Electrode assembly with improved safety, lithium secondary battery including the same, battery module and battery pack including lithium secondary battery

Abstract

The present invention relates to an electrode assembly with enhanced safety capable of improving safety by reducing heat generation even when an internal or external short circuit occurs, a lithium secondary battery including the same, a battery module including the lithium secondary battery, and a battery pack.

Description

Technology Field

[0001] The present invention relates to an electrode assembly with improved safety, a lithium secondary battery including the same, a battery module including the lithium secondary battery, and a battery pack. Background Technology

[0003] With the increasing technological development and demand for mobile devices, the demand for secondary batteries as an energy source is rapidly rising. Among these secondary batteries, much research is being conducted on lithium secondary batteries, which possess high energy density and discharge voltage, and they are also being commercialized and widely used.

[0004] Lithium secondary batteries are generally manufactured by interposing two electrodes having different potentials and a separator to prevent an electrical short circuit between the two electrodes, and then injecting an electrolyte that transfers lithium ions to the two electrodes. Most of the electrolytes used are organic electrolytes in which a lithium salt is dissolved in an organic solvent.

[0005] In such lithium secondary batteries, if an internal short circuit caused by foreign substances or an external short circuit caused by penetration of materials such as nails occurs, a large current may flow, potentially leading to heat generation or explosion, so improving safety is considered important.

[0006] Therefore, there is a need for technological development to ensure the safety of secondary batteries. Prior art literature

[0008] Republic of Korea Published Patent No. 10-2016-0091732 The problem to be solved

[0009] The present invention aims to solve the above-mentioned problems by providing an electrode assembly with enhanced safety capable of improving safety by reducing heat generation even if an internal or external short circuit occurs, a lithium secondary battery including the same, a battery module including the lithium secondary battery, and a battery pack. means of solving the problem

[0011] To solve the aforementioned problem, an electrode assembly with improved safety is provided. In one example, an electrode assembly for a lithium secondary battery according to the present invention comprises a positive electrode; a negative electrode; and a separator disposed between the positive electrode and the negative electrode. In a specific example, the electrode assembly according to the present invention is characterized in that, in one or more of the positive electrode and the negative electrode, the composite layer is located on the same plane and includes first and second regions satisfying the following condition 1, a polymer resin layer is formed on one surface of the first region, and the separator is disposed in a region excluding the first region.

[0012] [Condition 1]

[0013] R1 > R2

[0014] In condition 1, R1 and R2 represent the electrical resistance of the first and second regions, respectively.

[0015] In a specific example, the first and second regions each include an active material, a conductive material, and a binder resin, and can satisfy the following condition 2.

[0016] [Condition 2]

[0017] C1 < C2

[0018] In condition 2, C1 and C2 represent the conductive material content of the first and second regions, respectively.

[0019] For example, the conductive material content of the first region may contain 20 to 70% relative to the conductive material content of the second region.

[0020] In addition, the first area may be a structure formed in an area of ​​5% or more based on the total area of ​​the composite layer.

[0021] In addition, the melting temperature of the polymer resin layer may be an average of 150°C or less.

[0022] In one example, the anode of the electrode assembly according to the present invention may include a composite layer satisfying condition 1.

[0023] In a specific example, the positive and negative electrodes may be arranged such that electrode tabs are formed extending from a current collector, with each electrode tab facing in opposite directions. At this time, the first region of the positive electrode may be a structure formed along one or more of the two sides adjacent to the region opposite the electrode tab or the region where the electrode tab is formed.

[0024] In another example, the cathode may include a composite layer satisfying condition 1.

[0025] In a specific example, the positive and negative electrodes may be arranged such that electrode tabs are formed extending from a current collector, with each electrode tab facing in opposite directions. In this case, the first region of the negative electrode may be a structure formed along one or more of the region where the electrode tab is formed, the region opposite to the electrode tab, or two sides adjacent to the side where the electrode tab is formed.

[0026] In another example, the anode and cathode may each include a composite layer satisfying condition 1. In this case, the first regions of the anode and cathode may be positioned facing each other.

[0027] In a specific example, the anode and cathode may be arranged such that electrode tabs are formed extending from a current collector, with each electrode tab facing in opposite directions. In this case, the first region of the anode may be a structure formed along one or more of the two sides adjacent to the region opposite the electrode tab or the region where the electrode tab is formed. Additionally, the first region of the cathode may be a structure formed along one or more of the two sides adjacent to the region where the electrode tab is formed, the region opposite the electrode tab, or the side where the electrode tab is formed.

[0028] Meanwhile, the electrode assembly is characterized by being stacked or stacked / folded.

[0030] In addition, the present invention provides a lithium secondary battery comprising the electrode assembly described above. In a specific example, the lithium secondary battery according to the present invention may include the electrode assembly described above; and a pouch case housing the electrode assembly.

[0032] In addition, the present invention provides a battery module including the secondary battery described above.

[0034] Furthermore, the present invention provides a battery pack comprising the battery module described above.

[0035] In a specific example, the above battery pack can be used as a power source for medium to large devices. Effects of the invention

[0037] In the electrode assembly according to the present invention, when an internal or external short circuit occurs, the polymer resin layer melts, causing the first region of the positive electrode and the negative electrode to come into contact and generate a short circuit. At this time, the first region with high resistance acts as a resistive part, thereby reducing the amount of heat generated and explosive force, which can improve the safety of the lithium secondary battery.

[0038] Accordingly, the present invention can provide an electrode assembly with improved safety, a lithium secondary battery including the same, a battery module including the lithium secondary battery, and a battery pack. Brief explanation of the drawing

[0040] FIG. 1 is a cross-sectional view of an electrode assembly according to the present invention. FIG. 2 is an exploded perspective view of an electrode assembly according to the present invention. FIGS. 3 and 4 are cross-sectional views of an anode included in an electrode assembly according to the present invention. FIG. 5 is a cross-sectional view of an electrode assembly according to the present invention. FIG. 6 is a cross-sectional view of an electrode assembly according to the present invention. Specific details for implementing the invention

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

[0042] However, this is not intended to limit the invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0043] In the present invention, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0044] Furthermore, in the present invention, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately above" the other part, but also cases where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only cases where it is "immediately below" the other part, but also cases where there is another part in between. Additionally, in the present application, being "placed on" may include cases where it is placed on the lower part as well as on the upper part.

[0046] The present invention provides an electrode assembly with improved safety, a lithium secondary battery including the same, a battery module including the lithium secondary battery, and a battery pack.

[0047] In one example, an electrode assembly according to the present invention comprises an anode; a cathode; and a separator disposed between the anode and the cathode, wherein the anode and the cathode are configured to include a current collector and a composite layer formed on one or both sides of the current collector. In a specific example, in one or more of the anode and the cathode, the composite layer is located on the same plane and includes first and second regions satisfying the following condition 1, wherein a polymer resin layer is formed on one side of the first region, and the separator is structured to be disposed in a region excluding the first region:

[0048] [Condition 1]

[0049] R1 > R2

[0050] In condition 1, R1 and R2 represent the electrical resistance of the first and second regions, respectively.

[0051] In particular, when the internal temperature of the battery in the electrode assembly according to the present invention rises abnormally, the polymer resin layer melts, causing the first region of the electrode to come into contact with the composite layer of opposite electrodes, thereby causing a short circuit. At this time, the first region, which is a high-resistance region where current is not concentrated, comes into contact with one side of the opposite electrode, thereby causing a short circuit of relatively low energy. This has the advantage of improving the safety of the battery by reducing heat generation and explosive force through the high-resistance first region acting as a resistive part.

[0053] Hereinafter, with reference to the drawings, an electrode assembly with improved safety including an insulating coating portion according to the present invention, a lithium secondary battery including the same, a battery module including the lithium secondary battery, and a battery pack will be described in detail.

[0055] [First embodiment]

[0056] The present invention provides an electrode assembly with improved safety as a first embodiment. Specifically, the electrode assembly of the first embodiment may include a first and second region in which the composite layer of the anode satisfies condition 1.

[0058] electrode assembly

[0059] FIG. 1 is a cross-sectional view of an electrode assembly according to the present invention, FIG. 2 is an exploded perspective view of an electrode assembly according to the present invention, and FIG. 3 to 4 are cross-sectional views of an anode included in an electrode assembly according to the present invention.

[0060] Referring to FIGS. 1 and 2, the electrode assembly (100) according to the present invention comprises an anode (110), a cathode (120), and a separator (130) located between the anode (110) and the cathode (120). Specifically, the anode (110) and the cathode (120) each comprise a current collector (111, 121) and a composite layer (112, 122) formed on one or both sides of the current collector (111, 121), and may have a structure in which an electrode tab (114, 124) extending from the current collector (111, 121) is formed. Meanwhile, in the drawings, the anode and the cathode (110, 120) are depicted such that the composite layer (112, 122) is formed on both sides of the current collector (111, 121), but is not limited thereto.

[0061] At this time, the positive electrode (110) of the electrode assembly (100) according to the present invention may include first and second regions (1121, 1122) located on the same plane, and the first and second regions (1121, 1122) may satisfy the following condition 1.

[0062] [Condition 1]

[0063] R1 > R2

[0064] In condition 1, R1 and R2 represent the electrical resistance of the first and second regions, respectively.

[0065] In a specific example, the first region (1121) and the second region (1122) exhibit different resistance characteristics, and the first region (1121) may be designed to exhibit higher resistance than the second region (1122).

[0066] In one example, the first region (1121) of the composite layer (112) may not participate in the normal charge / discharge reaction of the battery because it is insulated by the polymer resin layer (113). However, the first region (1121) and the second region (1122) may generate heat rapidly as the internal temperature of the battery rises abnormally, causing damage to the battery such as a short circuit, which concentrates the current in a localized area of ​​low resistance. Here, the abnormal rise in the internal temperature of the battery does not mean a rise in the temperature of the battery cell including the electrode formed in the first and second regions, but rather an abnormal rise in temperature around the battery cell to which the electrode is applied.

[0067] At this time, in the present invention, the composite layer (112) is designed to have a low resistance region and a high resistance region distributed therein, so that when the internal temperature of the battery rises abnormally, the first region (1121), which is a high resistance region where current is not concentrated, comes into contact with one side of the negative electrode (120), thereby allowing a relatively low short circuit to occur.

[0068] In other words, the present invention aims to reduce explosive power by lowering the energy of a secondary battery before thermal runaway (TR) by generating a relatively low-intensity short circuit in a first region when the internal temperature of the battery rises abnormally.

[0069] In this way, when the internal temperature of the battery rises abnormally, the present invention causes a short circuit to occur when the first region comes into contact with the composite layer (122) of the negative electrode (120), and the movement of current is induced to the second region (1122), so that a relatively low short circuit occurs in the first region (1121), thereby reducing the explosive force.

[0070] Meanwhile, the structure is such that a polymer resin layer (113) is formed on one side of the positive electrode (110), and the separator (130) disposed between the positive electrode (110) and the negative electrode (120) may be disposed in an area excluding the first region (1121). In particular, if the internal temperature of the battery rises abnormally, the polymer resin layer (113) may melt, causing the first region (1121) of the positive electrode (110) to come into contact with the composite layer (122) of the negative electrode (120), thereby causing a short circuit. A detailed description of the polymer resin layer (113) will be provided later.

[0072] As previously explained, the first and second regions (1121, 1122) have different resistances from each other, but the first region (1121) has a higher resistance. At this time, the resistance values ​​of each region can be set differently by making the content of the conductive material in the first and second regions different.

[0073] In a specific example, the first and second regions (1121, 1122) are a positive composite layer (112) comprising a positive active material, a conductive material, and a binder resin. At this time, the conductive material may satisfy the following condition 2.

[0074] [Condition 2]

[0075] C1 < C2

[0076] In condition 2, C1 and C2 represent the conductive material content of the first and second regions, respectively.

[0077] Condition 2 above means designing the resistance value of the first region (1121) to be high by administering less conductive material content in the first region (1121) compared to the content in the second region (1122).

[0078] Specifically, the conductive material content of the first region (1121) may contain 20 to 70% relative to the conductive material content of the second region (1122). More specifically, the conductive material content of the first region (1121) may contain 30% to 65%; 35% to 60%; 40% to 55%; or about 50% relative to the conductive material content of the second region (1122). If the conductive material content of the first region (1121) is too low relative to the conductive material content of the second region (1122), the movement of current is low, making it difficult to cause a short circuit even when the internal temperature of the battery rises abnormally; and if the conductive material content of the first region (1121) is too high relative to the conductive material content of the second region (1122), ignition due to a short circuit may occur.

[0079] Meanwhile, the first region (1121) may be included in an area of ​​5% or more based on the total area of ​​the anode composite layer (112). In a specific example, the first region (1121) may be included in an area of ​​5% or more; 5% to 20%; 6% to 18%; 7% to 16%; 8% to 14%; 10% or 5% based on the total area of ​​the anode composite layer (112). If the area of ​​the first region (1121) is too large, the area that does not participate in normal charge / discharge reactions is too large, and energy loss may occur. In addition, if the area of ​​the first region (1121) is too small, a short circuit may occur in the first region (1121) in contact with the composite layer (122) of the negative electrode (120) when the temperature of the battery rises abnormally, but a problem may arise where it is difficult to sufficiently lower the energy until the thermal runaway temperature is reached because the area of ​​the first region (1121) is too small.

[0080] Additionally, the melting temperature of the polymer resin layer (113) disposed on one side of the first region (1121) may be an average of 150°C or less. Specifically, the melting temperature of the polymer resin layer (113) may be 40°C to 140°C; 45°C to 120°C; 45°C to 100°C; or 45°C to 70°C. However, the melting temperature of the polymer resin layer (113) is not limited thereto and may be changed depending on the type of polymer resin layer (113).

[0081] If the melting temperature of the polymer resin layer (113) is too low, the polymer resin may melt within the temperature range where the battery operates normally, causing the positive electrode (110) and the negative electrode (120) to come into contact with each other and cause a short circuit. If the melting temperature of the polymer resin layer (113) is too high, the polymer resin may not melt even when the internal temperature of the battery rises abnormally, and problems such as heat transfer or fire may occur.

[0082] In addition, a separator (130) is not placed in the area where the polymer resin layer (113) is located, and the polymer resin layer (113) can prevent a hard short that occurs instantaneously during normal operation of the battery. In a specific example, the polymer resin layer (113) may be a polymer material such as PVdF-co-HFP, polyethylene, and polypropylene, or may be a polymer wax. For example,

[0083] Meanwhile, the separator (130) may be interposed between the anode (110) and the cathode (120), and may be placed in an area excluding the first region (1121) of the anode (110) composite layer (112). The separator (130) may be an insulating thin film having high ion permeability and mechanical strength. The separator (130) is not particularly limited as long as it is commonly used in the industry, but specifically, a sheet or nonwoven fabric made of chemically resistant and hydrophobic polypropylene; glass fiber; or polyethylene may be used, and in some cases, a composite separator (130) in which inorganic particles / organic particles are coated by an organic binder polymer on a porous polymer substrate such as the sheet or nonwoven fabric may be used. When a solid electrolyte such as a polymer is used as the electrolyte, the solid electrolyte may also serve as the separator. In addition, the pore diameter of the above-mentioned membrane may be an average of 0.01 to 10 μm, and the thickness may be an average of 5 to 300 μm. For example, the above-mentioned membrane (130) may be a composite membrane coated with an organic binder polymer such as polyvinylidene fluoride (PVdF) or styrene butadiene rubber (SBR).

[0085] In the present invention, the positive electrode (110) and the negative electrode (120) have a structure in which electrode tabs (114, 124) extending from a current collector (111, 121) are formed, and each electrode tab (114, 124) may be arranged to face in opposite directions.

[0086] Referring to FIG. 3, the anode (110) includes first and second regions (1121, 1122), and the first region (1121) may represent a structure formed on the opposite side of the electrode tab (114). Additionally, referring to FIG. 4, the first region (1121) may represent a structure formed along one or more of two sides adjacent to the region where the electrode tab (114) of the anode is formed. However, the structure of the first and second regions is not limited thereto. Furthermore, the first and second regions (1121, 1122) may be arranged in various forms.

[0087] Meanwhile, the first region (1121) is not placed in the region where the electrode tab (114) is formed. Specifically, the separator (130) is placed in the region excluding the first region (1121). If the first region (1121) is placed in the composite layer (112) of the region where the electrode tab (114) is formed, the electrode tab (114) comes into contact with the composite layer (122) of the negative electrode (120), making normal charging and discharging impossible and potentially causing a short circuit of high intensity.

[0088] The electrode assembly (100) according to the present invention can be stacked in various forms, for example, stacked in a stacked type, stacked / folded type, etc., and preferably has a stacked structure. Electrode tabs extend from each electrode plate of the electrode assembly, and electrode leads are electrically connected to a plurality of electrode tabs extending from each electrode plate, for example by welding, and are exposed to the outside of the pouch.

[0089] In the present invention, the electrode may be laminated together with a conventional electrode having an electrode active material layer formed on both sides of a current collector to form a unit cell such as a bi-cell or a mono-cell. In a specific example, the electrode assembly in the secondary battery according to the present invention may include one or more types selected from the group consisting of a mono-cell and a bi-cell. More specifically, a mono-cell is a unit cell in which electrodes of opposite polarities are arranged on both sides of the unit cell. Furthermore, a bi-cell is a unit cell in which the same polarity is arranged on both sides of the cell, such as a unit structure of positive electrode / separator / negative electrode / separator / positive electrode and a unit structure of negative electrode / separator / positive electrode / separator / negative electrode. For such mono-cells and bi-cells, as long as the electrodes on both sides of the unit cell have the same structure, the number of positive and negative separators forming them is not particularly limited.

[0091] [Second embodiment]

[0092] The present invention provides an electrode assembly with improved safety as a second embodiment. Specifically, the electrode assembly of the first embodiment may include first and second regions in which the composite layer of the cathode satisfies condition 1.

[0094] electrode assembly

[0095] FIG. 5 is a cross-sectional view of an electrode assembly according to the present invention. Referring to FIG. 5, the electrode assembly (200) according to the present invention comprises an anode (210), a cathode (220), and a separator (230) located between the anode (210) and the cathode (220). Specifically, the anode (210) and the cathode (220) each comprise a current collector (211, 221) and a composite layer (212, 222) formed on one or both sides of the current collector (211, 221), and may have a structure in which an electrode tab (214, 224) extending from the current collector (211, 221) is formed.

[0096] At this time, the cathode (220) of the electrode assembly (200) according to the present invention may include first and second regions (2121, 2122) located on the same plane, and the first and second regions (2121, 2122) may satisfy the following condition 1. In addition, a polymer resin layer (213) is formed on one side of the first region (2121), and a separator (230) may be disposed in the region excluding the first region (2121).

[0097] [Condition 1]

[0098] R1 > R2

[0099] In condition 1, R1 and R2 represent the electrical resistance of the first and second regions (2121, 2122), respectively.

[0100] In a specific example, the first region (2121) and the second region (2122) exhibit different resistance characteristics, and the first region (2121) may be designed to exhibit higher resistance than the second region (2122).

[0101] Meanwhile, the positive electrode (210) and the negative electrode (220) have a structure in which electrode tabs (214, 224) extending from current collectors (211, 221) are formed, and each electrode tab (214, 224) can be arranged to face in opposite directions.

[0102] In addition, the first region (2121) of the above-mentioned cathode (220) may be formed along one or more of the two sides adjacent to the side where the electrode tab (224) is formed, the side opposite to the electrode tab (224), or the side where the electrode tab (224) is formed. Meanwhile, the first region (2121) of the cathode (220) may be placed in the area where the electrode tab (224) is formed. Due to this structure, even if the separator (230) is not placed at the location where the electrode tab (224) is formed, the electrode tab (224) of the cathode (220) may not come into contact with the composite layer (212) of the anode (210) because the cathode (220) is larger than the anode (210).

[0103] Generally, since the resistance of the anode (210) is the highest, a hard short occurs when the electrode tab (214) of the anode (210) and the composite layer (222) of the cathode (220) come into contact, and a short of relatively low intensity occurs when the composite layer (222) of the anode (210) and the electrode tab (224) of the cathode (220) come into contact. Meanwhile, since the electrode assembly (200) is designed so that the area of ​​the cathode (220) is larger than that of the anode (210), the electrode tab (224) of the cathode (220) may not come into contact with the composite layer (212) of the anode (210). However, in order to cause a short circuit when the ambient temperature of the cathode (220) including the first and second regions (2121, 2122) rises, the composite layer (212, 222) of the anode (210) and the cathode (220) must come into contact with each other, so the first region (2121) may be formed in one of all regions except for the position corresponding to the anode tab (214).

[0105] As the description of each component has been provided earlier, a detailed explanation of each component will be omitted.

[0106] As previously explained, in the case where the internal temperature of the battery of the electrode assembly (200) according to the present invention rises abnormally, the polymer resin layer (213) melts, and the first region (2121) of the negative electrode (220) comes into contact with the composite layer (212) of the positive electrode (210), thereby causing a short circuit. At this time, the first region (2121), which is a high-resistance region where current is not concentrated, comes into contact with one side of the positive electrode (210), thereby causing a short circuit of relatively low energy. This has the advantage that the safety of the battery can be improved by reducing the amount of heat and explosive force through the high-resistance first region (2121) acting as a resistance part.

[0108] [Third Embodiment]

[0109] The present invention provides an electrode assembly with improved safety in a third embodiment. Specifically, the electrode assembly of the third embodiment may include first and second regions in which a composite layer of an anode and a cathode satisfies condition 1.

[0111] electrode assembly

[0112] FIG. 6 is a cross-sectional view of an electrode assembly according to the present invention. Referring to FIG. 6, the electrode assembly (300) according to the present invention comprises an anode (310), a cathode (320), and a separator (330) located between the anode (310) and the cathode (320). Specifically, the anode (310) and the cathode (320) each comprise a current collector (311, 321) and a composite layer (312, 322) formed on one or both sides of the current collector (311, 321), and may have a structure in which an electrode tab (314, 324) extending from the current collector (311, 321) is formed.

[0113] At this time, the positive electrode (310) and the negative electrode (320) of the electrode assembly (300) according to the present invention may include a composite layer (312, 322) satisfying condition 1. The first and second regions (3121, 3122) may be located on the same plane. In addition, a polymer resin layer (313) is formed on one side of the first region (3121), and a separator (330) may be disposed in the region excluding the first region (3121).

[0114] [Condition 1]

[0115] R1 > R2

[0116] In condition 1, R1 and R2 represent the electrical resistance of the first and second regions (3121, 3122), respectively.

[0117] In a specific example, the first region (3121) and the second region (3122) exhibit different resistance characteristics, and the first region (3121) may be designed to exhibit higher resistance than the second region (3122).

[0118] Additionally, the first region (3121) of the anode (310) and cathode (320) may be positioned facing each other.

[0119] Meanwhile, the anode (310) and cathode (320) have a structure in which electrode tabs (314, 324) extending from current collectors (311, 321) are formed, and each electrode tab (314, 324) can be arranged to face in opposite directions.

[0120] In addition, the first region (3121) of the anode (310) may be a structure formed along one or more of the two sides adjacent to the region opposite the electrode tab (314) or the region where the electrode tab (314) is formed. Here, the two sides adjacent to the region where the electrode tab (314) is formed refer to a region formed in a direction orthogonal to the electrode tab (314).

[0121] Furthermore, the first region (3121) of the cathode (320) may be formed along one or more of the following sides: the region where the electrode tab (324) is formed, the region opposite to the electrode tab (324), or the two sides adjacent to the side where the electrode tab (324) is formed. However, as previously described, the first region (3121) of the anode (310) and the cathode (320) may be positioned in a region facing each other.

[0122] As the description of each component has been provided earlier, a detailed explanation of each component will be omitted.

[0123] As previously explained, in the case where the internal temperature of the battery of the electrode assembly (300) according to the present invention rises abnormally, the polymer resin layer (313) melts, and the first region (3121) of the negative electrode (320) comes into contact with the composite layer (312) of the positive electrode (310), thereby causing a short circuit. At this time, the first region (3121), which is a high-resistance region where current is not concentrated, comes into contact with one side of the positive electrode (310), thereby causing a short circuit of relatively low energy. This has the advantage that the safety of the battery can be improved by reducing the amount of heat and explosive force through the high-resistance first region (3121) acting as a resistance part.

[0125] lithium secondary battery

[0126] In addition, the present invention provides a lithium secondary battery comprising the electrode assembly described above. In a specific example, the lithium secondary battery according to the present invention comprises the electrode assembly described above; and a pouch case housing the electrode assembly.

[0127] The above pouch is typically made of an aluminum laminate sheet and can provide a space for accommodating an electrode assembly. Meanwhile, the electrode leads are drawn out to the outside of the pouch and may extend in the same direction or in opposite directions.

[0128] A lithium secondary battery according to the present invention may include the electrode assembly described above. In particular, when the ambient temperature of the electrode assembly rises abnormally, the polymer resin layer may melt, causing the first region of the positive electrode and the negative electrode to come into contact and cause a short circuit. At this time, the first region with high resistance acts as a resistance part to reduce heat generation and explosive force, thereby improving the safety of the lithium secondary battery.

[0130] Battery modules and battery packs

[0131] The present invention provides a battery module comprising the secondary battery described above. In addition, the present invention provides a battery pack comprising the battery module.

[0133] In one example, the lithium secondary battery according to the present invention can be used, in particular, in a high-output, high-capacity battery requiring a long lifespan and excellent durability, or in a battery module or battery pack comprising a plurality of such batteries as unit cells.

[0134] In a specific example, when an event such as a temperature rise occurs in one of the multiple lithium secondary batteries in the battery module or battery pack, the electrode assembly included in the lithium secondary battery described above may cause the polymer resin layer to melt due to the surrounding temperature rise, and the first region of the positive electrode and the negative electrode may come into contact, thereby causing a short circuit. At this time, by causing a short circuit of low intensity in the first region, the energy of the lithium secondary battery can be lowered before thermal runaway, thereby reducing the explosive force.

[0135] The above battery pack can be used as a power source for medium-to-large devices requiring high temperature stability, long cycle characteristics, and high rate characteristics. Specific examples of such medium-to-large devices include power tools that are powered by an electric motor; electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (PHEVs); electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters (E-scooters); electric golf carts; electric trucks; electric commercial vehicles; or power storage systems.

[0136] The structure and manufacturing method of such medium-to-large battery modules or medium-to-large battery packs are known in the art, so a detailed description thereof will be omitted.

[0138] The present invention will be explained in more detail below through examples and experimental examples.

[0139] However, the following examples and experimental examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and experimental examples.

[0141] Example 1

[0142] LiNi as a positive electrode active material 0.8 Co 0.1 Mn 0.1 A slurry for an anode composite layer was prepared by weighing 295 parts by weight of O2, 3.5 parts by weight of carbon black as a conductive material, and 1.5 parts by weight of PVdF as a binder, and mixing them in an N-methylpyrrolidone (NMP) solvent.

[0143] Then, the slurry for the anode composite layer was applied to a current collector with a thickness of 12 μm, dried at 130°C, and rolled to manufacture an anode.

[0144] Lithium metal was prepared as the anode and counter electrode, and a polypropylene separator was placed between them. Then, a coin half cell was manufactured using an electrolyte of ethylene carbonate / dimethyl carbonate / LiPF6 (EC / DMC=1 / 1).

[0146] Comparative Example 1

[0147] LiNi as a positive electrode active material 0.8 Co 0.1 Mn 0.1 A coin half cell was prepared in the same manner as in Example 1, except that 6.8 parts by weight of O29, 1.7 parts by weight of carbon black as a conductive material, and 1.5 parts by weight of PVdF as a binder were weighed and mixed in an N-methylpyrrolidone (NMP) solvent to prepare a slurry for the composite layer.

[0149] Resistance measurement experiment

[0150] After fixing the battery cells manufactured in the examples and comparative examples to a cell jig equipped with a heating pad, thermal runaway of the battery cells was induced by applying abnormal heat to each battery cell using the heating pad.

[0151] And, the results are shown in Table 1 below.

[0153] Cell data Experimental results Positive MP resistance (mΩ / cm) 2 ) DCIR(mΩ) TR starting temperature Total burning time Example 1 130-150 1.19 263℃ 170 sec Comparative Example 1 20-30 1.09 233℃ 157 sec

[0154] Referring to Table 1, the total thermal runaway (TR) temperature of Example 1 was about 30 degrees higher. Through this, it was confirmed that the thermal safety of Example 1 was increased.

[0155] In addition, the total combustion time of the battery cell in Example 1 increased by about 13 seconds compared to Comparative Example 1. Assuming that Example 1 and Comparative Example 1 are battery cells with the same capacity and emit the same energy, the increase in combustion time can be interpreted as the intensity of the flame being weakened.

[0156] As can be seen in the table above, the present invention has the effect of improving safety by reducing heat generation even if an internal or external short circuit occurs in the battery.

[0158] The present invention has been described in more detail above through drawings and embodiments. However, the configurations described in the drawings or embodiments described in this specification are merely one embodiment of the present invention and do not represent all technical concepts of the present invention; therefore, it should be understood that various equivalents and modifications that can replace them may exist at the time of filing this application. Explanation of the symbols

[0160] 100, 200, 300: Electrode assembly 110, 210, 310: Positive electrode 111, 211, 311: Positive current collector 112, 212, 312: Anode composite layer 1121, 2121, 3121: First Zone 1122, 2122, 3122: Second Zone 113, 213, 313: Polymer resin layer 114, 214, 314: Positive tab 120, 220, 320: Cathode 121, 221, 321: Positive current collector 122, 222, 322: Cathode composite layer 124, 224, 324: Negative tab 130, 230, 330: Separator

Claims

Claim 1 An electrode assembly comprising an anode; a cathode; and a separator disposed between the anode and the cathode, wherein the anode and the cathode each comprise a current collector and a composite layer formed on one or both sides of the current collector, wherein in one or more of the anode and the cathode, the composite layer comprises first and second regions located on the same plane and satisfying the following condition 1, wherein a polymer resin layer is formed on one side of the first region, and the separator has a structure disposed in a region excluding the first region, wherein the first and second regions each comprise an active material, a conductive material, and a binder resin, and the conductive material content of the first region contains 20 to 70% relative to the conductive material content of the second region: [Condition 1] R1 > R2 In Condition 1, R1 and R2 represent the electrical resistance of the first and second regions, respectively. Claim 2 delete Claim 3 delete Claim 4 In claim 1, the first region is an electrode assembly having a structure formed in an area of ​​5% or more based on the total area of ​​the composite layer. Claim 5 An electrode assembly according to claim 1, wherein the melting temperature of the polymer resin layer is an average of 150°C or less. Claim 6 In claim 1, the anode is an electrode assembly having a structure including a composite layer satisfying condition 1. Claim 7 An electrode assembly according to claim 6, wherein the positive and negative electrodes are formed such that electrode tabs extending from a current collector are arranged so that each electrode tab faces in opposite directions, and the first region of the positive electrode is formed along one or more of the two sides adjacent to the region opposite to the electrode tab or the region where the electrode tab is formed. Claim 8 In claim 1, the cathode is an electrode assembly having a structure including a composite layer satisfying condition 1. Claim 9 An electrode assembly according to claim 8, wherein the positive and negative electrodes are formed such that electrode tabs extending from a current collector are arranged so that each electrode tab faces in opposite directions, and the first region of the negative electrode is formed along one or more of the regions where the electrode tab is formed, regions opposite to the electrode tab, or two sides adjacent to the side where the electrode tab is formed. Claim 10 An electrode assembly according to claim 1, wherein the anode and the cathode each comprise a composite layer satisfying condition 1, and the first regions of the anode and the cathode are positioned facing each other. Claim 11 An electrode assembly according to claim 10, wherein the positive and negative electrodes are formed such that electrode tabs extending from a current collector are arranged so that each electrode tab faces in opposite directions, and the first region of the positive electrode is a structure formed along one or more of two sides adjacent to the region opposite to the electrode tab or the region where the electrode tab is formed, and the first region of the negative electrode is a structure formed along one or more of two sides adjacent to the region where the electrode tab is formed, the region opposite to the electrode tab, or the side where the electrode tab is formed. Claim 12 In claim 1, the electrode assembly is characterized by being stacked or stacked / folded. Claim 13 A lithium secondary battery comprising an electrode assembly according to claim 1; and a pouch case housing the electrode assembly. Claim 14 A battery module including a lithium secondary battery according to Paragraph 13. Claim 15 A battery pack including a battery module according to paragraph 14. Claim 16 In paragraph 15, the battery pack is a battery pack used as a power source for medium to large devices.

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