Cylindrical secondary battery and its manufacturing method

Abstract

The present invention relates to a cylindrical secondary battery and a manufacturing method thereof, and by including a negative electrode that does not have a negative electrode active material layer, it is possible to provide a large cylindrical secondary battery that has high energy density, improves cell performance, and ensures safety.

Description

[Technical Field]

[0001] The present invention relates to a cylindrical secondary battery and a manufacturing method thereof, and more particularly to a cylindrical secondary battery that does not include a negative electrode active material layer and a manufacturing method thereof.

[0002] This application claims priority based on Korean Patent Application No. 10-2022-0182927, filed on December 23, 2022, the entire contents of which are incorporated herein by reference. [Background technology]

[0003] With technological advances in electric vehicles and portable electronic devices, the demand for lithium secondary batteries as an energy source is rapidly increasing.

[0004] A lithium secondary battery has a stacked or wound structure of an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive and negative electrodes, and the electrode assembly is housed in a battery case into which an electrolyte is injected. The lithium secondary battery generates electrical energy through oxidation and reduction reactions that occur when lithium ions are inserted into and extracted from the positive and negative electrodes.

[0005] In recent years, as the prices of raw materials for lithium secondary batteries have skyrocketed, consumers are demanding low-cost, high-performance secondary batteries. For example, among positive electrode active materials, lithium iron phosphate (LFP) is approximately 30% cheaper than nickel cobalt manganese oxide (NCM), but has the disadvantage of being approximately 20% lower in energy density. Therefore, when using low-cost LFP, it is essential to design it to improve energy density.

[0006] Meanwhile, lithium secondary batteries can be classified into cylindrical batteries, prismatic batteries, and pouch batteries depending on the shape of the battery case. Among these, cylindrical batteries have a configuration in which a jelly-roll-type electrode assembly, which is manufactured by sequentially stacking sheet-like positive electrode plates, separators, and negative electrode plates and winding them in one direction, is housed in a cylindrical battery can, and the top of the battery can is covered and sealed with a cap plate. The positive electrode plate and negative electrode plate are provided with strip-shaped positive and negative electrode tabs, respectively, which are connected to electrode terminals and electrically connected to an external power source. For reference, the positive electrode terminal is the cap plate, and the negative electrode terminal is the battery can.

[0007] However, cylindrical secondary batteries have problems such as high resistance, heat generation, and poor current collection efficiency due to current concentration on the strip-shaped electrode tabs. Furthermore, with the recent development of electric vehicle technology, there is an increasing demand for batteries with high capacity and high energy density, and there is a need to develop low-cost, high-performance cylindrical batteries. Summary of the Invention [Problem to be solved by the invention]

[0008] Therefore, the present invention has been made in consideration of the above problems, and an object of the present invention is to provide a cylindrical secondary battery having a high energy density per volume and improved cell performance, and a manufacturing method thereof.

[0009] Another object of the present invention is to provide a cylindrical secondary battery with ensured stability and a method for manufacturing the same. [Means for solving the problem]

[0010] The present inventors have found that the above problems can be solved by the following cylindrical secondary battery and method for manufacturing the same.

[0011] According to a first aspect, an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a battery can containing the electrode assembly; and a sealing body sealing an open end of the battery can; the positive electrode comprises a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material on at least one surface of the positive electrode current collector; The negative electrode relates to a cylindrical secondary battery, in which the negative electrode includes a negative electrode current collector and does not include a negative electrode active material layer.

[0012] According to the second aspect, in the first aspect, The present invention relates to a cylindrical secondary battery, wherein the negative electrode is made of only a negative electrode current collector.

[0013] According to the third aspect, in the first or second aspect, The present invention relates to a cylindrical secondary battery, characterized in that the positive electrode active material includes lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese aluminum oxide (NCMA), lithium manganese oxide (LMO), overlithiated oxide (OLO), cobalt-free oxide, nickel-free oxide, manganese-free oxide, manganese-rich oxide, or a mixture thereof.

[0014] According to a fourth aspect, in any one of the first to third aspects, The present invention relates to a cylindrical secondary battery, characterized in that the positive electrode active material is contained in an amount of 80 to 99 parts by mass relative to 100 parts by mass of the entire positive electrode active material layer.

[0015] According to a fifth aspect, in any one of the first to fourth aspects, The cylindrical secondary battery is characterized in that the loading amount of the positive electrode is 110% to 120% based on the loading amount of the positive electrode of a cylindrical secondary battery including the negative electrode active material layer.

[0016] According to a sixth aspect, in any one of the first to fifth aspects, The loading of the positive electrode is 500 mg / cm 2 ~600mg / cm 2 The present invention relates to a cylindrical secondary battery characterized in that the range of

[0017] According to a seventh aspect, in any one of the first to sixth aspects, The present invention relates to a cylindrical secondary battery, wherein the thickness of the positive electrode is 110% to 120% based on the thickness of the positive electrode of a cylindrical secondary battery including a negative electrode active material layer.

[0018] According to an eighth aspect, in any one of the first to seventh aspects, The present invention relates to a cylindrical secondary battery, wherein the thickness of the positive electrode is in the range of 190 μm to 220 μm.

[0019] According to a ninth aspect, in any one of the first to eighth aspects, The cylindrical secondary battery has a capacity increased by 140% to 180% based on the capacity of a cylindrical secondary battery including a negative electrode active material layer.

[0020] According to a tenth aspect, in any one of the first to ninth aspects, The cylindrical secondary battery is characterized in that the energy density per volume is 850 Wh / L or more.

[0021] According to an eleventh aspect, in any one of the first to tenth aspects, The negative electrode current collector has the following structure 1) or 2) in a cylindrical secondary battery: 1) a structure including a porous region and a non-porous region, wherein at least a portion of the porous region is in contact with at least one surface of the separator; 2) A multilayer structure comprising at least one porous sheet and at least one metal sheet.

[0022] According to a twelfth aspect, in any one of the first to eleventh aspects, The cylindrical secondary battery is characterized in that the form factor ratio is 0.25 or more.

[0023] According to a thirteenth aspect, in any one of the first to twelfth aspects, The cylindrical secondary battery is characterized in that the cylindrical secondary battery is an 18650 cell, a 21700 cell, a 46110 cell, a 48750 cell, a 48110 cell, a 48800 cell, or a 46800 cell.

[0024] According to a fourteenth aspect, in any one of the first to thirteenth aspects, The cylindrical secondary battery is characterized in that it is a battery with a tab-less structure that does not include electrode tabs.

[0025] According to a fifteenth aspect, in any one of the first to fourteenth aspects, The cylindrical secondary battery is characterized in that it contains a liquid electrolyte.

[0026] According to a sixteenth aspect, providing a positive electrode, a negative electrode, and a separator; laminating the separator at least once to interpose the separator between the positive electrode and the negative electrode to form an electrode-separator laminate; winding the electrode-separator laminate in one direction to form a jellyroll-type electrode assembly; housing the electrode assembly in a can, and injecting an electrolyte into the can housing the electrode assembly; sealing the open end of the can to form a battery; activating the battery under conditions of ambient temperature and pressure; Including, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material on at least one surface of the positive electrode current collector; The method relates to a method for producing a cylindrical secondary battery, wherein the negative electrode includes a negative electrode current collector and does not include a negative electrode active material layer. [Effects of the Invention]

[0027] The cylindrical secondary battery according to the present invention includes a negative electrode that does not include a negative electrode active material layer, thereby making it possible to increase the energy density of the secondary battery.

[0028] The present invention is economical because it can exhibit a high energy density per volume even when an inexpensive positive electrode active material with a relatively low energy density is used for the positive electrode.

[0029] Furthermore, the present invention can effectively reduce heat generation inside a cylindrical secondary battery, and can achieve excellent safety even in a large cylindrical secondary battery with an increased volume.

[0030] The method for manufacturing a cylindrical secondary battery according to the present invention has the advantage of simplifying the manufacturing process since it is possible to omit the step of applying pressure for activating the secondary battery.

[0031] The following drawings attached to this specification illustrate preferred embodiments of the present invention and serve to further understand the technical concepts of the present invention together with the above-mentioned content of the invention, and therefore the present invention should not be interpreted as being limited to only the matters described in the drawings. [Brief explanation of the drawings]

[0032] [Figure 1] 3 is a view showing a stacked state of electrode assemblies included in a cylindrical secondary battery according to an embodiment of the present invention before being wound up; [Figure 2] 1 is a cross-sectional view showing the structure of a cylindrical battery with a tabless structure according to one embodiment of the present invention. [Figure 3] FIG. 10 is a cross-sectional view of a cylindrical battery with a tabless structure according to another embodiment of the present invention. [Figure 4] 1 is a diagram illustrating a structure of a jelly-roll type electrode assembly provided in a cylindrical secondary battery according to an embodiment of the present invention. [Figure 5] FIG. 2 is a diagram showing the results of an initial charge-discharge test on cylindrical secondary batteries manufactured in Examples 1 and 2 of the present invention and Comparative Example 1. [Figure 6] FIG. 2 is a diagram showing the measurement results of the life span and coulombic efficiency of cylindrical secondary batteries manufactured in Examples 1 and 2 of the present invention and Comparative Example 1. [Figure 7] FIG. 3 is a diagram showing the results of a hot box safety evaluation of the cylindrical secondary battery manufactured in Example 1 of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0033] The present invention will be described in detail below. Prior to this, the terms and words used in the specification and claims are not to be construed as being limited to their ordinary or dictionary meanings, but are to be construed as being in accordance with the meaning and concept of the technical idea of ​​the present invention, in accordance with the principle that the inventor himself can appropriately define the concept of terms in order to best describe the invention. Therefore, it should be understood that the configurations shown in the embodiments described in this specification are merely the most preferred embodiments of the present invention, and do not represent the entire technical idea of ​​the present invention, and therefore, various equivalents and modifications that can be substituted therefor may exist at the time of filing this application.

[0034] Throughout this specification, when a part is said to "comprise" or "have" certain elements, this means that it can further include or have other elements, but not to the exclusion of other elements, unless otherwise specified.

[0035] Throughout this specification, the phrase "A and / or B" means "A, B, or both."

[0036] As a result of extensive research to develop an excellent large cylindrical battery, the inventors discovered that by including a negative electrode that does not have a negative electrode active material layer, it is possible to ensure the safety of the large cylindrical battery, have a high energy density, and improve cell performance, and thus completed the present invention.

[0037] A cylindrical secondary battery according to one aspect of the present invention comprises: an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a battery can containing the electrode assembly; and a sealing body sealing an open end of the battery can; the positive electrode comprises a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material on at least one surface of the positive electrode current collector; The negative electrode includes a negative electrode current collector, but does not include a negative electrode active material layer.

[0038] electrode assembly The electrode assembly may include a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode, and may have a jelly roll structure wound in one direction.

[0039] 1 shows a laminated structure of an electrode assembly before winding that is included in a cylindrical secondary battery according to one aspect of the present invention. Referring to FIG. 1, an electrode assembly A included in a cylindrical secondary battery according to one aspect of the present invention can be manufactured by winding an electrode-separator laminate formed by sequentially stacking a separator 12, a positive electrode 10, a separator 12, and a negative electrode 11 at least once in one direction X.

[0040] Specifically, Fig. 4 is a diagram showing the structure of a jelly-roll type electrode assembly included in a cylindrical secondary battery according to one embodiment of the present invention. Referring to Fig. 4, a separator 12, a positive electrode 10, a separator 12, and a negative electrode 11 are sequentially stacked, the positive electrode 10 has positive electrode active material layers 10b disposed on both sides of a positive electrode current collector 10a, and the negative electrode 11 consists only of a negative electrode current collector 11a, to produce a jelly-roll type electrode assembly.

[0041] In this case, the negative electrode has a structure in which no active material layer is formed, and the positive electrode has a structure in which an active material layer is formed on a long sheet-shaped current collector, and may include a plain portion in which no active material layer is formed in a portion of the current collector. Preferably, the plain portion of the positive electrode may be formed long in the winding direction X on one end of the current collector. In this way, by using a negative electrode in which no active material layer is formed and a positive electrode in which a plain portion is formed in the winding direction X on one end of the current collector, a battery with a tabless structure without an electrode tab can be realized.

[0042] Specifically, a tabless battery can be manufactured by the following method. First, a separator, a positive electrode, a separator, and a negative electrode are sequentially stacked and wound in one direction to form a jelly-roll electrode assembly. Next, the uncoated portion 22 of the positive electrode is folded toward the core, and current collecting plates are welded to the uncoated portions of the positive electrode and the negative electrode, respectively, and the current collecting plates are connected to electrode terminals to form a tabless battery. Meanwhile, the current collecting plates have a larger cross-sectional area than strip-type electrode tabs, and since resistance is proportional to the cross-sectional area of ​​the path through which current flows, forming a secondary battery with the above structure can significantly reduce cell resistance.

[0043] Next, each component of the electrode assembly included in the cylindrical secondary battery according to an embodiment of the present invention will be described in more detail.

[0044] (1) Positive electrode The positive electrode may have a structure in which a positive electrode active material layer is formed on at least one surface of a long sheet-shaped positive electrode current collector, and the positive electrode active material layer may include a positive electrode active material, a conductive material, and a binder.

[0045] Specifically, the positive electrode may be manufactured by coating one or both sides of a long sheet-shaped positive electrode current collector with a positive electrode slurry prepared by dispersing a positive electrode active material, a conductive material, and a binder in a solvent such as dimethyl sulfoxide (DMSO), isopropyl alcohol, N-methylpyrrolidone (NMP), acetone, or water, and then drying the coated positive electrode current collector to remove the solvent. Alternatively, a positive electrode including a non-coated portion may be manufactured by not coating a portion of the positive electrode current collector, for example, one end of the positive electrode current collector, with the positive electrode slurry.

[0046] The positive electrode active material includes lithium iron phosphate (LiFePO4, LFP), and the positive electrode active material may be specifically lithium iron phosphate (LiFePO4).

[0047] When used as a positive electrode active material, lithium iron phosphate compensates for the irreversibility of the negative electrode during the activation process of a lithium secondary battery and acts as a resistor during subsequent charge and discharge, thereby improving the safety of the lithium secondary battery. Furthermore, it is less expensive than commonly used positive electrode active materials such as lithium nickel cobalt manganese oxide, thereby offering cost competitiveness.

[0048] However, the positive electrode active material of the present invention is not limited to lithium iron phosphate, and any material that can be used as a positive electrode active material can be used as the positive electrode active material of the present invention.Typical positive electrode active materials may include lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese aluminum oxide (NCMA), lithium manganese oxide (LMO), overlithiated oxide (OLO), cobalt-free oxide, nickel-free oxide, manganese-free oxide, manganese-rich oxide, or a mixture thereof.

[0049] However, when lithium iron phosphate is used as the positive electrode active material, the energy density of the secondary battery is relatively low. Therefore, the inventors of the present invention have completed the present invention so that the secondary battery has a high energy density even when lithium iron phosphate is used as the positive electrode active material.

[0050] In the present invention, the negative electrode active material layer may be removed from the negative electrode, and the volume created by removing the negative electrode active material layer may further contain a positive electrode active material. For example, the volume created by removing the negative electrode active material layer may further contain about 40% of the positive electrode active material, thereby providing a battery with a higher energy density than a battery including a negative electrode with a conventional negative electrode active material layer.

[0051] According to one embodiment of the present invention, the loading amount of the positive electrode may be 110% to 120% based on the loading amount of the positive electrode of a cylindrical secondary battery including the negative electrode active material layer.

[0052] According to one embodiment of the present invention, the thickness of the positive electrode may be 110% to 120% based on the thickness of the positive electrode of a cylindrical secondary battery including the negative electrode active material layer.

[0053] Specifically, the loading amount of the positive electrode is 500 mg / cm 2 ~600mg / cm 2 , 520 mg / cm 2 ~580mg / cm 2 , or 540 mg / cm 2 ~560mg / cm 2 The range may be:

[0054] Specifically, the thickness of the positive electrode can be in the range of 190 μm to 220 μm, or 200 μm to 220 μm, or 200 μm to 210 μm.

[0055] When the loading amount and / or thickness of the positive electrode is within the above range, it is possible to obtain an advantage that more capacity and energy can be delivered, and the mobility of lithium ions can be improved, thereby improving the life characteristics.

[0056] In the present invention, the "loading amount of the positive electrode" refers to the contents of the positive electrode active material, the binder polymer, and the conductive material contained in the positive electrode active material layer.

[0057] In addition, in the present invention, the "cylindrical secondary battery including a negative electrode active material layer" differs from the cylindrical secondary battery of the present invention only in that the negative electrode active material layer is included. The negative electrode active material layer may include a negative electrode active material and a binder polymer typically used in cylindrical secondary batteries, and the negative electrode active material layer in the present invention is not particularly limited.

[0058] Generally, a cylindrical battery contains a jelly-roll-type electrode assembly in which a sheet-like positive electrode plate, a separator, and a negative electrode plate are sequentially stacked in a cylindrical battery can. However, since the cylindrical secondary battery of the present invention does not include a negative electrode active material layer, an extra space corresponding to the thickness of the negative electrode active material layer may be generated in the battery can compared to a cylindrical secondary battery including a general negative electrode active material layer. Generally, in a cylindrical secondary battery including a negative electrode plate with a negative electrode active material layer, the loading amount of the positive electrode is about 400 mg / cm. 2 ~500mg / cm 2 The thickness of the positive electrode is in the range of about 150 μm to 180 μm, which generally shows a lower loading amount and thinner thickness than the loading amount and thickness of the positive electrode shown in the present invention.

[0059] Therefore, in the present invention, the extra space where the negative electrode active material layer is not provided can be utilized to increase the loading amount and / or thickness of the positive electrode active material layer, thereby achieving advantageous effects in terms of capacity and energy.

[0060] According to one embodiment of the present invention, the positive electrode active material may include lithium iron phosphate (LiFePO4, LFP) and a positive electrode active material typically used in secondary batteries, such as LCO, NCM, NCA, NCMA, LMO, or OLO. More specifically, positive electrode active materials typically used in secondary batteries include layered compounds such as lithium cobalt oxide (LiCoO2) and lithium nickel oxide (LiNiO2), and compounds substituted with one or more transition metals; 1+x Mn 2-x O4 (where x is 0 to 0.33), lithium manganese oxides such as LiMnO3, LiMn2O3, and LiMnO2; lithium copper oxide (Li2CuO2); oxides such as LiV3O8, LiV3O4, V2O5, and Cu2V2O7; chemical formula LiNi 1-x M x Lithium nickel oxide represented by the chemical formula LiMnO2 (wherein M is one or more selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B, and Ga, and x is 0.01 to 0.9); 2-x M x Examples of lithium manganese composite oxides include, but are not limited to, lithium manganese composite oxides represented by Li2Mn3MO8 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and x is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4, in which part of the Li in the chemical formula is substituted with an alkaline earth metal ion; disulfide compounds; and Fe2(MoO4)3.

[0061] The positive electrode active material may be included in an amount of 80 to 99 parts by weight, 85 to 99 parts by weight, or 90 to 99 parts by weight, relative to 100 parts by weight of the total positive electrode active material layer.

[0062] Meanwhile, various positive electrode current collectors used in the art can be used as the positive electrode current collector. For example, the positive electrode current collector can be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like. The positive electrode current collector typically has a thickness of 3 μm to 500 μm, and fine irregularities can be formed on the surface of the positive electrode current collector to enhance the adhesive strength of the positive electrode active material. The positive electrode current collector can be used in various forms, such as a film, sheet, foil, net, porous material, foam, or nonwoven fabric.

[0063] The conductive material is used to impart conductivity to the electrode. Any material that exhibits electronic conductivity without undergoing chemical changes in the resulting battery can be used without any particular limitations. Specific examples include 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, carbon fiber, and carbon nanotubes; metal powders or fibers, such as copper, nickel, aluminum, and silver; conductive whiskers, such as zinc oxide and potassium titanate; conductive metal oxides, such as titanium oxide; and conductive polymers, such as polyphenylene derivatives. One of these materials may be used alone, or two or more may be used in combination. The conductive material is typically contained in an amount of 1% by weight to 30% by weight, preferably 1% by weight to 20% by weight, and more preferably 1% by weight to 10% by weight, based on the total weight of the positive electrode active material layer.

[0064] The binder improves adhesion between positive electrode active material particles and between the positive electrode active material and the positive 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, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, and various copolymers thereof. These binders may be used alone or in combination. The binder may be present in an amount ranging from 1 to 30% by weight, preferably from 1 to 20% by weight, and more preferably from 1 to 10% by weight, based on the total weight of the positive electrode active material layer.

[0065] (2) Negative electrode The negative electrode includes a negative electrode current collector, but does not include a negative electrode active material layer formed on either side of the negative electrode current collector. Specifically, the negative electrode may consist only of the negative electrode current collector. The absence of a negative electrode active material layer in the negative electrode has the advantages of reducing the process, manufacturing time, and cost compared to a case in which the negative electrode includes a negative electrode active material layer, thereby reducing the unit price of the battery, and also increasing the energy density.

[0066] The negative electrode current collector may be a negative electrode current collector commonly used in the art, such as copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. The negative electrode current collector may typically have a thickness of 3 μm to 500 μm, and like the positive electrode current collector, may have fine irregularities formed on the surface of the current collector, and may be used in various forms such as a film, sheet, foil, net, porous material, foam, nonwoven fabric, etc.

[0067] According to one embodiment of the present invention, the negative electrode current collector may have the following structure 1) or 2).

[0068] 1) a structure comprising a porous region and a non-porous region, wherein at least a portion of the porous region is in contact with at least one surface of the separator; or 2) A multilayer structure comprising at least one porous sheet and at least one metal sheet.

[0069] When the negative electrode current collector has the structure described in 1), the non-porous region of the negative electrode current collector may be located in the center of the negative electrode current collector.

[0070] The negative electrode current collector may have a porosity of 30% to 80%. When the negative electrode current collector has a porosity in this range, an electrodeposition space can be created when lithium is electrodeposited from the positive electrode to the negative electrode, and the cylindrical secondary battery sealed in the battery can experiences almost no volume change, allowing stable charge and discharge.

[0071] In the present invention, the term "porosity" refers to the ratio of the volume occupied by pores to the total volume of a measurement object, and is expressed in units of vol%. The term "porosity" can be used interchangeably with terms such as void ratio and porosity.

[0072] Meanwhile, when the negative electrode current collector has a multi-layer structure as in 2), it may have a sandwich structure in which the metal sheet is positioned between two porous sheets, and the porosity of the porous sheets may be 30% to 80%.

[0073] The porous sheet may be copper; stainless steel; aluminum; nickel; titanium; sintered carbon; copper or stainless steel surface treated with carbon, nickel, titanium, silver, chromium, or the like; aluminum-cadmium alloy; or a material containing two or more of these.

[0074] The metal sheet may comprise lithium, a lithium alloy, or a mixture thereof.

[0075] The thickness of the metal sheet may be 0.1 μm to 10 μm. A metal sheet having a thickness in this range can provide an appropriate energy density and is preferable from an economical point of view.

[0076] (3) Separator The separator separates the negative electrode and the positive electrode and provides a path for lithium ions to move. Any separator typically used in lithium secondary batteries can be used without particular limitations. Specifically, the separator can be a porous polymer film, such as 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, or an ethylene / methacrylate copolymer, or a laminate structure of two or more layers thereof. Conventional porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, can also be used. Furthermore, to ensure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymeric material can also be used.

[0077] In another embodiment of the separator according to the present invention, at least one surface may further include a porous coating layer containing inorganic particles and a binder polymer.

[0078] In the porous coating layer, inorganic particles may be packed together and bound to each other by the binder polymer in a contact state, thereby forming interstitial volumes between the inorganic particles, and the interstitial volumes between the inorganic particles become empty spaces to form pores.

[0079] The inorganic particles used to form the porous coating layer are inorganic particles, i.e., particles that are within the operating voltage range of the electrochemical device (e.g., Li / Li + Inorganic particles that do not undergo oxidation and / or reduction reactions at a voltage of 0 to 5 V relative to the reference voltage can be further added. In particular, when inorganic particles having ion transfer ability are used, the ionic conductivity within the electrochemical device can be increased, thereby improving performance. Furthermore, when inorganic particles with a high dielectric constant are used, they can contribute to increasing the degree of dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte solution.

[0080] For the reasons mentioned above, the inorganic particles preferably include high-dielectric-constant inorganic particles having a dielectric constant of 5 or more, preferably 10 or more, inorganic particles having lithium ion transfer ability, or a mixture thereof.

[0081] Non-limiting examples of inorganic particles with a dielectric constant of 5 or greater include BaTiO3, Pb(Zr,Ti)O3 (PZT), Pb 1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3 (PMN-PT), hafnia (HfO2), SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiC, or mixtures thereof.

[0082] In particular, the aforementioned BaTiO3, Pb(Zr,Ti)O3 (PZT), and Pb1-x La x Zr 1-y Ti y O3(PLZT), PB(Mg 1 / 3 Nb 2 / 3 Inorganic particles such as )O3-PbTiO3 (PMN-PT) and hafnia (HfO2) not only exhibit high dielectric constants of over 100, but also possess piezoelectricity, which generates electric charges and a potential difference between the two sides when stretched or compressed under a certain pressure. This prevents internal short circuits between the electrodes due to external impacts and improves the safety of electrochemical devices. Furthermore, when the aforementioned high-dielectric inorganic particles are mixed with inorganic particles capable of transferring lithium ions, the synergistic effects of these two properties are amplified.

[0083] Inorganic particles with lithium ion transport ability refer to inorganic particles that contain lithium element but have the function of transporting lithium ions without storing lithium. Inorganic particles with lithium ion transport ability can transport and transport lithium ions through a type of defect present inside the particle structure, thereby improving the lithium ion conductivity in the battery and thereby improving the battery performance. Non-limiting examples of inorganic particles with lithium ion transport ability include lithium phosphate (Li3PO4), lithium titanium phosphate (Li x Ti y (PO4)3,0 <x<2、0<y<3)、リチウムアルミニウムチタンフォスフェイト(Li x Al y Ti z (PO4)3,0 <x<2、0<y<1、0<z<3)、14Li2O-9Al2O3-38TiO2-39P2O5などの(LiAlTiP) x O y Glass (0 <x<4、0<y<13)、リチウムランタンチタネート(Li x La y TiO3, 0 <x<2、0<y<3)、Li 3.25 Ge 0.25 P 0.75Lithium germanium thiophosphate such as S4 (Li x Ge y P z S w 、0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), lithium nitride such as Li3N (Li x N y 、0 < x < 4, 0 < y < 2), SiS2-based glass such as Li3PO4-Li2S-SiS2 (Li x Si y S z 、0 < x < 3, 0 < y < 2, 0 < z < 4), P2S5-based glass such as LiI-Li2S-P2S5 (Li x P y S z 、0 < x < 3, 0 < y < 3, 0 < z < 7), or mixtures thereof, etc.

[0084] The size of the inorganic particles in the porous coating layer is not particularly limited, but for forming a coating layer with a uniform thickness and an appropriate porosity, it is preferably 0.001 μm to 10 μm. If it is less than 0.001 μm, the dispersibility of the inorganic particles may decrease. If it exceeds 10 μm, the thickness of the porous coating layer increases, and the mechanical properties may decrease. Also, since the pore size is too large, the possibility of internal short circuit occurring during charging and discharging of the battery becomes high.

[0085] Examples of binder polymers that form the porous coating layer include polyvinylidene fluoride-co-hexafluoropropylene (PVdF-HFP), polyvinylidene fluoride-co-trichloroethylene, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, ethylene-co-vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, and cellulose acetate propionate. The binder polymer may be any one selected from the group consisting of cellulose acetate, cellulose acetate ester ...

[0086] The composition ratio of inorganic particles to binder polymer used in the porous coating layer is preferably, for example, in the range of 50:50 to 99:1, more preferably 70:30 to 95:5. If the content ratio of inorganic particles to binder polymer is less than 50:50, the content of binder polymer will be too high, which may reduce the thermal stability of the separator. Furthermore, the reduction in voids formed between the inorganic particles may reduce the pore size and porosity, potentially resulting in a deterioration in final battery performance. If the content of inorganic particles exceeds 99 parts by weight, the content of binder polymer will be too low, which may reduce the peel resistance of the porous coating layer. The thickness of the porous coating layer is not particularly limited, but is preferably in the range of 0.01 μm to 20 μm. The pore size and porosity are also not particularly limited, but the pore size is preferably in the range of 0.001 μm to 10 μm, and the porosity is preferably in the range of 10% to 90%. The pore size and porosity depend primarily on the size of the inorganic particles. For example, when inorganic particles with a particle size of 1 μm or less are used, the size of the pores formed will also generally be 1 μm or less. This pore structure is subsequently filled with the electrolyte, and the filled electrolyte plays a role in ion transport. If the pore size and porosity are less than 0.001 μm and 10%, respectively, the material may act as a resistive layer. If the pore size and porosity are greater than 10 μm and 90%, respectively, the mechanical properties may be reduced.

[0087] The porous coating layer can be formed by dissolving or dispersing a binder polymer in a dispersion medium, adding inorganic particles to obtain a slurry for forming the porous coating layer, and then coating the slurry on at least one surface of a substrate and drying it. The dispersion medium preferably has a solubility index similar to that of the binder polymer to be used and a low boiling point. This facilitates uniform mixing and subsequent removal of the dispersion medium. Non-limiting examples of dispersion mediums that can be used include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof.

[0088] It is preferable to add inorganic particles to a dispersion in which the binder polymer is dispersed in a dispersion medium, and then crush the inorganic particles. In this case, the crushing time is preferably 1 to 20 hours, and the particle size of the crushed inorganic particles is preferably 0.001 μm to 10 μm, as described above. As a crushing method, a conventional method can be used, and a ball mill method is particularly preferable.

[0089] The binder polymer dispersion containing the dispersed inorganic particles is then coated on at least one surface of a porous polymer substrate under a humidity condition of 10% to 80% and dried. The dispersion can be coated on the porous polymer substrate by a conventional coating method known in the art, such as dip coating, die coating, roll coating, comma coating, or a combination thereof.

[0090] In addition to the inorganic particles and binder polymer described above, the porous coating layer may further contain other additives such as a conductive agent.

[0091] The final separator manufactured according to the present invention may have a thickness of 1 μm to 100 μm or 5 μm to 50 μm. If the thickness is less than 1 μm, the separator may not function properly and mechanical properties may deteriorate, while if the thickness is more than 100 μm, battery properties may deteriorate during high-rate charge / discharge. The separator may also have a porosity of 40% to 60% and an air permeability of 150 to 300 seconds / 100 mL.

[0092] Cylindrical lithium secondary battery Next, the cylindrical lithium secondary battery according to the present invention will be described.

[0093] The cylindrical battery according to the present invention may include an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a battery can that houses the electrode assembly; and a seal that seals an open end of the battery can.

[0094] The cylindrical lithium secondary battery according to the present invention may be a cylindrical battery having a form factor ratio (defined as the value obtained by dividing the diameter by the height of the cylindrical battery, i.e., the ratio of the diameter Φ to the height H) of 0.25 or more, or 0.4 or more. Here, the form factor refers to a value representing the diameter and height of a cylindrical battery.

[0095] Cylindrical batteries according to the present invention may be, for example, 18650 cells (18 mm diameter, 65 mm height, 0.277 form factor ratio), 21700 cells (21 mm diameter, 70 mm height, 0.300 form factor ratio), 46110 cells (46 mm diameter, 110 mm height, 0.418 form factor ratio), 48750 cells (48 mm diameter, 75 mm height, 0.640 form factor ratio), 48110 cells (48 mm diameter, 110 mm height, 0.418 form factor ratio), 48800 cells (48 mm diameter, 80 mm height, 0.600 form factor ratio), or 46800 cells (46 mm diameter, 80 mm height, 0.575 form factor ratio). In the form factor numbers, the first two digits represent the cell diameter, the next two digits represent the cell height, and the final digit, 0, indicates a circular cell cross section.

[0096] The cylindrical lithium secondary battery according to the present invention can exhibit a high energy density per volume by including a negative electrode that does not include a negative electrode active material layer. According to one embodiment of the present invention, the capacity of the cylindrical lithium secondary battery according to the present invention can be increased by 140% to 180% based on the capacity of a cylindrical secondary battery including a negative electrode active material layer. Specifically, the cylindrical lithium secondary battery can exhibit an energy density per volume of 850 or 900 Wh / L or more. This can be calculated by multiplying the design capacity of the secondary battery by the average voltage and dividing the result by the volume of the battery size.

[0097] Furthermore, the cylindrical lithium secondary battery according to the present invention can achieve excellent safety even in a cylindrical battery having a form factor ratio of 0.25 or 0.4 or more. In particular, if the negative electrode active material layer is omitted, lithium is stored in metallic form when the negative electrode is charged. However, the present invention is advantageous in thermal stability because gas can be easily discharged in a certain direction.

[0098] Meanwhile, the cylindrical battery according to the present invention may preferably be a battery of tab-less structure that does not include electrode tabs, but is not limited thereto.

[0099] The tabless-structured battery may have, for example, a structure in which the positive electrode and the negative electrode each include an uncoated portion where no active material layer is formed, the positive electrode uncoated portion and the negative electrode uncoated portion are located at the upper and lower ends of the electrode assembly, respectively, current collecting plates are bonded to the positive electrode uncoated portion and the negative electrode uncoated portion, and the current collecting plates are connected to electrode terminals.

[0100] Fig. 2 shows a cross-sectional view of a cylindrical battery with a tabless structure according to one embodiment of the present invention. Hereinafter, a cylindrical battery according to one embodiment of the present invention will be described with reference to Fig. 2. However, Fig. 2 merely shows one embodiment of the present invention, and the structure of the cylindrical battery of the present invention is not limited to the scope disclosed in Fig. 2.

[0101] A cylindrical battery 140 according to one embodiment of the present invention includes the jelly-roll type electrode assembly 141, a battery can 142 that houses the electrode assembly 141, and a seal 143 that seals the open end of the battery can 142.

[0102] In this case, the positive and negative electrodes of the electrode assembly may each include an uncoated portion where no active material layer is formed, and the positive and negative electrode uncoated portions may be stacked and wound such that the positive and negative electrode uncoated portions are located at the upper and lower ends of the electrode assembly, respectively. Since the electrode assembly has been described above, only the remaining components excluding the electrode assembly will be described below.

[0103] The battery can 142 is a cylindrical container with an opening at the top, and is made of a conductive metal material such as aluminum or steel. The battery can accommodates the electrode assembly 141 in the inner space through the opening at the top, along with an electrolyte (not shown).

[0104] As the electrolyte used in the present invention, various electrolytes that can be used in lithium secondary batteries, such as liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, and molten inorganic electrolytes, can be used, and the type thereof is not particularly limited.

[0105] Specifically, the electrolyte may be a liquid electrolyte and may include an organic solvent and a lithium salt.

[0106] The organic solvent may be any solvent that functions as a medium through which ions involved in the electrochemical reaction of the battery can migrate, and may be any solvent. For example, the organic solvent may be an ester, an ether, an imide, a linear carbonate, a cyclic carbonate, or the like, which may be used alone or in combination of two or more thereof.

[0107] Specifically, the ester among the organic solvents may be any one selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate, γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone, and ε-caprolactone, or a mixture of two or more thereof, but is not limited thereto.

[0108] Specific examples of the ethers among the organic solvents include dimethyl ether, diethyl ether, dipropyl ether, dibutyl ether, diisobutyl ether, ethyl methyl ether, ethyl propyl ether, ethyl tert-butyl ether, dimethoxymethane, trimethoxymethane, dimethoxyethane, diethoxyethane, dimethoxypropane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, triethylene glycol dimethyl ether, tetraethylene glycol dimethyl ether, ethylene glycol divinyl ether, diethylene glycol divinyl ether, triethylene glycol divinyl ether, dipropylene glycol dimethylene ether, butylene glycol ether, diethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, dipropylene glycol dimethylene ether, butylene glycol ether, diethylene glycol ethyl methyl ether, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol dimethyl ether, diethylene glycol ethyl ... linear ethers such as ethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, diethylene glycol tert-butyl ethyl ether, and ethylene glycol ethyl methyl ether; cyclic ethers such as dioxolane, methyl dioxolane, dimethyl dioxolane, vinyl dioxolane, methoxy dioxolane, ethyl methyl dioxolane, oxane, dioxane, trioxane, tetrahydrofuran, methyl tetrahydrofuran, dimethyl tetrahydrofuran, dimethoxy tetrahydrofuran, ethoxy tetrahydrofuran, dihydropyran, tetrahydropyran, furan, and 2-methylfuran; and 1,1,2,2-tetrafluoroethyl 2,2,3,3-tetrafluoropropyl ether. Fluorinated ether compounds such as 2,2,3,3-tetrafluoropropyl ether (TTE), bis(fluoromethyl)ether, 2-fluoromethyl ether, bis(2,2,2-trifluoroethyl)ether, propyl 1,1,2,2-tetrafluoroethyl ether, isopropyl 1,1,2,2-tetrafluoroethyl ether, 1,1,2,2-tetrafluoroethyl isobutyl ether, 1,1,2,3,3,3-hexafluoropropyl ethyl ether, 1H,1H,2'H,3H-decafluorodipropyl ether, and 1H,1H,2'H-perfluorodipropyl ether; or mixtures thereof;It may include:

[0109] The lithium salt can be any compound capable of providing lithium ions used in lithium secondary batteries. Specifically, examples of the lithium salt include LiPF, LiClO, LiAsF, LiBF, LiSbF, LiAlO, LiAlCl, LiCF, SO, LiCF, SO, LiN(C, F, SO), LiN(C, F, SO), LiN(CF, SO), LiCl, LiI, and LiB(C, O) . The concentration of the lithium salt is preferably in the range of 0.1 M to 5.0 M, and more preferably 0.1 M to 3.0 M. When the lithium salt concentration is within this range, the electrolyte has appropriate conductivity and viscosity, resulting in excellent electrolyte performance and efficient lithium ion migration.

[0110] In addition to the electrolyte components, the electrolyte may further contain additives for purposes such as improving battery life characteristics, suppressing battery capacity degradation, and improving battery discharge capacity. Examples of additives include, but are not limited to, haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric 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, which may be used alone or in combination. The additives may be present in an amount of 0.1 wt % to 10 wt %, preferably 0.1 wt % to 5 wt %, based on the total weight of the electrolyte.

[0111] The battery can 142 is electrically connected to the uncoated portion 146 of the negative electrode plate and functions as a negative electrode terminal that contacts an external power source and transmits current applied from the external power source to the negative electrode plate.

[0112] If necessary, a beading portion 147 and a crimping portion 148 may be provided at the upper end of the battery can 142. The beading portion 147 may be formed by press-fitting around the outer periphery of the battery can 142. The beading portion 147 prevents the electrode assembly 141 housed inside the battery can 142 from slipping out of the upper opening of the battery 142 and may function as a support on which the sealing body 143 is placed.

[0113] The crimping portion 148 may be formed on the beading portion 147 and has a bent shape extending to enclose the outer circumferential surface of the cap plate 143a disposed on the beading portion 147 and a part of the upper surface of the cap plate 143a.

[0114] Next, the sealing body 143 is for sealing the open end of the battery can 142 and includes a cap plate 143a and a first gasket 143b having insulating properties and providing airtightness between the cap plate 143a and the battery can 142. If necessary, the sealing body 143 may further include a connection plate 143c electrically and mechanically coupled to the cap plate 143a. The cap plate 143a may be crimped onto a beading portion 147 formed on the battery can 142 and fixed by a crimping portion 148.

[0115] The cap plate 143a is a component made of a conductive metal material and covers the upper opening of the battery can 142. The cap plate 143a is electrically connected to the positive electrode plate of the electrode assembly 141 and is electrically insulated from the battery can 142 via the first gasket 143b. Therefore, the cap plate 143a can function as a positive electrode terminal of the cylindrical secondary battery. The cap plate 143a may have a protrusion 143d formed to protrude upward from the center thereof, and the protrusion 143d may come into contact with an external power source so that current can be applied from the external power source.

[0116] A first gasket 143b can be interposed between the cap plate 143a and the crimping portion 148 to ensure airtightness of the battery can 142 and to achieve electrical insulation between the battery can 142 and the cap plate 143a.

[0117] Meanwhile, the cylindrical battery 140 according to the present invention may further include current collecting plates 144 and 145, if necessary. The current collecting plates are bonded to the uncoated portion 146a of the positive plate and the uncoated portion 146b of the negative plate, and are connected to the electrode terminals (i.e., the positive and negative terminals).

[0118] Specifically, the cylindrical battery 140 according to the present invention may include a first current collecting plate 144 coupled to the upper part of the electrode assembly 141 and a second current collecting plate 145 coupled to the lower part of the electrode assembly 141.

[0119] The first current collecting plate 144 is coupled to the upper part of the electrode assembly 141. The first current collecting plate 144 is made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the uncoated portion 146a of the positive electrode plate. A lead 149 may be connected to the first current collecting plate 144. The lead 149 may extend above the electrode assembly 141 and be coupled to the connection plate 143c, or may be directly coupled to the lower surface of the cap plate 143a. The lead 149 may be coupled to other components by welding. Preferably, the first current collecting plate 144 may be integrally formed with the lead 149. In this case, the lead 149 may have a long plate shape extending outward from the center of the first current collecting plate 144.

[0120] Meanwhile, the first current collecting plate 144 is connected to the end of the uncoated portion 146a of the positive electrode plate, and the connection can be performed by a method such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0121] The second current collecting plate 145 is coupled to the lower part of the electrode assembly 141. The second current collecting plate 145 is made of a conductive metal material such as aluminum, copper, or nickel, and is electrically connected to the uncoated portion 146b of the negative electrode plate. One side of the second current collecting plate 145 may be coupled to the uncoated portion 146b of the negative electrode plate, and the other side may be coupled to the inner bottom surface of the battery can 142. In this case, the coupling may be performed by a method such as laser welding, resistance welding, ultrasonic welding, or soldering.

[0122] Meanwhile, the cylindrical battery 140 according to the present invention may further include an insulator 146, if necessary. The insulator 146 may be disposed to cover the upper surface of the first current collecting plate 144. By covering the first current collecting plate 144 with the insulator 146, direct contact between the first current collecting plate 144 and the inner peripheral surface of the battery can 142 can be prevented.

[0123] The insulator 146 has lead holes 151 for extracting the leads 149 extending upward from the first current collecting plate 144. The leads 149 are extracted upward through the lead holes 151 and coupled to the lower surface of the connection plate 143c or the lower surface of the cap plate 143a.

[0124] The insulator 146 may be formed from a polymer resin having insulating properties, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0125] Meanwhile, the cylindrical battery 140 according to the present invention may further include a vent 152 formed on the bottom surface of the battery can 142, if necessary. The vent 152 corresponds to a region on the bottom surface of the battery can 142 that is thinner than the surrounding region. Because the vent 152 is thinner, it is structurally weaker than the surrounding region. Therefore, when the internal pressure of the cylindrical battery 140 exceeds a certain level, the vent 152 ruptures, releasing gas from the battery can 152 to the outside and preventing the battery from exploding.

[0126] Fig. 3 is a cross-sectional view of a cylindrical battery with a tabless structure according to another embodiment of the present invention. Hereinafter, a cylindrical battery according to another embodiment of the present invention will be described with reference to Fig. 3. However, Fig. 3 merely illustrates one embodiment of the present invention, and the structure of the cylindrical battery of the present invention is not limited to the scope disclosed in Fig. 3.

[0127] Referring to FIG. 3, a cylindrical battery 170 according to another embodiment of the present invention has a different structure of the battery can and the sealed body compared to the cylindrical battery 140 shown in FIG. 2, but the configuration of the electrode assembly and electrolyte is substantially the same.

[0128] Specifically, cylindrical battery 170 includes a battery can 171 through which a rivet terminal 172 is inserted. Rivet terminal 172 is provided on the closed surface (top surface in the figure) of battery can 171. Rivet terminal 172 is riveted into a through-hole in battery can 171 with an insulating second gasket 173 interposed therebetween. Rivet terminal 172 is exposed to the outside in the direction opposite to the direction of gravity.

[0129] The rivet terminal 172 includes a terminal exposed portion 172a and a terminal inserted portion 172b. The terminal exposed portion 172a is exposed to the outside of the closed surface of the battery can 171. The terminal exposed portion 172a may be located approximately in the center of the closed surface of the battery can 171. The maximum diameter of the terminal exposed portion 172a may be larger than the maximum diameter of the through-hole formed in the battery can 171. The terminal inserted portion 172b may penetrate approximately the center of the closed surface of the battery can 171 and be electrically connected to the uncoated portion 146a of the positive electrode plate. The terminal inserted portion 172b may be rivet-connected to the inner surface of the battery can 171. That is, an end of the terminal inserted portion 172b may have a shape bent toward the inner surface of the battery can 171. The maximum diameter of the end of the terminal inserted portion 172b may be larger than the maximum diameter of the through-hole in the battery can 171.

[0130] The lower end surface of the terminal insertion portion 172b may be welded to the first current collecting plate 144 connected to the uncoated portion 146a of the positive electrode plate. An insulating cap 174 made of an insulating material may be interposed between the first current collecting plate 144 and the inner surface of the battery can 171. The insulating cap 174 covers the upper portion of the first current collecting plate 144 and the upper edge portion of the electrode assembly 141. This prevents the uncoated portion B3 on the outer periphery of the electrode assembly 141 from coming into contact with the inner surface of the battery can 171, which has the opposite polarity, and causing a short circuit. The terminal insertion portion 172b of the rivet terminal 172 may be welded to the first current collecting plate 144 through the insulating cap 174.

[0131] The second gasket 173 is interposed between the battery can 171 and the rivet terminal 172 to prevent electrical contact between the battery can 171 and the rivet terminal 172, which have opposite polarities. This allows the upper surface of the battery can 171, which has a substantially flat shape, to function as the positive electrode terminal of the cylindrical battery 170.

[0132] The second gasket 173 includes a gasket exposing portion 173a and a gasket inserting portion 173b. The gasket exposing portion 173a is interposed between the terminal exposing portion 172a of the rivet terminal 172 and the battery can 171. The gasket inserting portion 173b is interposed between the terminal inserting portion 172b of the rivet terminal 172 and the battery can 171. When the terminal inserting portion 172b is riveted, the gasket inserting portion 173b deforms and can adhere to the inner surface of the battery can 171. The second gasket 173 may be made of, for example, an insulating polymer resin.

[0133] The gasket exposing portion 173a of the second gasket 173 may have a shape that extends to cover the outer peripheral surface of the terminal exposing portion 172a of the rivet terminal 172. When the second gasket 173 covers the outer peripheral surface of the rivet terminal 172, it is possible to prevent a short circuit from occurring during the process of connecting an electrical connection part such as a bus bar to the upper surface of the battery can 171 and / or the rivet terminal 172. Although not shown in the drawings, the gasket exposing portion 173a may have a shape that extends to cover not only the outer peripheral surface of the terminal exposing portion 172a but also a portion of the upper surface.

[0134] When the second gasket 173 is made of a polymer resin, the second gasket 173 may be joined to the battery can 171 and the rivet terminal 172 by heat sealing. In this case, the airtightness at the joining interface between the second gasket 173 and the rivet terminal 172 and at the joining interface between the second gasket 173 and the battery can 171 may be strengthened. Meanwhile, when the gasket exposed portion 173a of the second gasket 173 extends to the upper surface of the terminal exposed portion 172a, the rivet terminal 172 may be joined integrally with the second gasket 173 by insert injection.

[0135] The remaining area 175 of the upper surface of the battery can 171 excluding the area occupied by the rivet terminal 172 and the second gasket 173 corresponds to a negative terminal having a polarity opposite to that of the rivet terminal 172 .

[0136] The second current collecting plate 176 is coupled to the lower part of the electrode assembly 141. The second current collecting plate 176 is made of a conductive metal material such as aluminum, steel, copper, or nickel, and is electrically connected to the uncoated portion 146b of the negative electrode plate.

[0137] Preferably, the second current collecting plate 176 is electrically connected to the battery can 171. To this end, at least a portion of the edge portion of the second current collecting plate 176 may be fixed between the inner surface of the battery can 171 and the first gasket 178b. In one example, at least a portion of the edge portion of the second current collecting plate 176 may be fixed to the beading portion 180 by welding while being supported by the lower end surface of the beading portion 180 formed at the lower end of the battery can 171. In a modified example, at least a portion of the edge portion of the second current collecting plate 176 may be directly welded to the inner wall surface of the battery can 171.

[0138] The second current collecting plate 176 may have a plurality of projections (not shown) formed radially on the surface facing the uncoated portion 146b. When the projections and recesses are formed, the second current collecting plate 176 can be pressed to press the projections and recesses into the uncoated portion 146b.

[0139] Preferably, the end of the second current collecting plate 176 and the uncoated portion 146b may be joined by welding, for example, laser welding.

[0140] The sealing body 178 that seals the lower open end of the battery can 171 includes a cap plate 178a and a first gasket 178b. The first gasket 178b electrically isolates the cap plate 178a from the battery can 171. A crimping portion 181 secures the edge of the cap plate 178a and the first gasket 178b together. The cap plate 178a is provided with a vent portion 179. The configuration of the vent portion 179 is substantially the same as in the above-described embodiment.

[0141] Preferably, the cap plate 178a is made of a conductive metal material. However, the cap plate 178a does not have electrical polarity because the first gasket 178b is interposed between the cap plate 178a and the battery can 171. The seal 178 seals the open end of the lower part of the battery can 171 and functions to release gas when the internal pressure of the battery cell 170 increases above a critical value.

[0142] Preferably, the rivet terminal 172 electrically connected to the uncoated portion 146a of the positive electrode plate is used as the positive electrode terminal. Furthermore, a portion 175 of the upper surface of the battery can 171, excluding the rivet terminal 172, electrically connected to the uncoated portion 146b of the negative electrode plate via the second current collecting plate 176 is used as the negative electrode terminal. In this manner, when two electrode terminals are arranged on the upper portion of the cylindrical battery, electrical connection components such as bus bars can be arranged on only one side of the cylindrical battery 170. This simplifies the battery pack structure and improves energy density. Furthermore, the portion 175 used as the negative electrode terminal has a substantially flat shape, ensuring a sufficient contact area for joining electrical connection components such as bus bars. As a result, the cylindrical battery 170 can reduce resistance at the joining points of the electrical connection components to a desirable level.

[0143] When a cylindrical lithium secondary battery is formed with a tabless structure as described above, current concentration is reduced compared to conventional batteries with electrode tabs, so heat generation inside the battery can be effectively reduced, thereby improving the thermal safety of the battery.

[0144] A method for manufacturing a cylindrical secondary battery according to one aspect of the present invention includes the steps of: Preparing a positive electrode, a negative electrode, and a separator; laminating the separator at least once to interpose the separator between the positive electrode and the negative electrode to form an electrode-separator laminate; winding the electrode-separator laminate in one direction to form a jellyroll-type electrode assembly; housing the electrode assembly in a battery can, and injecting an electrolyte into the battery can housing the electrode assembly; sealing the open end of the battery can to produce a battery; activating the battery under normal temperature and pressure conditions;

[0145] The specific description of each component is as described above.

[0146] In particular, the present invention is characterized in that in the step of activating the battery, the activation of the battery is carried out under conditions of normal temperature and normal pressure.

[0147] In the battery activation step, an initial charge is performed to activate the electrode active material and form an SEI film on the electrode surface. Generally, in the battery activation step, gas is inevitably generated inside the battery due to the decomposition reaction of the electrolyte, etc., so to activate the battery, it is common to remove the generated gas by activating the battery under a predetermined high-pressure condition.

[0148] However, in the cylindrical secondary battery according to the present invention, the can functions as the outer wall of the jelly roll, and when lithium metal is produced, the pressure generated by the volume expansion contacts the can, allowing the battery to self-pressurize. That is, the cylindrical secondary battery according to the present invention can self-pressurize by itself through initial discharge. Therefore, there is no need for a separate high-pressure condition, specifically, a condition such as pressurizing using a jig, during the battery activation step, which is advantageous in that the process is simplified.

[0149] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0150] Example 1 A positive electrode slurry was prepared by mixing 497 parts by weight of LiFePO4 as a positive electrode active material, 1.5 parts by weight of carbon nanotubes as a conductive material, and 1.5 parts by weight of polyvinylidene fluoride (PVdF, Kureha) as a binder, and then adding the mixture to an N-methyl-2-pyrrolidone solvent and mixing it. The positive electrode slurry was applied to one side of a 15 μm-thick aluminum current collector sheet, dried at 120°C, and rolled to obtain a positive electrode loading of 560 mg / 25 cm. 2A positive electrode plate having a thickness of 200 μm was prepared.

[0151] A copper foil with a thickness of 10 μm was prepared as the negative electrode plate.

[0152] The positive and negative electrode plates prepared as above were stacked in the order of separator / positive electrode plate / separator / negative electrode plate with a separator interposed between them, and then wound up to prepare a jelly roll type electrode assembly. The electrode assembly prepared as above was inserted into a cylindrical battery can, and an electrolyte was injected into it to prepare a cylindrical secondary battery with 21700 cells.

[0153] Comparative Example 1 Anode slurry was prepared by mixing anode active material (a mixture of graphite and SiO2 in a weight ratio of 95:5), conductive material (Super C), styrene-butadiene rubber (SBR), and carboxymethyl cellulose (CMC) in water in a weight ratio of 96:2:1.5:0.5. The cathode slurry was applied to one side of a 10 μm-thick copper foil, dried at 150°C, and rolled to prepare anodes. Cylindrical secondary batteries (21700 cells) were fabricated in the same manner as in Example 1, except that cathode plates were prepared with different amounts of cathode active material, cathode thicknesses, and cathode loadings as shown in Table 1 below.

[0154] Example 2 Cylindrical secondary batteries (21700 cells) were manufactured in the same manner as in Example 1, except that positive electrode plates were prepared with different amounts of positive electrode active material, positive electrode thicknesses, and positive electrode loading amounts, as shown in Table 1 below.

[0155] [Table 1]

[0156] Evaluation example 1.Charge / discharge capacity The cylindrical secondary batteries prepared in Examples 1 and 2 and Comparative Example 1 were charged in CC / CV mode at 25° C. with a constant current of 0.1 C up to 3.9 V (cut-off current 0.1 C), and then discharged in CC mode down to 2.5 V to measure the initial charge / discharge capacity. The results are shown in FIG.

[0157] Within the operating range of the cylindrical secondary battery of Comparative Example 1, up to 26 g of positive electrode active material can be inserted, but when a negative electrode that does not include a negative electrode active material layer is applied as in Examples 1 and 2, the amount of positive electrode active material that can be inserted into the cell increases, thereby maximizing the energy density per volume. Examples 1 and 2 can increase the charge capacity and discharge capacity by approximately 50% compared to Comparative Example 1.

[0158] 2.Life evaluation To confirm the lifespan characteristics of the cylindrical secondary batteries prepared in Examples 1 and 2 and Comparative Example 1, the batteries were charged to 3.9 V at 0.1 C under constant current / constant voltage (CC / CV) conditions at 25° C. for the first cycle, and then charged under constant current (CC) conditions at 0.1 C. After leaving the batteries for 30 minutes, they were discharged to 2.5 V at 0.1 C, and the discharge capacity was measured.

[0159] Thereafter, charging and discharging were repeated at 0.1 C in the voltage range of 3.9 V to 2.5 V for 25 cycles, and the discharge capacity retention rate was measured for each cycle. The results are shown in Figure 6. It can be seen that Examples 1 and 2 have superior charge capacity and discharge capacity compared to Comparative Example 1, but also show a capacity retention rate at a level equivalent to that of Comparative Example 1.

[0160] 3. Hot box evaluation A hot box test was conducted to confirm the safety of the cylindrical secondary battery manufactured in Example 1. In the hot box test, a charged battery was placed in a convection chamber, heated to 130°C at a rate of 5°C / min, and maintained at that temperature for 30 minutes. Then, heated to 200°C at a rate of 5°C / min, and maintained at that temperature for 1 hour, and the cell temperature of the secondary battery was confirmed. The results are shown in Figure 7.

[0161] The hot box test results for the cylindrical secondary battery prepared in Example 1 showed that it could maintain temperatures at 130°C for about 30 minutes and at 200°C for about 1 hour. This result is similar to the hot box test results for cylindrical secondary batteries with a negative electrode coating layer, indicating that Example 1, despite not having a negative electrode coating layer, can ensure excellent safety at the same level as batteries with a negative electrode coating layer.

Claims

1. an electrode assembly including a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode; a battery can accommodating the electrode assembly; and a sealing body sealing an open end of the battery can, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material on at least one surface of the positive electrode current collector; The cylindrical secondary battery includes a negative electrode current collector and does not include a negative electrode active material layer.

2. 2. The cylindrical secondary battery according to claim 1, wherein the negative electrode consists solely of the negative electrode current collector.

3. 2. The cylindrical secondary battery of claim 1, wherein the positive electrode active material comprises lithium iron phosphate (LFP), lithium manganese iron phosphate (LMFP), lithium cobalt oxide (LCO), lithium nickel cobalt manganese oxide (NCM), lithium nickel cobalt aluminum oxide (NCA), lithium nickel cobalt manganese aluminum oxide (NCMA), lithium manganese oxide (LMO), overlithiated oxide (OLO), cobalt-free oxide, nickel-free oxide, manganese-free oxide, manganese-rich oxide, or a mixture thereof.

4. 2. The cylindrical secondary battery according to claim 1, wherein the positive electrode active material is contained in an amount of 80 to 99 parts by weight based on 100 parts by weight of the total positive electrode active material layer.

5. 5. The cylindrical secondary battery according to claim 1, wherein the loading amount of the positive electrode is 110% to 120% based on the loading amount of the positive electrode of a cylindrical secondary battery including a negative electrode active material layer.

6. The loading of the positive electrode is 500 mg / cm ２ ~600 mg / cm ２ The cylindrical secondary battery according to any one of claims 1 to 4, wherein the range is

7. 5. The cylindrical secondary battery according to claim 1, wherein the thickness of the positive electrode is 110% to 120% based on the thickness of the positive electrode of a cylindrical secondary battery including a negative electrode active material layer.

8. 5. The cylindrical secondary battery according to claim 1, wherein the thickness of the positive electrode is in the range of 190 μm to 220 μm.

9. The cylindrical secondary battery according to any one of claims 1 to 4, wherein the capacity of the cylindrical secondary battery is increased by 140% to 180% based on the capacity of a cylindrical secondary battery including a negative electrode active material layer.

10. 2. The cylindrical secondary battery according to claim 1, wherein the cylindrical secondary battery has an energy density per volume of 850 Wh / L or more.

11. 2. The cylindrical secondary battery according to claim 1, wherein the negative electrode current collector has the following structure 1) or 2): 1) a structure comprising a porous region and a non-porous region, wherein at least a portion of the porous region is in contact with at least one surface of the separator; or 2) A multi-layer structure comprising at least one porous sheet and at least one metal sheet.

12. The cylindrical secondary battery according to claim 1 , wherein the cylindrical secondary battery has a form factor ratio of 0.25 or more.

13. 2. The cylindrical secondary battery according to claim 1, wherein the cylindrical secondary battery is an 18650 cell, a 21700 cell, a 46110 cell, a 48750 cell, a 48110 cell, a 48800 cell, or a 46800 cell.

14. 2. The cylindrical secondary battery according to claim 1, wherein the cylindrical secondary battery is a battery of a tab-less structure that does not include electrode tabs.

15. The cylindrical secondary battery according to claim 1 , wherein the cylindrical secondary battery contains a liquid electrolyte.

16. providing a positive electrode, a negative electrode, and a separator; laminating the separator at least once to form an electrode-separator laminate such that the separator is interposed between the positive electrode and the negative electrode; winding the electrode-separator laminate in one direction to form a jellyroll-type electrode assembly; housing the electrode assembly in a can and injecting an electrolyte into the can housing the electrode assembly; sealing the open end of the can to form a battery; activating the battery under normal temperature and pressure conditions; Including, the positive electrode comprises a positive electrode current collector and a positive electrode active material layer containing a positive electrode active material on at least one surface of the positive electrode current collector; The method for producing a cylindrical secondary battery, wherein the negative electrode includes a negative electrode current collector and does not include a negative electrode active material layer.

Images