Secondary battery including heat insulation member

Abstract

According to an embodiment of the present invention, there is provided a secondary battery comprising: an electrode assembly comprising a positive electrode, a negative electrode, and a separator; and an electrolyte, in which the electrode assembly includes two or more unit cells and one or more thermal insulation materials, and in which one or more of the one or more thermal insulation materials are located between the two or more unit cells.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0003157, filed with the Korean Intellectual Property Office on January 8, 2024, the entire disclosure of which is incorporated herein by reference.

[0003] This disclosure relates to secondary batteries including heat insulation components. Background Technology

[0004] With the technological advancements and increasing demands of mobile devices, the demand for secondary batteries as an energy source is rapidly growing. In particular, secondary batteries have attracted considerable attention as an energy source for power-driven devices such as electric bicycles, electric vehicles, and hybrid electric vehicles, as well as for mobile devices such as mobile phones, digital cameras, laptops, and wearable devices.

[0005] Typically, a lithium-ion secondary battery includes a positive electrode, a negative electrode, a separator between the positive and negative electrodes, an electrolyte, and an organic solvent. Because the positive electrode, due to its unstable structure in the charging state, can generate oxygen, and this generation poses a high risk of fire, methods to improve the stability of lithium-ion secondary batteries have been researched and developed.

[0006] One of the important safety components in the safety assessment of lithium-ion batteries is the thermal propagation test. This test confirms whether the lithium-ion battery can withstand 5 minutes or more within a module or cell without igniting. However, with the increasing demand for high capacity and high energy density in recent years, lithium-ion batteries using excessive Ni and Ni-based cathode active materials have become difficult to pass the test, thus raising concerns about their safety.

[0007] On the other hand, conventionally, when lithium secondary batteries are manufactured into modules or packs, a technology has been developed to increase this safety, in which heat insulation components 12 are applied between the secondary batteries 11, or similarly, heat insulation components are applied between modules, such as... Figure 1 As shown in the image.

[0008] However, as the capacity and energy density of individual lithium-ion batteries increase, the explosive power of a single lithium-ion battery also increases, making it difficult to pass thermal transfer tests even in modules and groups. In other words, the safety of lithium-ion batteries remains a concern.

[0009] Therefore, there is a need to develop a technology that can solve these problems from the lithium secondary battery cell. Summary of the Invention

[0010] Technical issues

[0011] The purpose of this disclosure is to provide a secondary battery that can suppress heat transfer even when thermal runaway or fire occurs in the secondary battery cell, thereby reducing the capacity of the secondary battery as the starting point of thermal runaway or fire and improving safety issues caused by heat transfer.

[0012] Technical solution

[0013] According to embodiments of this disclosure, a secondary battery is provided, comprising: an electrode assembly including a positive electrode, a negative electrode, and a separator; and an electrolyte.

[0014] The electrode assembly includes two or more cell units and one or more heat insulation components.

[0015] In this configuration, one or more of the heat insulation components are located between two or more cell units.

[0016] In this document, each of two or more cell units may include one or more electrodes selected from a group consisting of a positive electrode and a negative electrode, as well as a separator. Specifically, each of two or more cell units may be a single cell including a positive or negative electrode and a separator, a dual cell stacked such that electrodes with the same polarity are located at both ends, or a full cell stacked such that electrodes with different polarities are located at both ends.

[0017] Meanwhile, one or more of the insulation components may be located in the middle part based on the stacking direction of the electrode assembly.

[0018] In one specific embodiment, there may be one or more insulation elements, greater than or equal to one and less than or equal to five, and specifically, there may be one or two insulation elements.

[0019] At this point, it is preferred that one or more heat insulation elements are arranged uniformly such that when the number of one or more heat insulation elements is odd, the heat insulation elements can be positioned uniformly between facing cell cells, including the middle portion, based on the stacking direction of the electrode assemblies, and when the number of one or more heat insulation elements is even, the heat insulation elements can be positioned uniformly between facing cell cells.

[0020] Furthermore, the area of ​​each of the one or more thermal insulation elements can be 100% to 110% of the area of ​​the negative electrode. Specifically, the one or more thermal insulation elements can be positioned to completely cover the facing electrode, and more specifically, they can be positioned to cover a portion of the tab protruding from the facing electrode.

[0021] In addition, the thickness of each of the one or more insulation elements can be from 0.1 mm to 5 mm, specifically from 0.2 mm to 2 mm.

[0022] Each of the one or more insulations may include porous Si foam, silica aerogel, or a non-combustible resin containing glass fibers, and specifically, silica aerogel. Attached Figure Description

[0023] Figure 1 This is a schematic cross-sectional view of a conventional battery module.

[0024] Figure 2 This is a schematic cross-sectional view of a secondary battery according to an embodiment of the present disclosure.

[0025] Figure 3 This is a schematic cross-sectional view of a secondary battery according to another embodiment of the present disclosure.

[0026] Figure 4 This is a partially exploded schematic diagram of an electrode assembly used to show the location of a heat insulation member according to an embodiment of the present disclosure.

[0027] Figure 5 This is a partial top view of an electrode assembly according to an embodiment of the present disclosure. Detailed Implementation

[0028] In the following description, various embodiments of the present disclosure will be detailed with reference to the accompanying drawings, to the extent that those skilled in the art can readily practice the present disclosure. The present disclosure may be implemented in various different forms and is not limited to the embodiments described herein.

[0029] For the sake of clarity in describing this disclosure, descriptions of parts that are not related to this disclosure will be omitted, and throughout the specification, the same or similar parts will be indicated by the same reference numerals.

[0030] Because the dimensions and thicknesses of each component are depicted arbitrarily for ease of description, this disclosure is not necessarily limited to the dimensions and thicknesses shown. The figures depict thicknesses at an enlarged scale to clearly show different layers and regions. Furthermore, the figures exaggerate the thickness of a particular layer or region for ease of description.

[0031] Throughout this description, unless otherwise defined, when a part “includes” a component, it does not indicate that the part excludes other components, but rather that the part may further include other components.

[0032] Throughout this text, the term "in plan view" refers to an object viewed from above, and the term "in cross-section view" refers to a vertical cross-section of an object viewed from the side.

[0033] Throughout the description herein, terms such as “about,” “approximately,” and “substantially” are used to describe a range or approximation of numerical values ​​or degrees that take into account inherent manufacturing and material tolerances, and are intended to prevent unfair use of this disclosure by infringers. This disclosure describes precise or absolute numerical values ​​to aid in understanding this disclosure.

[0034] As used in this article, “area,” “length,” “thickness,” and “width” are based on those defined in this article.

[0035] According to embodiments of this disclosure, a secondary battery is provided, comprising: an electrode assembly including a positive electrode, a negative electrode, and a separator; and an electrolyte.

[0036] The electrode assembly includes two or more cell units and one or more heat insulation components.

[0037] In this configuration, one or more of the heat insulation components are located between two or more cell units.

[0038] Figure 2 A cross-sectional view of a secondary battery 100 according to an embodiment of the present disclosure is schematically shown, and Figure 2 A cross-sectional view of a secondary battery 200 according to another embodiment is shown schematically.

[0039] Reference Figure 2 The secondary battery 100 includes an electrode assembly and an electrolyte (not shown). The electrode assembly includes two cell units 110 and 120 and a heat insulation element 130, wherein the heat insulation element 130 is located between the cell units 110 and 120.

[0040] exist Figure 2 The image shows an electrode assembly comprising two cell units 110 and 120 and a heat insulation element 130, but this is not limited to this, and the electrode assembly may have a structure comprising two or more cell units and one or more heat insulation elements. As another example, see [reference]. Figure 3 The secondary battery 200 may have a structure including an electrode assembly and an electrolyte (not shown), the electrode assembly including three cell units 210, 220 and 230 and two heat insulation elements 231 and 232, or the secondary battery may include more structures.

[0041] However, for ease of explanation, in Figure 2 The diagram shows a configuration including a thermal insulation element, and... Figure 3The diagram shows a configuration that includes two insulation elements, and an explanation will be given with reference to this.

[0042] Meanwhile, each of these cell units may have a structure including one or more electrodes selected from a group consisting of a positive electrode and a negative electrode, as well as separators.

[0043] Specifically, each of the two or more cell units can be a single cell including a positive or negative electrode and a separator, a bi-cell stacked such that electrodes with the same polarity are located at both ends, or a full cell stacked such that electrodes with different polarities are located at both ends.

[0044] At this point, there is no limit to the number of electrodes and separators stacked in a single cell.

[0045] Refer again Figure 2 Each of the cell units 110 and 120 may include positive electrodes 111 and 121, negative electrodes 112 and 122, and separators 113 and 123, and may be stacked as a dual cell with negative electrodes 112 and 122 at both ends.

[0046] Of course, the accompanying drawings show a cell 110 or 120 positioned on both sides of the reference heat insulation element 130, but this is a division for ease of explanation, and the structure can have two or more cell units stacked on one side of the reference heat insulation element 130. In other words, it can have a structure in which one or more cell units selected from a group consisting of single cells, dual cells, and full cells are stacked on one side of the reference heat insulation element 130.

[0047] Additionally, it may include one or more insulation components as another part, and more specifically, it may include one or more but less than or equal to five insulation components.

[0048] Including more than five heat insulation components outside the above range may increase the heat insulation effect, but the energy density may decrease based on the total volume of the secondary battery, and the cost and total volume may increase, which is not preferred.

[0049] In view of the above issues, more specifically, a secondary battery may include one or two heat insulation components.

[0050] Therefore, this disclosure focuses on describing components including one or two thermal insulation elements. Figure 2 and Figure 3 But they are not limited to this, and Figure 2 and Figure 3 This is representative of cases involving an odd or even number of insulation components.

[0051] Reference Figure 2 The secondary battery 100 includes a heat insulation element 130, i.e., an odd number of heat insulation elements 130.

[0052] At this point, the thermal insulation element 130 is located in the middle portion based on the stacking direction of the electrode assemblies. Here, the middle portion means that, based on the stacking direction of the electrode assemblies, the number of electrodes differs by one or two compared to the same number of electrodes and separators located on both sides of the thermal insulation element 130.

[0053] When the thermal insulation element 130 is located in the middle section in this manner, the capacity of the secondary battery participating in the reaction during thermal runaway or fire can be reduced by half, which is more effective in suppressing heat transfer.

[0054] Meanwhile, when it includes three or more and an odd number of heat insulation elements, they can be positioned to be evenly arranged between the cell units facing each other, including the middle portion.

[0055] Reference Figure 3 Describe a uniform arrangement. Figure 3 A schematic diagram showing two insulation components is provided.

[0056] Reference Figure 3 The secondary battery 200 includes two heat insulation elements 231 and 232, i.e., an even number of heat insulation elements, and each of the two heat insulation elements 231 and 232 is located between the cell cells 210, 220 and 230.

[0057] At this point, heat insulation elements 231 and 232 are positioned uniformly between the facing cell units 210, 220, and 230, respectively. That is, each of the heat insulation elements 231 and 232 can be formed with the same spacing b between them. Furthermore, the secondary battery, based on the stacking direction of the electrode assemblies, can be equally divided into three parts (a=b=c), with heat insulation elements 231 and 232 included between these three parts.

[0058] In other words, if thermal runaway or fire occurs in a secondary battery, it is preferable that the capacity of the insulation component be minimized to prevent heat transfer, and therefore it is preferable that the insulation component is located in an equally divided portion and has a capacity of 1 / n.

[0059] Therefore, when an odd number of insulation elements are included, it is preferable that at least one insulation element is located in the middle section.

[0060] Furthermore, it is preferable that the thermal insulation component can function even if thermal runaway or fire occurs anywhere in the component. Typically, thermal runaway or fire in a secondary battery is caused by short circuits between the positive and negative electrodes, oxygen generated due to side reactions between the positive and negative electrodes, lithium dendrite formation at the negative electrode, etc., and therefore it is preferable that the thermal insulation component has an area that can prevent these.

[0061] In this case, since the negative electrode is usually made to be much larger than the positive electrode, it is preferable that the area of ​​the insulation element is 100% to 120% of the area of ​​the negative electrode, more specifically 100% to 110% of the area of ​​the negative electrode.

[0062] To explain this in more detail, Figure 4 A partial exploded perspective view of the secondary battery 100 is shown, and Figure 5 A three-dimensional top view of a portion of the secondary battery 100 is shown.

[0063] Reference Figure 4 and Figure 5 The area Si of the heat insulation element 130 can be equal to or greater than the area Sa of the negative electrode 112 facing the separator 113, and can be positioned to completely cover the electrode. That is, if the heat insulation element has the same area as the negative electrode 112 (Si=Sa), the heat insulation element can be positioned to completely cover the portion of the negative electrode 112 except for the contact piece 112a, and if the heat insulation element has a larger area, the heat insulation element can be positioned to cover the entire negative electrode 112 and a portion of the contact piece 112a of the negative electrode 112.

[0064] If the area of ​​the insulation element is outside the above range and smaller than that of the negative electrode, it cannot effectively prevent problems such as short circuits at the negative electrode end, and heat transfer may occur through the end portion. If the insulation element is too wide, there are problems such as increased overall volume and increased production costs; therefore, it is preferable to meet the above range.

[0065] In addition, refer to again Figure 2 The thickness t of the heat insulation element 130 can be from 0.1 mm to 5 mm, specifically from 0.1 mm to 2 mm, and more specifically from 0.1 mm to 1 mm.

[0066] If the insulation is too thick and falls outside the above range, it may increase the overall volume of the secondary battery, and if the insulation is too thin, the insulation effect intended by this disclosure cannot be effectively achieved, which is not preferred.

[0067] Each of these insulation components may comprise porous Si foam, silica aerogel, or a non-combustible resin containing glass fibers. Specifically, the insulation component may comprise silica aerogel, and more specifically, may be composed of silica aerogel.

[0068] In this case, the porous Si foam may have a porosity of 50% to 95% by volume, specifically 60% to 90% by volume. In addition, the average diameter of the pores may be about 100 nm to 100 μm, specifically 500 nm to 10 μm.

[0069] The porosity of the porous Si foam can be measured according to ASTM D4641 using an AUTOSORB iQ series (manufactured by Quantachrome), and the average diameter of the pores is measured by magnifying the sample surface 2500 times using a scanning electron microscope (FE-SEM) (Hitachi S-4800 scanning electron microscope), and then the major axis length of the surface pores confirmed in a randomly sampled range (width of 10 um or more and length of 15 um or more) in the measurement image is measured as the pore size. The number of measurements is at least 10 times or more, and the average value of the pore sizes obtained after the measurement is calculated.

[0070] This porous Si foam can be produced by foaming silicon (Si), and there is no limitation as long as it is produced by a conventionally known method.

[0071] Silica aerogel is a highly porous solid material and has an irregular network structure. Here, the porosity of the silica aerogel can be 90% to 99.9% by volume, specifically 95% to 99.9% by volume, and more specifically 97% to 99% by volume.

[0072] In addition, the average diameter of these pores can be 1 nm to 100 nm, specifically 5 nm to 50 nm, and more specifically 5 nm to 10 nm.

[0073] At this time, the porosity and average pore diameter of the silica aerogel can be analyzed using a Micrometrics ASAP 2010 device based on the nitrogen adsorption / desorption amount according to the partial pressure (0.11 < p / po < 1).

[0074] The method for producing silica aerogel may include a method of drying and shaping under supercritical conditions using the sol-gel method, and there is no limitation as long as it is a production method known in the art.

[0075] The non-combustible resin containing glass fiber is in the form of coating the non-combustible resin on a glass fiber reinforced material, wherein the non-combustible resin and glass fiber may be included in a weight ratio of 30:70 to 80:20, and specifically, may be included in a weight ratio of 40:60 to 70:30.

[0076] In this document, the non-flammable resin may be at least one of the following: polyester, polyamide, polyethersulfone, polyetherimide, polyimide, polyamideimide, polyamidesiloxane, polyurethane, polystyrene, polycarbonate and polymethyl methacrylate.

[0077] The thermal conductivity of this type of insulation can be, for example, 0.02. Up to 0.5 Specifically, it is 0.03 Up to 0.1 And more specifically, 0.04 Up to 0.07 .

[0078] If the thermal conductivity is greater than the above range, sufficient insulation effect cannot be obtained.

[0079] At this point, the thermal conductivity is evaluated according to the ISO 2207-2 standard of the TPS hot plate method. In this case, the measurement model can be TPS 3500.

[0080] Meanwhile, as other components of the secondary battery, the positive electrode can have a structure including a positive electrode current collector and a layer of positive electrode active material formed on one or both sides of the positive electrode current collector.

[0081] In this paper, there are no particular restrictions on the positive electrode current collector, as long as it is conductive and will not cause any chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, sintered carbon, or aluminum or stainless steel whose surface has been treated with one of carbon, nickel, titanium, silver, etc. can be used as the current collector.

[0082] The positive electrode current collector can have a thickness from 3 μm to 500 μm and can have fine protrusions and depressions formed on its surface to enhance adhesion to the positive electrode active material layer. For example, the positive electrode current collector can be used in various forms, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven structures.

[0083] The positive electrode active material layer may contain a positive electrode active material, and optionally include conductive materials, binders and other additives.

[0084] The positive electrode active material is not limited, as long as it is a compound capable of reversibly inserting and deintercalating lithium, wherein the positive electrode active material may specifically include a lithium metal oxide comprising lithium and at least one metal such as cobalt, manganese, nickel or aluminum. More specifically, the positive electrode active material may include a nickel-based lithium transition metal oxide represented by the following chemical formula 1.

[0085] [Chemical Formula 1]

[0086] Li 1+x Nia Co b Mn c M 1-(a+b+c) O2

[0087] Among them,

[0088] M is at least one selected from the group consisting of: Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and

[0089] 0 ≤ x ≤ 0.5, 0.6 ≤ a < 1, 0 < b < 0.4, 0 < c < 0.4.

[0090] In addition, the positive electrode active material is a lithium metal oxide, which may include lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., Li 1+x’ Ni 1-Y Mn Y O2 (where -0.5 ≤ x' ≤ 0.5, 0 < Y < 1), Li 1+x” Mn 2-Z Ni Z O4 (where -0.5 ≤ x'' ≤ 0.5, 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., Li 1+x’’’ Ni 1-Y1 Co Y1 O2 (where -0.5 ≤ x''' ≤ 0.5, 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., Li 1+x’’’’ Co 1-Y2 Mn Y2 O2 (where -0.5 ≤ x'''' ≤ 0.5, 0 < Y2 < 1), Li 1+x’’’’’ Mn 2-Z1 Co Z1 O4 (where -0.5 ≤ x''''' ≤ 0.5, 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li 1+a1 (Ni p Co q Mn r )O2 (where -0.5 ≤ a1 ≤ 0.5, 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li 1+a2 (Ni p1 Co q1 Mn r1 )O4 (where -0.5 ≤ a2 ≤ 0.5, 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li1+a3 (Ni p2 Co q2 Mn r2 M s2 )O2 (where M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and a3, p2, q2, r2, and s2 are atomic fractions of each independent element, where -0.5 ≤ a3 ≤ 0.5, 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, and p2 + q2 + r2 + s2 = 1), etc.), lithium iron phosphate (e.g., Li 1+a4 Fe 1-p3 M p3 (PO 4-b4 )X b4 (where M is at least one selected from Al, Mg, and Ti, X is at least one selected from F, S, and N, and -0.5 ≤ a4 ≤ 0.5, 0 ≤ p3 ≤ 0.5, 0 ≤ b4 ≤ 0.1), and may include any one of them or a mixture of two or more of them.

[0091] Based on the total weight of the positive electrode active material layer, the positive electrode active material may be included in an amount of 60% to 98% by weight, preferably 80% to 98% by weight, and more preferably 90% to 98% by weight.

[0092] The conductive material is a component for further improving the conductivity of the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity and does not cause any chemical changes in the battery, and for example, the following can be used: carbon powder, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal cracking carbon black; graphite powder, such as natural graphite, artificial graphite, or graphite with a well-formed crystal structure; conductive fibers, such as carbon fibers or metal fibers; carbon fluoride powder; conductive powders, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive materials such as polyphenylene derivatives.

[0093] Based on the total weight of the positive electrode active material layer, the conductive material may be included in an amount of 0.1% to 20% by weight, specifically 0.5% to 10% by weight, and more specifically 0.5% to 5% by weight.

[0094] Binders are components that facilitate the bonding between conductive materials, positive electrode active materials, and positive electrode current collectors. Examples of binders may include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-dihydrogen monomer, sulfonated ethylene-propylene-dihydrogen monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0095] Typically, based on the total weight of the positive electrode active material layer, the binder may be included in an amount of 0.5% to 20% by weight, specifically 0.5% to 10% by weight, and more specifically 0.5% to 5% by weight.

[0096] In addition, other additives may include, for example, fillers as components used to suppress expansion. There are no particular limitations on fillers, as long as they can suppress electrode expansion without causing any chemical changes in the battery, and examples may include: olefinic polymers, such as polyethylene and polypropylene; and fibrous materials, such as glass fiber and carbon fiber.

[0097] The negative electrode may have a structure including a negative electrode current collector and a negative electrode active material layer containing negative electrode active material formed on one or both sides of the negative electrode current collector, and the negative electrode active material layer may contain electrode materials such as conductive materials and binders as described in the positive electrode, in addition to the negative electrode active material.

[0098] There are no particular restrictions on the negative electrode current collector, as long as it has high conductivity and does not cause any chemical changes in the battery. Examples of negative electrode current collectors can include: copper, stainless steel, aluminum, nickel, titanium, sintered carbon; copper or stainless steel with surfaces treated with carbon, nickel, titanium, silver, etc.; aluminum-cadmium alloys; and so on.

[0099] Negative electrode current collectors can typically have a thickness ranging from 3 μm to 500 μm. Similar to positive electrode current collectors, negative electrode current collectors can have fine protrusions and depressions formed on their surface to enhance the adhesion to the negative electrode active material. For example, negative electrode current collectors can be used in various forms, such as membranes, sheets, foils, meshes, porous bodies, foams, and nonwoven structures.

[0100] The negative electrode active material layer may include at least one of the following: lithium metal, carbon material capable of reversibly inserting / deintercalating lithium ions, metal or alloy of these metals with lithium, metal composite oxide, material capable of doping and dedoping lithium, and transition metal oxide.

[0101] As a carbon material capable of reversibly inserting / deintercalating lithium ions, any carbon material can be used without particular limitation, as long as it is a carbon-based anode active material commonly used in lithium-ion secondary batteries. Representative examples include crystalline carbon, amorphous carbon, or both. Examples of crystalline carbon include graphite, such as irregular, planar, flake-like, spherical, or fibrous natural or artificial graphite. Examples of amorphous carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbides, and calcined coke.

[0102] As a metal or an alloy of these metals with lithium, a metal or an alloy of these metals with lithium selected from the group consisting of Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn can be used.

[0103] As a metal composite oxide, at least one of the following can be used: PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3 (where 0≤x≤1), Li x WO2 (where 0 ≤ x ≤ 1) and Sn x Me 1-x Me' y O z (Where, Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group I, Group II and Group III elements of the periodic table, halogens; 0≤x≤1; 1≤y≤3; 1≤z≤8).

[0104] Materials capable of doping and dedoping lithium can include Si and SiO. x(0 < x ≤ 2), Si-Y alloy (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from the group consisting of alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), and the like, and at least one of these can be mixed with and used with SnO2. The element Y can be selected from the group consisting of: Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof.

[0105] The transition metal oxide can include a lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, and the like.

[0106] Based on the total weight of the negative electrode active material layer, the negative electrode active material can be included in an amount of 60% to 99% by weight, preferably 80% to 99% by weight, and more preferably 90% to 98% by weight.

[0107] When using the metal itself without forming a negative electrode mixture layer on the negative electrode, it can be manufactured by physically bonding, roll-pressing, or depositing the metal on the metal thin film itself or the negative electrode current collector. As the deposition method, an electro-deposition method or a chemical vapor deposition method of the metal can be used.

[0108] For example, the metal bonded / roll-pressed / deposited on the metal thin film itself or the negative electrode current collector can include one type of metal selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two types thereof.

[0109] The separator can be used without particular limitation as long as it is generally used as a separator in a lithium secondary battery, and those having excellent electrolyte liquid moisture accommodation ability and low resistance to ion migration of the electrolyte liquid are particularly preferred.

[0110] For example, porous polymer membranes comprising polyolefin-based polymers such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or laminated structures of two or more of these layers, can be used as separators. Alternatively, typical porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers, polyethylene terephthalate fibers, etc., can also be used as separators.

[0111] Alternatively, it can be an SRS (Safety Reinforced Separator) having a structure in which a coating comprising a binder and inorganic particles is formed on one or both sides of a polymer substrate as described above.

[0112] The electrolyte can be a lithium non-aqueous electrolyte, and the lithium non-aqueous electrolyte can contain lithium salts and non-aqueous organic solvents.

[0113] In this case, lithium salts are used as the medium for ion transfer within the lithium secondary battery. For example, the lithium salt may contain Li. + It is a cation, and may contain at least one of the following as an anion: F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - B 10 Cl 10 - AlCl4 - AlO2 - PF6 - CF3SO3 - CH3CO2 - CF3CO2 - AsF6 - SbF6 - CH3SO3 - (CF3CF2SO2)2N - (CF3SO2)2N - (FSO2)2N - BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF- (CF3)6P - C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - (CF3SO2)2CH - CF3(CF2)7SO3 - and SCN - .

[0114] Specifically, lithium salts may include a single material or a mixture of two or more materials selected from the group consisting of: LiCl, LiBr, LiI, LiBF4, LiClO4, LiB 10 Cl 10 LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2) and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2), but for the sake of excellent stability, Li(N(SO2CF3)2 is preferred.

[0115] In addition to these, lithium salts commonly used in the electrolytes of lithium secondary batteries can be used without particular restrictions.

[0116] The concentration of lithium salt can be appropriately varied within the generally available range; however, to achieve the best effect in forming a film to prevent corrosion of the electrode surface, lithium salt can be included in the electrolyte at a concentration of 0.5 M to 3 M, specifically 1 M to 2.5 M, and more specifically 1 M to 2 M. When the concentration of lithium salt meets the above range, the effect of improving the cycle characteristics of lithium secondary batteries during high-temperature storage is sufficient, and the viscosity of the electrolyte is suitable to improve electrolyte impregnation.

[0117] Non-aqueous organic solvents are not limited, as long as they can minimize decomposition caused by oxidation reactions, etc., during the charging / discharging process of lithium secondary batteries, and can exhibit the desired properties together with additives. For example, carbonate-based organic solvents, ether-based organic solvents, ester-based organic solvents, etc., can be used alone or in mixtures of two or more thereof, and specifically, carbonate-based organic solvents can be used.

[0118] The carbonate-based organic solvent in the organic solvent can include at least one selected from the group consisting of cyclic carbonate-based organic solvents and linear carbonate-based organic solvents. Specifically, the cyclic carbonate-based organic solvent can include at least one selected from the group consisting of ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, vinylene carbonate, ethylene ethylene carbonate, and fluoroethylene carbonate (FEC). Specifically, it can include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively low melting point compared to ethylene carbonate.

[0119] Furthermore, the linear carbonate-based organic solvent is a solvent having low viscosity and low dielectric constant, and may include at least one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methyl ethyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate, and more specifically, may include dimethyl carbonate.

[0120] Ether-based organic solvents may include, but are not limited to, any one of the group consisting of ethylene glycol dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether, or a mixture of two or more thereof.

[0121] Ester-based organic solvents may include at least one selected from the group consisting of linear ester-based organic solvents and cyclic ester-based organic solvents.

[0122] Specific examples of linear ester-based organic solvents may include, but are not limited to, any one of the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate, or mixtures of two or more thereof.

[0123] Specific examples of cyclic ester-based organic solvents may include, but are not limited to, any one of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone, or mixtures of two or more thereof.

[0124] In ester-based solvents, cyclic carbonate compounds are preferred because they readily dissociate lithium salts in the electrolyte due to their high dielectric constant, acting as highly viscous organic solvents. When cyclic carbonate compounds are mixed with low-viscosity, low-dielectric-constant linear carbonate compounds, such as dimethyl carbonate and diethyl carbonate, in appropriate ratios, electrolytes with high conductivity can be prepared, which is even more preferable.

[0125] In addition, lithium non-aqueous electrolytes may also contain functional additives to prevent the negative electrode from decomposing and collapsing in high-power environments, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and battery swelling suppression during high-temperature storage.

[0126] Specifically, as a representative example, functional additives may include at least one functional additive selected from the group consisting of: sulfonyl lactone compounds, sulfite compounds, sulfone compounds, sulfate compounds, halogenated carbonate compounds, nitrile compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and lithium salt compounds.

[0127] The sulfonyl group compound may include at least one compound selected from the group consisting of: 1,3-propanesulfonyl (PS), 1,4-butanesulfonyl, ethanesulfonyl, 1,3-propenesulfonyl (PRS), 1,4-butenesulfonyl, and 1-methyl-1,3-propenesulfonyl, and may be included in an amount of 0.3% to 5% by weight, and specifically 1% to 5% by weight, based on the total weight of the electrolyte. Where the amount of the sulfonyl group compound in the electrolyte is greater than 5% by weight, an excessively thick layer may form on the surface of the electrode, resulting in increased resistance and decreased output. Furthermore, the increased resistance due to excessive additives may degrade output characteristics.

[0128] The sulfite-based compound may include at least one compound selected from the group consisting of: vinyl sulfite, methyl vinyl sulfite, ethyl vinyl sulfite, 4,5-dimethyl vinyl sulfite, 4,5-diethyl vinyl sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, and 1,3-butylene sulfite, and may be included in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0129] The sulfone-based compound may include at least one compound selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone, and may be included in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0130] The sulfate ester-based compound may include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyltrimethylene sulfate (MTMS), and may be included in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0131] Furthermore, the halocarbonate-based compound may include fluoroethylene carbonate (FEC) and may be included in an amount of 5% by weight or less based on the total weight of the electrolyte. If the amount of the halocarbonate-based compound in the electrolyte exceeds 5% by weight, the battery swelling performance may be reduced.

[0132] In addition, nitrile compounds may include at least one compound selected from the following: succinate, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valerate, octanoic acid, heptanoic acid, cyclopentaneformitrile, cyclohexaneformitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0133] Cyclic carbonate-based compounds may include vinylene carbonate (VC) or vinylene carbonate, and may be included in an amount of 3% by weight or less based on the total weight of the electrolyte. If the content of cyclic carbonate-based compounds in the electrolyte is greater than 3% by weight, the battery swelling suppression performance may be reduced.

[0134] The phosphate ester-based compound may include at least one compound selected from the group consisting of lithium difluoro(bis(oxalato)phosphate), lithium difluorophosphate, tetramethyltrimethylsilyl phosphate, trimethylsilyl phosphite, tris(2,2,2-trifluoroethyl) phosphate and tris(trifluoroethyl) phosphite, and may be included in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0135] The borate ester compound may include lithium difluorooxalate borate and may be included in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0136] Lithium salt-based compounds are compounds that are different from lithium salts contained in lithium non-aqueous electrolytes. Lithium salt-based compounds may include at least one compound selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bis(oxalatoborate) (LiB(C2O4)2), and LiBF4), and may be included in an amount of 3% by weight or less based on the total weight of the electrolyte.

[0137] Two or more functional additives may be mixed and included in an amount of 20% by weight or less, specifically from 0.1% to 10% by weight, based on the total weight of the lithium non-aqueous electrolyte. If the content of the functional additives is greater than 20% by weight, there is a possibility that excessive side reactions may occur in the lithium non-aqueous electrolyte during battery charging and discharging. In particular, they may not decompose sufficiently at high temperatures and may exist as unreacted materials or in a precipitated state in the lithium non-aqueous electrolyte at room temperature. Therefore, side reactions that reduce the lifespan or resistivity characteristics of the lithium metal battery may occur.

[0138] <Example 1>

[0139] LiNi will be used as the positive electrode active material 0.8 Co 0.1 Mn 0.1 O2, carbon black as a conductive material, and PVdF as a binder are mixed in NMP at a weight ratio of 94:3:3 to prepare a slurry. The slurry is then coated on both sides of a 20 μm thick Al current collector to a thickness of 70 μm and dried. The slurry is then rolled to a total positive electrode thickness of 120 μm to manufacture the positive electrode.

[0140] A slurry is prepared by mixing natural graphite as the negative electrode active material, carbon black as the conductive material, styrene-butadiene rubber (SBR) as the binder, and carboxymethyl cellulose (CMC) as the thickener in water at a weight ratio of 95:1:3:1. The slurry is then coated on both sides of a 10 μm thick Cu current collector to a thickness of 90 μm and dried. Finally, it is rolled to a total negative electrode thickness of 130 μm to manufacture the negative electrode.

[0141] In addition, an SRS separator was prepared (a coating of Al2O3 and PVdF mixed in a weight ratio of 80:20 to a thickness of 5 μm on each side was formed on both sides of a 15 μm thick polypropylene substrate) as a separator.

[0142] Cell cells are fabricated by stacking and laminating positive, negative, and separator components to create a separator / negative / separator / positive cell. After stacking 15 such cell cells, cell cells made of separator / negative / separator components are further stacked, and then a small heat insulation element 1 (porous Si foam, thickness: 3 mm, 0.07 mm) is stacked on top of it. Then, stack 15 separator / negative electrode / separator / positive electrode cells and one separator / negative electrode / separator cell again, and then attach the outside of the electrode assembly with PET tape.

[0143] The electrode assembly thus prepared is embedded together with the electrolyte in a pouch and sealed to manufacture a secondary battery.

[0144] At this point, the electrolyte used is an electrolyte in which LiPF6 is dissolved to a concentration of 1.0 M in a non-aqueous organic solvent having a composition of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 30:70 (volume ratio) and ethylene carbonate (VC) is incorporated at 3% by weight.

[0145] The battery was charged at 0.1C for 3 hours, activated at 30% SOC, subjected to aging and venting, and then charged at 0.33C to 4.2 V (SOC 100%) under CC / CV conditions.

[0146] <Example 2>

[0147] The secondary battery is manufactured in the same manner as in Example 1, except that a heat-insulating element 2 with a negative electrode size (silica aerogel, thickness: 1 mm, 0.04 mm) is used. Up to 0.05 ( ) as the insulation element in Example 1.

[0148] <Example 3>

[0149] The secondary battery is manufactured in the same manner as in Example 1, except that a heat insulation element 3 with a negative maximum size (glass fiber + polyamide resin (50 wt%:50 wt%), thickness: 0.2 mm, 0.05 mm) is used. ( ) as the insulation element in Example 1.

[0150] <Comparison Example 1>

[0151] The secondary battery is manufactured in the same manner as in Example 1, except that: in Example 1, a heat insulation element 2 with a negative electrode size of 0.04 mm (silica aerogel, thickness: 1 mm) is used. Up to 0.05 As a heat insulation component, 15 separator / negative electrode / separator / positive electrode unit cells, one separator / negative electrode / separator unit cell, another 15 separator / negative electrode / separator / positive electrode unit cells, and one separator / negative electrode / separator unit cell are stacked sequentially to prepare an electrode assembly, and the heat insulation component 2 is located between the electrode assembly and the bag-shaped box.

[0152] <Comparison Example 2>

[0153] The secondary battery is manufactured in the same manner as in Example 1, except that in Example 1, the heat insulation component 1 is not inserted.

[0154] <Experimental Example 1>

[0155] Thermocouples are attached to the center portions of the flat surfaces of the secondary batteries manufactured in Example 1, and the batteries are stacked such that four secondary batteries are stacked together with double-sided tape. A heater (120 mm × 60 mm) is then placed on the first secondary battery. Thermocouples are attached between the heater and the first secondary battery, and the heater is secured with PI tape. A 10T Superwool insulation piece (600 mm × 80 mm) is inserted into the lower plate of the modular simulation fixture. The stacked batteries are then placed inside the modular simulation fixture, and another 10T Superwool insulation piece (600 mm × 80 mm) is inserted between the stacked batteries and the fixture. A gasket is then placed on the lower plate of the fixture, and the upper plate of the fixture is secured with bolts and nuts.

[0156] The heat transfer test was performed by heating the heater at a rate of 5°C / second and inducing thermal runaway in the first secondary cell. The voltage of the secondary cells was measured using a data logger, and the time taken from the first secondary cell reaching V=0 to the fourth secondary cell reaching V=0 was also measured. The results are shown in Table 1 below.

[0157] The secondary batteries manufactured in Examples 2 to 3 and Comparative Examples 1 to 2 were also subjected to the above tests.

[0158] [Table 1]

[0159] Heat transfer test (time) Example 1 1 minute 52 seconds Example 2 6 minutes and 34 seconds Example 3 2 minutes Comparison Example 1 2 minutes and 47 seconds Comparison Example 2 49 seconds

[0160] Reviewing Table 1 above, it can be determined that when the insulation is applied inside the secondary battery as in this disclosure, heat transfer is slower than in Comparative Example 2 where no insulation is applied inside the secondary battery.

[0161] On the other hand, referring to Example 2 and Comparative Example 1, which use heat insulation made of the same material, it can be determined that when the heat insulation is applied to the middle part of the electrode assembly, heat transfer can be suppressed more effectively than when the heat insulation is applied to the outside.

[0162] Furthermore, it can be determined that, compared to porous silicone foam, insulation components prepared by combining silica aerogel or glass fiber with non-combustible resin exhibit better insulation performance relative to thickness. It is evident that the combination of glass fiber and non-combustible resin has low thermal conductivity, thus allowing for a reduction in thickness, but the insulation performance decreases with decreasing thickness. Therefore, it can be seen that when using an insulation component made of silica aerogel with a thickness of approximately 1 mm, the heat transfer delay effect is optimal, without a significant reduction in energy density.

[0163] Although preferred embodiments of the present disclosure have been described in detail above with reference to the accompanying drawings, the scope of the present disclosure is not limited thereto, and various modifications and improvements can be made by those skilled in the art using the basic concept of the present disclosure as defined in the appended claims, and these modifications and improvements also fall within the scope of the present disclosure.

[0164] [Description of reference numerals in the attached figures]

[0165] 11: Electrode

[0166] 12: Thermal insulation components

[0167] 100, 200: Secondary batteries

[0168] 110, 120, 210, 220, 230: Single-cell battery

[0169] 130, 231, 232: Thermal insulation components

[0170] Industrial applicability

[0171] According to this disclosure, the secondary battery of the present invention has one or more heat insulation elements inserted therein, which have the effect of suppressing heat transfer within the secondary battery. Furthermore, one or more heat insulation elements are located between two or more cell units. Thus, even if thermal runaway or fire occurs within the secondary battery, the heat insulation elements can prevent heat transfer between cell units within a single secondary battery and reduce the capacity at the point of thermal runaway or fire, which is effective in reducing explosive force and further improving safety.

Claims

1. A secondary battery, comprising: The electrode assembly includes a positive electrode, a negative electrode, and a separator; and an electrolyte. The electrode assembly includes two or more cell units and one or more heat insulation components. One or more of the heat insulation elements are located between the two or more cell units.

2. The secondary battery according to claim 1, in, Each of the two or more cell units includes: one or more electrodes selected from a group consisting of a positive electrode and a negative electrode; and a separator.

3. The secondary battery according to claim 2, in, Each of the two or more cell units is a single cell including a positive or negative electrode and a separator, a dual cell stacked such that electrodes with the same polarity are located at both ends, or a full cell stacked such that electrodes with different polarities are located at both ends.

4. The secondary battery according to claim 1, in, One or more of the insulation elements are located in the middle portion based on the stacking orientation of the electrode assembly.

5. The secondary battery according to claim 1, in, This includes one or more insulation elements, which may be five or fewer in number.

6. The secondary battery according to claim 1, in, When the number of the one or more heat insulation elements is odd, the heat insulation elements are positioned to be uniformly arranged between facing cell cells based on the stacking direction of the electrode assemblies, including the middle portion.

7. The secondary battery according to claim 1, in, When the number of one or more heat insulation elements is even, the heat insulation elements are positioned to be evenly arranged between the cell units facing each other.

8. The secondary battery according to claim 1, in, Includes one or two of the aforementioned one or more insulation elements.

9. The secondary battery according to claim 1, in, The area of ​​each of the one or more thermal insulation elements is 100% to 110% of the area of ​​the negative electrode.

10. The secondary battery according to claim 1, in, The one or more thermal insulation elements are positioned to completely cover the facing electrodes.

11. The secondary battery according to claim 10, in, The one or more thermal insulation elements are positioned to cover a portion of the tabs protruding from the facing electrodes.

12. The secondary battery according to claim 1, in, The thickness of each of the one or more insulation elements is from 0.1 mm to 5 mm.

13. The secondary battery according to claim 12, in, The thickness of each of the one or more thermal insulation elements is from 0.1 mm to 2 mm.

14. The secondary battery according to claim 1, in, Each of the one or more insulation elements comprises porous Si foam, silica aerogel, or a non-combustible resin containing glass fibers.

15. The secondary battery according to claim 14, in, The one or more insulation elements comprise silica aerogel.

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