Negative electrode for lithium secondary battery and lithium secondary battery containing the same

Abstract

The present invention relates to a negative electrode for a lithium secondary battery in which lithium precipitation is suppressed, and a lithium secondary battery including the same. The negative electrode has an excellent effect of suppressing lithium precipitation at an end of the negative electrode active layer during charging and discharging of the secondary battery by realizing high orientation of a carbon-based active material contained in a first region of the negative electrode active layer, and thus has the advantage that a lithium secondary battery including the same has high safety and can be charged and discharged for a long time under high rate conditions.

Description

[Technical Field]

[0001] This application claims priority rights under Korean Patent Application No. 10-2022-0116896 dated September 16, 2022, and Korean Patent Application No. 10-2023-0062320 dated May 15, 2023, and all content disclosed in the documents of said Korean Patent Applications is incorporated herein by reference.

[0002] This invention relates to a negative electrode for a lithium secondary battery in which lithium deposition is suppressed during charging and discharging, and to a lithium secondary battery containing the same. [Background technology]

[0003] In recent years, secondary batteries have been widely applied not only to small devices such as portable electronic devices, but also to medium- and large-scale devices such as battery packs for hybrid and electric vehicles, or power storage devices.

[0004] Such a secondary battery is a power generation element capable of charging and discharging, consisting of a stacked structure of a positive electrode / separating membrane / negative electrode. Generally, the positive electrode contains lithium metal oxide as the positive electrode active material, and the negative electrode contains a carbon-based negative electrode active material such as graphite. During charging, lithium ions released from the positive electrode are absorbed into the carbon-based negative electrode active material of the negative electrode, and during discharging, lithium ions contained in the carbon-based negative electrode active material are absorbed into the lithium metal oxide of the positive electrode, resulting in a configuration in which charging and discharging are repeated.

[0005] One of the factors that influences the performance of a secondary battery is the capacity ratio of the active material contained in the positive electrode and the negative electrode, respectively. This capacity ratio can be expressed as the N / P ratio. The N / P ratio is the value obtained by dividing the total capacity of the negative electrode, which is calculated considering the capacity per unit area of ​​the negative electrode, by the total capacity of the positive electrode, which is obtained considering the capacity per unit area of ​​the positive electrode. Since this has a significant impact on the safety and capacity of the battery, it is generally adjusted to have a value of 1 or greater.

[0006] In this regard, in recent years, as a way to increase the energy density of secondary batteries, there has been a trend to reduce the weight and / or thickness of components that do not generate capacity at the electrodes, such as electrode tabs, casing materials, separator membranes, and current collectors, and to increase the weight and / or thickness of components that do generate capacity, such as the electrode active layer. Such changes have the effect of increasing the oxidation-reduction reaction rate at the electrode tabs, where electron movement is smoother during battery charging and discharging.

[0007] However, this acceleration of oxidation-reduction reactions accelerates degradation near the negative electrode tab, and this accelerated degradation near the negative electrode tab induces increased resistance, leading to a decrease in capacity in the region adjacent to the negative electrode tab. In other words, a reversal phenomenon occurs in the region adjacent to the negative electrode tab, where the N / P ratio becomes less than 1. When the N / P ratio becomes less than 1 in this way, lithium ions are not all intercalated into the negative electrode active material during battery charging, and instead are deposited on the negative electrode surface, forming dendrites. The likelihood of these dendrites forming increases significantly, especially when lithium secondary batteries are used for long periods under high-rate conditions. Since these dendrites can induce internal short circuits in the battery, they can act as a factor that impairs battery safety. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Korean Published Patent Publication No. 10-2015-0028457 [Patent Document 2] Korean Published Patent Publication No. 10-2016-0125720 [Overview of the project] [Problems that the invention aims to solve]

[0009] The object of the present invention is to provide a negative electrode for a lithium secondary battery and a lithium secondary battery containing the same, in which lithium deposition is suppressed at the edges of the negative electrode composite layer even when the lithium secondary battery is used for a long time under high-rate conditions. [Means for solving the problem]

[0010] In order to solve the above-mentioned problems, In one embodiment, the present invention is described as follows: The negative electrode current collector includes a negative electrode active layer provided on at least one surface and containing a carbon-based negative electrode active material, and a negative electrode tab that is drawn out to one side of the negative electrode active layer and provided on a plain portion of the negative electrode current collector that does not contain the negative electrode active layer. The negative electrode active layer is provided with a cross-sectional structure in the thickness direction on which a negative electrode tab is provided on one side, having the same length ratio to the total length, and is divided into a first region to the nth region (where 2 ≤ n ≤ 10) which are sequentially arranged from the first side portion from which the negative electrode tab is drawn out to the second side portion opposite it, and the degree of alignment of the carbon-based negative electrode active material represented by the following formula 1 increases as it progresses from the first region to the nth region.

[0011]

number

[0012]

number

[0013]

number

[0014] In equations 1 to 3, S 60 / 0 This is the peak intensity ratio (I0) when the incident angle of the X-ray is 0° during near-end X-ray absorption fine structure (NEXAFS) spectroscopy. B / A The peak intensity ratio (I60) when the incident angle of X-rays to ) is 60° B / A This represents the value of ), I60A represents the intensity of the peak with the highest intensity among the peaks existing at 286 ± 1.0 eV when the incident angle of X-rays is 60°, I60 B represents the intensity of the peak with the highest intensity among the peaks existing at 292.5 ± 1.0 eV when the incident angle of X-rays is 60°, I0 A represents the intensity of the peak with the highest intensity among the peaks existing at 286 ± 1.0 eV when the incident angle of X-rays is 0°, I0 B represents the intensity of the peak with the highest intensity among the peaks existing at 292.5 ± 1.0 eV when the incident angle of X-rays is 0°.

[0015] At this time, the first region of the negative electrode active layer has an alignment degree (S 60 / 0 ) of the carbon-based negative electrode active material represented by Formula 1 that can be 0.01 to 1.0.

[0016] In addition, the alignment degree of the carbon-based negative electrode active material according to the following Formula 4 in the negative electrode active layer can increase as it progresses from the first region to the nth region.

[0017] [Formula 4] O.I = I 004 / I 110

[0018] In Formula 4, I 004 represents the area of the peak indicating the (0, 0, 4) crystal plane during X-ray diffraction (XRD) spectroscopic analysis of the negative electrode active layer, I 110 represents the area of the peak indicating the (1, 1, 0) crystal plane during X-ray diffraction (XRD) spectroscopic analysis of the negative electrode active layer.

[0019] In addition, the carbon-based negative electrode active material contained in the nth region has an alignment degree (O.I nth ) that can be 110% to 300% of the alignment degree (O.I 1st ) of the carbon-based negative electrode active material contained in the first region.

[0020] Furthermore, the first region of the negative electrode active layer is the average alignment of the carbon-based negative electrode active material according to Equation 4 (OI 1st ) can be between 0.1 and 0.6.

[0021] Furthermore, the above-mentioned negative electrode active layer has a degree of alignment (S) of the carbon-based negative electrode active material according to the above formula 1. 60 / 0 ) and / or the degree of alignment (OI) of the carbon-based anode active material according to the above formula 4 may have a gradient that increases as one progresses from the first region to the nth region, or may show a tendency to increase in a stepwise manner at predetermined intervals.

[0022] Furthermore, the first region of the negative electrode active layer is defined by the ratio (I) of the intensity of the peak representing the (0,0,4) crystal plane and the intensity of the peak representing the (0,0,2) crystal plane during X-ray diffraction (XRD) spectroscopy analysis. 004 / I 002 ) may be 0.04 or higher.

[0023] On the other hand, the carbon-based anode active material may contain one or more of natural graphite and artificial graphite, in which case the carbon-based anode active material may have a degree of spheroidization of 0.75 or higher.

[0024] Furthermore, in one embodiment of the present invention, The present invention provides a lithium secondary battery comprising an electrode assembly including a positive electrode, a negative electrode according to the present invention as described above, and a separator membrane disposed between the positive electrode and the negative electrode.

[0025] In this case, the positive electrode may include a positive electrode tab that is provided on at least one surface of the positive electrode current collector and includes a positive electrode active layer containing one or more positive electrode active materials from among lithium metal oxides represented by the following chemical formulas 1 and 2.

[0026] [Chemical formula 1] Li x [Ni y Co z Mn w M 1 v ]O2

[0027] [Chemical formula 2] LiM2 p Mn 1-p O4

[0028] In the above chemical formulas 1 and 2, M 1 It is one or more elements from 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, and v are such that 1.0 ≤ x ≤ 1.30, 0.5 ≤ y < 1, and 0 respectively. <z≦0.3、0<w≦0.3、0≦v≦0.1であり、かつy+z+w+v=1であり、 M 2 It is Ni, Co, or Fe, p is 0.05 ≤ p ≤ 1.0.

[0029] Specifically, the above positive electrode active material is LiNi 0.8 Co 0.1 Mn 0.1 O2, LiLiLi 0.6 Co 0.2 Mn 0.2 O2, LiLiLi 0.9 Co 0.05 Mn 0.05 O2, LiLiLi 0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiLiLi 0.6 Co 0.2 Mn 0.15 Al 0.05 O 2、 LiRing 0.7 Co 0.1 Mn 0.1 Al 0.1 O2, LiLiLi 0.7 Mn 1.3 O4, LiSa 0.5 Mn 1.5 O4, LiSa 0.3 Mn 1.7 O4, LiFePO4, LiFe 0.8 Mn 0.2 PO4 and LiFe 0.5 Mn 0.5 It may contain one or more of the PO4 types.

[0030] Furthermore, the electrode assembly may be a stacked electrode assembly, a zigzag electrode assembly, or a zigzag-stacked electrode assembly. [Effects of the Invention]

[0031] The negative electrode for lithium secondary batteries according to the present invention has a degree of alignment (S) of the carbon-based negative electrode active material contained near the negative electrode tab where the degree of degeneration of the negative electrode active layer is relatively high. 60 / 0 By reducing the OI (and / or OI) and thereby lowering electrode resistance, secondary batteries not only exhibit high efficiency during charging and discharging, especially during long-term charging and discharging under high-rate conditions, but also have the advantage of superior battery safety because they effectively suppress lithium deposition at the edges of the negative electrode active layer. [Brief explanation of the drawing]

[0032] [Figure 1] This image shows the structure of a negative electrode manufactured according to one embodiment of the present invention, where (a) is a cross-sectional view of the negative electrode, (b) is a plan view of the negative electrode, and (c) is a plan view showing the position of the negative electrode in the negative electrode slurry state during manufacturing. [Figure 2] This image shows the alignment of the ab-axis crystal planes of graphite when a magnetic field is applied to the negative electrode slurry during negative electrode active layer formation. (a) shows the case where no magnetic field is applied and the graphite crystal planes are not aligned, and (b) shows the case where a magnetic field is applied and the graphite crystal planes are aligned. [Figure 3] This image shows the trend of absorption peaks by type and position of each orbital depending on the incident angle of X-rays during near-end X-ray absorption fine structure (NEXAFS) spectroscopy. (a) shows the type and position of the orbitals forming the double bond in graphite, and (b) shows the positional peak morphology of each orbital when X-rays are incident. [Figure 4] This image shows the incident X-ray angle during near-end X-ray absorption fine structure (NEXAFS) spectroscopy analysis of a negative electrode manufactured according to one embodiment of the present invention. [Modes for carrying out the invention]

[0033] Since the present invention can be modified in various ways and may have a variety of embodiments, specific embodiments will be described in detail.

[0034] However, this is not intended to limit the present invention to any particular embodiment, but rather should be understood to include all modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

[0035] In the present invention, terms such as "includes" and "have" are intended to specify the presence of features, numbers, stages, operations, components, parts, or combinations thereof as described in the specification, and do not preemptively exclude the presence or possibility of adding one or more other features, numbers, stages, operations, components, parts, or combinations thereof.

[0036] Furthermore, in this invention, when a part such as a layer, film, region, or plate is described as being "on top" of another part, this includes not only the case where it is "directly on top" of the other part, but also the case where another part is located in between. Conversely, when a part such as a layer, film, region, or plate is described as being "below" another part, this includes not only the case where it is "directly below" the other part, but also the case where another part is located in between. Also, in this application, being "on top" may include being located not only at the top but also at the bottom.

[0037] Furthermore, in the present invention, "contains as a main component" may mean that the defined component is contained in an amount of 50% by weight or more (or 50% by volume or more), 60% by weight or more (or 60% by volume or more), 70% by weight or more (or 70% by volume or more), 80% by weight or more (or 80% by volume or more), 90% by weight or more (or 90% by volume or more), or 95% by weight or more (or 95% by volume or more) of the total weight (or total volume). For example, "contains graphite as a main component as the negative electrode active material" may mean that graphite is contained in an amount of 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, or 95% by weight or more of the total weight of the negative electrode active material, and in some cases it may also mean that the entire negative electrode active material consists of graphite and contains 100% by weight of graphite.

[0038] Furthermore, in the present invention, "cross-sectional structure" means the structure of a surface cut in the thickness direction of the negative electrode active layer, or the structure of a surface cut perpendicularly with respect to the surface of the negative electrode active layer. In this case, the cut surface may be the same as a surface cut perpendicular to the process direction during negative electrode active layer formation, or a surface cut in the width direction of the negative electrode slurry applied to form the negative electrode active layer. Moreover, the above cross-sectional structure may mean the structure of a surface cut in the thickness direction of the negative electrode active layer, and a structure cut in a direction progressing from one surface where the negative electrode tab is formed to the opposite surface.

[0039] Furthermore, in this specification, "the carbon-based anode active material is oriented" or "the carbon-based anode active material is aligned" may mean that, as shown in Figure 2(b), a specific crystal plane (for example, the ab-axis crystal plane of graphite) that shows the two-dimensional planar structure of the carbon-based anode active material constituting the anode active material particles is arranged to have a predetermined inclination with respect to the surface of the anode current collector. This may differ from, as shown in Figure 2(a), where the particles of the carbon-based anode active material themselves are aligned in a predetermined direction only within the anode active layer, but have no directionality with respect to the anode current collector.

[0040] Furthermore, "high orientation of carbon-based anode active material" may mean that a specific crystal plane (for example, the ab-axis crystal plane of graphite) exhibiting the two-dimensional planar structure of the carbon-based anode active material contained in the anode active layer has a high frequency of having a predetermined inclination with respect to the surface of the anode current collector. In some cases, it may also mean that the above crystal planes of the carbon-based anode active material contained in the anode active layer are aligned at a high angle (for example, an angle close to perpendicular, greater than 45°, specifically 60° or more) with respect to the surface of the anode current collector.

[0041] Furthermore, "high degree of alignment of carbon-based negative electrode active material" refers to the "degree of alignment (S)" as mentioned in this specification. 60 / 0 A large value of "and / or OI)" may mean that specific crystal planes (e.g., the ab-axis crystal plane of graphite) that show the two-dimensional planar structure of the carbon-based anode active material contained in the anode active layer are aligned at a low angle (e.g., less than 45°) with respect to the surface of the anode current collector. Conversely, "low alignment of the carbon-based anode active material" means that "alignment (S)" is large. 60 / 0 The value of "and / or OI)" is small, which may mean that the above crystal planes of the carbon-based anode active material contained in the anode active layer are aligned at a high angle (for example, an angle close to perpendicular, 45° or more, specifically 60° or more) with respect to the surface of the anode current collector.

[0042] Furthermore, in this specification, "average particle size (D 50 "50%" refers to the particle size at which the cumulative value in the particle size distribution becomes 50%, and this is also called the median diameter.

[0043] The present invention will be described in more detail below.

[0044] <Negative electrode for lithium secondary batteries> In one embodiment, the present invention is described as follows: The negative electrode current collector includes a negative electrode active layer provided on at least one surface and containing a carbon-based negative electrode active material, and a negative electrode tab that is drawn out to one side of the negative electrode active layer and provided on a plain portion of the negative electrode current collector that does not contain the negative electrode active layer. The above-mentioned negative electrode active layer is provided with a thickness-direction cross-sectional structure in which a negative electrode tab is provided on one side, and has the same length ratio to the total length, and is divided into a first region to the nth region (where 2 ≤ n ≤ 10) which are sequentially arranged from the first side portion from which the negative electrode tab is drawn out to the second side portion opposite it, and provides a negative electrode for a lithium secondary battery in which the degree of alignment of the carbon-based negative electrode active material, represented by the following formula 1, increases as it progresses from the first region to the nth region.

[0045]

number

[0046] The negative electrode for a lithium secondary battery according to the present invention includes a negative electrode active layer containing a carbon-based negative electrode active material on at least one surface of the negative electrode current collector, and includes a negative electrode tab located at one end of the surface of the negative electrode current collector on which the negative electrode active layer is provided, and provided in a plain area where the negative electrode active layer is not provided.

[0047] In this context, the negative electrode active layer refers to the layer that embodies the electrical activity of the negative electrode. The negative electrode active layer contains a carbon-based negative electrode active material as the negative electrode active material in order to embody electrical activity through a reversible oxidation-reduction reaction during the charging and discharging of the battery. Specifically, the carbon-based negative electrode active material refers to a material whose main component is carbon atoms, and such a carbon-based negative electrode active material may include graphite. The graphite may include one or more of either natural graphite or artificial graphite. For example, the carbon-based negative electrode active material may contain natural graphite or artificial graphite alone, or in some cases, a mixture of natural graphite and artificial graphite. In this case, the mixing ratio of natural graphite and artificial graphite may be 5-40:60-95 or 10-30:70-90 based on weight. By including natural graphite and artificial graphite in the above-mentioned mixing ratio, the carbon-based anode active material can achieve strong adhesion between the anode current collector and the anode active layer while also exhibiting high orientation of the carbon-based anode active material to the surface of the anode current collector.

[0048] The carbon-based anode active material described above is preferably a spherical graphite granule formed by the aggregation of multiple flake-shaped graphite particles. Examples of flake-shaped graphite include natural graphite, artificial graphite, mesophase-calcined carbon (bulk mesophase) made from tar and pitch, and graphitized cokes (such as green coke, green coke, pitch coke, needle coke, and petroleum coke). In particular, a material assembled using multiple highly crystalline natural graphite particles is preferred. Furthermore, a single graphite granule can be formed by the aggregation of 2 to 100, preferably 3 to 20, flake-shaped graphite particles.

[0049] Such carbon-based negative electrode active materials, specifically graphite, may have a spherical particle morphology. In this case, the degree of sphericity of the graphite particles can be 0.75 or higher, and may be, for example, 0.75 to 1.0, 0.75 to 0.95, 0.8 to 0.95, or 0.90 to 0.99. Here, "degree of sphericity" can mean the ratio of the shortest diameter (minor axis) to the longest diameter (major axis) among any diameter passing through the center of the particle. A degree of sphericity of 1 means that the particle morphology is spherical. The above degree of sphericity can be determined by measuring it using a particle shape analyzer, or by measuring the particle shape using a scanning electron microscope (SEM) or energy-dispersive spectrometer and then analyzing the measured results. The present invention has the advantage of being able to achieve high electrical conductivity in the negative electrode active layer by realizing a shape close to spherical in the carbon-based negative electrode active material, thereby improving the capacity of the battery, and being able to increase the specific surface area per unit weight of the negative electrode active material, thereby improving the adhesion between the negative electrode active layer and the current collector.

[0050] Furthermore, the above carbon-based negative electrode active material has an average particle size (D) of 0.5 μm to 10 μm. 50 ) can be shown, specifically an average particle size (D) of 2μm~7μm, 0.5μm~5μm, or 1μm~3μm. 50 ) can be shown.

[0051] For carbon-based anode active materials that are close to spherical, a smaller average particle size may be advantageous in order to maximize the degree of disorder in the expansion direction for each particle, thereby preventing particle expansion due to lithium ion charging. However, if the particle size of the carbon-based anode active material is less than 0.5 μm, a large amount of binder is required due to the increase in the number of particles per unit volume, which may result in a low degree of spheroidization and spheroidization yield. On the other hand, if the maximum particle size exceeds 10 μm, the expansion rate of the anode active material during charging and discharging of the secondary battery increases significantly, and repeated charging and discharging can reduce interparticle bonding and bonding between the anode active material particles and the current collector, potentially leading to a significant decrease in cycle performance.

[0052] Furthermore, the above-mentioned negative electrode active layer can be manufactured by applying a negative electrode slurry containing a carbon-based negative electrode active material to at least one surface of a negative electrode current collector, and then drying and rolling it, in order to realize electrical activity through a reversible oxidation-reduction reaction during the charging and discharging of the secondary battery.

[0053] Figure 1 is a structural diagram showing the structure of the negative electrode according to the present invention, where (a) is a cross-sectional view of the negative electrode, (b) is a plan view of the negative electrode, and (c) is a plan view showing the position of the negative electrode in the negative electrode slurry state during negative electrode manufacturing.

[0054] Referring to Figure 1, the negative electrode according to the present invention includes a negative electrode active layer 120 formed on at least one surface of the negative electrode current collector 110. The negative electrode also includes a negative electrode tab 111, which is electrically connected to the negative electrode terminal, at one end of the negative electrode current collector 110 on which the negative electrode active layer 120 is provided. The negative electrode tab 111 is provided on a plain area that does not include the negative electrode active layer 120 on its surface, so that it can be electrically connected to the negative electrode tabs and / or the negative electrode terminals of other adjacent negative electrodes when assembling electrodes for secondary battery manufacturing.

[0055] Here, the negative electrode active layer 120 includes, as shown in Figures 1(a) and 1(b), a first side portion S1 of the negative electrode active layer from which the negative electrode tab 111 is drawn out relative to the surface, a second side portion S2 positioned opposite to the first side portion and on the other side of the first side portion, and a third side portion S3 and a fourth side portion S4 that are connected to the first side portion S1 and the second side portion S2 to form a single surface. Here, the second to fourth side portions S2 to S4 may be slit (S / F) after drying of the negative electrode slurry 120' during negative electrode manufacturing, as shown in Figure 1(c), and their ends may have the shape of a cut surface, but are not limited to this.

[0056] Furthermore, the negative electrode active layer 120 is divided into multiple regions, and the carbon-based negative electrode active material contained in these regions may have different inclinations of the ab-axis crystal plane of the carbon-based negative electrode active material with respect to the surface of the negative electrode current collector. Specifically, the negative electrode active layer 120 is defined as shown in Figure 1(a), with respect to the total length L, based on a cross-sectional structure in the thickness direction in which a negative electrode tab 111 is provided on one side, and has the same length ratio (L1=L2=...=L) n-1 =L n The negative electrode active layer 120 has a first region (121-1) to the nth region (121-n, where 2≦n≦10), which are sequentially arranged from the first side surface S1 from which the negative electrode tab 111 is drawn out to the second side surface S2 opposite to it. For example, if the negative electrode active layer 120 contains three regions (n=3), the first region 121-1, the second region 121-2, and the third region 121-3 are sequentially arranged from the first side surface S1 from which the negative electrode tab 111 is drawn out to the second side surface S2 opposite to it, and the length of each region may be the same (L1=L2=L3).

[0057] The present invention makes it possible to control the deviation between the alignment of carbon-based negative electrode active material contained in any region and the alignment of carbon-based negative electrode active material contained in adjacent regions by dividing the negative electrode active layer 120 into multiple regions having the same length ratio. If the deviation in the alignment of carbon-based negative electrode active material in any region is larger than that of adjacent regions, it means that the tilt of the ab-axis crystal plane of the carbon-based negative electrode active material with respect to the surface of the negative electrode current collector is large. Such a negative electrode has low electrolyte impregnation, and the mobility of lithium ions during high-rate charge and discharge decreases, which can reduce the electrical properties of the negative electrode. Therefore, the present invention makes it possible to control the deviation in the alignment of carbon-based negative electrode active material between each region by dividing the negative electrode active layer into multiple regions having the same length ratio.

[0058] For this reason, the above-mentioned negative electrode active layer can be divided into 2 to 10 regions (2 ≤ n ≤ 10), specifically into 3 to 10 regions (3 ≤ n ≤ 10), 5 to 10 regions (5 ≤ n ≤ 10), 7 to 10 regions (7 ≤ n ≤ 10), 2 to 8 regions (2 ≤ n ≤ 8), 2 to 6 regions (2 ≤ n ≤ 6), or 2 to 4 regions (2 ≤ n ≤ 4).

[0059] Furthermore, the present invention can suppress lithium deposition at the edges of the negative electrode composite layer even when a lithium secondary battery is used for a long time under high-rate conditions, by controlling the alignment of the carbon-based negative electrode active material contained in the negative electrode active layer for each region. Specifically, in the negative electrode active layer according to the present invention, as you proceed from the first side portion S1 from which the negative electrode tab is drawn out to the second side portion S2 on the other side, that is, as you proceed from the first region 121-1 to the nth region 121-n, the degree of alignment (S) of the carbon-based negative electrode active material contained in the negative electrode active layer is controlled. 60 / 0 And / or OI) may increase.

[0060] Generally, in electrode tabs where electron movement is smooth during battery charging and discharging, oxidation-reduction reactions are accelerated, and the reaction rate tends to increase. This acceleration of oxidation-reduction reactions accelerates degradation near the negative electrode tab, which in turn induces an increase in electrical resistance, leading to a decrease in capacity in the region adjacent to the negative electrode tab. As a result, a reversal phenomenon occurs in the region of the negative electrode active layer adjacent to the negative electrode tab, where the N / P ratio becomes less than 1. When the N / P ratio becomes less than 1 in this way, lithium is deposited on the negative electrode surface, forming dendrites. The likelihood of these dendrites forming increases significantly, especially when lithium secondary batteries are used for long periods under high-rate conditions. Since these dendrites can induce internal short circuits in the battery, they can act as a factor that impairs battery safety.

[0061] However, the present invention controls the inclination of the ab-axis crystal plane of the carbon-based negative electrode active material with respect to the negative electrode current collector surface to increase as it becomes more adjacent to the first side surface of the negative electrode active layer provided on the side from which the negative electrode tab is drawn. This reduces the electrical resistance of the region adjacent to the negative electrode tab in the negative electrode active layer, thereby preventing lithium from being deposited in a dendritic manner on the negative electrode surface during charging and discharging. Specifically, the negative electrode active layer can be configured such that the ab-axis crystal plane of the carbon-based negative electrode active material contained in the first side surface from which the negative electrode tab is drawn, more specifically in the first region most adjacent to the negative electrode tab, is aligned nearly perpendicular to the negative electrode current collector. Furthermore, as the negative electrode active layer progresses from the first region to the nth region (where 2 ≤ n ≤ 10), the separation distance from the negative electrode tab increases, and as the separation distance from the negative electrode tab increases, the inclination of the ab-axis crystal plane of the carbon-based negative electrode active material contained in each region tends to decrease. This reduction in the tilt of the ab-axis crystal plane of the carbon-based anode active material (i.e., the degree of alignment of the carbon-based anode active material (S) 60 / 0 The increase in OI (and / or OI) may show a stepwise decreasing trend (or increasing orderliness) or a decreasing gradient (or increasing gradient) as we progress from the first region to the nth region (where 2 ≤ n ≤ 10).

[0062] Here, "the carbon-based negative electrode active material is aligned nearly perpendicular to the negative electrode current collector" can mean that the crystal planes of the carbon-based negative electrode active material constituting the spherical particles, specifically the ab-axis crystal planes representing the planar direction of graphite with a two-dimensional structure, are arranged at an inclination nearly perpendicular to the surface of the negative electrode current collector. In this case, the planar direction of the graphite (i.e., the ab-axis crystal plane direction) may have an average inclination of 60° to 120° with respect to the negative electrode current collector, preferably 70° to 110°, or 80° to 100°.

[0063] Furthermore, the alignment of the carbon-based anode active material can be applied without particular limitations as long as it is done by a method commonly used in the industry. Specifically, after applying a anode slurry containing the carbon-based anode active material to the surface of the anode current collector, a magnetic field can be applied to the surface of the anode slurry at the top and bottom of the anode slurry, and the magnetic field strength and / or application time can be reduced as the position of the anode active layer changes from the first region to the nth region (where 2 ≤ n ≤ 10). This can induce an increase in the degree of alignment of the carbon-based anode active material as one progresses from the first region to the nth region.

[0064] As one example, when the negative electrode active layer is divided into a total of three regions (n=3) from the first side surface where the negative electrode tab is drawn out to the second side surface, the magnetic field strength can be applied to the negative electrode slurry surface corresponding to the first, second, and third regions at 2.0T, 1.0T, and 0.5T, respectively, so that the magnetic field strength decreases in a stepwise manner during the manufacturing of the negative electrode active layer. In this case, the degree of alignment of the carbon-based negative electrode active material (S 60 / 0 And / or OI) can be realized in the order of 1st region < 2nd region < 3rd region.

[0065] As another example, if the negative electrode active layer is divided into a total of 5 regions (n=5) from the first side surface where the negative electrode tab is drawn out to the second side surface, a magnetic field can be applied from 2.0T to 0.5T during the manufacturing of the negative electrode active layer so that there is a magnetic field strength gradient on the surface of the negative electrode slurry corresponding to the first to fifth regions. In this case, the degree of alignment of the carbon-based negative electrode active material (S 60 / 0The and / or OI) can embody the alignment gradient in the order of 1st region < 2nd region < 3rd region < 4th region < 5th region.

[0066] In the present invention, the magnetic field applied to the negative electrode slurry can be performed at an intensity of 0.5T to 2.0T for 1 to 60 seconds, specifically at an intensity of 0.5T to 1.0T, 0.5T to 1.5T, 1.0T to 2.0T, 0.8T to 1.5T, or 0.8T to 1.2T for 1 to 30 seconds, or 1 to 20 seconds. By controlling the intensity and duration of the magnetic field applied to the negative electrode slurry as described above, the degree of alignment (S) of each region of the carbon-based negative electrode active material can be controlled. 60 / 0 The difference between and / or OI can be suitably realized. This prevents an increase in electrical resistance in the region adjacent to the negative electrode tab during charging and discharging, and prevents the N / P ratio from being reversed.

[0067] Furthermore, the magnetic field strength can be applied in such a way that the magnetic field strength deviation between any region of the negative electrode slurry and adjacent regions does not become large. For example, the magnetic field strength applied to any region may have a deviation of 0.01T to 0.5T from the magnetic field strength applied to adjacent regions, specifically, a deviation of 0.01T to 0.3T, 0.01T to 0.1T, 0.1T to 0.5T, or 0.2T to 0.3T. The applied magnetic field strength affects the alignment of the carbon-based negative electrode active material. Therefore, if the magnetic field strength deviation between any region and adjacent regions becomes large, the alignment deviation of the carbon-based negative electrode active material contained in them may also become large. At points where the alignment deviation of the carbon-based negative electrode active material is large, the impregnation of the electrolyte becomes low, and the mobility of lithium ions during high-rate charging and discharging may decrease. Therefore, this problem can be overcome by controlling the magnetic field strength deviation applied between any region and adjacent regions when a magnetic field is applied to the negative electrode slurry to be small.

[0068] On the other hand, the degree of alignment of the carbon-based anode active material contained in the anode active layer can be determined by molecular orientation and / or crystal structure analysis of the carbon-based anode active material.

[0069] As one example, in the negative electrode active layer, the carbon-based negative electrode active material is aligned nearly perpendicularly to the negative electrode current collector, and during near-edge X-ray absorption fine structure (NEXAFS) spectroscopy analysis, the value related to Equation 1 below may increase as the measurement position changes from the first region to the nth region (where 2 ≤ n ≤ 10).

[0070]

number

[0071] (In formula 1 above, S 60 / 0 This is the peak intensity ratio (I0) when the X-ray incident angle is 0° during near-end X-ray absorption fine structure (NEXAFS) spectroscopy. B / A The peak intensity ratio (I60) when the incident angle of X-rays to ) is 60° B / A Represents the value of ( ).

[0072] Near-edge X-ray absorption fine structure (NEXAFS) spectroscopy, unlike X-ray photoelectron spectroscopy (XPS) which measures the bond energy between atoms constituting a compound, can only reflect the local structure near carbon atoms, including excited core electrons, and the surface structure of the measured carbon-based anode active material particles. Therefore, the present invention uses the spectrum obtained by NEXAFS spectroscopy of the anode active layer to determine the degree of alignment (S) of the carbon-based anode active material contained in the anode active layer. 60 / 0 ) can be measured.

[0073] Specifically, when X-rays are irradiated onto the carbon atoms (C) of a carbon-based negative electrode active material, occupied electrons (K-shell electrons) in the inner-shell energy levels (1s orbitals) of the carbon atoms absorb X-ray energy and are excited to various unoccupied molecular orbitals. NEXAFS spectroscopy uses the absorption spectrum observed at this time.

[0074] In this context, the above-mentioned empty molecular orbitals include, in the case of graphite, a carbon-based anode active material, i) the π* orbital, which is attributed to the antibonding orbital of sp2 bonds that reflects the crystallinity of graphite (such as the basal plane and orientation); ii) the σ* orbital, which is attributed to the antibonding orbital of sp3 bonds that reflects the disorder of crystallinity (such as edge planes and non-orientation); and iii) the Rydberg orbital, which is attributed to the antibonding orbital of CH bonds and CO bonds.

[0075] Carbon-based anode active materials, such as graphite, have a crystalline structure in which carbon atoms are bonded in sp2 in a hexagonal network (see Figure 3(a)). The basal plane is the two-dimensional plane of the hexagonal network (ab-axis crystal plane), and the planes showing the ends of the hexagonal network (c-axis crystal plane) are the edge planes. At the edge planes of carbon-based anode active materials, there is a possibility of -COOH, -C=O, etc., being present at the terminal carbon atoms, so the proportion of sp3 bonds may be high. Therefore, to analyze the crystal plane orientation and / or alignment of carbon-based anode active materials, it is necessary to analyze the state of the sp2 orbitals of carbon atoms at each crystal plane of the carbon-based anode active material.

[0076] The above NEXAFS spectroscopic analysis can be performed by a total electron yield method, in which X-rays with a fixed incident angle relative to the negative electrode active layer are irradiated onto the negative electrode active layer, and the sample current flowing through the sample to complement the photoelectrons emitted from the surface of the negative electrode active layer is measured while scanning the energy of the irradiated X-rays from 280 eV to 320 eV. In this case, since the synchrotron radiation is linearly polarized X-rays with an applied magnetic field E, the intensity of the observed absorption peak may differ depending on the incident direction of the X-rays. Specifically, referring to Figure 3(a), in the case of graphite, which is a carbon-based negative electrode active material, it has a hexagonal network structure via sp2 bonds (-C=C-) of carbon atoms, and these sp2 bonds include σ orbitals located parallel to the sp2 bond and π orbitals located perpendicular to the sp2 bond. Here, the σ and π orbitals have a symmetrical structure with nodes at the nucleus position of the carbon atom, respectively, with respect to the antibonding σ* and π* orbitals. Therefore, the σ* and π* orbitals have the same orientation as the σ and π orbitals.

[0077] Therefore, as shown in Figure 3(b), when the incident X-ray direction is parallel to the sp2 bond, the intensity of the absorption peak excited from the 1s level to the π* level of carbon increases, while conversely, when it is perpendicular to the sp2 bond, the intensity of the absorption peak decreases. On the other hand, when the incident X-ray direction is parallel to the sp2 bond, the intensity of the absorption peak excited from the 1s level to the σ* level of carbon decreases, while conversely, when it is perpendicular to the sp2 bond, the intensity of the absorption peak increases. Due to these characteristics, as shown in Figure 2(b), if the orientation of the graphite contained in the negative electrode active layer is high, the antibonding empty-level molecular orbitals of the graphite located on the surface of the negative electrode active layer are uniformly aligned. Therefore, when the incident X-ray angle to the negative electrode active layer is changed, the spectral shape changes significantly due to reinforcement and interference of emitted photoelectrons. In contrast, as shown in Figure 2(a), if the orientation of the graphite contained in the negative electrode active layer is low, the antibonding empty-level molecular orbitals of the graphite located on the surface of the negative electrode active layer are non-uniformly aligned, so the spectral shape hardly changes even if the angle of incidence of X-rays on the sample is changed.

[0078] Therefore, in order to measure the degree of orientation of the carbon-based anode active material contained in the anode active layer, the present invention performs NEXAFS spectroscopic analysis on the surface of the anode active layer and incident X-rays on the anode active layer at different incident angles (0° and 60°), and for each incident angle, the ratio of the intensity of the absorption peak (peak A = 287 ± 0.2 eV) attributed to the transition from the 1s level to the σ* level of carbon to the intensity of the absorption peak (peak B = 293 ± 0.2 eV) attributed to the transition from the 1s level to the π* level of carbon (I B / A After determining the ratio of intensity between the angles of incidence (60° and 0°), the ratio (S) 60 / 0 =I60 B / A / I0 B / A By calculating the orientation and / or alignment (S) of the carbon-based anode active material contained in the anode active layer, the orientation and / or alignment (S) of the anode active material is determined. 60 / 0 ) can be measured quantitatively.

[0079] That is, the degree of orientation of the carbon-based negative electrode active material contained in the first region is determined as follows: i) As expressed by Equation 2, the intensity (I60 A ) of the absorption peak (peak A = 287 ± 0.2 eV) attributed to the transition from the 1s level to the π* level of carbon measured at an X-ray incident angle of 60° is used to calculate the ratio (I60 B ) of the intensity of the absorption peak (peak B = 293 ± 0.2 eV) attributed to the transition from the 1s level to the σ* level of carbon. ii) As expressed by Equation 3, after calculating the ratio (I0 B / A ) of the intensity of the absorption peak (peak A = 287 ± 0.2 eV) attributed to the transition from the 1s level to the π* level of carbon measured at an X-ray incident angle of 0° to the intensity of the absorption peak (peak B = 293 ± 0.2 eV) attributed to the transition from the 1s level to the σ* level of carbon, iii) as expressed by Equation 1, the ratio (S 60 / 0 = I60 B / A / I0 B / A ) is obtained to evaluate the degree of orientation.

[0080]

Equation

[0081]

Equation

[0082] In Equations 2 and 3, I60 A represents the intensity of the peak with the strongest intensity among the peaks existing at 286 ± 1.0 eV when the X-ray incident angle is 60°. I60 B represents the intensity of the peak with the strongest intensity among the peaks existing at 292.5 ± 1.0 eV when the X-ray incident angle is 60°. I0 A represents the intensity of the peak with the strongest intensity among the peaks existing at 286 ± 1.0 eV when the X-ray incident angle is 0°. ​​​​​​I0 B represents the intensity of the peak with the highest intensity among the peaks existing at 292.5 ± 1.0 eV when the incident angle of X-rays is 0°.

[0083] Here, the above formula 1 (S 60 / 0 ) can mean that the closer it is to 1, the lower the orientation of the a-b axis crystal plane of graphite, which is a carbon-based negative electrode active material, with respect to the negative electrode current collector and the higher the degree of alignment (O.I); the closer it is to 0, the higher the orientation of the a-b axis crystal plane of graphite with respect to the negative electrode current collector and the lower the degree of alignment (O.I). The first region according to the present invention can satisfy that the average value of the value (S 60 / 0 ) according to formula 1 is 1.0 or less, more specifically 0.9 or less, 0.8 or less, 0.7 or less, 0.5 or less, 0.01 to 1.0, 0.05 to 0.7, 0.05 to 0.5, 0.05 to 0.4, 0.1 to 0.7, 0.3 to 0.7, or 0.5 to 0.8. Also, the above nth region can satisfy that the average value of the value (S 60 / 0 ) according to formula 1 exceeds 0.8, more specifically more than 0.9, 0.8 to 2.0, 0.9 to 1.5, 0.8 to 1.5, 0.8 to 1.3, or 0.85 to 1.2.

[0084] That the first region of the negative electrode active layer according to the present invention satisfies formula 1 (S 60 / 0 ) being 1 or less indicates that the a-b axis crystal plane of the carbon-based negative electrode active material contained in the above first region is aligned close to perpendicular to the negative electrode current collector as shown in (b) of FIG. 2. Therefore, the negative electrode including it can prevent an increase in electrical resistance in the region adjacent to the negative electrode tab during charge and discharge of the secondary battery and can prevent the N / P ratio (N / P ratio) from reversing.

[0085] Also, this has a different meaning from the carbon-based negative electrode active material particles satisfying formula 1 (S 60 / 0 ). The carbon-based negative electrode active material particles satisfying formula 1 (S 60 / 0Satisfying the condition ) to be 1 or less means that the ab-axis crystal planes of the molecular crystals making up the particles of the carbon-based anode active material are aligned with a predetermined direction within the particles. Therefore, including such a carbon-based anode active material in the anode active layer means that, unless further treatment is applied, the ab-axis crystal planes of the carbon-based anode active material will tend to be non-oriented with respect to the surface of the anode current collector as shown in Figure 2(a), thus differentiating it from the first region of the anode active layer according to the present invention.

[0086] As another example, in the first region of the negative electrode active layer, the ab-axis crystal planes of the carbon-based negative electrode active material are aligned nearly perpendicular to the negative electrode current collector, and the degree of alignment of the carbon-based negative electrode active material (OI) is expressed by the following formula 4 during X-ray diffraction (XRD) spectroscopy analysis. 1st The degree of alignment (OI) of carbon-based negative electrode active material contained in the nth region (where 2 ≤ n ≤ 10) nth It may be smaller than ), which can increase the alignment (OI) of the carbon-based anode active material as the position of the anode active layer changes from the first side to the second side.

[0087] [Formula 4] OI=I 004 / I 110

[0088] In Equation 4, I 004 This represents the area of ​​the peak indicating the (0,0,4) crystal plane during X-ray diffraction (XRD) spectroscopy analysis of the negative electrode active layer. I 110 This represents the area of ​​the peak indicating the (1,1,0) crystal plane during X-ray diffraction (XRD) spectroscopy analysis of the negative electrode active layer.

[0089] The crystal plane orientation of the carbon-based anode active material can be determined by crystal plane analysis of the carbon-based anode active material, such as X-ray diffraction spectroscopy. The degree of alignment (OI) of the carbon-based anode active material, expressed in Equation 4 above, can serve as an indicator of the direction in which the crystal structure of the carbon-based anode active material is aligned during X-ray diffraction measurement. Specifically, it indicates the degree to which the ab-axis crystal plane, which shows the two-dimensional planar structure of the carbon-based anode active material, is aligned with respect to the surface of the anode current collector. For example, when the anode active layer contains graphite as the carbon-based anode active material, the peaks for graphite during X-ray diffraction spectroscopy of the anode active layer are 2θ = 26.5±0.2°, 42.4±0.2°, 43.4±0.2°, 44.6±0.2°, 54.7±0.2°, and 77.5±0.2°. This represents the (0,0,2), (1,0,0), (1,0,1)R, (1,0,1)H, (0,0,4), and (1,1,0) crystal planes of the graphite contained in the negative electrode active layer. Generally, in the case of graphite, graphene layers are placed on the a-axis and b-axis planes, and such graphene layers are stacked along the c-axis, resulting in a hexagonal or rhombohedral crystal structure. Here, the crystal plane peaks mentioned above are peaks that show the plane characteristics of such a crystal structure. Furthermore, the peak appearing at 2θ = 43.4 ± 0.2° may be considered to be an overlapping peak corresponding to the (1,0,1)R plane of a carbon-based material and the (1,1,1) plane of a current collector, such as Cu.

[0090] This invention allows for the measurement of the orientation (OI) of graphite by the area ratio of the peak at 2θ = 77.5 ± 0.2° representing the [1,1,0] plane and the peak at 2θ = 54.7 ± 0.2° representing the [0,0,4] plane, specifically, the area ratio obtained by integrating the intensities of the above peaks. Furthermore, X-ray diffraction was measured using the CuKα line as the target line, and to improve the peak intensity resolution, the target line was extracted using a monochromator. At this time, the measurement conditions were 2θ = 10° to 90°, scan speed (° / s) of 0.044 to 0.089, and step size of 0.026° / step. Furthermore, the (0,0,4) plane appearing at 2θ = 54.7 ± 0.2° indicates the thickness-direction characteristics (c-axis direction characteristics) of a layered structure formed by stacking two-dimensional planar structures of graphite layers, while the (1,1,0) plane appearing at 2θ = 77.5 ± 0.2° indicates the planar characteristics (ab-axis direction characteristics) of the stacked graphite layers. Therefore, the smaller the (0,0,4) plane peak indicating the thickness-direction characteristics of the graphite layer plane, and the larger the (1,1,0) plane peak indicating the planar characteristics of the graphite layer, the higher the angle at which the graphite planes are aligned with respect to the negative electrode current collector surface. In other words, the closer the alignment degree (OI) is to 0, the closer the angle or inclination of the graphite layer surface with respect to the negative electrode current collector surface is to 90°, and the larger the value, the closer the inclination with respect to the negative electrode current collector surface is to 0° or 180°.

[0091] In this respect, in the first region of the negative electrode active layer according to the present invention, the ab-axis crystal plane of the carbon-based negative electrode active material is aligned nearly perpendicular to the negative electrode current collector, so the degree of alignment (OI) of the carbon-based negative electrode active material may be lower compared to the nth region of the negative electrode active layer (where 2 ≤ n ≤ 10).

[0092] Specifically, the degree of alignment (OI) of the carbon-based anode active material contained in the first region can be 0.1 to 0.6, and more specifically, it can be 0.15 to 0.6, 0.15 to 0.5, 0.2 to 0.5, 0.2 to 0.4, 0.25 to 0.45, 0.3 to 0.5, or 0.35 to 0.6.

[0093] Furthermore, the degree of alignment of the carbon-based negative electrode active material contained in the nth region (OI nth ) is the degree of alignment (OI) of the carbon-based anode active material contained in the first region. 1st ) can range from 101% to 300%, and more specifically, 101% to 280%, 101% to 260%, 101% to 240%, 101% to 230%, 101% to 220%, 101% to 200%, 150% to 250%, 160% to 230%, 180% to 270%, 185% to 225%, and 170% to 25%. It could be 0%, 105%~130%, 110%~150%, 110%~130%, 120%~180%, 120%~160%, 101%~180%, 150%~200%, 125%~150%, 140%~180%, 160%~190%, 110%~160%, or 120%~150%.

[0094] Furthermore, the average alignment (OI) of the carbon-based anode active material contained in the overall anode active layer can be 0.4 to 1.2, specifically 0.4 to 1.0, 0.4 to 0.9, 0.4 to 0.7, 0.4 to 0.6, 0.6 to 1.0, 0.8 to 1.0, or 0.5 to 0.8.

[0095] The present invention relates to the degree of alignment (OI) of the carbon-based anode active material contained in the first region, the nth region, and the overall anode active layer. 1st and OI nth By controlling the above-described parameters, it is possible to reduce the electrical resistance of the electrode while improving the lithium ion mobility in the negative electrode active layer adjacent to the negative electrode tab during battery charging and discharging, thereby preventing a reduction in the charge / discharge capacity in the first region adjacent to the negative electrode tab. This prevents a reversal of the N / P ratio in the first side portion adjacent to the negative electrode tab, thus preventing lithium deposition.

[0096] Furthermore, the average alignment (OI) of the negative electrode active layer can be 0.1 to 0.5, and specifically 0.2 to 0.4. By controlling the average value of the overall orientation of the negative electrode active layer within the above range, the present invention can maintain a constant alignment of the carbon-based negative electrode active material contained throughout the negative electrode active layer, thereby enabling the uniform realization of the electrical properties of the negative electrode.

[0097] Furthermore, in order to prevent lithium from dendritic deposition on the surface of the negative electrode active layer during battery charging and discharging under high-rate conditions, the first region of the negative electrode active layer is configured such that the intensity ratio of the peaks indicating the (0,0,4) crystal plane and the peaks indicating the (0,0,2) crystal plane during X-ray diffraction (XRD) spectroscopy analysis (I 004 / I 002 ) can be controlled within a certain range. Specifically, the above first region is the above intensity ratio (I 004 / I 002 The ratio of the intensity of the peaks (I) to the peaks (I) that are detected during X-ray diffraction (XRD) spectroscopy is 0.04 or higher, and more specifically, it may be 0.04 to 0.09, 0.04 to 0.07, or 0.071 to 0.095. 004 / I 002 By controlling the above range, the increase in DC internal resistance in the first region can be suppressed, which has the advantage of improving high-rate characteristics and cycle life characteristics.

[0098] On the other hand, the negative electrode active layer according to the present invention may optionally further contain a conductive material, a binder, other additives, etc., along with the negative electrode active material.

[0099] The above conductive material may contain, but is not limited to, one or more of the following: carbon black, acetylene black, Ketjen black, carbon nanotubes, carbon fibers, etc.

[0100] As one example, the above-mentioned negative electrode active layer may contain carbon black, carbon nanotubes, carbon fibers, etc., individually or in combination as conductive materials.

[0101] In this case, the content of the conductive material may be 0.1 to 10 parts by weight per 100 parts by weight of the entire negative electrode active layer, and specifically may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 0.5 to 2 parts by weight. By controlling the content of the conductive material within the above range, the present invention can prevent an increase in the resistance of the negative electrode and a decrease in charging capacity due to a low content of conductive material. Furthermore, it can prevent problems such as a decrease in charging capacity due to a decrease in the content of the negative electrode active material due to an excessive amount of conductive material, or a decrease in rapid charging characteristics due to an increase in the loading amount of the negative electrode active layer.

[0102] Furthermore, the above-mentioned binder is a component that assists in the bonding of the active material to conductive materials and to the current collector, and can be suitably applied within a range that does not degrade the electrical properties of the electrode. Specifically, it may contain one or more of the following: vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, and fluororubber.

[0103] The binder content may be 0.1 to 10 parts by weight per 100 parts by weight of the entire negative electrode active layer, specifically 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 2 to 6 parts by weight. By controlling the binder content in the negative electrode active layer within the above range, the present invention can prevent a decrease in the adhesive strength of the active layer due to a low binder content or a decrease in the electrical properties of the electrode due to an excessive amount of binder.

[0104] Furthermore, the negative electrode current collector is not particularly limited as long as it has high conductivity without inducing chemical changes in the battery. For example, copper, stainless steel, nickel, titanium, and calcined carbon can be used, and in the case of copper or stainless steel, those with surface treatment with carbon, nickel, titanium, silver, etc. can also be used. The average thickness of the negative electrode current collector can be suitably applied in the range of 1 μm to 500 μm, taking into consideration the conductivity and total thickness of the manufactured negative electrode.

[0105] The negative electrode for lithium secondary batteries according to the present invention, having the above-described configuration, is excellent at suppressing lithium deposition on the surface of the negative electrode active layer during charging and discharging of secondary batteries, especially under high-rate conditions. Therefore, lithium secondary batteries containing it have the advantage of exhibiting high safety.

[0106] <Lithium-ion secondary battery> Furthermore, in one embodiment of the present invention, The present invention provides a lithium secondary battery comprising an electrode assembly including a positive electrode, the negative electrode of the present invention as described above, and a separator membrane disposed between the positive electrode and the negative electrode.

[0107] Each lithium secondary battery according to the present invention comprises an electrode assembly in which a plurality of positive electrodes and a plurality of negative electrodes are arranged alternately, with a separation membrane located between them, and an electrolyte composition having a lithium salt and an electrolyte additive dissolved in a non-aqueous organic solvent. In this case, the lithium secondary battery includes the negative electrode of the present invention in which, in the negative electrode active layer, the ab-axis crystal plane of the carbon-based negative electrode active material contained in the region adjacent to the negative electrode tab is aligned so as to be perpendicular and / or nearly perpendicular with respect to the surface of the negative electrode current collector. As a result, the lithium secondary battery has the advantage of high safety because the deposition of lithium on the surface of the negative electrode active layer, especially the surface of the region adjacent to the negative electrode tab, is prevented during charging and discharging of the battery, especially during charging and discharging under high-rate conditions.

[0108] In this case, the negative electrode has the same configuration as described above, so a detailed explanation will be omitted.

[0109] Furthermore, the positive electrode comprises a positive electrode active layer manufactured by coating, drying, and pressing a slurry containing positive electrode active material onto a positive electrode current collector, and the positive electrode active layer may optionally further selectively contain conductive materials, binders, and other additives.

[0110] The above-mentioned positive electrode active material is a substance that can undergo electrochemical reactions on the positive electrode current collector and may include one or more lithium metal oxides represented by the following chemical formulas 1 and 2, which are capable of reversible intercalation and deintercalation of lithium ions.

[0111] [Chemical formula 1] Li x [Ni y Co z Mn w M 1 v ]O2

[0112] [Chemical formula 2] LiM 2 p Mn q P r O4

[0113] In the above chemical formulas 1 and 2, M 1 It is one or more elements from 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, and v are such that 1.0 ≤ x ≤ 1.30, 0.5 ≤ y < 1, and 0 respectively. <z≦0.3、0<w≦0.3、0≦v≦0.1であり、かつy+z+w+v=1であり、 M 2 It is Ni, Co, or Fe, p is 0.05 ≤ p ≤ 1.0, q is either 1-p or 2-p, r is either 0 or 1.

[0114] The lithium metal oxides represented by chemical formulas 1 and 2 above are substances containing high amounts of nickel (Ni) and manganese (Mn), respectively, and when used as positive electrode active materials, they have the advantage of being able to stably supply high capacity and / or high voltage electricity.

[0115] In this case, the lithium metal oxide represented by the above chemical formula 1 is LiNi 0.8 Co 0.1 Mn 0.1 O2, LiLiLi 0.6 Co 0.2 Mn 0.2 O2, LiLiLi 0.9 Co 0.05 Mn 0.05 O2, LiLiLi 0.6 Co 0.2 Mn 0.1 Al 0.1 O2, LiLiLi 0.6 Co 0.2 Mn 0.15 Al 0.05 O 2、 LiRing 0.7 Co 0.1 Mn 0.1 Al 0.1 The lithium metal oxide represented by the above chemical formula 2 may contain O2, etc., and LiNi 0.7 Mn 1.3 O4, LiSa 0.5 Mn 1.5 O 4、 LiRing 0.3 Mn 1.7 O 4、 LiFePO4, LiFe 0.8 Mn 0.2 PO4, LiFe 0.5 Mn 0.5 It may contain PO4 and other components, which can be used alone or in combination.

[0116] Furthermore, the above-mentioned positive electrode active material may be present in 85 parts by weight or more, based on the weight of the positive electrode active layer, specifically in the form of 90 parts by weight or more, 93 parts by weight or more, or 95 parts by weight or more.

[0117] Furthermore, the positive electrode active layer may further contain conductive materials, binders, and other additives along with the positive electrode active material.

[0118] In this case, the conductive material is used to improve the electrical performance of the positive electrode, and may be one or more of those commonly used in the industry, specifically natural graphite, artificial graphite, carbon black, acetylene black, Denka black, Ketjen black, Super P, channel black, furnace black, lamp black, thermal black, graphene, and carbon nanotubes.

[0119] Furthermore, the conductive material may be included in amounts of 0.1 to 5 parts by weight based on the weight of each positive electrode active layer, specifically in amounts of 0.1 to 4 parts by weight, 2 to 4 parts by weight, 1.5 to 5 parts by weight, 1 to 3 parts by weight, 0.1 to 2 parts by weight, or 0.1 to 1 part by weight.

[0120] Furthermore, the binder plays a role in binding the positive electrode active material, positive electrode additive, and conductive material together, and any binder having such a function can be used without particular limitations. Specifically, the binder may include one or more resins from among polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, and copolymers thereof. As one example, the binder may include polyvinylidene fluoride.

[0121] Furthermore, the above-mentioned binder may be included in an amount of 1 to 10 parts by weight based on the weight of each positive electrode active layer, specifically in an amount of 2 to 8 parts by weight, or 1 to 5 parts by weight.

[0122] The total thickness of the positive electrode active layer described above is not particularly limited, but it may be 50 μm to 300 μm, and more specifically, it may be 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.

[0123] Furthermore, the positive electrode can be made of a material that has high conductivity without inducing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, or calcined carbon can be used, and in the case of aluminum or stainless steel, materials that have been surface-treated with carbon, nickel, titanium, silver, etc. can also be used. The average thickness of the current collector can be suitably applied in the range of 3 μm to 500 μm, taking into consideration the conductivity and total thickness of the manufactured positive electrode.

[0124] On the other hand, the separation membrane interposed between the positive and negative electrodes of each unit cell is an insulating thin film having high ion permeability and mechanical strength, and is not particularly limited as long as it is commonly used in the industry, but specifically, it may contain one or more polymers from among chemically resistant and hydrophobic polypropylene, polyethylene, and polyethylene-propylene copolymer. The above separation membrane may have the form of a porous polymer substrate such as a sheet or nonwoven fabric containing the above polymer, and in some cases, it may have the form of a composite separation membrane in which organic or inorganic particles are coated with an organic binder on the above porous polymer substrate. Furthermore, the above separation membrane may have an average pore diameter of 0.01 μm to 10 μm and an average thickness of 5 μm to 300 μm.

[0125] On the other hand, the lithium secondary battery according to the present invention is not particularly limited, but may preferably be a secondary battery that includes a stacked type, a zigzag type, or a zigzag-stack type electrode assembly. As one example, the lithium secondary battery according to the present invention may be a pouch-type secondary battery or a prismatic secondary battery.

[0126] The negative electrode applied to the lithium secondary battery according to the present invention has a degree of alignment (S) of the carbon-based active material contained in the first region of the negative electrode active layer adjacent to the negative electrode tab. 60 / 0 By reducing the OI (or OI), it is possible to reduce electrical resistance while improving lithium ion mobility in the first region adjacent to the negative electrode tab during battery charging and discharging, thereby preventing a reduction in the charge / discharge capacity per unit area of ​​that region. This prevents the reversal of the N / P ratio that occurs in the negative electrode active layer adjacent to the negative electrode tab during high-rate charging and discharging, thus preventing lithium deposition. Therefore, the above lithium secondary battery has high safety and the advantage of being able to charge and discharge for long periods of time under high-rate conditions.

[0127] The present invention will be described in more detail below with reference to examples and experimental examples.

[0128] However, the following examples and experimental examples are illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0129] <Examples 1-4. Manufacturing of negative electrodes for lithium secondary batteries> Natural graphite was prepared as the negative electrode active material, carbon black as the conductive material, and carboxymethylcellulose (CMC) and styrene-butadiene rubber (SBR) as binders. The sphericity of the natural graphite was adjusted as shown in Table 1 below. 95 parts by weight of natural graphite, 1 part by weight of carbon black, 1.5 parts by weight of carboxymethylcellulose (CMC), and 2.5 parts by weight of styrene-butadiene rubber (SBR) were mixed with water to form a negative electrode slurry with a solid content of 50%. The negative electrode slurry was then cast onto a copper sheet (thickness: 10 μm) being transported on a roll-to-roll system.

[0130] Subsequently, four magnets of the same size were arranged in a sequence perpendicular to the direction of movement of the coated negative electrode slurry (i.e., in the width direction of the negative electrode slurry). At this time, the magnetic field strength applied to the magnets was such that, as the position of the magnets changed from the first side surface of the negative electrode slurry, which is the negative electrode active layer where the negative electrode tab is provided, to the second side surface, the magnetic field strength decreased in a stepwise manner from 2.0 T to 1.0 T at predetermined intervals, or (b) decreased in a gradient, as shown in Table 1, thereby inducing the orientation of natural graphite in the negative electrode slurry. The time for which the magnetic field was applied to the upper surface of the negative electrode slurry was adjusted to 5 seconds. After that, the copper sheet coated with the negative electrode slurry was dried in a vacuum oven at 130°C, then rolled to a density of 1.63 ± 0.2 g / cc, and the negative electrode was manufactured by continuously slitting and notching so that the negative electrode tab was provided on the side surface where the first side surface was located.

[0131] To confirm the alignment of the carbon-based anode active material in each anode active layer region of the manufactured anode, the anode active layer was divided into four regions (n=4) from the first side where the anode tab is located to the second side, and each region had the same length ratio to the total length of the anode active layer. At this time, the lengths of the first to fourth regions were the same as the size of the magnet used to apply the magnetic field. Subsequently, i) near-end X-ray absorption fine structure (NEXAFS) spectroscopy and X-ray diffraction (XRD) spectroscopy were performed on each anode active layer region of the manufactured anode, and the spectra were measured. The degree of alignment (S) of the natural graphite (i.e., carbon-based anode active material) was determined from the spectra obtained using the following equations 1 to 4. 60 / 0 ii) and OI) were calculated and shown in Table 1 below. Also, from the spectrum obtained when X-ray diffraction (XRD) spectroscopy was performed on the first region of the negative electrode active layer, the ratio (I) of the intensity of the peak representing the (0,0,4) plane to the intensity of the peak representing the (0,0,2) plane was calculated. 004 / I 002 The following values ​​were calculated and are shown in Table 2 below.

[0132]

number

[0133]

number

[0134]

number

[0135] In equations 1 to 3, S 60 / 0 This is the peak intensity ratio (I0) when the incident angle of the X-ray is 0° during near-end X-ray absorption fine structure (NEXAFS) spectroscopy. B / A The peak intensity ratio (I60) when the incident angle of X-rays to ) is 60° B / A This represents the value of ), I60 A This represents the intensity of the strongest peak among the peaks present at 286±1.0eV when the X-ray incidence angle is 60°. I60 B This represents the intensity of the strongest peak among the peaks present at 292.5±1.0eV when the incident angle of X-rays is 60°. I0 A This represents the intensity of the peak with the strongest intensity among the peaks present at 286±1.0eV when the incident angle of X-rays is 0°. I0 B This represents the intensity of the strongest peak among the peaks present at 292.5±1.0eV when the X-ray incidence angle is 0°.

[0136] [Formula 4] OI=I 004 / I 110

[0137] In Equation 4, I 004 This represents the area of ​​the peak indicating the (0,0,4) crystal plane during X-ray diffraction (XRD) spectroscopy analysis of the negative electrode active layer. I 110This represents the area of ​​the peak indicating the (1,1,0) crystal plane during X-ray diffraction (XRD) spectroscopy analysis of the negative electrode active layer.

[0138] [Table 1]

[0139] [Table 2]

[0140] Furthermore, the measurement conditions for near-end X-ray absorption fine structure (NEXAFS) and X-ray diffraction (XRD) are as follows.

[0141] (1) Near-edge X-ray absorption fine structure (NEXAFS) - Acceleration voltage: 1.0 GeV ~ 1.5 GeV -Accumulated current: 80mA~350mA - Angle of incidence: 60° or 0°

[0142] (2) X-ray diffraction (XRD) -Target: Cu(Kα-ray) graphite monochromatization device - Slit: Divergent slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree

[0143] <Comparative Examples 1-3. Manufacturing of negative electrodes for lithium secondary batteries> A negative electrode for a lithium secondary battery was manufactured using the same method as in Example 1, except that no magnetic field was applied to the surface of the negative electrode slurry coated on a copper sheet, or a magnetic field of 1.0 T or 2.0 T was applied without changing the strength of the magnetic field.

[0144] At this time, i) the degree of spheroidization of the carbon-based anode active material, and ii) the degree of alignment (S) of the natural graphite (i.e., carbon-based anode active material) in the first and fourth regions of the anode active layer. 60 / 0 (I) and OI), and iii) the ratio of the intensity of the peak representing the (0,0,4) plane to the intensity of the peak representing the (0,0,2) plane calculated from X-ray diffraction (XRD) (I004 / I 002 The results are shown in Table 3 below.

[0145] [Table 3]

[0146] <Examples 5-8 and Comparative Examples 4-6. Manufacturing of Lithium Secondary Batteries> LiNi with a particle size of 5 μm is used as the positive electrode active material. 0.7 Co 0.1 Mn 0.1 Al 0.1 O2 was prepared and mixed with polyvinylidene fluoride and N-methylpyrrolidone (NMP) in a weight ratio of 94:3:3 as a carbon-based conductive material and binder to form a slurry. This slurry was then cast onto an aluminum sheet, dried in a vacuum oven at 120°C, and then rolled to produce a cathode.

[0147] A separation membrane made of polypropylene with a thickness of 18 μm was interposed between the positive electrode obtained above and the negative electrodes manufactured in the examples and comparative examples, respectively. After inserting the membrane into a case, the electrolyte composition was injected to assemble the lithium secondary battery.

[0148] The types of negative electrodes applied to each lithium secondary battery are shown in Table 4 below.

[0149] [Table 4]

[0150] <Experimental Example 1> To evaluate the safety of the lithium secondary battery according to the present invention during high-rate charge and discharge, the following experiments were conducted on each lithium secondary battery manufactured in the examples and comparative examples.

[0151] (i) Evaluation of high-rate characteristics of secondary batteries First, each manufactured lithium secondary battery underwent initial charging. Specifically, the lithium secondary batteries were initially charged at a temperature of 25°C with a charging current of 0.3C until the charging termination voltage reached 4.2V to 4.25V, and then activated by continuing to charge until the current density at the termination voltage reached 0.02C.

[0152] Each activated lithium secondary battery was fully charged at room temperature (22°C) at a rate of 0.1 C-rate. Then, the initial discharge capacity was measured while discharging the fully charged lithium secondary batteries at a rate of 0.1 C-rate. Afterward, each lithium secondary battery was fully charged again at a rate of 0.1 C-rate, and the relative discharge capacity percentage was measured relative to the initial discharge capacity at each discharge rate while discharging at 1.0 C, 2.0 C, 5.0 C, and 9.0 C-rates. The measured discharge capacity percentages are shown in Table 5.

[0153] (b) Safety evaluation of secondary batteries First, each manufactured lithium secondary battery underwent initial charging. Specifically, the lithium secondary batteries were initially charged at a temperature of 25°C with a charging current of 0.3C until the charging termination voltage reached 4.2V to 4.25V, and then activated by continuing to charge until the current density at the termination voltage reached 0.02C.

[0154] Subsequently, each activated lithium secondary battery was charged at a temperature of 25°C with a charging current of 3.0C until the charging termination voltage reached 4.2V to 4.25V, and then discharged in constant current mode until the current density at the termination voltage reached 0.02C. A total of 100 such charge-discharge cycles were performed, and each lithium secondary battery that had undergone 100 charge-discharge cycles was disassembled to check for lithium deposition on the negative electrode surface. The results are shown in Table 5.

[0155] [Table 5]

[0156] As shown in Table 5 above, it was found that the secondary battery containing the negative electrode for lithium secondary batteries according to the present invention not only has excellent high-rate charge-discharge efficiency, but also suppresses lithium metal deposition on the negative electrode surface even when high-rate charging is repeatedly performed.

[0157] This means that the degree of orientation in which the carbon-based negative electrode active material is aligned nearly perpendicularly to the surface of the negative electrode current collector is greatly induced in the first region of the negative electrode active layer adjacent to the negative electrode tab, resulting in a lower electrode resistance in the first region, and thereby improving the capacitance reduction per unit area on the first surface.

[0158] These results indicate that the negative electrode for lithium secondary batteries according to the present invention is excellent at suppressing lithium deposition on the surface of the negative electrode active layer during high-rate charging and discharging of secondary batteries. Therefore, lithium secondary batteries containing it have high safety and can be charged and discharged for long periods under high-rate conditions.

[0159] While preferred embodiments of the present invention have been described above with reference to those skilled in the art or those with ordinary knowledge in the art, it will be understood that the present invention can be modified and altered in various ways without departing from the spirit and technical scope of the invention as described in the claims below.

[0160] Therefore, the technical scope of the present invention is not limited to what is described in the summary of the invention in the specification, but is defined by the claims.

Claims

1. The negative electrode current collector includes a negative electrode active layer provided on at least one surface and containing a carbon-based negative electrode active material, and a negative electrode tab that is drawn out to one side of the negative electrode active layer and provided on a plain portion of the negative electrode current collector that does not contain the negative electrode active layer. The negative electrode active layer is divided into first to nth regions (where 2 ≤ n ≤ 10) that have the same length ratio to the total length, based on a thickness-direction cross-sectional structure in which a negative electrode tab is provided on one side, and are sequentially arranged from the first side surface from which the negative electrode tab is drawn out to the second side surface opposite it. The degree of alignment of the carbon-based anode active material, represented by the following formula 1, increases as we progress from the first region to the nth region. In the first region of the negative electrode active layer, the degree of alignment of the carbon-based negative electrode active material represented by Equation 1 (S 60 / 0) is 0.8 or less. Carbon-based negative electrode active material is a negative electrode for lithium secondary batteries that contains graphite. [Math 1] [Math 2] [Math 3] In equations 1 to 3, S ６０／０ This is the peak intensity ratio (I0) when the incident angle of the X-rays is 0° during near-edge X-ray absorption fine structure (NEXAFS) spectroscopy. Ｂ／Ａ The peak intensity ratio (I60) when the incident angle of X-rays to ) is 60° Ｂ／Ａ This represents the value of ), I60 Ａ This represents the intensity of the peak with the strongest intensity among the peaks present at 286 ± 1.0 eV when the incident angle of X-rays is 60°. I60 Ｂ This represents the intensity of the peak with the strongest intensity among the peaks present at 292.5 ± 1.0 eV when the incident angle of X-rays is 60°. I0 Ａ This represents the intensity of the peak with the strongest intensity among the peaks present at 286 ± 1.0 eV when the incident angle of X-rays is 0°. I0 Ｂ This represents the intensity of the peak with the strongest intensity among the peaks present at 292.5 ± 1.0 eV when the incident angle of X-rays is 0°.

2. The first region of the negative electrode active layer is the degree of alignment of the carbon-based negative electrode active material represented by Equation 1 (S ６０／０ The negative electrode for a lithium secondary battery according to claim 1, wherein the value of ) is 0.01 to 0.

8.

3. The negative electrode for a lithium secondary battery according to claim 1, wherein the negative electrode active layer has an increasing degree of alignment of carbon-based negative electrode active material according to the following formula 4 as it progresses from the first region to the nth region. [Formula 4] O.I=I ００４ / I １１０ In Equation 4, I ００４ This represents the area of ​​the peak indicating the (0,0,4) crystal plane during X-ray diffraction (XRD) spectroscopy analysis of the negative electrode active layer. I １１０ This represents the area of ​​the peak indicating the (1,1,0) crystal plane during X-ray diffraction (XRD) spectroscopy analysis of the negative electrode active layer.

4. The anode for a lithium secondary battery according to claim 3, wherein the carbon-based anode active material contained in the nth region has an alignment degree according to formula 4 that is 110% to 300% of the alignment degree of the carbon-based anode active material contained in the first region.

5. The anode for a lithium secondary battery according to claim 3, wherein the first region of the anode active layer has an average alignment degree of 0.1 to 0.6 of the carbon-based anode active material according to formula 4.

6. The negative electrode for a lithium secondary battery according to claim 1 or 3, wherein the negative electrode active layer has a gradient in which the degree of alignment of the carbon-based negative electrode active material increases as it progresses from the first region to the nth region.

7. The negative electrode for a lithium secondary battery according to claim 1 or 3, wherein the degree of alignment of the carbon-based negative electrode active material increases in a stepwise manner as the negative electrode active layer progresses from the first region to the nth region.

8. The first region of the negative electrode active layer is defined by the ratio (I) of the intensity of the peak representing the (0,0,4) crystal plane to the intensity of the peak representing the (0,0,2) crystal plane during X-ray diffraction (XRD) spectroscopy analysis. ００４ / I ００２ The negative electrode for a lithium secondary battery according to claim 1, wherein the coefficient of

9. The anode for a lithium secondary battery according to claim 1, wherein the carbon-based anode active material comprises one or more of natural graphite and artificial graphite.

10. The carbon-based negative electrode active material has a spheroidization degree of 0.75 or higher, as described in claim 1, for a lithium secondary battery negative electrode.

11. A lithium secondary battery comprising an electrode assembly including a positive electrode, a negative electrode as described in claim 1, and a separator membrane disposed between the positive electrode and the negative electrode.

12. The lithium secondary battery according to claim 11, wherein the positive electrode is provided on at least one surface of the positive electrode current collector and includes a positive electrode active layer containing one or more positive electrode active materials from among lithium metal oxides represented by the following chemical formulas 1 and 2. [Chemical formula 1] Li ｘ [Ni ｙ Co ｚ Mn ｗ M １ ｖ ]O ２ [Chemical formula 2] LiM ２ ｐ Mn １－ｐ O ４ In the aforementioned chemical formulas 1 and 2, M １ is one or more elements from 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, and v are such that 1.0 ≤ x ≤ 1.30, 0.5 ≤ y < 1, 0 < z ≤ 0.3, 0 < w ≤ 0.3, and 0 ≤ v ≤ 0.1, and y + z + w + v = 1. M ２ is Ni, Co, or Fe, p is 0.05 ≤ p ≤ 1.

0.

13. The positive electrode active material is LiNi ０．８ Co ０．１ Mn ０．１ O ２ LiNi ０．６ Co ０．２ Mn ０．２ O ２ LiNi ０．９ Co 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、 LiNi ０．７ Co ０．１ Mn ０．１ Al ０．１ O ２ LiNi ０．７ Mn １．３ O ４ LiNi ０．５ Mn １．５ O ４ LiNi ０．３ Mn １．７ O ４ LiFePO ４ LiFe ０．８ Mn ０．２ PO ４ , and LiFe ０．５ Mn ０．５ PO ４ A lithium secondary battery according to claim 12, comprising one or more of the following.

14. The lithium secondary battery according to claim 11, wherein the electrode assembly is a stacked electrode assembly, a zigzag electrode assembly, or a zigzag-stacked electrode assembly.

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