Improved safety of prismatic secondary batteries

Abstract

The disclosed invention relates to a rectangular secondary battery, and in one example, includes a case having at least one side forming an open surface, an electrode assembly housed inside the case via the open surface of the case, and a cap plate which is coupled to the open surface of the case to seal it and has positive and negative electrode terminals, and a first concave beading processing portion is formed on at least two opposing surfaces along the front, rear, left and right edges of the case.

Description

[Technical Field]

[0001] The present invention relates to a prismatic secondary battery having improved safety by preventing internal slippage of an electrode assembly.

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0085230, filed on July 11, 2022, and all contents disclosed in the documents of said Korean patent application are incorporated herein by reference. [Background technology]

[0003] Unlike primary batteries, secondary batteries are rechargeable and have the potential to be small and have large capacities, and as such, they have been the subject of much research and development in recent years. Demand for secondary batteries as an energy source is rapidly increasing due to the increasing technological development and demand for mobile devices, as well as the emergence of electric vehicles and energy storage systems in response to modern demands for environmental protection.

[0004] Secondary batteries are classified into coin-type batteries, cylindrical batteries, prismatic batteries, and pouch-type batteries depending on the shape of the battery case. The electrode assembly installed inside the battery case of a secondary battery is a power generating element that can be charged and discharged and is made up of a laminated structure of electrodes and a separator.

[0005] Electrode assemblies can be broadly classified into a jellyroll type in which a sheet-like positive electrode and negative electrode coated with an active material are wound up with a separator interposed between them; a stack type in which multiple positive electrodes and negative electrodes are stacked in sequence with a separator interposed between them; and a stack and folding type in which stack-type unit cells are wound up with a long separator film.

[0006] The positive and negative electrode tabs of the electrode assembly housed in a prismatic secondary battery are joined to electrode leads, respectively, and then connected to the positive and negative terminals on the case. The case housing the electrode assembly has some extra space for electrical connection of the electrode assembly and for the required amount of electrolyte. Therefore, the electrode assembly inside the case may shake or slip due to external impact. In particular, prismatic secondary batteries used in hybrid and electric vehicles frequently slip due to impacts while driving.

[0007] The electrode assembly's structural support is primarily provided by the positive and negative electrode tabs (electrode tabs) connected to the positive and negative terminals. Therefore, if slippage occurs in the electrode assembly, various problems can occur, such as short circuits due to electrical contact or tearing of the electrode tabs due to stress being concentrated on them. Furthermore, such tab damage can reduce the capacity of the secondary battery and cause imbalances among the multiple batteries housed in the battery pack, resulting in reduced battery life and stability issues. [Prior art documents] [Patent documents]

[0008] [Patent Document 1] Korean Patent Publication No. 2005-0046592 Summary of the Invention [Problem to be solved by the invention]

[0009] SUMMARY OF THE INVENTION An object of the present invention is to prevent an electrode assembly housed inside a prismatic secondary battery from slipping during use.

[0010] However, the technical problems that the present invention aims to solve are not limited to the above-mentioned problems, and other problems not mentioned will be clearly understood by those skilled in the art from the description of the invention described below. [Means for solving the problem]

[0011] The present invention relates to a prismatic secondary battery, which in one example includes a case having at least one surface forming an open surface, an electrode assembly housed inside the case via the open surface of the case, and a cap plate that is coupled to the open surface of the case so as to seal it and has positive and negative electrode terminals, and a first concave beading processing portion is formed on at least two opposing surfaces along the front, rear, left, and right edges of the case.

[0012] The first beading processing portion presses the surface of the electrode assembly housed inside the case.

[0013] In particular, the first beading processing portion may press the negative electrode surface of the electrode assembly housed inside the case, and the negative electrode surface of the electrode assembly covers the positive electrode surface, preventing the positive electrode surface from being exposed.

[0014] The first beading processed portion is formed at a position spaced apart from the electrode tab of the electrode assembly housed inside the case.

[0015] The first beading processing portion may be formed adjacent to the cap plate to press an upper portion of the electrode assembly housed inside the case.

[0016] In one embodiment of the present invention, the first beading processed portion may be formed on the front and rear edges of the case that have the longest widthwise lengths.

[0017] Alternatively, the first beading processed portion may be formed continuously on all four sides along the front, rear, left and right edges of the case.

[0018] According to another embodiment of the present invention, the case may further include second beading processed portions formed on at least two opposing surfaces along the front, rear, left, and right edges at a height adjacent to the bottom surface of the case.

[0019] The second beading processing portion supports the lower portion of the electrode assembly housed inside the case, and the second beading processing portion may contact and support the bottom surface of the electrode assembly without pressing against the surface of the electrode assembly housed inside the case.

[0020] The second beading processed portion may be formed on the front and rear surfaces of the case that have the longest widthwise length among the front, rear, left, and right edges, or may be formed continuously on all four sides along the front, rear, left, and right edges of the case. [Effects of the Invention]

[0021] In the prismatic secondary battery of the present invention having the above-described configuration, the recessed beading portion formed on the case presses against and fixes the surface of the electrode assembly, thereby improving the support structure of the electrode assembly and suppressing slippage during use, thereby preventing various problems such as short circuits due to electrical contact and broken tabs, thereby significantly improving the safety of the secondary battery.

[0022] However, the technical effects that can be obtained by the present invention are not limited to the effects described above, and other effects not mentioned will be clearly understood by those skilled in the art from the description of the invention described below.

[0023] The following drawings attached to this specification illustrate preferred embodiments of the present invention and, together with the detailed description of the invention described below, serve to further understand the technical concept of the present invention, and therefore the present invention should not be interpreted as being limited solely to the matters depicted in such drawings. [Brief explanation of the drawings]

[0024] [Figure 1] 1 is a view illustrating the outer shape of a prismatic secondary battery according to an embodiment of the present invention; [Figure 2] 2 is a cross-sectional view of the prismatic secondary battery of FIG. 1 taken along line "AA." [Figure 3] 1 is a view illustrating the front surface of a prismatic secondary battery; [Figure 4] 10 is a view illustrating another embodiment of the first beading processing unit. [Figure 5] 10 is a view illustrating the outer shape of a prismatic secondary battery according to another embodiment of the present invention. [Figure 6] 6 is a cross-sectional view of the prismatic secondary battery of FIG. 5 taken along line "BB." [Figure 7] 10 is a view illustrating another embodiment of the second beading processing unit. DETAILED DESCRIPTION OF THE INVENTION

[0025] Because the present invention can be modified in various ways and can have various embodiments, specific embodiments will be described in detail below.

[0026] However, this is not intended to limit the invention to any particular embodiment, but should be understood to include all modifications, equivalents, or alternatives falling within the spirit and scope of the invention.

[0027] In the present invention, the terms "comprise" and "have" are intended to specify the presence of features, numbers, steps, operations, components, parts or combinations thereof described in the specification, and should be understood as not precluding the presence or possibility of addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0028] Furthermore, in the present invention, when a layer, film, region, plate, or other portion is described as being "on" another portion, this includes not only the case where it is "directly on" the other portion, but also the case where there is another portion therebetween. Conversely, when a layer, film, region, plate, or other portion is described as being "under" the other portion, this includes not only the case where it is "directly under" the other portion, but also the case where there is another portion therebetween. Furthermore, in this application, being "located on" can include not only the case where it is located at the top, but also the case where it is located at the bottom.

[0029] The present invention relates to a prismatic secondary battery, which in one example includes a case having at least one surface forming an open surface, an electrode assembly housed inside the case via the open surface of the case, and a cap plate that is coupled to the open surface of the case so as to seal it and has positive and negative electrode terminals, and a first concave beading processing portion is formed on at least two opposing surfaces along the front, rear, left, and right edges of the case.

[0030] Here, the first beading processed portion formed in a concave shape toward the inside of the case presses the surface of the electrode assembly housed inside the case.

[0031] As described above, in the prismatic secondary battery of the present invention, the recessed beading portion formed on the case presses against and fixes the surface of the electrode assembly, thereby improving the support structure of the electrode assembly and suppressing slippage during use, thereby preventing various problems such as short circuits due to electrical contact and broken tabs, thereby significantly improving the safety of the secondary battery.

[0032] Hereinafter, specific embodiments of the prismatic secondary battery of the present invention will be described in detail with reference to the accompanying drawings. For reference, directions such as front-back, up-down, left-right, and the like that indicate relative positions used in the following description are intended to facilitate understanding of the invention, and unless otherwise specified, are based on the directions shown in the drawings.

[0033] (First embodiment) FIG. 1 is a view illustrating the outer shape of a prismatic secondary battery 10 according to a first embodiment of the present invention, and FIG. 2 is a cross-sectional view of the prismatic secondary battery 10 of FIG. 1 taken along line AA.

[0034] The prismatic secondary battery 10 of the first embodiment includes a case 100 having at least one open surface, and an electrode assembly 300 housed inside the case 100 via the open surface of the case 100. The battery also includes a cap plate 200 that is coupled to the open surface of the case 100 to seal the open surface and has positive and negative electrode terminals 210.

[0035] The prismatic secondary battery 10 of the first embodiment shown in FIG. 1 is a one-way secondary battery in which positive and negative electrode terminals 210 are both arranged on the top surface of the case 100, and the open surface of the case 100 is the top surface, so that the cap plate 200 seals the top surface of the case 100.

[0036] The electrode assembly 300, in which the unit cells are stacked, is sealed and housed in the case 100. A unit cell is a cell having a unit structure of an anode 310, a separator 320, and a cathode 330, and a plurality of unit cells are stacked to form one electrode assembly 300. The general structure of a unit cell is as follows.

[0037] The positive electrode 330 includes a positive electrode current collector and a positive electrode active material coated on one or both sides of the positive electrode current collector. One widthwise end of the positive electrode current collector has a blank area where the positive electrode active material is not coated. The blank area is notched (punched) to form a positive electrode tab 344.

[0038] The negative electrode 310 includes a negative electrode current collector and a negative electrode active material coated on one or both sides of the negative electrode current collector. One widthwise edge of the negative electrode current collector has a non-coated portion where the negative electrode active material is not coated. Similarly, the non-coated portion of the negative electrode 310 functions as a negative electrode tab 342.

[0039] In the first embodiment, the electrode tabs 340, i.e., the positive electrode tab 344 and the negative electrode tab 342, are located at the same end along the width direction of the electrode assembly 300, i.e., along the height direction of the prismatic secondary battery 10. In the illustrated example, the positive electrode tab 344 and the negative electrode tab 342 extend toward the upper surface of the prismatic secondary battery 10, and the positive electrode tab 344 and the negative electrode tab 342 are electrically connected to the positive electrode terminal and the negative electrode terminal, respectively, provided on the cap plate 200.

[0040] In the present invention, the positive electrode active material coated on the positive electrode current collector and the negative electrode active material coated on the negative electrode current collector may be any active material known in the art without any limitation.

[0041] In one example, the positive electrode active material has the general chemical formula A[A x M y ]O 2+z (A includes at least one element selected from Li, Na, and K; M includes at least one element selected from Ni, Co, Mn, Ca, Mg, Al, Ti, Si, Fe, Mo, V, Zr, Zn, Cu, Sc, Ru, and Cr; x≧0, 1≦x+y≦2, 0.1≦z≦2; and the stoichiometric coefficients of x, y, z, and the components in M ​​are selected so that the compound maintains electroneutrality).

[0042] In another example, the positive electrode active material is an alkali metal compound xLiM disclosed in US Pat. No. 6,677,082, US Pat. No. 6,680,143, etc. 1 O2(1x)Li2M 2 O3(M 1 contains at least one element having an average oxidation state of 3; M 2 x may be 0≦x≦1) where x is an integer of 0 to 10 and x is an integer of 1 to 10.

[0043] In another example, the positive electrode active material has the general chemical formula Li a M 1 x Fe 1x M 2 y P 1y M 3 z O 4z (M 1 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Mg and Al; M 2 contains at least one element selected from Ti, Si, Mn, Co, Fe, V, Cr, Mo, Ni, Nd, Mg, Al, As, Sb, Si, Ge, V and S; M 3contains halogen elements, optionally including F; <a≦2、0≦x≦1、0≦y<1、0≦z<1;a、x、y、z、M 1 , M 2 and M 3 wherein the stoichiometric coefficients of the components in are selected to maintain electroneutrality of the compound), or lithium metal phosphate, represented by Li3M2(PO4)3, where M comprises at least one element selected from Ti, Si, Mn, Fe, Co, V, Cr, Mo, Ni, Mg, and Al.

[0044] Preferably, the positive electrode active material may contain primary particles and / or secondary particles formed by aggregation of primary particles.

[0045] For example, the negative electrode active material may be a carbon material, lithium metal or a lithium metal compound, silicon or a silicon compound, or tin or a tin compound. Metal oxides with a potential of less than 2 V, such as TiO2 and SnO2, may also be used as the negative electrode active material. The carbon material may be either low-crystalline carbon or high-crystalline carbon.

[0046] The separator 320 interposed between the positive electrode 330 and the negative electrode 310 may be a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, an ethylene / methacrylate copolymer, etc., or a laminate of these. As another example, the separator 320 may be made of a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, polyethylene terephthalate fiber, etc.

[0047] At least one surface of the separator 320 may include a coating layer of inorganic particles. Alternatively, the separator 320 itself may be made of a coating layer of inorganic particles. The particles constituting the coating layer may have a structure in which they are bound with a binder so that interstitial volumes exist between adjacent particles.

[0048] The inorganic particles may be made of an inorganic material having a dielectric constant of 5 or more. Non-limiting examples of the inorganic particles include Pb(Zr,Ti)O3 (PZT), Pb 1x La x Zr 1y Ti y O3(PLZT), PB(Mg3Nb 2 / 3 )O3PbTiO3 (PMNPT), BaTiO3, hafnia (HfO2), SrTiO3, TiO2, Al2O3, ZrO2, SnO2, CeO2, MgO, CaO, ZnO, and Y2O3.

[0049] The electrolyte that constitutes the electrolyte solution in which the electrode assembly 300 is impregnated is A + B - The salt may have the structure: + Li + , Na + , K. + and alkali metal cations such as B - is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , ClO4 - , AlO4 - , AlCl4 - , PF6 - , SbF6 - , AsF6 - , BF2C2O4 - , BC4O8 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , C4F9SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N- , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - The compound contains one or more anions selected from the group consisting of:

[0050] The electrolyte may also be dissolved in an organic solvent, such as propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, N-methyl-2-pyrrolidone (NMP), ethyl methyl carbonate (EMC), gamma-butyrolactone, or a mixture thereof.

[0051] 1 and 2, in the prismatic secondary battery 10 of the present invention, a first beading process portion 400 is formed on at least two opposing surfaces along the front, rear, left, and right edges of the case 100. The first beading process portion 400 forms a thin linear concave surface, and the first beading process portion 400, which forms a concave surface toward the inside of the case 100, has a depth that presses against the surface of the electrode assembly 300 housed inside the case 100.

[0052] Because the first beading processing portion 400 has a thin linear shape, it has a very small effect on the capacity of the prismatic secondary battery even when a concave surface is formed inside the case 100. In other words, the first beading processing portion 400 has a very limited effect on the capacity or size of essential components of the prismatic secondary battery 10 housed inside the case, such as the electrode assembly 300 and / or electrolyte.

[0053] 2, first beading portions 400 formed on at least two opposing surfaces along the front, rear, left, and right edges of the case 100 compress the surface of the electrode assembly 300 from opposite directions. That is, the electrode assembly 300, which has a clearance gap with the case 100, is pressed in both directions by the opposing first beading portions 400 to be fixed, thereby improving the support structure of the electrode assembly 300 and suppressing slippage during use. As a result, the mobility of the electrode assembly 300 is restricted by the first beading portions 400, preventing various problems such as short circuits due to electrical contact and broken tabs, thereby significantly improving the safety of the prismatic secondary battery 10.

[0054] The first beading processing unit 400 may press the surface of the negative electrode 310 of the electrode assembly 300 housed inside the case 100. In the electrode assembly 300, the negative electrode 310 is formed larger than the positive electrode 330, and the surface of the negative electrode 310 covers the surface of the positive electrode 330. That is, the surface of the negative electrode 310 covers the surface of the positive electrode 330 and does not expose it.

[0055] In the electrode assembly 300, it is advantageous from a safety perspective to make the anode 310 larger than the cathode 330. This is because of the N / P ratio, which is the ratio of the capacities of the anode 310 and the cathode 330. In a lithium-ion secondary battery using a graphite anode, if the capacity of the anode 310 is not larger than that of the cathode 330, lithium deposition at the anode 310 during overcharge cannot be prevented.

[0056] In this regard, it is preferable to maintain the N / P ratio at approximately 1.12 in consideration of the safety of the secondary battery. As a result, the electrode assembly 300 may be formed such that the anode 310 is larger than the cathode 330. Another reason is that the anode 310 is preferably the surface directly pressed by the first beading processing portion 400 because the anode active material has higher structural stability than the cathode active material.

[0057] 3 is a view illustrating the front of a prismatic secondary battery 10, with the electrode assembly 300 housed inside the case 100 indicated by hidden lines. The first beading portion 400 presses against the surface of the negative electrode 310, and is formed at a position spaced apart from the electrode tab 340 of the electrode assembly 300.

[0058] When the first beading processing unit 400 presses the surface of the negative electrode 310 of the electrode assembly 300, it may support a coated portion coated with a negative electrode active material or a plain portion not coated with a negative electrode active material. If the first beading processing unit 400 presses the negative electrode plain portion, it is preferable to support the negative electrode tab 342 formed by notching the negative electrode plain portion at a certain distance below the negative electrode tab 342. This is because the first beading processing unit 400 directly presses the electrode tab 340, particularly the negative electrode tab 342, and generates stress on the electrode tab 340, which may damage the electrode tab 340.

[0059] In addition, the first beading processing portion 400 may be formed adjacent to the cap plate 200 forming the upper surface of the case 100 so as to press the upper portion of the electrode assembly 300 housed inside the case 100 .

[0060] 1, the first beading processing portion 400 may be formed on the two sides of the case 100 that have the longest widthwise lengths among the front, rear, left, and right edges, i.e., the front and rear sides of the case 100 as viewed in the drawing. As a result, the first beading processing portion 400 may be formed to have a sufficient length, thereby firmly supporting the electrode assembly 300.

[0061] Alternatively, as shown in FIG. 4, the first beading processing portion 400 may be formed continuously on all four sides along the front, rear, left, and right edges of the case 100, and by compressing the electrode assembly 300 from all sides, the electrode assembly 300 can be more securely compressed and supported.

[0062] (Second embodiment) FIG. 5 is a view illustrating the external shape of a prismatic secondary battery 10 according to a second embodiment of the present invention, and FIG. 6 is a cross-sectional view of the prismatic secondary battery 10 of FIG. 5 taken along line "BB."

[0063] As shown in Figures 5 and 6, according to the second embodiment of the present invention, the case 100 further includes a second beading processing portion 410 formed on at least two opposing surfaces along the front, rear, left, and right edges at a height adjacent to the bottom surface of the case 100.

[0064] The second beading processor 410 is an additional component that complements the first beading processor 400 described in the first embodiment and more reliably prevents slippage of the electrode assembly 300. The first beading processor 400 compresses and supports the upper portion of the electrode assembly 300, while the second beading processor 410 supports the lower portion of the electrode assembly 300.

[0065] 6, the second beading processing unit 410 contacts and supports the bottom surface of the electrode assembly 300 housed inside the case 100 without pressing on the surface of the electrode assembly 300. In other words, the second beading processing unit 410 does not directly press on the electrode assembly 300 but serves to support the bottom surface to prevent the electrode assembly 300 from moving downward.

[0066] In the second embodiment, the second beading processing portion 410 supports the bottom surface of the electrode assembly 300, while the first beading processing portion 400 presses and fixes the top of the electrode assembly 300, so that the slippage of the electrode assembly 300 is almost eliminated.

[0067] Here, the second beading processing portion 410 is not formed as a structure that directly compresses the electrode assembly 300 because, in the process of fixing both the upper and lower parts of the electrode assembly 300, unintended deformation of the electrode assembly 300 may occur, which may be detrimental to the impregnation of the electrolyte. Furthermore, if swelling occurs in the electrode assembly 300 due to repeated charging and discharging of the prismatic secondary battery 10, the second beading processing portion 410 may act as an obstacle in accommodating deformation of the electrode assembly 300.

[0068] As with the first beading processing portion 400, the second beading processing portion 410 may be formed on the front and rear surfaces of the case 100 that have the longest widthwise lengths, or may be formed continuously on all four sides along the front, rear, left, and right edges of the case 100. Fig. 5 illustrates an embodiment in which the second beading processing portion 410 is formed on each of the front and rear surfaces of the case 100, and Fig. 7 illustrates an embodiment in which the second beading processing portion 410 is formed continuously on all four sides along the front, rear, left, and right edges of the case 100.

[0069] The present invention has been described in more detail above with reference to the drawings and embodiments, etc. However, the configurations described in the drawings or embodiments in this specification are merely one embodiment of the present invention and do not represent all of the technical ideas of the present invention, so it should be understood that there may be various equivalents and modifications that can replace them at the time of filing this application. [Explanation of symbols]

[0070] 10: Prismatic secondary battery 100: Case 200: Cap plate 210: Electrode terminal 300: Electrode assembly 310: Negative electrode 320: Separation membrane 330: Positive electrode 340: Electrode tab 342: Negative electrode tab 344: Positive electrode tab 400: First beading processing section 410: Second beading processing section

Claims

1. A case in which at least one surface forms an open surface; an electrode assembly housed inside the case through an open surface of the case; a cap plate that is coupled to the open surface of the case so as to seal the case and that is provided with positive and negative electrode terminals; A prismatic secondary battery in which a first beading processed portion having a continuous recess is formed on all four sides along the front, rear, left and right edges of the case.

2. The first beading processing section is The prismatic secondary battery according to claim 1 , wherein the electrode assembly is pressed against a surface of the electrode assembly housed inside the case.

3. The first beading processing section is The prismatic secondary battery according to claim 2 , wherein the negative electrode of the electrode assembly housed inside the case is pressed against the negative electrode.

4. The electrode assembly is The prismatic secondary battery according to claim 3 , wherein the negative electrode surface covers the positive electrode surface, leaving the positive electrode surface unexposed.

5. The first beading processing section is The prismatic secondary battery according to claim 3 , wherein the electrode tabs are formed at positions spaced apart from the electrode tabs of the electrode assembly housed inside the case.

6. The first beading processing section is The prismatic secondary battery of claim 5 , wherein the cap plate is formed adjacent to the cap plate so as to press against an upper portion of the electrode assembly housed inside the case.

7. The first beading processing section is 7. The prismatic secondary battery according to claim 1, wherein the insulating layer is formed on the front and rear edges of the case, the front and rear edges having the longest widthwise lengths.

8. The prismatic secondary battery according to claim 1 , further comprising second beading portions formed on at least two opposing surfaces along the front, rear, left, and right edges at a height adjacent to the bottom surface of the case.

9. The second beading processing section is The prismatic secondary battery according to claim 8 , further comprising a support for a lower portion of the electrode assembly housed inside the case.

10. The second beading processing section is The prismatic secondary battery of claim 9 , wherein the electrode assembly is supported by contacting a bottom surface of the electrode assembly housed inside the case without pressing the surface of the electrode assembly.

11. The second beading processing section is The prismatic secondary battery according to claim 8 , wherein the protective layer is formed on the front and rear edges of the case, the front and rear edges having the longest widthwise lengths.

12. A case having at least one surface forming an open surface; an electrode assembly housed inside the case through an open surface of the case; a cap plate that is coupled to the open surface of the case so as to seal the case and that is provided with positive and negative electrode terminals; a first concave beading portion is formed on at least two opposing surfaces along the front, rear, left, and right edges of the case; A prismatic secondary battery, in which second beading processed portions are formed continuously on all four sides along the front, rear, left and right edges of the case at a height adjacent to the bottom surface of the case.

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