Positive electrode for lithium secondary battery and lithium secondary battery containing 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 using a linear dispersion containing a positive electrode additive represented by Formula 1 and a linear conductive material in a positive electrode composite layer which is an irreversible additive. By controlling the electrode sheet resistance to satisfy a specific range, the amount of oxygen gas generated during charging and discharging can be reduced, and the charging and discharging efficiency of the lithium secondary battery can be easily improved.

Description

Technology Field

[0001] The present invention relates to a positive electrode for a lithium secondary battery and a lithium secondary battery including the same. Background Technology

[0003] Recently, the demand for rechargeable batteries as an energy source has been increasing rapidly. Among these rechargeable batteries, lithium-ion batteries, which possess high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used.

[0004] Although graphite is primarily used as a negative electrode material for lithium secondary batteries, it is difficult to increase the capacity of lithium secondary batteries because graphite has a low capacity of 372 mAh / g per unit mass. Accordingly, to increase the capacity of lithium secondary batteries, negative electrode materials that form intermetallic compounds with lithium, such as silicon, tin, and their oxides, are being developed and used as non-carbon negative electrode materials that have a higher energy density than graphite. However, in the case of these non-carbon negative electrode materials, although the capacity is high, there is a problem in that the initial efficiency is low, resulting in a large amount of lithium consumption during the initial charge and discharge cycles and a large irreversible capacity loss.

[0005] In this regard, a method has been proposed to overcome irreversible capacity loss of the anode by using a material that can provide a lithium ion source or storage to the cathode material and exhibits electrochemical activity after the first cycle so as not to degrade the overall performance of the battery. Specifically, a method is known in which an oxide containing an excess amount of lithium, such as Li6CoO4, is applied to the cathode as a sacrificial cathode material or an irreversible additive (or over-discharge inhibitor).

[0006] Meanwhile, conventional irreversible additives such as the above Li6CoO4 are generally manufactured by reacting cobalt oxide, etc., with an excess amount of lithium oxide. The irreversible additive manufactured in this way is structurally unstable and generates a large amount of oxygen gas (O2) as charging proceeds. If the irreversible additive does not fully react and remains during the initial charging of the secondary battery, that is, during the activation of the battery, it may cause a reaction during the subsequent charging and discharging process, thereby generating side reactions or a large amount of oxygen gas inside the battery. The oxygen gas generated in this way can cause volume expansion of the electrode assembly, and thus act as one of the main factors causing a decrease in battery performance.

[0007]

[0008] In addition, conventionally used irreversible additives are nearly insulators due to their 2D percolating network, ~10 -11 It exhibits a very low electrical conductivity of S / cm. This low electrical conductivity increases the electrical resistance of the anode. In this case, it exhibits a large capacity of over 200 mAh / g at low C-rates, but as the C-rate increases, the performance decreases rapidly as charging and discharging proceeds due to the high resistance, so the charge and discharge capacity of the battery decreases, and there is a limitation that high-speed charging and discharging is difficult.

[0009] Therefore, there is a need for the development of lithium secondary batteries that not only have excellent electrical performance but also improved safety. Prior art literature

[0011] Republic of Korea Published Patent Application No. 10-2019-0064423 The problem to be solved

[0012] Accordingly, the objective of the present invention is to provide a positive electrode for a lithium secondary battery with improved safety while effectively improving the electrical properties of the lithium secondary battery, and a lithium secondary battery including the same. means of solving the problem

[0014] In order to solve the aforementioned problem,

[0015] In one embodiment of the present invention,

[0016] positive current collector, and

[0017] A positive composite layer is provided, positioned on the positive current collector, and comprises a positive active material, a positive additive represented by the following chemical formula 1, a first conductive material, and a binder;

[0018] The first conductive material contains one or more of carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers;

[0019] A positive electrode for a lithium secondary battery having a sheet resistance of 3.0 Ω / sq. or less is provided:

[0020] [Chemical Formula 1]

[0021] Li p Co (1-q) M 1 q O4

[0022] In the above chemical formula 1,

[0023] M 1 It 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

[0024] p and q are 5≤p≤7 and 0≤q≤0.5, respectively.

[0025] At this time, the anode composite layer may further include 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.

[0026] Additionally, the electrode sheet resistance (R12) of the anode containing the first conductive material and the second conductive material in the anode composite layer may have a ratio (R12 / R1) of 0.5 to 1.2 with the electrode sheet resistance (R1) of the anode containing only the first conductive material in the anode composite layer, or a ratio (R12 / R2) of 0.1 to 0.8 with the electrode sheet resistance (R2) of the anode containing only the second conductive material in the anode composite layer.

[0027] Specifically, the electrode sheet resistance (R12) of the anode containing the first conductive material and the second conductive material in the anode composite layer may have a ratio (R12 / R1) of 0.7 to 1.0 with the electrode sheet resistance (R1) of the anode containing only the first conductive material in the anode composite layer, or a ratio (R12 / R2) of 0.2 to 0.6 with the electrode sheet resistance (R2) of the anode containing only the second conductive material in the anode composite layer.

[0028] In addition, the above-mentioned anode additive may have a tetragonal structure with a space group of P42 / nmc.

[0029] In addition, the content of the anode additive may be 0.1 to 10 parts by weight per 100 parts by weight of the anode composite layer.

[0030] In addition, the content of the first conductive material may be 0.1 to 10 parts by weight per 100 parts by weight of the anode composite layer.

[0031] In addition, when the first conductive material and the second conductive material are included together, the total content of the first conductive material and the second conductive material may be 0.1 to 10 parts by weight per 100 parts by weight of the anode composite layer, and in this case, the second conductive material may be included in an amount of 20 to 60 parts by weight per 100 parts by weight of the first conductive material.

[0032] Meanwhile, the above-mentioned positive electrode active material may be a lithium metal composite oxide represented by the following chemical formula 2:

[0033] [Chemical Formula 2]

[0034] Li x [Ni y Co z Mn w M 2 v ]O u

[0035] In the above chemical formula 2,

[0036] 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, and

[0037] x, y, z, w, v, and u are 1.0≤x≤1.30, 0.1≤y<0.95, and 0.01, respectively. <z≤0.5, 0.01<w≤0.5, 0≤v≤0.2, 1.5≤u≤4.5이다.

[0039] In addition, in one embodiment of the present invention,

[0040] A positive additive represented by the following chemical formula 1; a step of preparing a pre-dispersion solution by mixing a first conductive material and a binder;

[0041] A step of preparing an anode slurry by mixing a prepared pre-dispersion, an anode active material, and a binder; and

[0042] The method includes the step of preparing an anode composite layer by applying the anode slurry onto an anode current collector;

[0043] The first conductive material contains one or more of carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers;

[0044] A method for manufacturing a cathode for a lithium secondary battery is provided, wherein the sheet resistance of the manufactured cathode is 3.0 Ω / sq. or less:

[0045] [Chemical Formula 1]

[0046] Li p Co (1-q) M 1 q O4

[0047] In the above chemical formula 1,

[0048] M 1 It 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

[0049] p and q are 5≤p≤7 and 0≤q≤0.5, respectively.

[0050] At this time, the step of preparing the above-mentioned pre-dispersion liquid can be performed under conditions of 10% or less relative humidity.

[0051] In addition, the step of preparing the anode slurry may further mix a second conductive material.

[0053] Furthermore, in one embodiment of the present invention,

[0054] The present invention provides a lithium secondary battery comprising a positive electrode according to the invention described above; a negative electrode; and a separator located between the positive electrode and the negative electrode. Effects of the invention

[0056] The positive electrode for a lithium secondary battery according to the present invention is manufactured using a linear dispersion containing a positive electrode additive represented by Formula 1 and a linearly structured conductive material in a positive electrode composite layer which is an irreversible additive, and by adjusting the electrode sheet resistance to satisfy a specific range, it is possible to reduce the amount of oxygen gas generated during charging and discharging, as well as easily improve the charging and discharging efficiency of the lithium secondary battery. Brief explanation of the drawing

[0058] Figure 1 is a graph showing the sheet resistance of the anodes prepared in Example 1, Example 2 and Comparative Example 2. Specific details for implementing the invention

[0059] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are to be described in detail in the detailed description.

[0060] However, this is not intended to limit the invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0061] In the present invention, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0062] Furthermore, in the present invention, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately above" the other part, but also cases where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only cases where it is "immediately below" the other part, but also cases where there is another part in between. Additionally, in the present application, being "placed on" may include cases where it is placed on the lower part as well as on the upper part.

[0063] In addition, in the present invention, "main component" may mean 50% or more by weight, 60% or more by weight, 70% or more by weight, 80% or more by weight, 90% or more by weight, 95% or more by weight, or 97.5% or more by weight with respect to the total weight of the composition or specific component, and in some cases, may mean 100% by weight when constituting the entire composition or specific component.

[0064] In addition, in the present invention, "Ah" is a unit of capacity for a lithium secondary battery, referred to as "ampere-hour," and signifies the amount of current per hour. For example, if the battery capacity is "3000 mAh," it means that it can be discharged for one hour with a current of 3000 mA.

[0066] The present invention will be described in more detail below.

[0068] cathode for lithium secondary batteries

[0069] In one embodiment of the present invention,

[0070] positive current collector, and

[0071] A positive composite layer is provided, positioned on the positive current collector, and comprises a positive active material, a positive additive represented by the following chemical formula 1, a first conductive material, and a binder;

[0072] The first conductive material contains one or more of graphene, carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers;

[0073] A positive electrode for a lithium secondary battery having a sheet resistance of 3.0 Ω / sq. or less is provided:

[0074] [Chemical Formula 1]

[0075] Li p Co (1-q) M 1 q O4

[0076] In the above chemical formula 1,

[0077] M 1 It 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

[0078] p and q are 5≤p≤7 and 0≤q≤0.5, respectively.

[0080] The positive electrode for a lithium secondary battery according to the present invention comprises a positive electrode composite layer manufactured by applying, drying, and pressing a positive electrode slurry onto a positive electrode current collector, and the positive electrode composite layer has a composition containing a positive electrode active material, a positive electrode additive, a conductive material, and a binder.

[0081] At this time, the anode additive may be lithium cobalt oxide represented by the following chemical formula 1:

[0082] [Chemical Formula 1]

[0083] Li p Co (1-q) M 1 q O4

[0084] In the above chemical formula 1,

[0085] M 1It 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

[0086] p and q are 5≤p≤7 and 0≤q≤0.5, respectively.

[0087] The above-mentioned cathode additive contains an excess amount of lithium, which can provide lithium for lithium consumption caused by irreversible chemical and physical reactions at the anode during initial charging, thereby increasing the charge capacity of the battery and reducing irreversible capacity, which can improve lifespan characteristics.

[0088] Among these, the cathode additive represented by Chemical Formula 1 above has a higher lithium ion content compared to nickel-containing oxides commonly used in the industry. Since this allows for the replenishment of lithium ions lost due to irreversible reactions during the initial activation of the battery, the charge and discharge capacity of the battery can be significantly improved. Furthermore, compared to iron and / or manganese-containing oxides commonly used in the industry, it has the advantage of excellent battery stability as there are no side reactions caused by the leaching of transition metals during battery charging and discharging. Examples of such lithium metal oxides represented by Chemical Formula 1 include Li6CoO4 and Li6Co 0.5 Zn 0.5 O4, Li6Co 0.7 Zn 0.3 It may include O4, etc.

[0089] In addition, the anode additive represented by Chemical Formula 1 above may have a tetragonal crystal structure, and among these, may be included in the space group of P42 / nmc having a twisted tetrahedral structure formed by cobalt and oxygen atoms. Since the anode additive has a twisted tetrahedral structure formed by cobalt and oxygen atoms and is structurally unstable, if it is used in an amount of 5 parts by weight or less per 100 parts by weight of the anode composite layer during anode manufacturing, it may cause side reactions with moisture or oxygen in the air during the mixing process of the anode slurry. However, the present invention has the advantage of preventing the anode additive from causing side reactions with moisture or oxygen in the air by using a composition in which the anode additive is pre-dispersed when manufacturing the anode slurry.

[0090] In addition, the above-mentioned anode additive may be included in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the anode composite layer, and specifically, may be included 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 per 100 parts by weight of the anode composite layer. By controlling the content of the anode additive to the above range, the present invention can prevent a decrease in charge / discharge capacity due to insufficient replenishment of lithium ions lost by irreversible reactions caused by a low content of the anode additive, and can prevent a large amount of oxygen gas from being generated during the charge / discharge of the battery due to an excessive amount of anode additive.

[0091] In addition, the positive electrode for the lithium secondary battery may include a first conductive material in the positive electrode composite layer, and the first conductive material may contain one or more of graphene, carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers having a linear structure.

[0092] At this time, the average size of the first conductive material may be 500 nm or less, specifically 10 to 500 nm; 10 to 400 nm; 10 to 300 nm; 10 to 200 nm; 10 to 100 nm; 50 to 500 nm; 100 to 500 nm; 200 to 500 nm; 250 to 500 nm; 300 to 500 nm; 400 to 500 nm; 100 to 300 nm; 200 to 400 nm; or 50 to 250 nm. Here, the average size may refer to the average length of the first conductive material.

[0093] The present invention can form a conductive path on the surface of an anode additive with low powder electrical conductivity by controlling the average size of a first conductive material having a linear structure to the range described above, thereby further lowering the resistance of the anode.

[0094] In addition, the anode composite layer may further include 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.

[0095] At this time, the average size of the second conductive material may be 1 to 100 μm, and specifically, 1 to 80 μm; 1 to 60 μm; 1 to 50 μm; 1 to 40 μm; 1 to 20 μm; 1 to 10 μm; 1 to 5 μm; 10 to 100 μm; 50 to 100 μm; 10 to 20 μm; 25 to 50 μm; 2 to 4 μm; 1 to 3 μm.

[0096] Furthermore, the cathode for the lithium secondary battery may exhibit a sheet resistance of 3.0 Ω / sq. or less when comprising the first conductive material alone together with the cathode additive represented by Chemical Formula 1, or when comprising the first conductive material and the second conductive material. Specifically, the cathode for the lithium secondary battery may exhibit a sheet 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. It can exhibit a sheet resistance of up to 2.3 Ω / sq.

[0097] In addition, when a cathode for a lithium secondary battery contains a first conductive material and a second conductive material together with a cathode additive represented by Chemical Formula 1, the sheet resistance of the electrode may be lowered compared to when the first conductive material is contained alone or the second conductive material is contained alone. Specifically, the electrode sheet resistance (R12) of a cathode containing the first conductive material and the second conductive material in the cathode composite layer may have a ratio (R12 / R1) of 0.5 to 1.2 with the electrode sheet resistance (R1) of a cathode containing the first conductive material alone in the cathode composite layer, or a ratio (R12 / R2) of 0.1 to 0.8 with the electrode sheet resistance (R2) of a cathode containing the second conductive material alone in the cathode composite layer.

[0098] More specifically, the electrode sheet resistance (R12) of an anode containing a first conductive material and a second conductive material in the anode 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 sheet resistance (R11) of an anode containing only the first conductive material in the anode composite layer.

[0099] Additionally, the electrode sheet resistance (R12) of the anode containing the first conductive material and the second conductive material in the anode 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 sheet resistance (R2) of the anode containing only the second conductive material in the anode composite layer.

[0100] As one example, the electrode sheet resistance (R12) of the anode containing the first conductive material and the second conductive material in the anode composite layer may have a ratio of 0.7 to 1.0 with respect to the electrode sheet resistance (R1) of the anode containing only the first conductive material in the anode composite layer, or a ratio of 0.2 to 0.6 with respect to the electrode sheet resistance (R2) of the anode containing only the second conductive material in the anode composite layer.

[0101] The present invention can further improve the electrical performance of a lithium secondary battery by preventing the reduction of the charge / discharge capacity and capacity retention rate of the lithium secondary battery due to high sheet resistance exceeding 3.0 Ω / sq., a sheet resistance ratio (R12 / R1) exceeding 1.2, and a sheet resistance ratio (R12 / R2) exceeding 0.8, by controlling the sheet resistance of the positive electrode for a lithium secondary battery and the sheet resistance ratio (R12 / R1 and R12 / R2) according to the type of conductive material contained in the positive electrode composite layer to the above range.

[0102] In addition, the content of the first conductive material may be included in an amount of 0.1 to 10 parts by weight per 100 parts by weight of the anode composite layer, and 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.

[0103] Furthermore, 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 per 100 parts by weight of the anode composite layer, and 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.

[0104] Here, the second conductive material may be included in an amount of 20 to 60 parts by weight per 100 parts by weight of the first conductive material, and specifically, 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.

[0105] The present invention can effectively improve the increase in sheet resistance of an electrode caused by the anode additive represented by Formula 1 by controlling the content of the first conductive material and the total content of the first conductive material and the second conductive material in combination within the above range, and also prevent the decrease in activity of the anode active material due to an excess amount of conductive material exceeding 10 parts by weight.

[0106] Meanwhile, the above-mentioned cathode active material is a cathode active material capable of reversible intercalation and deintercalation, and may include a lithium metal composite oxide represented by the following chemical formula 2 as a main component:

[0107] [Chemical Formula 2]

[0108] Li x [Ni y Co z Mn w M 2 v ]O u

[0109] In the above chemical formula 2,

[0110] M 2is 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

[0111] x, y, z, w, v, and u are 1.0≤x≤1.30, 0.1≤y<0.95, and 0.01, respectively. <z≤0.5, 0.01<w≤0.5, 0≤v≤0.2, 1.5≤u≤4.5이다.

[0112] The lithium metal composite oxide represented by the above chemical formula 2 is a composite metal oxide containing lithium and nickel, wherein LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 O2, LiNi 0.8 Co 0.1 Mn 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.2 O2, LiNi 0.9 Co 0.05 Mn 0.05 O2, LiNi 0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiNi 0.6 Co 0.2 Mn 0.15 Al 0.05 O2 and LiNi 0.7 Co 0.1 Mn 0.1 Al 0.1 It may include one or more compounds selected from the group consisting of O2.

[0113] In addition, the content of the above-mentioned positive active material may be 85 to 95 parts by weight per 100 parts by weight of the positive composite layer, and specifically, 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.

[0114] In addition, the binder serves to bind the cathode active material, cathode additive, and conductive material together, and any binder having this function can be used without particular limitation. Specifically, the binder may include one or more resins selected from the group consisting of polyvinylidenefluoride-hexafluoropropylene copolymer (PVdF-co-HFP), polyvinylidenefluoride (PVdF), polyacrylonitrile, polymethylmethacrylate, and copolymers thereof. As one example, the binder may include polyvinylidenefluoride.

[0115] In addition, the binder may be included in an amount of 1 to 10 parts by weight with respect to 100 parts by weight of the total composite layer, specifically 2 to 8 parts by weight; or 1 to 5 parts by weight of a conductive material.

[0116] In addition, the average thickness of the composite layer is not particularly limited, but specifically may be 50㎛ to 300㎛, and more specifically may be 100㎛ to 200㎛; 80㎛ to 150㎛; 120㎛ to 170㎛; 150㎛ to 300㎛; 200㎛ to 300㎛; or 150㎛ to 190㎛.

[0117] In addition, the anode may be used as an anode current collector that has high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used, and in the case of aluminum or stainless steel, surface-treated materials such as carbon, nickel, titanium, silver, etc. may be used. Furthermore, the anode current collector may have fine irregularities formed on its surface to increase the adhesion of the anode active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible. Moreover, the average thickness of the current collector may be appropriately applied in the range of 3 to 500 μm, taking into consideration the conductivity and total thickness of the manufactured anode.

[0119] Method for manufacturing a positive electrode for a lithium secondary battery

[0120] In addition, in one embodiment of the present invention,

[0121] A positive additive represented by the following chemical formula 1; a step of preparing a pre-dispersion solution by mixing a first conductive material and a binder;

[0122] A step of preparing an anode slurry by mixing a prepared pre-dispersion, an anode active material, and a binder; and

[0123] The method includes the step of preparing an anode composite layer by applying the anode slurry onto an anode current collector;

[0124] The first conductive material contains one or more of graphene, carbon nanotubes, graphite nanofibers, carbon nanofibers, vapor-grown carbon fibers, and activated carbon fibers;

[0125] A method for manufacturing a cathode for a lithium secondary battery is provided, wherein the sheet resistance of the manufactured cathode is 3.0 Ω / sq. or less:

[0126] [Chemical Formula 1]

[0127] Li p Co (1-q) M 1 q O4

[0128] In the above chemical formula 1,

[0129] M 1 It 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

[0130] p and q are 5≤p≤7 and 0≤q≤0.5, respectively.

[0132] A method for manufacturing a positive electrode for a lithium secondary battery according to the present invention can be performed by first mixing a positive electrode additive represented by Chemical Formula 1, a first conductive material, and a binder to prepare a pre-dispersion liquid, then further mixing the prepared pre-dispersion liquid with a positive electrode active material and a binder to prepare 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.

[0133] Here, the step of preparing the pre-dispersion solution is a step of mixing the anode additive, the conductive material, and the binder, and can be performed in a conventional manner used in the industry for slurry preparation. For example, the step of preparing the pre-dispersion solution can be performed by introducing each component into a homo mixer and stirring at 1,000 to 5,000 rpm for 30 to 600 minutes, and the viscosity can be controlled by adding a solvent during the stirring. As one example, the anode pre-dispersion solution according to the present invention can be prepared by introducing the anode additive, the conductive material, and the binder represented by Formula 1 into a homo mixer and injecting N-methylpyrrolidone solvent while mixing at 3,000 rpm for 60 minutes, so that the viscosity at 25±1℃ is controlled to 7,500±300 cps.

[0134] In addition, the step of preparing the above-mentioned pre-dispersion solution may be performed under temperature and / or humidity conditions satisfying a specific range to prevent the structurally unstable anode additive from decomposing and / or being damaged.

[0135] Specifically, the step of preparing the above-mentioned pre-dispersion liquid can be performed under temperature conditions of 40°C or lower, and more specifically, 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.

[0136] In addition, the step of preparing the above-mentioned pre-dispersion liquid can be performed under relative humidity (RH) conditions of 10% or less, and more specifically, under relative humidity (RH) conditions of 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, and 1% or less.

[0137] The present invention can prevent irreversible activity degradation caused by side reactions with moisture and / or oxygen in the air during the process of mixing anode additives in the form of fine particles with conductive materials, etc., by controlling the temperature and / or humidity conditions during the preparation of the pre-dispersion liquid as described above, and can achieve a low sheet resistance of the anode composite layer.

[0138] Furthermore, the step of preparing the anode slurry may be performed by further mixing a second conductive material when additionally mixing the anode active material and the binder into the prepared pre-dispersion liquid. Although the second conductive material may be mixed together with the first conductive material when preparing the pre-dispersion liquid, the present invention allows the anode additive and the first conductive material contained in the pre-dispersion liquid to be uniformly dispersed through the method of additionally mixing the second conductive material into the prepared pre-dispersion liquid, and at the same time allows the first conductive material to more effectively form an electrical network on the surface of the anode additive.

[0140] lithium secondary battery

[0141] Furthermore, in one embodiment of the present invention,

[0142] The present invention provides a lithium secondary battery comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode according to the present invention described above.

[0143] The lithium secondary battery according to the present invention is equipped with the positive electrode of the present invention described above, and can not only reduce the amount of oxygen gas generated during charging and discharging but also exhibit excellent charging and discharging performance.

[0144] The lithium secondary battery of the present invention has a structure comprising a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode.

[0145] Here, the cathode is manufactured by applying, drying, and pressing a cathode active material onto a cathode current collector, and, if necessary, may optionally further include a conductive material, an organic binder polymer, an additive, etc., as in the anode.

[0146] In addition, the above-mentioned cathode active material may include, for example, a carbon material and a silicon material. The above-mentioned carbon material refers to a carbon material having carbon atoms as its main component. Such carbon materials may include graphite, which has a completely layered crystal structure like natural graphite; soft carbon having a low-crystallinity layered crystal structure (graphene structure; a structure in which hexagonal honeycomb-shaped planes of carbon are arranged in layers); hard carbon in which such structures are mixed with amorphous portions; artificial graphite; expanded graphite; carbon fiber; non-graphitized carbon; carbon black; acetylene black; ketjen black; carbon nanotubes; fullerene; activated carbon; graphene; carbon nanotubes; and, preferably, one or more selected from the group consisting of natural graphite, artificial graphite, graphene, and carbon nanotubes. More preferably, the above-mentioned carbon material may include natural graphite and / or artificial graphite, and together with the natural graphite and / or artificial graphite, may include one or more of graphene and carbon nanotubes. In this case, the carbon material may comprise 0.1 to 10 parts by weight of graphene and / or carbon nanotubes per 100 parts by weight of the total carbon material, and more specifically, may comprise 0.1 to 5 parts by weight or 0.1 to 2 parts by weight of graphene and / or carbon nanotubes per 100 parts by weight of the total carbon material.

[0147] In addition, the above silicon material is a particle containing silicon (Si) as a main component as a metallic component, comprising silicon (Si) particles and silicon oxide (SiO₂). X It may include one or more of the particles (1≤X≤2). As one example, the silicon material may include silicon (Si) particles, silicon monoxide (SiO) particles, silicon dioxide (SiO2) particles, or a mixture of these particles.

[0148] In addition, 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, based on 100 parts by weight of the total silicon material. By controlling the ratio of amorphous particles contained in the silicon material to the above range, the present invention can improve thermal stability and flexibility without degrading the electrical properties of the electrode.

[0149] In addition, the silicon material may include a carbon material and a silicon material, and may be included in an amount of 1 to 20 parts by weight per 100 parts by weight of the cathode composite layer, and specifically, may be included in an amount of 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 per 100 parts by weight of the cathode composite layer.

[0150] The present invention can improve the charge capacity per unit mass while reducing lithium consumption and irreversible capacity loss during the initial charge and discharge of the battery by controlling the content of carbon material and silicon material included in the negative electrode active material to the ranges described above.

[0151] As one example, the above-described negative electrode active material may comprise 95 ± 2 parts by weight of graphite and 5 ± 2 parts by weight of a mixture of silicon monoxide (SiO) particles and silicon dioxide (SiO2) particles uniformly mixed, based on 100 parts by weight of the negative electrode composite layer. By controlling the content of carbon material and silicon material included in the negative electrode active material to the above range, the present invention can improve the charge capacity per unit mass while reducing lithium consumption and irreversible capacity loss during the initial charge and discharge of the battery.

[0152] In addition, the cathode composite layer may have an average thickness of 100㎛ to 200㎛, and specifically, may have an average thickness of 100㎛ to 180㎛, 100㎛ to 150㎛, 120㎛ to 200㎛, 140㎛ to 200㎛, or 140㎛ to 160㎛.

[0153] In addition, the above-mentioned negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, nickel, titanium, calcined carbon, etc. may be used, and in the case of copper or stainless steel, surface-treated carbon, nickel, titanium, silver, etc. may be used. Furthermore, similar to the positive electrode current collector, the above-mentioned negative electrode current collector may form fine irregularities on its surface to strengthen the bonding force with the negative electrode active material, and various forms such as films, sheets, foils, nets, porous bodies, foams, and nonwoven fabrics are possible. In addition, the average thickness of the above-mentioned negative electrode current collector may be appropriately applied in the range of 3 to 500 μm, taking into consideration the conductivity and total thickness of the manufactured negative electrode.

[0154] In addition, the separator is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The separator is not particularly limited as long as it is commonly used in the industry, but specifically, a sheet or nonwoven fabric made of chemically resistant and hydrophobic polypropylene; glass fiber; or polyethylene may be used, and in some cases, a composite separator in which inorganic particles / organic particles are coated by an organic binder polymer on a porous polymer substrate such as the sheet or nonwoven fabric may be used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as the separator. Furthermore, the pore diameter of the separator may be an average of 0.01 to 10 μm, and the thickness may be an average of 5 to 300 μm.

[0155] Meanwhile, the above positive and negative electrodes may be wound into a jelly roll form and stored in a cylindrical battery, a prismatic battery, or a pouch-type battery, or stored in a pouch-type battery in a folding or stack-and-folding form, but are not limited thereto.

[0156] In addition, the lithium salt-containing electrolyte according to the present invention may consist of an electrolyte and a lithium salt, and the electrolyte may be a non-aqueous organic solvent, an organic solid electrolyte, an inorganic solid electrolyte, etc.

[0157] As the above-mentioned non-aqueous organic solvent, for example, aprotic organic solvents such as N-methyl-2-pyrrolidinone, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyrolactone, 1,2-dimethoxyethane, tetrahydroxyfranc, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, trimethoxymethane, dioxolone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl propionate, ethyl propionate, etc. may be used.

[0158] The above organic solid electrolyte may be, for example, a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, agitation lysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, a polymer containing an ionic dissociator, etc.

[0159] As the above-mentioned inorganic solid electrolyte, for example, nitrides, halides, sulfates of Li such as Li3N, LiI, Li5Ni2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH, Li3PO4-Li2S-SiS2, etc., may be used.

[0160] The above lithium salt is a substance that dissolves well in a non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl 10 LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi, lithium chloroborane, lithium lower aliphatic carboxylate, lithium 4-phenylboronicate, imide, etc. may be used.

[0161] In addition, for the purpose of improving charge / discharge characteristics and flame retardancy, the electrolyte may be further enriched with, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. In some cases, to impart non-flammability, halogen-containing solvents such as carbon tetrachloride and trifluoroethylene may be further enriched, carbon dioxide gas may be further enriched to improve high-temperature storage characteristics, and FEC (Fluoro-Ethylene Carbonate), PRS (Propene Sultone), etc.

[0163] The present invention will be explained in more detail below through examples and experimental examples.

[0164] 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.

[0166] Examples 1–6 and Comparative Examples 1–2. Preparation of cathodes for lithium secondary batteries

[0167] N-methylpyrrolidone is injected into a homo mixer, and Li6Co as an anode additive with respect to 100 parts by weight of the anode slurry solid content. 0.7 Zn 0.3 45 parts by weight of O and 1 part by weight of PVdF as a binder were weighed and added, carbon nanotubes (average size: 60±10 nm) were added as a first conductive material, and then a pre-dispersion solution for manufacturing an anode was prepared by first mixing at 2,000 rpm for 30 minutes. At this time, the content of the first conductive material and the conditions of temperature and relative humidity (RH) used in the preparation of the pre-dispersion solution are shown in Table 1 below.

[0168] Then, LiNi as the cathode active material in a homomixer containing the prepared pre-dispersion 0.6 Co 0.2 Mn 0.2 O2; Denka Black (average size: 2±0.5 μm) as a second conductive material; and PVdF as a binder were weighed and added, and a secondary mixing was performed at 2,500 rpm for 30 minutes to prepare a positive electrode slurry for a lithium secondary battery. At this time, the content of PVdF was 1 part by weight per 100 parts by weight of the positive electrode slurry solids, and the content of the positive electrode active material and the second conductive material was controlled as shown in Table 1 below.

[0169] The manufactured anode slurry was applied to one side of an aluminum current collector, dried at 100°C, and rolled to manufacture an anode. At this time, the total thickness of the anode composite layer was 130 μm, and the total thickness of the manufactured anode was approximately 200 μm.

[0170] Based on 100 parts by weight of anode slurry Conductive material content Anode active material content Temperature [℃] humidity [%] First challenge material 2nd Challenge Example 1 0.5 parts by weight 0.2 parts by weight 92.3 parts by weight 20~25 3% Example 2 0.7 parts by weight - 92.3 parts by weight 20~25 3% Example 3 0.7 parts by weight 0.1 parts by weight 92.2 parts by weight 20~25 3% Example 4 0.7 parts by weight 5 parts by weight 87.3 parts by weight 20~25 3% Example 5 0.5 parts by weight 0.2 parts by weight 92.3 parts by weight 50~55 3% Example 6 0.5 parts by weight 0.2 parts by weight 92.3 parts by weight 20~25 50% Comparative Example 1 - - 93 parts by weight 20~25 3% Comparative Example 2 - 2 parts by weight 91 parts by weight 20~25 3%

[0172] Comparative Example 3. Preparation of a cathode for a lithium secondary battery

[0173] N-methylpyrrolidone is injected into a homo mixer, and LiNi is used as the cathode active material with respect to 100 parts by weight of the cathode slurry solid content. 0.6 Co 0.2 Mn 0.2 O292.3 parts by weight; Li6Co as anode additive 0.7 Zn 0.3 45 parts by weight of O; 0.7 parts by weight of carbon nanotubes (average size: 60±10 nm) as a first conductive material; 0.2 parts by weight of Denka Black (average size: 2±0.5 μm) as a second conductive material; and 2 parts by weight of PVdF as a binder were weighed and added, and a positive electrode slurry for a lithium secondary battery was prepared by mixing at 2,000 rpm for 60 minutes. At this time, the temperature and relative humidity (RH) were controlled to 20~25℃ and 3%, respectively.

[0174] The manufactured anode slurry was applied to one side of an aluminum current collector, dried at 100°C, and rolled to manufacture an anode. At this time, the total thickness of the anode composite layer was 130 μm, and the total thickness of the manufactured anode was approximately 200 μm.

[0176] Comparative Example 4. Preparation of a cathode for a lithium secondary battery

[0177] An anode was prepared by performing the same method as in Example 1, except that Denka Black (average size: 2±0.5 μm) was used instead of the first conductive material, carbon nanotubes (average size: 60±10 nm), when preparing the pre-dispersion, and carbon nanotubes (average size: 60±10 nm) were used instead of the second conductive material, Denka Black (average size: 2±0.5 μm), when preparing the anode slurry.

[0179] Examples 7–12 and Comparative Examples 5–8. Preparation of lithium secondary batteries

[0180] Natural graphite and silicon (SiOx, where 1≤x≤2) particles as cathode active materials and styrene butadiene rubber (SBR) as a binder were prepared, and a cathode slurry was prepared in the same manner as that used to prepare the anode slurry. At this time, the graphite used to prepare the cathode composite layer was natural graphite (average particle size: 0.01~0.5㎛), and silicon (SiOx) particles with an average particle size of 0.9~1.1㎛ were used. The prepared cathode slurry was applied to one side of a copper current collector, dried at 100℃, and rolled to manufacture a cathode. At this time, the total thickness of the cathode composite layer was 150㎛, and the total thickness of the manufactured cathode was approximately 250㎛.

[0181] A full cell was fabricated by laminating a separator (thickness: about 16 μm) made of a porous polyethylene (PE) film between the above-mentioned cathode and the anode prepared in Examples 1 to 6 and Comparative Examples 1 to 4, and injecting E2DVC as the electrolyte.

[0182] Here, "E2DVC" refers to a type of carbonate-based electrolyte, which is a solution in which lithium hexafluorophosphate (LiPF6, 1.0M) and vinyl carbonate (VC, 2 wt%) are mixed with a mixture of ethylene carbonate (EC):dimethyl carbonate (DMC):diethyl carbonate (DEC) = 1:1:1 (volume ratio).

[0183] cathode for lithium secondary batteries lithium secondary battery Example 1 Example 7 Example 2 Example 8 Example 3 Example 9 Example 4 Example 10 Example 5 Example 11 Example 6 Example 12 Comparative Example 1 Comparative Example 5 Comparative Example 2 Comparative Example 6 Comparative Example 3 Comparative Example 7 Comparative Example 4 Comparative Example 8

[0186] Experimental Example.

[0187] To evaluate the performance of the cathode for a lithium secondary battery according to the present invention, the following experiment was performed.

[0189] a) Evaluation of electrode sheet resistance

[0190] The sheet resistance of the electrodes was measured using a 4-point probe method for the anodes prepared in Examples 1 to 6 and Comparative Examples 1 to 4, and the results are shown in Table 3 and Figure 1 below.

[0192] b) Evaluation of the amount of degassed oxygen gas during charging and discharging

[0193] For the lithium secondary batteries prepared in Examples 7 to 12 and Comparative Examples 5 to 8, initial charging (formation) was performed at 55°C under conditions of 3.5V and 1.0C, and the gas generated from the cathode during the initial charging was degassed to analyze the oxygen gas content generated during the initial charging. Then, 50 charge-discharge cycles were repeated at 45°C under conditions of 0.3C, and the oxygen gas content during each charge-discharge was further analyzed. The analyzed results are shown in Table 3 below.

[0195] c) Evaluation of charge / discharge capacity and retention rate

[0196] For the lithium secondary batteries prepared in Examples 7 to 12 and Comparative Examples 5 to 8, charging was performed at a temperature of 25°C with a charging current of 0.1C to a charging cutoff voltage of 4.2 to 4.25 V, and then activated by charging until the current density at the cutoff voltage became 0.01C. Afterward, the batteries were discharged with a discharge current of 0.1C to a cutoff voltage of 2 V, and the initial charge / discharge capacity per unit mass was measured.

[0197] Then, the capacity during charge and discharge was measured while repeating 50 charge-discharge cycles at 45°C under 0.3°C conditions, and the charge-discharge capacity retention rate was calculated after 50 charge-discharge cycles. The results are shown in Table 3 below.

[0198] Electrode sheet resistance Oxygen gas production [ml / g] Initial charge / discharge capacity [Ah] Capacity retention rate Measured value [Ω / sq.] R12 / R1 R12 / R2 1 charge / discharge cycle 50 charge / discharge cycles Example 7 2.0±0.2 0.89 0.36 86 12 103.2 92.5% Example 8 2.25±0.02 - - 91 19 102.8 91.9% Example 9 2.3±0.05 1.02 0.42 96 18 102.3 91.2% Example 10 1.9±0.05 0.84 0.35 95 26 102.8 90.9% Example 11 2.1±0.05 0.93 0.38 101 68 98.0 86.1% Example 12 2.1±0.05 0.93 0.38 107 78 98.2 85.7% Comparative Example 5 21.3±0.5 - - 89 13 94.7 85.6% Comparative Example 6 5.5±0.5 - - 97 15 101.8 89.9% Comparative Example 7 2.9±0.1 1.24 0.53 111 75 100.4 89.2% Comparative Example 8 2.8±0.1 1.24 0.51 95 21 100.1 89.6%

[0200] Referring to Table 3 and Figure 1 above, the positive electrode for a lithium secondary battery of an embodiment manufactured according to the present invention was found to have a low sheet resistance of 2.5 Ω / sq. or less, even though it contains a positive electrode additive represented by Formula 1, which has low electrical conductivity, and contains a first conductive material with a linear structure in the positive electrode composite layer. It can be seen that it exhibits a lower sheet resistance compared to cases where the first conductive material or a second conductive material without a linear structure is contained alone. Furthermore, the lithium secondary battery of the embodiment containing this not only has a high initial charge / discharge capacity of 102 Ah or more, but also exhibits a high capacity retention rate of 91% or more. Moreover, it was confirmed that the lithium secondary battery has high safety, as the amount of oxygen gas generated after the initial charge / discharge is significantly reduced.

[0201] From these results, it can be seen that the positive electrode for a lithium secondary battery according to the present invention is manufactured using a linear dispersion containing a positive electrode additive represented by Formula 1 and a linearly structured conductive material in a positive electrode composite layer which is an irreversible additive, and by adjusting the electrode sheet resistance to satisfy a specific range, the amount of oxygen gas generated during charging and discharging can be reduced and the charging and discharging efficiency of the lithium secondary battery can be easily improved.

[0203] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art or those with ordinary knowledge in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and technical scope of the invention as described in the claims set forth below.

[0204] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

Claim 1 A positive current collector, and a positive composite layer positioned on the positive current collector and comprising a positive active material, a positive 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 a positive electrode for a lithium secondary battery having a sheet resistance of 2.6 Ω / sq. or less: [Chemical Formula 1]Li p Co (1-q) M 1 q In the above chemical formula 1, O4, 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. Claim 2 A positive electrode for a lithium secondary battery according to claim 1, wherein the positive electrode composite layer further comprises a second conductive material, and the second conductive material comprises 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. Claim 3 In paragraph 2, the electrode sheet resistance (R12) of the anode containing a first conductive material and a second conductive material in the anode composite layer has a ratio (R12 / R1) of 0.5 to 1.2 with the electrode sheet resistance (R1) of the anode containing only the first conductive material in the anode composite layer, or a ratio (R12 / R2) of 0.1 to 0.8 with the electrode sheet resistance (R2) of the anode containing only the second conductive material in the anode composite layer. Claim 4 In claim 2, the electrode sheet resistance (R12) of the anode containing a first conductive material and a second conductive material in the anode composite layer has a ratio (R12 / R1) of 0.7 to 1.0 with respect to the electrode sheet resistance (R1) of the anode containing only the first conductive material in the anode composite layer, or has a ratio (R12 / R2) of 0.2 to 0.6 with respect to the electrode sheet resistance (R2) of the anode containing only the second conductive material in the anode composite layer. Claim 5 In claim 1, the anode additive is a positive electrode for a lithium secondary battery having a tetragonal structure with a space group of P42 / nmc. Claim 6 A lithium secondary battery cathode according to claim 1, wherein the content of the cathode additive is 0.1 to 10 parts by weight per 100 parts by weight of the cathode composite layer. Claim 7 A positive electrode for a lithium secondary battery according to claim 1, wherein the content of the first conductive material is 0.1 to 10 parts by weight per 100 parts by weight of the positive electrode composite layer. Claim 8 A positive electrode for a lithium secondary battery according to paragraph 2, wherein the total content of the first conductive material and the second conductive material is 0.1 to 10 parts by weight per 100 parts by weight of the positive electrode composite layer. Claim 9 In paragraph 2, the second conductive material is a positive electrode for a lithium secondary battery comprising 20 to 60 parts by weight per 100 parts by weight of the first conductive material. Claim 10 In claim 1, the cathode for a lithium secondary battery is a lithium metal composite oxide represented by the following chemical formula 2, wherein the cathode 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 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, and x, y, z, w, v, and u are 1.0≤x≤1.30, 0.1≤y<0.95, and 0.01, respectively. <z≤0.5, 0.01<w≤0.5, 0≤v≤0.2, 1.5≤u≤4.5이다. Claim 11 A method for manufacturing a cathode for a lithium secondary battery comprising: a cathode additive represented by the following chemical formula 1; a step of preparing a pre-dispersion solution by mixing a first conductive material and a binder; a step of preparing a cathode slurry by mixing the prepared pre-dispersion solution, a cathode active material, and a binder; and a step of preparing a cathode composite layer by applying the cathode slurry onto a cathode current collector; 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 wherein the sheet resistance of the manufactured cathode is 2.6 Ω / sq. or less: [Chemical Formula 1]Li p Co (1-q) M 1 q In the above chemical formula 1, O4, 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. Claim 12 In claim 11, the step of preparing the pre-dispersion solution is performed under conditions of 10% or less relative humidity, in a method for manufacturing a positive electrode for a lithium secondary battery. Claim 13 In claim 11, the step of manufacturing the anode slurry is a method for manufacturing a cathode for a lithium secondary battery, further mixing a second conductive material. Claim 14 A lithium secondary battery comprising a positive electrode according to claim 1; a negative electrode; and a separator located between the positive electrode and the negative electrode.

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