Positive electrode for lithium battery and lithium battery

Abstract

The positive electrode for a lithium battery contains a conductive auxiliary agent and a positive electrode active material containing manganese dioxide. The conductive auxiliary agent contains carbon black, the carbon black has an average primary particle diameter of 30 nm or more and a specific surface area of 1000 m2 / g or more, and the carbon black contains Al.

Description

Technical Field

[0001] The invention relates to a positive electrode for a lithium battery and a lithium battery. Background Art

[0002] Lithium batteries have high energy density and excellent storage properties, so they are widely used as power sources or backup power sources for various small portable devices.

[0003] In order to improve the conductivity, conductive additives such as carbon black are added to the electrodes of various batteries including such lithium batteries. Among them, Ketjen black is often used as a conductive additive because it exhibits high conductivity and liquid retention even in a small amount.

[0004] For example, Patent Document 1 discloses a lithium primary battery comprising: a positive electrode comprising manganese dioxide as a positive electrode active material, Ketjen black as a conductive aid and a fluororesin as a binder, a negative electrode comprising lithium metal as a negative electrode active material, and a non-aqueous electrolyte (PC / DME).

[0005] Prior art literature

[0006] Patent Literature

[0007] Patent Document 1: Japanese Patent Application Publication No. 2011-060655 Summary of the invention

[0008] Problem that the invention aims to solve

[0009] As mentioned above, manganese dioxide is used as a positive electrode active material, particularly in lithium batteries. Compared with other positive electrode active materials (such as composite oxides containing Li, etc.), manganese dioxide is easy to increase the plate density by pressing. However, in an electrode containing such manganese dioxide, if Ketjen black is used as a conductive additive, the liquid retention of the electrolyte is too high, and there is a problem of excessive expansion of the electrode. If the electrode expands excessively, the adhesion between the electrode mixture layer and the current collector is reduced, and the electrode mixture is easily peeled off from the current collector. Therefore, there is a problem of reduced quality and reliability.

[0010] In contrast, it is believed that if carbon black with a small specific surface area is used, the electrolyte retention is appropriately suppressed, thereby reducing electrode expansion. However, if carbon black with a small specific surface area is used, there is a problem that the discharge capacity of the battery is easily insufficient.

[0011] The present invention has been made based on the above circumstances, and an object of the present invention is to provide a positive electrode for a lithium battery and a lithium battery that can suppress electrode expansion while maintaining discharge capacity.

[0012] Solutions to the problem

[0013] The present invention relates to the following positive electrode for a battery and a battery.

[0014] [1] A positive electrode for a lithium battery, which comprises a conductive additive and a positive electrode active material containing manganese dioxide. The conductive additive comprises carbon black, the primary particle size of the carbon black is 30 nm or more, the specific surface area is 1000 m 2 / g or more, and the carbon black contains Al.

[0015] [2] The positive electrode for a lithium battery according to [1], wherein the mass content of Al in the carbon black is 5 ppm or more relative to the carbon black.

[0016] [3] The positive electrode for a lithium battery according to [1] or [2], wherein the mass content of Al in the carbon black is less than 20 ppm relative to the carbon black.

[0017] [4] The positive electrode for a lithium battery according to any one of [1]-[3], which further comprises a graphite-based active material.

[0018] [5] The positive electrode for a lithium battery according to any one of [1]-[4], wherein the conductive additive further comprises graphite.

[0019] [6] A lithium battery, which comprises: the positive electrode for a lithium battery according to any one of [1]-[5]; a negative electrode containing metallic lithium or a lithium alloy; a separator disposed between the positive electrode for a lithium battery and the negative electrode; and an electrolyte.

[0020] [7] The lithium battery according to [6], wherein the electrolyte comprises a cyclic carbonate solvent and a chain carbonate solvent.

[0021] Advantages of the Invention

[0022] According to the present invention, it is possible to provide a positive electrode for a lithium battery and a lithium battery that can suppress the swelling of the electrode while maintaining the discharge characteristics. Description of the Drawings

[0023] Figure 1A is a schematic perspective view showing the structure of a primary lithium battery according to an embodiment of the present invention, Figure 1B is Figure 1A an exploded perspective view of the primary lithium battery.

[0024] Figure 2 is a graph showing the discharge curves of the batteries of the examples and the comparative examples. Detailed Description of the Embodiments

[0025] As described above, the swelling of the electrode caused by the retention of the electrolyte easily occurs when carbon black with a specific surface area of 1000 m 2 / g or more is used.

[0026] In this regard, the present inventors have found that even if the specific surface area is large, if the carbon black contains Al (aluminum), the expansion of the electrode can be suppressed. That is, the following has been found: carbon black usually contains metal impurities from raw materials or manufacturing methods, and among them, carbon black containing Al can suppress the expansion of the electrode.

[0027] Although the reason is not clear, the following is speculated. Aluminum has an oxide film (such as Al2O3) on its surface. The oxide film shows hydrophilicity, so its affinity with the hydrophobic non-aqueous electrolyte is relatively low. Therefore, it is considered that carbon black containing Al is not likely to hold the electrolyte excessively.

[0028] That is, the positive electrode of the present invention contains manganese dioxide as a positive electrode active material and carbon black containing Al as a conductive aid. Hereinafter, the positive electrode of the present invention and the lithium battery using the positive electrode will be specifically described.

[0029] 1. Lithium battery

[0030] Hereinafter, as an example of the lithium battery of the present embodiment, a primary lithium battery will be described.

[0031] Figure 1A is a schematic perspective view showing the structure of a primary lithium battery according to an embodiment of the present invention, Figure 1B is Figure 1A exploded perspective view of the primary lithium battery.

[0032] As Figure 1A and Figure 1B shown, the primary lithium battery 10 is a so-called thin primary lithium battery, and has a positive electrode 20, a negative electrode 30, a separator 40, an electrolyte (not shown), and an outer package 50. That is, the primary lithium battery 10 is a battery in which an electrode body 60 formed by opposing the positive electrode 20 and the negative electrode 30 with the separator 40 interposed therebetween is encapsulated together with a non-aqueous electrolyte in the outer package 50.

[0033] 1-1. Positive electrode

[0034] The positive electrode 20 contains a positive electrode active material and a conductive aid. In the present embodiment, the positive electrode 20 includes a positive electrode current collector 21 and a positive electrode mixture 22; the positive electrode mixture 22 contains a positive electrode active material and a conductive aid.

[0035] The material constituting the positive electrode current collector 21 can be, for example, stainless steel or aluminum. The shape of the positive electrode current collector 21 can be, for example, a foil shape, a film shape, a net shape, a shape formed by punching or stretching, a porous body, a foam body, etc. Among them, a stainless steel foil is preferred. A positive electrode terminal plate 23 made of stainless steel or the like is connected to the positive electrode current collector 21, and the positive electrode terminal plate 23 is led out to the outside of the outer package 50.

[0036] The positive electrode mixture 22 is supported on the positive electrode current collector 21. The positive electrode active material contained in the positive electrode mixture 22 contains manganese dioxide, and other active materials may be further contained as needed. Examples of other active materials include graphite-based active materials such as fluorinated graphite, metal oxides such as MoO3, V2O5, and Mn2O4, and metal sulfides such as TiS2 and MoS. Among them, graphite-based active materials such as fluorinated graphite are preferred. The graphite-based active material can not only further reduce the decline of the pulse characteristics at the end of discharge, but also improve the pressing property.

[0037] The content of the graphite-based active material in the positive electrode mixture 22 is not particularly limited, but can be set to 0.1%-2.0% relative to the mass percentage of manganese dioxide. If the content ratio of the graphite-based active material becomes higher, it can not only further reduce the decline of the pulse characteristics at the end of discharge, but also improve the pressing property.

[0038] The conductive additive contains carbon black with a specific surface area of 1000 m 2 / g or more and containing Al.

[0039] If the specific surface area of the above carbon black is 1000 m 2 / g or more, the carbon black can form a structure well, so it is easy to sufficiently improve the conductivity of the positive electrode mixture 22 and can maintain the discharge capacity well. The specific surface area of the carbon black is more preferably 1000-2000 m 2 / g. The specific surface area of the carbon black can be measured by the BET method through nitrogen adsorption according to ASTM-D6556.

[0040] The mass content of Al in the above carbon black is not particularly limited, but is preferably 5 ppm or more relative to the carbon black. If the mass content of Al is 5 ppm or more, the liquid retention amount is not likely to increase excessively, and the expansion of the electrode can be further suppressed. The upper limit value of the mass content of Al in the carbon black is not particularly limited, but from the viewpoint of further not easily damaging the conductivity or liquid retention property, it is preferably 500 ppm or less, and more preferably 20 ppm or less.

[0041] The content of Al can be obtained as follows: After pretreating the carbon black by an acid decomposition method according to JIS K 0116; 2014 to prepare a solution, the content of ions / atoms of Al in the solution is measured using an ICP emission analyzer SPS3500 manufactured by SSI NanoTechnology Co., Ltd.

[0042] It should be noted that even when the positive electrode mixture 22 further contains graphite described below, materials with an ordered crystal structure observed by TEM observation or the like can be identified as graphite, and materials without an ordered crystal structure can be identified as carbon black. Further, by separating and recovering the carbon black containing Al from the positive electrode mixture 22 and performing the above ICP measurement on the carbon black, the content of Al in the carbon black can be confirmed.

[0043] In addition, the total amount of metal impurities containing Al is not particularly limited. For example, its mass content can be 3000 ppm or less. The total amount of metal impurities can be measured by the same method as above.

[0044] The DBP oil absorption of the above carbon black is not particularly limited, but is preferably 250 - 800 mL / 100 g. If the DBP oil absorption is within the above range, it is easy to appropriately ensure the liquid retention property of the electrolyte. The DBP oil absorption can be measured according to ASTM D - 2414 (JISK 6217 - 4). The DBP oil absorption can be adjusted, for example, by the average primary particle size or pore volume, pore diameter, content of Al, etc.

[0045] The average primary particle size of the above carbon black is not particularly limited. For example, it is 30 nm or more, and can also be 30 - 100 nm. If the average primary particle size of the carbon black is 30 nm or more, the amount of expansion of the electrode during liquid retention is likely to be large. Even in this case, by using the carbon black containing Al, the expansion of the electrode can be reduced to a certain level or below. The average primary particle size of the carbon black can be obtained by measuring the particle sizes of any 100 particles by electron microscopy and taking their average value.

[0046] The type of the above carbon black only needs to be a carbon black whose specific surface area at least satisfies the above range and contains Al. For example, it can be furnace black.

[0047] The content of the above carbon black is not particularly limited, but the mass percentage relative to the positive electrode active material is preferably 1% - 10%. If the mass percentage of the above carbon black is 1% or more, it is easy to further improve the conductivity of the positive electrode mixture 22. If the mass percentage of the above carbon black is 10% or less, the content ratio of the positive electrode active material can be increased, so the discharge capacity can be further improved.

[0048] Within the range that does not damage the effects of the present invention, the conductive assistant can further contain conductive assistants other than the above. Examples of such conductive assistants include graphite. Graphite can not only further improve the conductivity of the positive electrode mixture 22, but also further improve the pressability. That is, the positive electrode mixture 22 further containing graphite is more likely to increase the plate density, while on the other hand, the expansion of the electrode is more likely to occur. Even in this case, by using the above carbon black, the expansion of the electrode can be suppressed. It should be noted that the above carbon black and graphite can be identified by TEM observation.

[0049] It should be noted that graphite is a substance different from the graphite-based active material used as the positive electrode active material. For example, the average primary particle size of graphite is smaller than that of the graphite-based active material, and it can generally be 1-20 μm. The content of graphite can be 1%-10% by mass relative to the positive electrode active material.

[0050] The positive electrode mixture 22 may further contain a binder as needed. Examples of the binder include fluorine resins such as polytetrafluoroethylene (PTFE) and polyvinylidene fluoride (PVdF), and styrene-butadiene rubber (SBR).

[0051] The thickness of the positive electrode 20 when coating the positive electrode mixture 22 on both sides of the positive electrode current collector 21 also depends on the desired capacity, but for example, it can be 100-800 μm. If the thickness of the positive electrode 20 is 100 μm or more, it is easier to further increase the discharge capacity. If it is 800 μm or less, the diffusion distance of Li ions in the positive electrode mixture 22 can be further shortened, so it is easier to further suppress the internal resistance value of the battery.

[0052] 1-2. Negative electrode

[0053] The negative electrode 30 contains metallic lithium or a lithium alloy as the negative electrode active material. In this embodiment, the negative electrode 30 includes a negative electrode current collector 31 and metallic lithium or a lithium alloy as the negative electrode active material 32.

[0054] The material constituting the negative electrode current collector 31 can be, for example, copper, nickel, stainless steel, etc. The shape of the negative electrode current collector 31 can be the same as above. Among them, a copper foil is preferred. A negative electrode terminal plate 33 made of stainless steel or the like is connected to the negative electrode current collector 31, and the negative electrode terminal plate 33 is led out to the outside of the outer package 50. It should be noted that the negative electrode current collector 31 can also be omitted. In this case, the negative electrode terminal plate 33 is directly connected to the negative electrode active material 32.

[0055] The negative electrode active material 32 can be plate-shaped metallic lithium or a lithium alloy. Examples of the lithium alloy include Li-Al (lithium-aluminum alloy), Li-Sn, Li-Pb, Li-Ni-Si, etc., and Li-Al is preferred.

[0056] 1-3. Separator

[0057] The separator 40 is disposed between the positive electrode 20 and the negative electrode 30 to electrically insulate them. The separator 40 can be a microporous resin film or non-woven fabric of an olefin-based resin such as polyethylene or polypropylene.

[0058] 1-4. Electrolyte

[0059] The electrolyte is filled in the internal space of the exterior body 50. Thus, the positive electrode 20, the negative electrode 30, and the separator 40 are immersed in the electrolyte. In the present embodiment, the electrolyte is a non-aqueous electrolyte (organic electrolyte). The non-aqueous electrolyte contains a non-aqueous solvent and an electrolyte.

[0060] There is no particular limitation on the type of the non-aqueous solvent, and cyclic carbonates such as propylene carbonate (PC) and ethylene carbonate (EC), chain carbonates such as dimethyl carbonate (DMC) and diethyl carbonate (DEC), ethers such as 1,2-dimethoxyethane (DME), and lactones such as γ-butyrolactone can be used. One of them can be used, or two or more of them can be combined. For example, from the viewpoint of further balancing the dielectric constant and the viscosity, a cyclic carbonate and a chain carbonate can also be used in combination.

[0061] The electrolyte is a lithium salt, and examples thereof include lithium hexafluorophosphate (LiPF6), lithium perchlorate (LiClO4), lithium trifluoromethanesulfonate (LiCF3SO3), LiN(CF3SO2)2, LiN(C2F5SO2)2, LiN(CF3SO2)(C4F9SO2), etc.

[0062] There is no particular limitation on the concentration of the electrolyte in the electrolyte. For example, its molar percentage can be 0.1% - 5%, preferably 0.25% - 3.5%. The concentration of the electrolyte refers to the total concentration of the dissociated electrolyte and the undissociated electrolyte.

[0063] 1 - 5. Exterior body

[0064] The exterior body 50 is a casing that encapsulates the positive electrode 20, the negative electrode 30, the separator 40, and the electrolyte (not shown). In the present embodiment, the exterior body 50 is made of a flexible aluminum laminated film. That is, the exterior body 50 is a bag-shaped object formed by welding the peripheral region of the film 50a and the peripheral region of the film 50b to each other.

[0065] 2. Manufacturing method of lithium battery

[0066] The above-mentioned primary lithium battery can be manufactured by any method. For example, the above-mentioned primary lithium battery can be manufactured through the following processes: 1) a process of preparing electrodes (positive electrode and negative electrode); and 2) a process of obtaining a primary lithium battery using the prepared electrodes.

[0067] Regarding the process of 1)

[0068] In the present embodiment, the positive electrode 20 can be obtained, for example, by mixing and kneading the above-mentioned positive electrode active material, the above-mentioned conductive assistant, the above-mentioned binder, and water or a solvent to obtain a positive electrode mixture paste, then coating the positive electrode mixture paste on the positive electrode current collector 21 and drying it, and pressing it as needed. By performing pressing, the packing density of the active material in the positive electrode mixture 22 can be increased.

[0069] In the present embodiment, the negative electrode 30 can be obtained, for example, by pressing the negative electrode active material 32 onto the negative electrode current collector 31. Alternatively, in the same manner as described above, after obtaining a negative electrode mixture paste by mixing the negative electrode active material 32, a conductive additive, a binder, and an appropriate amount of water or solvent, the paste is coated on the surface of the negative electrode current collector 31 and dried, and then pressed as needed to obtain the negative electrode 30.

[0070] Furthermore, one end of the positive electrode terminal plate 23 is welded to the positive electrode current collector 21, and one end of the negative electrode terminal plate 33 is welded to the negative electrode current collector 31. When the negative electrode 30 does not have the negative electrode current collector 31, one end of the negative electrode terminal plate 33 can be directly welded to the negative electrode active material 32.

[0071] Regarding the process of 2)

[0072] Next, the positive electrode 20, the negative electrode 30, and the separator 40 are stacked in such a manner that the separator 40 is sandwiched between the negative electrode mixture active material 32 of the negative electrode 30 and the positive electrode mixture 22 of the positive electrode 20 to form an electrode assembly 60.

[0073] The electrode assembly 60 is placed inside a bag-shaped outer package 50. For example, three sides of a rectangle of two opposing aluminum laminated films 50a and 50b are welded to each other, leaving one side open to form a bag shape. The electrode assembly 60 is accommodated inside the bag-shaped aluminum laminated films 50a and 50b, and the positive electrode terminal plate 23 and the negative electrode terminal plate 33 are led out to the outside of the outer package 50 through the opening of the bag-shaped aluminum laminated films 50a and 50b.

[0074] Next, an electrolyte is injected into the outer package 50 containing the electrode assembly 60, and the electrode assembly 60 is impregnated with the electrolyte under reduced pressure.

[0075] Then, the periphery of one side of the opening of the outer package 50 is welded to seal the opening of the outer package 50. Thus, the primary lithium battery 10 can be obtained.

[0076] 3. Modification

[0077] It should be noted that, in the above embodiment, an example of a thin (laminated type) battery is shown, but it is not limited thereto, and it can be any one of a coin type, a cylindrical type, a square type, and a laminated type. In addition, depending on the shape of the battery, the current collector can also serve as the outer package or the terminal, so it can be omitted. For example, in a coin-shaped battery, the outer package case or the sealing plate can also serve as the current collector or the terminal, so a new current collector or terminal does not need to be provided.

[0078] In addition, in the above embodiment, the lithium battery is a primary battery, but it is not limited thereto, and it can also be a secondary battery.

[0079] As described above, the carbon black can be used as a conductive aid added to the electrodes of various batteries.

[0080] Examples

[0081] Hereinafter, the present invention will be described with reference to examples. The interpretation of the scope of the present invention is not limited by the examples.

[0082] 1. Types of conductive aids

[0083] Conductive aid 1: XE2-B (manufactured by Orion Engineered Carbons, furnace black)

[0084] Conductive aid 2: XPB538 (manufactured by Orion Engineered Carbons, furnace black)

[0085] Conductive aid 3: EC600JD (manufactured by LION SPECIALTY CHEMICALS, Ketjen black)

[0086] Conductive aid 4: 420B (manufactured by Orion Engineered Carbons, acetylene black)

[0087] Conductive aid 5: Li-400 (manufactured by Denka, acetylene black)

[0088] The physical properties of each conductive aid are shown in Table 1, and the metal impurity content is shown in Table 2.

[0089] Table 1

[0090]

[0091] Table 2

[0092]

[0093] Each physical property is measured by the following method.

[0094] (Average primary particle size)

[0095] The particle sizes of any 100 particles are measured by an electron microscope, and their average value is obtained.

[0096] (DBP oil absorption)

[0097] Measured according to ASTM D-2414 (JIS K 6217-4).

[0098] (pH)

[0099] The pH is measured by dispersing a known amount of carbon black in water according to ASTM D1512 and measuring the pH of the aqueous phase using a pH probe.

[0100] (Specific surface area)

[0101] The specific surface area is measured by nitrogen adsorption according to ASTM-D6556 using the BET method.

[0102] (Amount of metallic impurities)

[0103] According to JIS K 0116; 2014, the carbon black is pretreated by an acid decomposition method to prepare a solution. The content of Al ions / atoms in the obtained solution is measured using an ICP emission analyzer SPS3500 manufactured by SSI NanoTechnology Inc. to obtain the amount of metallic impurities.

[0104] 2. Preparation and evaluation of lithium batteries

[0105] <Example 1>

[0106] (Preparation of positive electrode)

[0107] Electrolytic manganese dioxide as a positive electrode active material with a mass percentage of 88.9% in the total solid content, graphite fluoride as a graphite-based active material with a mass percentage of 1.8% in the total solid content, conductive additive 1 (XE2-B, manufactured by Orion Engineered Carbons) as a conductive additive with a mass percentage of 3.8% in the total solid content, graphite (average primary particle size 15 μm) with a mass percentage of 1.0% in the total solid content, polytetrafluoroethylene (PTFE) as a binder with a mass percentage of 4.5% in the total solid content, and an appropriate amount of water are added and kneaded to prepare a paste-like positive electrode mixture. The positive electrode mixture is coated on both sides of a steel wire mesh made of stainless steel (SUS) as a current collector so that the size of the coating part becomes 20 cm × 30 cm, and then dried and pressed to prepare a positive electrode with an overall thickness of about 150 μm. The density of the pressed mixture is 3.1 g / cm 3 .

[0108] (Preparation of negative electrode)

[0109] A sheet of metallic lithium is cut into a size of 25 cm × 35 cm as the negative electrode.

[0110] (Preparation of electrolyte)

[0111] Dissolve LiCF3SO3 as a lithium salt in propylene carbonate (PC) / ethylene carbonate (EC) / dimethoxyethane (DME) = 10.5 / 10.5 / 79.0 (volume ratio) to a molar percentage of 0.63% to prepare an electrolyte solution.

[0112] (Preparation of battery)

[0113] Stack the above-prepared positive electrode and negative electrode with a separator interposed therebetween as an electrode body. Place this electrode body into a laminated outer package, inject the above-prepared electrolyte solution, and impregnate it under reduced pressure. Then, heat-seal the opening of the laminated outer package to prepare a laminated battery.

[0114] <Examples 2, Comparative Examples 1 - 3>

[0115] Except for changing the type of conductive additive contained in the positive electrode mixture as shown in Table 2, prepare the positive electrode in the same manner as in Example 1 and prepare a laminated battery.

[0116] <Evaluation>

[0117] The swelling of the electrodes and the discharge characteristics of the batteries in Examples 1 - 2 and Comparative Examples 1 - 3 were evaluated by the following methods.

[0118] (Swelling of electrodes)

[0119] 1) First, measure the surface height of the positive electrode before dropping the electrolyte solution using a laser microscope (manufactured by Keyence Corporation, VK-X3000).

[0120] 2) Next, drop 1 μL of the electrolyte solution onto the surface of the positive electrode and dry it at room temperature until the electrolyte solution is absorbed. Then, dry it in a thermostat at 80°C for 12 hours and measure the surface height of the positive electrode at the dropping part in the same manner as above.

[0121] 3) Further, subtract the surface height of the positive electrode before dropping in 1) from the surface height of the positive electrode after dropping in 2) (about 12 μm) to calculate the swelling amount (μm) of the electrode. Note that the "surface height" of the positive electrode refers to the maximum height in the surface roughness of the positive electrode mixture.

[0122] (Discharge characteristics)

[0123] Perform a discharge test on the prepared battery under the following conditions.

[0124] The discharge is carried out in the CC (constant current) discharge mode. The current rate is set to 1 / 20C and the discharge is terminated at 2.0V. The discharge test is carried out at 23°C.

[0125] The evaluation results are shown in Table 3. In addition, the discharge curves of the batteries of the examples and comparative examples are as Figure 2 shown.

[0126] Table 3

[0127]

[0128] (1) Regarding the discharge characteristics

[0129] As shown in Table 3, it can be seen that in the batteries of Comparative Example 2 and Comparative Example 3 using a conductive additive with a specific surface area of less than 1000 m 2 / g, the discharge capacity is low.

[0130] In contrast, it can be seen that the batteries of Example 1, Example 2 and Comparative Example 1 using a conductive additive with a specific surface area of 1000 m 2 / g or more showed a high discharge capacity (refer to Figure 2 ).

[0131] From this, it can be known that in order to obtain a discharge capacity of a certain level or more, it is effective to set the specific surface area of the conductive additive to 1000 m 2 / g or more.

[0132] (2) Regarding the swelling of the electrode

[0133] On the other hand, it can be seen that in Comparative Example 2 and Comparative Example 3 using conductive additives 4 and 5 with a specific surface area of less than 1000 m 2 / g, the swelling of the electrode hardly occurs, but in Comparative Example 1 using conductive additive 3 with a specific surface area of 1000 m 2 / g or more, the swelling of the electrode occurs significantly.

[0134] In contrast, it can be seen that even when the specific surface area is 1000 m 2 / g or more, in Example 1 and Example 2 containing Al, the swelling of the electrode is significantly suppressed. Specifically, compared with Comparative Example 1 using conductive additive 3, in Example 1 using conductive additive 1, it is suppressed to about 1 / 40, and in Example 2 using conductive additive 2, it is suppressed to about 1 / 200.

[0135] From this, it can be known that when using a conductive additive with a specific surface area of 1000 m 2 / g or more, the swelling of the electrode will occur; the swelling of the electrode can be suppressed by using a conductive additive containing aluminum (Al). It is known that Al is generally oxidized to form a film, and it is considered that as long as it contains Al, even if only a small amount, the effect can be expected.

[0136] According to the present invention, it is possible to provide a positive electrode for a lithium battery and a lithium battery that can suppress the expansion of the electrode while maintaining the discharge characteristics.

[0137] Industrial applicability

[0138] According to the present invention, it is possible to provide a positive electrode for a lithium battery that can suppress the expansion of the electrode while maintaining the discharge characteristics. The positive electrode for the lithium battery can be suitably used as the positive electrode of a lithium battery.

[0139] Explanation of reference numerals

[0140] 10: Primary lithium battery;

[0141] 20: Positive electrode;

[0142] 21: Positive electrode current collector;

[0143] 22: Positive electrode mixture;

[0144] 23: Positive electrode terminal plate;

[0145] 30: Negative electrode;

[0146] 31: Negative electrode current collector;

[0147] 32: Negative electrode active material;

[0148] 33: Negative electrode terminal plate;

[0149] 40: Separator;

[0150] 50: Outer package;

[0151] 60: Electrode body.

Claims

1. A positive electrode for a lithium battery, which comprises a conductive additive and a positive electrode active material containing manganese dioxide. The conductive additive contains carbon black, the average primary particle size of the carbon black is 30 nm or more, the specific surface area is 1000 m 2 / g or more, and the carbon black contains Al.

2. The positive electrode for a lithium battery according to claim 1, wherein the mass content of Al in the carbon black is 5 ppm or more relative to the carbon black.

3. The positive electrode for a lithium battery according to claim 2, wherein the mass content of Al in the carbon black is less than 20 ppm relative to the carbon black.

4. The positive electrode for a lithium battery according to claim 1, wherein the positive electrode active material further comprises a graphite-based active material.

5. The positive electrode for a lithium battery according to claim 1, wherein the conductive additive further comprises graphite.

6. A lithium battery, which comprises: the positive electrode for a lithium battery according to any one of claims 1-5; a negative electrode containing metallic lithium or a lithium alloy; a separator disposed between the positive electrode for a lithium battery and the negative electrode; and an electrolyte.

7. The lithium battery according to claim 6, wherein the electrolyte comprises a cyclic carbonate solvent and a chain carbonate solvent.

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