Secondary battery including insulation material

Abstract

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

Description

Secondary battery containing insulation

[0001] Cross-citation with related application(s)

[0002] This application claims the benefit of priority to Korean Patent Application No. 10-2024-0003157, filed January 8, 2024, the entire contents of which are incorporated herein by reference.

[0003] The present invention relates to a secondary battery including an insulating material.

[0004] As technological developments and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. In particular, secondary batteries are attracting significant attention as an energy source not only for mobile devices such as cell phones, digital cameras, laptops, and wearable devices, but also for powertrains such as electric bicycles, electric cars, and hybrid electric vehicles.

[0005] Typically, lithium secondary batteries include a cathode, an anode, a separator interposed between the anode and cathode, an electrolyte, an organic solvent, and other components. The cathode, due to its unstable structure when charged, can generate oxygen. This generation of oxygen poses a significant risk of ignition, and research and development are being conducted to improve the safety of lithium secondary batteries.

[0006] Among the safety assessments of these lithium secondary batteries, one of the most important safety factors is the thermal propagation test. This test determines whether a lithium secondary battery can withstand a module or pack for more than five minutes without ignition. However, with the recent rise in demand for high capacity and high energy density, lithium secondary batteries using nickel-based cathode active materials with excessive nickel content are finding it difficult to pass this test, raising safety concerns.

[0007] Meanwhile, in order to increase safety, a technology has been developed to apply insulation (12) between secondary batteries (11) as shown in Fig. 1 when manufacturing lithium secondary batteries as modules or packs, or similarly to apply insulation between modules.

[0008] However, as the capacity and energy density of individual lithium secondary batteries increase, the explosive power of a single lithium secondary battery increases, making it difficult for modules and packs to pass the above-mentioned heat transfer test. In other words, the safety of lithium secondary batteries remains an issue.

[0009] Therefore, it is necessary to develop technology that can solve these problems starting from the unit of lithium secondary batteries.

[0010] The purpose of the present invention is to provide a secondary battery that can improve safety issues due to thermal transfer by suppressing heat transfer even in a secondary battery unit when a thermal runaway or ignition problem occurs, thereby reducing the capacity of the secondary battery that causes thermal runaway or ignition.

[0011] A secondary battery according to one embodiment of the present invention is a secondary battery including an electrode assembly including a positive electrode, a negative electrode, a separator, and an electrolyte.

[0012] The electrode assembly comprises two or more unit cells and one or more insulating materials,

[0013] It is characterized in that at least one of the above one or more insulating materials is positioned between the above two or more unit cells.

[0014] Here, each of the two or more unit cells may include at least one electrode selected from the group consisting of anodes and cathodes and a separator, and specifically, each of the two or more unit cells may be a monocell including one of the anode or cathode electrodes and a separator, a bicell stacked so that electrodes with the same polarity are positioned at both ends, or a full cell stacked so that electrodes with different polarities are positioned at both ends.

[0015] Meanwhile, at least one of the above-mentioned one or more insulating materials may be positioned in the middle portion based on the stacking direction of the electrode assembly.

[0016] In one specific example, the above one or more insulating materials may be included in a number of one or more and five or less, and in detail, one or two may be included.

[0017] At this time, since it is preferable that the one or more insulating materials are evenly arranged, when the one or more insulating materials are odd in number, they can be positioned to be evenly arranged between unit cells facing each other, including the middle portion, based on the stacking direction of the electrode assembly, and when the one or more insulating materials are even in number, the insulating materials can be positioned to be evenly arranged between unit cells facing each other.

[0018] In addition, the area of ​​the above one or more insulating materials may be 100% to 110% of the area of ​​the cathode, and in detail, may be positioned so as to entirely cover the facing electrode, and further, may be positioned so as to cover a portion of the tab protruding from the facing electrode.

[0019] Moreover, the thickness of each of the above one or more insulating materials may be 0.1 mm to 5 mm, and specifically 0.2 mm to 2 mm.

[0020] Each of these one or more insulating materials may include a non-combustible resin including porous Si foam, silica aerogel, or glass fiber, and more specifically, may include silica aerogel.

[0021] Figure 1 is a cross-sectional schematic diagram of a conventional battery module.

[0022] Figure 2 is a cross-sectional schematic diagram of a secondary battery according to one embodiment of the present invention.

[0023] Figure 3 is a cross-sectional schematic diagram of a secondary battery according to another embodiment of the present invention.

[0024] Figure 4 is a partially exploded schematic diagram of an electrode assembly to show the location of an insulating material according to one embodiment of the present invention.

[0025] Figure 5 is a top view of a portion of an electrode assembly according to one embodiment of the present invention.

[0026] Hereinafter, various embodiments of the present invention will be described in detail with reference to the attached drawings so that those skilled in the art can easily implement the invention. The present invention may be implemented in various different forms and is not limited to the embodiments described herein.

[0027] In order to clearly explain the present invention, parts that are not related to the description are omitted, and the same reference numerals are used for identical or similar components throughout the specification.

[0028] Furthermore, the sizes and thicknesses of each component shown in the drawings are arbitrarily indicated for convenience of explanation, and thus the present invention is not necessarily limited to the illustrated components. In the drawings, the thicknesses are enlarged to clearly represent various layers and regions. Furthermore, in the drawings, the thicknesses of some layers and regions are exaggerated for convenience of explanation.

[0029] Additionally, throughout the specification, whenever a part is said to “include” a component, this does not mean that it excludes other components, but rather that it may include other components, unless otherwise specifically stated.

[0030] Additionally, throughout the specification, when we say "plane", we mean when the target portion is viewed from above, and when we say "cross-section", we mean when the target portion is viewed from the side in a cross-section cut vertically.

[0031] The terms "about," "substantially," and the like used throughout this specification are used in a sense of or near to the numerical values ​​when manufacturing and material tolerances inherent in the meanings referred to are presented, and are used to prevent unscrupulous infringers from unfairly exploiting disclosures that mention exact or absolute values ​​to aid understanding of this specification.

[0032] The terms “width,” “length,” “thickness,” and “depth” used in this specification are based on the definitions in the specification.

[0033]

[0034] According to one embodiment of the present invention,

[0035] A secondary battery comprising an electrode assembly including a positive electrode, a negative electrode, a separator, and an electrolyte,

[0036] The electrode assembly comprises two or more unit cells and one or more insulating materials,

[0037] A secondary battery is provided in which at least one of the above-mentioned one or more insulating materials is positioned between the above-mentioned two or more unit cells.

[0038] FIG. 2 schematically illustrates a cross-sectional view of a secondary battery (100) according to one embodiment of the present invention, and FIG. 2 schematically illustrates a cross-sectional view of a secondary battery (200) according to another embodiment of the present invention.

[0039] Referring to FIG. 2, a secondary battery (100) includes an electrode assembly including two unit cells (110, 120) and one insulator (130), and an electrolyte (not shown), wherein the insulator (130) is located between the unit cells (110, 120).

[0040] In FIG. 2, an electrode assembly including two unit cells (110, 120) and one insulator (130) is illustrated, but this is not limited and may have a structure including two or more unit cells and one or more insulators. As another example, referring to FIG. 3, a secondary battery (200) may have a structure including an electrode assembly including three unit cells (210, 220, 230) and two insulators (231, 232) and an electrolyte (not shown), or may include more than that.

[0041] However, for convenience of explanation, a configuration including one insulator and a configuration including two insulators are illustrated in FIG. 2, and the description will be made with reference to this.

[0042] Meanwhile, each of these unit cells may have a structure including one or more electrodes selected from the group consisting of anodes and cathodes and a separator.

[0043] Specifically, each of the unit cells may be a monocell including either a positive or negative electrode and a separator, a bicell stacked with electrodes of the same polarity positioned at both ends, or a full cell stacked with electrodes of different polarities positioned at both ends.

[0044] At this time, there is no limit to the number of electrodes and separators stacked in one unit cell.

[0045] Referring again to FIG. 2, the unit cells (110, 120) may each include an anode (111, 121), a cathode (112, 122), and a separator (113, 123), and may be bi-cells stacked so that the cathodes (112, 122) are positioned at both ends.

[0046] Of course, the drawing shows that one unit cell (110, 120) is positioned on each side of the insulation (130), but this is divided for convenience of explanation, and it may have a structure in which two or more unit cells are stacked on one side of the insulation (130). In other words, it may have a structure in which one or more types of unit cells selected from the group consisting of monocells, bicells, and full cells are stacked on one side of the insulation (130).

[0047] Meanwhile, another component, insulation, may be included in one or more, and more specifically, in one or more and five or fewer.

[0048] Beyond the above range, if more than 5 are included, the insulation effect may increase, but the energy density based on the entire volume of the secondary battery may decrease, which may increase the cost and overall volume, which is not desirable.

[0049] Considering the above problems, more specifically, one or two insulating materials may be included in the secondary battery.

[0050] Accordingly, the present invention focuses on FIGS. 2 and 3, which include one or two insulating materials, but is not limited thereto, and these represent cases where an odd or even number of insulating materials are included.

[0051] Referring to FIG. 2, the secondary battery (100) includes one insulating material (130), i.e., an odd number of insulating materials (130).

[0052] At this time, the insulation (130) is located in the middle part based on the stacking direction of the electrode assembly. Here, the middle part means the degree to which the number of electrodes differs by one or two from the same number of electrodes and separators located on both sides of the insulation (130) based on the stacking direction of the electrode assembly.

[0053] In this way, when the insulation material (130) is located in the middle, the capacity of the secondary battery participating in the reaction during thermal runaway or ignition can be reduced by half, making it more effective in suppressing thermal transfer.

[0054] Meanwhile, when an odd number of insulating materials are included, such as three or more, they can be positioned so as to be evenly arranged between unit cells facing each other, including the middle portion.

[0055] The above uniform arrangement is explained with reference to FIG. 3, which illustrates a drawing including two insulating materials.

[0056] Referring to FIG. 3, the secondary battery (200) includes two insulators (231, 232), i.e., an even number of insulators, and each of these two insulators (231, 232) is positioned between unit cells (210, 220, 230).

[0057] At this time, the insulating materials (231, 232) are positioned so as to be evenly arranged between the unit cells (210, 220, 230) facing each other. That is, each of the insulating materials (231, 232) may be formed with the same spacing (b). Furthermore, the electrode assembly may be divided into three equal parts (a=b=c) based on the stacking direction, and the insulating materials (231, 232) may be included between them.

[0058] That is, in the event of thermal runaway or ignition within the secondary battery, it is desirable to prevent heat transfer by minimizing the capacity of the insulation material, so it is desirable to place it in an evenly divided section so that the capacity is 1 / n.

[0059] Therefore, when an odd number of insulations are included, it is desirable to have at least one insulation located in the middle.

[0060] Moreover, it is desirable that the above insulation material be able to perform its role even if thermal runaway or ignition occurs anywhere in the component. In general, thermal runaway or ignition in a secondary battery is caused by short circuit between the positive and negative electrodes, oxygen generation due to side reactions between the positive and negative electrodes, and lithium dendrite formation at the negative electrode. Therefore, it is desirable that the insulation material be formed with a width that can prevent these.

[0061] At this time, since the cathode is generally manufactured larger than the anode, it is preferable that the insulating material have an area of ​​100% to 120% of the area of ​​the cathode, more specifically, 100% to 110%.

[0062] To explain this more specifically, FIG. 4 shows a partially exploded perspective view of a secondary battery (100), and FIG. 5 shows a perspective top view of a portion of the secondary battery (100).

[0063] Referring to FIGS. 4 and 5, the area (Si) of the insulation material (130) may be equal to or larger than the area (Sa) of the cathode (112) facing the separator (113), and may be positioned to entirely cover it. That is, when it has the same area (Si=Sa) as the cathode (112), it may be positioned to entirely cover the remaining area except for the tab (112a) of the cathode (112), and when it is larger, it may be positioned to cover the entire cathode (112) and a portion of the tab (112a) of the cathode (112).

[0064] If it is outside the above range and smaller than the cathode, problems such as short circuits occurring at the cathode end cannot be effectively prevented, and heat transfer may occur through the end. If it is too wide, the overall volume increases, and manufacturing costs also increase, and thus it is desirable to satisfy the above range.

[0065] Furthermore, referring again to FIG. 2, the thickness (t) of the insulation (130) may be 0.1 mm to 5 mm, specifically 0.1 mm to 2 mm, and more specifically 0.1 mm to 1 mm.

[0066] If it is too thick beyond the above range, it may increase the overall volume of the secondary battery, and if it is too thin, it is not desirable because the insulation effect intended by the present invention cannot be effectively obtained.

[0067] Each of these above-mentioned insulating materials may include a non-combustible resin including porous Si foam, silica aerogel, or glass fiber, and more specifically may include silica aerogel, and more specifically may be composed of the same.

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

[0069] The porosity of the above porous Si foam can be measured using the AUTOSORB iQ series (manufactured by Quantachrome) according to ASTM D4641, and the average pore diameter is measured using a scanning electron microscope (FE-SEM) (Hitachi S-4800 Scanning Electron Microscope) at a magnification of 2,500 times on the sample surface. Then, the major axis length of the surface pores confirmed in a randomly sampled range (more than 10 μm in width and more than 15 μm in length) in the measured image is measured as the pore size. The number of measurements is at least 10 or more, and the average value of the pore sizes obtained after the measurements is calculated.

[0070] Such porous Si foam can be manufactured by foaming silicon (Si), and is not limited to any conventionally known method.

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

[0072] Additionally, the average diameter of these pores may be 1 nm to 100 nm, specifically 5 nm to 50 nm, and even more specifically 5 nm to 10 nm.

[0073] At this time, the porosity and average pore diameter of the silica aerogel were measured using a Micrometrics ASAP 2010 device under partial pressure (0.11 <p / po<1)에 따른 질소의 흡 / 탈착량으로 분석할 수 있다.

[0074] The above silica aerogel can be manufactured by a method of drying and forming under supercritical conditions using a sol-gel method, and is not limited to any manufacturing method known in the art.

[0075] The above-mentioned non-combustible resin containing glass fiber is in the form of a non-combustible resin coated on a glass fiber reinforcing material, and at this time, the non-combustible resin and the glass fiber can be included in a ratio of 30:70 to 80:20 based on weight, and more specifically, can be included in a ratio of 40:60 to 70:30.

[0076] Here, the non-combustible resin may be at least one selected from the group consisting of polyester, polyamide, polyether sulfone, polyetherimide, polyimide, polyamideimide, polyamide siloxane, polyurethane, polystyrene, polycarbonate, and polymethyl methacrylate.

[0077] The thermal conductivity of such insulation may be, for example, 0.02 to 0.5 W / m·K, specifically 0.03 to 0.1 W / m·K, and even more specifically 0.04 to 0.07 W / m·K.

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

[0079] At this time, the thermal conductivity was evaluated according to the ISO 2207-2 standard of the TPS Hot Disk method. At this time, the measurement model may be TPS 3500.

[0080] Meanwhile, as other components of secondary batteries,

[0081] The above positive electrode may have a structure including a positive electrode current collector and a positive electrode active material layer formed on one or both sides of the positive electrode current collector.

[0082] Here, the positive electrode current collector may be any conductive material that does not induce chemical changes in the battery, and is not particularly limited. For example, the current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like.

[0083] The positive electrode current collector may have a thickness of 3 μm to 500 μm, and fine irregularities may be formed on the surface of the positive electrode current collector to enhance adhesion to the positive electrode active material layer. The positive electrode current collector may be used in various forms, such as films, sheets, foils, nets, porous bodies, foams, and non-woven fabrics.

[0084] The above positive electrode active material layer includes a positive electrode active material and may include a conductive agent, a binder, and other additives as needed.

[0085] The above-mentioned positive electrode active material is not limited to a compound capable of reversible intercalation and deintercalation of lithium, but specifically may include a lithium metal oxide containing lithium and one or more metals 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.

[0086] [Chemical Formula 1]

[0087] Li 1+x Ni a Co b Mn c M 1-(a+b+c) O2

[0088] In the above formula,

[0089] M is at least one selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg, and Mo,

[0090] 0≤x≤0.5, 0.6≤a<1, 0 <b<0.4, 0<c<0.4이다.

[0091] In addition, the positive electrode active material is a lithium metal oxide, such as a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (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 oxides (e.g., Li 1+x’’’ Ni 1-Y1 Co Y1 O2(here, -0.5≤x'''≤0.5, 0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, Li 1+x’’’’ Co 1-Y2 Mn Y2 O2(here, -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 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 (wherein, -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) oxide (e.g., Li 1+a3 (Ni p2 Co q2 Mn r2 M s2 )O2 (wherein, 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 independent elements, respectively, -0.5≤a3≤0.5, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.), lithium iron phosphate (e.g., Li 1+a4 Fe 1-p3 M p3 (PO 4-b4 )X b4 (Here, 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 the like, and any one or two or more compounds thereof may be included.

[0092] The above positive electrode active material may be included in an amount of 60 to 98 wt%, preferably 80 to 98 wt%, and more preferably 90 to 98 wt%, based on the total weight of the positive electrode active material layer.

[0093] The conductive agent is a component for further improving the conductivity of the positive electrode active material, and the conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery, and for example, carbon powder such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; fluorinated carbon powder; conductive powder such as aluminum powder or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives, etc. can be used.

[0094] The above-mentioned conductive material may be included in an amount of 0.1 to 20 wt%, specifically 0.5 to 10 wt%, and more specifically 0.5 to 5 wt%, based on the total weight of the positive electrode active material layer.

[0095] The above binder is a component that assists in bonding between the conductive material, the positive electrode active material, and the positive electrode current collector. Examples of such binders include polyvinylidene fluoride (PVDF), polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polyethylene, polypropylene, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber, fluororubber, and various copolymers thereof.

[0096] Typically, the binder may be included in an amount of 0.5 to 20 wt%, specifically 0.5 to 10 wt%, and more specifically 0.5 to 5 wt%, based on the total weight of the positive electrode active material layer.

[0097] In addition, the above-mentioned other additives may further include, for example, fillers as components that suppress expansion. The fillers are not particularly limited as long as they can suppress expansion of the electrode without causing chemical changes in the battery, and examples thereof include olefin polymers such as polyethylene and polypropylene; fibrous materials such as glass fiber and carbon fiber; and the like.

[0098] The above negative electrode may have a structure including a negative electrode current collector and a negative electrode active material layer formed on one or both sides of the negative electrode current collector, and the negative electrode active material layer may further include electrode materials such as a conductive material and a binder as described in the positive electrode in addition to the negative electrode active materials.

[0099] The negative current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

[0100] The above-mentioned negative electrode collector may typically have a thickness of 3 μm to 500 μm, and like the positive electrode collector, it may be provided with fine irregularities on the surface of the negative electrode collector to enhance the bonding strength of the negative electrode active material. For example, it may be used in various forms such as a film, sheet, foil, net, porous body, foam, or non-woven fabric.

[0101] The above negative active material may include at least one selected from the group consisting of lithium metal, a carbon material capable of reversibly intercalating / deintercalating lithium ions, a metal or an alloy of these metals and lithium, a metal composite oxide, a material capable of doping and dedoping lithium, and a transition metal oxide.

[0102] As the carbon material capable of reversibly intercalating / deintercalating the lithium ions, any carbon-based negative electrode active material commonly used in lithium-ion secondary batteries can be used without particular limitation, and representative examples thereof include crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as natural graphite or artificial graphite in an amorphous, plate-like, flake-like, spherical, or fibrous form, and examples of the amorphous carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0103] As the above metal or an alloy of these metals with lithium, a metal 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 or an alloy of these metals with lithium may be used.

[0104] The above metal composite oxides include PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, LixFe2O3(0≤x≤1), Li x WO2(0≤x≤1) and Sn x Me 1-x Me' y O z (Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, elements of group 1, 2, and 3 of the periodic table, halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8) 로 이루어진 군에서 선택되는 것이 사용될 수 있다.

[0105] Materials capable of doping and dedoping the above lithium include Si, SiO x(0 <x≤2), Si-Y 합금(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Si은 아님), Sn, SnO2, Sn-Y(상기 Y는 알칼리 금속, 알칼리 토금속, 13족 원소, 14족 원소, 전이금속, 희토류 원소 및 이들의 조합으로 이루어진 군에서 선택되는 원소이며, Sn은 아님) 등을 들 수 있고, 또한 이들 중 적어도 하나와 SiO2를 혼합하여 사용할 수도 있다. 상기 원소 Y로는 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 및 이들의 조합으로 이루어진 군에서 선택될 수 있다.

[0106] Examples of the above transition metal oxides include lithium-containing titanium composite oxide (LTO), vanadium oxide, and lithium vanadium oxide.

[0107] The negative electrode active material may be included in an amount of 60 to 99 wt%, preferably 80 to 99 wt%, and more preferably 90 to 98 wt%, based on the total weight of the negative electrode active material layer.

[0108] When the metal itself is used without including a cathode composite layer in the above cathode, it can be manufactured by physically bonding, rolling, or depositing the metal onto the metal thin film itself or the cathode current collector. The deposition method can use an electrical deposition method or a chemical vapor deposition method.

[0109] For example, the metal to be bonded / rolled / deposited on the metal thin film itself or the negative electrode current collector may include one metal selected from the group consisting of lithium (Li), nickel (Ni), tin (Sn), copper (Cu), and indium (In), or an alloy of two metals.

[0110] The above separator can be used without any special restrictions as long as it is commonly used as a separator in a lithium secondary battery, and it is particularly preferable that it has low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity.

[0111] For example, as a separator, a porous polymer film including a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof can be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc., can also be used as a separator.

[0112] Alternatively, it may be a Safety Reinforced Separator (SRS) membrane having a coating layer including a binder and inorganic particles formed on one or both sides of a polymer substrate as described above.

[0113] The above electrolyte may be a lithium non-aqueous electrolyte, and the lithium non-aqueous electrolyte may include a lithium salt and a non-aqueous organic solvent.

[0114] At this time, the lithium salt is used as a medium for transferring ions within a lithium secondary battery. Lithium salt is, for example, Li as a cation. + , and the anion is 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 - At least one selected from the group consisting of

[0115] Specifically, the lithium salt is 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 it is preferable to include Li(N(SO2CF3)2) in terms of excellent stability.

[0116] In addition to these, lithium salts commonly used in the electrolyte of lithium secondary batteries can be used without limitation.

[0117] The lithium salt may be appropriately changed within a generally usable range, but in order to obtain an optimal effect of forming a film for preventing corrosion on the electrode surface, it may be included in the electrolyte at a concentration of 0.5 M to 3 M, specifically, at a concentration of 1 M to 2.5 M, and more specifically, at a concentration of 1 M to 2 M. When the concentration of the lithium salt satisfies the above range, the effect of improving the cycle characteristics during high-temperature storage of a lithium secondary battery is sufficient, and the viscosity of the electrolyte is appropriate, so that the electrolyte impregnation property can be improved.

[0118] The above non-aqueous organic solvent is not limited as long as it can minimize decomposition due to oxidation reactions during the charge / discharge process of a lithium secondary battery and can exhibit the desired properties together with additives. For example, carbonate-based organic solvents, ether-based organic solvents, or ester-based organic solvents can be used alone or in combination of two or more, and specifically, carbonate-based organic solvents can be used.

[0119] Among the organic solvents, the carbonate-based organic solvent may include at least one of a cyclic carbonate-based organic solvent and a linear carbonate-based organic solvent. Specifically, the cyclic carbonate-based organic solvent may 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-pentylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and fluoroethylene carbonate (FEC), and specifically, may 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.

[0120] In addition, 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, ethylmethyl carbonate (EMC), methylpropyl carbonate, and ethylpropyl carbonate, and more specifically, may include dimethyl carbonate.

[0121] The above ether organic solvent may be any one selected from 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, but is not limited thereto.

[0122] The above ester organic solvent may include at least one selected from the group consisting of linear ester organic solvents and cyclic ester organic solvents.

[0123] Specific examples of the linear ester organic solvent include, but are not limited to, one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, and butyl propionate, or a mixture of two or more thereof.

[0124] The above cyclic ester organic solvent may be, as a specific example, one selected from the group consisting of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more thereof, but is not limited thereto.

[0125] Among the above ester solvents, cyclic carbonate compounds are preferably used as high-viscosity organic solvents with high dielectric constants, which facilitate the dissociation of lithium salts in the electrolyte. When low-viscosity, low-dielectric constant linear carbonate compounds and linear ester compounds, such as dimethyl carbonate and diethyl carbonate, are mixed and used in an appropriate ratio with these cyclic carbonate compounds, an electrolyte with high electrical conductivity can be produced, and thus the compounds can be used more preferably.

[0126] Furthermore, the lithium non-aqueous electrolyte further includes a functional additive, and the functional additive may be included to prevent cathode collapse from occurring in a high-power environment, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge prevention, and swelling improvement effects during high-temperature storage.

[0127] Specifically, the functional additive may include at least one functional additive selected from the group consisting of, as representative examples, sultone compounds, sulfite compounds, sulfone compounds, sulfate compounds, halogen-substituted carbonate compounds, nitrile compounds, cyclic carbonate compounds, phosphate compounds, borate compounds, and lithium salt compounds.

[0128] The above sultone-based compound may include at least one compound selected from the group consisting of 1,3-propane sultone (PS), 1,4-butane sultone, ethene sultone, 1,3-propene sultone (PRS), 1,4-butene sultone, and 1-methyl-1,3-propene sultone, and may be included in an amount of 0.3 wt% to 5 wt%, specifically 1 wt% to 5 wt%, based on the total weight of the electrolyte. When the content of the sultone-based compound in the electrolyte exceeds 5 wt%, an excessively thick film may be formed on the electrode surface, which may cause an increase in resistance and a deterioration in output, and the resistance may also increase due to an excessive amount of additive, which may deteriorate the output characteristics.

[0129] The above sulfite compound may include at least one compound selected from the group consisting of ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene 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 glycol sulfite, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0130] The above sulfone compound may include at least one compound selected from the group consisting of divinyl sulfone, dimethyl sulfone, diethyl sulfone, methylethyl sulfone, and methylvinyl sulfone, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0131] The above sulfate compound may include ethylene sulfate (Esa), trimethylene sulfate (TMS), or methyl trimethylene sulfate (MTMS), and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0132] In addition, the halogen-substituted carbonate compound may include fluoroethylene carbonate (FEC) and may be included in an amount of 5 wt% or less based on the total weight of the electrolyte. If the content of the halogen-substituted carbonate compound in the electrolyte exceeds 5 wt%, cell swelling performance may deteriorate.

[0133] In addition, the nitrile compound may include at least one compound selected from the group consisting of succinonitrile, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valeronitrile, caprylonitrile, heptanenitrile, cyclopentanecarbonitrile, cyclohexanecarbonitrile, 2-fluorobenzonitrile, 4-fluorobenzonitrile, difluorobenzonitrile, trifluorobenzonitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0134] The cyclic carbonate compound may be vinylene carbonate (VC) or vinylethylene carbonate, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte. If the content of the cyclic carbonate compound in the electrolyte exceeds 3 wt%, the cell swelling suppression performance may deteriorate.

[0135] The above phosphate compound may include at least one compound selected from the group consisting of lithium difluoro(bisoxalato)phosphate, lithium difluorophosphate, tetramethyl trimethyl silyl phosphate, trimethyl silyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphite, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0136] The above borate compound may include lithium oxalyldifluoroborate, and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0137] The above lithium salt-based compound is a compound different from the lithium salt included in the lithium non-aqueous electrolyte, and may include at least one compound selected from the group consisting of LiPO2F2, LiODFB, LiBOB (lithium bisoxalatoborate (LiB(C2O4)2) and LiBF4), and may be included in an amount of 3 wt% or less based on the total weight of the electrolyte.

[0138] The functional additives may be mixed in an amount of two or more, and may be included in an amount of 20 wt% or less, specifically 0.1 wt% to 10 wt%, based on the total weight of the lithium non-aqueous electrolyte. If the content of the functional additive exceeds 20 wt%, there is a possibility that excessive side reactions may occur within the lithium non-aqueous electrolyte during charging and discharging of the battery. In particular, since they may not be sufficiently decomposed at high temperatures, they may exist as unreacted substances or precipitated substances within the lithium non-aqueous electrolyte at room temperature. Accordingly, side reactions that reduce the lifespan or resistance characteristics of the lithium metal battery may occur.

[0139]

[0140] <Example 1>

[0141] As a cathode active material, LiNi 0.8 Co 0.1 Mn 0.1O2, carbon black as a conductive agent, and PVdF as a binder were mixed in a weight ratio of 94:3:3 under NMP to prepare a slurry, and then the slurry was coated on both sides of a 20 μm thick Al current collector to a thickness of 70 μm, dried, and rolled to a total anode thickness of 120 μm to prepare a positive electrode.

[0142] A slurry was prepared by mixing natural graphite as an anode active material, carbon black as a conductive material, styrene-butadiene rubber (SBR) as a binder, and carboxymethyl cellulose (CMC) as a thickener in water at a weight ratio of 95:1:3:1, and then the slurry was coated on both sides of a 10 μm thick Cu current collector to a thickness of 90 μm, dried, and rolled to a total anode thickness of 130 μm to prepare an anode.

[0143] In addition, an SRS membrane was prepared as a separator (a coating layer of Al2O3 and PVdF mixed in a weight ratio of 80:20 was formed on both sides of a 15㎛ thick polypropylene substrate, each with a thickness of 5㎛).

[0144] Using the above anode, cathode, and separator, a unit cell was manufactured by stacking and laminating the separator / cathode / separator / anode, and after stacking 15 such unit cells, a unit cell manufactured with the separator / cathode / separator was additionally stacked, and then an insulating material 1 (porous Si foam, 3 mm thick, 0.07 W / m·K) having the size of the cathode was laminated thereon. After that, 15 of the above separator / cathode / separator / anode unit cells and 1 separator / cathode / separator unit cell were stacked again, and then the outside of the electrode assembly was taped with PET tape.

[0145] The electrode assembly manufactured in this manner was embedded and sealed in a pouch case together with an electrolyte to manufacture a secondary battery.

[0146] At this time, the electrolyte was used by dissolving LiPF6 to 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 containing 3 wt% of vinylene carbonate (VC).

[0147] The battery was activated at 30% SOC by charging at 0.1C for 3 hours, aged and degassed, and then charged CC / CV to 4.2V (100% SOC) at 0.33C.

[0148]

[0149] <Example 2>

[0150] A secondary battery was manufactured in the same manner as in Example 1, except that a cathode-sized insulator 2 (silica aerogel, 1 mm thick, 0.04-0.05 W / m·K) was used as an insulator in Example 1.

[0151]

[0152] <Example 3>

[0153] A secondary battery was manufactured in the same manner as in Example 1, except that a cathode-sized insulator 3 (glass fiber + polyamide resin (50:50 wt%), thickness 0.2 mm, 0.05 W / m·K) was used as an insulator in Example 1.

[0154]

[0155] <Comparative Example 1>

[0156] In the above Example 1, an insulator 2 (silica aerogel, thickness 1 mm, 0.04-0.05 W / m·K) of the size of the cathode was used as an insulator, and 15 separator / cathode / separator / anode unit cells, 1 separator / cathode / separator unit cell, 15 separator / cathode / separator / anode unit cells, and 1 separator / cathode / separator unit cell were sequentially stacked to manufacture an electrode assembly, and a secondary battery was manufactured in the same manner as in the above Example 1, except that the insulator 2 was positioned between the electrode assembly and the pouch case.

[0157]

[0158] <Comparative Example 2>

[0159] In the above Example 1, a secondary battery was manufactured in the same manner as in the above Example 1 without inserting the above insulation material 1.

[0160]

[0161] Experimental Example 1

[0162] Thermocouples were each attached to the central portion of the flat surface of the secondary batteries manufactured in Example 1, and a laminated cell was manufactured so that four secondary batteries were laminated using double-sided tape. A heater (120 mm x 60 mm) was placed on the first secondary battery. A thermocouple was attached between the heater and the first secondary battery, and the heater was fixed with PI tape. After inserting 10T superwool insulation (600 mm x 80 mm) into the lower plate of the module simulation jig, the laminated cell was placed inside the module simulation jig, and 10T superwool insulation (600 mm x 80 mm) was inserted between the laminated cell and the jig. A gasket was placed on the lower plate of the jig, and the upper plate of the jig was fastened with bolts and nuts.

[0163] A thermal transfer test was performed by heating the heater at a rate of 5℃ / sec to cause thermal runaway of secondary battery No. 1, and the voltage of the secondary batteries was measured using a datalogger, and the time taken from the point where secondary battery No. 1 became V=0 to the point where secondary battery No. 4 became V=0 was measured, and the results are shown in Table 1 below.

[0164] The same test as above was also performed on the secondary batteries manufactured in Examples 2 to 3 and Comparative Examples 1 to 2.

[0165] Heat transfer test (time) Example 11 minutes 52 seconds Example 26 minutes 34 seconds Example 32 minutes Comparative example 12 minutes 47 seconds Comparative example 249 seconds

[0166] Reviewing Table 1 above, it can be seen that when insulation is applied to the interior of a secondary battery as in the present invention, heat transfer is slowed down compared to Comparative Example 2, where insulation is not applied to the interior of the secondary battery. Meanwhile, referring to Example 2 and Comparative Example 1, which use insulation of the same material, it can be seen that when insulation is applied to the middle portion of the electrode assembly, heat transfer is suppressed more effectively compared to when insulation is applied to the outside.

[0167] In addition, it can be confirmed that the insulation effect per thickness of the insulation material manufactured with a combination of silica aerogel or glass fiber and non-combustible resin is more excellent than that of porous silicone foam, and of course, the combination of glass fiber and non-combustible resin has low thermal conductivity, so the thickness can be reduced, but it can be seen that the insulation effect also decreases as the thickness is reduced, and therefore, when using an insulation material manufactured with silica aerogel with a thickness of about 1 mm, it can be seen that the heat transfer delay effect is the best without a large decrease in energy density.

[0168]

[0169] Although the preferred embodiments of the present invention have been described in detail above with reference to drawings and examples, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concept of the present invention defined in the following claims also fall within the scope of the present invention.

[0170] [Explanation of symbols]

[0171] 11: Electrode

[0172] 12: Insulation,

[0173] 100, 200: Secondary battery

[0174] 110, 120, 210, 220, 230: unit cells

[0175] 130, 231, 232: Insulation

[0176] According to the present invention, the secondary battery of the present invention has an effect of suppressing heat transfer within the secondary battery by having one or more insulating materials inserted therein, and furthermore, since the one or more insulating materials are positioned between two or more unit cells, even if thermal runaway or ignition occurs within the secondary battery due to the inserted insulating materials, the capacity at which thermal runaway or ignition occurs can be reduced by preventing heat transfer between unit cells within a single secondary battery, thereby effectively reducing explosive power and further improving safety.

Claims

1. A secondary battery comprising an electrode assembly including a positive electrode, a negative electrode, a separator, and an electrolyte, The electrode assembly comprises two or more unit cells and one or more insulating materials, A secondary battery wherein at least one of the above one or more insulating materials is positioned between the above two or more unit cells.

2. In paragraph 1, A secondary battery, wherein each of the above two or more unit cells includes at least one electrode selected from the group consisting of a positive electrode and a negative electrode and a separator.

3. In paragraph 2, A secondary battery in which each of the above two or more unit cells is a monocell including one of the positive or negative electrodes and a separator, a bicell stacked with electrodes having the same polarity positioned at both ends, or a full cell stacked with electrodes having different polarities positioned at both ends.

4. In paragraph 1, A secondary battery wherein at least one of the above insulating materials is positioned in the middle of the electrode assembly with respect to the stacking direction.

5. In paragraph 1, A secondary battery containing no more than five of the above insulating materials.

6. In paragraph 1, A secondary battery in which, when the number of the above 1 or more insulating materials is odd, the insulating materials are positioned so as to be evenly arranged between unit cells facing each other, including the middle portion, based on the stacking direction of the electrode assembly.

7. In paragraph 1, A secondary battery in which, when the number of the above 1 or more insulating materials is an even number, the insulating materials are positioned so as to be evenly arranged between the unit cells facing each other.

8. In paragraph 1, A secondary battery comprising one or two of the above insulating materials.

9. In paragraph 1, A secondary battery wherein the area of the above one or more insulating materials is each 100% to 110% of the area of the negative electrode.

10. In paragraph 1, A secondary battery in which the above one or more insulating materials are positioned to entirely cover the facing electrodes.

11. In paragraph 10, A secondary battery wherein the above one or more insulating materials are positioned to cover a portion of a tab protruding from the facing electrode.

12. In paragraph 1, A secondary battery wherein each of the above one or more insulating materials has a thickness of 0.1 mm to 5 mm.

13. In paragraph 12, A secondary battery wherein each of the above one or more insulating materials has a thickness of 0.1 mm to 2 mm.

14. In paragraph 1, A secondary battery wherein the above one or more insulating materials each include a fire-resistant resin including porous Si foam, silica aerogel, or glass fiber.

15. In paragraph 14, A secondary battery wherein the above one or more insulating materials include silica aerogel.

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