Steel sheet for battery case, battery case manufactured therefrom, and cylindrical secondary battery including battery case

Abstract

Disclosed are a steel sheet for a battery case, a battery case manufactured therefrom, and a cylindrical secondary battery including the battery case. The steel sheet comprises 0.02 wt% to 0.08 wt% of carbon (C); 0.01 wt% to 0.1 wt% of niobium (Nb); and the balance of iron (Fe).

Description

[0001] This application claims priority to and the benefit of Korean Patent Application No. 10-2023-0141752 filed on October 23, 2023, Korean Patent Application No. 10-2024-0136630 filed on October 8, 2024, and Korean Patent Application No. 10-2024-0144216 filed on October 21, 2024, in the Korean Intellectual Property Office, the disclosures of which are incorporated herein in their entirety by reference. Technical Field

[0002] The present invention relates to a steel sheet for a battery case and a battery case including the same. More specifically, the present invention relates to a steel sheet for a cylindrical battery case having excellent high temperature properties and a cylindrical case including the same. Background Art

[0003] Rechargeable secondary batteries are used as energy sources for various electronic devices. In particular, rechargeable secondary batteries have attracted attention as energy sources for electric vehicles and hybrid electric vehicles, which are proposed as alternatives to gasoline and diesel vehicles using fossil fuels.

[0004] According to the shape of the battery case, secondary batteries are classified into cylindrical or prismatic batteries, in which an electrode assembly is housed in a cylindrical or prismatic metal can, and pouch-type batteries, in which the electrode assembly is housed in a pouch-shaped case of laminated aluminum sheets.

[0005] A battery case for a cylindrical battery is generally formed of aluminum or stainless steel (particularly, austenitic stainless steel) to increase the rigidity of the battery case.

[0006] However, cylindrical battery cases for electric vehicles have problems with rapid reduction in yield strength at high temperatures and cannot prevent thermal runaway between cells due to sidewall rupture, especially in the event of a fire.

[0007] As a background art of the present invention, although Korean Patent No. 10-2487834 discloses a cylindrical housing made of ferritic stainless steel, the patent publication does not disclose a technology for maintaining strength by suppressing recrystallization of metal elements at high temperatures.

[0008] This section is only intended to provide a better understanding of the background of the invention and therefore may contain information that is not necessarily prior art. Summary of the invention

[0009] An aspect of the present invention is to provide a steel sheet for a battery case having increased strength not only at room temperature but also at high temperatures.

[0010] The steel plate for a battery case may be used as a cylindrical battery case, wherein the strength of the cylindrical battery case is greatly improved at a high temperature of 600° C. or higher, thereby preventing cracking of a side wall and thermal runaway of a battery.

[0011] The above and other aspects and features of the present invention will become apparent from the following description of embodiments of the present invention.

[0012] According to one aspect of the present invention, there is provided a steel sheet for a battery case, the steel sheet comprising: 0.02 wt % to 0.08 wt % of carbon (C); 0.01 wt % to 0.1 wt % of niobium (Nb); and the balance of iron (Fe).

[0013] According to another aspect of the present invention, there is provided a battery case formed of a steel plate for a battery case and having an opening.

[0014] According to still another aspect of the present invention, there is provided a cylindrical secondary battery including: a cylindrical case manufactured from a steel plate for a battery case; a cap assembly sealing the cylindrical case; and an electrode assembly disposed inside the cylindrical can.

[0015] According to the embodiments of the present invention, the steel sheet for a battery case may exhibit high mechanical properties not only at room temperature but also at a high temperature of 600° C. or higher.

[0016] In a typical plated steel sheet for a battery case, a recrystallized texture is generated at a high temperature of 600°C or higher, thereby deteriorating the strength of the steel sheet due to large and uneven grain sizes in the recrystallized texture, and when a cylindrical battery case for an EV is manufactured with such a steel sheet, the battery case may suffer from rupture of its side wall at high temperatures due to heat generation or combustion in the cell, thereby causing thermal runaway of the battery. However, the steel sheet for a battery case according to an embodiment of the invention exhibits high tensile strength even at a high temperature of 600°C or higher, and can prevent thermal runaway caused by rupture of the side wall, while improving the overall strength of a cylindrical secondary battery including an upper cover, thereby enabling the manufacture of a large-diameter cylindrical secondary battery with a diameter of Φ46 or more.

[0017] The steel sheet for a battery case according to an embodiment of the present invention can achieve significant improvements in mechanical properties by adjusting the addition amount of the recrystallization inhibiting element, and has greatly improved machinability by forming a cylindrical battery case to allow the thickness to be reduced to 1.0 mm or less, thereby being able to reduce the weight of the cylindrical secondary battery while effectively increasing the capacity of the battery.

[0018] However, aspects and features of the invention are not limited to the above-described aspects and features, and other aspects and features not mentioned will be clearly understood by those skilled in the art from the detailed description given below. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] The following drawings attached to this specification illustrate embodiments of the present invention and, together with the detailed description of the present invention, further describe aspects and features of the present invention. Therefore, the present invention should not be interpreted as being limited to the drawings:

[0020] Figure 1 is a perspective view of a cylindrical secondary battery according to one embodiment of the present invention;

[0021] Figure 2 is a perspective view of a prismatic battery according to one embodiment of the present invention;

[0022] Figure 3 is a graph showing the results of a room temperature rupture pressure test of a battery case according to one embodiment of the present invention; and

[0023] Figure 4 is a graph showing the results of a burst pressure test of a battery case according to one embodiment of the present invention after heating at 600° C. for 10 minutes. DETAILED DESCRIPTION

[0024] Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. However, it should be understood that the following embodiments are provided by way of illustration, and the present invention is not limited thereto and is only defined by the appended claims and their equivalents.

[0025] When any element is referred to as being disposed (or positioned or located) "above" (or "below") or "on" (or "below") a component, it may mean that the arbitrary element is placed in contact with the upper (or lower) surface of the component, and may also mean that another component may be placed between the component and the arbitrary element disposed (or positioned or located) on (or below) the component.

[0026] Throughout the specification, unless otherwise specified, each element may be singular or plural. In addition, throughout the specification, unless otherwise specified, when "A or B" is stated, it means A, B, or A and B.

[0027] As used herein, "combinations thereof" may refer to mixtures, stacks, composites, copolymers, alloys, blends, and reaction products of the components.

[0028] Unless otherwise defined herein, particle size may refer to average particle size. In addition, particle size refers to average particle size (D50), which refers to the particle size corresponding to 50% by volume in the volume cumulative distribution of corresponding particles. Average particle size can be measured by any method well known in the art (e.g., by a particle size analyzer, a transmission electron microscope image, or a scanning electron microscope image). Alternatively, average particle size (D50) can be measured by counting the number of particles in each particle size range using a device that uses a dynamic light scattering method to analyze data, and then calculating the average particle size (D50) based on the analyzed data. Alternatively, average particle size (D50) can be measured by laser diffraction. More specifically, in the measurement by laser diffraction, the target particles are dispersed in a dispersant, introduced into a commercially available laser diffraction particle analyzer (e.g., Microtrac MT3000), and irradiated with an ultrasonic wave of 28kHz and 60W power, and then the average particle size (D50) corresponding to 50vol% volume in the cumulative volume distribution of the particles is calculated in a measuring device.

[0029] Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.

[0030] The steel sheet for the battery case according to an embodiment of the present invention not only exhibits high yield strength at room temperature to address the expansion of the internal components of the battery, but also exhibits improved high temperature properties by significantly increasing the tensile strength and rupture pressure at a high temperature of 600° C. Specifically, the steel sheet according to the present invention has excellent machinability and improved high temperature properties to be used as a steel sheet for a cylindrical battery case for an electric vehicle (EV), and can suppress sidewall rupture during a high temperature and high power (PPR) test of a cylindrical battery, thereby ensuring the safety of the EV.

[0031] The steel sheet for a battery case according to the present invention is low-carbon steel, and contains the following metal elements.

[0032] Composition of steel sheets for battery housings

[0033] Carbon (C)

[0034] Carbon (C) is added to ensure the strength of the steel plate.

[0035] Specifically, based on the total weight of the steel sheet, carbon (C) may be present in an amount of 0.02wt% to 0.08wt%, for example, 0.02wt%, 0.03wt%, 0.04wt%, 0.05wt%, 0.06wt%, 0.07wt% or 0.08wt%, preferably, 0.03wt% to 0.05wt%. Within the range of this carbon, the steel sheet can achieve the target strength and can maintain toughness to allow forming processes such as DI (deep drawing and thinning drawing) / DRD (drawing and redrawing). Therefore, the steel sheet can be used not only as a steel sheet for a cylindrical battery housing, but also as a steel sheet for a battery housing for various secondary batteries.

[0036] Silicon (Si)

[0037] Silicon is used to increase the strength of the steel sheet by solid solution strengthening of the steel sheet, and is an effective element for spheroidizing cementite.

[0038] Silicon may be present in an amount of 0.001 wt % to 0.01 wt %, for example, 0.001 wt %, 0.002 wt %, 0.003 wt %, 0.004 wt %, 0.005 wt %, 0.006 wt %, 0.007 wt %, 0.008 wt %, 0.009 wt %, or 0.01 wt %, based on the total weight of the steel plate.

[0039] Within this range, silicon can increase the strength of the steel sheet, can maintain the corrosion resistance of the steel sheet without deteriorating the plating property of the steel sheet when the nickel plating layer is formed.

[0040] Manganese (Mn)

[0041] Manganese (Mn) is a solid strengthening element and is effective in improving the hardenability of the steel plate to ensure its strength.

[0042] Manganese (Mn) may be present in an amount of 0.05 wt % to 0.45 wt %, for example, 0.05 wt %, 0.06 wt %, 0.07 wt %, 0.08 wt %, 0.09 wt %, 0.1 wt %, 0.11 wt %, 0.12 wt %, 0.13 wt %, 0.14 wt %, 0.15 wt %, 0.16 wt %, 0.17 wt %, 0.18 wt %, 0.19 wt %, 0.2 wt %, 0.21 wt %, 0.22 wt %, 0.23 wt %, 0.24 wt %, 0.25 wt %, 0.26 wt %, 0.27 wt %, 0.28 wt %, 0.29 wt %, 0.30 wt %, 0.31 wt %, 0.32 wt %, 0.33 wt %, 0.34 wt %, 0.35 wt %, 0.36 wt %, 0.37 wt %, 0.38 wt %, 0.39 wt %, 0.40 wt %, 0.41 wt %, 0.42 wt %, 0.43 wt %, 0.44 %, 0.23wt%, 0.24wt%, 0.25wt%, 0.26wt%, 0.27wt%, 0.28wt%, 0.29wt%, 0.3wt%, 0.31wt%, 0.32wt%, 0.33wt%, 0.34wt%, 0.35wt%, 0.36wt%, 0.37wt%, 0.38wt%, 0.39wt%, 0.4wt%, 0.41wt%, 0.42wt%, 0.43wt%, 0.44wt%, or 0.45wt%. Preferably, manganese is present in an amount of 0.1wt% to 0.35wt% based on the total weight of the steel plate.

[0043] Within this range, manganese can improve the machinability of the steel sheet to facilitate the manufacture of a cylindrical battery case by a forming process, and allow the cylindrical battery case to reach a target strength even when the thickness of the cylindrical battery case is reduced after forming. In addition, the corrosion resistance of the steel sheet, such as in a battery, can be maintained, and the toughness of the low carbon steel can be prevented from being deteriorated by preventing the formation of inclusions and center segregation in the steel sheet.

[0044] Phosphorus (P)

[0045] Phosphorus is added to achieve hardening of the steel sheet and improvement of the corrosion resistance of the steel sheet.

[0046] Based on the total weight of the steel plate, the phosphorus may be present in an amount of 0.01 wt % to 0.02 wt %, for example, 0.01 wt %, 0.011 wt %, 0.012 wt %, 0.013 wt %, 0.014 wt %, 0.015 wt %, 0.016 wt %, 0.017 wt %, 0.018 wt %, 0.019 wt %, or 0.02 wt %. Preferably, based on the total weight of the steel plate, the phosphorus is present in an amount of 0.01 wt % to 0.015 wt %.

[0047] Within this range, phosphorus can maintain the corrosion resistance of the steel plate and harden the surface of the steel plate.

[0048] Sulfur (S)

[0049] Sulfur is an unavoidable impurity, and the content of sulfur must be limited because it reduces process efficiency by deteriorating the ductility of the steel sheet during hot working and by increasing the brittleness of the steel sheet when combining with manganese to form MnS precipitates.

[0050] Sulfur may be present in an amount of 0.01 wt % to 0.015 wt %, for example, 0.01 wt %, 0.011 wt %, 0.012 wt %, 0.013 wt %, 0.014 wt % or 0.015 wt %, based on the total weight of the steel plate. Within this sulfur range, brittle fracture during hot working can be prevented and machinability can be maintained.

[0051] Nitrogen (N)

[0052] Nitrogen present in a solid solution state in steel reduces the machinability of the steel sheet.

[0053] The upper limit of nitrogen is limited to 0.006 wt % or less, for example, 0.001 wt %, 0.002 wt %, 0.003 wt %, 0.004 wt %, 0.005 wt % or 0.006 wt % based on the total weight of the steel sheet. Within this range, nitrogen can prevent ductility degradation of the steel sheet due to aging.

[0054] Recrystallization Inhibiting Elements

[0055] Niobium (Nb)

[0056] Niobium (Nb) is added to low carbon steel to form carbides such as NbC, which can improve strength through grain boundary segregation caused by carbides while suppressing expansion of recrystallized texture due to formation of recrystallized grains at high temperature by increasing the recrystallization temperature.

[0057] Based on the total weight of the steel plate, niobium may be present in an amount of 0.01 wt% to 0.1 wt%, for example, 0.01 wt%, 0.02 wt%, 0.03 wt%, 0.04 wt%, 0.05 wt%, 0.06 wt%, 0.07 wt%, 0.08 wt%, 0.09 wt%, or 0.1 wt%. Preferably, niobium is present in an amount of 0.03 wt% to 0.05 wt% based on the total weight of the steel plate.

[0058] Within this range, niobium can increase the yield strength at room temperature while suppressing the formation of recrystallized grains at high temperatures, thereby improving the tensile strength of the steel sheet while achieving significant improvement in high temperature properties.

[0059] Molybdenum (Mo)

[0060] Molybdenum can improve the strength of the steel plate through solid solution strengthening, and can also improve the corrosion resistance and hardenability of the steel plate.

[0061] Based on the total weight of the steel plate, molybdenum (Mo) may be present in an amount of 0.05 wt % to 0.9 wt %, for example, 0.05 wt %, 0.06 wt %, 0.07 wt %, 0.08 wt %, 0.09 wt %, 0.1 wt %, 0.11 wt %, 0.12 wt %, 0.13 wt %, 0.14 wt %, 0.15 wt %, 0.16 wt %, 0.17 wt %, 0.18 wt %, 0.19 wt %, 0.2 wt %, 0.21 wt %, 0.22 wt %, or 0.23 wt %. t%, 0.23wt%, 0.24wt%, 0.25wt%, 0.26wt%, 0.27wt%, 0.28wt%, 0.29wt%, 0.3wt%, 0.31wt%, 0.32wt%, 0.33wt%, 0.34wt%, 0.35wt%, 0.36wt%, 0.37wt%, 038wt%, 0.39wt%, 0.4wt%, 0.41wt%, 0.42wt%, 0.43wt%, 0.44wt%, 0.45w t%, 0.46wt%, 0.47wt%, 0.48wt%, 0.49wt%, 0.5wt%, 0.51wt%, 0.52wt%, 0.53wt%, 0.54wt%, 0.55wt%, 0.56wt%, 0.57wt%, 0.58wt%, 0.59wt%, 0.6wt%, 0.61wt%, 0.62wt%, 0.63wt%, 0.64wt%, 0.65wt%, 0.66wt%, 0.67wt%, 0.68 %, 0.81wt%, 0.82wt%, 0.83wt%, 0.84wt%, 0.85wt%, 0.86wt%, 0.87wt%, 0.88wt%, 0.89wt% or 0.9wt%. Preferably, the molybdenum is present in an amount of 0.08wt% to 0.1wt% based on the total weight of the steel plate.

[0062] Within this range, molybdenum can prevent the generation of recrystallization texture by suppressing recrystallization of grains during heat treatment, and can suppress a decrease in yield strength at high temperatures, thereby achieving the effects of the present invention.

[0063] Boron (B)

[0064] Boron is a non-metallic element and is used to significantly improve the hardenability of low carbon steel. In addition, boron can be used as a precipitation hardening element and is also used to improve hardness and wear resistance.

[0065] Boron may be present in an amount of 0.001 wt % to 0.05 wt %, based on the total weight of the steel sheet, for example, 0.001 wt %, 0.002 wt %, 0.003 wt %, 0.004 wt %, 0.005 wt %, 0.006 wt %, 0.007 wt %, 0.008 wt %, 0.009 wt %, 0.01 wt %, 0.011 wt %, 0.012 wt %, 0.013 wt %, 0.014 wt %, 0.015 wt %, 0.016 wt %, 0.017 wt %, 0.018 wt %, 0.019 wt %, 0.02 wt %, 0.021 wt %, 0.022 wt %, 0.023 wt %, %. Preferably, boron is present in an amount of 0.01 wt % to 0.03 wt %, based on the total weight of the steel sheet.

[0066] Within this range, boron can improve the strength of the steel sheet and simultaneously prevent the generation of a recrystallization texture at a high temperature by increasing the recrystallization temperature, thereby achieving the effect of the present invention.

[0067] Steel sheets for battery housings

[0068] In one embodiment, a steel sheet for a battery case is manufactured with the above-mentioned composition of metal elements to achieve improved mechanical properties at a high temperature of 600°C.

[0069] The steel sheet for the battery case may include a base steel sheet including the above-mentioned metal elements, a heat diffusion layer (Fe—Ni), and a nickel (Ni) plating layer.

[0070] The steel sheet for a battery case may include niobium as a recrystallization inhibiting element, and may further include molybdenum, boron, or a combination thereof.

[0071] By controlling the composition system of metal elements in the steel sheet for battery cases and adding the above-mentioned kind of recrystallization inhibiting element thereto, it is possible to effectively prevent the generation of recrystallized texture at high temperatures of 600° C. or higher and improve the high temperature properties of the steel sheet for battery cases.

[0072] In one embodiment, the steel sheet for a battery case does not generate a recrystallized texture at a high temperature of 600° C. or higher and allows work hardening during rolling, thereby exhibiting not only high strength at room temperature but also high temperature properties in which high strength is ensured at high temperatures and elongation is not degraded at high temperatures.

[0073] In one embodiment, the steel plate for the battery case may have a thickness of 0.3 mm to 0.8 mm, for example, may have a thickness of 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, or 0.8 mm.

[0074] Within this thickness range, the steel sheet for a battery case can ensure strength while maintaining machinability, and can reduce the overall weight of the battery when applied to a cylindrical battery case.

[0075] In one embodiment, the steel sheet for the battery case may further include a nickel plating layer.

[0076] The steel sheet for the battery case may further include a nickel-plated layer on the cold-rolled steel strip including the metal element and the recrystallization inhibiting element. For example, the steel sheet may refer to a nickel-plated steel sheet (NPS) of a base steel sheet having a controlled composition system.

[0077] When the steel sheet used for the battery case is a nickel-plated steel sheet including a nickel-plated layer, the steel sheet has a lower degree of hardness increase due to work hardening after cylindrical battery case processing compared to a ferritic stainless steel sheet or an austenitic stainless steel sheet, and thus exhibits excellent formability, thereby improving the efficiency of the manufacturing process of the cylindrical battery case.

[0078] When the steel sheet for the battery case is a nickel-plated steel sheet, the steel sheet can ensure corrosion resistance and conductivity, and thus can be used not only as a cylindrical battery case but also as a battery case for various secondary batteries.

[0079] In one embodiment, the nickel plated layer may have a thickness of 0.1 μm to 6 μm, for example, 0.1 μm, 0.2 μm, 0.3 μm, 0.4 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, 1 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, A thickness of 2.8μm, 2.9μm, 3μm, 3.1μm, 3.2μm, 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm, 4μm, 4.1μm, 4.2μm, 4.3μm, 4.4μm, 4.5μm, 4.6μm, 4.7μm, 4.8μm, 4.9μm, 5μm, 5.1μm, 5.2μm, 5.3μm, 5.4μm, 5.5μm, 5.6μm, 5.7μm, 5.8μm, 5.9μm or 6μm.

[0080] Based on the total weight of the nickel plated layer, the nickel plated layer may include 50wt% or more of nickel, for example, may include 50wt%, 60wt%, 70wt%, 80wt% or 90wt% of nickel, and may have a thickness within the above range to ensure a sufficient heat dissipation layer while improving corrosion resistance.

[0081] The nickel layer can be heat diffused after plating.

[0082] For example, the nickel plating layer can be formed by electroplating the cold rolled steel sheet in a plating bath after pickling of the cold rolled steel sheet, and then performing alloying heat treatment and annealing to form a heat diffusion layer thereon. More specifically, the heat diffusion layer can be formed as a nickel-iron diffusion layer. The nickel-iron diffusion layer can be formed between the nickel plating layer and the base steel sheet.

[0083] Steel sheets used for battery housings can be work hardened.

[0084] The steel sheet for the battery case can be subjected to work hardening to a range in which a cylindrical battery case to be used for a cylindrical secondary battery can be manufactured without hardness deviation. For example, the degree of work hardening is controlled by cold rolling and annealing the NPS having a controlled composition system, whereby the cylindrical battery case can have a very uniform thickness in its outer diameter and inner diameter even after DI processing, and the parallelism of the opening can be maintained after trimming.

[0085] In one embodiment, the steel sheet for the battery case may have a tensile strength of 470 MPa or more and an elongation of 23% or more at room temperature. Specifically, the steel sheet for the battery case may have a tensile strength of 470 MPa to 490 MPa and an elongation of 23% to 25%.

[0086] The steel sheet for a battery case may exhibit tensile strength and elongation within the above ranges at room temperature of 25° C. by controlling the composition system of metal elements and recrystallization inhibiting elements.

[0087] The steel sheet for a battery case can be used as a battery case within the above range of properties at room temperature, and has improved machinability to allow thickness reduction, thereby enabling the manufacture of a large-diameter cylindrical battery case.

[0088] In one embodiment, the steel sheet for the battery case may have a tensile strength of 200 MPa or more at 500° C. Specifically, the steel sheet for the battery case may have a tensile strength of 200 MPa to 255 MPa at 500° C., and a tensile strength of 130 MPa to 170 MPa at 600° C.

[0089] By controlling the composition system of metal elements and adding recrystallization inhibiting elements, the steel sheet for the battery case not only exhibits high strength at room temperature, but also exhibits high-temperature properties in which high strength is ensured at high temperatures. For example, the steel sheet for the battery case can be manufactured by rolling, annealing and electroplating, and can be work-hardened during the mechanical processing of the battery case, thereby exhibiting not only excellent mechanical properties at room temperature, but also high-temperature properties in the temperature range of 500°C to 600°C, while ensuring the target tensile strength within the above range.

[0090] Even when the thickness of the steel sheet is reduced by 50% through a forming process (eg, DI process), the tensile strength of the steel sheet for a battery case at a temperature of 500 to 600° C. may be increased by about 2.7 times compared to a steel sheet without a recrystallization inhibiting element.

[0091] Since the steel sheet for the battery case can exhibit corrosion resistance by forming a nickel plating layer on a steel sheet having a controlled composition system of a metal element and a recrystallization inhibiting element, and can exhibit not only improved yield strength at room temperature but also high-temperature properties in which high tensile strength is ensured at high temperatures, the steel sheet for the battery case can be used for battery cases and cylindrical battery cases for EVs.

[0092] Battery housing

[0093] A battery case according to one embodiment is manufactured from the steel sheet for a battery case as described above.

[0094] In one embodiment, the battery case is manufactured into a cylindrical shape by deep drawing and deep drawing ironing (DI).

[0095] For example, the battery case may be manufactured by placing the NPS in a cylindrical can-shaped mold and then punching the NPS to simultaneously form the sidewall and the bottom, and may have an opening formed at the upper side thereof.

[0096] For austenitic or ferritic stainless steel, it is difficult to form a flanged portion or perform a clamping process due to increased rigidity through work hardening during DI processing, and separate heat treatment and annealing processes are required to form a side wall and a bottom having a uniform thickness.

[0097] By using a controlled composition system of metal elements and added recrystallization inhibiting elements, the steel sheet for battery housing according to the embodiment can exhibit increased strength and improved machinability even at room temperature, while limiting the increase in stiffness due to work hardening during DI processing, and can allow plastic deformation, making it very easy to manufacture cylindrical battery housings. In addition, the steel sheet for battery housing according to the embodiment limits the increase in residual stress due to hardness deviation even after machining, and therefore has the advantage of not requiring a separate annealing process.

[0098] In one embodiment, for example, when the steel sheet for the battery case has a thickness of 0.3 mm to 0.8 mm (e.g., 0.3 mm, 0.4 mm, 0.5 mm, 0.6 mm, 0.7 mm, or 0.8 mm), the battery case may have a thickness that is reduced by 50% or less by DI processing, and the side wall of the battery case may have a thickness of 0.15 mm to 0.4 mm.

[0099] The thickness of the battery case can be reduced by controlling the thickness within the above range through DI processing, and even when the thickness of the battery case is reduced to the above range, the battery case can maintain mechanical properties at room temperature, specifically, high temperature properties can be exhibited by significantly improving tensile strength even at high temperatures. In addition, the battery case is manufactured from a steel sheet for battery cases, so work hardening during DI processing is limited, thereby ensuring very high manufacturing efficiency.

[0100] The thickness reduction caused by the forming process reduces the thickness of the cylindrical case to increase the capacity of the battery by 10% or more while reducing the total weight of the battery by 30% or more, thereby enabling efficient manufacture of a cylindrical battery case having a large diameter of Φ46 or more.

[0101] In one embodiment, the tensile strength of the battery housing at room temperature may be 760 MPa or greater. Specifically, the tensile strength of the battery housing at room temperature may be 760 MPa to 780 MPa. Since the cylindrical battery housing can exhibit a tensile strength within the above range at room temperature even after DI processing, the cylindrical battery housing can be used in batteries for EVs that require high strength and high heat resistance, can effectively protect the monomer from various external impacts during driving at room temperature, and can effectively limit changes in the housing due to changes in the monomer.

[0102] In one embodiment, the tensile strength of the cylindrical battery case as measured at 500° C. may be 320 MPa or more, specifically, 320 MPa to 420 MPa, and the tensile strength of the cylindrical battery case as measured at 600° C. may be 240 MPa or more, specifically, 240 MPa to 280 MPa.

[0103] The battery case has increased strength, particularly at high temperatures ranging from 500° C. to 600° C., and thus can effectively prevent cracking of the side wall and the entire battery structure due to overheating or combustion in the cells.

[0104] In one embodiment, the sidewall rupture pressure of the battery case at room temperature may be 190 kgf / cm 2 or greater, specifically, 190 kgf / cm 2 Up to 210kgf / cm 2 .

[0105] Since the battery case is manufactured by DI processing the steel plate for battery case with improved room temperature properties and does not undergo work hardening during the DI processing, the battery case does not suffer from hardness deviation on its side walls and bottom, specifically, the side walls of the battery case have a uniform thickness, thereby ensuring a rupture pressure within the above range.

[0106] The cylindrical battery case may be used for a cylindrical secondary battery having a rupture pressure within the above range.

[0107] In one embodiment, the rupture pressure of the battery case at 600°C may be 100 kgf / cm 2 or more, specifically, 100 kgf / cm 2 Up to 130kgf / cm 2 .

[0108] Since no recrystallization texture is generated even at high temperatures, and recrystallization of grains is suppressed to prevent cracking between grains due to the addition of recrystallization inhibitory elements, the cylindrical battery case can have a rupture pressure within the above range even at a high temperature of 600°C. Compared with a battery case made of a typical cold-rolled steel sheet to which no recrystallization inhibitory elements are added, the battery case according to the present embodiment can show a rupture pressure increase of 20 kgf / cm at room temperature or high temperature (e.g., 600°C). 2 or more.

[0109] In one embodiment, the battery housing can maintain parallelism of the openings.

[0110] Since the cylindrical battery case allows easy plastic deformation during DI processing and does not suffer from hardness deviation due to work hardening, the cylindrical battery case can include side walls and a bottom with uniform thickness, especially side walls with very uniform thickness, and since the outer diameter, inner diameter and thickness of the cylindrical battery case do not change even after trimming the upper end of the cylindrical battery case after DI processing, the constant parallelism of the opening can be maintained.

[0111] In one embodiment, the cylindrical battery case does not suffer from side cracking due to PPR testing at 600°C.

[0112] The battery case has a controlled composition ratio of metal elements and recrystallization inhibiting elements, is manufactured into a cylindrical shape by DI processing, does not suffer from work hardening during machining, and limits the generation of recrystallization texture even at high temperatures of 500°C to 600°C to improve high-temperature properties including tensile strength, thereby enabling PPR response to temperature increases due to cell failures and fractures in EV-oriented battery modules or battery packs with a larger number of battery cells.

[0113] Cylindrical secondary battery

[0114] Figure 1 is a perspective view of a cylindrical secondary battery according to one embodiment of the present invention.

[0115] Reference Figure 1 According to one embodiment, a cylindrical secondary battery 100 includes an electrode assembly, a cylindrical battery case 110 configured to accommodate the electrode assembly and an electrolyte therein, a cap assembly 120 coupled to an opening of the cylindrical battery case 110 and sealing the cylindrical battery case 110, and an insulating plate built into the cylindrical battery case 110 between the electrode assembly and the cap assembly.

[0116] The electrode assembly may include a first electrode, a second electrode, and a separator interposed between the first electrode and the second electrode, and may be wound in a core shape.

[0117] The first electrode includes a first substrate and a first active material layer disposed on the first substrate. The first lead tab may extend outward from a first uncoated region of the first substrate where the first active material layer is not formed, and may be electrically connected to the cap assembly.

[0118] The second electrode includes a second substrate and a second active material layer disposed on the second substrate. The second lead tab may extend outward from a second uncoated region of the second substrate where the second active material layer is not formed, and may be electrically connected to the housing. The first lead tab and the second lead tab may extend in opposite directions to each other.

[0119] The first electrode may serve as a positive electrode. In this case, the first substrate may include, for example, aluminum foil, and the first active material layer may include, for example, a transition metal oxide. The second electrode may serve as a negative electrode. In this case, the second substrate may include, for example, copper foil or nickel foil, and the second active material layer may include, for example, graphite.

[0120] The separator is used to prevent the short circuit between the first electrode and the second electrode while allowing the migration of lithium ions. The separator may include, for example, a polyethylene film, a polypropylene film, a polyethylene-polypropylene film, and the like.

[0121] The cylindrical battery case 110 accommodates the electrode assembly and the electrolyte therein, and constitutes the exterior of the secondary battery together with the cap assembly 120. The cylindrical battery case 110 may include a side wall having a substantially cylindrical shape and a bottom connected to one side of the side wall. The side wall may include a curling portion deformed inwardly, and may be provided with a crimping portion bent inwardly at its open end.

[0122] The crimping portion can inhibit movement of the electrode assembly within the case while facilitating placement of the gasket and cap assembly. The crimping portion can securely hold the cap assembly in place by pressing the edge of the cap assembly 120 via the gasket. The case can be formed of, for example, nickel-plated steel.

[0123] The cap assembly 120 may be fixed to the inside of the crimping portion via a gasket to seal the case.The cap assembly may include an upper cap, a safety vent, a lower cap, an insulating member, and a sub-board, and may be modified in various ways without being limited thereto.

[0124] The upper cover may be placed at the uppermost side of the cap assembly. The upper cover may include a terminal protruding upward in a convex shape to be connected to an external circuit, and an exhaust port formed around the terminal and configured to exhaust gas.

[0125] The safety vent hole may be placed under the upper cover. The safety vent hole may include a protrusion protruding downward in a convex shape and connected to the sub-board and at least one notch placed around the protrusion.

[0126] When gas is generated, for example, due to overcharging or abnormal operation of the battery, the protrusion can be deformed upward under pressure to separate from the sub-plate, and a safety vent can be cut along the notch. The cut safety vent allows gas to be discharged to the outside, thereby preventing the explosion of the secondary battery.

[0127] The lower cover may be placed below the safety vent. The lower cover may include a first opening to expose the protrusion of the safety vent and a second opening for exhausting gas. An insulating member may be placed between the safety vent and the lower cover to insulate the safety vent from the lower cover.

[0128] The sub-plate may be placed downwardly below the lower cover. The sub-plate may be fixed to the lower surface of the lower cover to block the first opening of the lower cover, and the protrusion of the safety vent may be fixed to the sub-plate. The first lead tab extracted from the electrode assembly may be fixed to the sub-plate. Thus, the upper cover, the safety vent, the lower cover, and the sub-plate may be electrically connected to the first electrode of the electrode assembly.

[0129] The insulating plate may be disposed below the curling portion to abut against the electrode assembly, and may be provided with a tab opening for withdrawing the first lead tab. The cap assembly electrically connected to the first electrode through the first lead tab may face the electrode assembly, and the insulating plate may be disposed between the cap assembly and the electrode assembly, and the cap assembly may be insulated from the electrode assembly by the insulating plate.

[0130] The cylindrical secondary battery according to the embodiment can achieve improved capacity and reduced weight by improving room temperature properties to allow the thickness of the cylindrical battery case to be reduced, allowing PPR response at high temperatures of 500°C or higher by improving high temperature properties, and can be manufactured as a large-diameter battery with a diameter of Φ46 or more.

[0131] Prismatic battery

[0132] Figure 2 is a perspective view of a prismatic battery according to one embodiment of the present invention.

[0133] Reference Figure 2 , the prismatic battery 200 according to the present embodiment includes a case 210 formed of a steel plate for a battery case according to an embodiment of the invention.

[0134] Specifically, the prismatic battery may include at least one electrode assembly wound with a separator as an insulator interposed between positive and negative electrodes, a case 210 accommodating the electrode assembly therein, and a cap assembly coupled to an opening of the case 210 .

[0135] As a prismatic battery 200 according to an embodiment of the present invention, a prismatic lithium-ion secondary battery will be described below as an example. However, it should be understood that the present invention is not limited thereto and can be applied to various batteries, such as lithium polymer batteries, cylindrical batteries, etc.

[0136] Each of the positive electrode and the negative electrode may include a coated region, which refers to a region where an active material is applied to a current collector formed of a thin sheet of metal foil, and an uncoated region, which refers to a region where the active material is not applied.

[0137] The positive electrode and the negative electrode are wound after placing a separator as an insulator between the positive electrode and the negative electrode. However, it should be understood that the present invention is not limited thereto, and the electrode assembly may also include a plurality of positive and negative electrode sheets alternately stacked with a separator therebetween.

[0138] The case constitutes the overall appearance of the secondary battery and may be formed of a conductive metal such as aluminum, an aluminum alloy, or nickel-plated steel. The case may also provide a space in which the electrode assembly is accommodated.

[0139] The cap assembly may include a cap plate covering the opening of the case, wherein the case and the cap plate may be formed of a conductive material. Here, a positive terminal and a negative terminal electrically connected to the positive electrode and the negative electrode, respectively, may protrude outward through the cap plate.

[0140] In addition, the outer peripheral surfaces of the upper posts of the positive terminal and the negative terminal protruding outward through the cover plate may be threaded and fixed to the cover plate with nuts.

[0141] However, it should be understood that the present invention is not limited thereto, and the positive terminal and the negative terminal may have a riveting structure to be riveted to the cap plate or may be welded to the cap plate.

[0142] Furthermore, the cover plate may be a thin plate to be bonded to the opening of the case, and may be formed with an electrolyte inlet to which a sealing stopper may be provided, and a vent of the recess may be provided to the cover plate.

[0143] The positive and negative terminals may be electrically connected to current collectors including first and second current collectors (hereinafter, respectively referred to as positive and negative current collectors) welded to the positive and negative uncoated regions, respectively.

[0144] For example, the positive terminal and the negative terminal may be welded to the positive current collector and the negative current collector, respectively. However, it should be understood that the present invention is not limited thereto, and the positive terminal and the negative terminal may be integrally formed with the positive current collector and the negative current collector.

[0145] In addition, the insulating member may be disposed between the electrode assembly and the cap plate. The insulating member may include a first lower insulating member and a second lower insulating member, both of which are disposed between the electrode assembly and the cap plate.

[0146] According to the embodiment, one end of the separation member facing one side surface of the electrode assembly may be disposed between the insulation member and the positive electrode terminal or the negative electrode terminal.

[0147] The separation member may include a first separation member and a second separation member.

[0148] Therefore, one end of each of the first and second separation members that may be disposed to face one side surface of the electrode assembly may be disposed between the first lower insulating member and the positive terminal and between the second lower insulating member and the negative terminal, respectively.

[0149] As a result, the positive and negative electrode terminals welded to the positive and negative current collectors, respectively, may be coupled to corresponding ends of the first and second lower insulating members and the first and second separation members, respectively.

[0150] Next, the present invention will be described in more detail with reference to some examples. It should be understood that these examples are provided for illustration only and should not be interpreted as limiting the invention in any way.

[0151] Example: Composition system of metallic elements and recrystallization inhibitory elements

[0152] The amounts of the metal elements and the recrystallization inhibiting elements are adjusted so as to improve not only the texture properties of the steel sheet at room temperature but also the texture properties of the steel sheet at high temperatures by inhibiting the formation of a recrystallization texture.

[0153] Based on low carbon steel containing 0.03 wt % of carbon (C) according to Table 1 (Comparative Example 1; Reference), a slab having a controlled steel composition system was nickel plated in a nickel bath and annealed at 800° C. or less, thereby finally preparing a steel sheet for a battery case.

[0154] Properties at room and elevated temperatures

[0155] In order to examine whether the steel sheet according to the example can be used as a battery case, the tensile strength and elongation of the samples prepared according to Table 1 at room temperature and high temperature were measured using a universal material testing machine.

[0156] A tensile strength of 470 MPa or more and an elongation of 23% or more at room temperature (25°C) were set as target properties, and a tensile strength of 200 MPa or more at 500°C and a tensile strength of 130 MPa at 600°C were set as target properties to examine whether the target values ​​could be achieved.

[0157] Table 1

[0158]

[0159]

[0160] Referring to Table 1, the samples of Comparative Example 1 and Comparative Example 2 are low carbon steels conventionally used for battery cases, do not include the recrystallization inhibitory element according to the present invention, and have a tensile strength of 419.5 MPa to 422.6 MPa at room temperature, an elongation of 23.6% to 26% at room temperature, a tensile strength of 177 MPa at 500°C, and a tensile strength of 99.6 MPa to 111.1 MPa at 600°C, indicating that the target high temperature properties cannot be achieved.

[0161] Although the carbon content was insufficient, the sample of Comparative Example 3 could ensure room temperature properties by adding niobium. However, the tensile strength of this sample was 161 MPa at 500°C and 119.3 MPa at 600°C, indicating that the targeted high temperature properties could not be achieved.

[0162] Despite the addition of boron, the sample of Comparative Example 4 had a tensile strength of 167.8 MPa at 500° C. and a tensile strength of 119 MPa at 600° C., indicating that the targeted high temperature properties could not be achieved.

[0163] When the carbon content according to the examples was not ensured, it was confirmed that the targeted high temperature properties could not be achieved even by adding an additional recrystallization inhibiting element.

[0164] On the other hand, it is examined whether the targeted room temperature properties and high temperature properties can be achieved according to the combination of recrystallized elements.

[0165] In Experimental Examples 1 and 2 in which only boron was added, the samples failed to achieve the target tensile strength at room temperature, and it was confirmed that the tensile strength of the samples at room temperature was 411 MPa to 415.7 MPa, the tensile strength at 500°C was 172.7 MPa to 174.6 MPa, and the tensile strength at 600°C was 99.6 MPa to 101 MPa, indicating that the target high temperature properties cannot be achieved when recrystallization inhibiting elements including niobium are not added.

[0166] In Example 1 in which niobium is added, the sample has a tensile strength of 472.6 MPa or more at room temperature, an elongation of 24.8% or more at room temperature, a tensile strength of 209 MPa or more at 500°C, and a tensile strength of 135.3 MPa or more at 600°C, indicating that the targeted room temperature / high temperature properties can be achieved.

[0167] In Example 2 where molybdenum is added, the sample has a tensile strength of 485.6 MPa or greater at room temperature, an elongation of 23% or greater at room temperature, a tensile strength of 250.8 MPa or greater at 500°C, and a tensile strength of 168.6 MPa or greater at 600°C, indicating that the targeted room temperature / high temperature properties can be achieved.

[0168] Specifically, it was confirmed that when the molybdenum content increased, the tensile strength at room temperature increased to 485 MPa or more, indicating that the tensile strength at room temperature was improved.

[0169] In Example 3 in which niobium and boron are added, the sample has a tensile strength of 472.3 MPa or greater at room temperature, an elongation of 23.7% or greater at room temperature, a tensile strength of 219.2 MPa or greater at 500°C, and a tensile strength of 138.4 MPa or greater at 600°C, indicating that the targeted room temperature / high temperature properties can be achieved.

[0170] In Example 4, in which niobium, molybdenum, and boron were added as recrystallization inhibiting elements, the sample had a tensile strength of 485.1 MPa or more at room temperature, an elongation of 23.3% or more at room temperature, a tensile strength of 251.8 MPa or more at 500°C, and a tensile strength of 158.5 MPa or more at 600°C, indicating that the targeted room temperature / high temperature properties can be achieved.

[0171] Therefore, it can be seen that the steel sheet according to the embodiment can be used as a battery case, specifically, as a cylindrical battery case, by controlling the carbon content of low carbon steel while adding a recrystallization inhibiting element to achieve targeted room temperature / high temperature properties.

[0172] Properties of Cylindrical Battery Cases

[0173] In order to simulate a cylindrical battery case having a side wall subjected to a 50% thickness thinning drawing by a DI process, a steel sheet prepared according to the following Table 2 was subjected to cold rolling at a reduction rate of 50%.

[0174] Table 2

[0175]

[0176]

[0177] Table 2 shows changes in room temperature / high temperature properties of a steel sheet for a battery case after cold rolling according to the addition of a recrystallization inhibiting element.

[0178] It can be seen that the samples of Experimental Examples 4 to 6 show significant improvement in high temperature properties by improving tensile strength at room temperature and high temperature compared to the sample of Experimental Example 3 without adding a recrystallization inhibitory element. Specifically, at a high temperature of 600°C or higher, the tensile strength of the sample of Experimental Example 6 is about 2.7 times that of the sample of Experimental Example 3, indicating that the high temperature properties after rolling are significantly improved. Therefore, it is confirmed that the steel sheet according to the embodiment can reduce the thickness of the battery case while ensuring high temperature properties.

[0179] Bursting pressure of sidewall

[0180] For the PPR response, the rupture pressure of the cylindrical battery casing is measured.

[0181] Figure 3 is a graph showing the results of a room temperature rupture pressure test of a battery case according to one embodiment of the present invention, Figure 4 is a graph showing the results of a burst pressure test of a battery case according to one embodiment of the present invention after heating at 600° C. for 10 minutes.

[0182] Reference Figure 3 , the rupture pressure test was repeated five times at room temperature without heat being applied to the cylindrical battery case to determine the rupture pressure of the side wall of the cylindrical battery case according to the embodiment.

[0183] Table 3

[0184] Serial number Experimental Example 3 Experimental Example 4 Experimental Example 5 Experimental Example 6 1 189.7 181.5 171.3 203.9 2 184.6 202.9 200.9 200.9 3 184.6 186.6 198.8 206.0 4 179.5 - 202.9 - 5 178.5 - - - <![CDATA[Average value (kgf / cm 2 )]]> 183.3 190.3 193.5 203.6

[0185] Table 3 shows the results of the burst pressure test at room temperature.

[0186] The samples of Experimental Examples 4 to 6 satisfying the composition according to the embodiment have an average rupture pressure higher than that of the sample of Experimental Example 3 as a typical cold-rolled steel sheet. Specifically, it was confirmed that the average rupture pressure of the sample of Experimental Example 6 was 20 kgf / cm greater than that of the sample of Experimental Example 3. 2 or more.

[0187] To measure the rupture pressure at high temperature, the cylindrical battery case was heated at 600° C. for 10 minutes, and then the rupture pressure was measured again.

[0188] Table 4

[0189] Serial number Experimental Example 3 Experimental Example 4 Experimental Example 5 Experimental Example 6 1 98.9 119.3 - 109.1 2 93.8 99.9 122.4 121.3 3 97.9 108.1 108.1 125.4 <![CDATA[Average value (kgf / cm 2 )]]> 96.9 109.1 115.2 118.6

[0190] Table 4 shows the results of the burst pressure test of the cylindrical battery casing after heating to 600°C.

[0191] Reference Figure 44, it is confirmed that the cylindrical battery cases of Experimental Examples 4 to 6 satisfying the composition according to the embodiment have high rupture pressure even at high temperatures. Specifically, the average rupture pressure of the cylindrical battery case of Experimental Example 6 is 22 kgf / cm greater than the average rupture pressure of the sample of Experimental Example 3. 2 or more.

[0192] PPR Performance

[0193] Passive Propagation Resistance (PPR) testing is performed to evaluate the extent of propagation to adjacent cells due to thermal runaway of an ignited cell (initiator) in an EV / ESS (Energy Storage System) that uses a large number of cylindrical cells to form a battery module.

[0194] A 6 Ah cylindrical battery cell was prepared using a cylindrical can having a thickness of 0.15 t (0.15 mm) formed by rolling the steel sheet of Example 2 at a reduction ratio of 50%.

[0195] A cylindrical battery cell having the same capacity was prepared by forming a cylindrical can having a thickness of 0.25 t (0.25 mm) from the steel plate of Comparative Example 1.

[0196] As shown in Table 5, the PPR test was performed by bringing a 30 W heating coil into contact with the upper and lower surfaces of a cylindrical battery cell while varying the applied power to examine side cracks of the battery case.

[0197] Table 5

[0198] Applied power 30W 33W 45W 60W 70W 90W Example 2 (0.15t) OK OK OK OK OK NG Comparative Example 1 (0.25t) OK OK OK OK NG NG

[0199] Table 5 shows the side fracture according to the amount of applied power. Referring to Table 5, although the steel sheet of Example 2 was fractured at the lower bead of the cylindrical battery case even by applying a power of 60 W, the steel sheet of Example 2 did not suffer from the side fracture.

[0200] Although the steel sheet of Example 2 had a further reduced thickness compared to the steel sheet of Comparative Example 1, it was confirmed that the cylindrical battery cell of Example 2 exhibited the same level of strength as that of the cylindrical battery cell of Comparative Example 1.

[0201] It has been confirmed that the cylindrical battery cells manufactured using the steel sheet for battery case according to the embodiment do not suffer side cracking even when a high power of 60W is applied in the PPR test, and have the same level of PPR performance as typical cylindrical batteries manufactured using a steel sheet having a thickness of 0.25t or more.

[0202] In this way, the steel sheet for the battery case according to the embodiment can not only achieve high strength at room temperature, but also ensure significant improvement in high temperature properties (high strength at high temperatures of 500°C or higher is ensured) by adjusting the composition system of metal elements and the amount of niobium, molybdenum and boron among the recrystallization inhibiting elements, and allow the thickness to be reduced by improving the yield strength at room temperature, so as to allow the manufacture of large-diameter cylindrical batteries with a diameter of Φ46 or more, thereby achieving significant improvement in single cell capacity. Specifically, the cylindrical battery case manufactured by DI processing of the steel sheet for the battery case according to the embodiment exhibits improved high temperature properties and can effectively suppress side cracking, thereby enabling PPR response in the manufacture of batteries for EVs.

[0203] Although the present invention has been described with reference to some embodiments and drawings, the present invention is not limited thereto. Various modifications and changes may be made by those skilled in the art within the technical spirit of the present invention and the scope of the claims and their equivalents.

[0204] <Reference Signs List>

[0205] 100: Cylindrical secondary battery

[0206] 110: Cylindrical battery case

[0207] 120: Cover assembly

[0208] 200: Prismatic battery

[0209] 210: Shell.

Claims

1. A steel plate for a battery housing, the steel plate comprising a matrix steel plate, the matrix steel plate comprising: 0.02wt% to 0.08wt% carbon; 0.01wt% to 0.1wt% niobium; and the balance of iron.

2. The steel plate for a battery case according to claim 1, further comprising: 0.05wt% to 0.9wt% molybdenum.

3. The steel plate for a battery case according to claim 1, further comprising: 0.001 wt% to 0.05 wt% boron.

4. The steel plate for a battery case according to claim 1, further comprising: 0.05wt% to 0.9wt% molybdenum and 0.001wt% to 0.05wt% boron.

5. The steel plate for a battery case according to claim 1, further comprising: 0.001 wt % to 0.01 wt % silicon; 0.05 wt % to 0.45 wt % manganese; 0.010 wt% to 0.020 wt% of phosphorus; 0.010 wt% to 0.015 wt% of sulfur; and 0.006 wt% or less of nitrogen.

6. The steel sheet for a battery case according to claim 1, wherein: The steel sheet has no recrystallization texture at a temperature of 600° C. or higher.

7. The steel sheet for a battery case according to claim 1, wherein: The thickness of the steel plate is 0.3 mm to 0.8 mm.

8. The steel plate for a battery case according to claim 1, further comprising: A nickel layer is plated on the substrate steel plate.

9. The steel sheet for a battery case according to claim 8, wherein: The thickness of the nickel plating layer is 0.1 μm to 6 μm.

10. The steel sheet for a battery case according to claim 8, wherein: A heat diffusion layer is formed between the nickel plating layer and the base steel plate.

11. The steel sheet for a battery case according to claim 1, wherein: The steel plate has a tensile strength of 470 MPa or more at room temperature and an elongation of 23% or more at room temperature.

12. The steel sheet for a battery case according to claim 1, wherein: The steel sheet has a tensile strength of 200 MPa or more at 500°C.

13. The steel sheet for a battery case according to claim 1, wherein: The steel sheet has a tensile strength of 130 MPa or more at 600°C. 14 . A battery case, which is manufactured from the steel plate for a battery case according to claim 1 and is provided with an opening.

15. The battery casing according to claim 14, wherein: The battery case has a thickness reduced by 50% or less by forming.

16. The battery casing according to claim 14, wherein: The battery case has a tensile strength of 760 MPa or more at room temperature.

17. The battery casing according to claim 14, wherein: The battery case has a tensile strength of 320 MPa or more at 500° C. and a tensile strength of 240 MPa or more at 600° C.

18. The battery casing according to claim 14, wherein: The side wall rupture pressure of the battery case at room temperature is 190 kgf / cm 2 or larger.

19. The battery casing according to claim 14, wherein: The side wall rupture pressure of the battery case at 600°C is 100 kgf / cm 2 or larger.

20. A cylindrical secondary battery, comprising: A cylindrical housing made of the steel sheet for a battery housing according to claim 1; a cover assembly, sealing the cylindrical housing; as well as The electrode assembly is arranged inside the cylindrical shell.

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