Positive electrode for lithium secondary battery and lithium secondary battery including the same

Abstract

The present invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery including the same. The positive electrode is manufactured by using a pre-dispersion liquid containing a positive electrode additive represented by Chemical Formula 1 and a linear conductive material in a positive electrode mixture layer as an irreversible additive. The electrode sheet resistance is adjusted to satisfy a specific range, thereby reducing the amount of oxygen gas generated during charge and discharge, and easily improving the charge and discharge efficiency of the lithium secondary battery.

Description

Technical Field

[0001] The present invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery including the same. This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0072238 filed on June 3, 2021 and Korean Patent Application No. 10-2022-0041454 filed on April 4, 2022, and all contents disclosed in the documents of the Korean patent applications are included as part of this specification.

Background Art

[0002] Recently, the demand for secondary batteries as an energy source has been rapidly increasing. Among such secondary batteries, lithium secondary batteries having a high energy density, a high voltage, a long cycle life, and a low self-discharge rate have been commercialized and widely used.

[0003] As a negative electrode material for lithium secondary batteries, graphite is mainly used. However, since graphite has a low capacity of 372 mAh / g per unit mass, it is difficult to increase the capacity of lithium secondary batteries. Accordingly, in order to increase the capacity of lithium secondary batteries, negative electrode materials that form intermetallic compounds with lithium, such as silicon, tin, and their oxides, have been developed and used as non-carbon negative electrode materials having a higher energy density than graphite. However, in the case of such non-carbon negative electrode materials, although the capacity is large, there is a problem in that the initial efficiency is low, so the lithium consumption amount during the initial charge and discharge is large and the irreversible capacity loss is large.

[0004] In connection with this, a method has been proposed to overcome the irreversible capacity loss of the negative electrode by using a material that is electrochemically active after the first cycle so as to provide a lithium ion supply source or storage site to the positive electrode material and not degrade the performance of the entire battery. Specifically, as a sacrificial positive electrode material or an irreversible additive (or over-discharge prevention agent), for example, a method of applying an oxide containing an excessive amount of lithium such as Li 6 CoO 4 to the positive electrode is known.

[0005] On the one hand, conventional irreversible additives such as the above-mentioned Li 6 CoO 4 are generally produced by reacting cobalt oxide or the like with an excessive amount of lithium oxide. The irreversible additive produced in this way is structurally unstable, and as charging progresses, a large amount of oxygen gas (O 2 ) is generated as follows. However, if the irreversible additive remains unreacted during the initial charging of the secondary battery, that is, during battery activation, a reaction occurs during the subsequent charge-discharge process, generating side reactions and a large amount of oxygen gas inside the battery. The oxygen gas generated in this way can induce volume expansion of the electrode assembly and act as one of the main factors leading to a decrease in battery performance.

[0006]

Chemical formula

[0007] In addition, conventionally, the commonly used irreversible additive exhibits a very low powder electrical conductivity of approximately ~10 -11 S / cm, which is nearly a non-conductor due to a 2D percolating network. Such a low powder electrical conductivity increases the electrical resistance of the positive electrode. In this case, at a low C-rate, a large capacity of 200 mAh / g or more is exhibited, but as the C-rate increases, the performance rapidly decreases as charge-discharge progresses due to the large resistance, resulting in a decrease in the charge-discharge capacity of the battery and a limitation in achieving high-speed charge-discharge.

[0008] Therefore, there is a demand for the development of a lithium secondary battery that is excellent in electrical performance and has improved battery safety.

Prior art documents

Patent documents

[0009]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0010] Accordingly, an object of the present invention is to provide a positive electrode for a lithium secondary battery that effectively improves the electrical properties of the lithium secondary battery and has improved safety, and a lithium secondary battery including the same.

Means for Solving the Problems

[0011] In order to solve the above problems, in one embodiment, the present invention includes a positive electrode current collector, and a positive electrode composite layer located on the positive electrode current collector and including a positive electrode active material, a positive electrode additive represented by the following Chemical Formula 1, a first conductive material, and a binder, wherein the first conductive material contains one or more of carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers, and provides a positive electrode for a lithium secondary battery having a surface resistance of 3.0 Ω / sq. or less:

[0012] [Chemical Formula 1] Li p Co (1-q) M 1 q O 4

[0013] In Chemical Formula 1 above, M 1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and p and q are 5 ≤ p ≤ 7 and 0 ≤ q ≤ 0.5, respectively.

[0014] At this time, the positive electrode composite material layer may further contain a second conductive material, and the second conductive material may contain one or more of natural graphite, artificial graphite, carbon black, acetylene black, Denka black, Ketjen black, Super P, channel black, furnace black, lamp black, and thermal black.

[0015] Further, the electrode surface resistance R12 of the positive electrode containing the first conductive material and the second conductive material in the positive electrode composite material layer may have a ratio R12 / R1 of 0.5 to 1.2 with respect to the electrode surface resistance R1 of the positive electrode containing the first conductive material alone in the positive electrode composite material layer, or may have a ratio R12 / R2 of 0.1 to 0.8 with respect to the electrode surface resistance R2 of the positive electrode containing the second conductive material alone in the positive electrode composite material layer.

[0016] Specifically, the electrode surface resistance R12 of the positive electrode containing the first conductive material and the second conductive material in the positive electrode composite material layer may have a ratio R12 / R1 of 0.7 to 1.0 with respect to the electrode surface resistance R1 of the positive electrode containing the first conductive material alone in the positive electrode composite material layer, or may have a ratio R12 / R2 of 0.2 to 0.6 with respect to the electrode surface resistance R2 of the positive electrode containing the second conductive material alone in the positive electrode composite material layer.

[0017] Also, the positive electrode additive may have a tetragonal structure with a space group of P4 2 / nmc.

[0018] Also, the content of the positive electrode additive may be 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode composite material layer.

[0019] At the same time, the content of the first conductive material may be 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode composite material layer.

[0020] Also, when both the first conductive material and the second conductive material are included, the total content of the first conductive material and the second conductive material may be 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode composite material layer. In this case, the second conductive material may be contained in an amount of 20 to 60 parts by weight with respect to 100 parts by weight of the first conductive material.

[0021] On the other hand, the positive electrode active material may be a lithium metal composite oxide represented by the following Chemical Formula 2:

[0022] [Chemical Formula 2] Li x [Ni y Co z Mn w M 2 v O u

[0023] In the above Chemical Formula 2, M 2 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, x, y, z, w, v, and u are respectively 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, 0.01 < z ≤ 0.5, 0.01 < w ≤ 0.5, 0 ≤ v ≤ 0.2, and 1.5 ≤ u ≤ 4.5.

[0024] Further, in one embodiment of the present invention, a positive electrode additive represented by the following Chemical Formula 1; a step of mixing a first conductive material and a binder to produce a pre-dispersion liquid, a step of mixing the produced pre-dispersion liquid, a positive electrode active material, and a binder to produce a positive electrode slurry, a step of applying the positive electrode slurry onto a positive electrode current collector to produce a positive electrode composite layer, and includes the first conductive material contains one or more of carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers, A method for manufacturing a positive electrode for a lithium secondary battery is provided, wherein the surface resistance of the produced positive electrode is 3.0 Ω / sq. or less:

[0025] [Chemical Formula 1] Li p Co (1-q) M 1 q O4

[0026] In the above Chemical Formula 1, M 1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, p and q are 5 ≦ p ≦ 7 and 0 ≦ q ≦ 0.5, respectively.

[0027] At this time, the step of manufacturing the above pre-dispersion can be performed under the condition of a relative humidity of 10% or less.

[0028] Further, in the step of manufacturing the above positive electrode slurry, a second conductive material can be additionally mixed.

[0029] Moreover, in one embodiment, the present invention provides a lithium secondary battery including the positive electrode according to the present invention described above, a negative electrode, and a separator located between the positive electrode and the negative electrode.

Advantages of the Invention

[0030] The positive electrode for a lithium secondary battery according to the present invention is manufactured using a pre-dispersion containing a positive electrode additive represented by Chemical Formula 1, which is an irreversible additive, and a conductive material having a linear structure in a positive electrode composite layer, and by adjusting so that the above electrode surface resistance satisfies a specific range, it is possible to reduce the amount of oxygen gas generated during charge and discharge, and there is an advantage that the charge and discharge efficiency of the lithium secondary battery can be easily improved.

Brief Description of the Drawings

[0031]

Figure 1

Modes for Carrying Out the Invention

[0032] While the present invention is capable of various modifications and having various embodiments, specific embodiments will be described in detail in the detailed description.

[0033] However, this is not intended to limit the present invention to specific embodiments, and it should be understood to include all modifications, equivalents, or alternatives included in the spirit and technical scope of the present invention.

[0034] In the present invention, terms such as "comprising" or "having" are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, and should not be construed as precluding the presence or addition of one or more other features, numbers, steps, operations, components, parts, or combinations thereof in advance.

[0035] Also, in the present invention, when a part such as a layer, film, region, plate, etc. is described as "on" another part, this includes not only the case where it is "directly on" the other part, but also the case where there are further other parts in between. Conversely, when a part such as a layer, film, region, plate, etc. is described as "under" another part, this includes not only the case where it is "directly under" the other part, but also the case where there are further other parts in between. Also, in this application, being "disposed on" can include not only the upper part but also the case of being disposed in the lower part.

[0036] Also, in the present invention, the "main component" means 50% by weight or more, 60% by weight or more, 70% by weight or more, 80% by weight or more, 90% by weight or more, 95% by weight or more, or 97.5% by weight or more with respect to the total weight of the composition or a specific component. In some cases, when constituting the entire composition or specific component, that is, it can also mean 100% by weight.

[0037] In the present invention, "Ah" is a unit of the capacity of a lithium secondary battery, called "ampere-hour", which means the current amount per unit time. For example, if the battery capacity is "3000 mAh", it means that it can be discharged with a current of 3000 mA for 1 hour.

[0038] Hereinafter, the present invention will be described in more detail.

[0039] <Positive electrode for lithium secondary battery> In one embodiment, the present invention comprises a positive electrode current collector, and a positive electrode composite layer which is located on the positive electrode current collector and contains a positive electrode active material, a positive electrode additive represented by the following Chemical Formula 1, a first conductive material, and a binder. The first conductive material contains one or more of graphene, carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers, and provides a positive electrode for a lithium secondary battery having a surface resistance of 3.0 Ω / sq. or less.

[0040] [Chemical Formula 1] Li p Co (1-q) M 1 q O 4

[0041] In Chemical Formula 1 above, M 1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and p and q are 5 ≤ p ≤ 7 and 0 ≤ q ≤ 0.5, respectively.

[0042] The positive electrode for a lithium secondary battery according to the present invention includes a positive electrode composite layer manufactured by applying, drying, and pressing a positive electrode slurry on a positive electrode current collector, and the positive electrode composite layer has a configuration containing a positive electrode active material, a positive electrode additive, a conductive material, and a binder.

[0043] At this time, the positive electrode additive may be lithium cobalt oxide represented by the following Chemical Formula 1:

[0044] [Chemical Formula 1] Li p Co (1-q) M 1 q O 4

[0045] In the above Chemical Formula 1, M 1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, p and q are respectively 5 ≤ p ≤ 7 and 0 ≤ q ≤ 0.5.

[0046] The positive electrode additive contains an excessive amount of lithium and can provide lithium for lithium consumption generated by an irreversible chemical and physical reaction at the negative electrode during initial charging. As a result, the charging capacity of the battery can be increased, the irreversible capacity can be decreased, and the life characteristics can be improved.

[0047] Among them, since the positive electrode additive represented by the above Chemical Formula 1 has a high lithium ion content compared with nickel-containing oxides commonly used in the art, it can replenish lithium ions lost in an irreversible reaction during initial activation of the battery, so that the charge and discharge capacity of the battery can be significantly improved. In addition, compared with iron and / or manganese-containing oxides commonly used in the art, there is no side reaction caused by the elution of transition metals during charge and discharge of the battery, so it has the advantage of excellent battery stability. Such lithium metal oxides represented by Chemical Formula 1 include Li 6 CoO 4 , Li 6 Co 0.5 Zn 0.5 O 4 , Li 6 Co 0.7 Zn 0.3 O 4 etc. may be included.

[0048] Further, the cathode additive represented by the above chemical formula 1 may have a tetragonal crystal structure. Among these, P4 having a distorted tetrahedral structure formed by cobalt element and oxygen element 2 / nmc may be included in the space group. The above cathode additive has a distorted tetrahedral structure formed by cobalt element and oxygen atoms, and is structurally unstable. Therefore, when it is used at 5 parts by weight or less with respect to 100 parts by weight of the cathode composite material layer during the production of the cathode, side reactions with moisture and oxygen in the air can occur during the mixing process of the cathode slurry. However, the present invention has the advantage that by using a composition in which the cathode additive is pre-dispersed during the production of the cathode slurry, it is possible to prevent the cathode additive from undergoing side reactions with moisture and oxygen in the air.

[0049] Further, the above cathode additive may be contained in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the cathode composite material layer. Specifically, it may be contained in an amount of 0.1 to 8 parts by weight; 0.1 to 5 parts by weight; 1 to 10 parts by weight; 2 to 10 parts by weight; 5 to 10 parts by weight; 2 to 8 parts by weight; 3 to 7 parts by weight; or 4 to 5.5 parts by weight with respect to 100 parts by weight of the cathode composite material layer. The present invention can prevent the discharge capacity from decreasing without sufficiently replenishing lithium ions lost by an irreversible reaction due to a low content of the cathode additive by adjusting the content of the cathode additive within the above range, and can prevent a large amount of oxygen gas from being generated during charge and discharge of the battery due to an excessive cathode additive.

[0050] Further, the cathode for the lithium secondary battery may contain a first conductive material in the cathode composite material layer. The first conductive material may contain one or more of graphene having a linear structure, carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers.

[0051] At this time, the average size of the first conductive material may be 500 nm or less. Specifically, it may be 10 - 500 nm; 10 - 400 nm; 10 - 300 nm; 10 - 200 nm; 10 - 100 nm; 50 - 500 nm; 100 - 500 nm; 200 - 500 nm; 250 - 500 nm; 300 - 500 nm; 400 - 500 nm; 100 - 300 nm; 200 - 400 nm; or 50 - 250 nm. Here, the average size means the average length of the first conductive material.

[0052] By controlling the average size of the first conductive material having a linear structure within the above range, the present invention can form a conductive path on the surface of the positive electrode additive with low powder electrical conductivity, and through this, the resistance of the positive electrode can be further reduced.

[0053] In addition, the positive electrode composite layer may further contain a second conductive material containing one or more of natural graphite, artificial graphite, carbon black, acetylene black, Denka black, Ketjen black, Super P, channel black, furnace black, lamp black, and thermal black together with the first conductive material.

[0054] At this time, the average size of the second conductive material may be 1 - 100 μm. Specifically, it may be 1 - 80 μm; 1 - 60 μm; 1 - 50 μm; 1 - 40 μm; 1 - 20 μm; 1 - 10 μm; 1 - 5 μm; 10 - 100 μm; 50 - 100 μm; 10 - 20 μm; 25 - 50 μm; 2 - 4 μm; 1 - 3 μm.

[0055] Moreover, when the positive electrode for the lithium secondary battery contains the first conductive material alone or contains the first conductive material and the second conductive material together with the positive electrode additive represented by Chemical Formula 1, it can exhibit a surface resistance of 3.0 Ω / sq. or less. Specifically, the positive electrode for the lithium secondary battery can exhibit a surface resistance of 2.8 Ω / sq. or less; 2.6 Ω / sq. or less; 2.4 Ω / sq. or less; 2.2 Ω / sq. or less; 2.0 Ω / sq. or less; 1.0 Ω / sq. to 3.0 Ω / sq.; 1.0 Ω / sq. to 2.6 Ω / sq.; 1.2 Ω / sq. to 2.6 Ω / sq.; 1.5 Ω / sq. to 2.5 Ω / sq.; or 1.4 Ω / sq. to 2.3 Ω / sq.

[0056] In addition, when the positive electrode for the lithium secondary battery contains both the first conductive material and the second conductive material together with the positive electrode additive represented by Chemical Formula 1, the surface resistance of the electrode can be further reduced compared to the case where the first conductive material is contained alone or the second conductive material is contained alone. Specifically, the electrode surface resistance R12 of the positive electrode containing the first conductive material and the second conductive material in the positive electrode composite layer may have a ratio R12 / R1 of 0.5 to 1.2 with respect to the electrode surface resistance R1 of the positive electrode containing the first conductive material alone in the positive electrode composite layer, or may have a ratio R12 / R2 of 0.1 to 0.8 with respect to the electrode surface resistance R2 of the positive electrode containing the second conductive material alone in the positive electrode composite layer.

[0057] More specifically, the electrode surface resistance R12 of the positive electrode containing the first conductive material and the second conductive material in the positive electrode composite layer may have a ratio R12 / R1 of 0.5 to 1.1; 0.5 to 1.0; 0.5 to 0.9; 0.6 to 1.1; 0.65 to 1.0; or 0.7 to 0.98 with respect to the electrode surface resistance R1 of the positive electrode containing the first conductive material alone in the positive electrode composite layer.

[0058] In addition, the electrode surface resistance R12 of the positive electrode containing the first conductive material and the second conductive material in the positive electrode composite layer may have a ratio R12 / R2 of 0.1 to 0.7; 0.1 to 0.6; 0.1 to 0.5; 0.1 to 0.45; 0.1 to 0.4; 0.2 to 0.8; 0.2 to 0.55; or 0.2 to 0.5 with respect to the electrode surface resistance R2 of the positive electrode containing the second conductive material alone in the positive electrode composite layer.

[0059] As an example, the electrode surface resistance R12 of the positive electrode containing the first conductive material and the second conductive material in the positive electrode composite material layer may have a ratio of 0.7 to 1.0 with respect to the electrode surface resistance R1 of the positive electrode containing only the first conductive material in the positive electrode composite material layer, or may have a ratio of 0.2 to 0.6 with respect to the electrode surface resistance R2 of the positive electrode containing only the second conductive material in the positive electrode composite material layer.

[0060] The present invention controls the surface resistance of the positive electrode for a lithium secondary battery and the surface resistance ratios R12 / R1 and R12 / R2 according to the type of conductive material contained in the positive electrode composite material layer within the above ranges, thereby preventing a decrease in the charge-discharge capacity and capacity retention rate of the lithium secondary battery due to a high surface resistance exceeding 3.0 Ω / sq., a surface resistance ratio R12 / R1 exceeding 1.2, and a surface resistance ratio R12 / R2 exceeding 0.8, and can further improve the electrical performance of the battery.

[0061] In addition, the content of the first conductive material may be included in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode composite material layer. Specifically, it may be 0.1 to 7.5 parts by weight; 0.1 to 5 parts by weight; 0.1 to 3 parts by weight; 0.1 to 1.5 parts by weight; 2 to 5 parts by weight; 4 to 7 parts by weight; 5 to 10 parts by weight; 7 to 9 parts by weight; or 0.1 to 0.9 parts by weight.

[0062] Moreover, when the first conductive material and the second conductive material are used in combination, the total content of the first conductive material and the second conductive material may be included in an amount of 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode composite material layer. Specifically, it may be 0.1 to 7.5 parts by weight; 0.1 to 5 parts by weight; 0.1 to 3 parts by weight; 0.1 to 1.5 parts by weight; 2 to 5 parts by weight; 4 to 7 parts by weight; 5 to 10 parts by weight; 7 to 9 parts by weight; or 0.1 to 0.9 parts by weight.

[0063] Here, the second conductive material may be included in an amount of 20 to 60 parts by weight with respect to 100 parts by weight of the first conductive material. Specifically, it may be included in an amount of 20 to 50 parts by weight; 20 to 45 parts by weight; 30 to 60 parts by weight; 25 to 50 parts by weight; or 30 to 50 parts by weight.

[0064] The present invention can not only effectively improve the increase in the surface resistance of the electrode due to the positive electrode additive represented by Chemical Formula 1 by controlling the content of the first conductive material and, when the first conductive material and the second conductive material are used in combination, the total content of the first conductive material and the second conductive material within the above ranges, but also prevent the activity of the positive electrode active material from decreasing due to an excessive amount of the conductive material exceeding 10 parts by weight.

[0065] On the other hand, the positive electrode active material is a positive electrode active material capable of reversible intercalation and deintercalation, and may contain, as a main component, a lithium metal composite oxide represented by the following Chemical Formula 2:

[0066] [Chemical Formula 2] Li x [Ni y Co z Mn w M 2 v O u

[0067] In the above Chemical Formula 2, M 2 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, x, y, z, w, v, and u are respectively 1.0 ≦ x ≦ 1.30, 0.1 ≦ y < 0.95, 0.01 < z ≦ 0.5, 0.01 < w ≦ 0.5, 0 ≦ v ≦ 0.2, and 1.5 ≦ u ≦ 4.5.

[0068] The lithium metal composite oxide represented by the above Chemical Formula 2 is a composite metal oxide containing lithium and nickel, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O 2 、LiNi 0.8 Co 0.1 Mn 0.1 O 2 、LiNi 0.6 Co 0.2 Mn 0.2 O 2 、LiNi 0.9Co 0.05 Mn 0.05 O 2 、LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O 2 、LiNi 0.6 Co 0.2 Mn 0.15 Al 0.05 O 2 およびLiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 O 2 may contain one or more compounds selected from the group consisting of.

[0069] In addition, the content of the above positive electrode active material may be 85 to 95 parts by weight with respect to 100 parts by weight of the positive electrode composite material layer. Specifically, it may be 88 to 95 parts by weight, 90 to 95 parts by weight, 86 to 90 parts by weight, or 92 to 95 parts by weight.

[0070] In addition, the above binder serves to bind the positive electrode active material, the positive electrode additive, and the conductive material to each other, and any material having such a function can be used without particular limitation. Specifically, examples of the above binder may include one or more resins selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinylidene fluoride (PVdF), polyacrylonitrile, polymethyl methacrylate, and copolymers thereof. As an example, the above binder may contain polyvinylidene fluoride.

[0071] In addition, the above binder may be contained in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the entire composite material layer. Specifically, it may be contained in an amount of 2 to 8 parts by weight; or 1 to 5 parts by weight.

[0072] At the same time, the average thickness of the composite material layer is not particularly limited, but specifically, it may be 50 μm to 300 μm, more specifically, 100 μm to 200 μm; 80 μm to 150 μm; 120 μm to 170 μm; 150 μm to 300 μm; 200 μm to 300 μm; or 150 μm to 190 μm.

[0073] In addition, for the positive electrode, as the positive electrode current collector, one having high conductivity can be used without inducing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, fired carbon, etc. can be used, and in the case of aluminum or stainless steel, those surface-treated with carbon, nickel, titanium, silver, etc. can also be used. Further, the positive electrode current collector can also form fine irregularities on the surface to enhance the adhesive force of the positive electrode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc. are possible. Also, the average thickness of the current collector can be appropriately applied within 3 to 500 μm in consideration of the conductivity and total thickness of the positive electrode to be manufactured.

[0074] <Method for manufacturing a positive electrode for a lithium secondary battery> Also, in one embodiment of the present invention, mixing a positive electrode additive represented by the following Chemical Formula 1; a first conductive material and a binder to produce a pre-dispersion liquid; mixing the produced pre-dispersion liquid, a positive electrode active material and a binder to produce a positive electrode slurry; coating the positive electrode slurry on a positive electrode current collector to produce a positive electrode composite material layer, and the first conductive material contains one or more of graphene, carbon nanotube, graphite nanofiber, carbon nanofiber, vapor-grown carbon fiber and activated carbon fiber, A method for manufacturing a positive electrode for a lithium secondary battery is provided, wherein the surface resistance of the produced positive electrode is 3.0 Ω / sq. or less.

[0075] [Chemical Formula 1] Li p Co (1-q) M1 q O 4

[0076] In Chemical Formula 1 above, M 1 is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, p and q are 5 ≦ p ≦ 7 and 0 ≦ q ≦ 0.5, respectively.

[0077] The method for manufacturing a positive electrode for a lithium secondary battery according to the present invention can be carried out by mixing a positive electrode additive, a first conductive material, and a binder represented by Chemical Formula 1 in advance to produce a pre-dispersion liquid, and then additionally mixing the produced pre-dispersion liquid with a positive electrode active material and a binder to produce a positive electrode slurry, and then applying the positive electrode slurry onto a positive electrode current collector and drying it to produce a positive electrode composite layer.

[0078] Here, the step of manufacturing the pre-dispersion liquid is a step of mixing a positive electrode additive, a conductive material, and a binder, and can be carried out by a usual method used in the industry when manufacturing a slurry. For example, the step of manufacturing the pre-dispersion liquid can be carried out by charging each component into a homomixer and stirring at 1,000 to 5,000 rpm for 30 to 600 minutes, and a solvent can be further added during the stirring to control the viscosity. As an example, the pre-dispersion liquid for a positive electrode according to the present invention can be manufactured by charging a positive electrode additive, a conductive material, and a binder represented by Chemical Formula 1 into a homomixer, mixing at 3,000 rpm for 60 minutes, injecting an N-methylpyrrolidone solvent, and adjusting the viscosity at 25 ± 1 °C to 7,500 ± 300 cps.

[0079] Also, the step of manufacturing the pre-dispersion liquid can be carried out under temperature and / or humidity conditions satisfying a specific range in order to prevent decomposition and / or damage of a structurally unstable positive electrode additive.

[0080] Specifically, the step of manufacturing the pre-dispersion liquid can be carried out under temperature conditions of 40°C or lower. More specifically, it can be carried out under temperature conditions of 10°C to 40°C; 10°C to 35°C; 10°C to 30°C; 10°C to 25°C; 10°C to 20°C; 15°C to 40°C; 20°C to 40°C; 15°C to 35°C; or 18°C to 30°C.

[0081] Moreover, the step of manufacturing the pre-dispersion liquid can be carried out under conditions of a relative humidity (RH) of 10% or lower. More specifically, it can be carried out under conditions of a relative humidity (RH) of 9% or lower, 8% or lower, 7% or lower, 6% or lower, 5% or lower, 4% or lower, 3% or lower, 2% or lower, 1% or lower.

[0082] According to the present invention, by controlling the temperature and / or humidity conditions as described above during the manufacture of the pre-dispersion liquid, it is possible to prevent the occurrence of side reactions such as reactions with moisture and / or oxygen in the air during the process of mixing the particulate positive electrode additive with a conductive material or the like, thereby preventing a decrease in irreversible activity and enabling the surface resistance of the positive electrode composite layer to be realized at a low level.

[0083] Moreover, the step of manufacturing the positive electrode slurry can be carried out by additionally mixing a second conductive material when additionally mixing the positive electrode active material and the binder into the manufactured pre-dispersion liquid. The second conductive material can also be mixed together with the first conductive material during the manufacture of the pre-dispersion liquid. However, according to the present invention, the positive electrode additive and the first conductive material contained in the pre-dispersion liquid can be uniformly dispersed by means of additionally mixing the second conductive material into the manufactured pre-dispersion liquid. At the same time, the first conductive material can more effectively form an electrical network on the surface of the positive electrode additive.

[0084] <Lithium secondary battery> Moreover, in one embodiment of the present invention, There is provided a lithium secondary battery including the positive electrode according to the present invention described above, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

[0085] The lithium secondary battery according to the present invention includes the positive electrode of the present invention as described above, and not only generates a small amount of oxygen gas during charge and discharge, but also can exhibit excellent charge and discharge performance.

[0086] Such a lithium secondary battery of the present invention has a structure including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

[0087] Here, the negative electrode is manufactured by applying, drying, and pressing a negative electrode active material on a negative electrode current collector, and may selectively further contain the same conductive material, organic binder polymer, additive, etc. as the positive electrode if necessary.

[0088] Further, the negative electrode active material may include, for example, a carbon material and a silicon material. The carbon material means a carbon material mainly composed of carbon atoms. Such carbon materials include graphite having a complete layered crystal structure like natural graphite, soft carbon having a low crystalline layered crystal structure (graphene structure; a structure in which hexagonal honeycomb-shaped planes of carbon are arranged in layers), and hard carbon in which such a structure is mixed with an amorphous part, artificial graphite, expanded graphite, carbon fiber, non-graphitizable carbon, carbon black, acetylene black, ketjen black, carbon nanotube, fullerene, activated carbon, graphene, carbon nanotube, etc. may be included, and preferably, one or more selected from the group consisting of natural graphite, artificial graphite, graphene, and carbon nanotube may be included. More preferably, the carbon material includes natural graphite and / or artificial graphite, and may include one or more of graphene and carbon nanotube together with the natural graphite and / or artificial graphite. In this case, the carbon material may include 0.1 to 10 parts by weight of graphene and / or carbon nanotube based on 100 parts by weight of the whole carbon material, and more specifically, 0.1 to 5 parts by weight; or 0.1 to 2 parts by weight of graphene and / or carbon nanotube based on 100 parts by weight of the whole carbon material.

[0089] Further, the silicon material is particles containing silicon (Si) as a main component as a metal component, and may contain one or more of silicon (Si) particles and silicon oxide (SiO X , where 1 ≦ X ≦ 2). As an example, the silicon material may contain silicon (Si) particles, silicon monoxide (SiO) particles, silicon dioxide (SiO 2 ), or a mixture of these particles.

[0090] Also, the silicon material may have a form in which crystalline particles and amorphous particles are mixed, and the ratio of the amorphous particles may be 50 to 100 parts by weight, specifically 50 to 90 parts by weight; 60 to 80 parts by weight; or 85 to 100 parts by weight with respect to 100 parts by weight of the entire silicon material. By controlling the ratio of the amorphous particles contained in the silicon material within the above range, the present invention can improve the thermal stability and flexibility without degrading the electrical properties of the electrode.

[0091] Also, the silicon material may contain a carbon material and a silicon material, and may be contained in an amount of 1 to 20 parts by weight, specifically 5 to 20 parts by weight; 3 to 10 parts by weight; 8 to 15 parts by weight; 13 to 18 parts by weight; or 2 to 7 parts by weight with respect to 100 parts by weight of the negative electrode composite material layer.

[0092] By adjusting the contents of the carbon material and the silicon material contained in the negative electrode active material within the above range, the present invention can reduce the lithium consumption amount and the irreversible capacity loss during the initial charge and discharge of the battery, and improve the charge capacity per unit mass.

[0093] As an example, the negative electrode active material contains 95 ± 2 parts by weight of graphite and; silicon monoxide (SiO) particles and silicon dioxide (SiO 2) It may contain 5 ± 2 parts by weight of a mixture in which the particles are uniformly mixed. By adjusting the contents of the carbon material and the silicon material contained in the negative electrode active material within the above ranges, the present invention can reduce the lithium consumption amount and the irreversible capacity loss during the initial charge and discharge of the battery, and improve the charge capacity per unit mass.

[0094] Further, the negative electrode composite material layer may have an average thickness of 100 μm to 200 μm, specifically, it may have an average thickness of 100 μm to 180 μm, 100 μm to 150 μm, 120 μm to 200 μm, 140 μm to 200 μm, or 140 μm to 160 μm.

[0095] Further, the negative electrode current collector is not particularly limited as long as it has high conductivity without inducing a chemical change in the battery. For example, copper, stainless steel, nickel, titanium, fired carbon, etc. can be used. In the case of copper or stainless steel, those surface-treated with carbon, nickel, titanium, silver, etc. can also be used. Also, similar to the positive electrode current collector, the negative electrode current collector can form fine irregularities on the surface to strengthen the bonding force with the negative electrode active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, non-woven fabrics, etc. are possible. Further, the average thickness of the negative electrode current collector can be appropriately applied within 3 to 500 μm in consideration of the conductivity and the total thickness of the manufactured negative electrode.

[0096] Further, the separation membrane is interposed between the positive electrode and the negative electrode, and an insulating thin film having high ion permeability and mechanical strength is used. The separation membrane is not particularly limited as long as it is commonly used in the art. Specifically, sheets or non-woven fabrics made of chemical-resistant and hydrophobic polypropylene, glass fibers, or polyethylene can be used. In some cases, a composite separation membrane in which inorganic particles / organic particles are coated on a porous polymer substrate such as the above sheet or non-woven fabric with an organic binder polymer can also be used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte can also serve as the separation membrane. Further, the pore diameter of the separation membrane may be 0.01 to 10 μm on average, and the thickness may be 5 to 300 μm on average.

[0097] On the other hand, the positive electrode and the negative electrode may be wound in a jelly roll form and housed in a cylindrical battery, a prismatic battery, or a pouch-type battery, or may be housed in a pouch-type battery in a folding or stack-and-fold form, but is not limited thereto.

[0098] Further, the lithium salt-containing electrolyte according to the present invention may be composed of an electrolyte and a lithium salt. As the electrolyte, an aprotic organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, or the like can be used.

[0099] Examples of the aprotic organic solvent include N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, triphosphate ester, trimethoxymethane, dioxolane derivative, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, ether, methyl propionate, ethyl propionate, and other aprotic organic solvents.

[0100] Examples of the above-mentioned organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate esters, polyaditation lysine, polyester sulfides, polyvinyl alcohol, polyvinylidene fluoride, polymer materials containing ionic dissociation groups, and the like.

[0101] Examples of the above-mentioned inorganic solid electrolyte include Li 3 N, LiI, Li 5 NI 2 、Li 3 N-LiI-LiOH, LiSiO 4 、LiSiO 4 -LiI-LiOH, Li 2 SiS 3 、Li 4 SiO 4 、Li 4 SiO 4 -LiI-LiOH, Li 3 PO 4 -Li 2 S-SiS 2 Such as Li nitrides, halides, sulfates, etc. can be used.

[0102] The above-mentioned lithium salts are substances that are easily soluble in non-aqueous electrolytes. For example, LiCl, LiBr, LiI, LiClO 4 、LiBF 4 、LiB 10 Cl 10 、LiPF 6 、LiCF 3 SO 3 、LiCF 3 CO 2 、LiAsF 6 、LiSbF 6 、LiAlCl 4 、CH 3 SO 3 Li, (CF 3 SO 2 ) 2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium tetraphenylborate, imide, etc. can be used.

[0103] In addition, for the purpose of improving charge-discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinoneimine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. may be added to the electrolytic solution. In some cases, for imparting nonflammability, it may further contain halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride, for improving high-temperature storage characteristics, it may further contain carbon dioxide gas, and it may further contain fluoroethylene carbonate (FEC), propene sultone (PRS), etc.

[0104] Hereinafter, the present invention will be described in more detail based on examples and experimental examples.

[0105] However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0106] <Examples 1 to 6 and Comparative Examples 1 to 2. Production of positive electrode for lithium secondary battery> Inject N-methylpyrrolidone into a homomixer, and as a positive electrode additive, Li 6 Co 0.7 Zn 0.3 O 4Weighed and added 5 parts by weight; and 1 part by weight of PVdF as a binder, and after adding carbon nanotubes (average size: 60 ± 10 nm) as the first conductive material, it was mixed once at 2,000 rpm for 30 minutes to produce a pre-dispersion liquid for manufacturing the positive electrode. At this time, the content, temperature, and relative humidity (RH) conditions of the first conductive material used during the production of the pre-dispersion liquid are shown in Table 1 below.

[0107] Next, LiNi as the positive electrode active material was added to the homomixer containing the produced pre-dispersion liquid. 0.6 Co 0.2 Mn 0.2 O 2 ; Denka black (average size: 2 ± 0.5 μm) as the second conductive material; and PVdF as a binder were weighed and added, and secondary mixing was performed at 2,500 rpm for 30 minutes to produce a positive electrode slurry for a lithium secondary battery. At this time, the content of PVdF was 1 part by weight with respect to 100 parts by weight of the positive electrode slurry solid content, and the contents of the positive electrode active material and the second conductive material were adjusted as shown in Table 1 below.

[0108] After applying the produced positive electrode slurry to one side of an aluminum current collector, it was dried at 100 °C and rolled to produce a positive electrode. At this time, the total thickness of the positive electrode composite layer was 130 μm, and the total thickness of the produced positive electrode was about 200 μm.

[0109]

Table 1

[0110] <Comparative Example 3. Manufacture of Positive Electrode for Lithium Secondary Battery> Inject N-methylpyrrolidone into a homomixer, and for 100 parts by weight of the positive electrode slurry solid content, LiNi as the positive electrode active material. 0.6 Co 0.2 Mn 0.2 O 2 92.3 parts by weight; Li as a positive electrode additive. 6 Co 0.7 Zn 0.3 O 45 parts by weight; 0.7 parts by weight of carbon nanotubes (average size: 60 ± 10 nm) as the first conductive material; 0.2 parts by weight of Denka black (average size: 2 ± 0.5 μm) as the second conductive material; 2 parts by weight of PVdF as a binder were weighed and added, and mixed at 2,000 rpm for 60 minutes to produce a positive electrode slurry for a lithium secondary battery. At this time, the temperature and relative humidity (RH) were adjusted to 20 - 25 °C and 3%, respectively.

[0111] After applying the produced positive electrode slurry to one side of an aluminum current collector, it was dried at 100 °C and rolled to produce a positive electrode. At this time, the total thickness of the positive electrode composite layer was 130 μm, and the total thickness of the produced positive electrode was about 200 μm.

[0112] <Comparative Example 4. Production of a Positive Electrode for a Lithium Secondary Battery> During the production of the pre-dispersion liquid, instead of carbon nanotubes (average size: 60 ± 10 nm) as the first conductive material, Denka black (average size: 2 ± 0.5 μm) was used, and during the production of the positive electrode slurry, instead of Denka black (average size: 2 ± 0.5 μm) as the second conductive material, carbon nanotubes (average size: 60 ± 10 nm) were used. A positive electrode was produced in the same manner as in Example 1, except for this.

[0113] <Examples 7 - 12 and Comparative Examples 5 - 8. Production of a Lithium Secondary Battery> Natural graphite and silicon (SiOx, where 1 ≤ x ≤ 2) particles as the negative electrode active material and styrene-butadiene rubber (SBR) as a binder were prepared, and a negative electrode slurry was prepared in the same manner as the method for producing the positive electrode slurry. At this time, the graphite used during the production of the negative electrode composite layer was natural graphite (average particle size: 0.01 - 0.5 μm), and the silicon (SiOx) particles used had an average particle size of 0.9 - 1.1 μm. After applying the prepared negative electrode slurry to one side of a copper current collector, it was dried at 100 °C and rolled to produce a negative electrode. At this time, the total thickness of the negative electrode composite layer was 150 μm, and the total thickness of the produced negative electrode was about 250 μm.

[0114] A porous polyethylene (PE) film separator (thickness: about 16 μm) was interposed between the above-mentioned negative electrode and the positive electrodes manufactured in Examples 1 to 6 and Comparative Examples 1 to 4, and E2DVC was injected as an electrolytic solution to fabricate a full cell form cell.

[0115] Here, "E2DVC" is a kind of carbonate-based electrolytic solution, which is a mixture of ethylene carbonate (EC): dimethyl carbonate (DMC): diethyl carbonate (DEC) = 1:1:1 (volume ratio), to which lithium hexafluorophosphate (LiPF 6 , 1.0 M) and vinyl carbonate (VC, 2 wt%) are mixed solutions.

[0116]

Table 2

[0117] <Experimental Example> In order to evaluate the performance of the positive electrode for a lithium secondary battery according to the present invention, the following experiments were conducted.

[0118] i) Evaluation of electrode surface resistance For the positive electrodes manufactured in Examples 1 to 6 and Comparative Examples 1 to 4, the surface resistance of the electrodes was measured by a 4-point probe method, and the results are shown in Table 3 and FIG. 1 below.

[0119] ii) Evaluation of the amount of degassed oxygen gas during charge and discharge For the lithium secondary batteries manufactured in Examples 7 to 12 and Comparative Examples 5 to 8, initial charging (formation) was performed at 55 °C under the conditions of 3.5 V and 1.0 C. By performing the above initial charging, the gas generated at the positive electrode was degassed, and the content of oxygen gas generated during the initial charging was analyzed. Next, 50 charge and discharge cycles were repeatedly performed at 45 °C under the condition of 0.3 C each, and the content of oxygen gas during each charge and discharge was additionally analyzed. The analyzed results are shown in Table 3 below.

[0120] iii) Evaluation of charge-discharge capacity and retention rate For the lithium secondary batteries manufactured in Examples 7 to 12 and Comparative Examples 5 to 8, they were charged at a charging current of 0.1 C at a temperature of 25 °C until the charging cut-off voltage reached 4.2 to 4.25 V, and charging was carried out until the current density became 0.01 C at the cut-off voltage to be activated. Thereafter, they were discharged at a discharge current of 0.1 C until the cut-off voltage reached 2 V, and the initial charge-discharge capacity per unit mass was measured.

[0121] Next, charge and discharge were repeatedly performed 50 times under the condition of 0.3 C at 45 °C respectively, the capacity was measured during charge and discharge, and after 50 charge and discharge cycles, the charge-discharge capacity retention rate was calculated. The results are shown in Table 3 below.

[0122]

Table 3

[0123] Referring to Table 3 and FIG. 1 above, the positive electrode for a lithium secondary battery of the example manufactured according to the present invention contains a first conductive material having a linear structure in the positive electrode composite material layer, and despite containing a positive electrode additive represented by Chemical Formula 1 with low powder electrical conductivity, it is shown to have a low surface resistance of 2.5 Ω / sq. or less, and it can be seen that it shows a lower surface resistance compared with the case of containing the first conductive material or a second conductive material having no linear structure alone. Further, the lithium secondary battery including this not only has a high initial charge-discharge capacity of 102 Ah or more, but also shows a high capacity retention rate of 91% or more. Moreover, it was confirmed that the amount of oxygen gas generated after the initial charge and discharge of the above lithium secondary battery was significantly reduced and the safety was high.

[0124] From such results, it can be understood that the positive electrode for a lithium secondary battery according to the present invention is manufactured using a pre-dispersion liquid containing a positive electrode additive represented by Chemical Formula 1, which is an irreversible additive, and a conductive material having a linear structure in the positive electrode composite material layer, and by adjusting the electrode surface resistance to satisfy a specific range, the amount of oxygen gas generated during charge and discharge can be reduced, and the charge-discharge efficiency of the lithium secondary battery can be easily improved.

[0125] As described above with reference to the preferred embodiments of the present invention, those skilled in the art or those with ordinary knowledge in the art will understand that the present invention can be variously modified and changed without departing from the spirit and technical scope of the present invention described in the claims to be described later.

[0126] Therefore, the technical scope of the present invention should not be limited to the content described in the detailed description of the specification, but should be determined by the claims.

Claims

1. A positive electrode current collector, A positive electrode composite layer located on the positive electrode current collector and containing a positive electrode active material, a positive electrode additive represented by the following Chemical Formula 1, a first conductive material, and a binder, The first conductive material contains one or more of carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers, The surface resistance is 2.6 Ω / sq. or less, A positive electrode for a lithium secondary battery in which the first conductive material forms an electrical network on the surface of the positive electrode additive: [Chemical Formula 1] Li ｐ Co （１－ｑ） M １ ｑ O ４ In Chemical Formula 1, M １ is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, p and q are 5 ≤ p ≤ 7 and 0 ≤ q ≤ 0.5, respectively.

2. The positive electrode composite layer further contains a second conductive material, The second conductive material contains one or more of natural graphite, artificial graphite, carbon black, acetylene black, Denka black, Ketjen black, Super P, channel black, furnace black, lamp black, and thermal black. The positive electrode for a lithium secondary battery according to Claim 1.

3. The electrode surface resistance R12 of the positive electrode containing the first conductive material and the second conductive material in the positive electrode composite layer is It has a ratio R12 / R1 of 0.5 to 1.2 with respect to the electrode surface resistance R1 of the positive electrode containing only the first conductive material in the positive electrode composite layer, or It has a ratio R12 / R2 of 0.1 to 0.8 with respect to the electrode surface resistance R2 of the positive electrode containing only the second conductive material in the positive electrode composite layer. The positive electrode for a lithium secondary battery according to Claim 2.

4. The electrode surface resistance R12 of the positive electrode containing the first conductive material and the second conductive material in the positive electrode composite layer is It has a ratio R12 / R1 of 0.7 to 1.0 with respect to the electrode surface resistance R1 of the positive electrode containing only the first conductive material in the positive electrode composite layer, or It has a ratio R12 / R2 of 0.2 to 0.6 with respect to the electrode surface resistance R2 of the positive electrode containing only the second conductive material in the positive electrode composite layer. The positive electrode for a lithium secondary battery according to Claim 2.

5. The positive electrode additive has a tetragonal crystal structure with a space group of P4 ２ / nmc, and is the positive electrode for a lithium secondary battery according to claim 1.

6. The content of the positive electrode additive is 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode composite layer. The positive electrode for a lithium secondary battery according to Claim 1.

7. The content of the first conductive material is 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode composite layer. The positive electrode for a lithium secondary battery according to Claim 1.

8. The total content of the first conductive material and the second conductive material is 0.1 to 10 parts by weight with respect to 100 parts by weight of the positive electrode composite layer. The positive electrode for a lithium secondary battery according to Claim 2.

9. The positive electrode for a lithium secondary battery according to claim 2, wherein the second conductive material is contained in an amount of 20 to 60 parts by weight with respect to 100 parts by weight of the first conductive material.

10. The positive electrode for a lithium secondary battery according to claim 1, wherein the positive electrode active material is a lithium metal composite oxide represented by the following Chemical Formula 2: [Chemical Formula 2] Li ｘ [Ni ｙ Co ｚ Mn ｗ M ２ ｖ O ｕ In the Chemical Formula 2, M ２ is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, x, y, z, w, v, and u are 1.0 ≤ x ≤ 1.30, 0.1 ≤ y < 0.95, 0.01 < z ≤ 0.5, 0.01 < w ≤ 0.5, 0 ≤ v ≤ 0.2, and 1.5 ≤ u ≤ 4.5, respectively.

11. A positive electrode additive represented by the following Chemical Formula 1; a step of mixing the first conductive material and a binder to produce a pre-dispersion liquid, a step of mixing the produced pre-dispersion liquid, the positive electrode active material, and a binder to produce a positive electrode slurry, a step of applying the positive electrode slurry onto a positive electrode current collector to produce a positive electrode composite layer, and the first conductive material contains one or more of carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers, A method for manufacturing a positive electrode for a lithium secondary battery, wherein the surface resistance of the produced positive electrode is 3.0 Ω / sq. or less: [Chemical Formula 1] Li ｐ Co （１－ｑ） M １ ｑ O ４ In the Chemical Formula 1, M １ is one or more elements selected from the group consisting of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, p and q are 5 ≤ p ≤ 7 and 0 ≤ q ≤ 0.5, respectively.

12. The method for manufacturing a positive electrode for a lithium secondary battery according to claim 11, wherein the step of manufacturing the pre-dispersion liquid is performed under the condition of a relative humidity of 10% or less.

13. The method for manufacturing a positive electrode for a lithium secondary battery according to claim 11, wherein the step of manufacturing the positive electrode slurry further mixes a second conductive material.

14. A lithium secondary battery including the positive electrode according to claim 1, a negative electrode, and a separator positioned between the positive electrode and the negative electrode.

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