Electrode assembly, electrode plate, secondary battery, and method for manufacturing electrode plate for secondary battery

Abstract

The present invention relates to an electrode assembly, an electrode plate, a secondary battery, and a method for manufacturing an electrode plate for a secondary battery. Disclosed are an electrode assembly, an electrode plate, a secondary battery, and a method for manufacturing an electrode plate for a secondary battery according to one aspect of the present invention, wherein the electrode assembly is configured to have a structure in which positive and negative electrode plates are alternately disposed, with a separator interposed therebetween, and stacked or wound, and the electrode plates positioned more towards the inner side of the electrode assembly are configured to have a thicker composite coating layer than the electrode plates of the same polarity positioned more towards the outer side of the electrode assembly, thereby solving the problem of non-uniformity in charging speed caused by differences in temperature between the inner side and the outer side of the stacked or wound electrode plates.

Description

Electrode assembly, electrode plate, secondary battery, method for manufacturing electrode plate for secondary battery

[0001] The present invention relates to an electrode assembly, an electrode plate, a secondary battery, and a method for manufacturing an electrode plate for a secondary battery, and more particularly, to an electrode assembly in which a positive electrode plate and a negative electrode plate are alternately arranged with a separator therebetween to form a laminated or wound structure, and wherein an electrode plate arranged at a more inner position of the electrode assembly has a greater thickness of a composite coating layer than an electrode plate of the same polarity arranged at a more outer position, thereby resolving a problem of uneven charging speed caused by a temperature difference between the inner and outer sides of the laminated or wound electrode plates.

[0002]

[0003] Secondary batteries are manufactured as final products through an electrode process that creates positive and negative plates, an assembly process that laminates or winds the positive and negative plates together with a separator and places them in a battery case, an activation process that imparts electrical energy characteristics to the battery so that it can function as a rechargeable battery, and a pack process that modularizes battery cells according to the characteristics of the end user (e.g., electric vehicles).

[0004] In the assembly process, an electrode assembly is formed by alternately placing positive and negative electrode plates with a separator between them to form a laminated or wound structure.

[0005] However, the electrode assembly may have an uneven charging speed problem due to heat dissipation and temperature difference between the inner and outer sides of the laminated or rolled electrode plates.

[0006] That is, among the laminated or rolled electrode plates, the electrode plates located on the inner side (center side) have difficulty dissipating heat compared to the electrode plates located on the outer side, and are therefore exposed to a relatively high temperature environment. This temperature difference causes a difference in internal resistance between the electrode plates located on the inner side (center side) and the electrode plates located on the outer side, which in turn causes a difference in charging speed.

[0007] In particular, recently developed secondary batteries tend to form thick film electrodes with a composite coating layer formed on the current collector in order to increase battery capacity, so the problem of uneven charging speed becomes even more serious.

[0008] In addition, the electrode plates located on the inner side (center side) are more vulnerable to the problem of deterioration in lifespan due to long-term exposure to high-temperature environments compared to the electrode plates located on the outer side.

[0009]

[0010] The present invention has been made in consideration of the above problems, and the purpose of the present invention is to provide an electrode assembly, an electrode plate, a secondary battery, and a method for manufacturing an electrode plate for a secondary battery, which comprises an electrode assembly in which a positive electrode plate and a negative electrode plate are alternately arranged with a separator therebetween to form a laminated or rolled structure, and in which an electrode plate arranged at a more inner position of the electrode assembly has a greater thickness of a composite coating layer than an electrode plate of the same polarity arranged at a more outer position, thereby resolving the problem of uneven charging speed caused by a difference in temperature between the inner and outer sides of the laminated or rolled electrode plates.

[0011]

[0012] According to one aspect of the present invention for achieving the above object, an electrode assembly is disclosed, which has a structure in which positive electrode plates and negative electrode plates are alternately arranged and a separator is arranged between the positive electrode plates and negative electrode plates, wherein the positive electrode plates and negative electrode plates each have a structure in which a composite coating layer is formed on at least one side of a current collector, and another electrode plate of the same polarity is configured to have a thickness value of a composite coating layer greater than that of the electrode plates among the electrode plates forming the arranged state based on an arbitrary cross-section in the arranged state, and is configured to be included at a further inner position of the electrode assembly.

[0013] According to another aspect of the present invention, an electrode assembly is disclosed, which has a structure in which positive electrode plates and negative electrode plates are alternately arranged and a separator is arranged between the positive electrode plates and negative electrode plates, wherein the positive electrode plates and negative electrode plates each have a structure in which a composite coating layer is formed on at least one side of a current collector, and an electrode assembly is characterized in that, based on an arbitrary cross-section in the arranged state, an electrode plate arranged at a more inner position of the electrode assembly has a greater thickness of the composite coating layer than an electrode plate of the same polarity arranged at a more outer position.

[0014] Preferably, based on any cross-section in the arranged state, the composite coating layer formed on any electrode plate is formed to have a change state in which the thickness value gradually decreases or gradually increases along one direction.

[0015] Preferably, based on any cross-section of the arranged state, the composite coating layer formed on any electrode plate is formed to have a change state in which the thickness value gradually decreases or gradually increases along one direction, and based on the cross-section, the composite coating layer formed on another electrode plate of the same polarity that is arranged closest to the arbitrary electrode plate is formed to have a change state in which the thickness value gradually decreases or gradually increases along the opposite direction to the one direction.

[0016] Preferably, the composite coating layer is formed on only one side of the current collector or on both sides, and the thickness of the composite coating layer of any electrode plate based on any cross-section in the arranged state is the sum of the thickness values ​​of the composite coating layers of each side formed on one side or both sides of the current collector.

[0017] According to another aspect of the present invention, an electrode plate is disclosed, wherein a composite coating layer is formed on at least one side of a current collector, wherein the composite coating layer is configured to have a change state in which a thickness value gradually decreases or gradually increases along one direction on the coating surface of the current collector.

[0018] According to another aspect of the present invention, a jelly roll-type electrode assembly is disclosed, which is formed by winding a positive electrode plate having the above characteristics; a negative electrode plate having the above characteristics; and a separator disposed between the positive electrode plate and the negative electrode plate, and is configured such that, based on any cross-section in a wound state, an electrode plate disposed at a more inner position has a greater thickness of a composite coating layer than an electrode plate of the same polarity disposed at a more outer position.

[0019] According to another aspect of the present invention, a stacked electrode assembly is disclosed, which is formed by stacking a positive electrode plate having the above characteristics; a negative electrode plate having the above characteristics; and a separator disposed between the positive electrode plate and the negative electrode plate, and is configured such that, based on any cross-section of the stacked state, an electrode plate disposed at a more inner position has a greater thickness of a composite coating layer than an electrode plate of the same polarity disposed at a more outer position.

[0020] According to another aspect of the present invention, a stack-folding electrode assembly is disclosed, which is formed by wrapping unit cells formed by stacking a positive electrode plate having the above characteristics, a negative electrode plate having the above characteristics, and a first separator disposed between the positive electrode plate and the negative electrode plate with a second separator having a sheet shape, and is configured such that, based on an arbitrary cross-section in a state where the unit cells are wrapped with the second separator, an electrode plate disposed at a more inner position has a greater thickness of a composite coating layer than an electrode plate of the same polarity disposed at a more outer position.

[0021] According to another aspect of the present invention, an electrode assembly is disclosed, which has a structure in which positive electrode plates and negative electrode plates are alternately arranged and a separator is arranged between the positive electrode plates and negative electrode plates, wherein the positive electrode plates and negative electrode plates each have a structure in which a composite coating layer is formed on at least one side of a current collector, and another electrode plate of the same polarity is configured to have a composite loading amount of a composite coating layer greater than that of the electrode plates among the electrode plates arranged based on an arbitrary cross-section in the arranged state, and is configured to be included at a further inner position of the electrode assembly.

[0022] According to another aspect of the present invention, an electrode assembly is disclosed, which has a structure in which positive electrode plates and negative electrode plates are alternately arranged and a separator is arranged between the positive electrode plates and negative electrode plates, wherein the positive electrode plates and negative electrode plates each have a structure in which a composite coating layer is formed on at least one side of a current collector, and an electrode assembly is characterized in that, based on an arbitrary cross-section in the arranged state, an electrode plate arranged at a more inner position of the electrode assembly has a larger composite loading amount of the composite coating layer than an electrode plate of the same polarity arranged at a more outer position.

[0023] According to another aspect of the present invention, a secondary battery is disclosed, comprising: the electrode assembly; and a battery case in which the electrode assembly is loaded and an electrolyte is injected.

[0024] According to another aspect of the present invention, there is provided a method for producing a positive electrode mixture, comprising: 1) mixing a positive electrode active material with a positive electrode conductive agent, a binder, and a solvent to produce a positive electrode mixture; and mixing a negative electrode conductive agent, a binder, and a solvent to produce a negative electrode mixture; 2) coating the positive electrode mixture on at least one side of a positive electrode current collector with a preset thickness to form a preset pattern and drying the coating to form a positive electrode coating plate having a positive electrode mixture coating layer formed thereon, and coating the negative electrode mixture on at least one side of a negative electrode current collector with a preset thickness to form a preset pattern and drying the coating to form a negative electrode coating plate having a negative electrode mixture coating layer formed thereon; 3) rolling the positive electrode coating plate, and rolling the negative electrode coating plate; And 4) a step of slitting and notching the rolled positive electrode coating plate according to preset conditions to obtain a positive electrode plate, and a step of slitting and notching the rolled negative electrode coating plate according to preset conditions to obtain a negative electrode plate; and through control of at least one of the coating layer thickness conditions in step 2) and the rolling roll gap conditions in step 3), a method for manufacturing an electrode plate for a secondary battery is disclosed, wherein the composite coating layer formed on the positive electrode plate obtained in step 4) and the composite coating layer formed on the negative electrode plate have a change state in which the thickness value gradually decreases or gradually increases along one direction on the coating surface of each current collector.

[0025]

[0026] The present invention configures an electrode assembly in which positive and negative electrode plates are alternately arranged with a separator between them to form a laminated or wound structure, and the electrode plate arranged at a more inner position of the electrode assembly has a greater thickness of the composite coating layer than the electrode plate of the same polarity arranged at a more outer position, thereby resolving the problem of uneven charging speed caused by the temperature difference between the inner and outer sides of the laminated or wound electrode plates.

[0027] In addition, the present invention provides a structure of an electrode plate having a change state in which the thickness of the composite coating layer gradually decreases or gradually increases in one direction, and a method for manufacturing the same, thereby facilitating the manufacture of an electrode assembly in which a change in the thickness of the composite coating layer of the electrode plate is required.

[0028]

[0029] Figures 1 to 3b are cross-sectional schematic diagrams of an electrode assembly according to an embodiment of the present invention.

[0030] Figures 4a and 4c are enlarged cross-sectional views of an electrode assembly according to an embodiment of the present invention.

[0031] Figure 5 is a cross-sectional schematic diagram of an electrode according to an embodiment of the present invention;

[0032] Figure 6 is a schematic diagram for explaining the loading state of the coating layer of the electrode assembly according to an embodiment of the present invention.

[0033] Figure 7 is a flow chart of a method for manufacturing an electrode assembly according to an embodiment of the present invention.

[0034] Figure 8 is a schematic diagram for explaining the process of forming a coating layer of an electrode according to an embodiment of the present invention.

[0035] Figure 9 is a schematic diagram for explaining the coating layer rolling process of an electrode according to an embodiment of the present invention.

[0036] Figure 10 is a cross-sectional schematic diagram of a secondary battery according to an embodiment of the present invention.

[0037]

[0038] The present invention may be embodied in various forms without departing from its technical spirit or essential characteristics. Therefore, the embodiments of the present invention are merely illustrative in all respects and should not be construed as limiting.

[0039] Terms such as "first" and "second" are used solely to distinguish one component from another. For example, without departing from the scope of the present invention, a first component could be referred to as a "second component," and similarly, a second component could also be referred to as a "first component."

[0040] When a component is referred to as being "connected" or "connected" to another component, it may be directly connected or connected to that other component, but there may also be other components in between.

[0041] The singular expressions used in this application include plural expressions unless the context clearly dictates otherwise. In this application, terms such as "include," "have," and "have" are intended to indicate the presence of components or combinations thereof described in the specification, but do not preclude the possibility of other components or features being present or added.

[0042]

[0043] Hereinafter, a preferred embodiment according to the present invention will be described in detail with reference to the attached drawings.

[0044] FIGS. 1 to 3b are cross-sectional schematic views of an electrode assembly according to an embodiment of the present invention, FIGS. 4a and 4c are enlarged cross-sectional views of an electrode assembly according to an embodiment of the present invention, and FIG. 5 is a cross-sectional schematic view of an electrode according to an embodiment of the present invention.

[0045] The electrode assembly (EA) of the present embodiment can be configured in the form of a stacked electrode assembly (Fig. 1), a jelly roll-type electrode assembly (Fig. 2), or a stack-folding electrode assembly (Figs. 3a, 3b).

[0046] In the case of a stacked electrode assembly (Fig. 1) or a jelly roll electrode assembly (Fig. 2), a positive electrode plate (1) and a negative electrode plate (5) are arranged alternately, and a separator (3) is arranged between the positive electrode plate (1) and the negative electrode plate (5).

[0047] In the case of a stack-folding type electrode assembly (Fig. 3a, Fig. 3b), a positive electrode plate (1) and a negative electrode plate (5) are arranged alternately, and a separator (3) is arranged between the positive electrode plate (1) and the negative electrode plate (5). The basic structure is formed by stacking the positive electrode plate (1), the negative electrode plate (5), and the first separator (3) arranged between the positive electrode plate (1) and the negative electrode plate (5), and wrapping the unit cells (U) formed by wrapping the second separator (3') in the form of a sheet.

[0048] The above positive electrode plate (1) and negative electrode plate (5) each have a structure in which a composite coating layer (B) is formed on at least one side of the current collector (A). The composite coating layer (B) may be formed on only one side (B1) of the current collector (A) or on both sides (B1, B2). Typically, the composite coating layer (B) is formed on both sides (B1, B2) of the current collector (A).

[0049] While including the above basic configuration, for example, the electrode assembly (EA) of the present embodiment is configured such that, based on an arbitrary cross-section in a deployed state, another electrode plate of the same polarity is included at a further inner position of the electrode assembly (EA), and the electrode plate is configured to have a thickness value (T) of the composite coating layer (B) greater than that of any of the electrode plates (1, 5) forming the deployed state. The arbitrary cross-section in a deployed state can be understood as a state in which a virtual cross-section is created at any point of the electrode assembly (EA) so that a stacked or wound state of all electrode plates forming the electrode assembly (EA) can be seen.

[0050] For example, when any of the electrode plates (1,5) forming the arranged state is regarded as the positive electrode plate 1-3, the positive electrode plate 1-2 and / or the positive electrode plate 1-1, which are located further inward, are configured such that the thickness of the composite coating layer (B) has a thickness value (T) greater than that of the positive electrode plate 1-3. From another perspective, both the positive electrode plate 1-2 and the positive electrode plate 1-1 may be configured such that they have a thickness value (T) greater than that of the positive electrode plate 1-3, or the positive electrode plate 1-2 may have the same thickness value (T) as the positive electrode plate 1-3, while the positive electrode plate 1-1 may have a thickness value (T) greater than that of the positive electrode plate 1-3.

[0051] As another example, when any of the electrode plates (1,5) forming the arranged state is regarded as a positive electrode plate 1-2, the positive electrode plate 1-1 located further inward is configured such that the thickness of the composite coating layer (B) has a thickness value (T) greater than that of the positive electrode plate 1-2.

[0052] The same configuration as above can also be used for the negative electrode plates 5-3, 5-2, 5-1, 5-2', and 5-3'.

[0053] In the description of this embodiment, the concept of 'inner' or 'outer' is a relative concept, and among the electrode plates of the same polarity forming a laminated or wound state, the electrode plate located at the most central side can be regarded as being at the innermost position among the electrode plates of the corresponding polarity.

[0054] Referring to Fig. 1, among the five positive electrode plates 1-3, 1-2, 1-1, 1-2', 1-3' that form a laminated state, the positive electrode plate 1-1, which is located at the center, is at the innermost position, and the positive electrode plates 1-2, 1-2' can be seen as being at an outer position relative to the positive electrode plate 1-1. The positive electrode plate 1-2 is located at an inner position relative to the positive electrode plate 1-3, but at an outer position relative to the positive electrode plate 1-1. The negative electrode plate can also be understood using the same concept.

[0055] More preferably, the electrode assembly (EA) of the present embodiment is configured such that, based on any cross-section in the arranged state, an electrode plate arranged at a more inner position of the electrode assembly (EA) has a thickness value (T) of a composite coating layer (B) greater than that of an electrode plate of the same polarity arranged at a more outer position.

[0056] In this case, for example, both the positive electrode plate 1-2 and the positive electrode plate 1-1 are configured such that the thickness of the composite coating layer (B) has a thickness value (T) greater than that of the positive electrode plate 1-3. In addition, the positive electrode plate 1-1 is configured such that the thickness of the composite coating layer (B) has a thickness value (T) greater than that of the positive electrode plate 1-2. The negative electrodes 5-3, 5-2, 5-1, 5-2', and 5-3' may also have the same configuration as above.

[0057] Meanwhile, for example, based on an arbitrary cross-section in a deployed state, the composite coating layer (B) formed on an arbitrary electrode plate has a uniform thickness without any particular directionality in the electrode plate, but may have a difference in thickness value only according to a change in the inner or outer position in the electrode assembly (EA).

[0058] Referring to FIGS. 1 to 3b, the positive electrode plates 1-3, 1-2, 1-1, 1-2', 1-3' or the negative electrode plates 5-3, 5-2, 5-1, 5-2', 5-3' each have a difference in thickness value (T) as described above, but within any one electrode plate (e.g., positive electrode plate 1-2), the composite coating layer (B) may have a uniform thickness without any particular directionality in the corresponding electrode plate.

[0059] Referring to Fig. 4a, the thickness value (T1+T2) of the composite coating layer (B) of the positive electrode plate 1-1 has a greater value than the thickness value (T1'+T2') of the composite coating layer (B) of the positive electrode plate 1-2 located further outward, but the thickness of the composite coating layer (B) within each electrode plate is uniform.

[0060] As a preferable example in comparison therewith, based on any cross-section in a deployed state, the composite coating layer (B) formed on any electrode plate can be formed to have a change state in which the thickness value (T) gradually decreases or gradually increases along one direction.

[0061] Referring to FIG. 4b or FIG. 4c, based on any cross-section in the arranged state, the thickness value (T1+T2) of the composite coating layer (B) of the positive electrode plate 1-1 has a larger value than the thickness value (T1'+T2') of the composite coating layer (B) of the positive electrode plate 1-2 located further outward. In addition, within any one electrode plate (e.g., positive electrode plate 1-2), the thickness value (T) of the composite coating layer (B) gradually decreases or increases in one direction so that the thickness value (T1a'+T2a') of the composite coating layer (B) at the right side (F2) of the drawing has a larger value than the thickness value (T1'+T2') of the composite coating layer (B) at the left side (F1) of the drawing.

[0062] As another preferred example, based on any cross-section of the arranged state, the composite coating layer (B) formed on any electrode plate may be formed to have a change state in which the thickness value (T) gradually decreases or gradually increases along one direction, and based on the cross-section, the composite coating layer (B) formed on another electrode plate of the same polarity that is arranged closest to the arbitrary electrode plate may be formed to have a change state in which the thickness value (T) gradually decreases or gradually increases along the opposite direction to the one direction.

[0063] For example, in Fig. 4b, the direction of increase (F2) of the thickness value (T) of the composite coating layer (B) of the positive electrode plate 1-1 and the direction of increase (F2) of the thickness value (T) of the composite coating layer (B) of the positive electrode plate 1-2 are the same, but in Fig. 4c, the direction of increase (F2) of the thickness value (T) of the composite coating layer (B) of the positive electrode plate 1-1 and the direction of increase (F1) of the thickness value (T) of the composite coating layer (B) of the positive electrode plate 1-2 are opposite to each other.

[0064] Considering the gradual change rate of the thickness value (T) of the composite coating layer (B) and the electrode arrangement structure of the electrode assembly (EA), the electrode assembly (EA) can be made with the arrangement structure of Fig. 4b or the electrode assembly (EA) can be made with the arrangement structure of Fig. 4c.

[0065] Meanwhile, the configuration of the electrode assembly (EA) of the above-described embodiment can also be understood from the perspective of the loading amount of the composite coating layer (B). Fig. 6 is a schematic diagram illustrating the loading state of the coating layer of the electrode assembly according to the embodiment of the present invention.

[0066] That is, the electrode assembly (EA) of the present embodiment may be understood as being configured such that, based on an arbitrary cross-section of the arranged state, another electrode plate of the same polarity is included at a more inner position of the electrode assembly (EA) so that the composite loading amount of the composite coating layer (B) is greater than that of any electrode plate among the electrode plates (1, 5) forming the arranged state.

[0067] More preferably, the electrode assembly (EA) of the present embodiment may be understood to be configured such that, based on any cross-section in the arranged state, an electrode plate arranged at a more inner position of the electrode assembly (EA) has a larger composite loading amount of the composite coating layer (B) than an electrode plate of the same polarity arranged at a more outer position.

[0068] Typically, the loading amount of the positive electrode mixture is greater than that of the negative electrode mixture, and accordingly, the thickness of the formed mixture coating layer (B) is typically greater than that of the positive electrode plate.

[0069]

[0070] The electrode assembly (EA) of this embodiment is described from the perspective of the electrode plate configuration.

[0071] As a preferred example, referring to FIG. 5, the electrode plate for forming the electrode assembly (EA) of the present embodiment is an electrode plate having a composite coating layer (B) formed on at least one side of a current collector (A), wherein the composite coating layer (B) can be configured to have a change state in which the thickness value (T) gradually decreases or gradually increases along one direction on the coating surface of the current collector (A). This characteristic of the electrode plate is hereinafter referred to as a 'gradually changing thickness characteristic' for convenience of explanation.

[0072] By using electrode plates having gradually changing thickness characteristics as described above, a stacked electrode assembly (EA), a jelly roll electrode assembly (EA), or a stack-folding electrode assembly (EA) can be constructed.

[0073] For example, a stacked electrode assembly (EA) is formed by stacking a positive electrode plate (1) having a gradually changing thickness characteristic, a negative electrode plate (5) having a gradually changing thickness characteristic, and a separator (3) disposed between the positive electrode plate (1) and the negative electrode plate (5).

[0074] In addition, the stacked electrode assembly (EA) is configured such that, based on any cross-section in a stacked state, the electrode plate positioned further inward has a greater thickness value (T) of the composite coating layer (B) than the electrode plate of the same polarity positioned further outward. For example, such a configuration can be understood as applying the electrode plate having the gradually changing thickness characteristics of FIG. 5 to the stacked electrode assembly (EA) structure of FIG. 1.

[0075] As another example, a jelly roll-type electrode assembly (EA) is formed by winding a positive electrode plate (1) having a gradually changing thickness characteristic, a negative electrode plate (5) having a gradually changing thickness characteristic, and a separator (3) disposed between the positive electrode plate (1) and the negative electrode plate (5).

[0076] In addition, the jelly-roll type electrode assembly (EA) is configured such that, based on any cross-section in a rolled state, the electrode plate positioned further inward has a thickness value (T) of the composite coating layer (B) that is greater than that of the electrode plate of the same polarity positioned further outward. For example, such a configuration can be understood as applying the electrode plate having the gradually changing thickness characteristic of FIG. 5 to the jelly-roll type electrode assembly (EA) structure of FIG. 2.

[0077] As another example, a stack-folding electrode assembly (EA) is formed by wrapping unit cells (U) formed by stacking a positive electrode plate (1) having a gradually changing thickness characteristic, a negative electrode plate (5) having a gradually changing thickness characteristic, and a first separator (3) disposed between the positive electrode plate (1) and the negative electrode plate (5) with a second separator (3') having a sheet shape.

[0078] In addition, the stack-folding type electrode assembly (EA) is configured such that, based on an arbitrary cross-section in which the unit cells (U) are wrapped with the second separator (3), the electrode plate positioned further inward has a thickness value (T) of the composite coating layer (B) greater than that of the electrode plate of the same polarity positioned further outward. For example, such a configuration can be understood as applying an electrode plate having a gradually changing thickness characteristic of FIG. 5 to the stack-folding type electrode assembly (EA) structure of FIG. 3a or FIG. 3b.

[0079] For example, among the laminated or wound electrode plates, the electrode plate located on the inner side (center side) has difficulty dissipating heat compared to the electrode plate located on the outer side, so it has a higher temperature during battery charging and discharging, which results in a relatively lower internal resistance and thus a higher charge / discharge speed. Therefore, if the thickness of the composite coating layer (B) of the electrode plate located on the inner side (center side) is made larger than that of the outer side, the charging capacity is further increased, and charging / discharging is performed at a higher speed due to the lower internal resistance under high-temperature conditions, so that the charge / discharge speed can be balanced with that of the electrode plate located on the outer side. The configuration of the electrode assembly (EA) of the present embodiment is centered on this point.

[0080]

[0081] A secondary battery can be constructed using the electrode assembly (EA) according to the above embodiments. Fig. 10 is a cross-sectional schematic diagram of a secondary battery according to an embodiment of the present invention.

[0082] The secondary battery (SB) of the present embodiment is configured to include an electrode assembly (EA) according to the above embodiments, and a battery case (9) into which the electrode assembly (EA) is loaded and into which an electrolyte (8) is injected.

[0083]

[0084] Preferably, the electrode plate having the gradually changing thickness characteristics illustrated in Fig. 5 can be manufactured through the following manufacturing method. Fig. 7 is a flow chart of a manufacturing method of an electrode assembly according to an embodiment of the present invention, Fig. 8 is a schematic diagram for explaining a process of forming a coating layer of an electrode according to an embodiment of the present invention, and Fig. 9 is a schematic diagram for explaining a process of rolling a coating layer of an electrode according to an embodiment of the present invention.

[0085] In step 1), a positive electrode active material is mixed with a positive electrode conductive agent, a binder, and a solvent to create a positive electrode mixture, and a negative electrode active material is mixed with a negative electrode conductive agent, a binder, and a solvent to create a negative electrode mixture.

[0086] In step 2), the positive electrode mixture is coated on at least one side of the positive electrode current collector (A) to a preset thickness so as to form a preset pattern and dried to form a positive electrode coating plate on which a positive electrode mixture coating layer (B) is formed, and the negative electrode mixture is coated on at least one side of the negative electrode current collector (A) to a preset thickness so as to form a preset pattern and dried to form a negative electrode coating plate on which a negative electrode mixture coating layer (B) is formed.

[0087] For example, the composite coating for forming the composite coating layer (B) can be performed by a known roll-to-roll coating.

[0088] In step 3), the positive electrode coating plate is rolled, and the negative electrode coating plate is rolled. For example, rolling can be performed using a known rolling roll.

[0089] In step 4), the rolled positive electrode coating plate is slit and notched according to preset conditions to obtain a positive electrode plate (1), and the rolled negative electrode coating plate is slit and notched according to preset conditions to obtain a negative electrode plate (5). In the slitting process, the electrode width is cut according to the designed battery specifications through a slitter. In the notching process, among the electrodes cut through the slitting process, the non-coated portion where the positive / negative electrode mixture is not applied is left with a portion for grounding the tab, and the rest is cut off.

[0090] In the above process, when the composite coating layer (B) is formed only on one side (B1 or B2) of the positive electrode plate (1) or negative electrode plate (5), steps 2) and / or 3) are performed only on one side of each current collector, and when the composite coating layer (B) is formed on both sides (B1 and B2) of the positive electrode plate (1) or negative electrode plate (5), steps 2) and / or 3) are performed sequentially or simultaneously on both sides of each current collector.

[0091] In the manufacturing method of the present embodiment, by controlling at least one of the coating layer thickness conditions in step 2) and the rolling roll gap conditions in step 3), the composite coating layer (B) formed on the positive electrode plate (1) obtained in step 4) and the composite coating layer (B) formed on the negative electrode plate (5) are configured to have a change state in which the thickness value (T) gradually decreases or gradually increases along one direction on the coating surface of each current collector (A).

[0092] For example, the control of the coating layer thickness condition in step 2) can be performed through coating layer application control in known roll-to-roll coating.

[0093] Roll-to-roll coating is a method of applying a coating agent to a flat substrate using a combination of rollers. Various roll-to-roll methods can be configured depending on the roller arrangement.

[0094] For example, Fig. 8 is a slot die coater method, in which a mixture (39) is applied to a collector (30) conveyed through a roll (31) using a die (32), and the gap between the die lip (33) and the roll (31) is controlled to control the loading amount of the mixture (39) applied to the substrate (30) and the thickness of the mixture coating layer (38) formed accordingly. Unexplained reference numeral 32a is a die head.

[0095] In this way, the coating layer thickness conditions in step 2) can be controlled through the coating layer application control in the known roll-to-roll coating. For example, by gradually increasing or decreasing the gap between the die lip (33) and the roll (31) along with the transport of the current collector (30), an electrode plate having a gradually changing thickness characteristic can be obtained.

[0096] As a variation, it is also possible to control the coating layer thickness conditions in step 2) by controlling the discharge amount of the supply pump that supplies the mixture. For example, by gradually increasing or decreasing the discharge amount of the supply pump that supplies the mixture along with the transport of the current collector (30), an electrode plate having a gradually changing thickness characteristic can be obtained.

[0097] For example, the control of the rolling roll gap condition in step 3) above can be performed through a known rolling roll gap control.

[0098] As an example, Fig. 9 illustrates a rolling process using rolling rolls (R1, R2), in which a current collector (A) to which a composite is applied is passed between rolling rolls R1 and R2, and the coating layer thickness conditions in step 3) can be controlled by controlling the gap between the rolling rolls R1 and R2. Since the thickness change of the composite coating layer occurs primarily rather than the current collector (A) made of a metal plate during the rolling process, the coating layer thickness conditions in step 3) can be controlled by controlling the gap between the known rolling rolls. For example, an electrode plate having a thickness characteristic that gradually changes can be obtained by gradually increasing or decreasing the gap between the rolling rolls R1 and R2 along with the transport of the current collector (A).

[0099] Control of the coating layer thickness condition in step 2) above and control of the rolling roll gap condition in step 3) above may be performed together or only one of them may be performed.

[0100] Through the above process, an electrode plate having a gradually changing thickness characteristic as illustrated in FIG. 5 can be obtained.

[0101] According to the above manufacturing method, electrode plates having composite coating layers (B) of different thicknesses need not be manufactured separately, but electrode plates having thickness characteristics that gradually change according to the above manufacturing method are obtained in a roll form, and then only by slitting and notching the electrode plates, electrode plates having thickness differences that enable a layout structure such as that of FIG. 4b or FIG. 4c can be obtained.

[0102]

[0103] While the present invention has been described with reference to the accompanying drawings, focusing on preferred embodiments, it will be apparent to those skilled in the art that numerous obvious modifications are possible without departing from the scope of the invention. Therefore, the scope of the present invention should be construed as encompassing these numerous modifications as defined by the claims.

Claims

1. An electrode assembly having a structure in which positive and negative electrode plates are alternately arranged and a separator is arranged between the positive and negative electrode plates. The above positive electrode plate and negative electrode plate each have a structure in which a composite coating layer is formed on at least one side of the current collector, An electrode assembly characterized in that, based on an arbitrary cross-section in a deployed state, another electrode plate of the same polarity is configured to have a thickness value of a composite coating layer greater than that of any electrode plate among the electrode plates forming the deployed state, and is configured to be included in a more inner position of the electrode assembly.

2. An electrode assembly having a structure in which positive and negative electrode plates are alternately arranged and a separator is arranged between the positive and negative electrode plates. The above positive electrode plate and negative electrode plate each have a structure in which a composite coating layer is formed on at least one side of the current collector, An electrode assembly characterized in that, based on an arbitrary cross-section in a positioned state, an electrode plate positioned at a more inner position of the electrode assembly has a thickness of a composite coating layer greater than that of an electrode plate of the same polarity positioned at a more outer position.

3. In paragraph 1 or 2, An electrode assembly characterized in that the composite coating layer formed on any electrode plate, based on any cross-section in a placed state, is formed to have a change state in which the thickness value gradually decreases or gradually increases along one direction.

4. In paragraph 2, Based on an arbitrary cross-section in a placed state, the composite coating layer formed on an arbitrary electrode plate is formed to have a change state in which the thickness value gradually decreases or gradually increases along one direction, An electrode assembly characterized in that the composite coating layer formed on another electrode plate of the same polarity, which is arranged closest to the arbitrary electrode plate based on the cross-section, is formed so that the thickness value gradually changes in a state opposite to the change state in the opposite direction to the one direction.

5. In paragraph 1 or 2, The above composite coating layer is formed on only one side of the collector or on both sides, An electrode assembly characterized in that, based on an arbitrary cross-section in a placed state, the thickness of the composite coating layer of an arbitrary electrode plate is the sum of the thickness values ​​of the composite coating layers of each side formed on one or both sides of the current collector.

6. An electrode plate having a composite coating layer formed on at least one side of a current collector, wherein the composite coating layer is configured to have a change state in which the thickness value gradually decreases or gradually increases along one direction on the coating surface of the current collector.

7. A bipolar plate having the characteristics of Article 6; A negative electrode plate having the characteristics of Article 6; and A separator disposed between the positive electrode plate and the negative electrode plate is formed by winding, A jelly roll-type electrode assembly configured such that, based on an arbitrary cross-section in a rolled state, an electrode plate positioned further inward has a greater thickness of a composite coating layer than an electrode plate of the same polarity positioned further outward.

8. A bipolar plate having the characteristics of Article 6; A negative electrode plate having the characteristics of Article 6; and A separator is formed by laminating a separator disposed between the positive electrode plate and the negative electrode plate, A stacked electrode assembly configured such that, based on any cross-section in a stacked state, an electrode plate positioned further inward has a greater thickness of a composite coating layer than an electrode plate of the same polarity positioned further outward.

9. It is formed by wrapping unit cells formed by laminating a positive electrode plate having the characteristics of Article 6, a negative electrode plate having the characteristics of Article 6, and a first separator disposed between the positive electrode plate and the negative electrode plate with a second separator having a sheet shape. A stack-folding electrode assembly configured such that, based on an arbitrary cross-section in which unit cells are wrapped with a second separator, an electrode plate positioned further inward has a greater thickness of a composite coating layer than an electrode plate of the same polarity positioned further outward.

10. An electrode assembly having a structure in which positive and negative electrode plates are alternately arranged and a separator is arranged between the positive and negative electrode plates. The above positive electrode plate and negative electrode plate each have a structure in which a composite coating layer is formed on at least one side of the current collector, An electrode assembly characterized in that, based on an arbitrary cross-section in a deployed state, another electrode plate of the same polarity is configured to have a larger composite loading amount of the composite coating layer than that of any electrode plate among the electrode plates forming the deployed state, and is included at a more inner position of the electrode assembly.

11. An electrode assembly having a structure in which positive and negative electrode plates are alternately arranged and a separator is arranged between the positive and negative electrode plates. The above positive electrode plate and negative electrode plate each have a structure in which a composite coating layer is formed on at least one side of the current collector, An electrode assembly characterized in that, based on an arbitrary cross-section in a positioned state, an electrode plate positioned at a more inner position of the electrode assembly has a larger composite loading amount of the composite coating layer than an electrode plate of the same polarity positioned at a more outer position.

12. An electrode assembly according to any one of the following items: 1, 2, 7, 8, 9, 10 and 11; and A secondary battery comprising a battery case in which the electrode assembly is loaded and an electrolyte is injected. 13.1) A step of mixing a positive electrode active material with a positive electrode conductive agent, binder, and solvent to make a positive electrode mixture, and a step of mixing a negative electrode conductive agent, binder, and solvent to a negative electrode active material to make a negative electrode mixture; 2) A step of forming a positive electrode coating plate having a positive electrode mixture coating layer formed thereon by coating the positive electrode mixture on at least one side of a positive electrode current collector with a preset thickness to form a preset pattern and drying the coating, and a step of forming a negative electrode coating plate having a negative electrode mixture coating layer formed thereon by coating the negative electrode mixture on at least one side of a negative electrode current collector with a preset thickness to form a preset pattern and drying the coating; 3) A step of rolling the positive electrode coating plate and rolling the negative electrode coating plate; and 4) A step of obtaining a positive electrode plate by slitting and notching the rolled positive electrode coating plate according to preset conditions, and a step of obtaining a negative electrode plate by slitting and notching the rolled negative electrode coating plate according to preset conditions; A method for manufacturing an electrode plate for a secondary battery, wherein the composite coating layer formed on the positive electrode plate obtained in step 4) and the composite coating layer formed on the negative electrode plate obtained in step 3) are configured to have a change state in which the thickness value gradually decreases or gradually increases along one direction on the coating surface of each current collector by controlling at least one of the coating layer thickness conditions in step 2) and the rolling roll gap conditions in step 3).

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