Secondary battery

Abstract

The present invention relates to a secondary battery in which an electrode assembly, comprising a plurality of laminates of positive electrodes, negative electrodes, and separators, is housed in a case, the electrode assembly being provided with a plurality of positive electrode tabs extending from the plurality of positive electrodes and a plurality of negative electrode tabs extending from the plurality of negative electrodes, wherein the positive electrode tabs form a positive electrode tab laminate in which the ends extending from the positive electrodes are laminated, a positive electrode tab connection part connecting a positive electrode and the positive electrode tab laminate form a first space of a set size with another neighboring positive electrode tab connection part, and a foam-coating part is attached to at least two of the positive electrode tab connection parts, the foam-coating part, comprising an inorganic foaming agent, expanding in volume within a first space when the temperature rises above a predetermined reference point.

Description

secondary battery

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0196775 filed on December 26, 2024, and all contents disclosed in the document of said Korean Patent Application are incorporated herein as part of this specification.

[0002] The present invention relates to a secondary battery capable of suppressing or minimizing damage caused by thermal runaway, wherein when a fire occurs externally or in an adjacent secondary battery and the temperature rises, an open circuit is induced in the positive or negative tab, thereby suppressing the occurrence of a short circuit.

[0003]

[0004] Demand for high-efficiency rechargeable batteries is rapidly increasing in sectors such as mobile devices and electric vehicles. Among these rechargeable batteries, lithium-ion batteries, which feature high energy density, the ability to maintain relatively high voltage, and a low self-discharge rate, have been commercialized and are widely used, while active research and development is underway to improve their performance.

[0005] Secondary batteries have a structure in which an electrode assembly and an electrolyte are housed within a case such as a can or a pouch.

[0006] Among these, the pouch-type secondary battery has a structure in which an electrode assembly (1) is mounted inside a pouch (7), as shown in FIG. 1a. At this time, the electrode assembly (1) has a structure in which a positive electrode (2), a separator (3), and a negative electrode (4) are repeatedly stacked. The positive electrode tabs (2ㅁ) extending from each positive electrode (2) are gathered together at their ends to form a positive electrode tab stacking section (2c) and are joined to a positive electrode lead (5), and the negative electrode tabs (4a) extending from each negative electrode (4) are gathered together to form a negative electrode tab stacking section (4c) and are joined to a negative electrode lead (6: see FIG. 5). Then, the ends of the positive electrode lead (5) and the negative electrode lead (6) protrude from the pouch (7) so that they can be electrically connected to the outside.

[0007] For reference, the positive electrode (2), separator (3), and negative electrode (4) may be stacked one by one, but they may also be manufactured into a unit cell (1a) in which the positive electrode (2), separator (3), and negative electrode (4) are stacked in a predetermined number, and then a plurality of unit cells (1a) may be stacked to form an electrode assembly (1). In addition, in FIG. 1b, the positive electrode tab connecting part (2b) connecting the positive electrode tab stacking part (2c) at the end of the positive electrode (2) is shown as being shortest at the bottom and longest at the top, but the opposite may be true, or the positive electrode tab connecting part (2b) of the positive electrode (2) located in the middle layer may be configured to be the shortest. Of course, the negative electrode (4) may also be configured in the same way.

[0008] Meanwhile, secondary batteries installed in vehicles, ESS (Energy Storage Systems), etc., are combined in multiple units to form a secondary battery module in order to increase output and electrical storage capacity, and multiple secondary battery modules are combined to form a secondary battery pack. That is, multiple secondary batteries are assembled to manufacture a secondary battery module, and multiple secondary battery modules are assembled to manufacture a secondary battery pack, which is then installed in vehicles, ESS, etc.

[0009] However, in secondary battery modules composed of multiple secondary batteries, there was a problem where if a fire occurred in even one of the batteries, the fire could spread to neighboring batteries and cause a series of explosions.

[0010] Furthermore, dust generated during a fire could come into contact with the electrode leads (positive and negative leads) of adjacent secondary batteries, causing an electrical short circuit and potentially accelerating thermal propagation (TP).

[0011] In particular, for secondary battery modules installed in means of transportation such as vehicles, the safety risk increases along with the increase in capacity and output. It was necessary to delay thermal runaway as much as possible to secure evacuation time for occupants even if a fire occurred in the secondary battery module.

[0012]

[0013] Accordingly, the main objective of the present invention is to provide a secondary battery capable of suppressing the occurrence of a fire caused by an electrical short circuit by disconnecting the electrode tabs (positive tab, negative tab) inside the case when a fire occurs (at an adjacent secondary battery or another point) or when overheating occurs due to other factors.

[0014]

[0015] The secondary battery of the present invention for achieving the aforementioned purpose is a secondary battery in which an electrode assembly, in which a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separators are repeatedly stacked, is embedded in a case, and comprises an electrode assembly having a plurality of positive electrode tabs extending from a plurality of positive electrodes and a plurality of negative electrode tabs extending from a plurality of negative electrodes.

[0016] At this time, the anode tabs form an anode tab stacking section in which the ends extending from each anode are stacked together, and the anode tab connecting section connecting the anodes and the anode tab stacking section forms a first space section having a predetermined size between adjacent anode tab connecting sections, and a foamed coating section is attached to at least two of the anode tab connecting sections, and the volume of the foamed coating section expands within the first space section when the temperature rises above a predetermined standard, and the foamed coating section is composed of an inorganic foaming agent.

[0017] Alternatively, the foamed coating portion may be coupled to the cathode tab in place of the anode tab or simultaneously with the anode tab.

[0018] That is, in the present invention, the cathode tabs form a cathode tab stacked portion formed by stacking the ends extended from each cathode, and the cathode tab connecting portion connecting the cathode and the cathode tab stacked portion forms a second space portion having a predetermined size between adjacent cathode tab connecting portions, and a foamed coating portion is attached to at least two of the cathode tab connecting portions, and the foamed coating portion expands in volume within the second space portion when the temperature rises above a predetermined standard, and the foamed coating portion is composed of an inorganic foaming agent.

[0019] In the present invention, the inorganic foaming agent contains at least one of lithium silicate, potassium silicate, sodium silicate, potassium silicate, zirconium silicate, magnesium silicate, titanium silicate, vermiculite, and perlite.

[0020] That is, the above-mentioned inorganic foaming agent can be manufactured using a component also known as water glass. Therefore, the foamed coating part (since it is manufactured using water glass as the main component) can be manufactured in a liquid state, applied or sprayed onto the anode tab or cathode tab, and then cured to bond.

[0021] The above-mentioned inorganic foaming agent is included in the foam coating portion in a range of 27.5 to 90 wt%.

[0022] In addition, the foamed coating part further includes a polymer resin, and the polymer resin is included in the foamed coating part in a range of 5 to 50 wt%.

[0023] The above polymer resin contains at least one of polyurethane resin, acrylic resin, cellulose-based resin, and synthetic rubber resin.

[0024] The above foamed coating part further includes an inorganic filler, and the inorganic filler is included in the foamed coating part in a range of 5 to 50 wt%.

[0025] The above-mentioned inorganic filler contains at least one of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide, and boehmite.

[0026] The above-mentioned foamed coating part expands to a final volume of at least 250% of its initial volume when the temperature rises above a predetermined standard (i.e., expands by at least 2.5 times the foaming rate).

[0027] In addition, the foamed coating part is configured so that volume expansion begins when it reaches 80℃.

[0028] Meanwhile, in the present invention, the foamed coating part coupled to one anode tab connection part and the foamed coating part coupled to another anode tab connection part expand to different volumes.

[0029] More specifically, among the anode tab connection parts to which the foam coating part is attached, the foam coating part attached to the shortest anode tab connection part has the thickest thickness, and the foam coating part attached to the longest anode tab connection part is attached to have the thinnest thickness.

[0030] Therefore, even if they have the same foaming rate, the foamed coating part connected to the shortest anode tab connection has a thicker thickness, and the foamed coating part connected to the longest anode tab connection has the thinnest thickness; thus, the foamed coating part connected to the shortest anode tab connection expands to have a larger volume, and the foamed coating part connected to the longest anode tab connection expands to have a smaller volume, resulting in expansion into different volumes.

[0031] In addition, as shown in FIG. 6, m anode tab connections are provided and a foam coating is attached to all anode tab connections, and when the anode tab connections at the outermost (i.e., the lowest and topmost) have the longest lengths (the intermediate layer anode tab connections have the shortest lengths), the thickness (T1) of the foam coating attached to the nth anode tab connection from bottom to top is calculated by the following formula.

[0032]

[0033] [formula]

[0034]

[0035]

[0036]

[0037] Similarly, the foamed coating part attached to one cathode tab connection and the foamed coating part attached to another cathode tab connection can expand to different volumes. That is, among the cathode tab connections to which the foamed coating part is attached, the foamed coating part attached to the shortest cathode tab connection has the thickest thickness, and the foamed coating part attached to the longest cathode tab connection is attached to have the thinnest thickness.

[0038] In addition, m cathode tab connections are provided, and a foam coating part is attached to all cathode tab connections, and when the outermost cathode tab connections (i.e., located at the bottom and top layers) have the longest length (the intermediate layer cathode tab connections have the shortest length), the thickness (T1) of the foam coating part attached to the nth cathode tab connection from bottom to top can be calculated by the following formula.

[0039] [formula]

[0040]

[0041]

[0042]

[0043] In addition, the present invention further provides a secondary battery module comprising a plurality of secondary batteries having the technical features described above.

[0044]

[0045] The secondary battery of the present invention having the above configuration is coupled with a foamed coating portion that expands in volume when the temperature rises above a predetermined standard on the positive tab and / or negative tab of the electrode assembly, so that when the internal or external temperature of the secondary battery rises, the disconnection of the positive tab or negative tab is induced, thereby preventing the occurrence of fire caused by a short circuit.

[0046] In the present invention, since the foamed coating part contains an inorganic foaming agent as a main component, compression does not occur after expansion, thereby reducing the possibility of failure of disconnection of the positive or negative tab.

[0047] In other words, organic foaming agents made of organic materials have a high probability of dispersing into the air in the form of gas after foaming, or even if they maintain a solid form, failing to resist external forces and thus failing to provide sufficient pressure to disconnect the positive or negative tab. However, since the foaming coating part of the present invention contains an inorganic foaming agent as a main component, it maintains a solid form and can provide sufficient pressure to disconnect the positive or negative tab (since compression occurs little or does not occur during foaming).

[0048] In the present invention, the inorganic foaming agent may be prepared in a liquid state to contain at least one of lithium silicate, also known as water glass, potassium silicate, sodium silicate, potassium silicate, zirconium silicate, magnesium silicate, titanium silicate, vermiculite, and perlite. Accordingly, it can be easily bonded to an anode tab or a cathode tab by coating or spraying.

[0049] In addition, in the present invention, the foam coating portion is configured such that the amount of expansion varies depending on the length of the connected positive tab connection portion or negative tab connection portion, thereby enabling more efficient disconnection.

[0050]

[0051] FIG. 1a is a drawing showing an electrode assembly mounted inside a pouch to manufacture a conventional pouch-type secondary battery.

[0052] FIG. 1b is a drawing showing a simplified view of a conventional electrode assembly.

[0053] FIG. 2 is a simplified drawing showing the appearance of an electrode assembly according to an embodiment of the present invention, showing a foamed coating portion combined with an anode tab connection portion.

[0054] FIG. 3 is a drawing showing the expanded foam coating portion in the structure of FIG. 2.

[0055] FIG. 4 is a table showing the foaming rate and foaming strength according to the weight % (wt%) of the foaming coating components.

[0056] FIG. 5 is a simplified drawing showing the appearance of an electrode assembly according to an embodiment of the present invention, showing the appearance of a foamed coating part coupled to a cathode tab connection part (top) and the appearance of the foamed coating part expanded (bottom).

[0057] FIG. 6 is a drawing showing the appearance of an electrode assembly in which a foamed coating portion is combined with all positive tab connections, the intermediate layer positive tab connections have the shortest length, and the outermost (topmost and bottommost) positive tab connections have the longest length.

[0058]

[0059] Hereinafter, the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement it. However, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0060] To clearly explain the present invention, parts unrelated to the explanation have been omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0061] Furthermore, terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0062] The present invention relates to a secondary battery capable of suppressing the occurrence of a fire caused by an electrical short circuit by disconnecting the electrode tabs (positive tab, negative tab) inside the case (pouch) when a fire occurs at an adjacent secondary battery or another point, or when overheating occurs due to other factors. Hereinafter, embodiments provided by the present invention will be described in more detail with reference to the attached drawings.

[0063] FIG. 2 is a simplified drawing showing the appearance of an electrode assembly according to an embodiment of the present invention, in which a foamed coating part is coupled to an anode tab connection part, and FIG. 3 is a drawing showing the foamed coating part expanded in the structure of FIG. 2. FIG. 4 is a table showing the foaming rate and foaming strength according to the weight% (wt%) of the foamed coating part components.

[0064] In addition, FIG. 5 is a simplified drawing showing the appearance of an electrode assembly according to an embodiment of the present invention, showing the appearance of a foamed coating part coupled to a negative tab connection part (top) and the appearance of the foamed coating part expanded (bottom), and FIG. 6 is a drawing showing the appearance of an electrode assembly in which a foamed coating part is coupled to all positive tab connection parts, the positive tab connection parts of the middle layer have the shortest length, and the positive tab connection parts of the outermost layer (topmost layer and bottommost layer) have the longest length.

[0065] The secondary battery provided in the present invention comprises an electrode assembly (1) in which a plurality of positive electrodes (2), a plurality of negative electrodes (4), and a plurality of separators (4) are repeatedly stacked in the order of positive electrode, separator, negative electrode, separator positive electrode (or, negative electrode, separator, positive electrode, separator negative electrode), and the electrode assembly is manufactured by being embedded in a case (along with an electrolyte). The case may be a pouch.

[0066] And, the electrode assembly (1) has a plurality of positive tabs (2a) extending from each positive electrode and a plurality of negative tabs (4a) extending from each negative electrode.

[0067] In the present invention, an electrode assembly having a foamed coating portion (E) combined with an anode tab is provided as an example.

[0068] That is, as shown in FIG. 2, the positive tab (2a) forms a positive tab stack (2c) formed by stacking the ends extending from each positive electrode (2). The positive tab stack (2c) is welded to a positive lead (5) with one end protruding outside the pouch.

[0069] At this time, the anode tab connecting part (2b) connecting the anode (2) and the anode tab stacking part (2c) forms a first space part (2d) as a space having a predetermined size between adjacent anode tab connecting parts (2b). That is, each anode (2) has a different stacking height, and since the ends of the anode tabs (2a) are gathered to form the anode tab stacking part (2c), a first space part (2d) is formed between each of the anode tab connecting parts (2b).

[0070] In addition, a foamed coating portion (E) is attached to at least two, preferably all, of the anode tab connection portions (2b). Here, 'attachment' means a state in which they are attached without being separated through application or coating.

[0071] That is, in the present invention, the foamed coating part (E) can be bonded by being manufactured in a liquid state, then applied or sprayed onto the positive electrode tab (2a) or negative electrode tab (2b), and then cured. In the present invention, the foamed coating part (E) can be bonded by being manufactured in a liquid, gel, or sol state, then applied or sprayed onto a target location and then cured, and can be bonded by being applied or sprayed during the manufacturing step of the positive electrode (2) or negative electrode (4) before being manufactured into an electrode assembly (1).

[0072] When the temperature of the foamed coating part (E) rises above a predetermined standard, the volume expands within the first space part (2d) as shown in FIG. 3.

[0073] In the present invention, a foamed coating portion (F) may be combined with the negative electrode tab (4a) in place of or simultaneously with the positive electrode tab (2a). Accordingly, the present invention provides a structure in which the foamed coating portion (F) is combined with the negative electrode tab (4a) as another embodiment.

[0074] That is, as illustrated in FIG. 1a, the positive electrode tab (2a) and the negative electrode tab (4a) can be formed with the same structure, so the negative electrode tab (4a) included in the electrode assembly (1) forms a negative electrode tab stacking portion (4c) in which the ends extending from each negative electrode (4) are stacked together, just like the positive electrode tab, and the negative electrode tab connecting portion (4b) connecting the negative electrode (4) and the negative electrode tab stacking portion (4c) forms a second space portion (4d) as a space having a predetermined size between it and an adjacent negative electrode tab connecting portion (4b).

[0075] As shown in FIG. 5, the negative tab connection part (4b) also has a foamed coating part (F) attached at least in two places, and the foamed coating part (F) expands in volume within the second space part (4d) when the temperature rises above a predetermined standard.

[0076] Meanwhile, in the present invention, the foamed coating part (E, F) contains an inorganic foaming agent as a main component.

[0077] In other words, organic foaming agents made of organic materials have a high probability of dispersing into the air in the form of gas after foaming, or even if they maintain a solid form, they cannot resist external forces and thus cannot provide sufficient pressure to disconnect the positive tab (2a) or negative tab (2b). However, since the foaming coating part (E, F) of the present invention contains an inorganic foaming agent as a main component, it maintains a solid form and can provide sufficient pressure to disconnect the positive tab or negative tab (since compression occurs little or does not occur during foaming).

[0078] Therefore, in the present invention, since no compression occurs after the foamed coating portions (E, F) expand, the possibility of failure of the wire breaking of the positive tab (2a) or negative tab (4a) can be reduced. Also, in FIGS. 2, 3, and 5, the foamed coating portions (E, F) are shown arranged side by side (regularly) with the positive tab or negative tab in between, but they may be arranged offset from each other (irregularly) to promote wire breaking. If the configuration is such that pressure is applied to the corner portion of the expanded foamed coating portion on one side of a point of the positive tab connection portion (2b) or negative tab connection portion (4b), and pressure is applied to the corner portion of the expanded foamed coating portion on the opposite side, wire breaking can be further promoted.

[0079] In the present invention, the inorganic foaming agent contains at least one of the components also known as water glass, namely lithium silicate, potassium silicate, sodium silicate, potassium silicate, zirconium silicate, magnesium silicate, titanium silicate, vermiculite, and perlite. Accordingly, as described above, the foamed coating portion (E, F) can be manufactured in a liquid state, applied or sprayed onto the positive or negative tab, and then cured to bond.

[0080] The above inorganic foaming agent is included in the foam coating portion (E, F) in a range of 27.5 to 90 wt%. Preferably, the above inorganic foaming agent (E, F) may be included in an amount of 40 wt% or more, 50 wt% or more, 55 wt% or more, or 60 wt% or more, and may also be 85 wt% or less, 80 wt% or less, or 75 wt% or less.

[0081] In addition, the foamed coating portion further comprises an inorganic filler, and the inorganic filler is included in the foamed coating portion in a range of 5 to 50 wt%. Preferably, the inorganic filler may be included in the foamed coating portion in an amount of 10 wt% or more, 15 wt% or more, 18 wt% or more, or 20 wt% or more, and may also be included in an amount of 45 wt% or less, 40 wt% or less, 35 wt% or less, or 30 wt% or less. The inorganic filler contains at least one of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide, and boehmite.

[0082] The foamed coating portion (E, F) expands to a final volume of at least 250% of its initial volume when the temperature rises above a predetermined standard. Additionally, the foamed coating portion is configured to begin volume expansion when it reaches 80℃.

[0083] In addition, the foamed coating portion (E, F) further comprises a polymer resin, and the polymer resin may be included in the foamed coating portion in a range of 5 to 50 wt%. Preferably, the polymer resin may be included in the foamed coating portion in an amount of 6 wt% or more, 8 wt% or more, 9 wt% or more, 10 wt% or more, or 12 wt% or more, and may also be included in an amount of 40 wt% or less, 35 wt% or less, 30 wt% or less, 25 wt% or less, or 20 wt% or less.

[0084] As described above, the inorganic foaming agent can perform the role of delaying the temperature rise by latent heat as moisture vaporizes at high temperatures and suppressing heat transfer by increasing the distance between cells through expansion, and this function can be optimally performed by including a polymer resin together with the inorganic filler.

[0085] Specifically, the inorganic foaming agent included in the foamed coating part can form a layer and achieve a foaming effect on its own since it is in a gel state, but in order to apply it to a pouch-type case, it is necessary to ensure durability and flexibility above a certain level. Specifically, if the elasticity and flexibility of the foamed coating part are low, there is a problem that the foamed coating part formed as a layer within the pouch-type case can easily break.

[0086] In this regard, there have been attempts to incorporate a moisture-retaining agent, such as glycerin, as a means to improve the flexibility of the foamed coating part. However, this type of moisture-retaining agent, such as glycerin, easily deforms in the battery operating environment—that is, at high temperatures above 50°C or low temperatures below 0°C, rather than at room temperature—and fails to exhibit a moisturizing effect, making it difficult to commercialize in actual batteries.

[0087] To solve these problems, by incorporating the above-mentioned polymer resin into the foamed coating part, a foamed coating part with excellent adhesion and durability can be realized. The above-mentioned polymer resin can improve adhesion to the adhesive substrate through hydrogen bonding with the inorganic filler and foaming agent, and can improve the flexibility and elasticity of the foamed coating part.

[0088] The above polymer resin may be one or more selected from, for example, styrene-butadiene rubber, phenol resin, polyester resin, epoxy resin, polysiloxane resin, polyurethane resin, polyvinyl acetate, carboxymethylcellulose, and nitrile rubber. By including an organic binder of the above type in the foamed coating part, the flexibility of the foamed coating part can be improved and the adhesion to organic materials can be improved. Preferably, the above polymer resin may be one or more selected from the group consisting of styrene-butadiene rubber, epoxy resin, and polyurethane resin.

[0089] In addition, the above polymer resin may preferably be of two or more types. When two or more types of polymer resins are included, the polymer resin may include styrene-butadiene rubber and epoxy resin, and in this case, the content may be independently selected within the aforementioned range, and the sum thereof may be included so as to be applied within the aforementioned range.

[0090] In addition, the above epoxy resin may include epoxy putty. As a result, optimal effects can be expected in securing adhesion to the substrate and realizing a foamed coating part with excellent flexibility and elasticity. Referring to the table in FIG. 4, the foamed coating part (E, F) provided in this invention was manufactured with sodium silicate as an inorganic foaming agent, kaulin as an inorganic filler, and polyurethane as a polymer resin, and experiments were conducted with different weight percentages of the inorganic foaming agent, inorganic filler, and polymer resin. In the table shown in FIG. 4, the foaming rate and foaming strength of Examples 1, 2, and 3 containing 27.5 wt% or more of the inorganic foaming agent, and Comparative Examples 1 and 2 containing less than 27.5 wt% of the inorganic foaming agent are listed.

[0091] The above foaming rate was expressed as a multiple of the volume of the foamed coating part after foaming was completed relative to the volume of the foamed coating part before foaming. Considering that the foaming rate of the foamed coating part must be at least 2.5 times to induce a break (of the positive or negative tab), the foaming strength was indicated as 'O' if the foaming rate exceeded 2.5 times and 'X' if it was less than 2.5 times. In the test in which the results of Figure 4 were obtained, the foamed coating part was fabricated into a sheet form and heated at 150°C for 5 minutes to compare the thickness before and after foaming.

[0092] As shown in Fig. 4, it was confirmed that the foamed coating part must contain at least 27.5 wt% of an inorganic foaming agent for the foaming rate to exceed 2.5 times.

[0093] In addition, through additional tests, it was confirmed that if the foamed coating expands more than 2.5 times, sufficient tension is formed at the positive tab connection or negative tab connection to induce a break in the wire.

[0094] Meanwhile, in the present invention, the inorganic filler and polymer resin included in the foamed coating portions (E, F) are introduced to uniformly disperse the inorganic foaming agent, improve chemical stability, and adhere the inorganic foaming agent to the anode tab connection portion or the cathode tab connection portion.

[0095] For example, when the inorganic foaming agent in the foamed coating part exceeds 90 wt% (the weight percentage of the inorganic filler and polymer resin decreases), there were cases where the adhesion decreased and detached after coating or applying to the anode tab connection part or the cathode tab connection part.

[0096] Therefore, it is preferable that the inorganic foaming agent in the above foamed coating part be included in an amount of 90 wt% or less.

[0097] Meanwhile, in the present invention, the foamed coating part (E) coupled to one anode tab connection part (2b) and the foamed coating part (E) coupled to another anode tab connection part (2b) may be configured to expand to different volumes.

[0098] That is, as illustrated in FIG. 3, the foam coating portion can be expanded to the thickest at the shortest bottom layer anode tab connection portion (2b). The foam coating portion (E1) connected to the shortest anode tab connection portion has the thickest thickness, and the foam coating portion (E5) connected to the longest anode tab connection portion has the thinnest thickness. Therefore, the longer the length of the anode tab connection portion (2b), the thinner the foam coating portions (E1, E2, E3, E4, E4) have.

[0099] Likewise, the foam coating portion (F) coupled to one cathode tab connection portion (4b) and the foam coating portion (F) coupled to another cathode tab connection portion (4b) can expand to different volumes. That is, referring to FIG. 5, the foam coating portion (F1) coupled to the shortest cathode tab connection portion (4b1) has the thickest thickness so that it can expand to the thickest thickness, and the foam coating portion coupled to the longest cathode tab connection portion (4b6) has the thinnest thickness. Therefore, the longer the length of the cathode tab connection portion (4b), the thinner the foam coating portions (F1, F2, F3, F4, F4) have.

[0100] For reference, the electrode assembly (1) illustrated in FIGS. 3 and FIGS. 5 has the lowest positive tab connection and the lowest negative tab connection configured to be the shortest. However, as shown in FIG. 6, if the middle layer has the shortest length (for example, if there are 18 positive tabs, the 9th positive tab connection from the bottom to the top becomes the middle layer, and the structure has the shortest length for the 9th positive tab connection), the size of the first space (2d) increases as it goes upward relative to the middle layer, and the size of the first space (2d) also increases as it goes downward.

[0101] If the electrode assembly (1) has such a configuration, when m positive tab connecting parts are provided, the thickness (T1) of the foamed coating part coupled to the nth positive tab connecting part (2b) can be calculated by the following formula 1.

[0102]

[0103] [Formula 1]

[0104]

[0105]

[0106]

[0107] That is, if the sum of the thickness of the anode (2) + the thickness of the cathode + the thickness of the two separator sheets is 500 μm and 18 anode tab connection parts (2b) are provided, for example, the thickness (T1) of the foamed coating part connected to the 9th anode tab connection part (anode tab connection part corresponding to 'B' in FIG. 6) can be set to 100 μm. And, the thickness (T1) of the foamed coating part connected to the 18th anode tab connection part (anode tab connection part corresponding to 'A' in FIG. 6) can be set to 55 μm.

[0108] Accordingly, when compared to the structure illustrated in FIGS. 3 and FIGS. 5, the structure disclosed in FIGS. 3 and FIGS. 5 has the shortest anode tab connection part of the lowest layer, and the foam coating part has a gradually thinner thickness from the bottom to the top, whereas if the anode tab connection part of the middle layer has the shortest structure, the foam coating part can be configured to have the thickest thickness at the center and a gradually thinner thickness towards the outermost (lowest layer and top layer).

[0109] The secondary battery of the present invention having the above configuration is coupled with a foamed coating portion (E, F) that expands in volume when the temperature rises above a predetermined standard when the positive tab and / or negative tab of the electrode assembly, so that when the internal or external temperature of the secondary battery rises, the disconnection of the positive tab or negative tab is induced, thereby preventing the occurrence of fire caused by a short circuit.

[0110] In the present invention, since the foamed coating part contains an inorganic foaming agent as a main component, compression does not occur after expansion, thereby reducing the possibility of failure of disconnection of the positive or negative tab.

[0111] In other words, organic foaming agents made of organic materials have a high probability of dispersing into the air in the form of gas after foaming, or even if they maintain a solid form, failing to resist external forces and thus failing to provide sufficient pressure to disconnect the positive or negative tab. However, since the foaming coating part of the present invention contains an inorganic foaming agent as a main component, it maintains a solid form and can provide sufficient pressure to disconnect the positive or negative tab (since compression occurs little or does not occur during foaming).

[0112] In the present invention, the inorganic foaming agent may be prepared in a liquid state to contain at least one of lithium silicate, also known as water glass, potassium silicate, sodium silicate, potassium silicate, zirconium silicate, magnesium silicate, titanium silicate, vermiculite, and perlite. Accordingly, it can be easily bonded to an anode tab or a cathode tab by coating or spraying.

[0113] In addition, in the present invention, the foam coating portion is configured such that the amount of expansion varies depending on the length of the connected positive tab connection portion or negative tab connection portion, thereby enabling more efficient disconnection.

[0114] Although the present invention has been described above by limited embodiments and drawings, the present invention is not limited thereto, and various implementations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

[0115]

[0116] [Explanation of the symbol]

[0117] 1 : Electrode assembly

[0118] 2 : Positive electrode

[0119] 3 : Separator

[0120] 4 : Cathode

[0121] E, F: Foamed coating section

Claims

1. A secondary battery in which an electrode assembly comprising a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separators is repeatedly stacked and embedded in a case, The electrode assembly comprises a plurality of positive electrode tabs extending from a plurality of positive electrodes and a plurality of negative electrode tabs extending from a plurality of negative electrodes. The above positive tabs form a positive tab stacking section in which the ends extending from each positive tab are stacked together, and the positive tab connecting section connecting the positive tabs and the positive tab stacking section forms a first space section having a predetermined size between it and an adjacent positive tab connecting section. At least two of the above positive tab connection parts are each connected to a foam coating part, and the foam coating part expands in volume within the first space part when the temperature rises above a predetermined standard. The above foamed coating part is a secondary battery containing an inorganic foaming agent.

2. A secondary battery in which an electrode assembly comprising a plurality of positive electrodes, a plurality of negative electrodes, and a plurality of separators is repeatedly stacked and embedded in a case, The electrode assembly comprises a plurality of positive electrode tabs extending from a plurality of positive electrodes and a plurality of negative electrode tabs extending from a plurality of negative electrodes. The above-mentioned cathode tabs form a cathode tab stacking portion formed by stacking ends extended from each cathode, and the cathode tab connecting portion connecting the cathode and the cathode tab stacking portion forms a second space portion having a predetermined size between it and an adjacent cathode tab connecting portion. At least two of the above-mentioned cathode tab connection parts are each connected to a foam coating part, and the foam coating part expands in volume within the second space part when the temperature rises above a predetermined standard. The above foamed coating part is a secondary battery containing an inorganic foaming agent.

3. In either Paragraph 1 or Paragraph 2, The above-mentioned inorganic foaming agent is, A secondary battery containing at least one of lithium silicate, potassium silicate, sodium silicate, potassium silicate, zirconium silicate, magnesium silicate, titanium silicate, vermiculite, and perlite.

4. In Paragraph 3, A secondary battery in which the above-mentioned inorganic foaming agent is included in the foam coating portion in a range of 27.5 to 90 wt%.

5. In Paragraph 4, The above foamed coating part further comprises a polymer resin, and The above polymer resin is included in the foamed coating portion in a range of 5 to 50 wt% for a secondary battery.

6. In Paragraph 5, The above polymer resin is, A secondary battery containing at least one of polyurethane resin, acrylic resin, cellulose-based resin, and synthetic rubber resin.

7. In Paragraph 5, The above foamed coating part further includes an inorganic filler, and The above-mentioned inorganic filler is included in the foamed coating portion in a range of 5 to 50 wt% for a secondary battery.

8. In Paragraph 7, The above-mentioned weapon filler is, A secondary battery containing at least one of titanium dioxide, alumina, kaolin, zirconia, silica, zinc oxide, and boehmite.

9. In either Paragraph 1 or Paragraph 2, The above-described foamed coating part is a secondary battery in which the final volume expanded by at least 250% compared to the initial volume as the temperature rises above a predetermined standard.

10. In either Paragraph 1 or Paragraph 2, The above foamed coating part is a secondary battery in which volume expansion begins when it reaches 80℃.

11. In Paragraph 1, A secondary battery in which a foamed coating part connected to one positive tab connection and a foamed coating part connected to another positive tab connection expand to different volumes.

12. In Paragraph 11, A secondary battery in which, among the positive tab connection parts to which the above-mentioned foam coating parts are connected, the foam coating part connected to the shortest positive tab connection part has the thickest thickness, and the foam coating part connected to the longest positive tab connection part has the thinnest thickness.

13. In Paragraph 11, A secondary battery having m positive tab connection parts, with foam coating parts attached to all positive tab connection parts, and when the outermost positive tab connection parts have the longest length, the thickness (T1) of the foam coating part attached to the nth positive tab connection part from bottom to top is calculated by the following formula. [formula] 14. In Paragraph 2, A secondary battery in which a foamed coating part coupled to one negative tab connection and a foamed coating part coupled to another negative tab connection expand to different volumes.

15. In Paragraph 14, A secondary battery in which, among the negative tab connection parts to which the foam coating part is attached, the foam coating part attached to the shortest negative tab connection part has the thickest thickness, and the foam coating part attached to the longest negative tab connection part has the thinnest thickness.

16. In Paragraph 14, A secondary battery having m negative tab connections, with foam coatings attached to all negative tab connections, and when the outermost negative tab connections have the longest length, the thickness (T1) of the foam coating attached to the nth negative tab connection from bottom to top is calculated by the following formula. [formula] 17. A secondary battery module comprising a plurality of secondary batteries according to either claim 1 or claim 16.

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