Cylindrical secondary battery and method for manufacturing same

Abstract

The present invention relates to a cylindrical secondary battery and a method for manufacturing the same, and can provide a large cylindrical secondary battery which includes a negative electrode having no negative electrode active material layer, and thus has high energy density, can improve cell performance, and ensures safety.

Description

Technical Field

[0001] The present disclosure relates to a cylindrical secondary battery and a method for manufacturing the same. In particular, the present disclosure relates to a cylindrical secondary battery without a negative electrode active material layer and a method for manufacturing the same.

[0002] This application claims priority to Korean Patent Application No. 10-2022-0182927 filed in Korea on December 23, 2022, the disclosure of which is incorporated herein by reference. Background Art

[0003] With the development of technologies such as electric vehicles and portable electronic devices, the demand for lithium secondary batteries as energy sources is increasing.

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

[0005] In recent years, as the cost required for the main materials of lithium secondary batteries has increased rapidly, consumers need secondary batteries with high performance and low cost. For example, among positive electrode active materials, lithium iron phosphate (LFP) is about 30% cheaper than nickel cobalt manganese oxide (NCM), but the disadvantage is that the energy density it provides is about 20% lower than that provided by NCM. In other words, when using such cheap LFP, a design that can increase the energy density is required.

[0006] Meanwhile, lithium secondary batteries can be divided into cylindrical, prismatic and pouch-type batteries according to the shape of the battery housing. Among these lithium secondary batteries, the cylindrical battery has a shape obtained by stacking the sheet-like positive plate, the separator and the negative plate in sequence and winding the resulting stack in one direction. The core-wound electrode assembly is received in a cylindrical battery can, and the top of the battery can is covered with a cap plate and then sealed. The positive plate and the negative plate are respectively provided with a strip-shaped positive electrode connector and a negative electrode connector, which are connected to the electrode terminal and electrically connected to an external power source. For reference, the positive terminal is the cap plate and the negative terminal is the battery can.

[0007] However, in the case of cylindrical secondary batteries, the current is concentrated in the strip electrode joints, resulting in large resistance and a large amount of heat generation, and poor current collection efficiency. In addition, in recent years, electric vehicle technology has developed, and the demand for high-capacity and high-energy-density batteries has increased. Under these circumstances, it is necessary to develop cylindrical batteries with high performance and low cost. Summary of the invention

[0008] Technical issues

[0009] The present disclosure is intended to solve the problems of the prior art, and thus the present disclosure is intended to provide a cylindrical secondary battery having high energy density per unit volume and improved battery performance, and a method for manufacturing the same.

[0010] The present disclosure also provides a cylindrical secondary battery ensuring stability and a method of manufacturing the same.

[0011] Technical Solution

[0012] The inventors of the present disclosure have found that the above-mentioned problems can be solved by a cylindrical secondary battery and a method of manufacturing the same as described below.

[0013] According to a first embodiment of the present disclosure, there is provided a cylindrical secondary battery including:

[0014] 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 configured to receive the electrode assembly; and a sealing body configured to seal an open end of the battery can,

[0015] The positive electrode is provided with a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is provided on at least one surface of the positive electrode current collector and contains a positive electrode active material, and

[0016] The negative electrode includes a negative electrode current collector but does not have a negative electrode active material layer.

[0017] According to a second embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in the first embodiment,

[0018] Wherein, the negative electrode only includes the negative electrode current collector.

[0019] According to a third embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in the first or second embodiment,

[0020] The positive electrode active material includes lithium iron phosphate (LFP), lithium iron manganese 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), over-lithium oxide (OLO), cobalt-free oxide, nickel-free oxide, manganese-free oxide, manganese-rich oxide or a mixture thereof.

[0021] According to a fourth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to third embodiments,

[0022] Wherein, based on 100 parts by weight of the total weight of the positive electrode active material layer, the amount of the positive electrode active material is 80 to 99 parts by weight.

[0023] According to a fifth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to fourth embodiments,

[0024] The loading amount of the positive electrode is equivalent to 110% to 120% of the loading amount of the positive electrode of a cylindrical secondary battery having a negative electrode active material layer.

[0025] According to a sixth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to fifth embodiments,

[0026] Wherein, the loading amount of the positive electrode is 500mg / cm 2 Up to 600mg / cm 2 .

[0027] According to a seventh embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to sixth embodiments,

[0028] The thickness of the positive electrode is equivalent to 110% to 120% of the thickness of the positive electrode of a cylindrical secondary battery having a negative electrode active material layer.

[0029] According to an eighth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to seventh embodiments,

[0030] Wherein, the thickness of the positive electrode is 190 μm to 220 μm.

[0031] According to a ninth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to eighth embodiments,

[0032] It exhibits a capacity increase of 140% to 180% relative to that of a cylindrical secondary battery having a negative electrode active material layer.

[0033] According to a tenth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to ninth embodiments,

[0034] It exhibits an energy density per unit volume of over 850Wh / L.

[0035] According to an eleventh embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to tenth embodiments,

[0036] Wherein, the negative electrode current collector has the following structure 1) or 2):

[0037] 1) A structure comprising a porous region and a non-porous region, wherein the porous region is at least partially in contact with at least one surface of the membrane;

[0038] 2) A multi-layer structure comprising at least one porous sheet and at least one metal sheet.

[0039] According to a twelfth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to eleventh embodiments,

[0040] The cylindrical secondary battery has a shape factor ratio of 0.25 or more.

[0041] According to a thirteenth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to twelfth embodiments,

[0042] The cylindrical secondary battery is a 18650 battery cell, a 21700 battery cell, a 46110 battery cell, a 48750 battery cell, a 48110 battery cell, a 48800 battery cell or a 46800 battery cell.

[0043] According to a fourteenth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to thirteenth embodiments,

[0044] The cylindrical secondary battery is a battery having a jointless structure that does not include an electrode joint.

[0045] According to a fifteenth embodiment of the present disclosure, there is provided a cylindrical secondary battery as defined in any one of the first to fourteenth embodiments,

[0046] The cylindrical secondary battery includes a liquid electrolyte.

[0047] According to a sixteenth embodiment of the present disclosure, there is provided a method for manufacturing a cylindrical secondary battery, the method including the following steps:

[0048] Prepare positive electrode, negative electrode and separator;

[0049] stacking the separator at least once in a manner that the separator is interposed between the positive electrode and the negative electrode, thereby forming an electrode-separator stack;

[0050] Winding the electrode-separator stack in one direction to form a jellyroll electrode assembly;

[0051] Allowing the electrode assembly to be received in a can, and injecting an electrolyte into the can receiving the electrode assembly;

[0052] sealing the open end of the can to obtain a battery; and

[0053] The battery is activated at room temperature and ambient pressure.

[0054] The positive electrode is provided with a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is provided on at least one surface of the positive electrode current collector and contains a positive electrode active material, and

[0055] The negative electrode includes a negative electrode current collector but does not have a negative electrode active material layer.

[0056] Beneficial Effects

[0057] The cylindrical secondary battery according to the present disclosure includes a negative electrode having no negative electrode active material layer, and thus may provide a secondary battery having increased energy density.

[0058] According to the present disclosure, a cylindrical secondary battery is economical because it can provide a high energy density per unit volume even if a relatively low energy density and inexpensive positive electrode active material is applied to the positive electrode.

[0059] Furthermore, according to the present disclosure, even in a large cylindrical secondary battery with an increased volume, it is possible to effectively reduce heat dissipation inside the cylindrical secondary battery and achieve excellent safety.

[0060] The method for manufacturing a cylindrical secondary battery according to the present disclosure is convenient in terms of process because a pressurizing step for activating the secondary battery can be omitted. BRIEF DESCRIPTION OF THE DRAWINGS

[0061] The accompanying drawings illustrate preferred embodiments of the present disclosure and, together with the foregoing disclosure, are used to provide a further understanding of the technical features of the present disclosure. Therefore, the present disclosure is not to be construed as being limited to the accompanying drawings.

[0062] Figure 1 A stacked state of an electrode assembly provided in a cylindrical secondary battery according to an embodiment of the present disclosure before winding is illustrated.

[0063] Figure 2 is a cross-sectional view showing a cylindrical battery having a jointless structure according to an embodiment of the present disclosure.

[0064] Figure 3 is a cross-sectional view showing a cylindrical battery having a jointless structure according to another embodiment of the present disclosure.

[0065] Figure 4 The structure of a jelly jelly-type electrode assembly provided in a cylindrical secondary battery according to an embodiment of the present disclosure is illustrated.

[0066] Figure 5is a graph showing initial charge and discharge test results of a cylindrical secondary battery according to each of Examples 1 and 2 and Comparative Example 1.

[0067] Figure 6 is a graph showing the determination results of the lifespan and coulombic efficiency of the cylindrical secondary battery according to each of Examples 1 and 2 and Comparative Example 1.

[0068] Figure 7 is a graph showing the evaluation results of hot box safety of the cylindrical secondary battery according to Example 1. DETAILED DESCRIPTION

[0069] Hereinafter, the preferred embodiments of the present disclosure will be described in detail with reference to the accompanying drawings. Before the description, it should be understood that the terms used in the specification and the appended claims should not be interpreted as limited to the general and dictionary meanings, but are interpreted based on the meanings and concepts corresponding to the technical aspects of the present disclosure based on the principle of allowing the inventor to appropriately define the terms for the best interpretation. Therefore, the descriptions presented herein are only preferred embodiments for illustrative purposes and are not intended to limit the scope of the present disclosure, so it should be understood that other equivalents and modifications may be made thereto without departing from the scope of the present disclosure.

[0070] Throughout the specification, the expression "a certain part includes a certain element" does not exclude the existence of any additional element, but means that the part may further include other elements unless otherwise specified.

[0071] As used herein, the expression "A and / or B" means "A, B, or both of them."

[0072] The inventors of the present disclosure have conducted many studies to develop high-quality large cylindrical batteries and have found that it is possible to ensure the safety of large cylindrical batteries and provide high energy density and improved battery performance by using a negative electrode without a negative electrode active material layer. The present disclosure is based on this finding.

[0073] In one aspect of the present disclosure, there is provided a cylindrical secondary battery, the cylindrical secondary battery comprising:

[0074] 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 configured to receive the electrode assembly; and a sealing body configured to seal an open end of the battery can,

[0075] The positive electrode is provided with a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is provided on at least one surface of the positive electrode current collector and contains a positive electrode active material.

[0076] The negative electrode includes a negative electrode current collector but does not have a negative electrode active material layer.

[0077] Electrode assembly

[0078] The electrode assembly includes a positive electrode, a negative electrode, and a separator interposed between the positive electrode and the negative electrode. The electrode assembly may be a jelly-roll type electrode assembly having a structure wound in one direction.

[0079] Figure 1 2 shows a stacking structure of an electrode assembly before winding provided in a cylindrical secondary battery according to an embodiment of the present disclosure. Figure 1 The electrode assembly A provided in the cylindrical secondary battery according to the embodiment of the present disclosure can be obtained by stacking the separator 12, the positive electrode 10, the separator 12 and the negative electrode 11 in sequence at least once to form an electrode-separator stack, and winding the electrode-separator stack along one direction X.

[0080] Specifically, Figure 4 2 shows the structure of a jellyroll-type electrode assembly provided in a cylindrical secondary battery according to an embodiment of the present disclosure. Figure 4 , the separator 12, the positive electrode 10, the separator 12 and the negative electrode 11 are stacked in sequence, wherein the positive electrode 10 includes a positive electrode active material layer 10b located on both surfaces of the positive electrode collector 10a, and the negative electrode 11 only includes the negative electrode collector, thereby forming a core-wound electrode assembly.

[0081] Herein, the negative electrode has a structure in which an active material layer is not formed, and the positive electrode has a structure including an active material layer formed on an elongated sheet-like current collector, and may include a non-coating portion having no active material layer in a partial region of the current collector. Preferably, the non-coating portion of the positive electrode may be formed longitudinally at one end of the current collector along the winding direction X. When a negative electrode having no active material layer and a positive electrode having a non-coating portion formed at one end of the current collector along the winding direction X are used, a battery having a jointless structure may be realized.

[0082] Specifically, a battery with a jointless structure can be obtained by the following method. First, the separator, the positive electrode, the separator and the negative electrode are stacked in sequence, and then the resulting stack is wound in one direction to obtain a core-wound electrode assembly. Then, the non-coating portion 22 of the positive electrode is bent toward the core, the current collector is welded and bonded to each of the non-coating portion of the positive electrode and the non-coating portion of the negative electrode, and the current collector is connected to the electrode terminal, thereby providing a battery with a jointless structure. At the same time, since the current collector has a larger cross-sectional area than the strip electrode joint, and the resistance is proportional to the cross-sectional area of ​​the path through which the current flows, a secondary battery formed with such a structure can provide a significantly reduced cell resistance.

[0083] Hereinafter, each constituent element of an electrode assembly provided in a cylindrical secondary battery according to an embodiment of the present disclosure will be described in detail.

[0084] (1) Positive electrode

[0085] The positive electrode may have a structure including a positive electrode active material layer formed on at least one surface of an elongated sheet-shaped positive electrode collector, wherein the positive electrode active material layer may include a positive electrode active material, a conductive material, and a binder.

[0086] Specifically, the positive electrode can be obtained by dispersing the positive electrode active material, the conductive material and the binder in a solvent (such as dimethyl sulfoxide (DMSO), isopropanol, N-methylpyrrolidone (NMP), acetone, water, etc.) to prepare a positive electrode slurry, applying the positive electrode slurry to one surface or both surfaces of the elongated sheet-shaped positive electrode collector, removing the solvent of the positive electrode slurry through a drying step, and pressing. At the same time, when applying the positive electrode slurry, by not applying the positive electrode slurry in a partial area of ​​the positive electrode (such as one end of the positive electrode collector), a positive electrode including a non-coating portion can be obtained.

[0087] The positive electrode active material may include lithium iron phosphate (LiFePO 4 Specifically, the positive electrode active material may be lithium iron phosphate (LiFePO 4 ).

[0088] When lithium iron phosphate is used as the positive electrode active material, the irreversibility of the negative electrode can be compensated during the activation of the lithium secondary battery, and the safety of the lithium secondary battery can be enhanced by acting as a resistor during the subsequent charge / discharge. In addition, lithium iron phosphate is cheaper than lithium nickel cobalt manganese oxide, which is a commonly used positive electrode active material, and thus provides an advantage in price competitiveness.

[0089] However, according to the present disclosure, the positive electrode active material is not limited to lithium iron phosphate, and any material can be used as the positive electrode active material as long as the material can be conventionally used as the positive electrode active material. Typical embodiments of the positive electrode active material 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), over-lithium oxide (OLO), cobalt-free oxide, nickel-free oxide, manganese-free oxide, manganese-rich oxide or a mixture thereof.

[0090] Meanwhile, when lithium iron phosphate is used as a positive electrode active material, there is a problem that the secondary battery exhibits a relatively low energy density. Therefore, the inventors of the present disclosure designed and completed the present disclosure so that the secondary battery can have a high level of energy density even when lithium iron phosphate is used.

[0091] In the cylindrical secondary battery according to the present disclosure, the negative electrode does not include a negative electrode active material layer. In addition, the cylindrical secondary battery may further include an additional amount of positive electrode active material in the volume generated by not including the negative electrode active material. For example, since the cylindrical secondary battery may further include about 40% of positive electrode active material in the volume generated by not including the negative electrode active material layer, it may have a higher energy density than a battery including a conventional negative electrode provided with a negative electrode active material layer.

[0092] According to an embodiment of the present disclosure, the loading amount of the positive electrode may be equivalent to 110% to 120% of the loading amount of the positive electrode of the cylindrical secondary battery having the negative active material layer.

[0093] In addition, according to an embodiment of the present disclosure, the thickness of the positive electrode may correspond to 110% to 120% of the thickness of the positive electrode of the cylindrical secondary battery having the negative active material layer.

[0094] Specifically, the positive electrode loading can be 500 mg / cm 2 Up to 600mg / cm 2 、520mg / cm 2 Up to 580mg / cm 2 , or 540mg / cm 2 Up to 560mg / cm 2 .

[0095] In addition, specifically, the thickness of the positive electrode may be 190 μm to 220 μm, 200 μm to 220 μm, or 200 μm to 210 μm.

[0096] When the positive electrode has the above-defined loading amount and / or thickness range, there are advantages in that a cylindrical secondary battery can achieve higher capacity and energy, and lithium ion transportability can be enhanced to provide improved life characteristics.

[0097] According to the present disclosure, the term "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.

[0098] In addition, according to the present disclosure, the expression "a cylindrical secondary battery provided with a negative electrode active material layer" is different from the cylindrical secondary battery according to the present disclosure only in that it is provided with a negative electrode active material layer. Generally, the negative electrode active material layer may include a negative electrode active material and a binder polymer commonly used in cylindrical secondary batteries, and the negative electrode active material layer is not particularly limited in the present disclosure.

[0099] Typically, a cylindrical battery includes a cylindrical battery can, in which a core-wound electrode assembly is received, the electrode assembly including a sheet-like positive electrode plate, a separator, and a negative electrode plate stacked in sequence. Since the cylindrical secondary battery according to the present disclosure is not provided with a negative electrode active material layer, the thickness of the negative electrode active material layer inside the battery can can generate additional space compared to a conventional cylindrical secondary battery provided with a negative electrode active material layer. Typically, in a cylindrical secondary battery including a negative electrode plate provided with a negative electrode active material layer, the loading amount of the positive electrode is about 400 mg / cm 2 Up to 500mg / cm 2 , and the thickness is about 150 μm to 180 μm. Therefore, compared with the loading amount and thickness of the positive electrode suggested according to the present disclosure, this cylindrical secondary battery exhibits a lower loading amount and a smaller thickness.

[0100] Therefore, according to the present disclosure, by increasing the loading amount and / or thickness of the positive electrode active material layer using the additional space generated by not including the negative electrode active material layer, beneficial effects in terms of capacity and energy may be achieved.

[0101] According to the embodiment of the present disclosure, in addition to lithium iron phosphate (LiFePO 4 In addition to LFP, the positive electrode active material may also include a positive electrode active material conventionally used in secondary batteries, such as the above-mentioned positive electrode active materials LCO, NCM, NCA, NCAM, LMO or OLO. Specific examples of positive electrode active materials conventionally used in secondary batteries may include: layered compounds, such as lithium cobalt oxide (LiCoO 2 ) and lithium nickel oxide (LiNiO 2 ), or those compounds substituted by one or more transition metals; lithium manganese oxides, such as those of the formula Li 1+x Mn 2-x O 4 (where x is 0 to 0.33), LiMnO 3 、LiMn 2 O 3 and LiMnO 2 Those lithium manganese oxides; lithium copper oxide (Li 2 CuO 2 ); Vanadium oxides, such as LiV 3 O 8 , LiV 3 O 4 、V 2 O 5 Cu 2 V 2 O 7 ; By chemical formula LiNi 1-x M x O 2(wherein M is at least one selected from the group consisting of Co, Mn, Al, Cu, Fe, Mg, B and Ga, and x is 0.01 to 0.9); a lithium nickel oxide represented by the chemical formula LiMn 2-x M x O 2 (wherein M is Co, Ni, Fe, Cr, Zn or Ta, and x is 0.01 to 0.1) or Li 2 Mn 3 MO 8 (wherein M is Fe, Co, Ni, Cu or Zn) represented by lithium manganese composite oxide; LiMn 2 O 4 , where Li is partially replaced by aluminum ions; disulfide; Fe 2 (MoO 4 ) 3 However, the scope of the present disclosure is not limited thereto.

[0102] The positive electrode active material may be present in an amount of 80 to 99 parts by weight, 85 to 99 parts by weight, or 90 to 99 parts by weight based on 100 parts by weight of the total weight of the positive electrode active material layer.

[0103] At the same time, the positive current collector may include various positive current collectors used in the art. Specific embodiments of the positive current collector include stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc. The positive current collector may generally have a thickness of 3 μm to 500 μm, and fine surface irregularities may be formed on the surface of the current collector to enhance the adhesion of the electrode active material. Current collectors of various shapes may be used, including films, sheets, foils, nets, porous bodies, foams, nonwoven fabrics, etc.

[0104] Conductive materials are used to impart conductive properties to the electrode, and any conductive material can be used without particular limitation, as long as the conductive material has electronic conductivity and does not cause any chemical changes in the corresponding battery. Specific embodiments of conductive materials include: graphite, such as natural graphite or artificial graphite; carbonaceous materials, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber or carbon nanofiber; metal powder or metal fiber, such as copper, nickel, aluminum or silver; conductive whiskers, such as zinc oxide or potassium titanate; conductive metal oxides, such as titanium dioxide; conductive polymers, such as polyphenylene derivatives, etc. Such conductive materials can be used alone or in combination. Typically, the amount of the conductive material used can be 1wt% to 30wt%, preferably 1wt% to 20wt%, and more preferably 1wt% to 10wt%, based on the total weight of the positive electrode active material layer.

[0105] The binder is used to achieve adhesion between the positive active materials and to improve the adhesion between the positive active materials and the positive current collector. Specific embodiments of the binder may include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl pyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene monomer rubber (EPDM rubber), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, various copolymers thereof, etc. These binders may be used alone or in combination. Based on the total weight of the positive active material layer, the amount of the binder is 1wt% to 30wt%, preferably 1wt% to 20wt%, and more preferably 1wt% to 10wt%.

[0106] (2) Negative electrode

[0107] The negative electrode includes a negative electrode current collector, and no negative electrode active material layer is formed on any surface of the negative electrode current collector. Specifically, the negative electrode may include only the negative electrode current collector. Since the negative electrode is not provided with a negative electrode active material layer, compared with the negative electrode including the negative electrode active material layer, the advantages are that the processing and manufacturing time and cost are reduced, and the price of the battery is reduced, and the battery can have an increased energy density.

[0108] The negative electrode current collector may include a negative electrode current collector commonly used in the art. Specific embodiments of the negative electrode current collector include: 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 generally have a thickness of 3 μmm to 500 μmm, and similar to the positive electrode current collector, fine surface irregularities may be formed on the surface of the current collector. Current collectors of various shapes may be used, including films, sheets, foils, nets, porous bodies, foams, non-woven fabrics, etc.

[0109] According to an embodiment of the present disclosure, the negative electrode current collector may have the following structure 1) or 2):

[0110] 1) a structure comprising a porous region and a non-porous region, wherein the porous region is at least partially in contact with at least one surface of the membrane; and

[0111] 2) A multi-layer structure comprising at least one porous sheet and at least one metal sheet.

[0112] When the negative electrode collector has the structure of 1), the non-porous region of the negative electrode collector may be located at a central portion of the negative electrode collector.

[0113] In addition, the negative electrode current collector may have a porosity of 30% to 80%. When the negative electrode current collector has the above-defined porosity range, an electrodeposition space may be formed when lithium is electrodeposited from the positive electrode to the negative electrode, so that the cylindrical secondary battery sealed in the battery can undergoes little volume change and is stably charged / discharged.

[0114] As used herein, the term "porosity" refers to a volume ratio occupied by pores based on the total volume of an object to be tested, expressed in vol%, and may be used interchangeably with terms such as pore ratio, porosity, and the like.

[0115] Meanwhile, when the negative electrode current collector has the multi-layer structure of 2), it may have a sandwich structure including a metal sheet between two porous sheets, wherein the porous sheets may have a porosity of 30% to 80%.

[0116] The porous sheet may include: copper; stainless steel; aluminum; nickel; titanium; calcined carbon; copper or stainless steel surface-treated with carbon, nickel, titanium, silver, chromium, etc.; aluminum-cadmium alloy; or two or more thereof.

[0117] The metal sheet may include lithium, a lithium alloy, or a mixture thereof.

[0118] The metal sheet may have a thickness of 0.1 μm to 10 μm. The metal sheet having the above-defined thickness range is preferred because it provides a suitable level of energy density and is economical.

[0119] (3) Diaphragm

[0120] The separator separates the negative electrode and the positive electrode from each other and provides a lithium ion migration channel, and any separator conventionally used for lithium secondary batteries can be used without particular limitation. Specifically, the separator that can be used includes a porous polymer film made of a polymer based on polyolefin (such as ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer or ethylene / methacrylate copolymer), or a laminated structure including two or more layers thereof. In addition, the conventional porous nonwoven fabric used in the art can be used, such as a nonwoven fabric including glass fiber, polyethylene terephthalate fiber, etc. with a high melting point. In addition, in order to ensure heat resistance or mechanical strength, a coated separator including a ceramic component or a polymer material can be used.

[0121] According to another embodiment of the present disclosure, the separator may further include a porous coating layer on at least one surface thereof, the porous coating layer including inorganic particles and a binder polymer.

[0122] In the porous coating layer, inorganic particles are bonded to each other via the binder polymer while they are piled up and in contact with each other, thereby forming interstitial volumes between the inorganic particles, and the interstitial volumes between the inorganic particles become empty spaces to form pores.

[0123] The inorganic particles used to form the porous coating layer may include those inorganic particles that do not cause oxidation and / or reduction reactions within the operating voltage range of the electrochemical device (e.g., 0V to 5V based on Li / Li+). Specifically, when inorganic particles with ion transportability are used, the ionic conductivity in the electrochemical device can be enhanced and its performance can be improved. In addition, when inorganic particles with a high dielectric constant are used, they help to increase the degree of dissociation of electrolyte salts (especially lithium salts) in liquid electrolytes, thereby improving the ionic conductivity of the electrolyte.

[0124] For these reasons, the inorganic particles may preferably include inorganic particles having a dielectric constant of 5 or more (preferably 10 or more), inorganic particles having lithium ion transportability, or a mixture thereof.

[0125] Non-limiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO 3 、Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB(Mg 1 / 3 Nb 2 / 3 ) 3 -PbTiO 3 (PMN-PT), hafnium oxide (HfO 2 )、SrTiO 3 SnO 2 、CeO 2 , MgO, NiO, CaO, ZnO, ZrO 2 , Y 2 O 3 、Al 2 O 3 、TiO 2 , SiC or a mixture thereof.

[0126] Specifically, such as BaTiO 3 、Pb(Zr,Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), PB(Mg 1 / 3 Nb 2 / 3 ) 3 -PbTiO 3 (PMN-PT) and hafnium oxide (HfO 2Inorganic particles such as those described above not only exhibit a high dielectric constant of over 100, but also possess piezoelectricity. By virtue of this piezoelectricity, when subjected to a predetermined level of pressing, charges are generated during elongation or compression, thereby creating a potential difference between two surfaces. As a result, an internal short circuit between two electrodes caused by an external impact can be prevented, thus providing an electrochemical device with improved safety. Additionally, when inorganic particles with a high dielectric constant are used in combination with inorganic particles having lithium-ion transportability, their synergistic effect can be enhanced.

[0127] Inorganic particles having lithium-ion transportability refer to inorganic particles that contain lithium elements but do not store lithium and have the function of transporting lithium ions. Inorganic particles having lithium-ion transportability can utilize the defects present in the particle structure to transport and conduct lithium ions, thereby improving the lithium-ion conductivity in a battery and providing improved performance for the battery. Non-limiting examples of inorganic particles having lithium-ion transportability include: lithium phosphate (Li 3 PO 4 ); lithium titanium phosphate (Li x Ti y (PO 4 ) 3 , 0 < x < 2, 0 < y < 3); lithium aluminum titanium phosphate (Li x Al y Ti z (PO 4 ) 3 , 0 < x < 2, 0 < y < 1, 0 < z < 3); (LiAlTiP) x O y -based glass (1 < x < 4, 0 < y < 13), such as 14Li 2 O - 9Al 2 O 3 - 38TiO 2 - 39P 2 O 5 ; lithium lanthanum titanate (Li x La y TiO 3 , 0 < x < 2, 0 < y < 3); lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), such as Li 3.25 Ge 0.25 P 0.75 S 4 ; lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), such as Li 3 N; SiS 2Base glass (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), such as Li 3 PO 4 -Li 2 S-SiS 2 ; and P 2 S 5 -base glass (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), such as LiI-Li 2 S-P 2 S 5 or a mixture thereof.

[0128] Although the particle size of the inorganic particles in the porous coating layer is not particularly limited, the inorganic particles preferably may have a particle size of 0.001 μm to 10 μm in order to form a coating layer with a uniform thickness and provide a suitable porosity. When the particle size is less than 0.001 μm, the dispersibility of the inorganic particles decreases. When the particle size is greater than 10 μm, the porous coating layer may have an increased thickness, resulting in a decrease in mechanical properties. In addition, due to the too large pore size, there is a high probability of internal short circuit during battery charging / discharging.

[0129] The binder polymer for forming the porous coating layer may include any one or more than two binder polymers selected from the group consisting of: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-HFP); polyvinylidene fluoride-trichloroethylene copolymer; polymethyl methacrylate; polybutyl acrylate; polyacrylonitrile; polyvinylpyrrolidone; polyvinyl acetate; polyethylene-vinyl acetate copolymer; poly(ethylene oxide); polyarylate; cellulose acetate; cellulose acetate butyrate; cellulose acetate propionate; cyanoethyl pullulan; cyanoethyl polyvinyl alcohol; cyanoethyl cellulose; cyanoethyl sucrose; pullulan; and carboxymethyl cellulose. However, the scope of the present disclosure is not limited thereto.

[0130] For example, the ratio of inorganic particles to binder polymers used in the porous coating layer may preferably be 50:50 to 99:1, more preferably 70:30 to 95:5. When the content ratio of inorganic particles to binder polymers is less than 50:50, the content of binder polymers increases, resulting in reduced thermal safety of the separator. In addition, the empty space formed between the inorganic particles is reduced, resulting in reduced pore size and reduced porosity, resulting in reduced performance of the finished battery. When the content of inorganic particles is greater than 99 parts by weight, such a low content of binder polymers may result in reduced peeling resistance of the porous coating layer. Although the thickness of the porous coating layer is not particularly limited, the porous coating layer may preferably have a thickness of 0.01 μm to 20 μm. In addition, the pore size and porosity are not particularly limited, but preferably the pore size is 0.001 μm to 10 μm and the porosity is 10% to 90%. The pore size and porosity depend mainly on the size of the inorganic particles. For example, when inorganic particles having a particle size of 1 μm or less are used, the pores formed between the inorganic particles also exhibit a size of 1 μm or less. This pore structure is filled with an electrolyte that is subsequently injected, and the filled electrolyte is used to transport ions. When the pore size and porosity are less than 0.001 μm and 10%, respectively, the porous coating layer can be used as a resistance layer. When the pore size and porosity are greater than 10 μm and 90%, respectively, the mechanical properties may be reduced.

[0131] The porous coating layer can be formed in the following manner: the binder polymer is dissolved or dispersed in a dispersion medium, inorganic particles are added thereto to obtain a slurry for forming a porous coating layer, and the slurry is coated on at least one surface of the substrate, and then dried. The solubility parameter of the dispersion medium is preferably similar to the solubility parameter of the binder polymer to be used, and the dispersion medium has a low boiling point. This is because this dispersion medium helps to uniformly mix and remove the dispersion medium subsequently. The non-limiting embodiments of the usable dispersion medium include acetone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, N-methyl-2-pyrrolidone (NMP), cyclohexane, water or its mixture.

[0132] After the inorganic particles are added to the dispersion (the dispersion includes a binder polymer dispersed in the dispersion medium), the inorganic particles are preferably pulverized. In this article, the pulverization time is suitably 1 to 20 hours, and the particle size of the inorganic particles after pulverization is preferably 0.001 μm to 10 μm (as described above). Any conventional pulverization process can be used, and ball milling is particularly preferred.

[0133] Then, the binder polymer dispersion containing inorganic particles dispersed therein is coated on at least one surface of the porous polymer substrate at a humidity of 10% to 80%, and then dried. Any conventional coating process known to those skilled in the art can be used to coat the dispersion on the porous polymer substrate, and specific embodiments of the process can include various processes such as dip coating, die coating, roller coating, comma coating, and combinations thereof.

[0134] In addition to the above-mentioned inorganic particles and binder polymer, the porous coating layer may further include other additives such as a conductive material.

[0135] The finished separator according to the present disclosure may have a thickness of 1 μm to 100 μm or 5 μm to 50 μm. When the thickness is less than 1 μm, the separator cannot fully realize the function of the separator, and the mechanical properties may deteriorate. When the thickness is greater than 100 μm, the battery performance may deteriorate during high-rate charge / discharge. In addition, the separator may have a porosity of 40% to 60% and an air permeability of 150 to 300 seconds / 100 mL.

[0136] Cylindrical lithium secondary battery

[0137] Hereinafter, a cylindrical lithium secondary battery according to the present disclosure will be described in detail.

[0138] A cylindrical battery according to the present disclosure 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 configured to receive the electrode assembly; and a sealing body configured to seal an open end of the battery can.

[0139] The cylindrical lithium secondary battery according to the present disclosure may be a cylindrical battery having a shape factor ratio (a value calculated by dividing the diameter of the cylindrical battery by its height, i.e., a ratio of diameter (φ) to height (H)) of 0.25 or more or 0.4 or more. Herein, the term "shape factor" refers to a value representing the diameter and height of a cylindrical battery.

[0140] For example, the cylindrical battery according to the present disclosure can be a 18650 battery cell (diameter 18mm, height 65mm, shape factor ratio 0.277), a 21700 battery cell (diameter 21mm, height 70mm, shape factor ratio 0.300), a 46110 battery cell (diameter 46mm, height 110mm, shape factor ratio 0.418), a 48750 battery cell (diameter 48mm, height 75mm, shape factor ratio 0.640), a 48110 battery cell (diameter 48mm, height 110mm, shape factor ratio 0.418), a 48800 battery cell (diameter 48mm, height 80mm, shape factor ratio 0.600) or a 46800 battery cell (diameter 46mm, height 80mm, shape factor ratio 0.575). In the number representing the shape factor, the first two digits represent the diameter of the battery cell, the next two digits represent the height of the battery cell, and the last digit 0 represents the circular cross-section of the battery cell.

[0141] The cylindrical lithium secondary battery according to the present disclosure includes a negative electrode without a negative electrode active material layer, and thus can exhibit a high energy density per unit volume. According to an embodiment of the present disclosure, based on the capacity of a cylindrical secondary battery provided with a negative electrode active material, the cylindrical lithium secondary battery according to the present disclosure can provide a capacity increased by 140% to 180%. Specifically, the cylindrical lithium secondary battery according to the present disclosure can provide an energy density of 850 or 900Wh / L or more. The capacity can be calculated by multiplying the design capacity of the corresponding secondary battery by its average voltage and then dividing it by the volume of the corresponding battery size.

[0142] In addition, the cylindrical lithium secondary battery according to the present disclosure can achieve excellent safety even in a cylindrical battery with a shape factor ratio of 0.25 or 0.4 or more. Specifically, when the negative electrode active material layer is not included, after charging, the negative electrode undergoes deposition in the form of lithium metal. However, according to the present disclosure, the gas can be easily discharged in a predetermined direction, which is beneficial to thermal safety.

[0143] Meanwhile, the cylindrical battery according to the present disclosure may be a battery having a jointless structure, ie, preferably having no electrode joints. However, the scope of the present disclosure is not limited thereto.

[0144] For example, a battery having a jointless structure may have a structure in which each of the positive electrode and the negative electrode includes a non-coating portion having no active material layer, each of the positive electrode non-coating portion and the negative electrode non-coating portion is disposed at each of the top end and the bottom end of the electrode assembly, a current collecting plate is coupled to each of the positive electrode non-coating portion and the negative electrode non-coating portion, and the current collecting plate is connected to the electrode terminal.

[0145] Figure 2 is a cross-sectional view showing a cylindrical battery having a jointless structure according to an embodiment of the present disclosure. Figure 2 A cylindrical battery according to an embodiment of the present disclosure is described. However, Figure 2 Only embodiments of the present disclosure are shown, and the structure of the cylindrical battery according to the present disclosure is not limited to Figure 2 The scope disclosed in.

[0146] The cylindrical battery 140 according to an embodiment of the present disclosure includes the above-described jellyroll type electrode assembly 141 , a battery can 142 configured to receive the electrode assembly 141 , and a sealing body 143 configured to seal an open end of the battery can 142 .

[0147] Herein, each of the positive electrode and the negative electrode of the electrode assembly may include a non-coating portion having no active material layer, and may be stacked and wound in such a manner that the positive electrode non-coating portion and the negative electrode non-coating portion may be disposed at the top and bottom ends of the electrode assembly, respectively. The electrode assembly is described above, and thus constituent elements other than the electrode assembly will be described below.

[0148] The battery can 142 is a cylindrical container having an opening at the top and includes a conductive metal material such as aluminum or steel. The battery can receives the electrode assembly 141 and an electrolyte (not shown) in its inner space via the top opening.

[0149] The electrolyte usable herein includes various electrolytes suitable for lithium secondary batteries, and specific examples thereof include liquid electrolytes, solid polymer electrolytes, gel polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited thereto.

[0150] Specifically, the electrolyte may be a liquid electrolyte and may include an organic solvent and a lithium salt.

[0151] Any organic solvent can be used without particular limitation, as long as it can be used as a medium through which ions participating in the electrochemical reaction of the battery can pass. For example, the organic solvent may include esters, ethers, imides, linear carbonates, cyclic carbonates, etc., and may be used alone or in combination.

[0152] Specific examples of esters as organic solvents may include any one or a mixture of two or more 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. However, the scope of the present disclosure is not limited thereto.

[0153] Specific examples of ethers as organic solvents may include: linear ether compounds such as dimethyl ether, ethyl 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, butanediol ether, diethylene glycol ethyl methyl ether, diethylene glycol isopropyl methyl ether, diethylene glycol butyl methyl ether, diethylene glycol tert-butyl ethyl ether, ethylene glycol ethyl methyl ether, and the like; cyclic ethers such as dioxolane, methyl dioxolane, dimethyl dioxolane, vinyl dioxolane, methoxy dioxolane, ethylmethyldioxane, oxane, oxane, trioxane, tetrahydrofuran, methyltetrahydrofuran, dimethyltetrahydrofuran, dimethoxytetrahydrofuran, ethoxytetrahydrofuran, dihydropyran, tetrahydropyran, furan, 2-methylfuran, etc.; fluorinated ether compounds such as 1,1,2,2-tetrafluoroethyl 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 ether, 1H,1H,2'H,3H-decafluorodipropyl ether, 1H,1H,2'H-perfluorodipropyl ether, etc.; or mixtures thereof.

[0154] Any lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions in a lithium secondary battery. Specific examples of lithium salts include LiPF 6 、LiClO 4 、LiAsF 6 , LiBF 4 、LiSbF 6 、LiAlO 4 、LiAlCl 4 、LiCF 3 SO 3 ,LiC 4 F 9 SO 3 、LiN(C 2 F 5 SO 3 ) 2 、LiN(C 2 F 5 SO 2 ) 2 、LiN(CF 3 SO 2 ) 2、LiCl、LiI、LiB(C 2 O 4 ) 2 The lithium salt may be used at a concentration of 0.1 to 5.0 M, preferably 0.1 to 3.0 M. When the lithium salt has the above concentration, the electrolyte may have a suitable conductivity and viscosity level to provide excellent electrolyte performance and allow efficient lithium ion migration.

[0155] In addition to the above-mentioned components forming the electrolyte, the electrolyte may also include additives to improve the life characteristics of the battery, inhibit the reduction of the battery capacity and increase the discharge capacity of the battery. Non-limiting examples of such additives include: halogenated alkylene carbonate compounds, such as difluoroethylene carbonate; pyridine; triethyl phosphite; triethanolamine; cyclic ethers; ethylenediamine; positive polyethers; hexamethylphosphoramide; nitrobenzene derivatives; sulfur; quinone imine dyes; N-substituted oxazolidinones; N, N-substituted imidazolidines; ethylene glycol dialkyl ethers; ammonium salts; pyrroles; 2-methoxyethanol; or aluminum chloride, and such additives may be used alone or in combination. Based on the total weight of the electrolyte, the additive is used in an amount of 0.1wt% to 10wt%, preferably 0.1wt% to 5wt%.

[0156] The battery can 142 is electrically connected to the non-coating portion 146 of the negative electrode plate, and serves as a negative electrode terminal in contact with an external power source to conduct current applied from the external power source to the negative electrode plate.

[0157] If necessary, a curling portion 147 and a crimping portion 148 may be provided at the top end of the battery can 142. The curling portion 147 may be formed by press-fitting the outer circumference of the battery can 142. The curling portion 147 prevents the electrode assembly 141 received in the battery can 142 from escaping through the top opening of the battery can 142, and may serve as a supporting portion for holding the sealing body 143.

[0158] The crimping portion 148 may be formed at the top of the curling portion 147 and take an extended and bent form to surround the outer peripheral surface of the cap plate 143 a disposed on the curling portion 147 and a portion of the top surface of the cap plate 143 a .

[0159] Next, the sealing body 143 is configured to seal the open end of the battery can 142, and includes a cap plate 143a and a first gasket 143b, the first gasket 143b is configured to provide airtightness between the cap plate 143a and the battery can 142 and has insulation performance, and if necessary, may also include a link plate 143c electrically and mechanically coupled to the cap plate 143a. The cap plate 143a is compressed on the curling portion 147 formed in the battery can 142, and can be fixed by means of a crimping portion 148.

[0160] The cap plate 143a is a portion made of a conductive metal and covers the top opening of the battery can 142. The cap plate 143a is electrically connected to the positive plate of the electrode assembly 141 and is electrically insulated from the battery can 142 by means of the first gasket 143b. Therefore, the cap plate 143a can be used as a positive terminal of a cylindrical secondary battery. The cap plate 143a may be provided with a protrusion 143d protruding upward from the center thereof, and the protrusion 143d contacts an external power source so that a current can be applied from the external power source.

[0161] The first gasket 143 b may be interposed between the cap plate 143 a and the crimping portion 148 in order to ensure airtightness of the battery can 142 and to electrically insulate the battery can 142 and the cap plate 143 a from each other.

[0162] Meanwhile, if necessary, the cylindrical battery 140 according to the present disclosure may further include current collecting plates 144, 145. The current collecting plates are coupled to the positive and negative non-coating portions 146a and 146b and connected to electrode terminals (ie, positive and negative terminals).

[0163] Specifically, the cylindrical battery 140 according to the present disclosure may include a first current collecting plate 144 coupled to the top of the electrode assembly 141 and a second current collecting plate 145 coupled to the bottom of the electrode assembly 141 .

[0164] The first current collecting plate 144 is coupled to the top of the electrode assembly 141. The first current collecting plate 144 is made of a conductive metal such as aluminum, copper or nickel, and is electrically connected to the non-coating portion 146a of the positive electrode plate. A lead 149 may be connected to the first current collecting plate 144. The lead 149 extends toward the top of the electrode assembly and may be coupled to the link plate 143c or directly to the bottom surface of the cap plate 143a. The lead 149 may be coupled to other parts 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 an elongated plate-like shape extending outward from the central portion of the first current collecting plate 144.

[0165] Meanwhile, the first current collecting plate 144 is coupled to the end of the non-coating portion 146 a of the positive electrode plate, for example, by a process such as laser welding, resistance welding, ultrasonic welding, brazing, or the like.

[0166] The second current collecting plate 145 is coupled to the bottom of the electrode assembly 141. The second current collecting plate 145 is made of a conductive metal such as aluminum, copper, or nickel, and is electrically connected to the non-coating portion 146b of the negative electrode plate. One surface of the second current collecting plate 145 may be coupled to the non-coating portion 146b of the negative electrode plate, and the other surface may be coupled to the inner bottom surface of the battery can 142. Herein, the coupling may be performed by processes such as laser welding, resistance welding, ultrasonic welding, brazing, and the like.

[0167] Meanwhile, if necessary, the cylindrical battery 140 according to the present disclosure may further include an insulator 146. The insulator 146 may be provided to cover the top surface of the first current collecting plate 144. When the insulator 146 covers the first current collecting plate 144, the first current collecting plate 144 may be prevented from directly contacting the inner circumferential surface of the battery can 142.

[0168] The insulator 146 is provided with a lead hole 151 so that the lead 149 extending upward from the first current collecting plate 144 can be pulled. The lead 149 is pulled upward through the lead hole 151 and coupled to the bottom surface of the link plate 143c or the bottom surface of the cap plate 143a.

[0169] The insulator 146 may include a polymer resin material having insulating properties, such as polyethylene, polypropylene, polyimide, or polybutylene terephthalate.

[0170] Meanwhile, if necessary, the cylindrical battery 140 according to the present disclosure may further include a vent 152 formed on the bottom surface of the battery can. The vent 152 corresponds to a region having a smaller thickness than the surrounding region of the bottom surface of the cylindrical battery 140. Since the vent 152 has a smaller thickness, its structure is weaker than the surrounding region. Therefore, when the internal pressure of the cylindrical battery 140 increases to exceed a predetermined level, the gas inside the battery can can be discharged to the outside while the vent 152 ruptures, thereby preventing the battery from exploding.

[0171] Figure 3 is a cross-sectional view showing a cylindrical battery having a jointless structure according to another embodiment of the present disclosure. Figure 3 A cylindrical battery according to another embodiment of the present disclosure is described. However, Figure 3 Only embodiments of the present disclosure are shown, and the structure of the cylindrical battery according to the present disclosure is not limited to Figure 3 The scope disclosed in.

[0172] refer to Figure 3 According to another embodiment of the present disclosure, a cylindrical battery 170 and Figure 2 The cylindrical battery 140 shown is different in the structure of the battery can and the sealing body, and the configuration of the electrode assembly and the electrolyte are substantially the same as those of the cylindrical battery 140 .

[0173] Specifically, the cylindrical battery 170 includes a battery can 171 through which a riveted terminal 172 penetrates. The riveted terminal 172 is mounted on a closed surface (top surface in the figure) of the battery can 171. The riveted terminal 172 is riveted in a through hole of the battery can 171, in which an insulating second gasket 173 is inserted. The riveted terminal 172 is exposed to the outside in a direction opposite to the direction of gravity.

[0174] The riveted terminal 172 includes a terminal exposure portion 172a and a terminal insertion portion 172b. The terminal exposure portion 172a is exposed to the outside of the closed surface of the battery can 171. The terminal exposure portion 172a may be disposed approximately at the central portion of the closed surface of the battery can 171. The maximum diameter of the terminal exposure portion 172a may be formed to be larger than the maximum diameter of the through hole formed in the battery can 171. The terminal insertion portion 172b passes approximately through the central portion of the closed surface of the battery can 171 and may be electrically connected to the non-coating portion 146a of the positive plate. The terminal insertion portion 172b may be riveted to the inner surface of the battery can 171. In other words, the end of the terminal insertion portion 172b may be bent toward the inner surface of the battery can 171. The maximum diameter of the end of the terminal insertion portion 172b may be larger than the maximum diameter of the through hole of the battery can 171.

[0175] The bottom surface of the terminal insertion portion 172b may be welded to the first current collecting plate connected to the non-coating portion 146a of the positive plate. An insulating cap 174 including 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 top of the first current collecting plate and the top edge portion of the electrode assembly 141. In this way, the non-coating portion on the outer peripheral side of the electrode assembly 141 may be prevented from contacting the inner surface of the battery can 171 of the opposite polarity and causing a short circuit. The terminal insertion portion 172b of the riveted terminal passes through the insulating cap 174 and may be welded to the first current collecting plate 144.

[0176] The second gasket 173 is interposed between the battery can 171 and the rivet terminal 172 to prevent the battery can 171 and the rivet terminal 172, which have opposite polarities, from electrically contacting each other. In this way, the top surface of the battery can 171 having an approximately flat shape can be used as a positive terminal of the cylindrical battery 170.

[0177] The second gasket 173 includes a gasket exposure portion 173a and a gasket insertion portion 173b. The gasket exposure portion 173a is inserted between the terminal exposure portion 172a of the riveted terminal 172 and the battery can 171. The gasket insertion portion 173b is inserted between the terminal insertion portion 172b of the riveted terminal 172 and the battery can 171. The gasket insertion portion 173b is deformed when the terminal insertion portion 172b is riveted so that it can be in close contact with the inner surface of the battery can 171. For example, the second gasket 173 may include a polymer resin having insulating properties.

[0178] The gasket exposed portion 173a of the second gasket 173 may have a form that extends to cover the outer peripheral surface of the terminal exposed portion 172a of the riveted terminal 172. When the second gasket 173 covers the outer peripheral surface of the riveted terminal 172, a short circuit may be prevented from occurring during the bonding of an electrical connection portion such as a bus bar to the top surface of the battery can 171 and / or the riveted terminal 172. Although not shown in the drawings, the gasket exposed portion 173a may have a form that extends to cover a portion of the top surface and the outer peripheral surface of the terminal exposed portion 172a.

[0179] When the second gasket includes a polymer resin, the second gasket 173 may be bonded to the battery can 171 and the riveted terminal 172 by heat fusion. In this case, the bonding interface between the second gasket 173 and the riveted terminal 172 and the bonding surface between the second gasket 173 and the battery can 171 may have enhanced airtightness. Meanwhile, when the gasket exposed portion 173a of the second gasket 173 has a form extending to the top surface of the terminal exposed portion 172a, the riveted terminal 172 may be integrally bonded to the second gasket 173 by insert molding.

[0180] The remaining area 175 excluding the area occupied by the rivet terminal 172 and the second gasket 173 of the top surface of the battery can 171 corresponds to a negative terminal having a polarity opposite to that of the rivet terminal 172 .

[0181] The second current collecting plate 176 is coupled to the bottom of the electrode assembly 141. The second current collecting plate 176 includes a conductive metal such as aluminum, steel, copper, or nickel, and is electrically connected to the non-coating portion 146b of the negative electrode plate.

[0182] 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 inserted and fixed between the inner surface of the battery can 171 and the first gasket 178b. For example, at least a portion of the edge portion of the second current collecting plate 176 may be fixed at the curling portion 180 by welding while being supported on the bottom end surface of the curling portion 180 formed at the bottom 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.

[0183] The second current collecting plate 176 may be provided with a plurality of surface irregularities (not shown) radially formed on a surface facing the non-coating portion 146b. When such surface irregularities are formed, they may be press-fitted into the non-coating portion 146b by pushing the second current collecting plate 176.

[0184] Preferably, the second current collecting plate 176 and the end portions of the non-coating portion 146 b may be coupled to each other by welding such as laser welding.

[0185] The sealing body 178 configured to seal the open bottom end of the battery can 171 includes a cap plate 178a and a first gasket 178b. The first gasket 178b electrically separates the cap plate 178a from the battery can 171. The crimping portion 181 fixes the edge of the cap plate 178a and the first gasket 178b together. The cap plate 178a is provided with a vent 179. The vent 179 has a configuration substantially the same as in the above-described embodiment.

[0186] Preferably, the cap plate 178a is made of a conductive metal. However, since the first gasket 178b is interposed between the cap plate 178a and the battery can 171, the cap plate 178a does not exhibit electrical polarity. The seal 178 is used to seal the open bottom end of the battery can 171 and discharge gas when the internal pressure of the battery cell 170 increases to above a critical value.

[0187] Preferably, the rivet terminal 172 electrically connected to the non-coating portion 146a of the positive electrode plate is used as a positive terminal. In addition, a portion 175 (except the rivet terminal 172) of the top surface of the battery can 171 electrically connected to the non-coating portion 146b of the negative electrode plate via the second current collecting plate 176 is used as a negative terminal.

[0188] In this way, when two electrode terminals are provided at the top of the cylindrical battery, an electrical connection portion such as a bus bar can be provided only on one side of the cylindrical battery 170. This makes it possible to simplify the structure of the battery pack and improve the energy density. In addition, since the portion 175 used as the negative terminal has a substantially flat form, it is possible to ensure that there is sufficient contact area when an electrical connection portion such as a bus bar is combined. Therefore, the cylindrical battery 170 can reduce the resistance at the joint of the electrical connection portion to a desired level.

[0189] When a cylindrical lithium secondary battery is formed to have the above-described tab-less structure, current collection is lower than that of a conventional battery provided with an electrode tab, and thus heat dissipation in the battery can be effectively reduced, thereby providing improved thermal safety for the battery.

[0190] In another aspect of the present disclosure, there is provided a method for manufacturing a cylindrical secondary battery, the method comprising the following steps:

[0191] Prepare positive electrode, negative electrode and separator;

[0192] stacking the separator at least once so that the separator can be interposed between the positive electrode and the negative electrode to form an electrode-separator stack;

[0193] Winding the electrode-separator stack in one direction to form a jellyroll-type electrode assembly;

[0194] allowing the electrode assembly to be received in the can, and injecting an electrolyte into the can receiving the electrode assembly;

[0195] sealing the open end of the can to obtain a battery; and

[0196] The activation of the battery was carried out at room temperature and ambient pressure conditions.

[0197] Each constituent element is the same as described above.

[0198] Specifically, the method according to the present disclosure is characterized in that the battery activation step is performed under conditions of room temperature and ambient pressure.

[0199] In the battery activation step, initial charging is performed to activate the electrode active material and form a solid electrolyte interphase (SEI) film on the electrode surface. Generally, in the battery activation step, gas is inevitably generated inside the battery by decomposition of the electrolyte, etc. Therefore, the gas generated in the battery is usually removed by performing battery activation under predetermined high voltage conditions to activate the battery.

[0200] However, in the cylindrical secondary battery according to the present disclosure, the can outside the winding core is used as the outer wall, so when the volume expands when lithium metal is generated, the can may face pressure and thus pressurize itself. Therefore, since a separate high-pressure condition, especially a pressurization condition using a jig, is not required in the battery activation step, there is a convenience advantage in processing.

[0201] Embodiments will be described more fully below so that the present disclosure can be easily understood. However, the following embodiments can be embodied in many different forms and should not be construed as being limited to the exemplary embodiments set forth in these embodiments. On the contrary, these exemplary embodiments are provided so that the present disclosure will be thorough and complete, and will fully convey the scope of the present disclosure to those skilled in the art.

[0202] Example 1

[0203] First, 97 parts by weight of LiFePO as a positive electrode active material was added. 4 , 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 were mixed, and the resulting mixture was introduced into N-methyl-2-pyrrolidone as a solvent, and then mixed to prepare a positive electrode slurry. The positive electrode slurry was applied to one surface of an aluminum current collector sheet with a thickness of 15 μm and dried at 120°C, and then pressed to prepare a positive electrode with a positive electrode loading of 560 mg / 25 cm 2 And the thickness of the positive electrode plate is 200μm.

[0204] A copper foil with a thickness of 10 μm was prepared as a negative electrode plate.

[0205] The separator is inserted between the positive electrode plate and the negative electrode plate prepared as described above, and the separator / positive electrode plate / separator / negative electrode plate are stacked in the order of separator / positive electrode plate / separator / negative electrode plate, and then the stacked piece is wound to obtain a core-wound electrode assembly. The electrode assembly obtained as described above is inserted into a cylindrical battery can, and an electrolyte is injected therein to obtain a cylindrical secondary battery as a 21700 battery cell.

[0206] Comparative Example 1

[0207] A cylindrical secondary battery as a 21700 cell was obtained in the same manner as in Example 1, except that a negative electrode active material (containing a mixture of graphite and SiO2 at a weight ratio of 95:5), a conductive material (Super C), styrene-butadiene rubber (SBR) and carboxymethyl cellulose (CMC) were mixed in water at a weight ratio of 96:2:1.5:0.5 to prepare a negative electrode slurry. The negative electrode slurry was applied to one surface of a copper foil having a thickness of 10 μm and dried at 150° C., and then pressed to prepare a negative electrode, and a positive electrode plate using the amount of positive electrode active material, positive electrode thickness and positive electrode loading as shown in Table 1 below was prepared.

[0208] Example 2

[0209] A cylindrical secondary battery of 21700 cells was obtained in the same manner as in Example 1, except that a positive electrode plate using the amount of positive electrode active material, positive electrode thickness, and positive electrode loading as shown in Table 1 below was prepared.

[0210] [Table 1]

[0211]

[0212] Test Example

[0213] 1. Charge / discharge capacity

[0214] The cylindrical secondary batteries according to each of Examples 1 and 2 and Comparative Example 1 were charged to 3.9 V in a constant current / constant voltage (CC / CV) mode (cut-off current 0.1 C) at a temperature of 25° C. and a constant current of 0.1 C, and then discharged to 2.5 V in a CC mode. Then, the initial charge / discharge capacity was determined. The results are shown in Figure 5 middle.

[0215] The cylindrical secondary battery according to Comparative Example 1 can accept up to 26 g of positive electrode active material within its operating range. However, when the negative electrode not including the negative electrode active material layer according to each of Examples 1 and 2 is used, the amount of positive electrode active material that can be introduced into the battery cell is increased to maximize the energy density per unit volume. Compared with Comparative Example 1, Examples 1 and 2 exhibit an increase of about 50% in charge capacity and discharge capacity.

[0216] 2. Life test

[0217] In order to determine the life characteristics of the cylindrical secondary batteries according to each of Examples 1 and 2 and Comparative Example 1, the cylindrical secondary batteries were charged to 3.9 V in the 1st cycle under constant current / constant voltage (CC / CV) conditions at a temperature of 25° C. and a constant current of 0.1 C, and then charged in CC mode at 0.1 C. Then, the cylindrical secondary batteries were allowed to stand for 30 minutes and discharged to 2.5 V at 0.1 C, and the discharge capacity was determined.

[0218] Subsequent charge / discharge cycles were repeated at 0.1C in the voltage range of 3.9 to 2.5 V up to the 25th cycle, and the discharge capacity retention was determined for each cycle. The results are shown in Figure 6 It can be seen that compared with Comparative Example 1, Examples 1 and 2 exhibit higher charge and discharge capacities, while providing a capacity retention rate at a comparable level to Comparative Example 1.

[0219] 3. Hot box test

[0220] In order to determine the safety of the cylindrical secondary battery according to Example 1, a hot box test was performed. The hot box test includes introducing a charged battery into a chamber capable of convection and measuring the cell temperature of the secondary battery while increasing the temperature to 130°C at a heating rate of 5°C / min, maintaining the temperature for 30 minutes, increasing the temperature to 200°C at a heating rate of 5°C / min and maintaining the temperature for 1 hour. The results are shown in Figure 7 middle.

[0221] After performing a hot box test, it turned out that the cylindrical secondary battery according to Example 1 maintained its temperature at 130° C. for about 30 minutes and at about 200° C. for about 1 hour. This is at a level similar to the hot box test result of a cylindrical secondary battery with a negative electrode coating layer, which shows that Example 1 can ensure excellent safety at a level comparable to that of a battery with a negative electrode coating layer despite the absence of a negative electrode coating layer.

Claims

1. A cylindrical secondary battery, comprising: 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 configured to receive the electrode assembly; and a sealing body configured to seal an open end of the battery can, The positive electrode is provided with a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is provided on at least one surface of the positive electrode current collector and contains a positive electrode active material, and The negative electrode includes a negative electrode current collector but does not have a negative electrode active material layer.

2. The cylindrical secondary battery according to claim 1, wherein: The negative electrode includes only the negative electrode current collector.

3. The cylindrical secondary battery according to claim 1, wherein: The positive electrode active material includes lithium iron phosphate (LFP), lithium iron manganese 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), over-lithium oxide (OLO), cobalt-free oxide, nickel-free oxide, manganese-free oxide, manganese-rich oxide or a mixture thereof.

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

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

6. The cylindrical secondary battery according to claim 1, wherein The positive electrode loading is 500 mg / cm 2 Up to 600mg / cm 2 .

7. The cylindrical secondary battery according to claim 1, wherein: The thickness of the positive electrode is 110% to 120% relative to the thickness of the positive electrode of the cylindrical secondary battery having the negative electrode active material layer.

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

9. The cylindrical secondary battery according to claim 1, wherein: The capacity of the cylindrical secondary battery is increased by 140% to 180% relative to the capacity of a cylindrical secondary battery having a negative electrode active material layer.

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

11. 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 the porous region is at least partially in contact with at least one surface of the membrane; and 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 shape factor ratio of 0.25 or more.

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

14. The cylindrical secondary battery according to claim 1, wherein The cylindrical secondary battery is a battery having a jointless structure that does not include an electrode joint.

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

16. A method for manufacturing a cylindrical secondary battery, the method comprising the following steps: Prepare positive electrode, negative electrode and separator; stacking the separator at least once in such a manner that the separator is interposed between the positive electrode and the negative electrode, thereby forming an electrode-separator stack; Winding the electrode-separator stack in one direction to form a jellyroll electrode assembly; Allowing the electrode assembly to be received in a can, and injecting an electrolyte into the can receiving the electrode assembly; sealing the open end of the can to obtain a battery; and The battery is activated at room temperature and ambient pressure. The positive electrode is provided with a positive electrode current collector and a positive electrode active material layer, wherein the positive electrode active material layer is provided on at least one surface of the positive electrode current collector and contains a positive electrode active material, and The negative electrode includes a negative electrode current collector but does not have a negative electrode active material layer.

Images