Electrode assembly

Abstract

The present application can provide an electrode assembly and its uses. In the present application, it is possible to provide a structure of an electrode assembly that can maximize the capacity per unit area of the positive electrode with respect to the negative electrode while effectively achieving an N / P ratio exceeding 1 in the entire region where the positive electrode and the negative electrode face each other. Along with this, in the present application, it is possible to provide an electrode assembly that can maximize the energy density per unit volume and per unit weight even under an N / P ratio exceeding 1. The present application can also provide a method for manufacturing the electrode assembly as described above and its uses.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0086635 filed on July 14, 2022, and all contents disclosed in the corresponding Korean patent application are incorporated herein by reference in their entirety.

[0002] This application relates to an electrode assembly.

Background Art

[0003] Energy storage technology has been expanding its application areas, such as mobile phones, video cameras, notebook personal computers (PCs), and electric vehicles.

[0004] One of the research fields of energy storage technology is rechargeable secondary batteries, and research and development are underway to improve the capacity density and energy density of such secondary batteries.

[0005] Secondary batteries include an electrode assembly having a structure in which a positive electrode and a negative electrode are laminated with a separator interposed therebetween. When designing the electrode assembly, the negative electrode is made wider and has a higher loading than the positive electrode, which is a design for making the so-called N / P ratio greater than 1.

[0006] The N / P ratio is the ratio of the capacities per unit area of the negative electrode and the positive electrode, and is a value obtained by dividing the capacity per unit area of the negative electrode by the capacity per unit area of the positive electrode.

[0007] The reason for designing the N / P ratio to be greater than 1 is that during the charging process, if the negative electrode does not face the positive electrode or the loading of the negative electrode is low, so that the amount of lithium that can be accommodated in the negative electrode is smaller than the amount of lithium generated at the positive electrode, problems such as lithium electroplating may occur.

[0008] When the N / P ratio is less than 1, short circuits in the battery due to needle-shaped lithium deposition can occur, and since all the lithium generated at the positive electrode cannot be utilized during discharge, a decrease in efficiency and a reduction in capacity can occur. Also, the electrolyte can decompose on the surface of the deposited lithium, causing film growth, which can lead to a decrease in efficiency and an increase in resistance.

[0009] Normally, the negative electrode and the positive electrode are manufactured by coating a slurry containing an electrode active material on the surface of a current collector and subjecting it to drying and rolling processes, and the coated slurry forms the active material layer of the electrode.

[0010] By the way, as exemplarily shown in FIG. 1, depending on the characteristics of the slurry, in the process of coating the slurry on the current collector 100 to form the active material layer 101, sliding portions (S in FIG. 1) where the thickness increases or decreases along the coating direction (the direction of the arrow in FIG. 1) at the start and end sites of the coating occur.

[0011] The degree of inclination and width of the sliding portion are determined by the composition of the slurry. When forming an electrode assembly with the positive electrode and the negative electrode facing each other, an N / P ratio exceeding 1 must be achieved even at the sites where the sliding portions of the positive electrode and the negative electrode exist. However, since it is not easy to adjust the degree of inclination and width of the sliding portion, it is also not easy to adjust the N / P ratio, which is a problem.

[0012] Accordingly, it is a difficult problem to manufacture an electrode assembly such that the N / P ratio is greater than 1 in the entire region where the negative electrode and the positive electrode face each other.

[0013] Since it is important to achieve an N / P ratio exceeding 1 in general, an excessive capacity per unit area of the negative electrode is applied more than necessary during electrode design.

[0014] In such a case, the N / P ratio can be achieved as desired. However, surplus portions that are not actually utilized during charge and discharge of the secondary battery in the negative electrode will occur, unnecessarily increasing the volume and weight of the electrode assembly or the secondary battery, and showing inefficient results in terms of energy density.

SUMMARY OF THE INVENTION

PROBLEMS TO BE SOLVED BY THE INVENTION

[0015] The present application relates to an electrode assembly and its use. One object of the present application is to provide a structure of an electrode assembly that can effectively achieve an N / P ratio exceeding 1 in all regions where the positive electrode and the negative electrode face each other, while maximizing the capacity per unit area of the positive electrode with respect to the negative electrode. Along with this, another object of the present application is to provide an electrode assembly that can maximize the energy density per unit volume and per unit weight even under an N / P ratio exceeding 1.

[0016] Another object of the present application is to provide a method for manufacturing the electrode assembly as described above.

[0017] Another object of the present application is to provide a use of the electrode assembly as described above.

MEANS FOR SOLVING THE PROBLEMS

[0018] The present application relates to an electrode assembly.

[0019] The electrode assembly of the present application includes a negative electrode; a positive electrode and a separator, wherein the negative electrode and the positive electrode are laminated with the separator interposed therebetween, the negative electrode and the positive electrode each include a current collector layer and an active material layer present at least between the current collector layer and the separator, each of the negative electrode and the positive electrode has a first end portion where a tab portion is formed and a second end portion on the opposite side of the first end portion, the negative electrode and the positive electrode are laminated so that their first end portions face each other, or one of the first end portions faces the other second end portion, A slitting portion is formed in one of the first and second end portions of the negative electrode in the active material layer, and a sliding portion is formed in the other active material layer. The active material layers at both end portions of the positive electrode are each located inside the active material layers at both end portions of the negative electrode facing each other. The ratio I2 / I1 of the distance I1 between the positive electrode active material layer and the negative electrode active material layer at the end of the negative electrode where the slitting portion is formed to the distance I2 between the positive electrode active material layer and the negative electrode active material layer at the end of the negative electrode where the sliding portion is formed can be in the range of 0.5 to 10.

[0020] In the electrode assembly, the active material layer of the negative electrode may be thicker than the active material layer of the positive electrode.

[0021] In the electrode assembly, a sliding portion may be formed in the active material layer at the end portion of the positive electrode facing the end portion where the slitting portion of the negative electrode is formed.

[0022] In the electrode assembly, the surface of the sliding portion of the active material layer of the positive electrode may be a cut surface.

[0023] In the electrode assembly, a slitting portion may be formed in the active material layer of the positive electrode at the end opposite to the end where the sliding portion of the active material layer of the positive electrode is formed.

[0024] In the electrode assembly, the slitting portion of the active material layer of the positive electrode can exist inside the sliding portion of the active material layer of the negative electrode.

[0025] The electrode assembly can be designed to satisfy the following formula 1.

[0026] [Formula 1] T N / tanθ1≦I2

[0027] In formula 1, T Nis the thickness of the negative electrode active material layer, θ1 is the inclination angle of the sliding portion of the negative electrode, and I2 is the distance between the positive electrode active material layer and the negative electrode active material layer at the end of the negative electrode where the sliding portion is formed.

[0028] In the above, tanθ1 can be in the range of 0.001 to 10.

[0029] The electrode assembly can be designed to further satisfy the following formula 2.

[0030] [Formula 2] I2 ≦ T N / sinθ1

[0031] In formula 2, T N is the thickness of the negative electrode active material layer, θ1 is the inclination angle of the sliding portion of the negative electrode, and I2 is the distance between the positive electrode active material layer and the negative electrode active material layer at the end of the negative electrode where the sliding portion is formed.

[0032] A second sliding portion may be formed on the positive electrode active material layer at the opposite end of the end where the sliding portion of the positive electrode active material layer is formed in the electrode assembly.

[0033] In the above, the surface of the second sliding portion of the positive electrode active material layer can be a cut surface.

[0034] The electrode assembly can be designed to satisfy the following formula 3.

[0035] [Formula 3] T N / tanθ1 ≦ I2 + T P / tanθ2

[0036] In formula 3, T N is the thickness of the negative electrode active material layer, θ1 is the inclination angle of the sliding portion of the negative electrode, and I2 is the distance between the positive electrode active material layer and the negative electrode active material layer at the end of the negative electrode where the sliding portion is formed, and T P is the thickness of the positive electrode active material layer, and θ2 is the inclination angle of the second sliding portion of the positive electrode.

[0037] The electrode assembly can be designed to further satisfy the following formula 4.

[0038] [Formula 4] I2 + T P / tanθ2 ≤ T N / sinθ1

[0039] In formula 4, T N is the thickness of the negative electrode active material layer, θ1 is the inclination angle of the sliding part of the negative electrode, I2 is the distance between the positive electrode active material layer and the negative electrode active material layer at the end of the negative electrode where the sliding part is formed, and T P is the thickness of the positive electrode active material layer, and θ2 is the inclination angle of the second sliding part of the positive electrode.

[0040] The electrode assembly can be designed to further satisfy the following formula 5.

[0041] [Formula 5] θ2 / θ1 > 1

[0042] In formula 5, θ1 is the inclination angle of the sliding part of the negative electrode, and θ2 is the inclination angle of the second sliding part of the positive electrode.

[0043] In the electrode assembly, the negative electrode can further include an active material layer formed on the side opposite to the side facing the separator of the current collector layer. In such a case, the active material layer formed on the side opposite to the side facing the separator of the current collector layer of the negative electrode, the current collector layer, and the active material layer existing between the separator can have a symmetric structure.

[0044] In the electrode assembly, the positive electrode can further include an active material layer formed on the side opposite to the side facing the separator of the current collector layer. In such a case, the active material layer formed on the side opposite to the side facing the separator of the current collector layer of the positive electrode, the current collector layer, and the active material layer existing between the separator can have a symmetric structure.

[0045] This application also relates to a secondary battery including the electrode assembly and the electrolyte.

Advantages of the Invention

[0046] This application can provide an electrode assembly and its uses. In this application, it is possible to provide a structure of an electrode assembly that can maximize the capacity per unit area of the positive electrode with respect to the negative electrode while effectively achieving an N / P ratio exceeding 1 in the entire region where the positive electrode and the negative electrode face each other. Accordingly, in this application, it is possible to provide an electrode assembly that can maximize the energy density per unit volume and per unit weight even under an N / P ratio exceeding 1. This application can also provide a method for manufacturing the electrode assembly as described above and its uses.

Brief Description of the Drawings

[0047]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Figure 8

Figure 9

Figure 10

Figure 11

Figure 12

Explanation of Reference Numerals

[0048] 200: Separation membrane 300: Negative electrode 400: Positive electrode 100, 103, 104: Current collector layer 101, 102, 301, 302, 401, 402: Active material layer S: Sliding portion 10: Starting point of the active material layer NC: Plain portion 1011: Side surface of the slitting portion

Embodiments for Carrying Out the Invention

[0049] As used herein, the term "sliding portion" means a region of the active material layer in a cross-section of an electrode including a current collector layer and an active material layer formed on at least one surface of the current collector layer, where the thickness of the active material layer substantially increases or decreases along the length direction of the current collector layer. The increase or decrease in the thickness may be made at a constant ratio or may not be at a constant ratio.

[0050] As used herein, the term "normal thickness region" means a region in a cross-section of the electrode where the thickness of the active material layer is substantially maintained constant along the length direction of the current collector layer.

[0051] The electrode means a positive electrode or a negative electrode.

[0052] The cross-section of the electrode means a cut surface when the electrode is cut in a direction parallel to the direction connecting the end where the plain portion of the electrode exists and the opposite end from the end where the plain portion exists when observing the electrode from the front, and parallel to the normal of the surface of the current collector layer. Such a cut surface may be a virtual cut surface or may be an actual cut surface.

[0053] Hereinafter, in the description of the electrode assembly in this specification, the positional relationship between the active material layers of the positive electrode and the negative electrode may be a relationship based on the cross-section of the electrode.

[0054] FIG. 2 is a drawing exemplarily showing a cross-section of the electrode. As shown in FIG. 2, the electrode of the present application may include a current collector layer 100 and active material layers 101 and 102 formed on one or both surfaces thereof. At this time, the active material layers 101 and 102 are formed such that there is a portion (so-called plain portion) where the active material layers 101 and 102 are not formed at at least one of both ends of the current collector layer 100. Such a plain portion can form a tab portion described later. The plain portion may be formed at both ends of the electrode as shown in the drawing, or may be formed only at one of the ends of the electrode. When plain portions exist at both ends of the electrode, the cutting may be made parallel to the direction connecting both ends where the plain portions of the electrode exist.

[0055] FIG. 3 is an example when the electrode of FIG. 2 is observed from the front (the surface on which the active material layer 101 is formed). In FIG. 3, the dotted line is a cutting line for observing the cross-section of the electrode. As shown by the dotted line in FIG. 3, the cutting is parallel to the direction connecting the end where the plain portion of the electrode exists and the end opposite to the end where the plain portion exists when the electrode is observed from the front (or the direction connecting both ends where the plain portion of the electrode exists), and is also parallel to any one side of the electrode, and can be made in a direction parallel to the normal of the surface of the current collector layer.

[0056] The length direction of the current collector layer may mean a direction parallel to the current collector layer in the cross-section of the electrode (for example, the direction of the arrow in FIG. 2).

[0057] Generally, an electrode such as a negative electrode or a positive electrode is manufactured by coating a slurry containing an electrode active material on one or both surfaces of a current collector layer and performing drying and rolling processes, and the coated slurry forms an active material layer of the electrode.

[0058] As shown in FIG. 2, in such an electrode, due to the characteristics of the slurry, a portion where the thickness of the active material layers 101 and 102 substantially increases or decreases along the length direction of the current collector layer 100 (the direction of the arrow in FIG. 2) (for example, the portion indicated by S in FIG. 2) will occur.

[0059] In this specification, a portion of the active material layer where the thickness substantially increases or decreases as described above can be designated as a sliding portion. The sliding portion does not necessarily occur only in the coating process of the slurry, and the sliding portion may be formed by, for example, eating, cutting, or non-contact cutting described later.

[0060] Also, the substantial increase or decrease in thickness as described above means that, with the starting points of the active material layers 101 and 102 in the cross-section of the electrode (for example, 10 in FIG. 2) as the origin, the distance from the origin to any point of the active material layers 101 and 102 measured along the length direction of the current collector layer is taken as the value of the x-axis, and the thickness of the active material layers 101 and 102 at the corresponding distance point is taken as the value of the y-axis, and when a graph is drawn, it means that the absolute value of the slope of the corresponding graph is 0.001 or more. The length of the x-axis and the thickness of the y-axis have the same unit. When the graph is not a straight line, the slope can be the differential value at the corresponding point. The absolute value of the slope in the sliding portion may be, in other examples, 0.002 or more, 0.004 or more, 0.006 or more, 0.008 or more, 0.01 or more, 0.02 or more, 0.04 or more, 0.06 or more, 0.08 or more, 0.1 or more, 0.12 or more, 0.14 or more, 0.16 or more, 0.18 or more, or 0.2 or more, or about 10 or less, 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.8 or less, 0.6 or less, 0.4 or less, 0.2 or less, 0.1 or less, 0.08 or less, 0.06 or less, 0.04 or less, 0.02 or less, 0.01 or less, 0.008 or less, 0.006 or less, 0.004 or less, or 0.002 or less.

[0061] On one hand, when observing the active material layers 101 and 102 in the electrode cross-section of FIG. 2 along the length direction of the current collector (the direction of the arrow in FIG. 2) starting from the origin 10, there is a region where the thickness of the active material layers 101 and 102 is substantially maintained constant from the point where the sliding part ends to before the sliding part of the other end starts. Such a region becomes the normal thickness region. In the normal thickness region, the absolute value of the slope can be within the range of about 0 or more and less than 0.001. The upper limit of the absolute value of the slope may be about 0.0008 or less, 0.0006 or less, 0.0004 or less, or 0.0002 or less in other examples.

[0062] The electrode assembly of the present application may at least include a negative electrode, a positive electrode, and a separator. The negative electrode and the positive electrode may be included in the electrode assembly in a stacked state with the separator interposed therebetween. FIG. 4 is a drawing showing a form in which a negative electrode 300 and a positive electrode 400 are stacked with a separator 200 interposed therebetween.

[0063] As shown in FIG. 4, the electrode assembly may include one each of a separator 200, a negative electrode 300, and a positive electrode 400, or may include two or more of any one or more of them. For example, as exemplarily shown in FIG. 5, the electrode assembly may include a plurality of two or more unit structures stacked in the order of a negative electrode 300, a separator 200, and a positive electrode 400.

[0064] The negative electrode of the electrode assembly may include a current collector layer and an active material layer formed on at least one surface of the current collector layer. The positive electrode may also include a current collector layer and an active material layer formed on at least one surface of the current collector layer.

[0065] FIG. 6 exemplarily shows the structure of a negative electrode in which the active material layers 301 and 302 are formed on both surfaces of the current collector layer 103. In FIG. 6, the active material layers 301 and 302 are formed on both surfaces of the current collector layer 103, but the active material layer may be formed on only one surface of the current collector layer.

[0066] The positive electrode may also be formed in a form similar to that of the negative electrode.

[0067] A structure in which a negative electrode having a form as shown in FIG. 6 and a positive electrode having such a form are laminated with a separator therebetween is exemplarily shown in FIG. 7, and such a structure can sequentially include a negative electrode active material layer 302, a negative electrode current collector layer 103, a negative electrode active material layer 301, a separator 200, a positive electrode active material layer 401, a positive electrode current collector layer 104, and a positive electrode active material layer 402.

[0068] In the electrode assembly, the negative electrode and the positive electrode can each include a current collector layer (103, 104 in FIG. 7) and an active material layer (301, 401 in FIG. 5) existing at least between the current collector layer (103, 104 in FIG. 7) and the separator (200 in FIG. 7).

[0069] The negative electrode and the positive electrode can each have a first end portion where a tab portion is formed and a second end portion on the opposite side of the first end portion.

[0070] The tab portion can mean the aforementioned blank portion (the region of the current collector layer where the active material layer is not formed), and this site can be the site where the tab is adhered in a tab welding process or the like. In another example, the tab portion can mean the site where the electrode is electrically connected to the outside. Such blank portions may be formed at both end portions of the electrode, or may be formed only at one end portion of the electrode. FIG. 8 shows a case where blank portions NC are formed at both ends of an electrode in which active material layers 101 and 102 are formed on both sides of a current collector layer 100. When blank portions are formed at both ends of the electrode as shown in FIG. 8, either one of the two blank portions can be designated as the first end portion, and the opposite side can be designated as the second end portion. In one example, the site where the tab is attached or electrically connected to the outside through tab welding or the like can be designated as the first end portion.

[0071] In the electrode assembly, the negative electrode and the positive electrode may be stacked so that their first end portions face each other. In another example, they may be stacked so that the first end portion of either the negative electrode or the positive electrode faces the second end portion of the other. When it is said that two certain parts face each other as described above, it means that when observing the electrodes along the normal direction of the surface of the separator 200 in structures such as those shown in FIGS. 4, 5, and 7, the parts overlap and at least partially cover each other.

[0072] In the electrode assembly of the present application having the above structure, a slitting portion may be formed in one of the active material layers of either the first or second end portion of the negative electrode, and a sliding portion may be formed in the other active material layer. A normal thickness region may be formed between the slitting portion and the sliding portion in the negative electrode.

[0073] The slitting portion means a portion formed such that the extension direction of the side surface of the end portion of the active material layer forms an angle within ±5 degrees, ±4 degrees, ±3 degrees, ±2 degrees, or ±1 degree with the normal of the surface of the current collector layer in the cross-section of the electrode, or the extension direction of the side surface is substantially parallel to the normal of the surface of the current collector layer.

[0074] Such a slitting portion can be formed by a cutting process such as a slitting or notching process. At this time, the cross-section of the electrode is the same as the cross-section of the electrode in the process of explaining the sliding portion and the normal thickness region.

[0075] As described above, for an electrode that has undergone slurry coating, drying, and rolling, sliding portions are usually formed at both ends, and its cross-section is shown in the form as in FIG. 9. That is, as exemplarily shown in FIG. 9, due to the characteristics of the slurry, in the process of coating the slurry on the current collector 100 to form the active material layers 101 and 102, sliding portions are generated at the start and end sites of the coating, where the thickness increases or decreases along the coating direction or the length direction of the current collector layer 100 (the bidirectional arrow direction in FIG. 9) (S in FIG. 9).

[0076] Thus, by cutting one of the two end portions formed with the sliding portion through a cutting process such as a slitting or notching process, an electrode can be formed in which one end portion is the sliding portion and the other end portion is the slitting portion.

[0077] For example, when cutting is performed in the dotted line direction along the direction of the one-way arrow in FIG. 9, as shown in FIG. 10, an electrode is formed in which one end portion is the sliding portion and the other end portion is the slitting portion.

[0078] In the electrode of FIG. 10, the extending direction of the side surface 1011 of the active material layer at the end portion that is the slitting portion is substantially parallel to the normal line (the direction of the one-way arrow) of the surface of the current collector layer.

[0079] In the electrode assembly of the present application, the active material layers at both end portions of the positive electrode can be located inside the active material layers at both end portions of the negative electrode facing each other.

[0080] The statement that the active material layers at both end portions of the positive electrode are located inside the active material layers at both end portions of the negative electrode facing each other means that when the electrode assembly is observed from the normal direction of the surface of the separator, the active material layer of the negative electrode is formed such that both end portions extend further than the active material layer of the positive electrode.

[0081] That is, as exemplified in FIGS. 11 and 12, when the electrode assembly is observed along the normal direction of the surface of the separator 200, the active material layer 301 of the negative electrode is formed to extend further than the active material layer 401 of the positive electrode along the length direction of the current collector layers 103 and 104. Therefore, I1 and I2 in FIGS. 11 and 12 each exceed 0. Such an arrangement can effectively prevent the phenomenon in which the N / P ratio becomes less than 1 (hereinafter, referred to as the N / P inversion phenomenon).

[0082] In one example, the active material layer 301 of the negative electrode may be formed with a larger area than the active material layer 401 of the positive electrode.

[0083] In one example, the ratio I2 / I1 of the distance (I1 in FIGS. 11 and 12) between the positive electrode active material layer 401 and the negative electrode active material layer 301 at the end of the negative electrode where the slitting portion is formed in the cross-section of the electrode to the distance (I2 in FIGS. 11 and 12) between the positive electrode active material layer 401 and the negative electrode active material layer 301 at the end of the negative electrode where the sliding portion is formed may be in the range of 0.5 to 10.

[0084] In other examples, the ratio I2 / I1 may be 1 or more, 1.5 or more, 2 or more, 2.5 or more, 3 or more, 4 or more, 5 or more, 6 or more, or 7 or more, or about 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2.5 or less, 2 or less, 1.5 or less, or 1 or less. Under such a ratio, an electrode assembly can be provided that effectively prevents the N / P inversion phenomenon while ensuring a high energy density.

[0085] In the electrode assembly, the active material layer of the negative electrode may also be formed to be thicker than the active material layer of the positive electrode, thereby providing an electrode assembly that effectively prevents the N / P inversion phenomenon while ensuring a high energy density. The thickness of each active material layer above is the thickness in the normal thickness region. When the thickness in the normal thickness region is not somewhat constant, the corresponding thickness means the average thickness of the corresponding normal thickness region. Although not particularly limited, the ratio (TN / TP) of the thickness TN of the active material layer of the negative electrode to the thickness TP of the active material layer of the positive electrode may be about more than 1 and 5 or less. In other examples, the ratio (TN / TP) may be about 4.5 or less, 4 or less, 3.5 or less, 3 or less, 2.5 or less, 2 or less, or 1.5 or less.

[0086] In the electrode assembly, a sliding portion may be formed in the active material layer of the end portion of the positive electrode that faces the end portion where the slitting portion of the negative electrode is formed. By having such a configuration, it is possible to provide an electrode assembly that effectively prevents the N / P inversion phenomenon while ensuring a high energy density.

[0087] FIGS. 11 and 12 are drawings exemplarily showing an electrode assembly having such a configuration. The drawings show a case where the active material layers 301 and 401 are formed only between the current collectors 103 and 104 and the separator 200, but the active material layers 301 and 401 may also be formed on the opposite sides of the respective current collector layers 103 and 104.

[0088] In FIGS. 11 and 12, the inclined surfaces (e.g., S N , S P etc.) of the sliding portion are shown as being in a linear form, but this is shown for the convenience of explaining the electrode assembly of the present application, and the inclined surface may not be in a linear form but in a curved form (e.g., a bulging curve or a concave curve form) or other forms.

[0089] Referring to FIGS. 11 and 12, a slitting portion is formed at the right end portion of the negative electrode active material layer 301, and a sliding portion is formed at the left end portion. A sliding portion is formed at the right end of the positive electrode active material layer 401 that faces the end where the slitting portion is formed.

[0090] FIG. 11 shows one aspect of the electrode assembly of the present application, in which a slitting portion is formed in the active material layer 401 of the positive electrode at the end opposite to the end (the right end in FIG. 11) where the sliding portion of the active material layer 401 of the positive electrode is formed.

[0091] In such a structure, the slitting portion of the active material layer 401 of the positive electrode can be located inside the sliding portion of the active material layer 301 of the negative electrode.

[0092] Referring to the structure of FIG. 11, the fact that the slitting portion of the active material layer 401 of the positive electrode exists inside the sliding portion of the active material layer 301 of the negative electrode means that the following formula 1 is satisfied.

[0093] [Formula 1] T N / tanθ1 ≦ I2

[0094] In formula 1, T N is the thickness of the active material layer of the negative electrode, which is the thickness of the normal thickness region of the negative electrode active material layer, θ1 is the inclination angle of the sliding portion of the negative electrode active material layer, and I2 is the distance between the active material layer of the positive electrode and the active material layer of the negative electrode at the end of the negative electrode where the sliding portion is formed.

[0095] The above T N , θ1 and I2 are shown in FIG. 11.

[0096] The inclined surface S of the negative electrode active material layer (301 in FIG. 11) for obtaining θ1 N is, as shown in the drawing, the angle formed by the straight line connecting the starting point and the ending point of the sliding portion and the length direction of the current collector layer 103. Actually, the inclined surface of the sliding portion may or may not be in a linear form as shown in FIG. 11. However, even when it is not in a linear form, θ1 is obtained based on a virtual straight line when calculating.

[0097] In the above formula 1, T N / tanθ1 is the width of the sliding portion of the negative electrode active material layer 301 indicated by W N in FIG. 11.

[0098] By forming the active material layers 301 and 401 so that formula 1 is satisfied, it is possible to stably prevent the N / P inversion phenomenon and design the electrode assembly to exhibit a high energy density.

[0099] In the above, tanθ1 can have a value within the range of 0.001 to 10. In other examples, tanθ1 can be 0.002 or more, 0.004 or more, 0.006 or more, 0.008 or more, 0.01 or more, 0.02 or more, 0.04 or more, 0.06 or more, 0.08 or more, 0.1 or more, 0.12 or more, 0.14 or more, 0.16 or more, 0.18 or more, or 0.2 or more, or can be about 9 or less, 8 or less, 7 or less, 6 or less, 5 or less, 4 or less, 3 or less, 2 or less, 1 or less, 0.8 or less, 0.6 or less, 0.4 or less, 0.2 or less, 0.1 or less, 0.08 or less, 0.06 or less, 0.04 or less, 0.02 or less, 0.01 or less, 0.008 or less, 0.006 or less, 0.004 or less, or 0.002 or less.

[0100] The embodiment of FIG. 11 may further satisfy the following formula 2.

[0101] [Formula 2] I2 ≦ T N / sinθ1

[0102] In formula 2, T N , the meanings of θ1 and I2 are the same as those in the case of formula 1.

[0103] By further satisfying formula 2, the effects intended in this application can be further improved.

[0104] In another embodiment of the present application, as shown in FIG. 12, a second sliding portion may be formed in the positive electrode active material layer 401 at the opposite end (the left end in FIG. 12) of the end (the right end in FIG. 12) where the sliding portion of the positive electrode active material layer 401 is formed.

[0105] In such a case, the electrode assembly can be designed so that the following formula 3 is satisfied.

[0106] [Formula 3] T N / tanθ1 ≦ I2 + T P / tanθ2

[0107] In formula 3, T N, θ1 and I2 are as defined in Formula 1 and Formula 2, and T P is the thickness of the positive electrode active material layer, and θ2 is the inclination angle of the second sliding portion of the positive electrode active material layer.

[0108] As described above, the meaning of the thickness TP of the positive electrode active material layer is the thickness of the normal thickness region of the positive electrode active material layer, similar to the thickness TN of the negative electrode active material layer in Formula 1 and Formula 2. Also, the inclination angle θ2 of the second sliding portion of the positive electrode active material layer can be obtained in accordance with the method of obtaining θ1 in Formula 1 and Formula 2.

[0109] The relationship of Formula 3 means that the sum of I2 and W P in FIG. 12 is equal to or greater than W N This such relationship is a necessary relationship in achieving the object of this application.

[0110] The structure of FIG. 12 can be designed to further satisfy the following Formula 4.

[0111] [Formula 4] I2 + T P / tanθ2 ≤ T N / sinθ1

[0112] In Formula 4, T N , θ1, I2, T P and θ2 have the same meaning as in Formula 3.

[0113] The structure of FIG. 12 can also be designed to further satisfy the following Formula 5.

[0114] [Formula 5] θ2 / θ1 > 1

[0115] In Formula 5, θ1 and θ2 have the same meaning as in Formula 3 and Formula 4.

[0116] The upper limit of θ2 / θ1 in the above Formula 5 can be formed at an appropriate ratio. For example, the θ2 / θ1 can be about 5 or less, 4.5 or less, 4 or less, 3.5 or less, 3 or less, 2.5 or less, 2 or less, or 1.5 or less.

[0117] With the above design, while ensuring the capacity relationship between the negative electrode and the positive electrode where N / P inversion does not occur, the capacity per unit area of the positive electrode can be maximized.

[0118] As described above, in the structures of the electrode assemblies in FIGS. 11 and 12, it is shown when the active material layers 301 and 401 are formed only between the current collectors 103 and 104 and the separator 200, but the active material layers 301 and 401 may also be formed on the opposite surfaces of the respective current collector layers 103 and 104.

[0119] For example, in the above structure, the negative electrode can further include an active material layer formed on the surface opposite to the surface of the current collector layer (103 in FIGS. 11 and 12) facing the separator 200.

[0120] In such a case, the further included active material layer can have a symmetric structure with the active material layer (301 in FIGS. 11 and 12) existing between the current collector layer (103 in FIGS. 11 and 12) and the separator (200 in FIGS. 11 and 12).

[0121] That is, for example, as shown in FIG. 10, when the active material layers 101 and 102 are formed on both sides of the current collector layer 100, the active material layers 101 and 102 can have a symmetric structure. The symmetric structure at this time means a substantial symmetric structure.

[0122] Therefore, in the above symmetric structure, the inclination angle of the sliding part (for example, θ1 in FIGS. 11 and 12) and the thickness of the active material layer (T in FIGS. 11 and 12) N ) do not necessarily have exactly the same value. For example, when the absolute value of the error of the inclination angle or the thickness is 10% or less, 9% or less, 8% or less, 7% or less, 6% or less, 5% or less, 4% or less, 3% or less, 2% or less, or 1% or less in both active material layers, both active material layers can be regarded as having a symmetric structure. In the above, the error is, for example, in the case of the thickness, taking the thickness of any one of the active material layers as T N1 and the thickness of the other active material layer as T N2 , when 100Х(T N1 - TN2 ) / T N2 It is calculated by this, and this is the same even in the case of the tilt angle.

[0123] In the case of the positive electrode with the above structure, it may further include an active material layer formed on the surface opposite to the surface facing the separator 200 of the current collector layer (104 in FIGS. 11 and 12).

[0124] In such a case, the further included active material layer can have a symmetrical structure with the active material layer (401 in FIGS. 11 and 12) existing between the current collector layer (104 in FIGS. 11 and 12) and the separator (200 in FIGS. 11 and 12) as in the case of the negative electrode, and the meaning of the symmetrical structure is the same as that in the case of the negative electrode at this time.

[0125] In the present application, the surface of the sliding portion of the active material layer of the negative electrode or the positive electrode (that is, the surface of the inclined portion) can be a cut surface, that is, a cut surface. That is, the sliding portion can be a sliding portion naturally generated in the slurry coating process, or can be artificially formed by cutting. If the tilt angle, width (W in FIGS. 11 and 12 N , W P , θ1, θ2, etc.) and the intervals (I1, I2, etc. in FIGS. 11 and 12) between the negative electrode active material layer and the positive electrode active material layer cannot satisfy the above formulas 1 to 5, the sliding portion can be artificially formed by a known cutting method.

[0126] There is no particular limitation on the method of artificially forming such a sliding portion, and known etching, cutting or non-contact cutting (for example, a cutting method using a laser) methods can be applied.

[0127] Also, there is no particular limitation on the materials for forming the current collector, the active material layer, etc. in the electrode assembly of the present application, and the above structure can be formed using known materials.

[0128] Moreover, there is no limitation on the manufacturing method thereof, and the electrode assembly can be configured by manufacturing an electrode by a known manufacturing method. However, if necessary for an electrode formed by a known manufacturing method, the mentioned indentation, cutting or non-contact cutting process may be performed.

[0129] The present application also relates to a secondary battery or an electrochemical device including the electrode assembly and an electrolyte.

[0130] As long as the electrode assembly of the present application is applied, there is no particular limitation on the materials constituting the secondary battery or the electrochemical device, and known materials can be used.

Claims

1. A negative electrode; a positive electrode and a separator, wherein the negative electrode and the positive electrode are laminated with the separator interposed therebetween, the negative electrode and the positive electrode each include a current collector layer and an active material layer existing at least between the current collector layer and the separator, each of the negative electrode and the positive electrode has a first end portion where a tab portion is formed and a second end portion on the opposite side of the first end portion, the negative electrode and the positive electrode are laminated such that their first end portions face each other, or such that one of the first end portions faces the other second end portion, a slitting portion is formed in one of the active material layers of either the first or second end portion of the negative electrode, and a sliding portion is formed in the other active material layer, the active material layers at both end portions of the positive electrode are located inside the active material layers at both end portions of the negative electrode that face each other, The distance (I １ ) and the interval (I) between the active material layer of the positive electrode and the active material layer of the negative electrode at the end of the negative electrode where the sliding portion is formed. ２ ) ratio I ２ / I １ is in the range of 0.5 to 10.

2. The electrode assembly according to claim 1, wherein the active material layer of the negative electrode is thicker than the active material layer of the positive electrode.

3. The electrode assembly according to claim 1, wherein the sliding portion is formed in the active material layer at the end portion of the positive electrode that faces the end portion of the negative electrode where the slitting portion is formed.

4. The electrode assembly according to claim 3, wherein the surface of the sliding portion of the active material layer of the positive electrode is a cut surface.

5. The electrode assembly according to claim 3, wherein the slitting portion is formed in the active material layer of the positive electrode at the end opposite to the end where the sliding portion of the active material layer of the positive electrode is formed.

6. The electrode assembly according to claim 5, wherein the slitting portion of the active material layer of the positive electrode exists inside the sliding portion of the active material layer of the negative electrode.

7. The electrode assembly according to claim 5, satisfying the following formula 1: 【Formula 1】 T Ｎ / tanθ １ ≤I ２ T in Formula 1 Ｎ is the thickness of the active material layer of the negative electrode, and θ １ is the inclination angle of the sliding portion of the negative electrode, and I ２ is the distance between the active material layer of the positive electrode and the active material layer of the negative electrode at the end of the negative electrode where the sliding portion is formed.

8. tanθ １ The electrode assembly according to claim 7, wherein １ is in the range of 0.001 to 10.

9. The electrode assembly according to claim 7, further satisfying the following formula 2: 【Formula 2】 I ２ ≤ T Ｎ / sinθ １ T in Formula 2 Ｎ is the thickness of the active material layer of the negative electrode, and θ １ is the inclination angle of the sliding portion of the negative electrode, and I ２ is the distance between the active material layer of the positive electrode and the active material layer of the negative electrode at the end of the negative electrode where the sliding portion is formed.

10. The electrode assembly according to claim 3, wherein a second sliding portion is formed in the active material layer of the positive electrode at the end opposite to the end where the sliding portion of the active material layer of the positive electrode is formed.

11. The electrode assembly according to claim 10, wherein the surface of the second sliding portion of the active material layer of the positive electrode is a cut surface.

12. The electrode assembly according to claim 10, satisfying the following formula 3: 【Formula 3】 T Ｎ / tanθ １ ≤ I ２ + T Ｐ / tanθ ２ T in Formula 3 Ｎ is the thickness of the active material layer of the negative electrode, θ １ is the inclination angle of the sliding portion of the negative electrode, I ２ is the distance between the active material layer of the positive electrode and the active material layer of the negative electrode at the end of the negative electrode where the sliding portion is formed, T Ｐ is the thickness of the active material layer of the positive electrode, θ ２ is the inclination angle of the second sliding portion of the positive electrode.

13. The electrode assembly according to claim 12, further satisfying the following formula 4: 【Formula 4】 I ２ +T Ｐ / tanθ ２ ≤T Ｎ / sinθ １ T in Formula 4 Ｎ is the thickness of the active material layer of the negative electrode, and θ １ is the inclination angle of the sliding portion of the negative electrode, and I ２ is the distance between the active material layer of the positive electrode and the active material layer of the negative electrode at the end of the negative electrode where the sliding portion is formed, and T Ｐ is the thickness of the active material layer of the positive electrode, and θ ２ is the inclination angle of the second sliding portion of the positive electrode.

14. The electrode assembly according to claim 10, satisfying the following formula 5: [Formula 5] θ ２ / θ １ > 1 In Equation 5, θ １ is the inclination angle of the sliding portion of the negative electrode, and θ ２ is the inclination angle of the second sliding portion of the positive electrode.

15. The electrode assembly according to claim 1, wherein the negative electrode further includes an active material layer formed on a surface opposite to the surface facing the separator of the current collector layer.

16. The electrode assembly according to claim 15, wherein the active material layer formed on a surface opposite to the surface facing the separator of the current collector layer of the negative electrode and the active material layer existing between the current collector layer and the separator have a symmetric structure.

17. The electrode assembly according to claim 1, wherein the positive electrode further includes an active material layer formed on a surface opposite to the surface facing the separator of the current collector layer.

18. The electrode assembly according to claim 17, wherein the active material layer formed on a surface opposite to the surface facing the separator of the current collector layer of the positive electrode and the active material layer existing between the current collector layer and the separator have a symmetric structure.

19. A secondary battery including the electrode assembly and an electrolyte according to any one of claims 1 to 18.

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