanochemical reaction, the binding force between the positive electrode active material particles and the conductive auxiliary particles can be increased. Further, it is not necessary to add a binder in order to obtain a binding force between the positive electrode active material particles and the conductive auxiliary particles. For this reason, the internal resistance of the secondary battery can be reduced.

  In addition, as positive electrode active material particles used for secondary batteries, for example, as disclosed in Patent Document 2 below, core / shell particles in which a surface layer made of a material different from the core part is formed on the surface of the core part have been developed. Has been. Such core / shell particles have characteristics such as cycle characteristics, durability, mechanical strength, solvent resistance (electrolytic solution resistance), oxidation resistance, etc., compared to positive electrode active material particles composed of only the core portion. (Performance) etc. can be improved.

JP 2007-220510 A Japanese Patent No. 5905086

  The mechanical energy acting on the powder by the mixing apparatus varies depending on the peripheral speed of the rotating body and the processing time of the mixing process. When the peripheral speed of the rotating body is slow or the processing time is short, the mechanical energy acting on the powder is small, so that a sufficient mechanochemical reaction cannot be obtained, and the positive electrode active material particles and the conductive auxiliary agent particles are combined. Power is weakened. Thereby, the electrical conductivity of the composite particles for positive electrode is lowered, and the required performance of the battery cannot be obtained.

  On the other hand, when the peripheral speed of the rotating body is excessively increased in order to obtain a sufficient mechanochemical reaction, the surface layer is damaged in the positive electrode active material particles having the surface layer coated on the surface of the core as in Patent Document 2. And may peel off.

  An object of the present invention is to provide a positive electrode capable of increasing the binding force between the positive electrode active material particles and the conductive auxiliary particles while suppressing damage to the positive electrode active material particles whose surface is coated with a surface layer made of a material different from that of the core portion. It is providing the determination method of the manufacturing conditions of the composite particle for laser, and the manufacturing method of the composite particle for positive electrodes.

  The method for determining the manufacturing condition of the composite particles for positive electrode according to the present invention that achieves the above object comprises a material different from the core part on the surface of the core part in the accommodating part of the mixing device provided with the rotating body in the accommodating part. The positive electrode active material particles and the conductive auxiliary agent are mixed by charging the powder of the positive electrode active material particles coated with the surface layer and the powder of the conductive auxiliary agent particles, rotating the rotating body and mixing them in a dry manner. This is a method for determining production conditions for producing composite particles for a positive electrode combined with particles. The method for determining the manufacturing conditions includes a manufacturing process for manufacturing the composite particles for positive electrode by setting the peripheral speed of the rotating body and the processing time of the mixing process, and a conductivity measuring process for measuring the conductivity of the composite particles for positive electrode. The peripheral speed of the rotating body set in the manufacturing process based on the pH measurement step for measuring the pH of the solution in which the composite particles for positive electrode are dispersed in water, and the results obtained by the conductivity measurement step and the pH measurement step A determination step of determining whether or not the processing time of the mixing process is an effective set value.

  The manufacturing method of the composite particles for positive electrodes according to the present invention that achieves the above object includes a surface layer made of a material different from the core portion on the surface of the core portion in the housing portion of the mixing device provided with a rotating body in the housing portion. The coated positive electrode active material particle powder and conductive auxiliary agent particle powder are charged, and a mixing process is performed in which the rotating body is rotated and mixed in a dry manner to obtain the positive electrode active material particles and the conductive auxiliary agent particles. It is the manufacturing method of the composite particle for positive electrodes which manufactures the composite particle for positive electrodes combined. This positive electrode composite particle manufacturing method uses the set values made effective by the method for determining the positive electrode composite particle manufacturing conditions as the peripheral speed of the rotating body and the processing time of the mixing process.

  According to the method for determining production conditions for composite particles for positive electrode according to the present invention, in the production of composite particles for positive electrode in which the powder of the positive electrode active material particles and the powder of the conductive additive particles are dry mixed, Tolerances for speed and processing time of the mixing process can be determined. In particular, in a positive electrode active material particle having a core portion and its surface layer, an appropriate peripheral speed capable of suppressing damage to the surface layer can be obtained. As a result, the internal resistance of the battery can be increased by increasing the bonding force between the positive electrode active material particles and the conductive auxiliary particles while suppressing damage to the surface layer of the positive electrode active material particles, regardless of the configuration and material design of the mixing device. Manufacturing conditions that can be reduced can be determined.

  According to the method for producing a composite particle for positive electrode according to the present invention, the positive electrode active material particle and the conductive auxiliary agent particle are suppressed while suppressing damage to the surface layer of the positive electrode active material particle without depending on the configuration of the mixing device or the material design. The internal resistance of the battery can be reduced by increasing the binding force.

It is a cross-sectional schematic diagram which shows one Embodiment of the composite particle for positive electrodes. It is the cross-sectional schematic which shows an example of a mixing apparatus. It is a flowchart which shows the determination method of the manufacturing conditions of the composite particle for positive electrodes. The conceptual diagram which shows the relationship between the pressure added to the composite particle for positive electrodes, and the electrical conductivity of the composite particle for positive electrodes obtained when measuring electrical conductivity using the composite particle for positive electrodes manufactured on the conditions from which the peripheral speed of a rotary body differs It is. The conceptual diagram which shows the relationship between the pressure added to the composite particle for positive electrodes, and the electrical conductivity of the composite particle for positive electrodes obtained when the electrical conductivity is measured using the composite particle for positive electrodes manufactured on the conditions from which the process time of a mixing process differs It is. It is a conceptual diagram which shows the relationship between the time which passed since throwing the composite particle for positive electrodes into water, and pH value.

  Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings. In addition, the following description does not limit the meaning of the technical scope and terms described in the claims. In addition, the dimensional ratios in the drawings are exaggerated for convenience of explanation, and may differ from actual ratios.

<Composite particles for positive electrode>
FIG. 1 is a schematic cross-sectional view showing one embodiment of composite particle 10 for positive electrode.

  As shown in FIG. 1, the positive electrode composite particle 10 includes positive electrode active material particles 11 and conductive auxiliary agent particles 12 that coat the surfaces of the positive electrode active material particles 11. The composite particle 10 for positive electrode can improve electroconductivity compared with the positive electrode active material particle 11 single-piece | unit by couple | bonding the conductive support agent particle | grains 12 with the surface of the positive electrode active material particle 11. FIG.

(Positive electrode active material particles)
As illustrated in FIG. 1, the positive electrode active material particle 11 includes a core portion 11 a and a surface layer 11 b that covers the surface of the core portion 11 a. The surface layer 11b preferably covers the entire surface of the core portion 11a. The positive electrode active material particles 11 of the present embodiment are not particularly limited as long as the surface layer 11b is formed on the surface of the core portion 11a (hereinafter also simply referred to as “core / shell particles”). Conventionally known core / shell particles can be used. Conventionally, characteristics (performance) such as cycle characteristics, durability, mechanical strength, solvent resistance (electrolytic solution resistance), oxidation resistance, etc., compared to positive electrode active material particles composed only of existing positive electrode active material A wide variety of core / shell particles have been developed for the purpose of further improving the above.

  The method for determining the manufacturing conditions and the manufacturing method of the composite particle for positive electrode 10 according to the present embodiment, which will be described later, can correspond to any of a wide variety of such core-shell particles. That is, the bonding strength between the core portion 11a and the surface layer 11b of various core / shell particles is not uniform and varies. The method for determining the manufacturing conditions and the manufacturing method of the composite particles for positive electrode 10 according to the present embodiment are such that the surface layer 11b does not crack or peel according to the difference in bonding strength, and the bonding of the conductive auxiliary agent particles 12 occurs. It can increase your power.

The core portion 11a of the positive electrode active material particle 11 is not particularly limited, and an existing positive electrode active material can be appropriately used according to the intended use. For example, LiMn ₂ O ₄ , LiCoO ₂ , LiNiO ₂ , Li (Ni—Mn—Co) O ₂ , and lithium-transition metal composite oxides in which a part of these transition metals is substituted with other elements , Lithium-transition metal phosphate compounds, lithium-transition metal sulfate compounds, and the like. In some cases, two or more positive electrode active materials may be used in combination. Preferably, a lithium-transition metal composite oxide is used as the positive electrode active material from the viewpoint of capacity and output characteristics. More preferably, a composite oxide containing lithium and nickel is used, and more preferably Li (Ni—Mn—Co) O ₂ , and a part of these transition metals substituted with other elements (hereinafter referred to as “lower”). Simply referred to as “NMC composite oxide”). The NMC composite oxide has a layered crystal structure in which lithium atomic layers and transition metal (Mn, Ni, and Co are arranged in order) atomic layers are alternately stacked via oxygen atomic layers. One Li atom is contained per one atom of the transition metal M, and the amount of Li that can be taken out is twice that of the spinel-based lithium manganese oxide, that is, the supply capacity is doubled, and a high capacity can be obtained.

  As described above, the NMC composite oxide includes a composite oxide in which a part of the transition metal element is substituted with another metal element. Other elements in that case include Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, Cr, Fe, B, Ga, In, Si, Mo, Y, Sn, V, Cu , Ag, Zn and the like. Preferred are Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr. More preferred are Ti, Zr, P, Al, Mg, and Cr, and further preferred are Ti, Zr, Al, Mg, and Cr from the viewpoint of improving cycle characteristics.

Since the NMC composite oxide has a high theoretical discharge capacity, it preferably has a composition represented by the general formula (1): LiaNibMncCodMxO ₂ . In the general formula (1), a, b, c, d and x are 0.9 ≦ a ≦ 1.2, 0 <b <1, 0 <c ≦ 0.5, 0 <d ≦ 0.5, 0 ≦ x ≦ 0.3 and b + c + d = 1 are satisfied. M is at least one element selected from Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr, and Cr. Here, a represents the atomic ratio of Li, b represents the atomic ratio of Ni, c represents the atomic ratio of Co, d represents the atomic ratio of Mn, and x represents the atomic ratio of M. Represents. From the viewpoint of cycle characteristics, it is preferable that 0.4 ≦ b ≦ 0.6 in the general formula (1). The composition of each element can be measured by, for example, inductively coupled plasma (ICP) emission spectrometry.

  In general, nickel (Ni), cobalt (Co), and manganese (Mn) are known to contribute to capacity and output characteristics from the viewpoint of improving the purity of materials and improving electronic conductivity. Ti or the like partially replaces the transition metal in the crystal lattice. From the viewpoint of cycle characteristics, it is preferable that a part of the transition element is substituted with another metal element, and it is particularly preferable that 0 <x ≦ 0.3 in the general formula (1). The crystal structure is stabilized by dissolving at least one selected from the group consisting of Ti, Zr, Nb, W, P, Al, Mg, V, Ca, Sr and Cr. As a result, it is considered that even when charging and discharging are repeated, a decrease in battery capacity can be prevented and excellent cycle characteristics can be realized.

In a more preferred embodiment, in the general formula (1), b, c and d are 0.49 ≦ b ≦ 0.51, 0.29 ≦ c ≦ 0.31, 0.19 ≦ d ≦ 0.21. It is preferable from the viewpoint of improving the balance between capacity and life characteristics. For example, LiNi ₀ . ₅ Mn _0.3 Co _0.2 O ₂ is a unit weight compared to LiCoO ₂ , LiMn ₂ O ₄ , LiNi _1/3 Mn _1/3 Co _1/3 O _2, etc., which have been proven in general consumer batteries. The per unit capacity is large, and the energy density can be improved. Therefore, it has the advantage that a compact and high capacity battery can be produced, which is preferable from the viewpoint of cruising distance. It should be noted that LiNi ₀ . ₈ Co ₀ . ₁ Al ₀ . ₁ O ₂ is more advantageous, but there are difficulties in life characteristics. In contrast, LiNi ₀ . ₅ Mn ₀ . ₃ Co ₀ . ₂ O ₂ has life characteristics as excellent as LiNi _1/3 Mn _1/3 Co _1/3 O ₂ .

  Moreover, the average particle diameter of the core part 11a of the positive electrode active material particles 11 contained in the positive electrode active material layer is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 to 20 μm from the viewpoint of increasing the output. . In the present specification, the “particle diameter” means the positive electrode active material particle 11 or the core portion 11a observed using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). It means the maximum distance among the distances between any two points on the contour line (observation surface). As the value of “average particle diameter”, the average particle diameter of particles observed in several to several tens of fields using an observation means such as a scanning electron microscope (SEM) or a transmission electron microscope (TEM). The calculated value shall be adopted. The particle diameters and average particle diameters of other components can be defined in the same manner. In addition, the thickness of the surface layer 11b can be easily calculated as a difference between the average particle diameter of the positive electrode active material particles 11 and the average particle diameter of the core portion 11a.

  The method for producing the core portion 11a of the positive electrode active material particles 11 is not particularly limited, and a wide variety of existing methods for producing positive electrode active material particles other than the core / shell particles can be used. For example, various known methods such as a coprecipitation method and a spray drying method can be selected and prepared. The coprecipitation method is preferably used because the composite oxide is easy to prepare. For example, a nickel-cobalt-manganese composite hydroxide is produced by a coprecipitation method. Thereafter, the nickel-cobalt-manganese composite hydroxide and the lithium compound are mixed and fired to obtain the core portion 11a made of the NMC composite oxide.

The surface layer 11b of the positive electrode active material particle 11 is not particularly limited as long as it is made of a material different from that of the core portion 11a, and an existing surface layer material of core / shell particles can be appropriately used depending on the intended use. . Some examples of the existing surface layer materials are shown below, but the present embodiment is not limited to these examples. For example, as the surface layer material, a material in which a part of a metal element (for example, Mn, Ni, Co, etc.) in the positive electrode active material constituting the core portion 11a is partially substituted with another element can be cited. Moreover, the material which inserted (dope) another element in crystal structures, such as the rock salt type | mold layered structure of the positive electrode active material material which comprises the core part 11a, a zigzag type | mold layered structure, and a spinel type | mold layered structure, is mentioned. Examples of the elements that substitute or insert (dope) part of the metal elements in the positive electrode active material include, for example, Li, B, P, N, Mg, Al, Ca, V, Ti, Cr, Ni, Mn, Examples of the element include Fe, Co, Cu, Zn, Sr, Zr, Nb, Mo, and Sn. These elements may be used alone or in combination of two or more. Furthermore, examples of the surface layer material include a material made of a mixture or composite oxide of a positive electrode active material or a part thereof (element or compound, etc.) constituting the core portion 11a and an inorganic N-based oxide. Here, examples of N include elements such as Mg, Ti, Fe, Cu, Al, Ca, Ba, Y, Sn, Sb, Na, Zn, Zr, and Si. These elements may be used alone or in combination of two or more. Examples of the surface layer material include the above inorganic N-based oxides such as Al ₂ O ₃ , nitrides, oxynitrides, and the like, or a combination of these. Alternatively, as the surface layer material, fluorination in which 40 to 70% of hydrogen atoms in the R portion in the compound represented by ROLi (R is a linear alkyl group or a linear acyl group) is substituted with a fluorine atom. Examples include materials containing compounds. Of course, a surface layer material constituting the surface layer 11b of the positive electrode active material particles 11 other than the above may be used. The composition of each element of the surface layer 11b can be measured by, for example, inductively coupled plasma (ICP) emission analysis.

  The method for forming the surface layer 11b on the core portion 11a is not particularly limited, and the surface layer forming method in the existing method for producing core / shell particles can be used. Some examples of the surface layer forming method in the existing core / shell particle manufacturing method will be described below, but the present embodiment is not limited to these examples. For example, there is a method of forming the surface layer 11b by covering the core portion 11a with the existing surface layer material as described above or a solution containing the same as the surface of the core portion 11a. As such a method, for example, an existing forming method such as a dipping / sintering method, a coating / sintering method, a kneading (sintering) method, a spraying / sintering method, a thermal spraying method, or a CVD method can be applied. Alternatively, a method of forming the surface (modified) layer 11b by modifying the surface layer portion of the core portion 11a using the existing surface layer material as described above or a part thereof may be used. As such a method, for example, an existing forming method such as a method of inserting (doping) a metal or a metal compound (oxide, nitride, oxynitride, etc.) (for example, an ion implantation method, an alloy method, a diffusion method, etc.) Is applicable. The surface layer 11b may be a single layer (single layer) or may be composed of two or more layers.

  Further, the thickness (coating thickness or modified depth) of the surface layer 11b of the positive electrode active material particles 11 depends on the purpose of forming the surface layer 11b (for example, cycle characteristics, durability, mechanical strength, solvent resistance (resistance to resistance). What is necessary is just to select suitably from the existing thickness range optimized for every characteristic improvement purpose (electrolyte property), oxidation resistance, etc.).

  Further, the average particle diameter of the positive electrode active material particles 11 (core portion 11a + surface layer 11b) contained in the positive electrode active material layer is not particularly limited, but is preferably 1 to 100 μm, more preferably 1 from the viewpoint of high output. ˜20 μm.

(Conductive aid particles)
The conductive auxiliary agent particles 12 are a carbon material blended to improve the conductivity of the positive electrode active material particles 11. Examples of the carbon material include acetylene black, furnace black, carbon black, channel black, graphite, and carbon nanotube. Among these, it is more preferable to use carbon black because of its excellent conductivity.

  Moreover, the carbon material to be used can be appropriately changed according to the method used when coating the active material. Therefore, depending on the method for coating the active material with the carbon material, a carbon material other than the above may be used. For example, when coating by the sintering method described in detail below, a water-soluble polymer such as polyvinyl alcohol and sucrose is preferably used as a carbon source for coating the active material. Among these, polyvinyl alcohol is preferable.

  The shape of the conductive auxiliary agent particles 12 (the shape in a state of being coated with the active material) is not particularly limited, and may be in the form of particles or fibers. From the viewpoint of easy coating, a particle form is preferable, and from a conductive point, a fiber form is preferable.

  The size of the conductive auxiliary agent particles 12 is not particularly limited, but from the viewpoint of sufficiently causing a mechanochemical reaction, the average particle size of the conductive auxiliary agent particles 12 is 1/10 of the average particle size of the positive electrode active material particles 11. The following is preferable. For example, when the carbon material is in the form of particles, the average particle size (secondary particle size) is preferably 10 to 200 nm, more preferably 20 to 150 nm. When the carbon material is in a fiber form, the diameter is preferably 20 to 500 nm, more preferably 50 to 300 nm, and the length is preferably 5 to 20 μm, more preferably 8 to 15 μm. It is. With such a size, the surface of the positive electrode active material particle 11 is easily and uniformly coated with the carbon material.

<Mixing device>
FIG. 2 is a schematic cross-sectional view showing an example of a mixing device 100 used for manufacturing the composite particles 10 for positive electrode.

  The mixing apparatus 100 includes a container (corresponding to an accommodating part) 110 and a wing part (corresponding to a rotating body) 120 that rotates relative to the container 110 in the container 110. The mixing apparatus 100 performs a mixing process in which the powder of the positive electrode active material particles 11 and the powder of the conductive auxiliary agent particles 12 are flowed by the blades 120 in the container 110 and mixed in a dry manner. Thereby, the mixing apparatus 100 manufactures the composite particles 10 for the positive electrode in which the positive electrode active material particles 11 and the conductive additive particles 12 are combined.

  The configuration of the mixing apparatus 100 is not limited to the mixing apparatus 100 shown in FIG. 2 as long as it can perform the mixing process of the powder of the positive electrode active material particles 11 and the powder of the conductive auxiliary agent particles 12, and is publicly known. The mixing device (mixer) can be used.

<Method for determining production conditions of composite particles for positive electrode>
A method for determining the manufacturing conditions of the composite particles 10 for the positive electrode will be described. FIG. 3 is a flowchart showing a method for determining manufacturing conditions for the composite particles 10 for positive electrode.

  First, the operator sets the peripheral speed of the blade portion 120 of the mixing device 100 and the processing time of the mixing process (step 1 (hereinafter referred to as “S1”; the same applies to other S numbers)). .

  Next, an operator performs the manufacturing process which manufactures the composite particle 10 for positive electrodes using the mixing apparatus 100 (S2). More specifically, the powder of the positive electrode active material particles 11 and the powder of the conductive auxiliary agent particles 12 are put into the container 110 of the mixing apparatus 100. And the mixing apparatus 100 operates the wing | blade part 120 with the circumferential speed and processing time which were set by S1. Thereby, the mixing process which makes the powder of the positive electrode active material particle 11 and the powder of the conductive support agent particle 12 flow and mix is performed.

  The mixing apparatus 100 applies mechanical energy such as compression force, shear force, friction force, and the like to the powder of the positive electrode active material particles 11 and the powder of the conductive additive particles 12 by the mixing process. The mechanical energy activates the surfaces of the positive electrode active material particles 11 and the conductive auxiliary agent particles 12 to cause a so-called mechanochemical reaction. Thereby, the mixing apparatus 100 manufactures the composite particles 10 for the positive electrode in which the positive electrode active material particles 11 and the conductive auxiliary agent particles 12 are bonded (coated) by a mechanochemical reaction. In the present specification, the “circumferential speed” is a speed at the outermost peripheral position (maximum radius position) of the wing part 120 that is a rotating body, the rotation number per unit time is n, the maximum radius is R, Then, the peripheral speed of the wing part 120 = 2πnR.

  Next, an operator performs the electrical conductivity measurement process which measures the electrical conductivity of the composite particle 10 for positive electrodes based on JISK1469 (2003) (S3). More specifically, the operator first fills a cylindrical container having a negative electrode with a predetermined amount (for example, 1 g) of a sample that is a dry powder of the positive electrode composite particles 10. Next, the positive electrode is inserted into a container filled with the sample. Thereafter, the sample is compressed by applying pressure with a jig. In this state, the conductivity of the sample is measured by the two-terminal method. Furthermore, the pressure applied to the sample is increased, and the conductivity of the sample when a predetermined pressure is applied is measured. Thereby, the relationship between the pressure applied to the composite particles 10 for positive electrodes and the electrical conductivity of the composite particles 10 for positive electrodes can be obtained.

  Here, the relationship between the peripheral speed and processing time when producing the positive electrode composite particles 10 and the conductivity will be described.

  FIG. 4 shows the pressure applied to the positive electrode composite particles 10 and the conductivity of the positive electrode composite particles 10 obtained when the conductivity is measured using the positive electrode composite particles 10 manufactured under different conditions of the peripheral speed of the wing 120. It is a conceptual diagram which shows the relationship with a rate.

  By changing the peripheral speed of the wing part 120, a plurality of samples in which the positive electrode composite particles 10 are manufactured are prepared. In the example shown in FIG. 4, when the mixing process is performed at “circumferential speed 1”, when the mixing process is performed at “peripheral speed 2” slower than the peripheral speed 1, and at the low speed without using the mixing device 100, the mixing process is performed. The case of “no processing” is shown. Here, “mixing at low speed” means stirring and mixing at a low speed that does not cause a mechanochemical reaction. The mixing speed when mixing at a low speed can be, for example, 10 rpm or less. Further, in FIG. 4, a reference conductivity curve is shown as a conductivity reference value. The conductivity reference value will be described in detail later.

  As shown in FIG. 4, the conductivity of each sample increases as the pressure during measurement increases. This is because by applying a high pressure to the composite particles 10 for the positive electrode, the density of the particles is increased, and the particles are close to each other and are easily conductive. Further, where the conductivity has increased to some extent, the conductivity is saturated without increasing even if the pressure is increased further. This is because the density at the time of measurement no longer increases, or even if the density increases, the conductivity is not affected.

  Thus, the conductivity increases as the measurement pressure increases. For this reason, it is necessary to provide a different conductivity reference value for each pressure as well when determining the peripheral speed. Therefore, as shown in FIG. 4, the conductivity reference value is a curve that increases as the pressure increases.

  As for the peripheral speed of the wing portion 120, the peripheral speed 1 has a higher conductivity than the peripheral speed 2 which is slower than this. This is because the higher the peripheral speed, the more effectively the mechanochemical reaction can be generated, and the positive electrode composite particle 10 itself has a higher electrical conductivity.

  FIG. 5 shows the pressure applied to the composite particle for positive electrode 10 and the electrical conductivity of the composite particle for positive electrode 10 obtained when the electrical conductivity is measured using the composite particle for positive electrode 10 manufactured under different conditions for the mixing treatment time. It is a conceptual diagram which shows the relationship.

  A plurality of samples in which the composite particles for positive electrode 10 are manufactured are manufactured by changing the processing time of the mixing process. In the example shown in FIG. 5, when the mixing process is performed at “processing time 1”, the mixing process is performed at “processing time 2” shorter than the processing time 1, and the mixing process is performed without using the mixing apparatus 100. The case of “no processing” is shown. Further, in FIG. 5, similarly to FIG. 4, a reference conductivity curve is shown as the conductivity reference value.

  As shown in FIG. 5, when the pressure at the time of measurement is increased, the conductivity increases as in FIG. As described above, the reference conductivity becomes a curve that increases with pressure.

  On the other hand, the conductivity is higher in the processing time 1 than in the processing time 2 shorter than this. This is because by increasing the treatment time, a mechanochemical reaction can be effectively generated, and the conductivity of the positive electrode composite particle 10 itself is increased.

  Next, the operator determines whether or not the conductivity is equal to or higher than a predetermined conductivity reference value based on the results shown in FIGS. 4 and 5 obtained by the conductivity measurement step (S3). (S4: 1st judgment process). Thus, the operator can determine whether or not the peripheral speed of the wing 120 and the processing time of the mixing process set in S1 are valid set values.

  Here, the “conductivity reference value” is a predetermined value based on, for example, the conductivity of the powder of the composite particles 10 for positive electrode not subjected to the mixing process by the mixing apparatus 100 (“no treatment” shown in FIGS. 4 and 5). The value can be increased by a percentage X%. The ratio X% can be appropriately set according to the required performance required for the battery. For example, the ratio X% can be set to about 1 to 50%, more preferably about 30 to 50%.

  In the case shown in FIG. 4, the peripheral speed 1 is an effective set value because the conductivity at the peripheral speed 1 is equal to or higher than the conductivity reference value. On the other hand, since the conductivity of the peripheral speed 2 is less than the conductivity reference value, the peripheral speed 2 is not an effective set value. Similarly, in the case shown in FIG. 5, the processing time 1 is an effective set value because the conductivity of the processing time 1 is equal to or higher than the conductivity reference value. On the other hand, since the conductivity of the processing time 2 is less than the conductivity reference value, the processing time 2 is not an effective set value.

  Since the mechanochemical reaction does not occur in the positive electrode composite particles 10 that are not subjected to the mixing treatment by the mixing apparatus 100, the bonding force between the positive electrode active material particles 11 and the conductive auxiliary agent particles 12 is weak. Further, even when the peripheral speed of the wing portion 120 is low or the processing time of the mixing process is short, the mechanical energy acting on the powder is small, so that a sufficient mechanochemical reaction cannot be obtained, and the positive electrode active material particles 11 The bonding strength between the conductive auxiliary particles 12 is weak. When the binding force between the positive electrode active material particles 11 and the conductive auxiliary agent particles 12 is weak, the conductivity of the positive electrode composite particles 10 becomes low. Therefore, the operator can measure the peripheral speed of the wing part 120 and the mixing treatment that can sufficiently obtain the bonding force between the positive electrode active material particles 11 and the conductive auxiliary agent particles 12 by measuring the conductivity of the positive electrode composite particles 10. Processing time can be determined.

  In FIGS. 4 and 5, the conductivity reference value is also shown as a curve that changes as the pressure changes. However, in the actual manufacturing process, the pressure for measuring the conductivity may be set to a constant value, and only one point of the conductivity reference value at that constant pressure may be determined, or the conductivity reference for each of a plurality of pressures. You may decide the value.

  When the electrical conductivity obtained by the electrical conductivity measurement step (S3) is less than a predetermined electrical conductivity reference value (S4: NO), the operator performs the peripheral speed of the wing 120 and the mixing process set in the manufacturing process. It is determined that the processing time is not a valid set value (S11). More specifically, it is determined that the peripheral speed of the wing part 120 is slow or the processing time of the mixing process is short. In response to this result, the setting values of the peripheral speed and processing time are changed and reset (S12), and the process returns to S2 to perform the manufacturing process. By repeating this thereafter, the effective peripheral speed and processing time can be narrowed down.

  Specifically, in S12, the peripheral speed of the wing 120 is set faster than the current setting, or the processing time of the mixing process is set longer than the current setting. At this time, how much the peripheral speed and the processing time are increased and reset is arbitrary, but can be determined from the relationship between the conductivity measured in S3 and the conductivity reference value, for example. If the conductivity measured in S3 is close to the conductivity reference value, the increase rate of the peripheral speed and processing time is reduced, and if the conductivity is far from the conductivity reference value, the increase rate is increased.

  On the other hand, when the electrical conductivity obtained by the electrical conductivity measurement step (S3) is equal to or higher than a predetermined electrical conductivity reference value (S4: YES), the operator measures the pH of the composite particle for positive electrode 10 by a pH measurement step. (S5). More specifically, a predetermined amount of the composite particles for positive electrode 10 is put into a predetermined amount of water, and stirred to prepare a solution in which the composite particles for positive electrode 10 are dispersed in water. The water used in the pH measurement step is not particularly limited as long as the pH is about 6 to 8, preferably pH 7, and there is no extreme metal contamination to the extent that pH measurement can be performed. For example, commercially available purified water or pure water (ion exchange water or distilled water) can be used. A known pH meter can be used for measuring the pH.

  FIG. 6 is a conceptual diagram showing the relationship between the time elapsed since the positive electrode composite particles 10 were put into water having a pH of 7 and the pH value.

  By measuring the pH of the solution for each time that has elapsed since the time when the powder of the composite particle for positive electrode 10 was introduced into water having a pH of 7, a relationship between the elapsed time and the pH value as shown in FIG. 6 can be obtained. . In the example shown in FIG. 6, the mixing process is performed at “peripheral speed 3” which is faster than the peripheral speed 1 of the wing part 120 in the case of FIG. The case of "no processing" processed is shown.

  Next, the operator determines whether or not the difference between the pH value of the positive electrode composite particles 10 obtained by the pH measurement step and the pH reference value is equal to or less than a predetermined deviation amount (S6: second determination step). ). Thus, the operator determines whether or not the peripheral speed of the wing 120 is an effective set value. At this stage, the effective peripheral speed is determined as a result of the determination based on the conductivity reference value in S4.

  Here, the “pH reference value” is obtained by, for example, dispersing a powder obtained by mixing the powder of the positive electrode active material particles 11 and the powder of the conductive auxiliary agent particles 12 in water without performing the mixing process by the mixing apparatus 100. It can be the pH value of the solution (“no treatment” shown in FIG. 6). Further, the “predetermined deviation amount” of the pH can be set to, for example, about 0.5 to 6, more preferably about 1 to 5.

  As shown in FIG. 6, with the pH reference value, there is almost no change in the pH value over time. On the other hand, at the peripheral speed 3, the pH value increases with time. As a result, the difference between the pH value at the peripheral speed 3 and the pH reference value exceeds a predetermined deviation amount (“deviation amount” shown in FIG. 6). This is because the surface layer 11b of the positive electrode active material particles 11 is destroyed because the peripheral speed is excessively increased during the mixing process, and the metal component forming the core portion 11a is gradually dissolved in water. This is because. Therefore, the peripheral speed 3 is not an effective set value.

  In the present embodiment, since the positive electrode active material particles 11 contain lithium ions, when the surface layer 11b of the positive electrode active material particles 11 is damaged, Li of the positive electrode active material particles 11 dispersed in water is gradually eluted. And reacts with water to produce lithium hydroxide (LiOH). Lithium hydroxide dissolves in water and exhibits alkalinity. For this reason, when the surface layer 11b of the positive electrode active material particles 11 is damaged, the pH value of the solution rises with time. Therefore, the operator can determine whether or not the surface layer 11b of the positive electrode active material particles 11 is damaged by measuring the pH. As a result, the operator can determine the peripheral speed of the wing part 120 at which the surface layer 11b of the positive electrode active material particles 11 is not damaged. In addition, when the surface layer 11b of the positive electrode active material particle 11 is damaged, it is not limited to the case where the pH value increases with the passage of time as in the present embodiment, but depending on the metal component forming the core portion 11a. The present invention can be applied even when the pH value decreases with the passage of time.

  In addition, it is preferable to perform the measurement of pH after a certain amount of time has passed, not immediately after the produced composite particles 10 for positive electrode are put into water. This is because, as described above, in the manufactured composite particle for positive electrode 10, it may take some time for the metal component to dissolve when the surface layer 11 b is damaged. For example, it may be about 1 to 60 minutes, preferably 5 to 30 minutes. Moreover, you may make it measure several times for every predetermined time with progress of time. In the case where there is no standard mixing treatment, the metal component hardly dissolves even after a lapse of time, so there is no need to wait. However, in order to match the measurement conditions, the measurement may be performed after the same time has elapsed in accordance with the pH measurement of the positive electrode composite particles 10.

  When the difference between the pH value of the positive electrode composite particle 10 and the pH reference value exceeds a predetermined amount of deviation (S6: NO), the operator can effectively use the peripheral speed of the wing 120 set in the manufacturing process. It is determined that the set value is not correct (S11). Thereafter, in S12, the setting value of the peripheral speed of the wing 120 is changed and reset. At this point, the peripheral speed is set to be slower than the current set value.

  On the other hand, when the difference between the pH value of the composite particle for positive electrode 10 and the pH reference value is equal to or less than a predetermined deviation (S6: YES), the operator uses the composite particle for positive electrode 10 to produce a test cell. (S7). The test cell can be, for example, a small test cell.

More specifically, first, the worker produces a positive electrode including the positive electrode composite particles 10 and a negative electrode. The produced positive electrode and negative electrode are punched out using a punch. Furthermore, a separator (for example, a polypropylene microporous film) is prepared. In addition, an electrolytic solution (for example, LiPF ₆ that is a lithium salt dissolved in an equal volume mixed solution of ethylene carbonate and propylene carbonate at a concentration of 1M) is prepared.

  The negative electrode, separator, and positive electrode obtained above are laminated in this order to produce a battery element, and an electrolyte is injected into the separator. Then, a current extraction terminal is connected to each of the negative electrode and the positive electrode, and the battery element is placed in an aluminum laminate film so that the current extraction terminal is exposed to the outside, and sealed in a vacuum to produce a test cell. To do.

  Next, the operator performs an internal resistance measurement step of measuring the internal resistance of the test cell in the discharged state after the first charge / discharge (S8). Here, a direct current resistance (DCR) is measured as the internal resistance of the test cell.

  The measurement of DCR is used to determine whether or not the positive electrode active material is manufactured using the manufactured positive electrode composite particles 10 and is within the range of a standard direct current resistance (DCR reference value). For this reason, only the DCR after the first charge / discharge may be measured. Of course, the DCR after a plurality of charge / discharge cycles may be measured, whereby the quality of the composite particle for positive electrode 10 in a state close to actual use can be determined.

  For the measurement of DCR, for example, constant current and constant voltage charging is performed until SOC (State Of Charge) reaches 100%, and then constant current discharging is performed for a certain time (or until reaching a certain voltage). A DCR value is obtained by dividing the voltage difference (voltage value of the difference) from the open circuit voltage at 100% SOC in the constant current discharge process to the voltage at the end of discharge by the current value of constant current discharge. The DCR may be measured by other methods or by a chemical impedance analyzer having a DCR measurement function.

  Next, the operator determines whether or not the measured DCR value is equal to or less than the DCR reference value (corresponding to the resistance reference value) based on the result obtained in the internal resistance measurement step (S9: third determination step). .

  Here, the “DCR reference value” is, for example, the same as in the test cell described above, using a slurry prepared by mixing in a solvent containing the powder of the positive electrode active material particles 11 and the powder of the conductive additive particles 12 together with the binder. And the DCR value is measured. Therefore, when obtaining the DCR reference value, a test cell that does not perform the powder dry mixing process as in this embodiment is used.

  The internal resistance of the secondary battery can be decomposed into three types of resistance components: a reaction resistance component, an ohmic resistance component, and a diffusion resistance component. The reaction resistance component is a resistance component derived from a chemical reaction of the active material. The ohmic resistance component is a resistance component composed of contact resistance between constituent materials (metal members) and conductive resistance in the constituent materials. The diffusion resistance component is a resistance component that represents ion diffusion in the active material or in the solution. If the treatment time of the mixing treatment is excessively long, the conductive auxiliary agent particles 12 covered with the positive electrode active material particles 11 are excessively densified. Thereby, the conductive auxiliary agent particles 12 limit the battery reaction of the positive electrode active material particles 11, particularly the movement of lithium ions on the positive electrode side, and charge and recharge of the battery accompanying the reversible occlusion and release of the lithium ions. Discharges the discharge reaction. As a result, the reaction resistance of the test cell is increased, and the internal resistance value is increased. Therefore, the operator can determine whether the processing time of the mixing process is not excessively long by measuring the internal resistance value (DCR in this case).

  When the DCR value of the test cell obtained by the internal resistance measurement process is higher than the DCR reference value (S9: NO), the operator can use the processing time of the mixing process made effective in S4 as the battery reaction. It is determined that the set value is not correct (S11). More specifically, it is determined that the processing time of the mixing process is excessively long. Thereafter, the setting value of the processing time is changed and reset by S12. At this stage, the processing time of the mixing process is set to be shorter than the current set value.

  On the other hand, when the DCR value of the test cell obtained by the internal resistance measurement step is equal to or less than the DCR reference value (S9: YES), the operator sets the effective speed of the wing 120 and the processing time of the mixing process. (S10). The peripheral speed and processing time set at this time are finally determined as effective set values.

  Thus, if the effective setting value of a peripheral speed and processing time is determined, the composite particle 10 for positive electrodes will be manufactured using the setting value. In the manufacturing method of the composite particles 10 for the positive electrode, the powder of the positive electrode active material particles 11 and the powder of the conductive auxiliary agent particles 12 are introduced into the container 110 of the mixing apparatus 100 described above, and the determined peripheral speed and processing time are determined. By mixing them dry.

  As described above, the described embodiment has the following effects.

  In the method for determining the manufacturing condition of the composite particle for positive electrode 10 according to the present embodiment, the core part 11a is provided in the container 110 of the mixing apparatus 100 provided with the wing part (rotating body) 120 in the container (accommodating part) 110. The positive electrode active material particle 11 powder coated with the surface layer 11b made of a material different from the core part 11a and the conductive auxiliary agent particle 12 powder are put on the surface of the wing part 120, and the wing part 120 is rotated and mixed in a dry manner. This is a method for determining manufacturing conditions for manufacturing the composite particles 10 for the positive electrode in which the positive electrode active material particles 11 and the conductive additive particles 12 are bonded by performing the mixing process. The manufacturing conditions are determined by setting the peripheral speed of the wing 120 and the processing time of the mixing process (S1), the manufacturing process (S2) for manufacturing the composite particles for positive electrode 10, and the conductivity of the composite particles for positive electrode 10 Obtained by a conductivity measuring step (S3) for measuring the rate, a pH measuring step (S5) for measuring the pH of a solution in which the composite particles for positive electrode 10 are dispersed in water, a conductivity measuring step and a pH measuring step. And a determination step (S4, S6) for determining whether the peripheral speed of the wing portion 120 set in the manufacturing process and the processing time of the mixing process are effective set values based on the result.

  According to the method for determining the manufacturing condition of the composite particle for positive electrode 10 described above, in the manufacture of the composite particle for positive electrode 10 in which the powder of the positive electrode active material particle 11 and the powder of the conductive additive particle 12 are dry-mixed, the wing part 120 is used. The permissible values of the peripheral speed and the processing time of the mixing process can be determined. In particular, in the positive electrode active material particles 11 having the core portion 11a and the surface layer 11b, an appropriate peripheral speed capable of suppressing damage to the surface layer 11b can be obtained. Thereby, the binding force between the positive electrode active material particles 11 and the conductive additive particles 12 is increased while suppressing damage to the surface layer 11b of the positive electrode active material particles 11 without depending on the configuration or material design of the mixing device 100. Manufacturing conditions that can reduce the internal resistance of the battery can be determined.

  In addition, in the determination process, when the conductivity obtained by the conductivity measurement process is equal to or higher than a predetermined conductivity reference value, the peripheral speed of the wing 120 and the processing time of the mixing process set in the manufacturing process are effective. 1st judgment process (S4: YES) which judges that it is an easy setting value. Thereby, the bond strength between the positive electrode active material particles 11 and the conductive auxiliary agent particles 12 can be increased, and the internal resistance of the battery can be reduced.

  Further, the determination step was obtained by the pH measurement step using the pH value of the solution in which the powder of the positive electrode active material particles 11 and the powder of the conductive auxiliary agent particles 12 before the mixing treatment were dispersed in water as the pH reference value. A second determination step (S6: determining that the peripheral speed of the wing part 120 set in the manufacturing process is an effective set value when the difference between the pH value and the pH reference value is equal to or less than a predetermined deviation amount. YES). Thereby, in manufacture of the composite particle 10 for positive electrodes, it can suppress that the surface layer 11b of the positive electrode active material particle 11 is damaged.

  In addition, the method for determining the manufacturing condition of the composite particle for positive electrode 10 according to the present embodiment further includes an internal resistance measurement step (S8) for measuring the internal resistance value of a cell including the composite particle for positive electrode 10 in the positive electrode. In the determination step, it is further determined whether the processing time of the mixing process is an effective set value based on the result obtained in the internal resistance measurement step (S9). Thereby, it can be judged whether the processing time of a mixing process is not too long, and it can prevent that the conductive support agent particle 12 inhibits the battery reaction of the positive electrode active material particle 11. Thereby, the internal resistance of the battery can be further reduced.

  Further, the determining step determines that the processing time of the mixing process set in the manufacturing process is an effective set value when the internal resistance value obtained in the internal resistance measuring process is equal to or less than a predetermined resistance reference value. It has a 3rd judgment process (S9: YES). Thereby, it is possible to prevent the conductive auxiliary agent particles 12 from inhibiting the battery reaction of the positive electrode active material particles 11 by preventing the processing time of the mixing treatment from becoming excessively long. Thereby, the internal resistance of the battery can be further reduced.

  Moreover, the manufacturing method of the composite particle 10 for positive electrodes which concerns on this embodiment is a material different from the core part 11a on the surface of the core part 11a in the said container 110 of the mixing apparatus 100 with which the wing | blade part 120 was equipped in the container 110. The powder of the positive electrode active material particles 11 coated with the surface layer 11b and the powder of the conductive auxiliary agent particles 12 are charged, and a mixing process is performed in which the wing 120 is rotated and mixed in a dry manner to perform positive electrode active This is a method for producing a composite particle for positive electrode 10 that produces composite particles for positive electrode 10 in which substance particles 11 and conductive additive particles 12 are bonded. In the method for producing the composite particle for positive electrode 10, the set values made effective by the method for determining the production condition of the composite particle for positive electrode 10 are used as the peripheral speed of the wing 120 and the processing time of the mixing process. Thereby, the binding force between the positive electrode active material particles 11 and the conductive additive particles 12 is increased while suppressing damage to the surface layer 11b of the positive electrode active material particles 11 without depending on the configuration or material design of the mixing device 100. The internal resistance of the battery can be reduced.

  As mentioned above, although the determination method of the manufacturing conditions of the composite particles for positive electrodes and the manufacturing method of the composite particles for positive electrodes according to the present invention have been described through the embodiments, the present invention is not limited only to the contents described in the embodiments, Modifications can be made as appropriate based on the description of the scope of claims.

  For example, the mixing device is not limited to the configuration described in the embodiment as long as the powder can be flowed, and a known mixer or the like can be used. In addition, the storage unit of the mixing device is not limited to the container described in the embodiment as long as it has a space for storing powder to flow, and is configured by a space formed between two or more members, for example. May be. Furthermore, the rotating body of the mixing device is not limited to the wing part described in the embodiment as long as mechanical energy for flowing the powder can be applied, and may be a rotating disk, for example.

  Moreover, the material, particle size, etc. which comprise positive electrode active material particle | grains and conductive support agent particle | grains are not specifically limited to the structure demonstrated in embodiment.

  In the embodiment, the method for determining the manufacturing condition of the composite particles for positive electrode has been described as including the internal resistance measurement step of the test cell and the third determination step of determining the result thereof, but is not limited thereto, and the internal resistance measurement is performed. The process and the third determination process may not be included.

  In the embodiment, the first determination step is performed after the conductivity measurement step, and then the second determination step is performed subsequent to the pH measurement step. However, these steps may be performed in the reverse order. That is, the second determination step may be performed first after the pH measurement step, and then the first determination step may be performed subsequent to the conductivity measurement step. In addition, the first determination step and the second determination step may be performed together after performing the pH measurement step following or concurrently with the conductivity measurement step. By performing the first determination step and the second determination step together, the peripheral speed can be increased or the processing time can be lengthened if the conductivity is low, and the peripheral speed can be decreased if the difference in pH value is large. You can change settings at once. Further, the measurement of internal resistance and the subsequent third determination step may be performed in any order as long as they are after the manufacturing process of the composite particles for positive electrode, and the first to third determination steps are performed as one determination step. Also good.

10 Composite particles for positive electrode,
11 positive electrode active material particles,
11a Core part of positive electrode active material particles,
11b The surface layer of the positive electrode active material particles,
12 conductive aid particles,
100 mixing device,
110 container (container),
120 Wings (rotating body).

Claims (6)

The powder of the positive electrode active material particles in which the surface of the core part is coated with a surface layer made of a material different from the core part, and the powder of the conductive auxiliary agent particles in the container part of the mixing device provided with the rotating body in the container part. A manufacturing condition for manufacturing a composite particle for a positive electrode in which a positive electrode active material particle and a conductive auxiliary agent particle are combined by performing a mixing process in which a rotating body is rotated and the rotary body is rotated and mixed in a dry manner. A method for determining
A manufacturing process for manufacturing the positive electrode composite particles by setting a peripheral speed of the rotating body and a processing time of the mixing process;
A conductivity measuring step for measuring the conductivity of the composite particles for positive electrode;
A pH measurement step for measuring the pH of a solution in which the composite particles for positive electrode are dispersed in water;
Judgment whether or not the peripheral speed set in the manufacturing process and the processing time of the mixing process are effective set values based on the results obtained by the conductivity measuring process and the pH measuring process And a method for determining manufacturing conditions for the composite particles for positive electrode. The determination step includes
When the electrical conductivity obtained by the electrical conductivity measurement step is greater than or equal to a predetermined electrical conductivity reference value, the peripheral speed of the rotating body and the processing time of the mixing process set in the manufacturing process are effective set values. The method for determining production conditions for composite particles for a positive electrode according to claim 1, further comprising a first determination step for determining that there is one. The determination step includes
The pH value obtained by the pH measurement step and the pH value of a solution in which the powder of the positive electrode active material particles and the powder of the conductive auxiliary agent particles before the mixing treatment are dispersed in water are set as the pH reference value, and 2. A second determination step of determining that the peripheral speed of the rotating body set in the manufacturing step is an effective set value when a difference from a pH reference value is equal to or less than a predetermined deviation amount. Or the determination method of the manufacturing conditions of the composite particle for positive electrodes of Claim 2. An internal resistance measurement step of measuring an internal resistance value of a cell containing the composite particles for positive electrode in the positive electrode;
The said determination process WHEREIN: Based on the result obtained by the said internal resistance measurement process, it is further determined whether the processing time of the said mixing process is an effective setting value. Of determining manufacturing conditions for composite particles for positive electrode. The determination step includes
Third determination for determining that the processing time of the mixing process set in the manufacturing process is an effective setting value when the internal resistance value obtained by the internal resistance measurement process is equal to or less than a predetermined resistance reference value. The method of determining the manufacturing conditions of the composite particle for positive electrodes of Claim 4 which has a process. The powder of the positive electrode active material particles in which the surface of the core part is coated with a surface layer made of a material different from the core part, and the powder of the conductive auxiliary agent particles in the container part of the mixing device provided with the rotating body in the container part. The positive electrode composite particles for producing positive electrode composite particles in which the positive electrode active material particles and the conductive auxiliary particles are combined by performing a mixing process of rotating the rotating body and mixing in a dry manner. A manufacturing method of
The setting value validated by the method for determining the production condition of the composite particle for positive electrode according to any one of claims 1 to 5 is used as a peripheral speed of the rotating body and a processing time of the mixing treatment. A method for producing composite particles.