Non-aqueous electrolyte secondary battery

Abstract

A nonaqueous electrolyte secondary battery has an electrode body and a nonaqueous electrolyte, the electrode body being formed by alternately stacking a positive electrode and a negative electrode with a separator therebetween, the positive electrode having a positive electrode core and a positive electrode composite layer containing a positive electrode active material. The positive electrode active material has a median particle diameter (D50) of 5.0 to 7.0 μm on a volume basis, a BET specific surface area of 2.00 to 3.00 m 2 / g, and a TAP density of 1.30 to 1.70 g / cm 3 , and the positive electrode composite layer has a density of 2.3 to 2.5 g / cm 3 .

Description

Technical Field

[0001] This application relates to non-aqueous electrolyte secondary batteries. Background Technology

[0002] Non-aqueous electrolyte secondary batteries have an electrode body and a non-aqueous electrolyte. The electrode body is formed by alternating layers of positive and negative electrodes separated by a separator. The positive electrode has a positive electrode core and a positive electrode composite material layer containing positive electrode active material (e.g., Patent Document 1). Non-aqueous electrolytic secondary batteries are used as power sources for hybrid electric vehicles and electric vehicles, and are used in low-temperature and normal-temperature environments.

[0003] To improve the output characteristics of the non-aqueous electrolyte under low and normal temperature conditions, it is necessary to increase the density of the positive electrode composite layer to ensure conductive pathways and reduce internal resistance. Furthermore, especially to improve output characteristics at low temperatures, it is necessary to increase the specific surface area (BET) of the positive electrode active material and reduce the charge transfer resistance at the interface between the non-aqueous electrolyte and the positive electrode active material. To increase the specific surface area (BET) of the positive electrode active material, reducing its particle size can be considered.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2016-25041 Summary of the Invention

[0007] As mentioned above, increasing the density of the positive electrode composite layer and decreasing the particle size of the positive electrode active material reduces the pore size of the positive electrode composite layer and decreases the permeability of the non-aqueous electrolyte. As a result, in the manufacture of non-aqueous electrolyte secondary batteries, a longer time is required from the injection of the non-aqueous electrolyte liquid until the non-aqueous electrolyte permeates to the positive electrode, thus reducing manufacturing efficiency.

[0008] One embodiment of this application is a non-aqueous electrolyte secondary battery comprising an electrode body and a non-aqueous electrolyte. The electrode body is composed of alternating layers of a positive electrode and a negative electrode separated by a separator. The positive electrode has a positive electrode core and a positive electrode composite material layer containing positive electrode active material. The median particle size (D50) of the positive electrode active material is 5.0–7.0 μm (volume reference), and the BET specific surface area of ​​the positive electrode active material is 2.00–3.00 m². 2 The TAP density of the positive electrode active material is 1.30–1.70 g / cm³. 3 The density of the positive electrode composite layer is 2.3–2.5 g / cm³. 3 .

[0009] According to one aspect of this application, the output characteristics at room temperature and low temperature can be improved, and the permeability of non-aqueous electrolytes during injection can be enhanced. Attached Figure Description

[0010] Figure 1 This is a perspective view illustrating one embodiment, namely a non-aqueous electrolyte secondary battery. Detailed Implementation

[0011] The embodiments of this application are described below using the accompanying drawings. The shapes, materials, and quantities described below are illustrative and may be appropriately varied according to the specifications of non-aqueous electrolyte secondary batteries. Hereinafter, equivalent elements are labeled with the same symbols throughout the drawings.

[0012] [Non-aqueous electrolyte secondary battery]

[0013] Hereinafter, a detailed description of an embodiment of this application will be provided. In this embodiment, a secondary battery 10 having a square metal casing 12 is shown. However, the casing is not limited to a square shape; it can be, for example, cylindrical, coin-shaped, or a battery casing made of a laminate containing a metal layer and a resin layer. Furthermore, a wound electrode body 11 formed by winding the positive and negative electrodes with a separator is shown. A stacked electrode body formed by alternately stacking multiple positive and multiple negative electrodes with separators is also possible. Regarding both the positive and negative electrodes, an example is shown where each composite material layer is formed on both sides of each core. However, it is not limited to the case where each composite material layer is formed on both sides of each core; it is sufficient as long as at least one surface is formed.

[0014] like Figure 1 As shown, the secondary battery 10 includes a wound electrode body 11, an electrolyte, and an outer casing 12 for housing the electrode body 11 and the electrolyte. The wound electrode body 11 is formed by winding the positive and negative electrodes together with a separator, and is shaped into a flat shape with a flat portion and a pair of curved portions. The outer casing 12 and the sealing plate 13 are both made of metal, such as aluminum or aluminum alloy.

[0015] The outer casing 12 has a bottom that is generally rectangular in shape when viewed from below and sidewalls provided at the bottom edge. The sidewalls are formed perpendicular to the bottom. The dimensions of the outer casing 12 are not particularly limited; for example, the lateral length is 60 to 160 mm, the height is 60 to 100 mm, and the thickness is 10 to 40 mm.

[0016] The positive electrode is a strip having a metallic positive electrode core and positive electrode composite material layers formed on both sides of the core, with a strip-shaped positive electrode core exposure portion 15 formed at one end in the width direction, exposing the positive electrode core along the length direction. Similarly, the negative electrode is a strip having a metallic negative electrode core and negative electrode composite material layers formed on both sides of the core, with a strip-shaped negative electrode core exposure portion 16 formed at one end in the width direction, exposing the negative electrode core along the length direction. The electrode body 11 has the following structure: with the positive electrode core exposure portion 15 of the positive electrode arranged on one end side of the axial direction and the negative electrode core exposure portion 16 of the negative electrode arranged on the other end side of the axial direction, the positive electrode and the negative electrode are wound around a separator.

[0017] Specifically, the positive current collector 17 is connected to the stacked portion of the positive electrode core exposed portion 15 of the positive electrode, and the negative current collector 18 is connected to the stacked portion of the negative electrode core exposed portion 16 of the negative electrode. A suitable positive current collector 17 is made of aluminum or an aluminum alloy. A suitable negative current collector 18 is made of copper or a copper alloy. The positive terminal 21 has: a positive external conductive portion 22 disposed on the battery exterior side of the sealing plate 13, a positive bolt portion 23 connected to the positive external conductive portion 22, and a positive insertion portion 24 inserted into a through hole provided in the sealing plate 13. The positive terminal 21 is electrically connected to the positive current collector 17. In addition, the negative terminal 25 has: a negative external conductive part 26 disposed on the battery external side of the sealing plate 13, a negative bolt part 27 connected to the negative external conductive part 26, and a negative insertion part 28 inserted into the through hole provided in the sealing plate 13. The negative terminal 25 is electrically connected to the negative current collector 18.

[0018] The positive terminal 21 and the positive current collector 17 are fixed to the sealing plate 13 by means of an internal insulating member and an external insulating member, respectively. The internal insulating member is disposed between the sealing plate 13 and the positive current collector 17, and the external insulating member is disposed between the sealing plate 13 and the positive terminal 21. Similarly, the negative terminal 25 and the negative current collector 18 are fixed to the sealing plate 13 by means of an internal insulating member and an external insulating member, respectively. The internal insulating member is disposed between the sealing plate 13 and the negative current collector 18, and the external insulating member is disposed between the sealing plate 13 and the negative terminal 25.

[0019] The electrode body 11 is housed within the outer casing 12. A sealing plate 13 is connected to the opening edge of the outer casing 12 by laser welding or the like. The sealing plate 13 has an electrolyte injection hole 32, which is sealed with a sealing plug after electrolyte liquid is injected into the outer casing 12. The sealing plate 13 also has an exhaust valve 31 for releasing gas when the internal pressure of the battery reaches a specified value.

[0020] The following details the positive electrode, negative electrode, and separator that constitute the electrode body 11, especially the positive electrode composite material layer and positive electrode active material that constitute the positive electrode.

[0021] [positive electrode]

[0022] The positive electrode comprises a positive electrode core and a positive electrode composite material layer formed on the surface of the positive electrode core. The positive electrode core can be made of a foil of a metal stable within the positive electrode potential range, such as aluminum or aluminum alloy, or a thin film with a metal layer disposed on its surface. The thickness of the positive electrode core is, for example, 10 μm to 20 μm. The thickness of the positive electrode composite material layer is, for example, 10 μm to 150 μm on one side of the positive electrode core. The positive electrode is manufactured by coating the surface of the positive electrode core with a positive electrode composite material slurry containing a positive electrode active material, a conductive material, and a binder, and then compressing the slurry after drying.

[0023] Examples of conductive materials included in the cathode composite layer include carbon materials such as carbon black, acetylene black, Ketjen black, carbon nanotubes, and graphite. Examples of binders included in the cathode composite layer include fluoropolymers such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF); polyacrylonitrile (PAN), polyimide, acrylic resins, and polyolefins. These resins can also be used in combination with carboxymethyl cellulose (CMC) or its salts, polyethylene oxide (PEO), etc.

[0024] [Active Substances]

[0025] As a positive electrode active material, it is a metal oxide containing at least lithium and a transition metal element, such as Mn, Ni, and Co. The added element in the lithium-containing transition metal oxide is not limited to Mn, Ni, and Co, and can include other added elements. Examples of other added elements include alkali metals other than lithium; transition metals other than Mn, Ni, and Co; alkaline earth metals; Group 12 elements; Group 13 elements; and Group 14 elements. Specific examples of other added elements include Zr, B, Mg, Al, Ti, Fe, Cu, Zn, Sn, Na, K, Ba, Sr, and Ca. Among these, Zr is suitable. It can be considered that by containing Zr, the crystal structure of the lithium-containing transition metal oxide is stabilized, and the durability and cycle performance of the positive electrode composite layer at high temperatures are improved. The Zr content in the lithium-containing transition metal oxide is preferably 0.05 mol% or more and 10.00 mol% or less relative to the total amount of metals other than Li, more preferably 0.10 mol% or more and 5.00 mol% or less, and particularly preferably 0.20 mol% or more and 3.00 mol% or less.

[0026] As the positive electrode active material, for example, it is a lithium metal composite oxide containing at least one element selected from Ni, Co, and Mn. The lithium metal composite oxide is represented by the general formula Li 1+x Ni a Mn b Co c O2, and preferably satisfies the conditions of a + b + c = 1, 0 < x ≤ 0.3, a ≥ b, a ≥ c, 0 < c / (a + b) < 0.65, and 1.0 ≤ a / b ≤ 3.0.

[0027] The median particle diameter (D50) of the positive electrode active material based on volume is preferably 5.0 to 7.0 μm, more preferably 6.0 to 7.0 μm. The median particle diameter (D50) is the particle diameter at which the volume accumulation value in the particle size distribution measured by the laser diffraction scattering method reaches 50%, and is also called the 50% particle diameter or median diameter. The D50 of the positive electrode active material is measured using a laser diffraction type particle size distribution measuring device (manufactured by SHIMAZU Corporation, SALD - 2200). In addition, the BET specific surface area of the positive electrode active material is preferably 2.00 to 3.00 m 2 / g, more preferably 2.20 to 2.40 m 2 / g.

[0028] Thereby, the reaction area of the positive electrode active material becomes larger, and by reducing the charge transfer resistance at the interface between the positive electrode active material and the electrolyte, the output characteristics of the secondary battery 10 in a low - temperature environment can be improved.

[0029] The TAP density of the positive electrode active material is preferably 1.30 to 1.70 g / cm 3 、more preferably 1.60 to 1.70 g / cm 3 . The TAP density refers to the volume density measured by vibrating the powder when it is filled into a container to further pack it. The TAP density can be measured using a powder reduction degree measuring device (manufactured by Tsutsui Rikagaku Kikai Co., Ltd., TPM - 1). Specifically, 50 g of the sample (powder) can be filled into a 150 - ml glass graduated cylinder, and the powder is oscillated 1000 times with a 30 - mm stroke using the powder reduction degree measuring device, and the powder packing density at this time is obtained, and this density is measured as the TAP density. In addition, the density of the positive electrode composite layer is preferably 2.3 to 2.5 g / cm 3 、more preferably 2.4 g / cm 3 . Thereby, by ensuring the conductive path in the positive electrode and reducing the internal resistance, the output characteristics of the secondary battery 10 can be improved.

[0030] For example, when increasing the density of the cathode composite layer to improve output characteristics at low and normal temperatures, or increasing the specific surface area (BET) of the cathode active material while decreasing the particle size of the cathode active material to improve output characteristics at low temperatures, the pore size of the cathode composite layer becomes smaller, and the permeability of the non-aqueous electrolyte decreases. However, in this embodiment, by setting the D50 particle size and TAP density of the cathode active material to appropriate values, the drawback of a smaller pore size in the cathode composite layer is avoided.

[0031] In this embodiment, the median pore size of the positive electrode composite material layer in terms of volume reference is preferably 0.5–0.7 μm, more preferably 0.6–0.7 μm. The median pore size is the median pore size in terms of volume reference measured using the mercury injection method, and can be measured using an automatic mercury porosimeter (Shimadzu Corporation - MICROMERITICS, AUTOPORE V9620). This avoids reducing the permeability of non-aqueous electrolytes.

[0032] The positive electrode active material of this embodiment is manufactured as follows. First, a solution is prepared by dissolving a Ni source containing a nickel compound, a Co source containing a cobalt compound, and a Mn source containing a manganese compound in a solvent. An appropriate amount of alkali is added to the solution under suitable mixing conditions to obtain a precipitate. This precipitate is then washed with water, dehydrated, and dried to produce a precursor of a lithium nickel cobalt manganese composite oxide (hereinafter referred to as the NCM precursor). This precursor is then mixed with a Li raw material in an appropriate amount and calcined, followed by crushing under appropriate conditions to produce a positive electrode active material with the aforementioned particle size. The D50, BET specific surface area, TAP density, density of the positive electrode composite layer, median pore size, etc., of the positive electrode active material of this embodiment can be adjusted to the target range by changing the crystallization conditions and the calcination conditions described above.

[0033] [negative electrode]

[0034] The negative electrode comprises a negative electrode core and negative electrode composite material layers formed on both sides of the negative electrode core. The negative electrode core can be made of a foil of a metal stable within the negative electrode's potential range, such as copper or a copper alloy, or a thin film of the same metal disposed on its surface. The negative electrode composite material layers contain a negative electrode active material and a binder material. The thickness of the negative electrode composite material layer is, for example, 10 μm to 150 μm on one side of the negative electrode core. The negative electrode is manufactured by coating the surface of the negative electrode core with a negative electrode composite material slurry containing a negative electrode active material and a binder material, drying the coating, and then calendering it to form the negative electrode composite material layers on both sides of the negative electrode core.

[0035] As the negative electrode active material contained in the negative electrode composite material layer, there is no particular limitation as long as it can reversibly occlude and release lithium ions, and carbon materials such as graphite are usually used. The graphite can be any of natural graphite such as flake graphite, massive graphite, and earthy graphite; artificial graphite such as massive artificial graphite and graphitized mesophase carbon microbeads. In addition, as the negative electrode active material, metals that alloy with Li such as Si and Sn can be used; metal compounds containing Si, Sn, etc.; lithium titanium composite oxides, etc. In addition, substances provided with a carbon coating film on them can also be used. For example, a silicon-containing compound represented by SiO x (0.5 ≤ x ≤ 1.6) or a silicon-containing compound in which Si fine particles are dispersed in a lithium silicate phase represented by Li 2y SiO (2+y) (0 < y < 2) can be used in combination with graphite. <00 / /

[0036] Similar to the case of the positive electrode, the binder contained in the negative electrode composite material layer can use fluorine-containing resins such as PTFE and PVdF; PAN, polyimide, acrylic resins, polyolefins, etc., and styrene-butadiene rubber (SBR) is preferably used. In addition, the negative electrode composite material layer can contain CMC or its salts, polyacrylic acid (PAA) or its salts, polyvinyl alcohol (PVA), etc.

[0037] [Separator]

[0038] For the separator, a porous sheet having ion permeability and insulation, for example, can be used. Specific examples of the porous sheet include microporous films, woven fabrics, non-woven fabrics, etc. As the material of the separator, polyolefins such as polyethylene and polypropylene; cellulose, etc. are suitable. The separator can have a single-layer structure or a laminated structure. In addition, a resin layer with high heat resistance such as an aromatic polyamide resin or a filler layer containing an inorganic compound filler can be provided on the surface of the separator.

[0039] [Non-aqueous electrolyte]

[0040] The non-aqueous electrolyte contains, for example, a non-aqueous solvent and an electrolyte salt dissolved in the non-aqueous solvent. As the non-aqueous solvent, for example, esters, ethers, nitriles such as acetonitrile, amides such as dimethylformamide, and mixed solvents of two or more of them can be used. The non-aqueous solvent can contain halogenated products obtained by substituting at least a part of the hydrogen in these solvents with halogen atoms such as fluorine. As the halogenated product, fluorinated cyclic carbonates such as fluoroethylene carbonate (FEC), fluorinated chain carbonates, fluorinated chain carboxylic acid esters such as methyl fluoropropionate (FMP), etc. can be cited.

[0041] Examples of the above esters include cyclic carbonates such as ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate; chain carbonates such as dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), diethyl carbonate (DEC), methyl propyl carbonate, ethyl propyl carbonate, methyl isopropyl carbonate; cyclic carboxylic acid esters such as γ-butyrolactone (GBL), γ-valerolactone (GVL); chain carboxylic acid esters such as methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), ethyl propionate (EP), etc.

[0042] Examples of the above ethers include cyclic ethers such as 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-epoxybutane, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, crown ethers; chain ethers such as 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether, o-dimethoxybenzene, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, etc.

[0043] The electrolyte salt is preferably a lithium salt. Examples of the lithium salt include LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiCF3SO3, LiCF3CO2, Li(P(C2O4)F4), LiPF 6-x (C n F 2n+1 ) x (1 < x < 6, n is 1 or 2), LiB 10 Cl 10 , LiCl, LiBr, LiI, lithium chloroborane, lithium lower aliphatic carboxylate, borate salts such as Li2B4O7, Li(B(C2O4)F2); LiN(SO2CF3)2, LiN(C

[0042] Examples of the above ethers include cyclic ethers such as 1,3-dioxolane, 4-methyl-1,3-dioxolane, tetrahydrofuran, 2-methyltetrahydrofuran, propylene oxide, 1,2-epoxybutane, 1,3-dioxane, 1,4-dioxane, 1,3,5-trioxane, furan, 2-methylfuran, 1,8-cineole, crown ethers; chain ethers such as 1,2-dimethoxyethane, diethyl ether, dipropyl ether, diisopropyl ether, dibutyl ether, dihexyl ether, ethyl vinyl ether, butyl vinyl ether, methyl phenyl ether, ethyl phenyl ether, butyl phenyl ether, pentyl phenyl ether, methoxytoluene, benzyl ethyl ether, diphenyl ether, dibenzyl ether, o-dimethoxybenzene, 1,2-diethoxyethane, 1,2-dibutoxyethane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol dibutyl ether, 1,1-dimethoxymethane, 1,1-diethoxyethane, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, etc.

[0043] The electrolyte salt is preferably a lithium salt. Examples of the lithium salt include LiBF4, LiClO4, LiPF6, LiAsF6, LiSbF6, LiAlCl4, LiSCN, LiCF3SO3, LiCF3CO2, Li(P(C2O4)F4), LiPF 6-x (C n F 2n+1 ) x (1 < x < 6, n is 1 or ] <0000] Cl [[ID=] 、LiCl、LiBr、LiI、氯硼烷锂、低级脂肪族羧酸锂、Li2B4O7、Li(B(C2O4)F2)等硼酸盐类;LiN(SO2CF3)2、LiN(C l F 2l+1 SO2)(C m F 2m+1 It seems there are some incomplete or incorrect parts in the original text after ID=14 which might affect the accurate translation. Please check and correct the original text for a more precise translation.Imidamine salts such as SO2 (where l and m are integers greater than or equal to 0) are used. One type of lithium salt can be used alone, or multiple types can be used in combination. Among these, LiPF6 is preferred from the viewpoint of ionic conductivity and electrochemical stability. The concentration of the lithium salt is, for example, 0.8 mol to 1.8 mol per liter of a non-aqueous solvent. Furthermore, vinylene carbonate and propanesulfonate lactone additives can be further added.

[0044] It should be noted that the present invention is not limited to the above-described embodiments and their variations, and needless to say, various changes and improvements can be made within the scope of the claims of this application.

[0045] <Example>

[0046] The present application is further illustrated below by way of examples, but the present application is not limited to these examples.

[0047] <Example 1>

[0048] [Preparation of positive electrode active material]

[0049] A solution is prepared by dissolving Ni source containing nickel compounds, Co source containing cobalt compounds, and Mn source containing manganese compounds in solvent. An appropriate amount of alkali is added to the solution under suitable mixing conditions to obtain a precipitate. This precipitate is then washed with water and dehydrated to produce an NCM precursor. The NCM precursor is then mixed with a suitable amount of Li raw material and calcined, followed by crushing under appropriate conditions to produce a positive electrode active material with a median particle size (D50) of 5.9 μm.

[0050] [Making the positive electrode plate]

[0051] LiNi will be used as the positive electrode active material 0.35 Co 0.35 Mn 0.30 Lithium nickel cobalt manganese composite oxide (O2), carbon powder as a conductive material, and polyvinylidene fluoride (PVdF) as a binder are mixed with N-methyl-2-pyrrolidone (NMP) as a dispersion medium to prepare a cathode composite slurry. Here, the mass ratio of the cathode active material, conductive material, and binder in the cathode composite slurry is set to 90:7:3.

[0052] The cathode composite slurry prepared by the above method is coated onto both sides of an aluminum foil with a thickness of 15 μm, which serves as the cathode core, using a die coating machine. The cathode composite slurry is then dried to remove NMP, which is used as a dispersion medium. The cathode active material composite layer is compressed using a pair of compression rollers. Finally, the cathode plate is cut to a specified size, forming an exposed portion of the cathode core without the cathode active material composite layer on one end, thus producing the cathode plate.

[0053] [Making the negative electrode plate]

[0054] A negative electrode composite slurry was prepared by dispersing graphite powder (as the negative electrode active material), carboxymethyl cellulose (CMC) (as the tackifier), and styrene-butadiene rubber (SBR) (as the binder) in water at a mass ratio of 99.2:0.6:0.2.

[0055] The negative electrode composite slurry prepared by the above method is coated onto both sides of an 8μm thick copper foil, which serves as the negative electrode core, using a die coating machine. Next, the negative electrode composite slurry is dried to remove water, which is the dispersion medium, and then compressed using a roller press to achieve a specified thickness. Finally, the negative electrode plate is cut to a specified size, forming exposed portions of the negative electrode core at both ends in the width direction, where the negative electrode active material composite layer is not formed on either side, thus producing the negative electrode plate.

[0056] [Preparation of non-aqueous electrolytes]

[0057] A mixed solvent was prepared by mixing ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and methylene propionate (MP) in a volume ratio of 25:37:35:3 (25°C, 1 atm). LiPF6 was added as a solute to this mixed solvent at a concentration of 1.15 mol / L, and then lithium fluorosulfonate was added at 1% by mass relative to the non-aqueous electrolyte to prepare the non-aqueous electrolyte.

[0058] [Battery Manufacturing]

[0059] An electrode body, formed by winding the positive and negative electrode plates together with a separator, is inserted into an outer shell made of aluminum laminated film. After injecting electrolyte, the shell is sealed to produce a non-aqueous electrolyte secondary battery with a designed capacity of 0.14Ah.

[0060] [Particle size distribution determination of positive electrode active material]

[0061] Particle size distribution was determined using a laser diffraction / scattering method (SHIMAZU, SALD-2200).

[0062] [Determination of the specific surface area (BET) of the positive electrode active material]

[0063] The determination was performed using the BET single-point method (manufactured by MOUNTECH, Macsorb).

[0064] [Determination of TAP density of positive electrode active material]

[0065] 50g of the sample (positive electrode active material powder) was placed in a 150cm container. 3 In a glass graduated cylinder, a powder reduction tester is used to oscillate 1000 times with a stroke of 30 mm to determine the powder filling density at this time. This density is then used as the TAP density.

[0066] [Determination of median aperture]

[0067] The median pore size was determined using an automatic mercury impingement porosimeter (manufactured by Shimadzu Corporation - MICROMERITICS, AUTOPORE V9620) via the mercury injection method.

[0068] [Density of the positive electrode composite layer]

[0069] Cut 10cm from the positive electrode plate 2 The thickness and mass of the test piece are measured, and the thickness, area and mass of the positive electrode composite material layer are calculated based on the results after subtracting the thickness and mass of the positive electrode core.

[0070] [Determination of output characteristics under normal temperature conditions]

[0071] The non-aqueous electrolyte secondary battery was subjected to CCCV charging at 1 / 10 It at 25°C until the depth of charge (SOC) reached 50%. The battery was then left at 25°C for 2 hours. Subsequently, it was discharged at 25°C for 10 seconds at currents of 1 It, 2 It, 4 It, 8 It, 10 It, 12 It, and 16 It, and the battery voltage was measured. The current values ​​and battery voltages were plotted, and the output power (W) was calculated from the discharge IV characteristics as the room temperature output characteristic. It should be noted that the depth of charge deviating due to discharge was restored to the original depth of charge by charging with a constant current of 1 It.

[0072] [Determination of output characteristics under low temperature conditions]

[0073] The non-aqueous electrolyte secondary battery was subjected to CCCV charging at 25°C with a charging current of 1 / 10 It until the depth of charge (SOC) reached 50%. Then, the non-aqueous electrolyte secondary battery was placed at -30°C for 2 hours. Subsequently, at -30°C, it was discharged for 10 seconds at currents of 1 It, 2.4 It, 3.6 It, 4.8 It, 6.0 It, 7.2 It, and 8.4 It, and the battery voltage was measured. The current values ​​and battery voltages were plotted, and the output power (W) was calculated from the IV characteristics during discharge, serving as the low-temperature output characteristic. It should be noted that the depth of charge deviating due to discharge was restored to the original depth of charge by charging with a constant current of 0.2 It.

[0074] [Determination of infiltration time]

[0075] Using 1cm 3 The micropipette is used to add propylene carbonate to the surface of the positive electrode plate, and the time until the droplet penetrates is measured as the penetration time.

[0076] <Example 2>

[0077] In the preparation conditions of the positive electrode active material, the crystallization conditions and calcination conditions were changed so that the D50, BET specific surface area, TAP density, density of the positive electrode composite material layer and median pore size of the positive electrode active material shown in Table 1 could be obtained. Otherwise, the battery was prepared in the same manner as in Example 1.

[0078] <Comparative Examples 1-13>

[0079] In the preparation conditions of the positive electrode active material, the crystallization conditions and calcination conditions were controlled in a way that could obtain the D50, BET specific surface area, TAP density, density of the positive electrode composite material layer and median pore size shown in Table 1. Otherwise, the battery was prepared in the same manner as in Example 1.

[0080] [Table 1]

[0081]

[0082] [Example]

[0083] In the non-aqueous electrolyte secondary batteries of Examples 1 and 2, the BET specific surface area of ​​the positive electrode active material is 2.00–3.00 m². 2 The TAP density of the positive electrode active material is 1.30–1.70 g / cm³, thus increasing the reaction area and decreasing the charge transfer resistance during low-temperature discharge, thereby improving the output characteristics at low temperatures. Furthermore, the TAP density of the positive electrode active material is 1.30–1.70 g / cm³. 3 The density of the positive electrode composite layer is 2.3–2.5 g / cm³.3 Therefore, the conductive path of the positive electrode can be ensured, the internal resistance is reduced, and thus the output characteristics at room temperature are improved. Furthermore, by making the particle size of the positive electrode active material 5.0–7.0 μm and the density of the positive electrode composite layer 2.3–2.5 g / cm³, the output characteristics are further improved. 3 Thus, the median pore size of the positive electrode composite layer is 0.5–0.7 μm, which can shorten the impregnation time when injecting non-aqueous electrolyte.

[0084] [Comparative Example]

[0085] In the non-aqueous electrolyte secondary batteries of Comparative Examples 1-3, the discharge resistance increased at room temperature. This can be attributed to the fact that although the particle size was 5.0–7.0 μm and the BET specific surface area was 2.00–3.00 m², the resistance still increased. 2 / g, but the density of the positive electrode composite layer is approximately 2.0 g / cm³. 3 Therefore, the conductive path of the positive electrode composite material layer cannot be fully guaranteed, and the internal resistance increases.

[0086] In the non-aqueous electrolyte secondary battery of Comparative Example 4, the immersion time during electrolyte injection is longer. This is because the particle size is approximately 4.0 μm, therefore, the pore size of the positive electrode composite material layer is smaller.

[0087] In the non-aqueous electrolyte secondary batteries of Comparative Examples 5-7, the immersion time during electrolyte injection was longer. This can be attributed to the fact that the density of the positive electrode composite layer is approximately 2.8 g / cm³. 3 The aperture becomes smaller.

[0088] In the non-aqueous electrolyte secondary batteries of Comparative Examples 8-13, the discharge resistance increases at low temperatures. This can be attributed to the following: the BET specific surface area of ​​the positive electrode active material is small, and the charge transfer resistance at the interface between the non-aqueous electrolyte and the positive electrode active material is large.

[0089] Industrial availability

[0090] 10 Non-aqueous electrolyte secondary batteries

[0091] 11 Electrode Body

[0092] 12 outer shell

[0093] 13 Sealing Board

[0094] 15 Exposed portion of positive electrode core

[0095] 16 Exposed part of negative electrode core

[0096] 17 Positive current collector

[0097] 18 negative current collector

[0098] 21 positive extremes

[0099] 22 Positive external conductive part

[0100] 23 Positive electrode bolt section

[0101] 24 Positive Insertion Section

[0102] 25 negative extremes

[0103] 26 External conductive part of negative electrode

[0104] 27 Negative electrode bolt section

[0105] 28 Negative electrode insertion section

[0106] 31 Electrolyte Injection Hole

[0107] 32 exhaust valve

Claims

1. A nonaqueous electrolyte secondary battery having an electrode body and a nonaqueous electrolyte, the electrode body being formed by alternately stacking a positive electrode and a negative electrode with a separator therebetween, the positive electrode having a positive electrode core and a positive electrode composite layer containing a positive electrode active material, a median particle diameter (D50) of the positive electrode active material on a volume basis is 5.0 to 7.0 μm, The BET specific surface area of the positive electrode active material is 2.00 to 3.00 m 2 / g, The TAP density of the positive electrode active material is 1.30 to 1.70 g / cm 3 , The density of the positive electrode composite layer is 2.3 to 2.5 g / cm 3 , The positive electrode active material is a lithium metal complex oxide represented by the general formula Li 1+x Ni a Mn b Co c O2, the general formula satisfying the conditions of a+b+c=1, 0 a median pore diameter of the positive electrode composite layer is 0.5 to 0.7 μm.

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