Nonaqueous secondary battery and method of manufacturing nonaqueous secondary battery

Abstract

To provide a nonaqueous secondary battery and a method of manufacturing a nonaqueous secondary battery, capable of suppressing increase in resistance while suppressing increase in viscosity of a cathode mixture.SOLUTION: A nonaqueous secondary battery includes a cathode sheet, an anode sheet, and a nonaqueous electrolytic solution. A cathode mixture forming the cathode sheet contains a cathode active material 31 and a cathode binder. The porosity of the cathode active material 31 is 25% or more and 50% or less. The particle diameter of a secondary particle 31B that is an aggregate of primary particles 31A of the cathode active material 31 is 2 μm or more and 7 μm or less. The BET specific surface area of the cathode active material 31 is 1.2 m2 / g or more and 3.0 m2 / g or less. An acid for producing a salt 33 by neutralizing LiOH32 contained in the cathode active material 31 is contained X or more and Y or less equivalents of LiOH32. X and Y are obtained from the following equations. X=0.0013×the particle diameter×(the BET specific surface area)2 / the porosity, Y=0.0021×the particle diameter×(the BET specific surface area)2 / the porosity.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a non-aqueous secondary battery and a method for manufacturing the same.

Background Art

[0002] A non-aqueous secondary battery includes an electrode body in which a positive electrode sheet and a negative electrode sheet are laminated via a separator, and an electrolytic solution. The positive electrode sheet has a positive electrode composite material containing a positive electrode active material coated on a positive electrode substrate. A transition metal oxide is used as the positive electrode active material of the non-aqueous secondary battery described in Patent Document 1.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] By the way, the transition metal oxide used as the positive electrode active material of the non-aqueous secondary battery may contain LiOH as an impurity. When LiOH is contained in the positive electrode active material, it reacts with a binder such as PVdF to generate HF, thereby increasing the viscosity of the composite paste in the kneading step of the positive electrode composite material. Therefore, when an organic acid or an inorganic oxide is used to neutralize LiOH, the reaction product of the organic acid or the inorganic oxide and LiOH covers the positive electrode active material, inhibiting the reaction surface and increasing the resistance.

Means for Solving the Problems

[0005] The non-aqueous secondary battery for solving the above problems is a non-aqueous secondary battery having a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte. The positive electrode composite material constituting the positive electrode sheet includes a positive electrode active material and a positive electrode binder. The porosity of the positive electrode active material is 25% or more and 50% or less. The particle size of the secondary particles, which are aggregates of the primary particles of the positive electrode active material, is 2 μm or more and 7 μm or less. The BET specific surface area of the positive electrode active material is 1.2 m 2 / g or more and 3.0 m 2 / g or less. An acid for the purpose of neutralizing LiOH contained in the positive electrode active material is contained in an amount equal to X or more and Y or less of the LiOH. The X and the Y are obtained from the following formulae. X = 0.0013 × the particle size × (the BET specific surface area) 2 / the porosity Y = 0.0021 × the particle size × (the BET specific surface area) 2 / the porosity

[0006] According to the above configuration, the amount of the acid for neutralizing LiOH is adjusted according to the physical properties of the positive electrode active material, and only the LiOH on the surface of the secondary particles of the positive electrode active material that affects the increase in viscosity by reacting with the positive electrode binder is neutralized. Therefore, it is possible to suppress an increase in the resistance while suppressing an increase in the viscosity of the positive electrode composite material.

[0007] The method for manufacturing a non-aqueous secondary battery for solving the above problems is a method for manufacturing a non-aqueous secondary battery having a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte. The method includes a coating step of manufacturing the positive electrode sheet by coating a positive electrode composite material layer including a positive electrode active material and a positive electrode binder on a positive electrode substrate, and a rolling step of rolling the positive electrode sheet coated with the positive electrode composite material layer. The porosity of the positive electrode active material is 25% or more and 50% or less. The particle size of the secondary particles, which are aggregates of the primary particles of the positive electrode active material, is 2 μm or more and 7 μm or less. The BET specific surface area of the positive electrode active material is 1.2 m 2 / g or more and 3.0 m 2 / g or less. An acid for the purpose of neutralizing LiOH contained in the positive electrode active material is contained in an amount equal to X or more and Y or less of the LiOH. The X and the Y are obtained from the following formulae. X = 0.0013 × the particle size × (the BET specific surface area)2 / the void fraction Y = 0.0021 × the particle size × (the BET specific surface area) 2 / the void fraction

[0008] According to the above method, the amount of acid for neutralizing LiOH is adjusted according to the physical properties of the positive electrode active material, and only the LiOH on the surface of the secondary particles of the positive electrode active material that affects the increase in viscosity by reacting with the positive electrode binder is neutralized. Therefore, while suppressing the increase in the viscosity of the positive electrode mixture, an increase in resistance can be suppressed.

[0009] Regarding the method for manufacturing the non-aqueous secondary battery, it is preferable that the crushing rate in the rolling step is 20% or more and 40% or less. According to the above method, the crushing rate in the rolling step is set to 20% or more and 40% or less. For this reason, by causing the positive electrode active material to crack and a fresh surface not covered with the reaction product of LiOH to appear, an increase in resistance can be further suppressed.

Advantages of the Invention

[0010] According to the present invention, while suppressing the increase in the viscosity of the positive electrode mixture, an increase in resistance can be suppressed.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Modes for Carrying Out the Invention

[0012] [This Embodiment] Hereinafter, with reference to FIGS. 1 to 4, an embodiment of a non-aqueous secondary battery and a method for manufacturing the non-aqueous secondary battery will be described. As an example of the non-aqueous secondary battery, a lithium-ion secondary battery will be described.

[0013] [Lithium-ion secondary battery 10] As shown in FIG. 1, the lithium-ion secondary battery 10 is a cell battery that is enclosed in a resin or metal case in a state combined with a plurality of lithium-ion secondary batteries 10 to form a battery pack. The battery pack is used in hybrid vehicles and electric vehicles.

[0014] The lithium-ion secondary battery 10 includes a battery case 11 and a lid 12. The battery case 11 has a rectangular parallelepiped shape with an opening on the upper side. The lid 12 seals the opening of the battery case 11. The battery case 11 and the lid 12 are made of a metal such as aluminum or an aluminum alloy. The lithium-ion secondary battery 10 forms a sealed battery chamber by attaching the lid 12 to the battery case 11.

[0015] Two positive electrode external terminals 13A and a negative electrode external terminal 13B are provided on the lid 12. The positive electrode external terminal 13A and the negative electrode external terminal 13B are used for charging and discharging electric power. An electrode body 20 is housed inside the battery case 11. An extrapolation film (not shown) is inserted between the battery case 11 and the electrode body 20. The positive electrode current collector portion 20A, which is the end portion on the positive electrode side of the electrode body 20, is electrically connected to the positive electrode external terminal 13A via the positive electrode current collector member 14A. The negative electrode current collector portion 20B, which is the end portion on the negative electrode side of the electrode body 20, is electrically connected to the negative electrode external terminal 13B via the negative electrode current collector member 14B. Further, a non-aqueous electrolyte is injected into the battery case 11 through a liquid injection hole (not shown). Note that the shapes of the positive electrode external terminal 13A and the negative electrode external terminal 13B are not limited to the shapes shown in FIG. 1 and may be any shape.

[0016] [Electrode body 20] As shown in FIG. 2, the electrode body 20 is a flat wound body obtained by winding a laminate in which a long positive electrode sheet 21 and a negative electrode sheet 24 are laminated with a separator 27 interposed therebetween. The positive electrode sheet 21, the negative electrode sheet 24, and the separator 27 are laminated such that the longitudinal direction of each coincides with the longitudinal direction D1. The laminate before winding is laminated in the order of the positive electrode sheet 21, the separator 27, the negative electrode sheet 24, and the separator 27.

[0017] [Positive electrode sheet 21] The positive electrode sheet 21 includes a positive electrode current collector 22 and a positive electrode composite layer 23. The positive electrode current collector 22 is a foil-shaped positive electrode base material formed in a long shape. The positive electrode composite layer 23 is provided on each of the two opposing surfaces of the positive electrode current collector 22. The positive electrode current collector 22 includes a positive electrode side uncoated portion 22A where the positive electrode current collector 22 is exposed without the positive electrode composite layer 23 being formed at one end in the width direction D2.

[0018] The positive electrode current collector 22 is made of a metal foil composed of aluminum or an alloy mainly composed of aluminum. The positive electrode current collector 22 functions as a current collector in the positive electrode. The positive electrode side uncoated portion 22A provided in the positive electrode current collector 22 forms a positive electrode side current collecting portion 20A by the opposing surfaces being pressed against each other in the state of the wound body.

[0019] The positive electrode composite layer 23 is a cured body of a liquid positive electrode composite paste. The positive electrode composite paste includes a positive electrode active material, a positive electrode solvent, a positive electrode conductive material, and a positive electrode binder. The positive electrode composite layer 23 is formed by drying the positive electrode composite paste and vaporizing the positive electrode solvent. Therefore, the positive electrode composite layer 23 includes a positive electrode active material, a positive electrode conductive material, and a positive electrode binder.

[0020] The positive electrode active material is a lithium-containing composite oxide capable of occluding and releasing lithium ions, which are charge carriers in the lithium-ion secondary battery 10. The lithium-containing composite oxide is an oxide containing lithium and other metal elements other than lithium. The other metal elements other than lithium are, for example, at least one selected from the group consisting of nickel, cobalt, manganese, vanadium, magnesium, molybdenum, niobium, titanium, tungsten, aluminum, and iron contained as iron phosphate in the lithium-containing composite oxide.

[0021] For example, the lithium-containing composite oxide is lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or lithium manganate (LiMn2O4). For example, the lithium-containing composite oxide is a ternary lithium-containing composite oxide containing nickel, cobalt, and manganese, namely lithium nickel cobalt manganese oxide (LiNiCoMnO2). For example, the lithium-containing composite oxide is lithium iron phosphate (LiFePO4).

[0022] As the positive electrode solvent, an NMP (N-methyl-2-pyrrolidone) solution, which is an example of an organic solvent, is used. As the positive electrode conductive material, for example, carbon black such as acetylene black and ketjen black, carbon fibers such as carbon nanotubes and carbon nanofibers, and graphite are used. The positive electrode binder is an example of the resin component contained in the positive electrode composite paste. As the positive electrode binder, for example, polyvinylidene fluoride (PVdF), polyvinyl alcohol (PVA), styrene-butadiene rubber (SBR), etc. are used.

[0023] Note that the positive electrode sheet 21 may be provided with an insulating layer at the boundary between the uncoated portion 22A on the positive electrode side and the positive electrode composite layer 23. The insulating layer includes an inorganic component having insulating properties and a resin component functioning as a binder. The inorganic component is at least one selected from the group consisting of powdery boehmite, titania, and alumina. The resin component is at least one selected from the group consisting of PVdF, PVA, and acrylic.

[0024] [Negative electrode sheet 24] The negative electrode sheet 24 includes a negative electrode current collector 25 and a negative electrode composite material layer 26. The negative electrode current collector 25 is a foil-shaped negative electrode base material formed in a long strip shape. The negative electrode composite material layer 26 is provided on each of two opposite surfaces of the negative electrode current collector 25. The negative electrode current collector 25 includes a negative electrode non-coated portion 25A where the negative electrode composite material layer 26 is not formed and the negative electrode current collector 25 is exposed at an end portion that is one end in the width direction D2 and is located opposite to the non-coated portion 22A on the positive electrode side.

[0025] The negative electrode current collector 25 is made of a metal foil composed of copper or an alloy mainly composed of copper. The negative electrode current collector 25 functions as a current collector in the negative electrode. In the state of the wound body, the facing surfaces of the negative electrode non-coated portion 25A are pressed against each other to form the negative electrode side current collecting portion 20B.

[0026] The negative electrode composite material layer 26 is a cured body of a liquid negative electrode composite material paste. The negative electrode composite material paste includes a negative electrode active material, a negative electrode solvent, a negative electrode thickening material, and a negative electrode binder. The negative electrode composite material layer 26 is formed by drying the negative electrode composite material paste and vaporizing the negative electrode solvent. Therefore, the negative electrode composite material layer 26 includes a negative electrode active material, and further, as additives, a negative electrode thickening material and a negative electrode binder. Note that the negative electrode composite material layer 26 may further include an additive such as a conductive material.

[0027] The negative electrode active material is a material capable of occluding and releasing lithium ions. As the negative electrode active material, for example, carbon materials such as graphite, non-graphitizable carbon, graphitizable carbon, and carbon nanotubes are used. As an example, the negative electrode solvent is water. As an example of the negative electrode thickening material, CMC (carboxymethyl cellulose) can be used as a thickening material containing a sodium salt. The same material as the positive electrode binder can be used for the negative electrode binder. As an example of the negative electrode binder, SAR (styrene acrylic acid copolymer) can be used as a binder containing a sodium salt.

[0028] [Separator 27] The separator 27 prevents contact between the positive electrode sheet 21 and the negative electrode sheet 24 and holds the non-aqueous electrolyte between the positive electrode sheet 21 and the negative electrode sheet 24. When the electrode body 20 is immersed in the non-aqueous electrolyte, the non-aqueous electrolyte penetrates from the end portion in the width direction D2 of the separator 27 toward the central portion.

[0029] The separator 27 is a non-woven fabric made of polypropylene or the like. As the separator 27, for example, a porous polymer film such as a porous polyethylene film, a porous polyolefin film, a porous polyvinyl chloride film, and an ion conductive polymer electrolyte film can be used.

[0030] [Non-aqueous electrolyte] The non-aqueous electrolyte is a composition in which a supporting salt is contained in a non-aqueous solvent. As the non-aqueous solvent, one or more materials selected from the group consisting of propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethyl methyl carbonate, etc. can be used. Further, as the supporting salt, one or more lithium compounds (lithium salts) selected from LiPF6, LiBF4, LiClO4, LiAsF6, LiCF3SO3, LiC4F9SO3, LiN(CF3SO2)2, LiC(CF3SO2)3, LiI, LiBOB (lithium bisoxalate borate), etc. can be used.

[0031] [Manufacturing method] Next, with reference to FIGS. 3 and 4, the manufacturing method of the lithium ion secondary battery 10 will be described. The manufacturing method of the positive electrode sheet 21 will be described.

[0032] The manufacturing method of the lithium ion secondary battery 10 includes a coating step of coating the positive electrode current collector 22 with the positive electrode mixture paste, a rolling step of rolling the positive electrode sheet 21 coated with the positive electrode mixture paste, and a drying step of drying the positive electrode mixture paste. The positive electrode mixture paste includes a positive electrode active material, a positive electrode solvent, a positive electrode conductive material, and a positive electrode binder. In the drying step, the positive electrode mixture paste is dried and the positive electrode solvent is vaporized to form the positive electrode mixture layer 23.

[0033] Figures 3 and 4 are model diagrams of the positive electrode active material 31. The positive electrode active material 31 is composed of secondary particles 31B which are aggregates of primary particles 31A. The porosity of the positive electrode active material 31 is 25[%] or more and 50[%] or less. The particle size of the secondary particles 31B of the positive electrode active material 31 is 2 [μm] or more and 7 [μm] or less. The particle size is measured by particle size distribution measurement. The BET specific surface area of the positive electrode active material 31 is 1.2 [m 2 / g] or more and 3.0 [m 2 / g] or less.

[0034] The positive electrode active material 31 contains LiOH 32. LiOH 32 adheres to the periphery of the primary particles 31A of the positive electrode active material 31. Figure 3 shows a state where the positive electrode composite material layer 23 does not contain an acid for the purpose of neutralizing LiOH 32 contained in the positive electrode active material 31.

[0035] Figure 4 shows a state where the positive electrode composite material layer 23 contains an acid for the purpose of neutralizing LiOH 32 contained in the positive electrode active material 31. The acid for the purpose of neutralizing LiOH 32 is contained in an amount equal to X or more and Y or less of LiOH 32. X and Y are obtained from the following formulas (1) and (2). X = 0.0013 × particle size × (BET specific surface area) 2 / porosity ··· (1) Y = 0.0021 × particle size × (BET specific surface area) 2 / porosity ··· (2)

[0036] The amount of the acid for the purpose of neutralizing LiOH 32 is adjusted according to the physical properties of the positive electrode active material 31. Therefore, only the LiOH 32 on the surface of the secondary particles 31B of the positive electrode active material 31 is neutralized to form a salt 33 by the acid for the purpose of neutralizing LiOH 32. Thus, the reaction between LiOH 32 on the surface of the secondary particles 31B of the positive electrode active material 31 and the positive electrode binder is suppressed, the increase in viscosity is suppressed, and the increase in resistance due to the reaction product between LiOH 32 and the positive electrode binder can be suppressed.

[0037] The compaction ratio in the rolling process is 20% or more and 40% or less. The compaction ratio is obtained from the following formula (3) based on the thickness of the positive electrode composite material before and after rolling. The adjustment of the compaction ratio is performed by adjusting the viscosity, solid content ratio, drying temperature, etc. of the positive electrode composite material paste. Compaction ratio = {1 - (thickness after rolling) / (thickness before rolling)} × 100 ··· (3)

[0038] By the above rolling, the secondary particles 31B of the positive electrode active material 31 can be cracked to expose a fresh surface that is not covered with the neutralized salt 33 which is a reaction product of LiOH 32 and an acid. Therefore, an increase in resistance due to the neutralized salt 33 can be further suppressed.

[0039] Here, in order to reduce the reaction resistance, it is better for the BET specific surface area of the positive electrode active material 31 to be large. On the other hand, the viscosity increases due to the reaction with LiOH 32. Therefore, an acid is added to generate the salt 33. On the other hand, the resistance increases because the generated salt 33 covers the surface of the positive electrode active material 31. Note that it is the LiOH 32 on the surface of the secondary particles 31B of the positive electrode active material 31 that affects the increase in viscosity, and the LiOH 32 inside the secondary particles 31B is less likely to be affected. Therefore, by adjusting the amount of acid added according to the physical properties of the positive electrode active material 31 to be equal to X or more and Y or less of LiOH 32 by formulas (1) and (2), only the LiOH 32 on the surface of the secondary particles 31B of the positive electrode active material 31 is neutralized. Note that if the density of the positive electrode active material 31 is increased to reduce the resistance, the voids in the positive electrode will decrease and the resistance will increase.

[0040] Also, by using a positive electrode active material 31 with a porosity of 25% or more and 50% or less, a particle size of the secondary particles 31B of 2 [μm] or more and 7 [μm] or less, and a BET specific surface area of 1.2 [m 2 / g] or more and 3.0 [m 2 / g] or less, the internal surface area can be made larger than the outer surface area of the secondary particles 31B of the positive electrode active material 31, the increase in viscosity can be suppressed, and the increase in resistance can be suppressed.

[0041] [Effect] Next, the effects of this embodiment will be described. (1) The amount of acid for neutralizing LiOH32 is adjusted according to the physical properties of the positive electrode active material 31, and only the LiOH32 on the surface of the secondary particles 31B of the positive electrode active material 31 that affects the increase in viscosity by reacting with the positive electrode binder is neutralized. Therefore, it is possible to suppress an increase in resistance while suppressing an increase in the viscosity of the positive electrode mixture.

[0042] (2) The crushing rate in the rolling process is set to 20 [%] or more and 40 [%] or less. For this reason, by causing the positive electrode active material 31 to crack and presenting a fresh surface that is not covered with the neutralized salt 33 that is a reaction product of LiOH32, an increase in resistance can be further suppressed.

[0043] [Other Embodiments] The above embodiment can be implemented with the following modifications. The above embodiment and the following modification examples can be implemented in combination with each other as long as they do not technically conflict with each other.

[0044] · In the above embodiment, the crushing rate in the rolling process is set to 20% or more and 40% or less. However, if an increase in resistance is within an allowable range, the crushing rate in the rolling process may be set outside the above range.

[0045] · In the above embodiment, the wound body obtained by winding the laminate in which the positive electrode sheet 21 and the negative electrode sheet 24 are laminated via the separator 27 is used as the electrode body 20. However, a laminate in which a plurality of positive electrode sheets 21 and a plurality of negative electrode sheets 24 are alternately laminated via the separator 27 may be used as the electrode body.

[0046] · The lithium ion secondary battery 10 may be mounted on a computer or other electronic devices in addition to an automatic transporter, a special vehicle for cargo handling, an electric vehicle, a hybrid vehicle, etc., and may also be configured for other systems. For example, it may be provided in a moving body such as a ship or an aircraft, or may be a power supply system that supplies power to a building or a home where a secondary battery is installed via a substation from a power plant.

[0047] [Example] Next, with reference to FIG. 5, examples and comparative examples of the lithium ion secondary battery 10 will be described. Note that these examples and comparative examples do not limit the manufacturing method of the non-aqueous secondary battery.

[0048] Hereinafter, as shown in FIG. 5, the particle size of the secondary particles 31B of the positive electrode active material 31, the BET specific surface area of the positive electrode active material 31, the porosity of the positive electrode active material 31, the crushing rate in the rolling process, the X equivalent amount of the acid for the purpose of neutralizing LiOH 32 contained in the positive electrode active material 31, the Y equivalent amount of the acid for the purpose of neutralizing LiOH 32 contained in the positive electrode active material 31, and the added acid amount were changed. Lithium ion secondary batteries 10 of examples and comparative examples were prepared. Then, for each example and each comparative example, the viscosity and electrode resistance of the positive electrode mixture paste were evaluated. The viscosity is measured with a rheometer. Note that the viscosity can also be measured with a B-type viscometer or an E-type viscometer. The electrode resistance is measured by fabricating a small laminated cell.

[0049] [Comparative Example 1] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 5 [μm], the BET specific surface area of the positive electrode active material 31 was set to 2 [m 2 / g], the porosity of the positive electrode active material 31 was set to 38 [%], and the crushing rate in the rolling process was set to 30 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH 32 contained in the positive electrode active material 31 was 0.068 equivalent, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH 32 contained in the positive electrode active material 31 was 0.111 equivalent. The added acid was 0.050 equivalent of LiOH 32.

[0050] [Comparative Example 2] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 5 [μm], the BET specific surface area of the positive electrode active material 31 was set to 2 [m 2As [ / g], the porosity of the positive electrode active material 31 was set to 38 [%], and the crushing rate in the rolling process was set to 30 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.068 equivalent, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.111 equivalent. And the added acid was 0.150 equivalent of LiOH32.

[0051] [Comparative Example 3] The particle size of the secondary particles 31B of the positive electrode active material 31 was 3 [μm], and the BET specific surface area of the positive electrode active material 31 was 2.8 [m 2 / g], the porosity of the positive electrode active material 31 was set to 31 [%], and the crushing rate in the rolling process was set to 45 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.099 equivalent, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.159 equivalent. And the added acid was 0.065 equivalent of LiOH32.

[0052] [Comparative Example 4] The particle size of the secondary particles 31B of the positive electrode active material 31 was 3 [μm], and the BET specific surface area of the positive electrode active material 31 was 2.8 [m 2 / g], the porosity of the positive electrode active material 31 was set to 31 [%], and the crushing rate in the rolling process was set to 45 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.099 equivalent, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.159 equivalent. And the added acid was 0.200 equivalent of LiOH32.

[0053] [Comparative Example 5] The particle size of the secondary particles 31B of the positive electrode active material 31 was 7 [μm], and the BET specific surface area of the positive electrode active material 31 was 1.2 [m 2As [ / g], the porosity of the positive electrode active material 31 was set to 45 [%], and the crushing rate in the rolling process was set to 22 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 became 0.029 equivalent amount, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 became 0.047 equivalent amount. And the added acid was set to 0.010 equivalent amount of LiOH32.

[0054] [Comparative Example 6] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 7 [μm], and the BET specific surface area of the positive electrode active material 31 was 1.2 [m 2 As [ / g], the porosity of the positive electrode active material 31 was set to 45 [%], and the crushing rate in the rolling process was set to 22 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 became 0.029 equivalent amount, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 became 0.047 equivalent amount. And the added acid was set to 0.065 equivalent amount of LiOH32.

[0055] [Example 1] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 5 [μm], and the BET specific surface area of the positive electrode active material 31 was 2 [m 2 As [ / g], the porosity of the positive electrode active material 31 was set to 38 [%], and the crushing rate in the rolling process was set to 30 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 became 0.068 equivalent amount, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 became 0.111 equivalent amount. And the added acid was set to 0.070 equivalent amount of LiOH32.

[0056] [Example 2] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 5 [μm], and the BET specific surface area of the positive electrode active material 31 was 2 [m 2As [ / g], the porosity of the positive electrode active material 31 was set to 38 [%], and the crushing rate in the rolling process was set to 30 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.068 equivalent, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.111 equivalent. And the added acid was 0.110 equivalent of LiOH32.

[0057] [Example 3] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 3 [μm], and the BET specific surface area of the positive electrode active material 31 was 2.8 [m 2 / g]. The porosity of the positive electrode active material 31 was set to 31 [%], and the crushing rate in the rolling process was set to 45 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.099 equivalent, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.159 equivalent. And the added acid was 0.100 equivalent of LiOH32.

[0058] [Example 4] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 3 [μm], and the BET specific surface area of the positive electrode active material 31 was 2.8 [m 2 / g]. The porosity of the positive electrode active material 31 was set to 31 [%], and the crushing rate in the rolling process was set to 45 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.099 equivalent, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 was 0.159 equivalent. And the added acid was 0.150 equivalent of LiOH32.

[0059] [Example 5] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 7 [μm], and the BET specific surface area of the positive electrode active material 31 was 1.2 [m 2As [ / g], the porosity of the positive electrode active material 31 was set to 45 [%], and the crushing rate in the rolling process was set to 22 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 is 0.029 equivalent amount, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 is 0.047 equivalent amount. And the added acid was 0.030 equivalent amount of LiOH32.

[0060] [Example 6] The particle size of the secondary particles 31B of the positive electrode active material 31 was set to 7 [μm], and the BET specific surface area of the positive electrode active material 31 was 1.2 [m 2 / g], the porosity of the positive electrode active material 31 was set to 45 [%], and the crushing rate in the rolling process was set to 22 [%]. Therefore, the X equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 is 0.029 equivalent amount, and the Y equivalent amount of the acid for the purpose of neutralizing LiOH32 contained in the positive electrode active material 31 is 0.047 equivalent amount. And the added acid was 0.045 equivalent amount of LiOH32.

[0061] [Evaluation] For each of the above examples and comparative examples, the viscosity and electrode resistance of the positive electrode composite paste were evaluated. The viscosity is evaluated based on whether the positive electrode composite paste can be applied to the positive electrode current collector 22. The electrode resistance is the measured value.

[0062] Example 1, which is 0.070 equivalent amount included in the range of 0.068 equivalent amount or more of the X equivalent amount and 0.111 equivalent amount or less of the Y equivalent amount obtained from the physical properties of the positive electrode active material 31, has a viscosity that is applicable for coating and a resistance of 474 [mΩ].

[0063] Example 2, which is 0.110 equivalent amount included in the range of 0.068 equivalent amount or more of the X equivalent amount and 0.111 or less of the Y equivalent amount obtained from the physical properties of the positive electrode active material 31, has a viscosity that is applicable for coating and a resistance of 475 [mΩ].

[0064] Comparative Example 1, which is 0.050 equivalents, is less than the range of 0.068 equivalents or more of the equivalent amount of X and 0.111 equivalents or less of the equivalent amount of Y obtained from the physical properties of the positive electrode active material 31, and has a viscosity that cannot be coated.

[0065] Comparative Example 2, which is 0.150 equivalents, is greater than the range of 0.068 equivalents or more of the equivalent amount of X and 0.111 equivalents or less of the equivalent amount of Y obtained from the physical properties of the positive electrode active material 31, has a viscosity that can be coated, and has a resistance of 483 [mΩ].

[0066] Example 3, which is 0.100 equivalents, is included in the range of 0.099 equivalents or more of the equivalent amount of X and 0.159 equivalents or less of the equivalent amount of Y obtained from the physical properties of the positive electrode active material 31, has a viscosity that can be coated, and has a resistance of 463 [mΩ].

[0067] Example 4, which is 0.150 equivalents, is included in the range of 0.099 equivalents or more of the equivalent amount of X and 0.159 equivalents or less of the equivalent amount of Y obtained from the physical properties of the positive electrode active material 31, has a viscosity that can be coated, and has a resistance of 464 [mΩ].

[0068] Comparative Example 3, which is 0.065 equivalents, is less than the range of 0.099 equivalents or more of the equivalent amount of X and 0.159 equivalents or less of the equivalent amount of Y obtained from the physical properties of the positive electrode active material 31, and has a viscosity that cannot be coated.

[0069] Comparative Example 4, which is 0.200 equivalents, is greater than the range of 0.099 equivalents or more of the equivalent amount of X and 0.159 equivalents or less of the equivalent amount of Y obtained from the physical properties of the positive electrode active material 31, has a viscosity that can be coated, and has a resistance of 476 [mΩ].

[0070] Example 5, which is 0.030 equivalents, is included in the range of 0.029 equivalents or more of the equivalent amount of X and 0.047 equivalents or less of the equivalent amount of Y obtained from the physical properties of the positive electrode active material 31, has a viscosity that can be coated, and has a resistance of 479 [mΩ].

[0071] Example 6, which contains 0.045 equivalent amounts within the range of 0.029 equivalent amounts or more of X equivalent amounts and 0.047 equivalent amounts or less of Y equivalent amounts obtained from the physical properties of the positive electrode active material 31, has a viscosity that enables coating and a resistance of 477 [mΩ].

[0072] Comparative Example 5, which is 0.010 equivalent amounts and is less than the range of 0.029 equivalent amounts or more of X equivalent amounts and 0.047 equivalent amounts or less of Y equivalent amounts obtained from the physical properties of the positive electrode active material 31, has a viscosity that is not suitable for coating.

[0073] Comparative Example 6, which is 0.065 equivalent amounts and is greater than the range of 0.099 equivalent amounts or more of X equivalent amounts and 0.047 equivalent amounts or less of Y equivalent amounts obtained from the physical properties of the positive electrode active material 31, has a viscosity that enables coating and a resistance of 489 [mΩ].

[0074] The porosity of the positive electrode active material 31 is 25 [%] or more and 50 [%] or less, the particle size of the secondary particles 31B of the positive electrode active material 31 is 2 [μm] or more and 7 [μm] or less, and the BET specific surface area of the positive electrode active material 31 is 1.2 [m 2 / g] or more and 3.0 [m 2 / g] or less, and Examples 1 to 6, in which the acid for the purpose of neutralizing LiOH 32 contained in the positive electrode active material 31 contains X or more and Y or less equivalent amounts of LiOH, enable the coating of the positive electrode composite paste, and the increase in the electrode resistance is suppressed compared to comparative examples with the same physical properties of the positive electrode active material. Excellent results were obtained in Examples 1 to 6.

[0075] Specifically, Examples 1 and 2 and Comparative Examples 1 and 2 use the same positive electrode active material, and the particle size of the secondary particles, BET specific surface area, and porosity are also selected to be similar. On the other hand, the acid amounts in Examples 1 and 2 and Comparative Examples 1 and 2 are added in different amounts. The acid amounts in Examples 1 and 2 are within the range of X or more and Y or less equivalent amounts of LiOH obtained by the above formulas (1) and (2), and the acid amounts in Comparative Examples 1 and 2 are outside the range of X or more and Y or less equivalent amounts of LiOH. Examples 1 and 2 were good in both viscosity and resistance. In contrast, Comparative Example 1 with a small acid amount had a low viscosity and was not suitable for coating. Also, Comparative Example 2 with a large acid amount had a good viscosity, but the resistance increased by about 10 mΩ compared to Examples 1 and 2.

[0076] Examples 3 and 4 and Comparative Examples 3 and 4 use the same positive electrode active material, and the secondary particle size, BET specific surface area, and porosity are also selected to be the same. On the other hand, different amounts of acid are added in Examples 3 and 4 and Comparative Examples 3 and 4. The amount of acid in Examples 3 and 4 is within the range of X or more and Y or less equivalent amounts of LiOH obtained by the above formulas (1) and (2), and the amount of acid in Comparative Examples 3 and 4 is outside the range of X or more and Y or less equivalent amounts of LiOH. Examples 3 and 4 had good viscosity and resistance. In contrast, Comparative Example 3 with a small amount of acid had a low viscosity and was not suitable for coating. Also, Comparative Example 4 with a large amount of acid had good viscosity, but the resistance increased by about 10 mΩ compared to Examples 3 and 4.

[0077] Examples 5 and 6 and Comparative Examples 5 and 6 use the same positive electrode active material, and the secondary particle size, BET specific surface area, and porosity are also selected to be the same. On the other hand, different amounts of acid are added in Examples 5 and 6 and Comparative Examples 5 and 6. The amount of acid in Examples 5 and 6 is within the range of X or more and Y or less equivalent amounts of LiOH obtained by the above formulas (1) and (2), and the amount of acid in Comparative Examples 5 and 6 is outside the range of X or more and Y or less equivalent amounts of LiOH. Examples 5 and 6 had good viscosity and resistance. In contrast, Comparative Example 5 with a small amount of acid had a low viscosity and was not suitable for coating. Also, Comparative Example 6 with a large amount of acid had good viscosity, but the resistance increased by about 10 mΩ compared to Examples 5 and 6.

Explanation of Symbols

[0078] 10…Lithium-ion secondary battery 11…Battery case 12…Cover 13A…Positive electrode external terminal 13B…Negative electrode external terminal 14A…Positive electrode side current collector member 14B…Negative electrode side current collector member 20…Electrode body 20A…Positive electrode side current collecting part 20B…Negative electrode side current collecting part 21…Positive electrode sheet 22…Positive electrode current collector 22A…Positive electrode side uncoated part 23…Positive electrode composite layer 24…Negative electrode sheet 25…Negative electrode current collector 25A…Unglazed portion on the negative electrode side 26…Negative electrode composite layer 27…Separator 31…Positive electrode active material 31A…Primary particle 31B…Secondary particle 32…LiOH 33…Salt

Claims

1. A non-aqueous secondary battery having a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte, The positive electrode mixture constituting the positive electrode sheet contains a positive electrode active material and a positive electrode binder, The porosity of the positive electrode active material is 25% or more and 50% or less, The particle size of the secondary particles, which are aggregates of primary particles of the positive electrode active material, is 2 μm or more and 7 μm or less, The BET specific surface area of the positive electrode active material is 1.2 m ２ / g or more and 3.0 m ２ / g or less, An acid for the purpose of neutralizing LiOH contained in the positive electrode active material is contained in an amount equal to X or more and Y or less of the LiOH, The X and the Y are obtained from the following formula X = 0.0013 × the particle size × (the BET specific surface area) ２ / the porosity Y = 0.0021 × the particle size × (the BET specific surface area) ２ / the porosity A non-aqueous secondary battery.

2. A method for manufacturing a non-aqueous secondary battery having a positive electrode sheet, a negative electrode sheet, and a non-aqueous electrolyte, A coating step of manufacturing the positive electrode sheet by coating a positive electrode substrate with a positive electrode mixture layer containing a positive electrode active material and a positive electrode binder, A rolling step of rolling the positive electrode sheet coated with the positive electrode mixture layer, and includes The porosity of the positive electrode active material is 25% or more and 50% or less, The particle size of the secondary particles, which are aggregates of primary particles of the positive electrode active material, is 2 μm or more and 7 μm or less, The BET specific surface area of the positive electrode active material is 1.2 m ２ / g or more and 3.0 m ２ / g or less, An acid for the purpose of neutralizing LiOH contained in the positive electrode active material is contained in an amount equal to X or more and Y or less of the LiOH, The X and the Y are obtained from the following formula X = 0.0013 × the particle size × (the BET specific surface area) ２ / the porosity Y = 0.0021 × the particle size × (the BET specific surface area) ２ / the porosity Method for manufacturing a non-aqueous secondary battery.

3. The crushing rate in the rolling process is 20% or more and 40% or less The method for manufacturing a non-aqueous secondary battery according to claim 2.

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