Secondary battery and secondary battery module including the same

Abstract

The present invention relates to a secondary battery, wherein the separator included in the electrode assembly has a seal that individually seals the positive and negative electrodes, and the secondary battery has a double-seal structure including a first seal and a second seal so that a reservoir for containing a fire-extinguishing agent is provided at the end of the negative electrode. This effectively prevents the separator from contracting when exposed to high temperatures, and if a spark occurs inside the battery, the fire can be quickly extinguished by the fire-extinguishing agent, thereby preventing an internal short circuit caused by the separator contraction and the resulting explosion or fire of the secondary battery. Furthermore, the secondary battery includes a flame propagation prevention member on the outer surface of the electrode assembly, which prevents a flame that occurs during thermal runaway of the secondary battery from reaching the inside of the cell and extends the time for the flame to spread, thereby further improving the safety of the secondary battery and a secondary battery module including the same.

Description

[Technical field]

[0001] The present invention relates to a secondary battery and a secondary battery module including the same.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2021-0112116 dated August 25, 2021, and all contents disclosed in the documents of that Korean patent application are incorporated herein by reference. [Background technology]

[0003] The demand for secondary batteries is also increasing rapidly with technological development and increasing demand for mobile devices. Among them, lithium secondary batteries are widely used as energy sources for various electronic products as well as various mobile devices due to their high energy density, high operating voltage, and excellent storage and life characteristics.

[0004] The types of such secondary batteries include lithium ion batteries, lithium polymer batteries, nickel cadmium batteries, nickel metal hydride batteries, nickel zinc batteries, etc. Furthermore, lithium secondary batteries are classified into square batteries, pouch batteries, and cylindrical batteries depending on their shape.

[0005] Recently, secondary batteries are widely used not only in small devices such as portable electronic devices, but also in medium to large devices such as battery packs for hybrid and electric vehicles and power storage devices.

[0006] Such secondary batteries have advantages such as high operating voltage and high energy density, but because they use organic electrolyte, if a lithium secondary battery is overcharged, it can induce overcurrent and overheating, and in severe cases, can cause an explosion or fire.

[0007] In addition, in the case of a battery module in which multiple battery cells are stacked, if any one battery cell explodes or catches fire, the flame may spread to other battery cells that are still functioning normally, causing a chain reaction of explosions of the multiple battery cells, which may damage the device in which the battery module is installed and expose users to the risk of a safety accident.

[0008] FIG. 1 is a schematic diagram showing an example of a structure of a conventional battery module proposed to prevent flame propagation between battery cells.

[0009] The conventional battery module 1 includes a plurality of battery cells 10, a flame propagation prevention member 20 positioned between each battery cell, and a module case 11.

[0010] Even if an explosion or fire occurs in any one of the plurality of battery cells 10, the flame propagation prevention member 20 is located between the battery cells, so that the flame can be prevented from propagating to other battery cells.

[0011] However, in the conventional battery module described above, since a flame propagation prevention member is installed outside each battery cell, it is not possible to prevent the electrode assembly inside the battery cell from burning. In other words, if a fire occurs in the electrode assembly inside the cell, the flame propagation cannot be blocked at the stage inside the battery cell, so the battery cell burns without any hindrance until the electrode assembly and the battery case surrounding it are completely burned. If the battery cell is completely burned, such as burning not only the electrode assembly but also the battery case, the combustion temperature becomes even higher, and the risk of explosion increases.

[0012] In the conventional battery module, a flame propagation prevention member is installed between battery cells, so that the propagation of a flame to other cells can be delayed for a certain period of time. However, since the flame is not blocked from inside the battery cells, the flame propagation time between battery cells is relatively short. In a battery module containing a plurality of stacked battery cells, how much the flame propagation time can be reduced when a so-called thermal runaway phenomenon occurs in which a battery cell ignites is an important factor in evaluating the quality of the battery module. If the flame propagation time is short, it means that there is a high risk of explosion of not only the individual battery cells but also the entire battery module, and the conventional battery module structure has a limit in suppressing such a flame propagation time.

[0013] Meanwhile, a plurality of positive electrodes and a plurality of negative electrodes are alternately stacked in an electrode assembly, and a separator is interposed between the positive electrodes and the negative electrodes. In this case, the negative electrode is formed to have a larger area than the positive electrode, and the separator is manufactured to be larger than the positive electrode and / or the negative electrode in order to prevent a short circuit between the positive electrode and the negative electrode. However, a high-capacity secondary battery may generate a considerable amount of heat during charging and discharging, which may cause the separator to shrink. The shrunken separator may cause contact between the positive electrode and the negative electrode, resulting in an internal short circuit. Such an internal short circuit may cause an explosion and fire of the battery. Therefore, it is necessary to improve the internal short circuit problem of the electrode assembly from the viewpoint of improving the safety of the secondary battery. [Prior art documents] [Patent documents]

[0014] [Patent Document 1] Korean Patent Publication No. 10-2019-0094921 Summary of the Invention [Problem to be solved by the invention]

[0015] Therefore, an object of the present invention is to provide a secondary battery and a secondary battery module including the same, which prevents contraction of a separator included in an electrode assembly when the secondary battery is exposed to high temperatures, thereby suppressing an internal short circuit and the resulting explosion and / or fire of the secondary battery, while blocking or delaying radio waves of a flame generated when a battery cell explodes or ignites from inside the cell, and prevents fine particles from falling off of a flame propagation prevention sheet. [Means for solving the problem]

[0016] To solve the above problems, In one embodiment, the present invention comprises: The battery includes an electrode assembly having a stacked structure including a positive electrode, a negative electrode, and a separator, and a battery case in which the electrode assembly is housed, The separators included in the electrode assembly include a first seal portion in which an end of a separator is joined to an outer periphery of the electrode assembly to seal the positive electrode and the negative electrode separately; and a second seal portion that forms a receiving portion between an end of the negative electrode and the first seal portion by bonding between separators disposed on the upper and lower surfaces of the negative electrode.

[0017] In this case, the storage section can store an extinguishing agent that changes into a gas phase at 100°C to 300°C, and the extinguishing agent may contain one or more of halogenated carbon, halogenated ketone, halogenated alkane, and inert gas.

[0018] The first seal portion and the second seal portion may be joined by adhesion or heat fusion.

[0019] The separation membrane may have an average thickness of 5 μm to 50 μm.

[0020] The secondary battery may also include a flame propagation prevention portion that delays a flame propagation time.

[0021] As an example, the secondary battery may include a flame propagation prevention portion on at least one of the remaining outer surfaces of the electrode assembly excluding the surface on which the tap is formed.

[0022] As another example, the secondary battery may include a plurality of unit cells stacked in an electrode assembly, and may include a flame propagation prevention member interposed between the stacked unit cells.

[0023] Here, the above Included in flame propagation prevention section The flame propagation prevention sheet may be a silicate sheet composed of a silicate containing one or more elements of silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F) and oxygen (O).

[0024] Specifically, the flame propagation prevention sheet may contain one or more of muscovite, phengite, celadonite, paragonite, margarite, phlogopite, biotite, anite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, zinnwaldite, and taeniolite.

[0025] The silicate sheet may contain 1 to 20 parts by weight of a binder per 100 parts by weight of the total silicate, and the binder may include one or more of polyolefins including polyethylene (PE), polypropylene (PP) or poly(ethylene-propylene) copolymers; polyamides including nylon; and heat-resistant silicone.

[0026] The flame propagation prevention sheet may have a predetermined pattern on its surface, in which protrusions, recesses, or protrusions and recesses are repeatedly formed.

[0027] Moreover, in one embodiment, the present invention provides There is provided a secondary battery module including the secondary battery according to the present invention described above and a module case in which the secondary battery is housed. Effect of the Invention

[0028] In the secondary battery according to the present invention, the separator included in the electrode assembly has a sealing portion that seals the positive electrode and the negative electrode separately, and has a double seal structure including a first sealing portion and a second sealing portion so that a storage portion for storing a fire extinguishing agent is provided at the end of the negative electrode. This makes it possible to more effectively suppress contraction of the separator when exposed to high temperatures, and if a spark occurs inside the battery, the fire can be immediately extinguished by the fire extinguishing agent, thereby preventing an internal short circuit caused by contraction of the separator and the resulting explosion or fire of the secondary battery.

[0029] In addition, the secondary battery includes a flame propagation prevention portion on an outer surface of the electrode assembly, so that a flame generated during thermal runaway of the secondary battery can be blocked at an internal cell stage and the time for the flame to transfer can be extended, thereby further improving the safety of the secondary battery and a secondary battery module including the same. [Brief description of the drawings]

[0030] [Figure 1] FIG. 1 is a schematic diagram showing an example of a structure of a conventional battery module for preventing flame propagation between battery cells. [Diagram 2] 1 is a cross-sectional view showing the structure of a secondary battery according to the present invention. [Diagram 3] 1 is a cross-sectional view showing a structure of an electrode assembly according to the present invention. [Figure 4] 1 is a cross-sectional view showing a structure of an electrode assembly according to the present invention. [Diagram 5] FIG. 2 is a schematic diagram showing a flame propagation state of an electrode assembly having a stack type structure. [Figure 6] 1 is a cross-sectional view showing the structure of a secondary battery according to the present invention. [Figure 7] FIG. 2 is a schematic diagram showing a pattern of the flame propagation prevention sheet of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0031] While the present invention may be modified in various ways and have various embodiments, a specific embodiment will be described in detail in the detailed description.

[0032] It should be understood, however, that this is not intended to limit the invention to the particular embodiments, but rather to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0033] In the present invention, the terms "comprise" or "have" and the like are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof described in the specification, but are to be understood as not precluding the presence or additional possibility of one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0034] In addition, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion in between. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion in between. In addition, in the present application, being "located on" may include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0035] The terms "coupled" or "connected" as used herein include not only cases where one member is directly coupled or connected to another member, but also cases where one member is indirectly coupled or connected to another member through a connecting member.

[0036] The present invention will now be described in more detail.

[0037] <Secondary battery> In one embodiment, the present invention comprises: an electrode assembly including a plurality of positive electrodes and a plurality of negative electrodes alternately arranged and a plurality of separators interposed between the positive electrodes and the negative electrodes; a flame propagation prevention part provided on at least one outer surface of the electrode assembly; a battery case in which the electrode assembly and the flame propagation prevention part are housed, The positive and negative electrodes of the electrode assembly each include a sealing part in which the outer peripheries of a separator disposed on an upper surface and a separator disposed on a lower surface are joined to each other to individually seal the positive and negative electrodes, thereby providing a secondary battery.

[0038] FIG. 2 is a schematic diagram showing the structure of a secondary battery 100 according to the present invention.

[0039] Referring to FIG. 2, the secondary battery 100 according to the present invention has a structure in which an electrode assembly 110 is housed in a pouch-shaped battery case 130, an electrolyte is injected into the battery case 130, and the electrode assembly 110 is impregnated with the electrolyte.

[0040] The electrode assembly 110 may have various structures and may be stacked in various ways. The present invention can be applied to a mono-cell type secondary battery in which one full cell (mono-cell) of a positive electrode-separator-negative electrode is accommodated in a battery case. The electrode assembly 110 may have a stack type structure in which a number of unit cells, such as a mono-cell arranged in the order of a positive electrode-separator-negative electrode, or a bi-cell having a positive electrode-separator-negative electrode-separator-positive electrode or a negative electrode-separator-positive electrode-separator-negative electrode shape, are stacked according to the battery capacity. A number of electrode taps T protrude from the electrodes of the electrode assembly 110 and are connected to the electrode lead 140. The electrode lead 140 is a type of terminal exposed to the outside and connected to an external device, and may be made of a conductive material. The electrode lead 140 may include a positive electrode lead and a negative electrode lead. The positive and negative electrode leads may be arranged in opposite directions relative to the length of the secondary battery 100 (a so-called bidirectional cell) or in the same direction relative to each other (a so-called unidirectional cell). A bidirectional secondary battery 100 is shown in FIG.

[0041] The electrode assembly 110 of the present invention may be an electrode assembly 110 having a stacked structure as shown in Fig. 2. Alternatively, although not shown, the electrode assembly 110 may be a jelly-roll type electrode assembly having a structure in which long sheet-like positive and negative electrodes are wound with a separator interposed therebetween, or a stack-folded type electrode assembly having a mixed type of jelly-roll type and stack type, in which full cells or bi-cells are wound with a long continuous separator sheet.

[0042] In addition, the electrode assembly 110 has a structure in which a separator 113 located between the positive electrode 111 and the negative electrode 112 is joined at its outer periphery to an adjacent separator, so that the positive electrode 111 and the negative electrode 112 between them are surrounded and sealed by the separator 113, and sealing portions 114 and / or 115 may be provided at the ends of the joined separator.

[0043] Specifically, the electrode assembly 110 has a plurality of positive electrodes 111 and a plurality of negative electrodes 112 arranged alternately, and a separation membrane 113 is individually inserted between the arranged positive electrodes 111 and negative electrodes 112 and at the outermost part thereof. The thus inserted separation membrane 113 includes a first seal portion 114 whose end is joined to the outer periphery of the electrode assembly 110 and which individually seals the positive electrodes 111 and the negative electrodes 112, and includes a second seal portion 115 between the end of the negative electrode 112 and the first seal portion 114 by joining the separation membranes 113 arranged on the upper and lower surfaces of the negative electrodes 112.

[0044] As a result, the first seal portion 114 is located at the end of the positive electrode 111 sealed by the separation membrane 113 , and the first seal portion 114 and the second seal portion 115 are located at the end of the negative electrode 112 .

[0045] Here, it is preferable that the sealing portions 114 and 115 are formed on the remaining outer surfaces of the electrode assembly 110 except for the side on which the tap T is formed. Since the side on which the tap T of the electrode assembly 110 is formed is a passage through which the electrolyte and gas flow, if this side is sealed, the basic electrical function may be deteriorated.

[0046] Furthermore, in order to suppress shrinkage of separation membrane 113 at high temperatures, seal portion 114 and / or 115 may have a certain area ratio with respect to the total area of ​​positive electrode 111 and / or negative electrode 112. Specifically, first seal portion 114 and / or second seal portion 115 may have an area ratio of 2% or more with respect to the total area of ​​positive electrode 111 and / or negative electrode 112, and more specifically, may be 4% or more, 5% or more, 8% or more, 10% or more, 15% or more, 20% or more, 5 to 20%, 5 to 15%, 5 to 10%, 10 to 20%, 11 to 19%, or 8 to 14%.

[0047] As an example, the first seal portion 114 may have an area ratio of 3% to the total area of ​​the negative electrode 112, and the second seal portion 115 may have an area ratio of 5 to 8% to the total area of ​​the negative electrode 112.

[0048] In the present invention, by satisfying the above-mentioned area ratio of the area of ​​the sealing portion 114 and / or 115 to the total area of ​​the sealed positive electrode 111 and / or negative electrode 112, it is possible to maintain a high energy density and to more firmly fix the separator 113 around the electrodes when exposed to high temperatures, thereby minimizing the shrinkage of the separator 113. That is, a significantly low area ratio of the sealing portion does not realize the effect of suppressing the shrinkage of the separator, and an excessive area ratio of the sealing portion can prevent a decrease in the energy density of the electrode assembly.

[0049] In addition, the separator 113 preferably has a large area so that it covers the surfaces of the positive electrode 111 and the negative electrode 112 and leaves excess portions of the separator 113 around each electrode. In this case, by implementing a joint between the separators along the excess portions of the separator 113, the seal parts 114 and 115 that can seal each electrode around the positive electrode 111 and the negative electrode 112 and fix the separator 113 at the same time can be formed. That is, the seal parts 114 and 115 serve to fix the ends of the separator 113 when the secondary battery 100 is exposed to high temperatures, thereby preventing the separator 113 from shrinking. In particular, the secondary battery 100 according to the present invention includes the second seal part 115 that further seals the negative electrode 112 doubly inside the first seal part 114, thereby further improving the shrinkage resistance of the separator 113 at high temperatures compared to the case where only the first seal part 114 that seals the positive electrode 111 and the negative electrode 112 individually is provided.

[0050] In addition, the separation membrane 113 may be fused by applying heat or by using an adhesive means used in the art when bonding the separation membrane, thereby forming a first seal portion 114 and a second seal portion 115.

[0051] As an example, as shown in FIG. 3, the separation membrane 113 may form seal portions 114 and / or 115 using a means 115 such as an adhesive containing polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, and acrylic copolymer.

[0052] As another example, as shown in FIG. 4, the separator 113 may have the seal portions 114 and / or 115 formed by heat sealing the outer periphery of the separator 113 under high temperature conditions by applying pressure thereto.

[0053] In addition, the average thickness of the separator 113 may be 5 μm to 50 μm, specifically, 10 μm to 40 μm, 20 μm to 30 μm, or 17 μm to 28 μm. By controlling the average thickness of the separator 113 within the above range, the present invention can prevent the total thickness of the electrode assembly 110 from becoming excessively thick, thereby further increasing the energy density.

[0054] Moreover, the electrode assembly 110 has a configuration including a receiving portion 118 between the first sealing portion 114 and the second sealing portion 115. The receiving portion 118 is formed by bonding between the separators 113 disposed on the upper and lower surfaces of the negative electrode 112, and may thus include a certain pouch-shaped space at the end of the negative electrode 112. In this case, the size of the receiving portion 118 is not particularly limited, but when the sealing portion is formed by an adhesive means, the thickness may be the same as the average thickness of the negative electrode.

[0055] In addition, the receiving portion 118 may contain a fire extinguishing agent that can act on a spark generated inside the secondary battery cell to reduce and / or eliminate the spark.

[0056] Here, the extinguishing agent may be any type of extinguishing agent used in normal fire suppression, regardless of whether it is in powder, liquid, or gas form, and various extinguishing agents used in the art may be used. As for the extinguishing principle, smothering, cooling, or a combination of these two principles may all be used.

[0057] Specifically, the extinguishing agent may be a substance having excellent extinguishing performance, which contains as its main component a component whose production and use are not restricted by the Montreal Protocol, which is in a liquid phase at room temperature, and which changes into a gas phase at a specific temperature, for example, 100 to 300°C, specifically, 100 to 200°C.

[0058] Examples of such extinguishing agents include halogenated carbons such as fluorine carbon, fluorine chlorine carbon, fluorine bromine carbon, fluorine iodine carbon, and iodofluorocarbon (FIC-217I1 or FIC-13I1); 2-Iodo-1,1,1,2,3,3,3-heptafluoropropane (HFC-227ea), 1,1,1,2,2-pentafluoroethane (CF 3 CF 3 H, HFC-125), 1,1,1,2,3,3,3-heptafluoropropane (CF 3 CHFCF 3 ), chlorotetrafluoroethane (CHClFCF 3 ), 1-chloro-1,2,2,2-tetrafluoroethane (C 2 HClF 4 ), 2-chloro-1,1,1,2-tetrafluoroethane (CHClFCF 3 Halogenated alkanes such as HCFC-124; Dodecafluoro-2-methylpentan-3-one (FK-5-1-12, CF 3 CF 2 C(O)CF(CF 3 ) 2 ), decafluorocyclohexanone (perfluorocyclohexanone), CF 3 CF 2 C(O)CF(CF 3 ) 2 (-1,1,1,2,4,4,5,5,5-nonafluoro-2-trifluoromethyl-butan-3-one), (CF 3 ) 2 CFC(O)CF(CF 3 ) 2 (-1,1,1,2,4,5,5,5,6,6,6-octafluoro-2,4,-bis(trifluoromethyl)pentan-3-one), CF 3 CF 2 C(O)CF 2 CF 2 CF3 , C.F. 3 C(O)CF(CF 3 ) 2 ,1,1,1,3,3,4,4,5,5,6,6,7,7,8,8,8-Hexadodecafluorooctan-2-one (CF 3 CF 2 CF 2 CF 2 CF 2 CF 2 C(O)CF 3 ), 1,1,1,3,4,4,4-heptafluoro-3-trifluoromethylbutan-2-one (CF 3 C(O)CF(CF 3 ) 2 ), 1,1,1,2,4,4,5,5-octafluoro-2-trifluoromethylpentan-3-one (HCF 2 CF 2 C(O)CF(CF 3 ) 2 ), 1,1,1,2,4,4,5,5,6,6,6-undecafluoro-2-trifluoromethylhexan-3-one (CF 3 CF 2 CF 2 C(O)CF(CF 3 ) 2 ), 1-chloro-, 1,1,3,4,4,4-hexafluoro-3-trifluoromethyl-butan-2-one ((CF 3 ) 2 CFC(O)CF 2 Cl), 1,1,1,2,2,4,4,5,5,6,6,6-dodecafluorohexan-3-one (CF 3 CF 2 C(O)CF 2 CF 2 CF 3 ), 1,1,1,5,5,5-hexafluoropentane-2-4-dione (CF 3 C(O)CH 2 C(O)CF 3 ), 1,1,1,2,5,6,6,6-octafluoro-2,5-bis(trifluoromethyl)hexane-3,4-dione ((CF 3 ) 2 CFC(O)C(O)C(O)CF(CF 3 )2 ), 1,1,1,2,2,3,3,5,5,6,6,7,7,7,-tetradecafluoroheptan-4-one (CF 3 CF 2 CF 2 C(O)CF 2 CF 2 CF 3 ), 1,1,1,3,3,4,4,4-octafluorobutan-2-one (CF 3 C(O)CF 2 CF 3 ), 1,1,2,2,4,5,5,5-octafluoro-1-trifluoromethoxy-4-trifluoromethylpentan-3-one (CF 3 OCF 2 CF 2 C(O)CF(CF 3 ) 2 ), 1,1,1,2,4,4,5,5,6,6,7,7,7,-tridecafluoro-2-trifluoromethylheptan-3-one (CF 3 CF 2 CF 2 CF 2 C(O)CF(CF 3 ) 2 ), halogenated ketones such as 1,1,1,2,2,3,4,5,5,5-decafluoro-3-methoxy-4-(trifluoromethyl)pentane; Nitrogen gas (N 2 ), argon gas (Ar), or the like, either alone or in admixture.

[0059] As an example, the extinguishing agent may be one having the chemical formula CpHqOrXs (wherein p, q, r, and s are integers from 0 to 20, and X is one or more of Br, I, and F), and as an example, Novec 1230 from 3M may be used.

[0060] In addition, the electrode assembly 110 has a flame propagation prevention part 120 disposed on at least one outer surface. In this specification, the flame propagation prevention part 120 means a sheet-like member that prevents a flame caused by an ignition from being transmitted to other secondary battery cells when a ignition occurs in one secondary battery in, for example, a battery module or battery pack in which a plurality of secondary batteries are inserted. In addition, since the flame propagation prevention part 120 is a sheet-like member, it does not include holes like a conventional flame prevention net, but is a sheet of a fabric concept filled with fine particles such as crystalline silicate minerals such as mica, and can more effectively block flames.

[0061] In addition, the flame propagation prevention unit 120 of the present invention can increase the rigidity of the secondary battery 100. For example, when the flame propagation prevention unit 120 is installed on the electrode assembly, it reduces the pressing width of the battery cell during an impact test of the secondary battery 100, as described below, and serves to protect and reinforce the electrode assembly 110 in the battery case 130. Since the flame propagation prevention unit 120 of the present invention is installed in the battery case 130, it has an independent technical significance in that it provides stronger rigidity not only when a plurality of secondary batteries 100 are installed together, but also when a single secondary battery 100 is used as a power source for an electrical device.

[0062] The flame propagation prevention sheet 121 functions to prevent a flame from propagating to other parts of the secondary battery cell or to other adjacent secondary battery cells when a flame occurs in the secondary battery cell due to, for example, an overcurrent or thermal runaway. Therefore, the flame propagation prevention sheet 121 can adopt a material having both heat resistance and heat insulation to block the flame. Among them, the flame propagation prevention sheet 121 included in the flame propagation prevention part 120 of the present invention is preferably a silicate sheet having both heat resistance and heat insulation.

[0063] The silicate sheet referred to in the present invention is made of silicate and performs a function of realizing a flame retardant and / or flame retardant effect in a battery case. In this case, the silicate may be any silicate commonly used in the art, and may contain one or more elements selected from the group consisting of silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F) and oxygen (O).

[0064] Generally, silicates refer to neutral salts in which hydrogen in silicic acid is replaced with other metal atoms, but in the present invention, silicates in which the hydrogen sites are replaced with elements such as aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), etc. can be used to realize flame retardancy and / or flame retardant effects, and layered silicates can be used in particular for flame retardancy.

[0065] For example, the silicate may include one or more of muscovite, phengite, celadonite, paragonite, margarite, phlogopite, biotite, anite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, zinnwaldite, and taeniolite.

[0066] As an example, the flame propagation prevention sheet 121 may include a mica sheet containing mica.

[0067] Mica is one of the rock-forming materials that make up granite, and has excellent electrical insulation properties and exhibits very little change in physical properties when heated. The mica has excellent insulation resistance even at high temperatures of 500 to 1000°C. In addition, mica has excellent flame retardancy and does not produce smoke when burned or heated. Due to these characteristics, by installing a mica sheet containing mica in the battery case of a secondary battery, it is possible to prevent or delay thermal runaway inside the battery cell and even between the battery cells.

[0068] In addition, the flame spread prevention sheet 121 may be manufactured in a sheet shape by mixing scrap mica or crushed mica, which is a main component, with a binder (e.g., heat-resistant silicon) to form a large plate, and then cutting it to an appropriate length to manufacture the sheet shape that matches the size of the electrode assembly. However, the manufacturing method of the mica sheet is not limited thereto, and the mica sheet may be manufactured in various ways according to techniques commonly known in the art.

[0069] Here, "mainly as a component" means that the target component is contained in an amount of 60 parts by weight or more, 70 parts by weight or more, 80 parts by weight or more, 85 parts by weight or more, 90 parts by weight or more, 95 parts by weight or more, 98 parts by weight or more, or 99 parts by weight or more out of a total of 100 parts by weight of the substance.

[0070] As an example, the flame propagation prevention sheet 121 may contain 1 to 20 parts by weight of a binder with respect to 100 parts by weight of the total silicate.

[0071] The binder contained in the sheet may be one having excellent adhesion to silicates. Specifically, the binder may include at least one of polyolefins including polyethylene (PE), polypropylene (PP) or poly(ethylene-propylene) copolymers; polyamides including nylon; and heat-resistant silicone, but is not limited thereto.

[0072] In addition, the size of the flame propagation prevention part 120 is preferably such that it covers almost or completely the surface of the electrode assembly 110 in order to prevent flame propagation and from the viewpoint of protecting the electrode assembly 110. In addition, the thickness of the flame propagation prevention sheet 121 can be appropriately selected in proportion to the thickness of the electrode assembly 110 to be used. For example, when using an electrode assembly 110 having a stacked structure, a sheet having a thickness of about 0.1 to 1 mm can be used, but is not limited thereto. That is, a sheet having a thickness greater than or less than that can be used depending on the electrode or battery specifications.

[0073] The flame propagation prevention unit 120 may be in contact with the electrode assembly 110 to protect the electrode assembly 110, or may be laminated on the electrode assembly with another layer interposed therebetween. As shown in Fig. 2, the flame propagation prevention unit 120 may be laminated on both the upper and lower surfaces of the electrode assembly 110, or on one of the upper and lower surfaces. In some cases, the flame propagation prevention unit 120 may be laminated on both sides of the electrode assembly 110.

[0074] The battery case 130 may be a pouch-type battery case as shown in FIG. 2, but is not limited thereto, and may be a cylindrical can or a square can. The pouch-type battery case is made of an aluminum laminate film in which resin and aluminum are laminated. When the battery (electrode assembly) ignites due to thermal runaway, the heat blocking function of the aluminum laminate film is significantly deteriorated and melts. When the aluminum laminate film burns, toxic gas is generated, and the combustion temperature becomes higher because additional materials (battery case) are burned in addition to the electrode assembly. In addition, since the cylindrical can or square can-shaped battery case is made of a metal can, the problem of heat propagation during thermal runaway is a little more serious than that of the pouch-type battery cell, but from the viewpoint of safety, it is necessary to prevent or delay the heat propagation during thermal runaway. It is preferable that the flame propagation prevention unit 120 completely blocks the propagation of heat or flame during abnormal thermal runaway, but even if this is not possible, it is important to delay the propagation as much as possible. Since a secondary battery module is configured by stacking a plurality of secondary battery cells 100, if the flame propagation is delayed by even a few seconds to a few tens of seconds in each secondary battery cell 100, the flame propagation can be delayed by several minutes or more in the entire secondary battery module. Such flame propagation retardation characteristics are important characteristics related to the prevention of ignition, particularly explosion, or the maximum delay in explosion time.

[0075] FIG. 5 is a schematic diagram showing a flame propagation state in an electrode assembly having a stack type structure.

[0076] As shown in FIG. 5, if the stack layer of the electrode assembly 110 is divided into an upper part (X part) and a lower part (Y part), for example, if a flame occurs in a part of the X part, the flame advances to the upper and lower ends of the electrode assembly 110 without any hindrance. Therefore, even if the flame propagation prevention parts 120 are installed on the upper and lower surfaces of the electrode assembly 110 as shown in FIG. 5, the flame propagation to the outside of the electrode assembly 110 can be blocked, but the flame propagation to the inside of the electrode assembly 110 cannot be prevented. In this case, the electrode assembly 110, which is highly stacked in multiple stages for high capacity, is burned and consumed as a whole due to the ignition of some unit cells. In addition, if the entire highly stacked electrode assembly burns, the combustion range expands and the combustion temperature also rises, making it difficult to suppress the flame propagation.

[0077] FIG. 6 is a schematic diagram showing the structure of a battery cell according to another embodiment of the present invention for solving the above-mentioned problems.

[0078] Referring to FIG. 6, a flame propagation prevention unit 120 is stacked between unit cells (monocells M) located in the middle of an electrode assembly 110. The unit cells have a layer structure of a positive electrode-separator 113-negative electrode-separator 113. That is, a predetermined number of unit cells are stacked in an upper X part with the flame propagation prevention unit 120 in the center, and a predetermined number of unit cells are stacked in a lower Y part. For example, if a flame occurs in the X part due to overheating, the flame may propagate to the upper end of the X part. However, since the flame propagation prevention unit 120 is located between the unit cells of the X part and the Y part, the flame generated in the X part does not propagate to the Y part. Or, even if a flame propagates, the flame first propagates to the X part and then to the Y part. In other words, the flame propagation prevention unit 120 acts as a kind of barrier to block the radio waves of the flame and to sequentially induce ignition even when the flame propagates. As a result, even if the fire progresses to the Y part, the fire progresses sequentially, preventing the entire electrode assembly from catching fire quickly and delaying the overall flame propagation time, thereby improving the safety of the battery cell.

[0079] The flame propagation prevention unit 120 is preferably located at an approximately middle portion of the stacked unit cells, but is not limited thereto, and may be disposed between the unit cells near the top or bottom of the electrode assembly 110 as necessary.

[0080] Regardless of the position, the flame propagation prevention unit 120 can suppress flame propagation to the upper or lower part based on the sheet. The number of flame propagation prevention units to be installed is not limited to one. Depending on the number of unit cells to be stacked, two or more flame propagation prevention units can be installed at appropriate positions of the electrode assembly having a stack structure. However, when a flame propagation prevention unit is installed, the upper or lower unit cells or the upper and lower unit cells cannot perform the charge and discharge function as a battery based on the sheet part. Therefore, it is preferable to install as few flame propagation prevention units as possible in the electrode assembly. In other words, it is preferable to determine the installation position and number of flame propagation prevention units within an optimal range in consideration of the battery capacity and safety.

[0081] Meanwhile, the electrode assembly 110 shown in FIG. 6 is arranged as unit cells (monocells) having a symmetrical structure at the upper and lower parts, and a flame propagation prevention part 120 is arranged in a part of the half cell H1 between the symmetrical structures, thereby minimizing the part of the unit cell that does not contribute to charging and discharging.

[0082] The flame propagation prevention unit 120 of the present embodiment is not only positioned between unit cells, but may be laminated in place of the separator 113, positive electrode, or negative electrode that is a part of another unit cell that is positioned between specific unit cells M and unit cell M. In other words, the flame propagation prevention unit can be installed at an appropriate position by comparatively measuring the battery capacity and safety. Referring to FIG. 6, the flame propagation prevention unit 120 is laminated in place of the separator 113 that is positioned on the top of the negative electrode of the half cell H1.

[0083] 6, the flame propagation prevention effect is maximized when the flame propagation prevention unit 120 is installed on the upper or lower surface of the electrode assembly and inside the stacked electrode assembly 110. However, when the flame propagation prevention unit 120 is installed, the number of unit cells that do not participate in the battery reaction increases, so the number of flame propagation prevention units to be installed should be carefully determined in consideration of this point.

[0084] FIG. 7 is a schematic diagram showing a pattern of a flame propagation prevention sheet 121 of the present invention.

[0085] 7(a) shows the planar shape of the flame-propagation prevention sheet 121, and FIG. 7(b) shows the side shape of the flame-propagation prevention sheet 121. As shown in FIG.

[0086] Referring to FIG. 7, the flame-propagation prevention sheet 121 may have a predetermined pattern formed on its surface. That is, for example, when a mica sheet is used, since mica has a tendency to crack in the length direction, a pattern having a shape in which protrusions, recesses, or protrusions and recesses are repeated on the surface may be formed in order to improve the strength of the mica sheet. FIG. 7(a) shows an example in which a rectangular shape A is repeated or a stripe shape B is formed in the length direction of the sheet as such a pattern shape, but the shape is not limited to such a shape. In addition, as shown in FIG. 7(b), when a pattern is formed in a shape in which protrusions a and recesses b, or protrusions a and recesses b are repeated, the surface area of ​​the flame-propagation prevention sheet 121 is increased, and the heat dissipation area during thermal runaway can be increased. FIG. 7 shows that a pattern is formed only on the upper surface of the flame-propagation prevention sheet 121, but patterns can also be formed on the upper and lower surfaces as necessary.

[0087] The secondary battery according to the present invention has the above-mentioned configuration, and thus it is possible to more effectively suppress the contraction of the separator when exposed to high temperatures, thereby preventing an internal short circuit caused by the contraction of the separator and the resulting explosion or fire of the secondary battery. In addition, the secondary battery can prevent a flame generated during thermal runaway from occurring at the cell internal stage and can extend the time for the flame to transfer, thereby further improving the safety of the secondary battery and a secondary battery module including the same.

[0088] <Secondary battery module> In one embodiment, the present invention provides a method for producing a composition comprising: The secondary battery of the present invention described above, and a module case in which the secondary battery is housed.

[0089] The secondary battery module according to the present invention has excellent safety when exposed to high temperatures due to the configuration including the secondary battery of the present invention, and can be used as a power source for medium- to large-sized devices that require high-temperature safety, long cycle characteristics, high rate characteristics, etc. Specific examples of such medium- to large-sized devices include power tools driven by electric motors, electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), etc., electric two-wheeled vehicles including electric bicycles (E-bikes) and electric scooters, electric golf carts, and power storage systems, and more specifically, hybrid electric vehicles (HEVs) are included, but are not limited thereto.

[0090] The present invention will now be described in more detail with reference to examples and experimental examples. 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.

[0091] <Examples 1 to 3 and Comparative Examples 1 to 3> 40 positive and negative electrodes were prepared, and 120 separators (9.5 cm wide x 34.5 cm long, average thickness: about 20 μm) wider than the positive and negative electrodes were prepared. Next, a pouch-type secondary battery cell measuring 10 cm wide x 35 cm long x 1.6 cm thick was manufactured, in which a stack-type electrode assembly was built in which 40 stack unit cells of separator-negative electrode-separator-positive electrode-separator were stacked. In this case, a separator made of porous polyethylene was used as the separator. In addition, the separators located on the upper and lower surfaces of the negative electrode were primarily heat-sealed at the outer periphery at a temperature of 150°C at the end of the negative electrode to form a second seal, and Novec 1230 (3M Company, Novec 1230) was injected as a fire extinguishing agent into the inside of the separator where the second seal was formed, as shown in Table 1 below, and the outer periphery of the electrode assembly was secondarily heat-sealed to form a first seal.

[0092] Next, the fabricated secondary battery cells were fabricated into stack unit cells by arranging flame propagation prevention parts as shown in Table 1 below: Position (1): outer surfaces of the 1st and 40th stacked electrode assemblies (inside the secondary battery cell, structure in FIG. 7 ); Position (2): Between the outer surfaces of the 1st and 40th stacked electrode assemblies and the 19th and 20th stacked electrode assemblies (inside the secondary battery cell, FIG. 7 structure), or - Position (3): The outer top and bottom surfaces of the battery case (outside the rechargeable battery cells).

[0093] The flame propagation prevention part was made by mixing silicate powder containing 100 parts by weight of muscovite and lithium muscovite (1 wt. / 1 wt.) in total with a binder containing 10 parts by weight of polyethylene and polypropylene (1 mol% / mol%) in total, processing the mixture into a sheet, and cutting the sheet into the same size as the electrode assembly to obtain a mica sheet (average thickness: 0.2 mm). The sheet was used as the flame propagation prevention sheet.

[0094] [Table 1]

[0095] <Experimental Example> In order to evaluate the performance of the secondary battery according to the present invention, the following experiment was carried out.

[0096] a) Evaluation of high temperature shrinkage rate of separation membrane The secondary battery cells of the examples and comparative examples were left in an oven heated to 150°C for 20 seconds. Then, the test specimens were collected and disassembled, and the changes in the width and length of the separator installed in the electrode assembly after leaving it in the oven were measured compared to the width and length (9.5 cm wide x 34.5 cm long) before leaving it in the oven, and the average value of these was calculated as the shrinkage rate of the separator. The results are shown in Table 2 below.

[0097] b) 3P propagation test Three secondary battery cells each of the examples and the comparative examples were prepared, and each secondary battery cell was charged so that its SOC was 100%. The three secondary battery cells were stacked in a 3P propagation test device that was simulated by a cartridge-type module. In this case, the 3P propagation test device was prepared so that aluminum plates having a predetermined thickness were fastened with bolts to the upper and lower parts of the stacked secondary battery cells to pressurize the secondary battery cells, assuming a pressurized structure of the secondary battery cells in the module. In addition, aluminum cooling plates were provided between the upper and lower aluminum plates and the secondary battery cells, and between the stacked secondary battery cells. A heating pad (Hakkosha Co., Ltd., silicon heater, SBH2012) was installed between the lowermost secondary battery cell and the aluminum plate, and the heating pad was made to generate heat to heat the secondary battery cells at a temperature increase rate of 7°C / min, inducing thermal runaway.

[0098] The heating pad started to heat up, and the time it took for the first rechargeable battery cell located at the bottom of the device to ignite was measured, passing through the second rechargeable battery cell and then the third rechargeable battery cell. The results are shown in Table 2 below.

[0099] C) Impact test As in the 3P propagation test, three secondary battery cells each manufactured in the example and comparative example were prepared, stacked, and charged to SOC100%. Next, a secondary battery impact test was conducted on the prepared secondary battery cells according to the UN1642DL impact certification standard. The weight used was 9 kg, and the experiment was conducted by dropping it onto a round bar with a diameter of 16 mm placed on the secondary battery cells. The results are shown in Table 2 below.

[0100] [Table 2]

[0101] As shown in Table 2 above, the secondary battery according to the present invention has excellent safety at high temperatures.

[0102] Specifically, the secondary battery of the embodiment was shown to have a separator shrinkage rate of less than 5% at high temperatures, and it was confirmed that it took more than 190 seconds for all three cells to ignite during a 3P propagation test.Furthermore, the secondary battery of the embodiment was shown to have an average pressing width of less than 8 mm during an impact test, and did not ignite.

[0103] From these results, it can be seen that the secondary battery according to the present invention includes an electrode assembly having a structure in which a separator seals the positive and negative electrodes, and a flame propagation prevention part is provided on the outer surface of the electrode assembly, thereby significantly suppressing flame propagation to adjacent battery cells. In addition, even when used as a single battery cell, the battery cell can be safely protected from external impact by the flame propagation prevention sheet without the need to thicken the battery case itself, thereby significantly improving the safety of the cell as a whole.

[0104] Although the present invention has been described above with reference to preferred embodiments, it will be understood that a person skilled in the art or having ordinary knowledge in the art can make various modifications and variations to the present invention without departing from the spirit and technical scope of the present invention as described in the claims below.

[0105] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the claims. [Explanation of symbols]

[0106] 1 Secondary battery module 10, 100 secondary battery 11 Module case 20 Flame propagation prevention material 110 Electrode assembly 111 Positive electrode 112 Negative electrode 113 Separation membrane 114 First seal part 115 Second seal part 116 Adhesion means 117 Fire extinguishing agents 118 Storage unit 120 Flame propagation prevention part 121 Flame propagation prevention sheet 130 Battery case 140 Electrode Lead T electrode tap X Upper part of electrode assembly Lower part of Y electrode assembly M unit cell or mono cell H1 Half Cell A Square shaped protrusion B Stripe-shaped protrusion a Projection b Concave

Claims

1. An electrode assembly having a stacked structure including a positive electrode, a negative electrode, and a separator located between the positive electrode and the negative electrode and at the outermost portion thereof; a battery case in which the electrode assembly is housed, The separator included in the electrode assembly is a first seal portion, an end of the separator being joined to an outer periphery of the electrode assembly, and sealing the positive electrode and the negative electrode individually; a second seal portion that forms a storage portion between an end portion of the negative electrode and the first seal portion by bonding between the separators arranged on the upper and lower surfaces of the negative electrode, The electrode assembly is a secondary battery having a flame propagation prevention portion on at least one of the remaining outer surfaces excluding the surface on which the tap is formed.

2. 2. The secondary battery according to claim 1, wherein the storage section stores a fire extinguishing agent that changes into a gas phase at a temperature between 100° C. and 300° C.

3. The secondary battery according to claim 2 , wherein the extinguishing agent includes at least one of a halogenated carbon, a halogenated ketone, a halogenated alkane, and an inert gas.

4. The secondary battery according to claim 1 , wherein the first seal portion and the second seal portion are joined by adhesion or thermal fusion.

5. The secondary battery according to claim 1 , wherein the separator has an average thickness of 5 μm to 50 μm.

6. The electrode assembly is configured by stacking a plurality of unit cells, The secondary battery according to claim 1 , further comprising a flame propagation prevention member inserted between the stacked unit cells.

7. 7. The secondary battery according to claim 6, wherein the flame propagation prevention portion includes a flame propagation prevention sheet, and the flame propagation prevention sheet is a silicate sheet made of a silicate containing one or more elements selected from the group consisting of silicon (Si), aluminum (Al), iron (Fe), magnesium (Mg), manganese (Mn), titanium (Ti), sodium (Na), potassium (K), fluorine (F) and oxygen (O).

8. 7. The secondary battery of claim 6, wherein the flame propagation prevention portion includes a flame propagation prevention sheet, and the flame propagation prevention sheet includes one or more of muscovite, phengite, celadonite, paragonite, margarite, phlogopite, biotite, anite, iron mica, siderophyllite, clintonite, lithium muscovite, trilithionite, polylithionite, zinnwaldite, and taeniolite.

9. The silicate sheet contains 1 to 20 parts by weight of a binder per 100 parts by weight of the total silicate, 8. The secondary battery according to claim 7, wherein the binder comprises at least one of polyolefins including polyethylene (PE), polypropylene (PP) or poly(ethylene-propylene) copolymers; polyamides including nylon; and heat-resistant silicone.

10. 7. The secondary battery according to claim 6, wherein the flame propagation prevention portion includes a flame propagation prevention sheet, and the flame propagation prevention sheet has a predetermined pattern on a surface thereof, in which protrusions; recesses; or protrusions and recesses are repeatedly formed.

11. A secondary battery module comprising: the secondary battery according to claim 1; and a module case in which the secondary battery is housed.

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