Positive electrode for nonaqueous electrolyte secondary battery, nonaqueous electrolyte secondary battery using the same, and positive electrode slurry

Abstract

This positive electrode for a nonaqueous electrolyte secondary battery disclosed herein comprises: a positive electrode current collector; and a positive electrode mixture layer that is disposed on the positive electrode current collector. The positive electrode mixture layer contains a positive electrode active material containing a transition metal element, a binder, a conductive material, and a compound represented by formula (1) (R1 and R2 are each independently a hydrogen atom or a hydrocarbon group. X includes at least one of a hydrocarbon group and an oxygen atom).

Description

Positive electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery using the same, and positive electrode slurry.

[0001] This disclosure relates to a positive electrode for a non-aqueous electrolyte secondary battery, a non-aqueous electrolyte secondary battery using the same, and a positive electrode slurry.

[0002] Non-aqueous electrolyte secondary batteries offer high power output and high energy density, making them widely used in consumer and automotive applications. In recent years, there has been a growing demand for even higher performance in non-aqueous electrolyte secondary batteries. Various proposals have been made regarding non-aqueous electrolyte secondary batteries.

[0003] Claim 1 of Patent Document 1 (Japanese Unexamined Patent Publication No. 2010-049903) describes a battery composition for producing battery electrodes, comprising "one or more derivatives selected from the group consisting of organic dye derivatives having acidic functional groups and triazine derivatives having acidic functional groups, a resin having basic functional groups, and a carbon material as a conductive additive."

[0004] Japanese Patent Publication No. 2010-049903

[0005] The positive electrode of a non-aqueous electrolyte secondary battery is manufactured using a positive electrode slurry containing a positive electrode active material. Lowering the viscosity of the positive electrode slurry makes it easier to improve the uniformity of the coating film formed by the slurry, and as a result, manufacturing becomes easier. On the other hand, if the amount of binder is reduced to lower the viscosity of the positive electrode slurry, the adhesion between the positive electrode current collector and the positive electrode mixture layer decreases. Therefore, there is currently a need for a positive electrode that is easy to manufacture and has high adhesion between the positive electrode current collector and the positive electrode mixture layer. One of the objectives of this disclosure is to provide a positive electrode that is easy to manufacture and has high adhesion between the positive electrode current collector and the positive electrode mixture layer.

[0006] One aspect of this disclosure is a positive electrode for a non-aqueous electrolyte secondary battery, comprising a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, wherein the positive electrode mixture layer comprises a positive electrode active material containing a transition metal element, a binder, a conductive material, and the following formula (1) (R １ and R ２The present invention relates to a positive electrode for a non-aqueous electrolyte secondary battery comprising a compound represented by (where each is independently a hydrogen atom or a hydrocarbon group, and X contains at least one of a hydrocarbon group and an oxygen atom).

[0007] Another aspect of this disclosure relates to a non-aqueous electrolyte secondary battery, comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte.

[0008] Another aspect of this disclosure relates to a positive electrode slurry used in the manufacture of a positive electrode for a non-aqueous electrolyte secondary battery, comprising a positive electrode active material containing a transition metal element, a binder, a conductive material, a liquid medium, and a compound represented by formula (1) above.

[0009] According to this disclosure, it is possible to obtain a positive electrode (a positive electrode for non-aqueous electrolyte secondary batteries) that is easy to manufacture and has high adhesion between the positive electrode current collector and the positive electrode mixture layer. Novel features of the present invention are described in the appended claims, but the present invention, in conjunction with other objects and features of the present invention, will be better understood by the following detailed description in reference to the drawings, both in terms of structure and content.

[0010] This is a schematic cross-sectional view showing an example of a positive electrode related to this disclosure. This is a schematic cross-sectional view showing an example of a non-aqueous electrolyte secondary battery related to this disclosure.

[0011] The embodiments relating to this disclosure will be described below with examples, but this disclosure is not limited to the examples described below. In the following description, specific numerical values ​​and materials may be given as examples, but other numerical values ​​and materials may be applied as long as the effects of this disclosure are obtained. In this specification, the description "numerical value A to numerical value B" includes numerical value A and numerical value B, and can be read as "greater than or equal to numerical value A and less than or equal to numerical value B". In the following description, when lower and upper limits of numerical values ​​relating to specific physical properties or conditions are given as examples, either the given lower limit and either the given upper limit may be arbitrarily combined, as long as the lower limit does not exceed the upper limit. In the following description, when examples of components or methods are listed, unless otherwise specified, only one of the listed examples may be used, or multiple of the listed examples may be used in combination.

[0012] (Positive Electrode for Non-aqueous Electrolyte Secondary Battery) The positive electrode of this embodiment is a positive electrode for a non-aqueous electrolyte secondary battery. Hereinafter, the positive electrode of this embodiment may be referred to as "positive electrode (P)". The positive electrode (P) includes a positive electrode current collector and a positive electrode composite agent layer disposed on the positive electrode current collector. The positive electrode composite agent layer includes a positive electrode active material containing a transition metal element, a binder, a conductive material, and a compound represented by the following formula (1) (hereinafter may be referred to as "compound (1)").

[0013]

[0014] R １ and R ２ are each independently a hydrogen atom or a hydrocarbon group. X contains at least one of a hydrocarbon group and an oxygen atom.

[0015] The positive electrode composite agent layer is formed by applying a positive electrode slurry to the positive electrode current collector and then drying it. In order to improve the productivity of the positive electrode, it is necessary to increase the drying rate of the positive electrode slurry. As one method of increasing the drying rate of the positive electrode slurry, there is a method of reducing the ratio of the liquid medium of the positive electrode slurry. However, when the ratio of the liquid medium is reduced, the viscosity of the slurry becomes too high, making it difficult to apply. By reducing the ratio of the liquid medium and the ratio of the binder, an increase in the viscosity of the slurry can be suppressed. However, in that case, the positive electrode composite agent layer is likely to peel off from the positive electrode current collector. [[ID=!14]]

[0016] The positive electrode composite agent layer of the positive electrode (P) contains compound (1). As a result of investigations, the inventors of the present application have found that by adding compound (1), the adhesion between the positive electrode current collector and the positive electrode composite agent layer can be maintained even when the amount of the binder is small. This disclosure is based on this new finding. [[ID=1!8]]

[0017] The reason why the above effect is obtained by adding compound (1) is not clear at present. However, it is possible that the unshared electron pair of the nitrogen atom contained in the amino group of compound (1) undergoes an acid-base interaction with the transition metal in the positive electrode active material, and the phosphate group, which is a polar group of compound (1), strongly interacts with the binder. Due to these interactions, it is possible that the adhesion between the positive electrode current collector and the positive electrode composite agent layer is maintained even when the amount of the binder is small.

[0018] R １ 及びR ２ は同じであってもよいし、異なってもよい。R １ 及びR ２ は、鎖式炭化水素基及び / または環式炭化水素基を含んでもよい。鎖式炭化水素基の例には、飽和炭化水素基(アルキル基)および、不飽和炭化水素基(ビニル基など)が含まれる。環式炭化水素基の例には、脂環式炭化水素基(シクロアルキル基など)、および、芳香族炭化水素基(フェニル基など)が含まれる。R １ 及びR ２ の炭素数はそれぞれ独立に、0~6の範囲、または0~3の範囲にあってもよく、0、1、または2であってもよい。すなわち、R １ が炭化水素基である場合、その炭素数は、1~6の範囲、または1~3の範囲にあってもよく、1または2であってもよい。R ２ が炭化水素基である場合、その炭素数は、1~6の範囲、または1~3の範囲にあってもよく、1または2であってもよい。

[0019] 化合物(1)の一例では、式(1)のR １ 及びR ２ はそれぞれ独立に、水素原子または鎖式炭化水素基であり、式(1)のXは、鎖式炭化水素基である。化合物(1)のアミノ基は、化合物(1)の末端の炭素原子と結合していてもよい。すなわち、R １ 及びR ２ は水素原子であってもよい。その場合、アミノ基が正極活物質に結合しやすくなる。

[0020] 化合物(1)の一例では、式(1)のXに含まれる酸素数は、0または1であり、化合物(1)に含まれる炭素数(炭素原子数)は、2~8の範囲にある。化合物(1)の一例では、R １ 及びR ２X is a hydrogen atom, and X in formula (1) is an alkylene group having 1 to 4 carbon atoms (for example, 1 to 3 or 1 to 2 carbon atoms). In these examples, X in formula (1) may be replaced with an oxyalkylene group having 1 to 4 carbon atoms (for example, 1 to 3 or 1 to 2 carbon atoms). The oxygen atom of the oxyalkylene group may be bonded to a phosphorus atom. If compound (1) has a large number of carbon atoms, the concentration of functional phosphate and amino groups will be relatively diluted. Therefore, it becomes necessary to increase the amount of compound (1) added, which can lead to problems such as a decrease in battery capacity. By setting the number of carbon atoms of X in compound (1) to the range of 2 to 8, it is possible to suppress the unnecessary increase in the amount of compound (1).

[0021] The molecular weight of compound (1) may be 1000 or less, 500 or less, 300 or less, 200 or less, or 150 or less. By reducing the molecular weight of compound (1), the increase in viscosity of the slurry due to the addition of compound (1) can be suppressed. As a result, the manufacturing of the cathode becomes easier.

[0022] Compound (1) is 2-aminoethylphosphonic acid (H ２ N-CH ２ -CH ２ -P(=O)(OH) ２ ) may also be used. Particularly high effectiveness can be obtained by using 2-aminoethylphosphonic acid.

[0023] (Positive electrode active material) The positive electrode active material is a material capable of intercalating and releasing lithium ions. A composite oxide containing lithium and a transition metal can be used as the positive electrode active material. Examples of transition metals include Ni, Co, and Mn. The composite oxide preferably contains Ni. The composite oxide may have a layered structure (for example, a rock salt crystal structure).

[0024] The composite oxide has the compositional formula Li ｙ Ni ｘ M （１－ｘ） O ２－δIt may be an oxide represented by . x, y, and δ may satisfy 0.8 ≤ x ≤ 1, 0 < y ≤ 1.2, and 0 ≤ δ ≤ 0.05. The element M in the composition formula includes, or may be, at least one element selected from the group consisting of Co, Mn, Al, Fe, Ti, Sr, Ca, Zr, W, and B.

[0025] Element M preferably contains at least one element selected from the group consisting of Co, Mn, Al, and Fe, and may contain only that at least one element. Element M may contain Co and Al, or Co and Al. In the above composition formula, the value of y, which indicates the composition ratio of lithium, increases or decreases with charging and discharging. Examples of composite oxides include lithium-nickel-cobalt-aluminum composite oxide.

[0026] In the above compositional formula, when x is 0.8 or greater, the proportion of nickel among elements other than lithium and oxygen is 80 atomic percent or greater. By setting x to 0.8 or greater, the battery capacity can be increased.

[0027] Composite oxides are typically used in particulate form. The average particle size of the composite oxide may be 1 μm or more, 2 μm or more, or 5 μm or more, and may be 20 μm or less, 15 μm or less, 10 μm or less, 6 μm or less, or 5 μm or less.

[0028] In this specification, unless otherwise specified, the average particle size is the median diameter (D50) at which the cumulative volume in the volume-based particle size distribution reaches 50%. The median diameter is determined using a laser diffraction / scattering particle size distribution analyzer.

[0029] (Binder) The binder is added to improve the adhesion of the positive electrode mixture layer. In terms of interaction with compound (1), the binder is preferably a polar polymer. The binder may be a fluorine-containing polymer. Examples of fluorine-containing polymers include vinylidene fluoride polymers. Examples of vinylidene fluoride polymers include polymers of monomers containing vinylidene fluoride. The binder may include vinylidene fluoride polymers and other fluorine-containing polymers. The vinylidene fluoride polymer may be a copolymer of vinylidene fluoride and other monomers. Examples of vinylidene fluoride polymers include polyvinylidene fluoride (PVDF). The binder may also be a polymer that does not contain fluorine. The binder may be a polymer other than a vinylidene fluoride polymer.

[0030] (Conductive Material) The conductive material is not particularly limited. The conductive material may be a conductive material used in known positive electrodes of known non-aqueous electrolyte secondary batteries. The conductive material may be a conductive carbonaceous material. Examples of conductive carbonaceous materials include conductive carbon particles such as carbon black (e.g., acetylene black, Ketjen black), carbon nanotubes, and other conductive carbonaceous materials.

[0031] The content of compound (1) in the positive electrode mixture layer may be 0.05% by mass or more, or 0.1% by mass or more, and may be 1.0% by mass or less, 0.5% by mass or less, or 0.3% by mass or less. The content of the binder in the positive electrode mixture layer may be 0.5% by mass or more, or 1.0% by mass or more, and may be 3.0% by mass or less, or 2.0% by mass or less. By using compound (1), it is possible to maintain the adhesion of the positive electrode mixture layer even if the binder content is low. When the content of compound (1) and the binder are within these ranges, the binder may be a vinylidene fluoride polymer.

[0032] The content of conductive material in the positive electrode mixture layer may be 0.5% by mass or more, or 1.0% by mass or more, or 3.0% by mass or less, or 2.0% by mass or less. The positive electrode mixture layer may also contain components other than those described above.

[0033] The positive electrode mixture layer is placed on one or both sides of the positive electrode current collector. The thickness of the positive electrode mixture layer is not limited and is selected according to the size and application of the battery. The thickness of the positive electrode mixture layer may be 100 μm or more, or 150 μm or more, or 300 μm or less, or 200 μm or less.

[0034] (Positive electrode current collector) A conductive sheet is used as the positive electrode current collector. The positive electrode current collector may also be a metal foil. Examples of metal foil materials include stainless steel, aluminum, aluminum alloy, and titanium.

[0035] (Method for manufacturing the positive electrode (P)) An example of a method for manufacturing the positive electrode (P) is described below. The positive electrode (P) may also be manufactured by a method other than the one described below.

[0036] First, the positive electrode slurry is prepared. The positive electrode slurry can be prepared by mixing the components of the positive electrode mixture layer with a liquid medium. The mixing ratio of components other than the liquid medium in the positive electrode slurry is reflected in the content of each component in the formed positive electrode mixture layer.

[0037] The order in which the components of the positive electrode mixture layer and the liquid medium are mixed is not particularly limited. The positive electrode slurry may be prepared by mixing a mixture containing all the components of the positive electrode mixture layer with the liquid medium. Alternatively, some of the components of the positive electrode mixture layer may be mixed first, and then the other components may be mixed. Specifically, two or three of the positive electrode active material, binder, conductive material, and compound (1) may be mixed first, and then the other components may be mixed. In this case, the liquid medium may be mixed at any stage. For example, the positive electrode active material and binder may be mixed first, and then the other components may be mixed. Alternatively, the positive electrode active material and compound (1) may be mixed first, and then the other components may be mixed.

[0038] The liquid medium is not particularly limited. The liquid medium may be any known liquid medium used in positive electrode slurries. Organic solvents may be used as the liquid medium. Examples of organic solvents include alcohols (such as ethanol), ethers (such as tetrahydrofuran), amides (such as dimethylformamide), and N-methyl-2-pyrrolidone (NMP).

[0039] Next, a coating film is formed on the positive electrode current collector by applying a positive electrode slurry to the positive electrode current collector. Then, by drying the coating film, a laminate (positive electrode) having a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector is obtained. The obtained laminate may be pressed if necessary. The method of applying and drying the positive electrode slurry is not limited, and known methods may be used.

[0040] (Positive Electrode Slurry) The positive electrode slurry of this embodiment is a positive electrode slurry used in the manufacture of a positive electrode for a non-aqueous electrolyte secondary battery. The positive electrode slurry comprises a positive electrode active material containing a transition metal element, a binder, a conductive material, a liquid medium, and compound (1). Since these have been described above, redundant explanations will be omitted.

[0041] The liquid medium content in the positive electrode slurry may be 5% by mass or more, or 10% by mass or more, or 30% by mass or less, or 20% by mass or less. By lowering the liquid medium content, the drying time required for the positive electrode slurry can be shortened.

[0042] (Non-aqueous electrolyte secondary battery) The non-aqueous electrolyte secondary battery according to this embodiment may be referred to as "non-aqueous electrolyte secondary battery (B)" or "secondary battery (B)" below. The secondary battery (B) includes a positive electrode (P), a negative electrode, and a non-aqueous electrolyte.

[0043] The positive electrode (P) is easy to manufacture and highly reliable because the positive electrode mixture layer is less likely to peel off from the positive electrode current collector. The components other than the positive electrode are not particularly limited, and known components may be used. The secondary battery (B) may be a lithium-ion secondary battery or a lithium secondary battery. When the secondary battery (B) is a lithium secondary battery, lithium metal is deposited in the negative electrode during charging and dissolves during discharge.

[0044] A secondary battery (B) can be manufactured using a positive electrode (P) and other components. The method of manufacturing the secondary battery (B) is not limited, and known manufacturing methods may be used.

[0045] The components other than the positive electrode are not particularly limited, and components used in known non-aqueous electrolyte secondary batteries may be applied. Examples of the components of secondary battery (B) are described below.

[0046] (Positive electrode) The positive electrode described above is used as the positive electrode.

[0047] (Negative electrode) The negative electrode typically includes a negative electrode mixture layer containing a negative electrode active material. The negative electrode may also include a negative electrode current collector and a negative electrode mixture layer disposed on the negative electrode current collector. However, in the case of a lithium secondary battery (lithium metal secondary battery), a negative electrode current collector on which lithium metal can be deposited may be used for the negative electrode.

[0048] The negative electrode mixture layer contains a negative electrode active material as an essential component. The negative electrode mixture layer may also contain optional components such as a binder, thickener, and conductive material. These optional components may be those exemplified as components of the positive electrode.

[0049] The negative electrode mixture layer may be formed by dispersing the components of the negative electrode mixture layer in a liquid medium (dispersion medium), applying the resulting negative electrode slurry to the surface of the negative electrode current collector, and drying it. The dried coating may be rolled if necessary. The liquid medium may be one of the liquid media exemplified for the positive electrode slurry.

[0050] (Negative Electrode Active Material) The negative electrode active material is selected according to the type of secondary battery (B). An example of a negative electrode active material is a material capable of intercalating and releasing lithium ions. Examples of such materials include carbonaceous materials and Si-containing materials. The negative electrode active material may contain Si-containing materials or may be a Si-containing material. Metallic lithium, lithium alloys, etc., may be used as the negative electrode active material. The negative electrode may contain one type of negative electrode active material or a combination of two or more types.

[0051] Examples of carbonaceous materials include graphite, easily graphitizable carbon (soft carbon), and difficult-to-graphitize carbon (hard carbon). Carbonaceous materials may be used individually or in combination of two or more. Graphite is preferred because of its excellent charge-discharge stability and low irreversible capacity. Examples of graphite include natural graphite, artificial graphite, and graphitized mesophase carbon particles.

[0052] Examples of silicon-containing materials include elemental silicon, silicon alloys, silicon compounds (such as silicon oxides), and composite materials in which a silicon phase is dispersed within a lithium-ion conductive phase (matrix). An example of silicon oxide is SiO ｘ Particles are included. x may be, for example, 0.5 ≤ x < 2, and 0.8 ≤ x ≤ 1.6. The lithium ion conducting phase is SiO ２ At least one selected from the group consisting of phase, silicate phase, and carbon phase may be used.

[0053] Metal foil may be used for the negative electrode current collector. The negative electrode current collector may also be porous. Examples of materials for the negative electrode current collector include stainless steel, nickel, nickel alloys, copper, and copper alloys.

[0054] (Non-aqueous electrolytes) Non-aqueous electrolytes consist of a non-aqueous solvent and a solute dissolved in the non-aqueous solvent. Examples of solutes include lithium salts. Various additives may be added to non-aqueous electrolytes.

[0055] As the non-aqueous solvent, known non-aqueous solvents may be used. Examples of non-aqueous solvents include cyclic carbonate esters, linear carbonate esters, cyclic carboxylic acid esters, and linear carboxylic acid esters. Examples of cyclic carbonate esters include propylene carbonate (PC), ethylene carbonate (EC), fluoroethylene carbonate (FEC), and vinylene carbonate (VC). Examples of linear carbonate esters include diethyl carbonate (DEC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC). Examples of cyclic carboxylic acid esters include γ-butyrolactone (GBL) and γ-valerolactone (GVL). Examples of linear carboxylic acid esters include methyl acetate, ethyl acetate, propyl acetate, methyl propionate (MP), and ethyl propionate (EP). These compounds may be used individually or in combination of two or more.

[0056] Examples of lithium salts include lithium salts of chlorine-containing acids (LiClO2). ４ LiAlCl ４ LiB １０ Cl １０ (e.g.), lithium salts of fluorine-containing acids (LiPF) ６ LiPF ２ O ２ LiBF ４ LiSbF ６ LiAsF ６ LiCF ３ SO ３ LiCF ３ CO ２ (etc.), lithium salts of fluorine-containing acidimides (LiN(FSO) ２ ) ２ ,LiN(CF ３ SO ２ ) ２ ,LiN(CF ３ SO ２ ) (C ４ F ９ SO ２ ), LiN(C ２ F ５ SO ２ ) ２These include lithium halides (LiCl, LiBr, LiI, etc.), etc. Lithium salts may be used individually or in combination of two or more types.

[0057] The concentration of lithium salt in the non-aqueous electrolyte may be 1 mol / L or more and 2 mol / L or less, or 1 mol / L or more and 1.5 mol / L or less. By setting the lithium salt concentration within the above range, an electrolyte with excellent ionic conductivity and appropriate viscosity can be obtained.

[0058] Non-aqueous electrolytes may contain known additives. Examples of additives include 1,3-propanesalton, methylbenzenesulfonate, cyclohexylbenzene, biphenyl, diphenyl ether, and fluorobenzene.

[0059] (Separator) The separator is placed between the positive electrode and the negative electrode. The separator preferably has high ion permeability and appropriate mechanical strength and insulating properties. As the separator, a microporous thin film, woven fabric, nonwoven fabric, etc., can be used. Examples of separator materials include polyolefins (polypropylene, polyethylene, etc.) and other resins.

[0060] (Outer casing) The outer casing (battery case) houses the electrode group and the non-aqueous electrolyte. The outer casing is not particularly limited, and known outer casings may be used. The electrode group consists of a positive electrode, a negative electrode, and a separator. The configuration of the electrode group is not particularly limited, and may be a wound type or a stacked type. A wound type electrode group is formed by winding the positive electrode and negative electrode with a separator in between. A stacked type electrode group is formed by stacking the positive electrode and negative electrode with a separator in between. The form of the non-aqueous electrolyte secondary battery is not particularly limited, and may be cylindrical, prismatic, coin-shaped, button-shaped, laminate-shaped, etc.

[0061] Below, an example of a positive electrode (P) and an example of a secondary battery (B) will be described with reference to the drawings. The components of the example described below can be replaced with the components described above. Furthermore, the components of the example described below can be modified based on the above description. In addition, the matters described below may be applied to the above embodiment. Furthermore, in the example described below, components that are not essential for the secondary battery (B) may be omitted.

[0062] An example of a positive electrode (P) is schematically shown in Figure 1. The positive electrode 11 in Figure 1 includes a positive electrode current collector 11a and a positive electrode mixture layer 11b formed on both sides of the positive electrode current collector 11a.

[0063] Figure 2 schematically shows a cross-sectional view of an example of a non-aqueous electrolyte secondary battery (B). The cylindrical non-aqueous electrolyte secondary battery 10 shown in Figure 2 includes a cylindrical battery case and an electrode group 14 and a non-aqueous electrolyte (not shown) housed within the battery case. The electrode group 14 is a wound electrode group and includes a positive electrode 11, a negative electrode 12, and a separator 13.

[0064] The battery case includes a case body 15, which is a bottomed cylindrical metal container, and a sealing body 16 that seals the opening of the case body 15. A gasket 27 is placed between the case body 15 and the sealing body 16. The gasket 27 ensures that the battery case is airtight. Inside the case body 15, insulating plates 17 and 18 are placed at both ends of the electrode group 14. The case body 15 has a stepped portion 21.

[0065] The sealing body 16 includes a filter 22, a lower valve body 23, an insulating member 24, an upper valve body 25, and a cap 26. The lower valve body 23 and the upper valve body 25 are connected at their respective centers. The insulating member 24 is positioned between the periphery of the lower valve body 23 and the periphery of the upper valve body 25. The filter 22 and the lower valve body 23 are connected at their respective peripheries. The upper valve body 25 and the cap 26 are connected at their respective peripheries. All components of the sealing body 16, except for the insulating member 24, are electrically connected. The sealing body 16 functions as a safety valve when the pressure inside the battery case rises.

[0066] The positive electrode 11 is electrically connected to the cap 26, which functions as a positive electrode terminal, via the positive electrode lead 19. The negative electrode 12 is electrically connected to the case body 15, which functions as a negative electrode terminal, via the negative electrode lead 20. The positive electrode 11 is the positive electrode described above.

[0067] (Note) The above description discloses the following technology: (Technology 1) A positive electrode for a non-aqueous electrolyte secondary battery, comprising a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, wherein the positive electrode mixture layer comprises a positive electrode active material containing a transition metal element, a binder, a conductive material, and the following formula (1) (R １ and R ２ Each is independently a hydrogen atom or a hydrocarbon group. X contains at least one of a hydrocarbon group and an oxygen atom. A positive electrode for a non-aqueous electrolyte secondary battery comprising a compound represented by (1). (Technical 2) R of formula (1) １ and R ２ (Technology 3) The positive electrode according to Technology 1, wherein each is independently a hydrogen atom or a chain hydrocarbon group, and X in formula (1) is a chain hydrocarbon group. (Technology 4) The positive electrode according to Technology 1 or 2, wherein the number of oxygen atoms in X in formula (1) is 0 or 1, and the number of carbon atoms in the compound is in the range of 2 to 8. (Technology 5) The positive electrode according to Technology 1, wherein the compound is 2-aminoethylphosphonic acid. (Technology 5) A non-aqueous electrolyte secondary battery comprising the positive electrode according to any one of Technology 1 to 4, a negative electrode, and a non-aqueous electrolyte. (Technology 6) A positive electrode slurry used in the manufacture of a positive electrode for a non-aqueous electrolyte secondary battery, comprising a positive electrode active material containing a transition metal element, a binder, a conductive material, a liquid medium, and a compound represented by formula (1) above.

[0068] The present disclosure will be described in detail below based on examples, but the present disclosure is not limited to the following examples. In this example, several positive electrode slurries were prepared, and a positive electrode was made using the positive electrode slurries.

[0069] (Preparation of positive electrode slurry SA1) First, positive electrode slurry SA1 was prepared by mixing positive electrode active material, polyvinylidene fluoride (PVDF, binder), 2-aminoethylphosphonic acid (compound (1)), acetylene black (conductive material), and N-methyl-2-pyrrolidone (NMP, liquid medium) in a predetermined mass ratio. The positive electrode active material had the composition formula LiNi ０．９１ Co ０．０４ Al ０．０５ O ２ Particles of a composite oxide represented by [formula] were used. The positive electrode active material, PVDF, 2-aminoethylphosphonic acid, and conductive material were mixed in a mass ratio of positive electrode active material:2-aminoethylphosphonic acid:PVDF:conductive material = 97.9:0.1:1.0:1.0. The viscosity of the prepared positive electrode slurry SA1 was measured using a Brookfield viscometer.

[0070] The positive electrode slurry SA1 was applied to one side of the positive electrode current collector (aluminum foil), then dried and rolled. In this way, a positive electrode A1 was fabricated, which included the positive electrode current collector and a positive electrode mixture layer placed on the positive electrode current collector. The peel strength of the positive electrode mixture layer was then measured.

[0071] The peel strength of the positive electrode mixture layer on the positive electrode current collector was measured by a peel test in accordance with JIS (Japanese Industrial Standards) K 6854-1. The sample for measurement was formed by cutting the positive electrode to a size of 1.5 cm x 12 cm. The peel strength was then measured when the gripping and moving speed was 50 mm / min.

[0072] (Preparation of positive electrode slurries SC1 to SC3 and preparation of positive electrodes C1 to C3) Positive electrode slurry SC1 was prepared in the same manner and under the same conditions as the preparation of positive electrode slurry SA1, except that 2-aminoethylphosphonic acid was not added. Positive electrode slurries SC2 and SC3 were prepared in the same manner and under the same conditions as the preparation of positive electrode slurry SA1, except that 3,4,9,10-perylenetetracarboxylic dianhydride or naphthalene-1,4,5,8-tetracarboxylic dianhydride was used instead of 2-aminoethylphosphonic acid. Positive electrodes C1 to C3 were prepared in the same manner as the preparation of positive electrode A1, except that positive electrode slurries SC1 to SC3 were used instead of positive electrode slurry SA1.

[0073] The viscosity of the positive electrode slurries SC1 to SC3 was measured using the method described above. The peel strength of the positive electrode mixture layer in positive electrodes C1 to C3 was measured using the method described above.

[0074] Table 1 shows some of the preparation conditions for the positive electrode slurry and the evaluation results. Note that the percentages in Table 1 represent the percentages of components other than the liquid medium, and are the same as the percentages in the positive electrode mixture layer. Viscosity and peel strength are relative values, with the measured values ​​for positive electrode slurry SC1 and positive electrode C1 set to 100. Higher peel strength is preferable as it makes the positive electrode mixture layer less likely to peel off.

[0075]

[0076] Positive electrode slurry SA1 is the positive electrode slurry according to this disclosure. Positive electrode A1 is the positive electrode (P) according to this disclosure. Positive electrode slurries SC1 to SC3 and positive electrodes C1 to C3 are comparative examples. As shown in Table 1, the viscosity of positive electrode slurry SA1 was low, and the peel strength of the positive electrode mixture layer in positive electrode A1 was high.

[0077] This disclosure is applicable to positive electrodes for non-aqueous electrolyte secondary batteries, non-aqueous electrolyte secondary batteries, and positive electrode slurries for non-aqueous electrolyte secondary batteries. Although the present invention has been described in relation to preferred embodiments at present, such disclosure should not be construed as restrictive. Various modifications and alterations will undoubtedly become apparent to those skilled in the art in the field to which the invention pertains by reading the above disclosure. Accordingly, the appended claims should be construed as encompassing all modifications and alterations without departing from the true spirit and scope of the invention.

[0078] 10: Non-aqueous electrolyte secondary battery 11: Positive electrode 11a: Positive electrode current collector 11b: Positive electrode composite layer 12: Negative electrode

Claims

1. A positive electrode for a non-aqueous electrolyte secondary battery, comprising a positive electrode current collector and a positive electrode mixture layer disposed on the positive electrode current collector, wherein the positive electrode mixture layer comprises a positive electrode active material containing a transition metal element, a binder, a conductive material, and the following formula (1) (R １ and R ２ Each of the elements is independently a hydrogen atom or a hydrocarbon group. X contains at least one of a hydrocarbon group and an oxygen atom. A positive electrode for a non-aqueous electrolyte secondary battery comprising a compound represented by ).

2. R in formula (1) above １ and R ２ The positive electrode according to claim 1, wherein each is independently a hydrogen atom or a chain hydrocarbon group, and X in formula (1) is a chain hydrocarbon group.

3. The positive electrode according to claim 1, wherein the number of oxygen atoms in X of formula (1) is 0 or 1, and the number of carbon atoms in the compound is in the range of 2 to 8.

4. The positive electrode according to claim 1, wherein the compound is 2-aminoethylphosphonic acid.

5. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte according to any one of claims 1 to 4.

6. A positive electrode slurry used in the manufacture of a positive electrode for a non-aqueous electrolyte secondary battery, comprising: a positive electrode active material containing a transition metal element; a binder; a conductive material; a liquid medium; and the following formula (1) (R １ and R ２ A positive electrode slurry containing a compound represented by (where each is independently a hydrogen atom or a hydrocarbon group, and X contains at least one of a hydrocarbon group and an oxygen atom).

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