Cylindrical battery

Abstract

The present invention relates to a cylindrical battery, specifically to a cylindrical battery including an electrode assembly and a battery case including an electrode assembly receiving portion, and more specifically to a cylindrical secondary battery including a jelly-roll type electrode assembly with an outer circumferential tab structure and a battery case including a protrusion provided on at least a portion of the electrode assembly receiving portion.

Description

[Technical field]

[0001] The present invention relates to a cylindrical battery, specifically to a cylindrical battery including an electrode assembly and a battery case including an electrode assembly receiving portion, and more specifically to a cylindrical secondary battery including a jelly roll-type electrode assembly having an outer periphery tab structure and a battery case including an electrode assembly receiving portion. This application claims the benefit of the filing date of Korean Patent Application No. 10-2022-0156483 filed in the Korean Intellectual Property Office on November 21, 2022, and all contents disclosed in the documents of the corresponding Korean patent application are incorporated herein by reference. [Background technology]

[0002] In cylindrical batteries, a jelly roll type electrode assembly is prepared by winding a long electrode having a certain width into a roll. In cylindrical batteries manufactured by inserting such a jelly roll type electrode assembly into a battery case, the electrodes repeatedly contract and expand during charging and discharging, and the jelly roll structure can cause stress due to steps.

[0003] In particular, in a jelly-roll type electrode assembly having a structure in which the negative electrode is the outermost layer, the outermost negative electrode covers the end of the positive electrode, and the space on the side of the free edge of the positive electrode is left as an empty space due to the thickness of the positive electrode. In this case, stress is generated in the negative electrode due to the step caused by the thickness of the positive electrode, and this stress is concentrated on the surface opposite to the surface facing the positive electrode during charging and discharging, which may cause cracks in the outer periphery of the negative electrode.

[0004] In order to prevent such cracks from occurring in the outer periphery of the negative electrode, there is a need to develop a technology that can reduce the stress concentration on the negative electrode in that area. Summary of the Invention [Problem to be solved by the invention]

[0005] An object of the present invention is to provide a cylindrical battery in which the occurrence of cracks in the outer casing of the negative electrode is improved by modifying the design of the battery case.

[0006] However, the problems to be solved by the present invention are not limited to those mentioned above, and other problems not mentioned will be clearly understood by those skilled in the art from the following description. [Means for solving the problem]

[0007] One embodiment of the present invention provides a cylindrical battery comprising an electrode assembly and a battery case including an electrode assembly housing portion, the battery case including a protrusion provided on at least a portion of the electrode assembly housing portion, the electrode assembly being formed by stacking and winding a first electrode, a separator, and a second electrode, the second electrode including a second electrode current collector, and a second electrode active material layer provided on at least one surface of the second electrode current collector and having a longitudinal end portion at the same position as the second electrode current collector. Effect of the Invention

[0008] A cylindrical battery according to one embodiment of the present invention includes a battery case including an electrode assembly accommodating portion, and the battery case includes a protrusion provided on at least a portion of the electrode assembly accommodating portion, thereby suppressing expansion of the electrode assembly during repeated cycles and preventing cracks and deformation of the electrode assembly due to stress concentration on the outermost negative electrode.

[0009] The effects of the present invention are not limited to the effects described above, and effects not mentioned will be clearly understood by those skilled in the art based on the present specification and the accompanying drawings. [Brief description of the drawings]

[0010] [Figure 1] 1 is a view showing an electrode assembly and a battery case including an electrode assembly receiving portion of a cylindrical battery according to an embodiment of the present invention; [Diagram 2]2 is a diagram showing a cylindrical battery according to one embodiment of the present invention before and after an electrode assembly is accommodated, specifically, a vertical cross-sectional view of the cylindrical battery in FIG. 1 taken along line A-A'. [Diagram 3] FIG. 2 is a diagram showing a state after an electrode assembly of a cylindrical battery according to one embodiment of the present invention has been accommodated, specifically, a cross-sectional view of the cylindrical battery in FIG. 1 taken along line B-B'. [Figure 4] FIG. 2 is a diagram showing a schematic diagram of a step portion of a cylindrical battery according to one embodiment of the present invention. [Diagram 5] 1A and 1B are diagrams showing an electrode assembly of a cylindrical battery according to one embodiment of the present invention. [Explanation of symbols]

[0011] 100, 100': first electrode 101: First electrode current collector 102, 103: first electrode active material layer 110: Longitudinal end of first electrode 20, 20': Separator 300: second electrode 301: Second electrode current collector 302, 303: second electrode active material layer 310: Longitudinal end of second electrode 40: Second electrode tab C: Core section 50: Battery case 51: Electrode assembly housing 52:Protrusion H: Height of protrusion W: Width of protrusion T: Thickness of the protrusion 60: Step 70: Short circuit prevention tape L1: Depth of the inner surface of the electrode assembly housing L2: diameter of electrode assembly L3: Inner diameter of electrode assembly housing L4: Thickness of the end of the second electrode in the longitudinal direction L5: Distance between the longitudinal end of the step portion and the longitudinal end of the second electrode DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] In this specification, when a part "comprises" a certain component, it does not mean that the part excludes other components, but rather that the part may further include other components, unless otherwise specified.

[0013] In this specification, a member being located "on" another member includes not only a case in which the member is in contact with the other member, but also a case in which another member exists between the two members.

[0014] The present invention will be described in detail below with reference to the drawings. However, the attached drawings are merely for the purpose of illustrating the present invention, and the scope of the present invention is not limited by these drawings.

[0015] One embodiment of the present invention provides a cylindrical battery comprising an electrode assembly and a battery case including an electrode assembly housing portion, the battery case including a protrusion provided on at least a portion of the electrode assembly housing portion, the electrode assembly being formed by stacking and winding a first electrode, a separator, and a second electrode, the second electrode including a second electrode current collector, and a second electrode active material layer provided on at least one surface of the second electrode current collector and having a longitudinal end portion at the same position as the second electrode current collector.

[0016] A cylindrical battery according to one embodiment of the present invention includes a battery case including an electrode assembly accommodating portion, and the battery case includes a protrusion provided on at least a portion of the electrode assembly accommodating portion, thereby suppressing expansion of the electrode assembly during repeated cycles and preventing cracks and deformation of the electrode assembly due to stress concentration on the outermost negative electrode.

[0017] FIG. 1 shows an electrode assembly of a cylindrical battery according to one embodiment of the present invention and a battery case including an electrode assembly receiving portion.

[0018] As shown in FIG. 1, a cylindrical battery according to an embodiment of the present invention includes a battery case 50 including an electrode assembly receiving portion 51. Specifically, the battery case 50 and the electrode assembly receiving portion 51 have shapes corresponding to those of the electrode assembly, and it is preferable that the battery case 50 and the electrode assembly receiving portion 51 are cylindrical in shape to receive a jelly-roll type electrode assembly. The electrode assembly is inserted into the electrode assembly receiving portion, and an electrolyte injection process is performed. Then, an upper portion of the battery case is compressed toward the center in a beading process to fix the vertical movement of the electrode assembly, thereby preventing the electrode assembly from being detached. Also, a cap assembly is attached to the upper portion of the battery case. Specifically, the cylindrical battery according to an embodiment of the present invention further includes a cap assembly attached to an opening of the battery case, and the cap assembly includes a top cap, a safety vent, and a current interrupting element.

[0019] In one embodiment of the present invention, the battery case may be cylindrical. That is, since the electrode assembly according to the present invention is housed in a cylindrical battery case and the battery case including the electrode assembly, the cap assembly, and the electrolyte is cylindrical, the shape of the manufactured battery itself may also be cylindrical.

[0020] In one embodiment of the present invention, the battery case contains an electrolyte. Specifically, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte that can be used in manufacturing a lithium secondary battery, but is not limited thereto. Specifically, the electrolyte contains a non-aqueous organic solvent and a metal salt.

[0021] In one embodiment of the present invention, examples of the non-aqueous organic solvent include aprotic organic solvents such as N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl propionate, and ethyl propionate.

[0022] In one embodiment of the present invention, the metal salt may be a lithium salt. The lithium salt is a substance that is easily dissolved in the non-aqueous electrolyte. For example, the anion of the lithium salt is F. - , Cl - , I - , NO3 - , N(CN) 2- , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN -, and (CF3CF2SO2)2N - One or more selected from the group consisting of:

[0023] In one embodiment of the present invention, the electrolyte may further contain, in addition to the electrolyte components, one or more additives such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, and aluminum trichloride, for improving the life characteristics of the battery, suppressing a decrease in battery capacity, and improving the discharge capacity of the battery.

[0024] Fig. 2 shows the cylindrical battery according to one embodiment of the present invention before and after the electrode assembly is accommodated. Specifically, it is a vertical cross-sectional view of the cylindrical battery in Fig. 1 cut along line A-A'. More specifically, Fig. 2(a) shows the cylindrical battery according to one embodiment of the present invention before the electrode assembly is accommodated, and Fig. 2(b) shows the cylindrical battery according to one embodiment of the present invention after the electrode assembly is accommodated.

[0025] 3 shows a cylindrical battery according to an embodiment of the present invention after the electrode assembly is accommodated in the battery, specifically, a cross-sectional view of the cylindrical battery in FIG.

[0026] 2 and 3, a cylindrical battery according to one embodiment of the present invention includes an electrode assembly and a battery case 50, and the battery case 50 includes a protrusion 52 provided on at least a part of the electrode assembly accommodating portion 51. Specifically, the protrusion 52 is provided on the inner circumferential surface of the electrode assembly accommodating portion 51 of the battery case 50, and is formed to have a predetermined width W, height H, and thickness T.

[0027] During charging and discharging of a cylindrical battery, the electrode assembly accommodated therein repeatedly contracts and expands, and the greater the gap between the electrode assembly and the inner circumferential surface of the electrode assembly receiving portion, the greater the space in which the electrode assembly can expand, and the greater the degree of contraction and expansion. As a result, the stress acting on the outermost layer also increases, which may cause problems with cracks and deformation. In this case, the protrusion protrudes from the inner circumferential surface of the electrode assembly receiving portion by a predetermined thickness and fills a part of the internal space of the battery case, thereby controlling the space formed between the electrode assembly and the inner circumferential surface of the electrode assembly receiving portion. Here, the internal space of the battery case refers to a region having a volume obtained by subtracting the volume of the electrode assembly accommodated therein from the volume surrounded by the inner circumferential surface of the electrode assembly receiving portion.

[0028] That is, the protrusion provided in the electrode assembly receiving portion of the cylindrical battery according to the present invention can prevent the occurrence of cracks and deformation due to stress concentration on the outermost layer of the electrode assembly by suppressing the expansion of the electrode assembly located inside the electrode assembly receiving portion of the cylindrical battery during charging and discharging. Specifically, the protrusion occupies a certain space in the electrode assembly receiving portion, thereby suppressing the expansion of the electrode assembly in a direction facing the inner circumferential surface of the electrode assembly receiving portion, i.e., in a direction opposite to the direction facing the winding axis of the electrode assembly, and can reduce the degree of increase in the pattern length of the first electrode and the second electrode. More specifically, the protrusion suppresses the extension of the first electrode in a direction facing the inner circumferential surface of the electrode assembly receiving portion, i.e., in a direction opposite to the direction facing the winding axis, thereby preventing the occurrence of cracks and deformation due to stress concentration on the outermost layer of the electrode assembly.

[0029] In an embodiment of the present invention, a volume of the internal space of the battery case may be 2% to 5% when the volume of the electrode assembly receiving portion is taken as 100%.

[0030] In one embodiment of the present invention, the diameter of the electrode assembly may be 97% or more and 99.5% or less when the inner diameter of the electrode assembly receiving portion is 100%. In other words, as shown in Figures 2 and 3, the diameter L2 of the electrode assembly may be 97% or more and 99.5% or less when the inner diameter L3 of the electrode assembly receiving portion is 100%.

[0031] When the relationship between the volume of the internal space of the battery case and the volume of the electrode assembly accommodating portion, or the relationship between the diameter of the electrode assembly and the inner diameter of the electrode assembly accommodating portion, is satisfied, it becomes easier to control the space formed between the electrode assembly and the inner surface of the electrode assembly accommodating portion by forming the protrusion, and it becomes easier to prevent cracks and deformation of the electrode assembly due to stress concentration on the outermost negative electrode.

[0032] In one embodiment of the present invention, the protrusion may be made of the same or different material as the battery case. In other words, the protrusion may be formed on at least a part of the electrode assembly receiving portion by increasing the thickness of the battery case itself, for example, an aluminum can itself, but is not limited thereto, and may be provided by attaching another protrusion made of the same or different conductive material as the battery case, for example, any one selected from the group consisting of stainless steel, aluminum, nickel, titanium, burnt carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like, on the inner circumferential surface of the electrode assembly receiving portion.

[0033] In one embodiment of the present invention, the protrusion may be provided in an area of ​​5% to 15% of the entire circumference of the inner circumferential surface of the electrode assembly accommodating portion. In other words, as shown in FIG. 3, the width W of the protrusion 52 may be 5% to 15% of the entire circumference of the inner circumferential surface of the electrode assembly accommodating portion 51. Specifically, the protrusion is preferably provided in an area of ​​7% or more, 9% or more, or 11% or more of the entire circumference of the inner circumferential surface of the electrode assembly accommodating portion. In addition, the protrusion is preferably provided in an area of ​​13% or less, 11% or less, or 9% or less of the entire circumference of the inner circumferential surface of the electrode assembly accommodating portion.

[0034] Within the above-mentioned range, it becomes easier to control the space formed between the electrode assembly and the inner surface of the electrode assembly accommodating portion, and the effect of suppressing expansion of the electrode assembly located inside the cylindrical battery during charging and discharging of the battery is further improved.

[0035] In one embodiment of the present invention, the protrusion may be provided in an area of ​​95% to 100% when the depth of the inner circumferential surface of the electrode assembly accommodating portion is taken as 100%. In other words, as shown in FIG. 2(a), the height H of the protrusion 52 may be 95% to 100% when the depth L1 of the inner circumferential surface of the electrode assembly accommodating portion is taken as 100%. Specifically, the protrusion is preferably provided in an area of ​​95% to 97.5% or 97.5% to 100% when the depth of the inner circumferential surface of the electrode assembly accommodating portion is taken as 100%. For example, the protrusion may be provided in an area of ​​100% when the depth of the inner circumferential surface of the electrode assembly accommodating portion is taken as 100%, and the height H of the protrusion 52 may be the same as the depth L1 of the inner circumferential surface of the electrode assembly accommodating portion. Within the above-mentioned range, it becomes easier to control the space formed between the electrode assembly and the inner surface of the electrode assembly accommodating portion, and the effect of suppressing expansion of the electrode assembly located inside the cylindrical battery during charging and discharging of the battery is further improved.

[0036] In one embodiment of the present invention, the electrode assembly is formed by stacking and winding a first electrode, a separator, and a second electrode, and the second electrode may include the second electrode collector and a second electrode active material layer provided on at least one surface of the second electrode collector and having a longitudinal end at the same position as the second electrode collector. In other words, the longitudinal end of the second electrode may be in a free end shape. Here, the free end shape means a form in which the end of the second electrode active material layer and the end of the electrode collector coincide with each other, which includes not only the case where the longitudinal end completely coincides with a surface perpendicular to the longitudinal direction, but also the case where there is an error in the manufacturing process and measurement.

[0037] In one embodiment of the present invention, the first electrode may be a negative electrode and the second electrode may be a positive electrode.

[0038] In one embodiment of the present invention, the first electrode includes a first electrode collector and a first electrode active material layer provided on the first electrode collector. Specifically, the first electrode may include a first electrode collector and a first electrode active material layer provided on one or both sides of the first electrode collector and made of a first electrode active material. In other words, the first electrode active material layer is formed on a first electrode grounded portion of the first electrode collector, and a surface on which the first electrode active material layer is not formed may be referred to as a first electrode uncoated portion.

[0039] In one embodiment of the present invention, the first electrode collector includes a first electrode-covered portion on which a first electrode active material layer is formed and a first electrode uncoated portion on which the first electrode active material layer is not formed, and a first electrode tab is provided on the first electrode uncoated portion. Specifically, the first electrode collector may include a first electrode uncoated portion and a first electrode tab provided on the first electrode uncoated portion. Thus, the electrode assembly to be manufactured may include one or more first electrode tabs. For example, as shown in FIG. 1, the first electrode tab (not shown) protrudes from a lower surface of the electrode assembly and serves to electrically connect the electrode assembly to an inner circumferential surface of the electrode assembly receiving portion 51 of the battery case 50, and the first electrode tab may serve to fix the protrusion 52 to a region corresponding to a longitudinal end 310 of a second electrode included in the electrode assembly when the electrode assembly is received in the electrode assembly receiving portion 51.

[0040] In one embodiment of the present invention, the first electrode active material layer may be made of a first electrode active material including at least one selected from the group consisting of silicon-based materials and carbon-based materials. The first electrode active material layer may further include a first electrode conductive material and a first electrode binder, and the first electrode active material, the first electrode conductive material, and the first electrode binder may be any negative electrode active material, negative electrode conductive material, and negative electrode binder known in the art without limitation.

[0041] In one embodiment of the present invention, the first electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples thereof include copper, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, etc. Specifically, transition metals that easily adsorb carbon, such as copper and nickel, can be used as the first electrode current collector.

[0042] The thickness of the first electrode current collector may be, but is not limited to, 8 μm or more and 180 μm or less.

[0043] In one embodiment of the present invention, the first electrode binder includes at least one selected from the group consisting of polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, polyacrylic acid, and substances in which hydrogen is substituted with Li, Na, Ca, or the like, and further includes various copolymers thereof.

[0044] In one embodiment of the present invention, the first electrode conductive material is not particularly limited as long as it is conductive and does not cause a chemical change in the battery, and examples that can be used include graphite such as natural graphite and artificial graphite; carbon black such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0045] In one embodiment of the present invention, the second electrode includes a second electrode collector and a second electrode active material layer provided on the second electrode collector. Specifically, the second electrode may include a second electrode collector and a second electrode active material layer provided on one or both sides of the second electrode collector and made of a second electrode active material. In other words, the second electrode active material layer is formed on a second electrode grounded portion of the second electrode collector, and the surface on which the second electrode active material layer is not formed may be referred to as a second electrode uncoated portion.

[0046] In one embodiment of the present invention, the second electrode collector includes a second electrode-coated portion on which a second electrode active material layer is formed and a second electrode uncoated portion on which a second electrode active material layer is not formed, and a second electrode tab is provided on the second electrode uncoated portion. Specifically, the second electrode collector may include a second electrode uncoated portion and a first electrode tab provided on the second electrode uncoated portion. Thus, the electrode assembly to be manufactured may include one or more second electrode tabs. For example, as shown in FIG. 1, the second electrode tab 40 protrudes from an upper surface of the electrode assembly and serves to electrically connect to the cap assembly (not shown). When the electrode assembly is accommodated in the electrode assembly accommodation portion 51, the second electrode tab may serve to fix the protrusion 52 so that it is provided in a region corresponding to a longitudinal end 310 of the second electrode included in the electrode assembly.

[0047] In one embodiment of the present invention, the second electrode current collector is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, baked carbon, or aluminum or stainless steel whose surface has been treated with carbon, nickel, titanium, silver, or the like can be used.

[0048] The second electrode current collector may generally have a thickness of 60 μm or more and 200 μm or less, and the adhesive strength of the second electrode active material can be increased by forming fine irregularities on the surface of the second electrode current collector. For example, the second electrode current collector may be in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc.

[0049] In one embodiment of the present invention, the second electrode active material may be a commonly used positive electrode active material. Specifically, the second electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; a lithium iron oxide such as LiFe3O4, or a compound having the chemical formula Li 1+x Mn 2-x O4 (0≦x≦0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, LiMnO2, lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, V2O5, Cu2V2O7; chemical formula LiNi 1-y M y Lithium nickel oxide with Ni site represented by the chemical formula LiMnO2 (wherein M is any one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and 0.01≦y≦0.3 is satisfied); 2-z M z Examples of the lithium manganese composite oxide include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Co, Ni, Fe, Cr, Zn, and Ta, and satisfies 0.01≦z≦0.1) or Li2Mn3MO8 (wherein M is at least one selected from the group consisting of Fe, Co, Ni, Cu, and Zn); and LiMn2O4 in which part of the Li in the chemical formula is replaced with an alkaline earth metal ion. The second electrode may be Li-metal.

[0050] In one embodiment of the present invention, the second electrode active material layer may further include a second electrode conductive material and a second electrode binder. The second electrode conductive material is for imparting electrical conductivity to the electrode, and can be used without any particular limitation as long as it has electronic conductivity without causing a chemical change in the battery that is constructed. Specifically, the second electrode conductive material may be graphite such as natural graphite or artificial graphite; carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fibers; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives; and the like, which may be used alone or in combination of two or more.

[0051] The second electrode binder plays a role of improving the adhesion between particles of the second electrode active material and the adhesive strength between the second electrode active material and the second electrode current collector. Specific examples include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated EPDM, styrene butadiene rubber (SBR), fluororubber, or various copolymers thereof, which can be used alone or in combination of two or more.

[0052] In one embodiment of the present invention, the separator separates the negative electrode and the positive electrode to provide a path for lithium ion migration. Any separator that is generally used as a separator in a secondary battery may be used without limitation, and in particular, a separator that has low resistance to ion migration of the electrolyte and has excellent moisture absorption ability of the electrolyte is preferable. Specifically, 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, and an ethylene-methacrylate copolymer, or a laminate structure of two or more layers thereof may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of a high-melting point glass fiber, a polyethylene terephthalate fiber, or the like, may be used. In addition, in order to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric substance may be used, and a single layer or multilayer structure may be selectively used.

[0053] In one embodiment of the present invention, the longitudinal end of the first electrode extends longer than the longitudinal end of the second electrode and is further wound around the outer periphery of the electrode assembly. Specifically, the electrode assembly according to one embodiment of the present invention may have a structure in which the longitudinal end of the second electrode, which is a free end shape, is covered by the first electrode, which is the outermost layer, and may have a step portion, which is an empty space formed in a region where the first electrode covers the second end of the second electrode.

[0054] FIG. 4 shows a schematic diagram of a stepped portion of a cylindrical battery according to one embodiment of the present invention.

[0055] FIG. 5 shows an electrode assembly of a cylindrical battery according to one embodiment of the present invention.

[0056] Specifically, as shown in Figures 4 and 5, a first electrode 100 is disposed on the outermost layer of the electrode assembly, and the first electrode 100 includes first electrode active material layers 102, 103 on both sides of a first electrode current collector 101, and may include a non-coating area. In contrast, a second electrode 300 is disposed on one side of the first electrode, which is the outermost layer of the electrode assembly, facing the winding axis, and the second electrode 300 includes second electrode active material layers 302, 303 on both sides of a second electrode current collector 301, but may not include a non-coating area. In other words, the second electrode current collector and the end of the second electrode active material layer may be in a free end shape that coincides with each other. That is, the longitudinal end 310 of the second electrode 300 includes the ends of the second electrode active material layers 302, 303 and the end of the second electrode current collector 301, which have the same length in the longitudinal direction, and the longitudinal end 310 of the second electrode 300 may be aligned with the ends of the second electrode active material layers 302, 303 and the end of the second electrode current collector 301. In addition, in one embodiment of the present invention, the uncoated portion on the surface of the first electrode 100 opposite to the surface facing the end of the longitudinal end 310 of the second electrode 300 may further include a short-circuit prevention tape 70 for reducing the occurrence of short circuits or cracks due to stress concentration in the corresponding region.

[0057] In one embodiment of the present invention, the first electrode may be in direct contact with the inner surface of the battery case, and the battery case may function as a first electrode terminal. Specifically, the first electrode, which is the outermost layer of the electrode assembly, may be a negative electrode, and the electrode assembly may be wound in the order of negative electrode / separator / positive electrode / separator, with the negative electrode being the outermost layer. In other words, the electrode assembly may have a peripheral tab structure in which the negative electrode is exposed at the outermost layer.

[0058] In one embodiment of the present invention, the electrode assembly may be accommodated in the electrode assembly accommodation portion, and the protrusion may be provided in a region corresponding to a longitudinal end of a second electrode included in the electrode assembly. Specifically, the protrusion is formed such that a center thereof coincides with a longitudinal end of the second electrode. Here, the center of the protrusion may refer to a line connecting half points of the width of the protrusion.

[0059] 1 to 3, a cylindrical battery according to an embodiment of the present invention includes an electrode assembly and a battery case 50, and the battery case includes a protruding portion 52 provided in at least a part of the electrode assembly housing portion 51. In this case, the protruding portion may be provided on the inner circumferential surface of the electrode assembly housing portion 51 of the battery case, and in a region corresponding to a longitudinal end portion 310 of a second electrode 300 included in the electrode assembly. In other words, the protruding portion 52 may be provided in a region corresponding to the longitudinal end portion 310 of the second electrode having a free end shape.

[0060] When the protrusion is provided in a region corresponding to a longitudinal end of a second electrode included in the electrode assembly, in the process of the electrode assembly expanding toward the inner circumferential surface of the electrode assembly receiving portion, the region corresponding to the longitudinal end of the second electrode first comes into contact with and is constrained by the battery case, thereby suppressing the expansion. Specifically, during charging and discharging of the battery, the electrode assembly repeatedly contracts and expands toward the inner circumferential surface of the electrode assembly receiving portion of the battery case adjacent to the outer circumferential surface of the electrode assembly, thereby repeatedly coming into contact with and being separated from the inner circumferential surface of the electrode assembly receiving portion of the battery case. That is, the greater the separation distance between the outer circumferential surface of the electrode assembly and the inner circumferential surface of the adjacent electrode assembly receiving portion, the more sufficient the space in which the electrode assembly can expand is formed, and the greater the degree of expansion of the electrode assembly. At this time, the region corresponding to the longitudinal end of the second electrode has a smaller distance from the inner surface of the storage portion of the battery case than the region not corresponding to the protrusion, and when the electrode assembly expands, the outer surface first comes into contact with and is restrained by the protrusion, thereby improving the expansion suppression effect in the relevant region.

[0061] In one embodiment of the present invention, the electrode assembly may be accommodated in the electrode assembly accommodating portion, and the protrusion may be provided in a region corresponding to a longitudinal end of the second electrode through the first electrode located in the outermost layer of the electrode assembly. When the protrusion is provided in a region corresponding to a longitudinal end of the second electrode through the first electrode located in the outermost layer of the electrode assembly, expansion in the corresponding region is suppressed, thereby mitigating stress concentration on a portion of the first electrode facing the second electrode due to the longitudinal end of the second electrode, and the effect of preventing cracks and deformation is further improved.

[0062] In one embodiment of the present invention, the electrode assembly is accommodated in the electrode assembly accommodation portion, the protrusion is provided in a region corresponding to a step portion included in the electrode assembly, and the step portion may be an empty space formed in a region where the first electrode covers the longitudinal end portion of the second electrode. Specifically, as shown in Figs. 3 and 4, the protrusion 52 may be provided so as to cover the entire region corresponding to the step portion 60. Here, the "region corresponding to the step portion" refers to a region from a line parallel to the longitudinal end portion 310 of the second electrode on the first electrode 100 to a line connecting the portions where the first electrode abuts via a separator, that is, a region having a distance L5 between the longitudinal end portion of the step portion 60 and the longitudinal end portion 310 of the second electrode, and a region having a distance L5' equal to L5 in the direction opposite to the longitudinal direction of the first electrode.

[0063] In other words, the "region corresponding to the step" means a region on the first electrode 100 having distances of L5 and L5' on both sides of the longitudinal direction of the first electrode 100 from a line parallel to the longitudinal end 310 of the second electrode, and may have a length of "L5+L5'=L5+L5=2×L5'". That is, the width W of the protrusion 52 is larger than the length of the region corresponding to the step 60, and may be equal to or greater than "2×L5".

[0064] In one embodiment of the present invention, the thickness of the protrusion may be 30% to 50% of the step formed by the thickness of the longitudinal end of the second electrode. In other words, as shown in Figures 3 and 4, the thickness T of the protrusion may be 30% to 50% of the thickness L4 of the longitudinal end 310 of the second electrode. Specifically, the thickness of the protrusion is preferably 30% to 40% or 40% to 50% of the step formed by the thickness of the longitudinal end of the second electrode. If the thickness of the protrusion is within the above range, the effect of suppressing expansion of the electrode assembly located in the cylindrical battery and the effect of preventing cracks from occurring during charging and discharging the battery are further improved.

[0065] According to an embodiment of the present invention, there is provided a battery module including the cylindrical battery as a unit cell, and a battery pack including the same. The battery module and the battery pack include the secondary battery having improved high capacity, high stability, and long life characteristics, and can be used as a power source for medium to large devices selected from the group consisting of electric vehicles, hybrid vehicles, plug-in hybrid vehicles, and power storage systems.

[0066] The above describes preferred embodiments of the present invention to aid in understanding the present invention. However, it will be apparent to those skilled in the art that the above-described embodiments are merely examples of the invention, and that various changes and modifications can be made within the scope of the scope and technical ideas of the present invention. It goes without saying that such variations and modifications also fall within the scope of the claims.

Claims

1. A cylindrical battery comprising an electrode assembly and a battery case including an electrode assembly receiving portion, the battery case includes a protrusion provided on at least a portion of the electrode assembly receiving portion, The electrode assembly includes a first electrode, a separator, and a second electrode that are stacked and wound, the second electrode includes a second electrode current collector and a second electrode active material layer provided on at least one surface of the second electrode current collector and having a longitudinal end at the same position as the second electrode current collector.

2. The cylindrical battery according to claim 1 , wherein the protrusion is provided over an area of ​​5% to 15% of the entire circumference of the inner circumferential surface of the electrode assembly receiving portion, the area being taken as 100%.

3. The cylindrical battery according to claim 1 , wherein the protrusion is provided in an area that occupies 100% of the depth of the inner circumferential surface of the electrode assembly receiving portion.

4. 2. The cylindrical battery of claim 1, wherein the first electrode is a negative electrode and the second electrode is a positive electrode.

5. 2. The cylindrical battery according to claim 1, wherein a longitudinal end of the first electrode extends longer than a longitudinal end of the second electrode and is further wound around an outer shell of the electrode assembly.

6. The electrode assembly is accommodated in the electrode assembly accommodating portion, The cylindrical battery according to claim 1 , wherein the protrusion is provided in an area corresponding to a longitudinal end of the second electrode included in the electrode assembly.

7. The electrode assembly is accommodated in the electrode assembly accommodating portion, The cylindrical battery according to claim 1 , wherein the protrusion is provided in a region corresponding to a longitudinal end of the second electrode with the first electrode positioned at the outermost edge of the electrode assembly interposed therebetween.

8. The electrode assembly is accommodated in the electrode assembly accommodating portion, the protrusion is provided in a region corresponding to a step portion included in the electrode assembly, 2. The cylindrical battery according to claim 1, wherein the step portion is an empty space formed in a region where the first electrode covers an end portion of the second electrode in the longitudinal direction.

9. 9. The cylindrical battery according to claim 1, wherein a thickness of the protrusion is 30% to 50% of a step formed by a thickness of the end portion in the longitudinal direction of the second electrode.

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