Electrode assembly

Abstract

The present invention relates to an electrode assembly. In the electrode assembly, the orientation of the carbon-based anode active material of the anode included in the central portion and the carbon-based anode active material of the anode included in the outer portion is controlled such that the degree of degradation of electrodes included in the electrode assembly can be uniformly implemented. Therefore, a secondary battery including same has excellent lifetime characteristics and capacity characteristics.

Description

electrode assembly

[0001] The present invention relates to an electrode assembly.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0170832 dated November 26, 2024, and all contents disclosed in the document of said patent application are incorporated herein as part of this specification.

[0003]

[0004] Recently, lithium-ion batteries are being widely applied not only to small devices such as portable electronic devices but also to medium-to-large devices such as battery packs or power storage systems for hybrid and electric vehicles. In particular, as concern for environmental issues grows, the demand base for high-capacity batteries is expanding due to the growth of the market for devices employing high-capacity batteries, such as electric vehicles and hybrid electric vehicles, which can replace fossil fuel-using vehicles like gasoline and diesel cars—a major cause of air pollution. To manufacture lithium-ion batteries that possess high energy density, high output, and high discharge voltage as the power source for these devices, there is a demand for high-capacity electrode designs.

[0005] In this regard, as a means to increase the energy density of secondary batteries, attempts have been made to reduce the weight and / or thickness of components that do not generate capacity in the electrodes—namely, electrode tabs, casings, separators, and current collectors—while increasing the weight and / or thickness of components that do generate capacity, such as the electrode active layer. Due to these changes, secondary batteries exhibit an effect of increasing the redox reaction rate in regions where electron movement is smooth during charging and discharging. Specifically, in the case of an electrode assembly having a structure in which multiple positive and negative electrodes are stacked, the redox reaction proceeds relatively faster in the center of the electrode assembly. However, since degradation is accelerated in the center of the electrode assembly due to the accelerated redox reaction, electrical resistance increases as cycles progress. This ultimately increases the degradation disparity between the center and the outer parts of the electrode assembly, which not only reduces lifespan but also leads to a decrease in the capacity of the secondary battery.

[0006]

[0007] The objective of the present invention is to provide an electrode assembly with excellent lifespan and capacity characteristics and a secondary battery including the same.

[0008]

[0009] In order to solve the aforementioned problem,

[0010] The present invention is,

[0011] A monocell stack comprising a plurality of monocells arranged in the thickness direction, each monocell consisting of a unit cell with a stacked separator and a cathode and a unit cell with a stacked separator and an anode, and a monocell stack, and

[0012] It includes a half cell positioned at the rear of the monocell stack, having a structure in which a separator, a cathode, and a separator are stacked;

[0013] The above cathode is formed on at least one surface of a cathode current collector and includes a cathode active layer comprising a carbon-based cathode active material;

[0014] The above monocell stack is divided into first to third regions from the front to the rear where the monocells are arranged;

[0015] One or more of the cathodes included in the first region and the cathodes included in the third region provide an electrode assembly in which the orientation degree (OI) represented by Equation 1 below is smaller than the orientation degree (OI) of the cathode included in the second region when X-ray diffraction analysis is performed on the cathode active layer:

[0016] [Equation 1]

[0017] OI= I 004 / I 110

[0018] In the above Equation 1,

[0019] I 110 represents the intensity of the peak indicating the (110) crystal plane of the carbon-based cathode active material during X-ray diffraction spectroscopy (XRD) measurement of the cathode active layer, and

[0020] I 004 represents the intensity of the peak indicating the (004) crystal plane of the carbon-based cathode active material during X-ray diffraction spectroscopy (XRD) measurement of the cathode active layer.

[0021] One or more of the cathodes included in the first region and the cathodes included in the third region may have an orientation degree (OI) in the range of 0.5 to 15.

[0022] The orientation degree (OI) of the cathode included in the second region may have a ratio of 105% to 1,000% based on the orientation degree (OI) of the cathode included in the first region and / or the third region.

[0023] The above monocell stack can satisfy the following Equation 2, where the number of monocells included in the first region, the second region, and the third region are denoted as n1, n2, and n3, respectively:

[0024] [Equation 2]

[0025] 0.25 ≤ n2 / (n1+n3) ≤ 15.

[0026] The number of monocells (n2) included in the second region above may be 5 to 35.

[0027] The cathode included in the second region may have a greater pore resistance than the cathode included in the first or third region.

[0028] The cathode included in the second region above may have a pore resistance deviation of 0.05 Ω or more compared to the cathode included in the first region and / or the third region.

[0029] The cathode included in the first region and / or third region may each have a tortuosity in the range of 2.0% to 8.0%.

[0030] The above carbon-based cathode active material may include one or more of natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, carbon microbeads, mesophase pitch, and graphitized coke.

[0031] The average thickness of the above cathode active layer may be in the range of 100㎛ to 500㎛.

[0032]

[0033] Furthermore, the present invention,

[0034] The electrode assembly according to the present invention, and

[0035] A secondary battery comprising an electrolyte composition that impregnates the electrode assembly is provided.

[0036]

[0037] The electrode assembly according to the present invention can achieve a uniform degree of degradation of the electrodes included in the electrode assembly by controlling the orientation of the carbon-based negative electrode active material included in the center and the carbon-based negative electrode active material included in the outer part. Accordingly, a secondary battery including the same has the advantage of excellent lifespan and capacity characteristics.

[0038]

[0039] FIG. 1 is a cross-sectional view schematically showing the structure of an electrode assembly according to the present invention.

[0040]

[0041] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are to be described in detail in the detailed description.

[0042] In the present invention, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0043] In this specification, "include as a main component" may mean including a defined component in an amount of 50 wt% or more (or 50 volume% or more), 60 wt% or more (or 60 volume% or more), 70 wt% or more (or 70 volume% or more), 80 wt% or more (or 80 volume% or more), 90 wt% or more (or 90 volume% or more), or 95 wt% or more (or 95 volume% or more) with respect to the total weight (or total volume). For example, "include carbon atoms as a main component" may mean including 50 wt% or more, 60 wt% or more, 70 wt% or more, 80 wt% or more, 90 wt% or more, or 95 wt% or more based on the total weight of the carbon-based compound. In some cases, it may mean that the entire carbon-based compound consists of carbon atoms and is included in an amount of 100 wt%.

[0044] In this specification, the “thickness direction of the monocell” may be the same as the direction perpendicular to the plane formed by the combination of the width direction and the length direction of the monocell. Additionally, the thickness direction of the monocell is the same as the direction in which a plurality of monocells are stacked / assembled, and this may be defined as the “X-axis direction” of FIG. 1.

[0045] Additionally, in this specification, "center" refers to a range including a defined area or the exact center of said area, and in some cases, may mean the exact center itself.

[0046]

[0047] The present invention will be described in more detail below.

[0048]

[0049] electrode assembly

[0050] The present invention is,

[0051] A monocell stack comprising a plurality of monocells arranged in the thickness direction, each monocell consisting of a unit cell with a stacked separator and a cathode and a unit cell with a stacked separator and an anode, and a monocell stack, and

[0052] The present invention provides an electrode assembly comprising a separator, a cathode, and a half cell disposed at the rear of the monocell stack having a stacked structure of the separator.

[0053]

[0054] The electrode assembly according to the present invention may be applied to a lithium secondary battery.

[0055] The electrode assembly comprises a monocell stack in which a plurality of monocells, each composed of a unit cell including an anode and a cathode, are arranged in the thickness direction, and a half cell arranged at the rear of the monocell stack.

[0056] FIG. 1 is a cross-sectional view schematically showing the structure of an electrode assembly (10) according to the present invention. Referring to FIG. 1, the electrode assembly (10) comprises a plurality of monocells (110) composed of a unit cell (110, i.e., 'negative unit cell') in which a negative electrode (111a) and a separator (111b) are stacked; and a unit cell (112, i.e., 'positive unit cell') in which an positive electrode (112a) and a separator (112b) are stacked. The plurality of monocells (110) may have the form of a monocell stack (11) arranged along the thickness direction of the monocell (i.e., the X-axis direction).

[0057] A half cell (120) is disposed at the rear of the monocell stack (11), comprising an electrode having a polarity opposite to that of the monocell exposed at the rear of the stack. For example, the electrode assembly (10) may include a half cell (120) in which a unit cell (112) having a positive electrode is exposed at the rear of the monocell stack (11) as in FIG. 1, with a unit cell (112) having a positive electrode disposed therein, and a separator (121b) disposed on both sides of the negative electrode (121a).

[0058] The monocell stack (11) is divided into a first region (11a), a second region (11b), and a third region (11c) from the front to the rear where the monocells are arranged.

[0059] In the plurality of monocells (110) constituting the monocell stack above, the crystal plane characteristics of the negative electrode active material included in the negative electrode can be controlled differently for each region of the monocell stack (11).

[0060] Specifically, each monocell (110) includes a negative electrode (111a) and a positive electrode (112a). At this time, the negative electrode (111a) includes a negative active layer containing a negative active material on at least one surface of a negative current collector. The negative active material may include a carbon-based negative active material that contains carbon atoms as a main component, as a negative active material exhibiting electrochemical activity. Examples of the carbon-based negative active material include natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, carbon microbeads, as well as mesophase pitch or cokes (raw coke, green coke, pitch coke, needle coke, petroleum coke, coal coke, etc.) that have been graphitized. The carbon-based negative active material is formed by stacking multiple layers in which carbon atoms form a network structure and are spread out in a planar shape. In such carbon-based negative electrode active materials, lithium ions can penetrate from the edge surface (the surface where the layers overlap) of the stacked layers and diffuse between the layers during charging of the secondary battery, and lithium ions can be released from the edge surface of the layers during discharge. At this time, since the electrical resistance in the plane direction of the layer of the carbon-based negative electrode active material is lower than the electrical resistance in the stacking direction of the layer, an electron conduction path is formed along the plane direction of the layer. Therefore, if the plane direction of the layer of the carbon-based negative electrode active material is controlled, the electrical resistance of the negative electrode containing it can be controlled. The electrode assembly (10) of the present invention utilizes the characteristics of such carbon-based negative electrode active material. Specifically, the electrode assembly (10) of the present invention is characterized by orienting the (002) crystal plane of the carbon-based negative electrode active material included in the outer part where electron movement is not active, i.e., the first region (11a) and / or the third region (11c), at a predetermined angle with respect to the negative electrode current collector.

[0061] The degree of orientation of the carbon-based cathode active material can be confirmed through crystal plane analysis of the carbon-based cathode active material. Specifically, the degree of orientation of the carbon-based cathode active material can be determined through X-ray diffraction (XRD) or near-end X-ray fluorescence spectroscopy (NEXAFS) on the cathode active layer containing the carbon-based cathode active material.

[0062] For example, in the electrode assembly (10), any one or more of the cathodes included in the first region (11a) and the cathodes included in the third region (11c) may satisfy an orientation degree (OI) represented by the following Equation 1 in the range of 0.5 to 15 when X-ray diffraction analysis is performed on the cathode active layer:

[0063] [Equation 1]

[0064] OI= I 004 / I 110

[0065] In the above Equation 1,

[0066] I 110 represents the intensity of the peak indicating the (110) crystal plane of the carbon-based cathode active material during X-ray diffraction spectroscopy (XRD) measurement of the cathode active layer, and

[0067] I 004 represents the intensity of the peak indicating the (004) crystal plane of the carbon-based cathode active material during X-ray diffraction spectroscopy (XRD) measurement of the cathode active layer.

[0068]

[0069] The orientation degree (OI) of the carbon-based cathode active material defined by Equation 1 above can serve as a relative indicator representing the degree to which the crystal planes of the carbon-based cathode active material are oriented in a certain direction, specifically with respect to the surface of the cathode current collector, when measured by X-ray diffraction (XRD). When measured by X-ray diffraction, the peaks representing the carbon-based cathode active material in the cathode active layer appear at 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°. The above peaks represent the (002) plane, (100) plane, (101)R plane, (101)H plane, (004) plane, and (110) plane among the crystal planes of the carbon-based cathode active material. In addition, the peak appearing at 2θ=43.4±0.2° can be seen as an overlap between the (101)R plane of the carbon-based cathode active material and the (111) plane of the current collector, for example, copper (Cu).

[0070] The orientation degree (OI) of the carbon-based negative electrode active material can be determined through the ratio of the intensity of the peak at 2θ=54.7±0.2° representing the (004) plane and the peak at 2θ=77.5±0.2° representing the (110) plane. Here, the peak at 2θ=54.7±0.2° represents the ab-axis crystal plane of the carbon-based negative electrode active material among the crystal planes of the carbon-based negative electrode active material. Therefore, the orientation degree (OI) may indicate that the slope with respect to the surface of the negative electrode current collector is close to 90° as its value approaches 0, and the slope with respect to the surface of the negative electrode current collector is close to 0° or 180° as its value increases.

[0071] The electrode assembly (10) according to the present invention has a configuration in which the crystal planes of the carbon-based cathode active material of the cathode included in the first region (11a) and / or the third region (11c) are aligned at a predetermined angle with respect to the cathode current collector. Accordingly, the cathode included in the first region (11a) and / or the third region (11c) may have an orientation degree (OI) according to Formula 1 within a predetermined range.

[0072] Specifically, in the electrode assembly (10), any one or more of the cathodes (111a) included in the first region (11a) and the cathodes included in the third region (11c) may each satisfy an orientation degree (OI) represented by Equation 1 in the range of 0.5 to 15 when X-ray diffraction analysis is performed on the cathode active layer. For example, any one or more of the cathodes (111a) included in the first region (11a) and the cathodes included in the third region (11c) may each satisfy 0.5 to 12; 0.5 to 10; 0.5 to 9; 0.5 to 8; 0.5 to 6; 0.5 to 5; 0.5 to 3.5; 0.5 to 2.9; 1 to 14; 3 to 12; 5 to 10; 6 to 12; 2 to 6; 2 to 8; It may have an orientation degree (OI) in the range of 4 to 9; 3 to 9; 3.5 to 6.0; 4.5 to 9.0; 4.2 to 8.9; or 2.1 to 5.5. This means that the carbon-based negative electrode active material contained in the first region (11a) and / or the third region (11c) of the electrode assembly is aligned to have an angle of 60° or more, 60 to 80°, 70 to 90°, 80 to 90°, 65 to 85°, or 70 to 85° with respect to the negative electrode current collector.

[0073] The second region (11b) of the electrode assembly may have a greater degree of orientation (OI) of the carbon-based cathode active material compared to the first region (11a) and the third region (11c). This means that the carbon-based cathode active material of the cathode included in the second region is not oriented with respect to the cathode current collector; or even if oriented, the angle of alignment with respect to the cathode current collector is lower than that of the carbon-based cathode active material of the cathode included in the first region (11a) and / or the third region (11c), or the frequency of aligned carbon-based cathode active material is lower.

[0074] For example, the cathode included in the second region (11b) may have an orientation degree (OI) represented by Equation 1 during X-ray diffraction analysis of the cathode active layer in a ratio of 105% to 1,000% based on the orientation degree (OI) of the cathode included in the first region (11a) and / or the cathode included in the third region (11c). For example, the cathode included in the second region (11b) may have an orientation degree (OI) of 105% to 150%; 105% to 200%; 105% to 400%; 105% to 600%; 105% to 800%; 150% to 900%; 200% to 800%; 300% to 900%; based on the orientation degree (OI) of the cathode included in the first region (11a) and / or the cathode included in the third region (11c). It may have an orientation (OI) in the range of 400% to 800%; 500% to 1,000%; 700% to 1,000%; 900% to 1,000%; 200% to 400%; 400% to 600%; 110% to 250%; or 300% to 500%.

[0075] The present invention allows the orientation degree (OI) of the cathode included in the second region (11b) to have a ratio of the above-described range based on the orientation degree (OI) of the cathode included in the first region (11a) and / or the third region (11c), so that the redox reactivity in the second region (11b) is not reduced during charging and discharging, and the cathode can degrade at a rate similar to that of the adjacent first region (11a) and / or third region (11c).

[0076] The first region (11a) and / or third region (11c) of the electrode assembly (10) may have improved electrical performance by aligning the carbon-based cathode active material of the cathode at a predetermined angle with respect to the cathode current collector. Specifically, the carbon-based cathode active material of the cathode included in the first region (11a) and / or third region (11c) may have its crystal plane aligned with respect to the cathode current collector, thereby shortening the toutroosity, which indirectly indicates the movement path of lithium ions during charging and discharging. A cathode with shortened toutroosity exhibits faster insertion and extraction rates of lithium ions during charging and discharging. Therefore, the electrode assembly of the present invention can reduce the variation in the redox reaction rate between the first and third regions during charging and discharging, thereby reducing the variation in degradation degree by region.

[0077] At this time, the cathode included in the first region (11a) and / or the cathode included in the third region (11c) may each have a curvature of the cathode active layer in the range of 2.0% to 8.0%. Specifically, the cathode included in the first region (11a) and / or the cathode included in the third region (11c) may each have a curvature of the cathode active layer in the range of 3.0% to 8.0%; 4.0% to 8.0%; 5.0% to 8.0%; 4.0% to 8.0%; 5.0% to 8.0%; 3.0% to 7.0%; 4.0% to 7.0%; 4.0% to 6.5%; 5.0% to 6.5%; 4.0% to 6.0%; 3.5% to 6.0%; 4.0% to 5.0%; It may be in the range of 4.0% to 4.9%; 4.0% to 4.5%; 4.2% to 4.8%; or 4.1% to 4.4%.

[0078] The cathode included in the first region (11a) and / or the third region (11c) may have an electrical resistance of the cathode active layer that is smaller than that of the cathode active layer of the cathode included in the second region (11b). The carbon-based cathode active material has an electrical resistance in the plane direction where graphite planes formed of carbon atoms are stacked that is lower than the electrical resistance in the stacking direction. The carbon-based cathode active material of the cathode included in the first region (11a) and / or the third region (11c) can achieve low electrical resistance and high electrical conductivity because a crystal plane having the same orientation as the plane direction (i.e., an ab-axis crystal plane) is aligned at a predetermined angle with respect to the cathode current collector. In contrast, the carbon-based cathode active material of the cathode included in the second region (11b) may exhibit relatively high electrical resistance and low electrical conductivity because it is not aligned or is aligned at a low angle or less frequently with respect to the cathode current collector compared to the carbon-based cathode active material of the first region (11a) and / or the third region (11c).

[0079] For example, the cathode included in the second region (11b) has a higher pore resistance than the cathode included in the first region (11a) and / or the third region (11c), and the deviation may be in the range of 0.05 Ω or more. Specifically, the cathode included in the second region (11b) has a higher pore resistance than the cathode included in the first region (11a) and / or the third region (11c), and the deviation is 0.06 Ω or more; 0.07 Ω or more; 0.08 Ω or more; 0.09 Ω or more; 0.1 Ω or more; 0.2 Ω or more; 0.5 Ω or more; 0.05 Ω to 2.0 Ω; 0.05 Ω to 1.5 Ω; 0.05 Ω to 1.2 Ω; 0.05 Ω to 1.0 Ω; The pore resistance may be in the range of 0.05 Ω to 0.9 Ω; 0.05 Ω to 0.75 Ω; 0.05 Ω to 0.5 Ω; 0.05 Ω to 0.4 Ω; 0.05 Ω to 0.3 Ω; 0.05 Ω to 0.2 Ω; 0.07 Ω to 0.5 Ω; 0.09 Ω to 0.5 Ω; 0.11 Ω to 0.25 Ω; 0.2 Ω to 2.0 Ω; 0.6 Ω to 1.5 Ω; 0.6 Ω to 1.1 Ω; or 0.11 Ω to 0.19 Ω. In this case, the pore resistance may be measured using an electrochemical impedance spectroscopy (EIS) device after fabricating a symmetric cell including a target cathode. The present invention can control the degree of degradation of the monocell included in the electrode assembly (10) to be uniform while maintaining high lifespan characteristics and cycle characteristics of the electrode assembly (10) by adjusting the pore resistance of the cathode included in the second region (11b) and the cathode included in the first region (11a) and / or the third region (11c) as described above.

[0080] The electrode assembly (10) can control the number of each monocell included in the first region (11a) to the third region (11c). Specifically, the monocell stack (11) of the electrode assembly (10) can satisfy the following Equation 2 when the number of each monocell included in the first region (11a), the second region (11b), and the third region (11c) is denoted as n1, n2, and n3, respectively:

[0081] [Equation 2]

[0082] 0.25 ≤ n2 / (n1+n3) ≤ 15.

[0083] The monocell stack (11) of the electrode assembly may satisfy the above Equation 2 in the range of 0.25 to 15. For example, the monocell stack (11) of the electrode assembly may satisfy the above Equation 2 in the range of 0.25 to 13; 0.25 to 11; 0.25 to 10; 0.25 to 9; 0.25 to 8; 0.25 to 6; 0.25 to 5; 0.25 to 3; 0.5 to 10; 0.5 to 7.5; 0.5 to 5; 0.3 to 2.5; 2.0 to 4.5; 0.9 to 4.5; or 0.3 to 4.5.

[0084] Equation 2 above is a parameter representing the ratio of monocells included in the center and outer parts of the electrode assembly (10). In order to maintain the electrical performance of the electrode assembly (10) while uniformizing the degree of degradation of all monocells included in the electrode assembly (10), the ratio of monocells included in the center and outer parts of the monocell stack (11) must be appropriately adjusted. By adjusting Equation 2 above to the range described above, the present invention can prevent a large number of monocells from being included in the center of the electrode assembly (10) due to a ratio greater than the upper limit, or a large number of monocells from being included in the outer part of the electrode assembly (10) due to a ratio lower than the lower limit. If the ratio of monocells included in the center increases, a large deviation in the degree of degradation between the center and outer parts of the electrode assembly (10) is induced, which causes a problem in which the lifespan characteristics of the electrode assembly (10) are significantly degraded. Furthermore, if the ratio of monocells included in the outer part of the electrode assembly (10) increases, there is a limitation in that the effect of increasing the lifespan of the electrode assembly (10) is negligible.

[0085] Additionally, the number of monocells (n2) included in the second region (11b) may be 5 to 35. For example, the number of monocells (n2) included in the second region (11b) may be 5 to 30; 5 to 25; 5 to 20; 5 to 15; 5 to 10; 10 to 35; 15 to 35; 20 to 35; 10 to 30; 15 to 30; or 18 to 29. By adjusting the number of monocells (n2) included in the second region (11b) to the range described above, the present invention can easily equalize the degree of degradation of the electrode assembly while maintaining high lifespan characteristics and cycle characteristics.

[0086] The average thickness of the negative active layer of the above-mentioned negative electrode (111b) can be controlled to a predetermined range. Since the negative active layer includes a negative active material that exhibits electrochemical activity during the charging and discharging of a secondary battery, the thickness of the negative active layer may increase when the content of the negative active material is increased to increase the charge and discharge capacity of the negative electrode. However, if the thickness of the negative active layer becomes excessively thick, it is not only difficult to control the crystal plane orientation of the carbon-based negative active material included in the negative active layer, but the lifespan of the negative electrode may be significantly reduced as volume changes due to the insertion and extraction of lithium ions during charging and discharging increase. Accordingly, the present invention can control the average thickness of the negative active layer to a range of 100 μm to 500 μm. For example, the average thickness of the negative active layer may be 100 μm to 450 μm; 100 μm to 400 μm; 100 μm to 350 μm; 100 μm to 300 μm; It can be adjusted to a range of 100 µm to 250 µm; 100 µm to 200 µm; 150 µm to 400 µm; 200 µm to 450 µm; 300 µm to 500 µm; 150 µm to 300 µm; 150 µm to 250 µm; or 150 µm to 220 µm.

[0087] Meanwhile, the electrode assembly (10) may have a stacked, stacked, or jelly-roll wound shape. Since an electrode assembly of this type exhibits high energy density within a limited space, it has the advantage of being highly useful in terms of energy density or output of a secondary battery.

[0088] The electrode assembly (10) may be embedded in a state connected to each lead of the positive and negative electrodes formed outside the pouch case. Specifically, the positive lead and the negative lead may be formed to extend from the inside to the outside of the pouch case. At this time, the positive lead and the negative lead may be structured to be drawn out to the outside of the pouch case, extending in the same direction or in opposite directions.

[0089] Meanwhile, the anode (112a), like the cathode (111a), includes an anode active layer containing an anode active material on at least one surface of the anode current collector.

[0090] Here, the cathode active material is a material capable of causing an electrochemical reaction and may include one or more of lithium metal compounds represented by the following chemical formulas 1 to 3 that are capable of reversibly intercalating and deintercalating lithium ions:

[0091] [Chemical Formula 1]

[0092] Li a [Ni b Co 1-b-c M 1 c ]O2

[0093] [Chemical Formula 2]

[0094] Li p [Mn 2-q M 2 q ]O4

[0095] [Chemical Formula 3]

[0096] LiFe 1-x M 3 x XO4

[0097] In the above chemical formulas 1 to 3,

[0098] M 1 It is one or more elements selected from W, Cu, Fe, V, Cr, Mn, Al, Mg, Ca, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ce, Nb, B, and Mo, and

[0099] M 2 is one or more elements selected from W, Cu, Fe, V, Cr, Ni, Al, Mg, Ca, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ce, Nb, B, and Mo, and

[0100] M 3It is one or more elements selected from W, Cu, Fe, V, Cr, Ni, Co, Mn, Al, Mg, Ca, Ti, Zr, Zn, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ce, Nb, B, and Mo, and

[0101] X is one or more elements selected from P, Si, S, As, and Sb, and

[0102] a, b, c, p, q, and x are 1.0≤a≤1.30, 0≤b<1, 0≤c≤0.4, 1.0≤p≤1.30, 0≤q≤1.0, and 0≤x≤0.8, respectively.

[0103]

[0104] The lithium metal oxide represented by Chemical Formula 1 above is a compound having a layered crystal structure, which facilitates the storage of lithium ions and possesses a high lithium ion diffusion rate, making it applicable as a cathode active material for high-capacity / high-output secondary batteries. The lithium metal oxide represented by Chemical Formula 1 above is a metal oxide containing nickel (Ni) and / or cobalt (Co) along with lithium, and in some cases, other transition metals (M 1 It may have a doped form. For example, the lithium metal oxide is LiCoO2, LiNiO2, Li(Ni 0.6 Co 0.2 Mn 0.2 )O2, Li(Ni 0.7 Co 0.15 Mn 0.15 )O2, Li(Ni 0.8 Co 0.1 Mn 0.1 )O2, Li(Ni 0.9 Co 0.05 Mn 0.05 )O2, Li(Ni 0.6 Co 0.2 Mn 0.1 Zr 0.1 )O2, Li(Ni 0.6 Co 0.2 Mn 0.15 Zr 0.05 )O2, Li(Ni 0.7 Co 0.1 Mn0.1 Zr 0.1 )O2, Li(Ni 0.6 Co 0.2 Al 0.2 )O2, Li(Ni 0.7 Co 0.15 Al 0.15 )O2, Li(Ni 0.8 Co 0.1 Al 0.1 )O2, Li(Ni 0.9 Co 0.05 Al 0.05 )O2, Li(Ni 0.6 Co 0.2 Al 0.1 Zr 0.1 )O2, Li(Ni 0.6 Co 0.2 Al 0.15 Zr 0.05 )O2 and Li(Ni 0.7 Co 0.1 Al 0.1 Zr 0.1 It may include one or more types of O2.

[0105] In addition, the lithium metal oxide represented by Chemical Formula 2 above has a spinel crystal structure, which is easily observed in general metal oxides. Since the spinel crystal structure contains various three-dimensional channels internally, it facilitates the insertion of lithium ions and thus possesses excellent output characteristics. The lithium metal oxide represented by Chemical Formula 2 above is a metal oxide containing manganese (Mn), and in some cases, other transition metals (M 2 It may have a doped form. For example, the lithium metal oxide is LiMn2O4, LiMn 1.7 Al 0.3 O4, LiMn 1.5 Al 0.5 It may include one or more types of O4.

[0106] The lithium metal oxide represented by Chemical Formula 3 above has an olivin structure and exhibits the best structural stability; therefore, it is a promising active material with excellent lifespan characteristics and superior advantages in all aspects of safety, including overcharging and over-discharging. In particular, the lithium iron phosphate compound is PO4 - Due to the strong bonding force, it exhibits excellent high-temperature stability and is more economical than LiCoO2, LiNiO2, or LiMn2O4 because it contains iron, which is resource-abundant and inexpensive. Furthermore, the lithium iron phosphate oxide has the advantage of having low toxicity, resulting in minimal environmental impact. This lithium metal oxide represented by Chemical Formula 3 is a phosphate containing iron (Fe) among transition metals, and in some cases, other transition metals (M 3 It may have a doped form. For example, the lithium metal oxide is LiFePO4, LiFe 0.8 Mn 0.2 PO4, LiFe 0.7 Mn 0.3 PO4, LiFe 0.5 Mn 0.5 PO4, LiFe 0.3 Mn 0.7 PO4, LiFe 0.2 Mn 0.8 It may include PO4, etc.

[0107] The above positive active layer may further include a conductive material, a binder, other additives, etc., along with the positive active material.

[0108] At this time, the conductive material may include one or more types of carbon black such as acetylene black, Denka black, Ketjen black, Super-P, furnace black, lamp black, and thermal black; graphene; carbon nanotubes and carbon fibers, but is not limited thereto.

[0109] For example, the above-mentioned positive active layer may contain carbon black, carbon nanotubes, carbon fibers, etc., as a conductive material, either alone or in combination.

[0110] At this time, the content of the conductive material may be 0.1 to 10 parts by weight per 100 parts by weight of the entire positive electrode active layer. Specifically, the conductive material may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 2 to 6 parts by weight, or 0.5 to 2 parts by weight per 100 parts by weight of the entire positive electrode active layer. By controlling the content of the conductive material within the above range, the present invention can prevent the reduction in charging capacity caused by an increase in the resistance of the positive electrode due to a low content of the conductive material. Furthermore, the present invention can prevent problems such as a decrease in charging capacity due to a reduction in the content of the positive electrode active material caused by an excessive amount of conductive material exceeding the above range, or an increase in electrical resistance due to an increase in the loading amount of the positive electrode active layer.

[0111] The above binder serves to bind the cathode active material, conductive material, and / or other additives together, and any binder having this function can be used without particular limitation. Specifically, the binder may include one or more of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVdF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene butadiene rubber (SBR), and fluororubber. As an example, the binder may include polyvinylidenefluoride.

[0112] In addition, the binder may be included in an amount of 1 to 10 weight percent based on the total weight of the anode active layer. Specifically, the binder may be included in an amount of 2 to 8 weight percent or 1 to 5 weight percent based on the total weight of the anode active layer.

[0113] The total thickness of the anode active layer is not particularly limited, but specifically may be in the range of 50㎛ to 300㎛, and more specifically may be in the range of 100㎛ to 200㎛; 80㎛ to 150㎛; 120㎛ to 170㎛; 150㎛ to 300㎛; 200㎛ to 300㎛; or 150㎛ to 190㎛.

[0114] In addition, the anode (112a) may be used as an anode current collector that has high conductivity without causing chemical changes in the battery. For example, the anode current collector may be a thin sheet or film containing stainless steel, aluminum, nickel, titanium, calcined carbon, etc., and in the case of aluminum or stainless steel, a surface treated with carbon, nickel, titanium, silver, etc. may be used. Furthermore, the average thickness of the current collector may be appropriately applied from 3㎛ to 500㎛, taking into account the conductivity and total thickness of the anode being manufactured.

[0115] Meanwhile, the cathode active layer of the above-mentioned cathode (111a) may optionally include a silicon-based cathode active material, a conductive material, a binder, other additives, etc., along with a carbon-based cathode active material, as needed.

[0116] The above silicon-based negative electrode active material is a material containing silicon (Si) as a main component, which can increase the charge / discharge capacity of the negative electrode. Examples of such silicon-based negative electrode active materials include silicon (Si), silicon carbide (SiC), silicon monoxide (SiO), or silicon dioxide (SiO2), and these may be included alone or used in combination in the negative electrode active layer. When silicon monoxide (SiO) and silicon dioxide (SiO2) are uniformly mixed or composited and included in the negative electrode active layer as the above silicon-based negative electrode active materials, they are silicon oxide (SiO2 q , provided that 0.8≤q≤2.5) can be expressed as.

[0117] In addition, the silicon-based negative electrode active material may be doped with Li, Mg, Al, Ca, or Ti, or form an alloy. Furthermore, when the silicon-based negative electrode active material contains oxygen (O), it may be surface-treated with a carbon coating layer or the like to suppress volume expansion during charging and simultaneously improve the electrical conductivity of the negative electrode active material, or it may be composited with carbon particles.

[0118] In addition, the silicon-based negative electrode active material may be included in an amount of 0.1 to 40 weight% based on the total weight of the negative electrode active layer. Specifically, the silicon-based negative electrode active material may be included in an amount of 0.5 to 20 weight%, 1 to 9 weight%, 5 to 15 weight%, 3 to 7 weight%, 11 to 19 weight%, 13 to 17 weight%, 15 to 20 weight%, 10 to 30 weight%, 20 to 40 weight%, 25 to 35 weight%, 15 to 25 weight%, or 9 to 22 weight% based on the total weight of the negative electrode active layer. By adjusting the content ratio of the silicon-based negative electrode active material included in the negative electrode active layer to the above range, the present invention can improve the charge capacity per unit mass while reducing lithium consumption and irreversible capacity loss during the initial charge and discharge of the secondary battery. In addition, by minimizing the volume change of the negative electrode active layer during charging and discharging of the secondary battery, the structural stability of the negative electrode active layer can be improved, thereby extending the lifespan of the secondary battery.

[0119] The above conductive material may include one or more types of carbon black such as acetylene black, Denka black, Ketjen black, Super-P, furnace black, lamp black, and thermal black; graphene; carbon nanotubes and carbon fibers, but is not limited thereto.

[0120] For example, the above-mentioned cathode active layer may contain carbon black, carbon nanotubes, carbon fibers, etc., as a conductive material, either alone or in combination.

[0121] At this time, the content of the conductive material may be 0.1 to 10 parts by weight per 100 parts by weight of the entire cathode active layer. Specifically, the conductive material may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 2 to 6 parts by weight, or 0.5 to 2 parts by weight per 100 parts by weight of the entire cathode active layer. By controlling the content of the conductive material within the above range, the present invention can prevent the decrease in charging capacity caused by an increase in the resistance of the cathode due to a low content of the conductive material. Furthermore, the present invention can prevent problems such as a decrease in charging capacity due to a decrease in the content of the cathode active material caused by an excessive amount of conductive material exceeding the above range, or an increase in electrical resistance due to an increase in the loading amount of the cathode active layer.

[0122] In addition, the binder is a component that assists in the bonding of the cathode active material and the conductive material, and the bonding to the current collector, and can be appropriately applied within a range that does not degrade the electrical properties of the cathode. For example, the binder may include one or more of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidenefluoride (PVdF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene butadiene rubber (SBR), and fluororubber.

[0123] The content of the binder may be 0.1 to 10 parts by weight per 100 parts by weight of the entire cathode active layer. Specifically, the binder may be 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 per 100 parts by weight of the entire cathode active layer. By controlling the content of the binder contained in the cathode active layer to the above range, the present invention can prevent the adhesion of the active layer from being reduced due to a low content of binder or the electrical properties of the cathode from being reduced due to an excessive amount of binder.

[0124] The above-mentioned negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, nickel, titanium, calcined carbon, etc. may be used, and in the case of copper or stainless steel, surface-treated carbon, nickel, titanium, silver, etc. may be used. In addition, the average thickness of the above-mentioned negative electrode current collector can be appropriately applied from 1 μm to 500 μm, taking into consideration the conductivity and total thickness of the negative electrode being manufactured.

[0125] In addition, the separator (111b, 112b, and 121b) 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. Specifically, the separator (111b, 112b, and 121b) may be one comprising one or more polymers selected from chemically resistant and hydrophobic polypropylene; polyethylene; and polyethylene-propylene copolymer. The separator (111b, 112b, and 121b) may have the form of a porous polymer substrate, such as a sheet or nonwoven fabric, containing the polymer described above, and in some cases, may have the form of a composite separator in which organic or inorganic particles are coated on the porous polymer substrate by an organic binder. Furthermore, the separator (111b, 112b, and 121b) may have an average pore diameter of 0.01㎛ to 10㎛ and an average thickness of 5㎛ to 300㎛.

[0126]

[0127] The electrode assembly according to the present invention has the above-described configuration, thereby enabling uniform degradation of the electrodes included in the electrode assembly, and thus has the advantage of excellent lifespan and capacitance characteristics.

[0128]

[0129] secondary battery

[0130] Furthermore, the present invention

[0131] The electrode assembly according to the present invention described above, and

[0132] A secondary battery comprising an electrolyte composition that impregnates the electrode assembly is provided.

[0133]

[0134] The secondary battery according to the present invention may be a lithium secondary battery. The lithium secondary battery includes a negative electrode according to the present invention and has the advantage of having excellent energy density as well as excellent lifespan and capacity characteristics.

[0135] At this time, since the electrode assembly has the same configuration as the electrode assembly described above, a detailed description is omitted.

[0136] The above electrolyte composition may include a non-aqueous organic solvent, a lithium salt, and an electrolyte additive.

[0137] The above-mentioned non-aqueous organic solvent can be applied without particular limitation as long as it is used in the industry for non-aqueous electrolytes. For example, as the above-mentioned non-aqueous organic solvent, aprotic organic solvents such as N-methyl-2-pyrrolidinone, ethylene carbonate (EC), propylene carbonate (PC), propylene carbonate, butylene carbonate, dimethyl carbonate (DMC), diethyl carbonate (DEC), gamma-butyrolactone, 1,2-dimethoxyethane (DME), tetrahydrofuran, 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolone, formamide, dimethylformamide, dioxolone, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate tryster, trimethoxymethane, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, ether, methyl propionicate (MP), ethyl propionicate (EP), and propyl propionicate (PP) may be used. It is possible.

[0138] In addition, the non-aqueous organic solvent used in the present invention may be used as a single type, or two or more types may be mixed in any combination or ratio according to the application. Among these, it is particularly desirable to mix propylene carbonate, ethylene carbonate, fluoroethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, etc., from the perspective of electrochemical stability against oxidation and reduction and chemical stability against heat or reaction with solutes.

[0139] The above lithium salts may be applied without particular limitation as long as they are used in the industry for non-aqueous electrolytes. Specifically, the above lithium salts include LiCl, LiBr, LiI, LiClO4, LiBF4, and LiB10 Cl 10 It may include one or more of LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, (CF3SO2)2NLi and (FSO2)2NLi.

[0140] The lower limit of the appropriate concentration range for using the above lithium salt is 0.5 mol / L or higher, specifically 0.7 mol / L or higher, more specifically 0.9 mol / L or higher, and the upper limit is 2.5 mol / L or lower, specifically 2.0 mol / L or lower, more specifically 1.5 mol / L or lower. If the concentration of the lithium salt is lower than 0.5 mol / L, the ion conductivity decreases, which may lead to a decrease in the cycle characteristics and output characteristics of the non-aqueous electrolyte battery. In addition, if the concentration of the lithium salt exceeds 2.5 mol / L, the viscosity of the electrolyte for the non-aqueous electrolyte battery increases, which may also lead to a decrease in ion conductivity and a decrease in the cycle characteristics and output characteristics of the non-aqueous electrolyte battery.

[0141] In addition, when a large amount of lithium salt is dissolved in a non-aqueous organic solvent at once, the temperature of the electrolyte may rise due to the heat of dissolution of the lithium salt. If the temperature of the non-aqueous organic solvent rises significantly due to the heat of dissolution of the lithium salt in this way, in the case of a lithium salt containing fluorine, decomposition is accelerated and there is a risk of hydrogen fluoride (HF) being generated. Hydrogen fluoride (HF) is undesirable because it causes degradation of battery performance. Therefore, the temperature at which the lithium salt is dissolved in the non-aqueous organic solvent is not particularly limited, but can be controlled to -20 to 80°C, and specifically to 0 to 60°C.

[0142] Furthermore, the above electrolyte additive may be included as an additional auxiliary component to improve the physical properties of the electrolyte composition. Electrolyte additives generally used in the non-aqueous electrolyte of the present invention may be added in any proportion. Specifically, examples include compounds having an overcharge prevention effect, a negative electrode film formation effect, and a positive electrode protection effect, such as cyclohexylbenzene, biphenyl, t-butylbenzene, carbonate, vinylethylene carbonate, difluoroanisole, fluoroethylene carbonate, propanesulfone, succinonitrile, and dimethylvinylene carbonate. In addition, it is also possible to use an electrolyte for a non-aqueous electrolyte battery by solidifying it with a gelling agent or a crosslinking polymer, as in the case of use in a non-aqueous electrolyte battery called a lithium polymer battery.

[0143]

[0144] The present invention will be explained in more detail below through examples and comparative examples.

[0145] However, the following examples and comparative examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and comparative examples.

[0146]

[0147] Examples 1–8 and Comparative Examples 1–2. Preparation of electrode assemblies

[0148] 1) Manufacture of cathode unit cells and half cells

[0149] Artificial graphite was prepared as a carbon-based cathode active material. In addition, styrene butadiene rubber (SBR) and carboxymethylcellulose (CMC) were prepared as binders, and carbon black (Super-P) was prepared as a conductive material.

[0150] A cathode slurry was prepared by mixing 97 wt% of artificial graphite; 1.5 wt% of carboxymethylcellulose (CMC) and styrene butadiene rubber (SBR) mixed in a 1:1 weight ratio; and 1.5 wt% of carbon black with water to obtain a solid content of 50%. Then, the prepared cathode slurry was applied onto a copper foil (thickness: 6 μm) being transported roll-to-roll (transport speed: 6 m / min) using a die coater.

[0151] After that, in order to manufacture cathode unit cells with different orientation degrees of carbon-based cathode active materials, magnets were placed on the upper and lower parts of a moving copper foil, and a magnetic field was applied to the cathode slurry for 5 to 11 seconds with a magnetic field strength as shown in Table 1 below.

[0152] A cathode slurry to which a magnetic field was applied was hot-air dried and rolled at a speed of 10 to 20 m / min at 50 to 60°C to produce a cathode with a cathode active layer (average thickness: about 180 ± 5 μm) provided on a cathode current collector.

[0153] X-ray diffraction spectroscopy (XRD) was performed on the cathode active layer of the fabricated cathode to measure the X-ray diffraction of the carbon-based cathode active material contained in the cathode active layer. The measurement conditions are as follows:

[0154] - Target: Cu(Kα line) graphite monochromator

[0155] - Slit: Diverging slit = 1 degree, Receiving slit = 0.1 mm, Scattering slit = 1 degree

[0156] - Measurement area: (110) plane: 76.5°<2θ<78.5° / (004) plane: 53.5°<2θ<56.0°.

[0157]

[0158] The orientation degree (OI) of the carbon-based cathode active material was calculated from the measured spectrum using Equation 1 below. The results are shown in Table 1 below:

[0159] [Equation 1]

[0160] OI= I 004 / I 110

[0161] In the above Equation 1,

[0162] I 110 represents the intensity of the peak indicating the (110) crystal plane of the carbon-based cathode active material during X-ray diffraction spectroscopy (XRD) measurement of the cathode active layer, and

[0163] I 004 represents the intensity of the peak indicating the (004) crystal plane of the carbon-based cathode active material during X-ray diffraction spectroscopy (XRD) measurement of the cathode active layer.

[0164]

[0165] Meanwhile, two cathodes with different applied magnetic field strengths were prepared for each, and a symmetric cell was fabricated by stacking them in the order of separator / cathode / separator / cathode / separator. Electrolyte was injected into the fabricated symmetric cell to completely immerse it, and the cell was mounted on an electrochemical impedance spectroscopy (EIS) device while secured to a jig. Subsequently, the impedance was measured in the range of 300 kHz to 300 MHz, and the measured data was fitted to determine the resistance (R) of the pores contained in the cathode active layer. pore ) was calculated. The results are shown in Table 1 below.

[0166]

[0167] Meanwhile, a cathode unit cell was obtained by placing a separator made of 12 to 16 μm polypropylene on one side of the manufactured cathode. In addition, a cathode half-cell was also manufactured by placing a separator made of 18 μm polypropylene on both sides of the cathode.

[0168] Magnetic field strength [G, gauss]OIR pore [Ω] Manufacturing Example 1015.73.27 Manufacturing Example 230008.822.45 Manufacturing Example 360005.032.32 Manufacturing Example 490003.192.07

[0169]

[0170] 2) Manufacturing of the anode unit cell

[0171] LiNi as a positive electrode active material 0.7 Co 0.1 Mn 0.1 Al 0.1 An anode slurry was prepared by mixing O296 wt%, carbon black as a conductive material, and polyvinylidene fluoride as a binder, 2.5 wt%, with N-methylpyrrolidone at a solid content of 50%.

[0172] An anode slurry prepared was applied onto an aluminum foil (thickness: 10~14㎛) that was being transported roll-to-roll (transport speed: 6 m / min) using a die coater, then dried with hot air, and an anode was manufactured by rolling at a speed of 30~40 m / min at 50~60℃.

[0173] An anode unit cell was obtained by placing a separator made of 12 to 16 μm polypropylene on one side of the manufactured anode.

[0174]

[0175] 3) Manufacture of electrode assembly

[0176] A monocell was obtained by sequentially stacking the previously manufactured cathode unit cell and anode unit cell, and a monocell stack was manufactured by sequentially stacking 40 of these monocells.

[0177] At this time, as shown in FIG. 1, the unit cells were arranged so that the separator provided in each unit cell faced forward, and a plurality of monocells were assembled such that a negative unit cell was placed at the front of the monocell stack. An electrode assembly was obtained by placing the previously prepared negative half-cell at the rear of the monocell stack.

[0178] At this time, ① the number of monocells included in the first to third regions of the electrode assembly; and ② the type of cathode unit cell included in each region were adjusted as shown in Table 2 below.

[0179] Region 1 Region 2 Region 3 Number of Monocells Type of Cathode Unit Cell Number of Monocells Type of Cathode Unit Cell Number of Monocells Type of Cathode Unit Cell Example 1 14 Unit cell of Manufacturing Example 3 12 Unit cell of Manufacturing Example 1 14 Unit cell of Manufacturing Example 3 Example 2 10 Unit cell of Manufacturing Example 3 20 Unit cell of Manufacturing Example 1 10 Unit cell of Manufacturing Example 3 Example 3 6 Unit cell of Manufacturing Example 3 28 Unit cell of Manufacturing Example 1 6 Unit cell of Manufacturing Example 3 Example 4 4 ​​Unit cell of Manufacturing Example 3 32 Unit cell of Manufacturing Example 1 4 Unit cell of Manufacturing Example 3 Example 5 1 Unit cell of Manufacturing Example 3 38 Unit cell of Manufacturing Example 1 1 Unit cell of Manufacturing Example 3 Example 6 17 Unit cell of Manufacturing Example 3 6 Unit cell of Manufacturing Example 1 17 Unit cell of Manufacturing Example 3 Example 7 10 Unit cell of Manufacturing Example 3 20 Unit cell of Manufacturing Example 2 10 Unit cell of Manufacturing Example 3 Example 8 10 Unit cell of Manufacturing Example 4 20 Unit cell of Manufacturing Example 2 10 Unit cell of Manufacturing Example 4 Comparative Example 1 110 Unit cell of Manufacturing Example 1 20 Unit cell of Manufacturing Example 1 10 Unit cell of Manufacturing Example 1 Comparative Example 2 10 Unit cell of Manufacturing Example 3 20 Unit cell of Manufacturing Example 3 10 Unit cell of Manufacturing Example 3

[0180] Experimental Example.

[0181] To evaluate the lifespan characteristics of the electrode assembly according to the present invention, the following experiment was performed.

[0182] The electrode assemblies prepared in Examples 1 to 8 and Comparative Examples 1 to 2 were inserted into a battery case, and an electrolyte composition was injected to produce a small pouch-type lithium secondary battery.

[0183] Here, the electrolyte composition used was an organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7 and LiPF6 was dissolved to a concentration of 1.2 M.

[0184] Each lithium secondary battery was activated by charging to 4.2V at a rate of 0.3C under CC-CV conditions at 25℃ and discharging to 2.5V at a rate of 0.3C under CC conditions.

[0185] One cycle was defined as charging each activated lithium secondary battery to 4.2V at a rate of 1.0C under CC-CV conditions at a temperature of 25°C and discharging to 2.5V at a rate of 1.0C under CC conditions, and one cycle of charge and discharge was performed for each lithium secondary battery prepared in the examples and comparative examples. At this time, the capacity was measured during charge and discharge to confirm the charge and discharge capacity of the first cycle. Subsequently, 499 charge and discharge cycles were performed on each lithium secondary battery to perform a total of 500 charge and discharge cycles. At this time, the charge and discharge capacity of the 500th cycle was confirmed during the final cycle. The charge and discharge capacity retention rate of the 500th cycle was calculated based on the measured charge and discharge capacity of the first cycle. The results are shown in Table 3 below.

[0186] Dose Retention Rate Example 1: Approx. 87% Example 2: Approx. 90% Example 3: Approx. 89% Example 4: Approx. 90% Example 5: Approx. 80% Example 6: Approx. 82% Example 7: Approx. 91% Example 8: Approx. 93% Comparative Example 1: Approx. 71% Comparative Example 2: Approx. 78%

[0187]

[0188] Looking at Table 3 above, it was confirmed that the secondary battery containing the electrode assembly of the example showed a high capacity retention rate of 85% or higher, whereas the secondary battery containing the electrode assembly of the comparative example showed a capacity retention rate of less than 80%.

[0189] This indicates that when the crystal plane characteristics of the carbon-based negative electrode active material contained in the outer and central parts of the electrode assembly, respectively, are controlled, the degradation of the monocell is induced uniformly.

[0190] From these results, it can be seen that the electrode assembly according to the present invention has excellent cycle characteristics and / or life characteristics.

[0191]

[0192] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art or those with ordinary knowledge in the art will understand that various modifications and changes can be made to the invention without departing from the technical features of the invention as described in the claims set forth below.

[0193] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

[0194]

[0195] [Explanation of the symbol]

[0196] 10: Electrode assembly

[0197] 11: Monocell stack 11a: First region

[0198] 11b: Second area 11c: Third area

[0199] 110: Monocell 111: Cathode unit cell

[0200] 111a and 121a: Cathode 111b and 121b: Separator

[0201] 112: Positive unit cell

[0202] 112a: Anode 112b: Separator

[0203] 120: Half-cell

Claims

1. A monocell stack comprising a plurality of monocells arranged in the thickness direction, each monocell comprising a unit cell having a stacked separator and a cathode and a unit cell having a stacked separator and an anode, and It includes a half cell positioned at the rear of the monocell stack, having a structure in which a separator, a cathode, and a separator are stacked; The above cathode is formed on at least one surface of a cathode current collector and includes a cathode active layer comprising a carbon-based cathode active material; The above monocell stack is divided into first to third regions from the front to the rear where the monocells are arranged; An electrode assembly in which one or more of the cathodes included in the first region and the cathodes included in the third region have an orientation degree (OI) represented by Equation 1 below, when analyzed by X-ray diffraction of the cathode active layer, that is smaller than the orientation degree (OI) of the cathode included in the second region: [Equation 1] OI= I 004 / I 110 In the above Equation 1, I 110 represents the intensity of the peak indicating the (110) crystal plane of the carbon-based cathode active material during X-ray diffraction spectroscopy (XRD) measurement of the cathode active layer, and I 004 represents the intensity of the peak indicating the (004) crystal plane of the carbon-based cathode active material during X-ray diffraction spectroscopy (XRD) measurement of the cathode active layer.

2. In Paragraph 1, One or more of the cathodes included in the first region and the cathodes included in the third region are electrode assemblies having an orientation degree (OI) in the range of 0.5 to 15.

3. In Paragraph 1, An electrode assembly having a ratio of 105% to 1,000% based on the orientation degree (OI) of the cathode included in the second region or the orientation degree (OI) of the cathode included in the first region or the cathode included in the third region.

4. In Paragraph 1, The above monocell stack is an electrode assembly satisfying the following Equation 2, where the number of monocells included in the first region, the second region, and the third region are denoted as n1, n2, and n3, respectively: [Equation 2] 0.25 ≤ n2 / (n1+n3) ≤ 15.

5. In Paragraph 4, An electrode assembly in which the number of monocells (n2) included in the second region is 5 to 35.

6. In Paragraph 1, The cathode included in the second region above is an electrode assembly having a greater pore resistance than the cathode included in the first region or the third region.

7. In Paragraph 6, The cathode included in the second region is an electrode assembly having a pore resistance deviation of 0.05 Ω or more with respect to the cathode included in the first region or the third region.

8. In Paragraph 1, The cathodes included in the first and third regions are electrode assemblies having a tortuosity in the range of 2.0% to 8.0%.

9. In Paragraph 1, The above carbon-based negative electrode active material is an electrode assembly comprising one or more of natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, carbon microbeads, mesophase pitch, and graphitized coke.

10. In Paragraph 1, An electrode assembly in which the average thickness of the above-mentioned cathode active layer is in the range of 100㎛ to 500㎛.

11. Electrode assembly according to paragraph 1, and A secondary battery comprising an electrolyte composition that impregnates the above electrode assembly.

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