CN118235279A

CN118235279A - Wound electrode assembly, method for manufacturing the same, and secondary battery including the same

Info

Publication number: CN118235279A
Application number: CN202380014433.XA
Authority: CN
Inventors: 具圣谟; 金英洙; 李菅秀; 李炳俊
Original assignee: LG Energy Solution Ltd
Current assignee: LG Energy Solution Ltd
Priority date: 2022-09-26
Filing date: 2023-09-26
Publication date: 2024-06-21

Abstract

Disclosed are a winding type electrode assembly, a method for manufacturing the same, and a secondary battery including the same.

Description

Wound electrode assembly, method for manufacturing the same, and secondary battery including the same

Technical Field

The present invention relates to a winding-type electrode assembly, a method for manufacturing the same, and a secondary battery including the same, and more particularly, to a winding-type electrode assembly including a swelling tape, a method for manufacturing the same, and a cylindrical secondary battery including the same.

The present application claims priority and benefit from korean patent application No. 10-2022-012623 filed on the korean intellectual property office at 9/26 of 2022, the entire contents of which are incorporated herein by reference.

Background

For a cylindrical battery, a rolled electrode assembly is manufactured by rolling a long electrode having a prescribed width into a roll form. In a cylindrical battery manufactured by inserting such a wound electrode assembly into a battery case, shrinkage/expansion of the electrode repeatedly occurs during charge and discharge. In particular, when the degree of shrinkage/expansion of the electrode assembly increases due to the tab (intab) located in the core of the wound electrode assembly or the silicon-based active material added in the negative electrode, the pressure acting on the core portion of the electrode assembly greatly increases.

With the recent increase in low resistance/high capacity designs, the rolled electrode assembly includes a plurality of tabs or adds a silicon-based active material in many cases. Accordingly, the electrode assembly located in the core portion is increased in probability of deformation due to shrinkage/expansion of the electrode assembly. In particular, when the separator between the negative electrode and the positive electrode is damaged, the negative electrode and the positive electrode are in direct contact with each other, and heat generation and ignition are caused due to an internal short circuit.

In order to solve the problems of damage to the separator and internal short circuit caused by deformation of the electrode assembly, it is necessary to develop a technique capable of protecting the positive electrode and the separator in the corresponding region and suppressing the occurrence of internal short circuit.

Disclosure of Invention

Technical problem

The present invention has been made in an effort to provide a winding-type electrode assembly, of which the design has been changed, a method for manufacturing the same, and a secondary battery including the same.

However, the problems to be solved by the present invention are not limited to the above-described problems, and other problems not mentioned will be clearly understood by those skilled in the art from the following description.

Technical proposal

An exemplary embodiment of the present invention provides a winding type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound, wherein the winding type electrode assembly includes a swelling tape attached on at least one surface of the first electrode, wherein the first electrode includes a first end portion from which winding is started in a longitudinal direction and a second end portion at which winding is ended, and wherein the swelling tape is attached such that one end portion matches the first end portion of the first electrode.

Another embodiment of the present invention provides a method for manufacturing a winding type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound, the method including: (a) transferring the first electrode in a roll-to-roll manner; (b) Attaching a swelling tape on at least one surface of the slit region included in the first electrode; and (c) slitting a longitudinal center portion of the slitting region of the first electrode, wherein in the attaching of (b) above, the swelling tape is attached such that the longitudinal center portion of the swelling tape matches the longitudinal center portion of the slitting region of the first electrode, and wherein in the slitting of (c) above, the longitudinal center portion of the slitting region is slit such that the first electrode is provided with a first end portion from which winding is started in the longitudinal direction and a second end portion from which winding is ended, and a further embodiment of the present invention also provides a wound electrode assembly manufactured by the method.

Another exemplary embodiment of the present invention provides a secondary battery including: the above-described wound electrode assembly; and a battery case for accommodating the electrode assembly.

Advantageous effects

The rolled electrode assembly according to the exemplary embodiment of the present invention includes a swelling tape attached such that it expands and wraps one longitudinal end portion of the positive electrode when impregnated with an electrolyte solution, thereby preventing damage to the positive electrode and the separator due to deformation of the electrode assembly caused by shrinkage/expansion of the electrode during charge and discharge of the battery. Further, even when the separator is damaged, the swelling tape can prevent an internal short circuit between the positive electrode and the negative electrode to improve the stability and life characteristics of the battery.

The method for manufacturing a roll-type electrode assembly according to an exemplary embodiment of the present invention enables the roll-type electrode assembly including a swelling tape attached such that it swells and wraps one longitudinal end portion of a positive electrode when impregnated with an electrolyte solution to be manufactured in a continuous process using an existing roll-to-roll processing apparatus, thereby enabling productivity and economical efficiency to be ensured.

Further, the secondary battery according to the present invention can prevent an internal short circuit between the positive electrode and the negative electrode even when the electrode assembly is deformed due to shrinkage/expansion of the electrode during charge and discharge of the battery, thereby improving the stability and life characteristics of the battery.

The effects of the present invention are not limited to the aforementioned effects, and effects not mentioned will be clearly understood by those skilled in the art from the present specification and drawings.

Drawings

Fig. 1 illustrates a rolled electrode assembly including a swelling tape according to an exemplary embodiment of the present invention.

Fig. 2 shows schematic views of a method for manufacturing a rolled electrode assembly including a swelling tape and a method for manufacturing a rolled electrode assembly including a PET tape according to an exemplary embodiment of the present invention.

Fig. 3 is an image illustrating an implementation example of a method for manufacturing a rolled electrode assembly according to an exemplary embodiment of the present invention.

Fig. 4 shows swelling test results of a swelling tape included in a rolled electrode assembly according to an exemplary embodiment of the present invention.

Fig. 5 and 6 are images showing first end portions of the first electrode before and after activation of the rolled electrode assembly according to example 1 and comparative example 1.

Fig. 7 shows the change in coulombic efficiency with respect to the cycle progress and the tracking evaluation results of the room temperature-voltage over time of the secondary batteries prepared in example 1 and comparative example 2.

Fig. 8 is an image showing the state of a portion of the separator facing the first electrode included in the secondary batteries prepared in example 1 and comparative example 2.

Fig. 9 is an image showing the result of roundness evaluation of the secondary batteries prepared in example 1 and comparative example 3.

Description of the reference numerals

100: First electrode

101: First electrode current collector

102. 103: A first electrode active material layer

110: A first end portion of the first electrode

20: Partition piece

30. 30': Swelling belt

40: PET (polyethylene terephthalate) belt

L: length of swelling tape before swelling

L': length of the swelling tape after swelling

Ls: expanded length of the swelling belt

S10, S10': first electrode preparation Process

S11: first electrode transfer step

S11': slitting step

S11': first electrode separation step

S12: swelling tape attachment step

S12': protective tape attaching step

S13, S13': slitting step

S20: supply process

S30: layout process

S40: lamination process

S50: winding process

S60: tape sticking process

S70: inspection process

TD: in the width direction

MD: longitudinal direction

Detailed Description

Throughout the specification, when a portion "comprises," "comprising," or "has" a constituent element, unless specifically described otherwise, this is not intended to exclude another constituent element, but rather means that another constituent element may also be included.

Throughout the specification, when an element is referred to as being "on" another element, it can be directly in contact with the other element or intervening elements may also be present.

The rolled electrode assembly according to the exemplary embodiment of the present invention includes a swelling tape attached such that it expands and wraps one end portion of the positive electrode in the longitudinal direction when immersed in an electrolyte solution, thereby preventing the positive electrode and the separator from being damaged due to deformation of the electrode assembly caused by shrinkage/expansion of the electrode during charge and discharge of the battery. Further, even when the separator is damaged, the swelling tape can prevent an internal short circuit between the positive electrode and the negative electrode to improve the stability and life characteristics of the battery.

According to an exemplary embodiment of the present invention, the rolled electrode assembly may include a swelling tape attached on at least one surface of the first electrode. In particular, the swelling tape may be attached on one surface of the first electrode facing the winding axis or on the surface opposite to the one surface facing the winding axis, or on both surfaces of the first electrode.

As described below, the swelling tape may expand and increase in length when impregnated with an electrolyte solution. Therefore, when the swelling tape is attached on one surface of the first electrode, the swelling tape wraps one longitudinal end portion of the first electrode after swelling, resulting in preventing direct contact between the first electrode and the second electrode facing each other via the separator even if the separator is damaged.

Therefore, in the case where the swelling tape is attached on one surface of the first electrode facing the winding axis, the swelling tape can be more effectively used to prevent internal short-circuiting between the positive electrode and the negative electrode when the separator is damaged. Further, in the case where the swelling tapes are attached on both surfaces of the first electrode, after swelling, the end portions of the swelling tapes are brought into contact with the end portions of the first electrode while wrapping the end portions of the first electrode, so that the longitudinal end portions of the first electrode can be more effectively protected. Further, in the case where the swelling tape wraps the longitudinal end portion of the first electrode after swelling, the effect of relieving the internal stress and improving the roundness of the core portion may be excellent due to the porous material property of the swelling tape.

According to an exemplary embodiment of the present invention, the first electrode may include a first end portion from which winding starts in the longitudinal direction and a second end portion at which winding ends. In other words, the first electrode may be such that the winding starts from the first end portion and proceeds towards the second end portion. That is, the first end portion may refer to one longitudinal end portion located in the core portion of the wound-type electrode assembly after winding, and the second end portion may refer to one longitudinal end portion located at the outermost portion of the wound-type electrode assembly after winding.

According to an exemplary embodiment of the present invention, the swelling tape may be attached such that one end portion is matched with one longitudinal end portion of the first electrode. In particular, the swelling tape may be attached such that one end portion mates with the first end portion of the first electrode. In other words, the swelling tape may be attached such that one end portion matches one longitudinal end portion of the first electrode located in the core portion.

Thereby, the swelling tape can prevent the electrode assembly from being deformed due to shrinkage/expansion of the electrode during charge and discharge of the battery, and particularly prevent damage to the separator due to sliding of the first end portion of the first electrode in the core portion. Specifically, after the expansion, one end portion of the swelling tape wraps around the end portion of the first electrode, or the end portions of the swelling tape attached on both surfaces of the first end portion of the first electrode wrap around and contact the end portion of the first electrode. Thus, even when the separator is damaged, the swelling tape can be effectively used to prevent an internal short circuit between the positive electrode and the negative electrode.

According to an exemplary embodiment of the present invention, the length of the swelling tape in the width direction may be 60% or more and 100% or less of the width of 100% of the first electrode. Specifically, the length of the swelling tape in the width direction may be 70% or more and 100% or more, 80% or more and 100% or less, 60% or more and 90% or less, 60% or more and 80% or less, 60% or more and 70% or more and 90% or less of 100% of the width of the first electrode. When the length of the swelling tape in the width direction satisfies the above range, the length of the swelling tape after swelling may correspond to the length of the first electrode in the width direction, and one end portion of the swelling tape effectively wraps one longitudinal end portion of the first electrode. Thus, even when the separator is damaged, the swelling tape can be more effectively used to prevent internal short circuit between the positive electrode and the negative electrode.

If the length of the swelling tape in the width direction is less than the above range, the effect of protecting the first end portion of the first electrode becomes poor, and one end portion of the first electrode is exposed, which may cause damage to the separator. When the separator is damaged, an internal short circuit may occur due to direct contact between the first electrode and the second electrode. On the other hand, if the length of the swelling tape in the width direction exceeds the above-described range, the manufacturing cost may increase due to excessive use of materials, and after expansion, one end portion of the swelling tape is excessively exposed in the width direction of the rolled electrode assembly, which may result in defects during the insertion process into the battery case, and local problems such as lithium deposition due to formation of steps in the overlapping region of the swelling tape. Note that the preferable length of the swelling belt in the width direction may be adjusted according to the physical properties of the swelling belt, in particular, the length change rate before/after swelling.

According to an exemplary embodiment of the present invention, the length of the swelling tape in the longitudinal direction may be 250% or more and 3500% or less of the thickness of 100% of the first electrode. Specifically, the length of the swelling tape in the longitudinal direction may be 300% or more, 350% or more, 400% or more, 450% or more, or 500% or more of the thickness of 100% of the first electrode, and the length of the swelling tape in the longitudinal direction may be 3000% or less, 2500% or less, 2000% or less, or 1500% or less, preferably 1000% or less, 850% or less, or 700% or less, based on the thickness of 100% of the first electrode.

When the length of the swelling tape in the longitudinal direction satisfies the above-described range, the length of the swelling tape in the longitudinal direction after swelling may correspond to the thickness of the first electrode, and one end portion of the swelling tape effectively wraps one longitudinal end portion of the first electrode. Therefore, even when the separator is damaged, the swelling tape can be more effectively used to prevent internal short circuits between the positive electrode and the negative electrode.

Specifically, the swelling tape may be expanded by 40% or more toward both sides in the width direction and the longitudinal direction, respectively, or may be expanded by 20% or more toward one side. That is, when the length of the swelling tape attached on both surfaces of the first electrode in the longitudinal direction is 250% or more of the thickness of 100% of the first electrode, the sum of the longitudinal lengths of the swelling tapes expanded may correspond to the thickness of the first electrode, and one end portion of the swelling tape attached on both surfaces of the first electrode may contact with one longitudinal end portion of the first electrode and effectively wrap one longitudinal end portion of the first electrode.

Further, when the length of the swelling tape in the longitudinal direction is 500% or more of the thickness of 100% of the first electrode, even in the case where the swelling tape is attached only on one surface of the first electrode facing the winding axis, the length of the swelling tape in the longitudinal direction may correspond to the thickness of the first electrode, and the swelling tape may be effectively used to prevent internal short-circuiting between the positive electrode and the negative electrode when the separator is damaged.

On the other hand, if the length of the swelling tape in the longitudinal direction is less than 250% of the thickness of 100% of the first electrode, the swelling tape may not completely wrap one end portion of the first electrode after swelling, and thus, a portion of one end portion of the first electrode may be exposed. Therefore, the effect of preventing the separator from being damaged and preventing the internal short circuit between the positive electrode and the negative electrode may be deteriorated when the separator is damaged.

On the other hand, when the length of the swelling tapes attached on both surfaces of the first electrode in the longitudinal direction is 1000% or less of the thickness of 100% of the first electrode, defects caused by overlapping regions of the swelling tapes, which may be caused by excessive exposure of one end portion of the swelling tapes in the longitudinal direction of the first electrode, may be minimized.

Further, when the length of the swelling tape in the longitudinal direction is 700% or less of the thickness of 100% of the first electrode, inactive regions that may be formed in the swelling tape attachment region may be adjusted to an appropriate level to achieve the above-described effect of preventing damage to the separator and internal short circuit while minimizing the influence on electrochemical properties such as the capacity reduction rate of the battery including the swelling tape.

According to an exemplary embodiment of the present invention, the first end portion of the first electrode may be such that the current collector of the first electrode and the active material layer of the first electrode form the end portion at the same position. In other words, the first end portion of the first electrode may have a free edge shape. Thereby, an area of an unnecessary uncoated portion on the first electrode current collector may be reduced to ensure economic efficiency, and a slitting process may be performed after forming an active material layer on the electrode, so that roll-to-roll processing including the slitting process and the winding process may be more effectively performed. Here, the description of the "same position" means that the end portions in the longitudinal direction are the same, and may include a case where the end portions are formed at substantially the same position due to a processing error that may occur in a dicing process or the like.

According to an exemplary embodiment of the invention, the swelling tape may be expanded or made flexible by the electrolyte solution. In particular, the swelling tape may include a portion made of a polymer material as described below, and when the swelling tape is impregnated with an electrolyte solution, the portion made of the polymer material absorbs the electrolyte solution and thus may expand or become flexible. More specifically, as a feature of the polymeric material, the volume of the polymeric material may increase due to solvent molecules entering between the chains of the polymeric material. Thus, the swelling tape may expand or become flexible as it absorbs the electrolyte solution.

According to an exemplary embodiment of the present invention, the swelling tape may be swelled by the electrolyte solution, and after the swelling, the swelling tape may wrap the first end portion of the first electrode. Specifically, the swelling tape may be expanded and increased in longitudinal length by absorbing an electrolyte solution including an organic solvent as described below, and after expansion, one longitudinal end portion of the swelling tape may be extended and bent to wrap the first end portion of the first electrode. In other words, after expansion, the longitudinal length of the swelling tape may increase, and the swelling tape may be bent to wrap around at least one edge of the first end portion of the first electrode.

Thereby, the sharp free edge of the positive electrode can be prevented from being in direct contact with the separator or the negative electrode, and thus the electrode assembly can be prevented from damaging the positive electrode and the separator due to deformation of the electrode caused by shrinkage/expansion during charge and discharge of the battery. Further, even when the separator is damaged, the swelling tape can prevent an internal short circuit between the positive electrode and the negative electrode to improve the stability and life characteristics of the battery.

Specifically, (a) of fig. 1 shows a first electrode including swelling tapes attached to both surfaces of a first electrode before impregnation with an electrolyte solution, (b) of fig. 1 shows a first electrode including swelling tapes attached to both surfaces of a first electrode after impregnation with an electrolyte solution, and (c) of fig. 1 shows a first electrode including swelling tapes attached to one surface of a first electrode after impregnation with an electrolyte solution.

Referring to (a) of fig. 1, a swelling tape may be attached on both surfaces of the first electrode such that one end portion is matched with the first end portion of the first electrode, and referring to (b) of fig. 1, the swelling tape is swelled by an electrolyte solution when impregnated with the electrolyte solution, and after swelling, the swelling tape may wrap the first end portion of the first electrode. On the other hand, referring to (c) of fig. 1, a swelling tape may be attached on one surface of the first electrode such that one end portion is matched with the first end portion of the first electrode, the swelling tape may be swelled by the electrolyte solution when impregnated with the electrolyte solution, and after swelling, the swelling tape may wrap the first end portion of the first electrode.

According to an exemplary embodiment of the present invention, the length of the swelling tape after being impregnated with an electrolyte solution including 45wt% dimethyl carbonate, 20wt% ethylene carbonate, 15wt% ethylmethyl carbonate, and 15wt% LiPF ₆ as an electrolyte may be 120% or more and 160% or less of the length of 100% of the swelling tape before being expanded. Specifically, the length of the swelling tape after expansion may be 120% or more and 150% or less, 120% or more and 140% or less, 120% or more and 130% or less, 130% or more and 160% or less, 140% or more and 160% or less, 150% or more and 160% or less, or 130% or more and 150% or less of the length of the swelling tape before expansion of 100%.

Here, the length of the swelling tape after swelling may include the length in both the longitudinal direction and the width direction. That is, the ratio of the length of the swelling tape after expansion to the length of the swelling tape before expansion may be the same in the longitudinal direction and the width direction. Further, the length of the swelling belt may refer to a length measured from one end portion of the swelling belt to the other end portion of the swelling belt in a specific direction. For example, when the length of the swelling tape after expansion is measured from one end portion to the other end portion in the longitudinal direction, the length may be 120% or more and 160% or less, and when the length of one longitudinal end portion after expansion is measured based on the longitudinal center portion of the swelling tape before expansion, the length may be 110% or more and 130% or less.

If the length of the swelling tape after swelling satisfies the above range, the swelling tape is impregnated with the electrolyte solution and may be swelled to a length suitable for effectively wrapping the first end portion of the first electrode even when the swelling tape is attached on at least one surface of the first electrode such that one end portion is matched with the first end portion of the first electrode. Accordingly, the effect of protecting the first end portion of the first electrode may be excellent, and the effect of preventing an internal short circuit and improving the stability of the battery may be more excellent.

According to an exemplary embodiment of the present invention, the swelling tape may include a portion made of a polymer material that absorbs the electrolyte solution and swells or becomes flexible, and a portion having adhesiveness for attaching the swelling tape to the first electrode.

According to an exemplary embodiment of the present invention, the swelling tape may include a base layer and an adhesive layer, and the adhesive layer may be disposed on at least one surface of the base layer. Specifically, the swelling tape may include a multilayer structure having a base layer that absorbs an electrolyte solution and swells when impregnated with the electrolyte solution, and an adhesive layer that attaches the swelling tape to the first electrode, and the adhesive layer may be provided on one surface or both surfaces of the base layer.

According to an exemplary embodiment of the present invention, the adhesive layer may include a pressure sensitive adhesive including a polyacrylic resin. That is, the adhesive force of the adhesive layer may be affected by the amount of pressure applied to the surface of the swelling tape.

According to an exemplary embodiment of the present invention, the adhesive layer may include one or more comonomers selected from the group consisting of polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), and polybutyl methacrylate (PBMA). Specifically, the adhesive layer may include a polyacrylic resin manufactured by copolymerizing a comonomer selected from the group including monomers such as Ethyl Acrylate (EA), butyl Acrylate (BA), and 2-ethylhexyl acrylate (2-EHA) with a comonomer selected from the group including polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), and polybutyl methacrylate (PBMA). When the adhesive layer includes the above-mentioned materials, the adhesive force of the swelling tape can be maintained at an appropriate level while minimizing the influence on the electrochemical performance of the battery including the swelling tape.

According to an exemplary embodiment of the present invention, the base layer may include a urethane-based resin. For example, the base layer may include polyurethane resin or the like. When the base layer comprises the above-described materials, absorption of the electrolyte solution by the swelling tape may be further promoted, and when impregnated with the electrolyte solution, the swelling tape may expand to a length suitable for effectively wrapping the first end portion of the first electrode.

According to an exemplary embodiment of the present invention, the electrolyte solution may include an organic solvent. Specifically, the organic solvent may include 70wt% or more of any one of the following: ethylene Carbonate (EC), propylene Carbonate (PC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and mixtures thereof. Specifically, the electrolyte solution may include a mixed organic solvent containing 45wt% or more of dimethyl carbonate. For example, the electrolyte solution may include a mixed organic solvent including 45wt% dimethyl carbonate, 20wt% ethylene carbonate, and 15wt% ethylmethyl carbonate.

In particular, when the base layer includes a urethane-based resin, the base layer may be swelled by absorbing the electrolyte solution, and when the electrolyte solution includes an organic solvent of the aforementioned type, the base layer including the urethane-based resin may be more easily swelled. That is, the swelling tape including the base layer may be more easily swelled, and the swelled swelling tape may effectively wrap the first end portion of the first electrode to prevent damage to the separator.

According to an exemplary embodiment of the present invention, the electrolyte solution may further include an electrolyte. Examples of the electrolyte may include, but are not limited to, a solid polymer electrolyte, a gel polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like, which may be used to manufacture a lithium secondary battery.

Specifically, the electrolyte solution may include a metal salt such as LiPF ₆ as an electrolyte, and for example, an electrolyte solution including 45wt% of dimethyl carbonate, 20wt% of ethylene carbonate, 15wt% of ethylmethyl carbonate, and 15wt% of LiPF ₆ as an electrolyte may be used. When the electrolyte solution further includes the aforementioned type of electrolyte, the swelling property of the swelling tape may be more excellent than that in the case where the electrolyte is not included, and the swelling tape that is expanded may effectively wrap the first end portion of the first electrode to prevent damage to the separator.

According to an exemplary embodiment of the present invention, the first electrode may be a positive electrode and the second electrode may be a negative electrode. That is, the winding-type electrode assembly according to the exemplary embodiment of the present invention may be a winding-type electrode assembly in which a positive electrode, a first separator, a negative electrode, and a second separator are sequentially stacked and wound, the winding-type electrode assembly including a swelling tape attached on at least one surface of the positive electrode, wherein the positive electrode includes a first end portion from which winding is started in a longitudinal direction, and a second end portion at which winding is ended, and wherein the swelling tape is attached such that one end portion matches the first end portion of the positive electrode.

According to an exemplary embodiment of the present invention, the first electrode may include a current collector and an active material layer disposed on the current collector. That is, the positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector. Specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on one surface or both surfaces of the positive electrode current collector and including a positive electrode active material. In other words, the positive electrode active material layer is formed on the positive electrode coating portion of the positive electrode current collector, and the surface where the positive electrode active material layer is not disposed may be referred to as a positive electrode non-coating portion.

According to an exemplary embodiment of the present invention, the positive electrode current collector may include a positive electrode coating portion coated with a positive electrode active material and a positive electrode non-coating portion not coated with the positive electrode active material, and may include a tab on the positive electrode non-coating portion. Specifically, the positive electrode current collector may include a positive electrode non-coating portion and a positive electrode tab formed on the positive electrode non-coating portion.

According to an exemplary embodiment of the present invention, the positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. Specifically, as the positive electrode current collector, stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel each surface of which is treated with carbon, nickel, titanium, silver, or the like may be used. That is, the positive electrode current collector may be provided in the form of surface-treated stainless steel, aluminum foil, or the like.

In addition, the positive electrode current collector may generally have a thickness of 3 to 50 μm, but is not limited thereto, and the surface of the current collector may be formed with microscopic irregularities to enhance the adhesion of the positive electrode active material. For example, the positive electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam body, and a non-woven fabric body.

According to an exemplary embodiment of the present invention, the positive electrode active material may be a commonly used positive electrode active material. Specifically, the positive electrode active material may be a layered compound such as: lithium cobalt oxide (LiCoO ₂) and lithium nickel oxide (LiNiO ₂), or compounds substituted with one or more transition metals; lithium iron oxides such as LiFe ₃O₄; lithium manganese oxides such as the formulas Li _1+xMn_2-xO₄(0≤x≤0.33)、LiMnO₃、LiMn₂O₃ and LiMnO ₂; lithium copper oxide (Li ₂CuO₂); vanadium oxides such as LiV ₃O₈、V₂O₅ and Cu ₂V₂O₇; ni-site lithium nickel oxide represented by the chemical formula LiNi _1-yM_yO₂ (wherein M is at least one selected from the group consisting of Co, mn, al, cu, fe, mg, B and Ga, and satisfies 0.01.ltoreq.y.ltoreq.0.3); lithium manganese composite oxide represented by the chemical formula LiMn _2-zM_z0₂ (wherein M is at least one selected from the group consisting of Co, ni, fe, cr, zn and Ta, and 0.01.ltoreq.z.ltoreq.0.1 is satisfied) or Li ₂Mn₃MO₈ (wherein M is at least one selected from the group consisting of Fe, co, ni, cu and Zn); liMn ₂O₄ in which a part of Li of the chemical formula is substituted with an alkaline earth metal ion, etc., but is not limited thereto. The positive electrode may be lithium metal.

According to an exemplary embodiment of the present invention, the positive electrode active material layer may further include a positive electrode conductive material and a positive electrode binder. The positive electrode conductive material is used to impart conductivity to the electrode, and may be used without particular limitation as long as it does not cause chemical changes in the battery to be constructed and has electron conductivity. Specific examples of the positive electrode conductive material may 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, and carbon fiber; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative or the like, and any one of them or a mixture of two or more thereof may be used.

In addition, the positive electrode binder serves to improve the attachment between particles of the positive electrode active material and the adhesion between the positive electrode active material and the positive electrode current collector. Specific examples may include polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, polyacrylonitrile, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene-butadiene rubber (SBR), fluororubber, or various copolymers thereof, and the like, and any one of them or a mixture of two or more thereof may be used.

According to an exemplary embodiment of the present invention, the second electrode may include a current collector and an active material layer disposed on the current collector. That is, the anode may include an anode current collector and an anode active material layer disposed on the anode current collector. Specifically, the anode may include an anode current collector and an anode active material layer formed on one surface or both surfaces of the anode current collector and including an anode active material. In other words, the anode active material layer is formed on the anode coated portion of the anode current collector, and the surface on which the anode active material layer is not provided may be referred to as an anode uncoated portion.

According to an exemplary embodiment of the present invention, the anode current collector may include an anode coated portion formed with an anode active material layer and an anode uncoated portion not formed with the anode active material layer, and may include a tab on the anode uncoated portion. In particular, the anode current collector may include an anode uncoated portion and an anode tab formed on the anode uncoated portion. Thus, the electrode assembly produced may include one or more negative electrode tabs.

According to an exemplary embodiment of the present invention, the anode active material layer may include an anode active material including one or more selected from the group consisting of a silicon-based material and a carbon-based material. In addition, the anode active material layer may further include an anode conductive material and an anode binder, and for the anode active material, the anode conductive material and the anode binder, materials used in the art may be used without limitation.

According to an exemplary embodiment of the present invention, the anode current collector is not particularly limited as long as it has conductivity without causing chemical changes in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel each surface of which is treated with carbon, nickel, titanium, silver, or the like, may be used for the negative electrode current collector. In particular, transition metals, such as copper and nickel, which well adsorb carbon, may be used for the negative electrode current collector. The thickness of the negative electrode current collector may be 6 μm or more and 80 μm or less. However, the thickness of the anode current collector is not limited thereto.

According to an exemplary embodiment of the present invention, the anode binder may include at least one selected from the group consisting of: polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene-butadiene rubber (SBR), fluororubber, polyacrylic acid, and the above materials in which hydrogen is substituted with Li, na, ca, or the like, and may also include various copolymers thereof.

According to an exemplary embodiment of the present invention, the anode conductive material is not particularly limited as long as it has conductivity without causing chemical changes in the battery, and for example, may be used: graphite, such as natural graphite or artificial graphite; carbon blacks such as acetylene black, ketjen black, channel black, furnace black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powders; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; conductive materials such as polyphenylene derivatives and the like.

An exemplary embodiment of the present invention provides a method for manufacturing a winding type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound, the method including: (a) transferring the first electrode in a roll-to-roll manner; (b) Attaching a swelling tape on at least one surface of the slit region included in the first electrode; and (c) slitting a longitudinal central portion of the slitting area of the first electrode, wherein in the attaching of (b) the swelling tape is attached such that the longitudinal central portion of the swelling tape matches the longitudinal central portion of the slitting area of the first electrode, and wherein in the slitting of (c) the longitudinal central portion of the slitting area is slit such that the first electrode is provided with a first end portion from which winding starts in the longitudinal direction and a second end portion at which winding ends.

The method for manufacturing a roll-type electrode assembly according to an exemplary embodiment of the present invention enables the roll-type electrode assembly including a swelling tape attached such that it swells and wraps one longitudinal end portion of a positive electrode when impregnated with an electrolyte solution to be manufactured in a continuous process using an existing roll-to-roll processing apparatus, thereby enabling productivity and economical efficiency to be ensured. Further, the rolled electrode assembly manufactured by the manufacturing method includes a swelling tape attached such that it expands and wraps one longitudinal end portion of the positive electrode when impregnated with an electrolyte solution, thereby preventing damage to the positive electrode and the separator due to deformation of the electrode assembly caused by shrinkage/expansion of the electrode during charge and discharge of the battery. Further, even when the separator is damaged, the swelling tape can prevent an internal short circuit between the positive electrode and the negative electrode to improve the stability and life characteristics of the battery.

According to an exemplary embodiment of the present invention, the method for manufacturing the rolled electrode assembly may include the step (a) of transferring the first electrode in a roll-to-roll manner. Specifically, step (a) may be performed in a roll-to-roll manner in which a plurality of flexible metal foils or the like are processed while being moved between rolls. Here, the roll-to-roll manner may refer to the following manner: the electrode current collector is supplied by unwinding a roll having the flexible thin metal sheet-shaped electrode current collector wound thereon, an electrode mixture layer is formed by applying an electrode paste including an electrode active material onto at least one surface of the electrode current collector and drying the electrode paste, and then the treated electrode current collector is rewound and collected from another roll. That is, step (a) may be a step of transferring the first electrode in a roll-to-roll manner to process it, and may be expressed as a first electrode transfer step (S11).

According to an exemplary embodiment of the present invention, the method for manufacturing a rolled electrode assembly may include the step (b) of attaching a swelling tape on at least one surface of the slit region included in the first electrode. Here, the slitting region may refer to a region for cutting the first electrode by a slitting process of cutting the first electrode or the electrode assembly including the first electrode to a set length, and the slitting region may refer to a partial region including the first electrode current collector and the first electrode active material layer included in the first electrode in the longitudinal direction, and the longitudinal length of the slitting region may be adjusted according to the process conditions. Furthermore, the length and position of the slitting area may vary depending on the length and position of the attached slitting area. That is, the slit region may be set by changing the length and position of the swelling tape attached on one surface or both surfaces of the first electrode according to the process conditions.

According to an exemplary embodiment of the present invention, in step (b), the swelling tape may be attached such that a longitudinal central portion of the swelling tape matches a longitudinal central portion of the slit region of the first electrode. Specifically, in step (b), the swelling tape may be attached on at least one surface of the slit region included in the first electrode such that a longitudinal central portion of the swelling tape matches with a longitudinal central portion of the slit region of the first electrode. Thereby, in the subsequent step of slitting the longitudinal center portion of the slitting region, the first electrode may be provided with a first end portion from which winding is started in the longitudinal direction and a second end portion at which winding is ended, and the first electrode may be provided in the following state: after the slitting step, a swelling tape having a predetermined length is attached to at least one surface of the first end portion and the second end portion.

According to an exemplary embodiment of the present invention, the step (b) may be a step of attaching a swelling tape on at least one surface of the slit region included in the first electrode, and in particular, the step (b) may be a step of attaching a swelling tape on one surface or both surfaces of the slit region included in the first electrode, and may be expressed as a swelling tape attaching step (S12).

According to an exemplary embodiment of the present invention, the method for manufacturing the rolled electrode assembly may include the step (c) of slitting a longitudinal center portion of the slitting region of the first electrode. Specifically, the step (c) may be a step of cutting the first electrode or the electrode assembly including the first electrode to a set length, and cutting may be performed using a cutter or the like, but is not particularly limited.

According to an exemplary embodiment of the present invention, the step (c) may be a step of dividing a longitudinal central portion of the slit region into a first end portion from which the winding is started in the longitudinal direction and a second end portion at which the winding is ended, such that the first electrode is provided with the first end portion and the second end portion. Specifically, the step (c) may be a step of dividing a longitudinal central portion of the dividing region into such a manner that the first electrode or the first electrode included in the electrode assembly is provided with a first end portion from which winding is started in the longitudinal direction and a second end portion at which winding is ended. Step (c) may be performed in a plurality of steps, and when performed during the first electrode preparation process (S10), step (c) may be expressed as a slitting step (S13).

According to an exemplary embodiment of the present invention, the steps (a) and (b) may be performed during the first electrode preparation process (S10), and the step (c) may be performed during the first electrode preparation process (S10) or after the first electrode preparation process (S10). Specifically, step (c) may be performed before or after the winding process (S50). More specifically, step (c) may be performed after the winding process (S50).

When a protective tape is used to protect the electrode end portions exposed through the slitting step, a separate process may be required to check the positions of the slit electrode end portions after the electrodes are slit and to appropriately attach the protective tape to wrap the slit electrode end portions, and after the protective tape is attached to the end portions of the electrodes, an inspection process, such as a visual inspection step for eliminating attachment defects, may be additionally required. Further, when the winding process is performed only after the visual inspection step to reduce defects in the electrode assembly, the production speed of the wound electrode assembly may be greatly reduced, so that roll-to-roll processing is practically impossible.

On the other hand, the method for manufacturing a rolled electrode assembly according to an exemplary embodiment of the present invention may enable the rolled electrode assembly including the swelling tape to be manufactured in a continuous process using an existing roll-to-roll processing apparatus. In other words, the method for manufacturing the rolled electrode assembly includes the swelling tape attaching step (S12) in the first electrode preparation process (S10), so that the step (c) may be performed during the first electrode preparation process (S10) or after the first electrode preparation process (S10), and thus, the entire process may be performed by roll-to-roll processing used in industry. That is, the method for manufacturing a wound-type electrode assembly according to an exemplary embodiment of the present invention enables the wound-type electrode assembly including a swelling tape attached such that it swells and wraps one longitudinal end portion of a positive electrode when impregnated with an electrolyte solution to be manufactured in a continuous process using an existing roll-to-roll processing apparatus, thereby enabling productivity and economic efficiency to be ensured.

Specifically, fig. 2 (a) schematically illustrates a method for manufacturing a rolled electrode assembly including a swelling tape according to an exemplary embodiment of the present invention, wherein the method for manufacturing a rolled electrode assembly includes a step of attaching the swelling tape (S12), and fig. 2 (b) schematically illustrates a method for manufacturing a rolled electrode assembly including a PET tape, wherein the PET protective tape is attached to wrap a first end portion of a first electrode instead of the swelling tape.

Referring to (b) of fig. 2, in order to attach the protective tape to wrap the first end portion of the first electrode as in the wound electrode assembly including the swelling tape according to the exemplary embodiment of the present invention, an additional process may be required. That is, when the protective tape (PET) attaching step (S12') is included instead of the swelling tape attaching step (S12), an additional process may be required to produce an electrode having a similar structure.

Specifically, when the protective tape (PET) attaching step (S12 ') is included instead of the swelling tape attaching step (S12), a step (S11 ') of slitting the first electrode after the first electrode transferring step (S11) and a first electrode spacing step (S11 ") of spacing the slit first electrodes by a predetermined distance so as to attach the protective tape made of PET may be required, and an additional slitting step (S13 ') of dividing the attached protective tape into the longitudinal end portions wrapping the first electrodes may also be required.

More specifically, when the protective tape (PET) attaching step (S12 ') is included instead of the swelling tape attaching step (S12), a step (S11') of stopping the advancing winder for the first electrode and then performing slitting may be performed, and a step (S11 ") of spacing the first electrode in consideration of the thickness of the first electrode so as to sufficiently wrap the first end portion of the slit first electrode may also be required. Thereafter, a step of attaching a protective tape on both surfaces of the spaced apart first electrodes (S12 ') and an additional slitting step of cutting the attached protective tape (S13') may also be required.

That is, when a PET protective tape is used instead of the swelling tape, a predetermined additional process may be required to provide a structure similar to that of the wound electrode assembly including the swelling tape according to the exemplary embodiment of the present invention.

In other words, the method for manufacturing the wound-type electrode assembly according to the exemplary embodiment of the present invention includes the swelling tape attaching step (S12), so that the wound-type electrode assembly including the swelling tape attached to wrap one longitudinal end portion of the positive electrode can be provided while minimizing a separate additional process. Further, productivity and economic efficiency can be ensured by realizing production of continuous processing using existing roll-to-roll processing equipment.

Specifically, fig. 3 (a) shows a state in which the swelling tape is attached to the slit region included in the first electrode in the winding process (S50) after the swelling tape attaching step (S12), fig. 3 (b) shows a state in which the swelling tape is attached such that one end portion matches the first end portion of the first electrode after the slitting step (S13), and fig. 3 (c) shows an attached state of the swelling tape obtained by detaching the wound electrode assembly after the winding process (S50).

Referring to fig. 2 (a), the method for manufacturing a rolled electrode assembly according to an exemplary embodiment of the present invention may further include a supply process (S20), an arrangement process (S30), a lamination process (S40), a rolling process (S50), a taping process (S60), an inspection process (S70), and the like.

Specifically, the supplying process (S20) may be a process of supplying the first electrode and the second electrode together with the first separator and the second separator after the first electrode preparing process (S10), and the disposing process (S30) may be a process of sequentially disposing the first electrode, the first separator, the second electrode, and the second separator supplied in the supplying process (S20) and forming a stack.

Further, the lamination process (S40) may be a process of pressurizing and thermally fusing the stack manufactured in the disposing process (S30), that is, the stack including the first electrode, the first separator, the second electrode, and the second separator, thereby providing the electrode assembly.

Note that the winding process (S50) may be a process of winding the electrode assembly on which the lamination process has been performed, and may further include a slitting process of cutting the electrode assembly to a set length before or after the winding process.

Next, the taping process (S60) may be a process of trimming the outer surface of the electrode assembly wound in the winding process (S50) with a sealing tape, and may be performed to prevent defects such as loosening of the electrode assembly due to the spacing of the longitudinal end portions of the first electrode, the first separator, the second electrode, and the second separator.

The inspection process (S70) may include a visual inspection step of determining a defect by inspecting shapes, arrangement, damage, etc. of the first electrode, the first separator, the second electrode, and the second separator included in the electrode assembly, and a withstand voltage test step of determining a defect by supplying power to the electrode assembly and measuring withstand voltage.

According to an exemplary embodiment of the present invention, the swelling tape used in the method for manufacturing the wound electrode assembly may be the same as the swelling tape described above with respect to the wound electrode assembly.

According to an exemplary embodiment of the present invention, the length of the swelling tape in the width direction may be 60% or more and 100% or less of the width of 100% of the first electrode. Specifically, the length of the swelling tape in the width direction may be 70% or more and 100% or less, 80% or more and 100% or less, 60% or more and 90% or less, 60% or more and 80% or less, 60% or more and 70% or more and 90% or less of the width of 100% of the first electrode. When the length of the swelling tape in the width direction satisfies the above range, the length of the swelling tape after swelling may correspond to the length of the first electrode in the width direction, and one end portion of the swelling tape effectively wraps one longitudinal end portion of the first electrode. Thus, even when the separator is damaged, the swelling tape can be more effectively used to prevent internal short circuit between the positive electrode and the negative electrode.

According to an exemplary embodiment of the present invention, the length of the swelling tape in the longitudinal direction may be 500% or more and 7000% or less of the thickness of 100% of the first electrode. Specifically, the length of the swelling tape in the longitudinal direction may be 600% or more, 700% or more, 800% or more, or 1000% or more of the thickness of 100% of the first electrode, and the length of the swelling tape in the longitudinal direction may be 6000% or less, 5000% or less, 4000% or less, or 3000% or less, preferably 2000% or less, 1700% or less, or 1400% or less of the thickness of 100% of the first electrode. When the length of the swelling tape in the longitudinal direction satisfies the above-described range, the length of the swelling tape cut after step (c) may be within an appropriate range, that is, 250% or more and 3500% or less, and preferably 250% or more and 1000% or less, of the thickness of the first electrode, the length of the swelling tape after expansion in the longitudinal direction may correspond to the thickness of the first electrode, and one end portion of the swelling tape effectively wraps one longitudinal end portion of the first electrode, thereby more effectively minimizing the influence on the electrochemical performance, such as the capacity reduction rate, of the battery including the swelling tape, and preventing internal short circuits between the positive electrode and the negative electrode even when the separator is damaged.

According to an exemplary embodiment of the present invention, the length of the swelling tape in the longitudinal direction may be 0.75mm or more and 10mm or less. Specifically, the length of the swelling tape in the longitudinal direction may be 1mm or more, 1.25mm or more, 1.5mm or more, 1.75mm or more, or 2mm or more, and the length of the swelling tape in the longitudinal direction may be 2.75mm or less, 2.5mm or less, 2.25mm or less. When the length of the swelling tape in the longitudinal direction satisfies the above-described range, the swelling tape whose longitudinal length corresponds to the thickness of the first electrode can be easily manufactured even when there is a certain process deviation.

According to an exemplary embodiment of the present invention, the first electrode may be a positive electrode and the second electrode may be a negative electrode. The positive and negative electrodes used in the method for manufacturing the rolled electrode assembly may be the same as those described above with respect to the rolled electrode assembly.

Exemplary embodiments of the present invention provide a wound electrode assembly manufactured by the above-described method for manufacturing a wound electrode assembly.

The rolled electrode assembly according to the exemplary embodiment of the present invention includes a swelling tape attached such that it expands and wraps one longitudinal end portion of the positive electrode when impregnated with an electrolyte solution, thereby preventing damage to the positive electrode and the separator due to deformation of the electrode assembly caused by shrinkage/expansion of the electrode during charge and discharge of the battery. Further, even when the separator is damaged, the swelling tape can prevent an internal short circuit between the positive electrode and the negative electrode to improve the stability and life characteristics of the battery. Further, when the swelling tape wraps the longitudinal end portion of the first electrode, the effect of relieving the internal stress and improving the roundness of the core portion may be excellent due to the porous material property of the swelling tape.

An exemplary embodiment of the present invention provides a secondary battery including the above-described wound electrode assembly and a battery case for accommodating the electrode assembly. In particular, the secondary battery may include the electrode assembly according to the above-described exemplary embodiments and a battery case for accommodating the electrode assembly.

The secondary battery according to the present invention can prevent an internal short circuit between the positive electrode and the negative electrode even when the electrode assembly is deformed due to shrinkage/expansion of the electrodes during charge and discharge of the battery, thereby improving the stability and life characteristics of the battery.

According to an exemplary embodiment of the present invention, the battery case may have a cylindrical shape. Specifically, the battery case may have a cylindrical shape, a square shape, a pouch shape, etc., according to the use, but is not limited thereto.

According to an exemplary embodiment of the present invention, the battery case may include an electrolyte therein. In particular, the electrolyte may include an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte, which may be used to manufacture a lithium secondary battery, but is not limited thereto. In particular, the electrolyte may include a nonaqueous organic solvent and a metal salt.

According to an exemplary embodiment of the present invention, as the non-aqueous organic solvent, for example, an aprotic organic solvent such as N-methyl-2-pyrrolidone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, methylethyl carbonate, γ -butyllactone, 1, 2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethyl sulfoxide, 1, 3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphotriester, trimethoxymethane, dioxolane derivative, sulfolane, methylsulfane, 1, 3-dimethyl-2-imidazolidinone, propylene carbonate derivative, tetrahydrofuran derivative, diethyl ether, methyl propionate, and ethyl propionate may be used.

According to an exemplary embodiment of the present invention, a lithium salt may be used as the metal salt, and the lithium salt is a material that is easily soluble in a non-aqueous electrolyte solution, wherein, for example, one or more selected from the group consisting of the following may be used as anions ：F^-、Cl^-、I^-、NO₃ ^-、N(CN)^2-、BF₄ ^-、ClO₄ ^-、PF₆ ^-、(CF₃)₂PF₄ ^-、(CF₃)₃PF₃ ^-、(CF₃)₄PF₂ ^-、(CF₃)₅PF^-、(CF₃)₆P^-、CF₃SO₃ ^-、CF₃CF₂SO₃ ^-、(CF₃SO₂)₂N^-、(FSO₂)₂N^-、CF₃CF₂(CF₃)₂CO^-、(CF₃SO₂)₂CH^-、(SF₅)₃C^-、(CF₃SO₂)₃C^-、CF₃(CF₂)₇SO₃ ^-、CF₃CO₂ ^-、CH₃CO₂ ^-、SCN^- and (CF ₃CF₂SO₂)₂N^-) of the lithium salt.

According to an exemplary embodiment of the present invention, for the purpose of improving the life characteristics of a battery, suppressing the decrease in the capacity of a battery, improving the discharge capacity of a battery, and the like, one or more additives, for example, halogenated alkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylenediamine, N-glycol, hexaphosphoric triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, and the like, may be included in the electrolyte in addition to the above electrolyte components.

Mode for the invention

Hereinafter, examples will be described in detail to specifically describe the present invention. However, examples according to the present invention may be modified in other forms, and the scope of the present invention should not be construed as being limited to the following examples. Examples of the present specification are provided to more fully explain the invention to those skilled in the art.

Example

Example 1

Preparation of electrode assemblies

The positive electrode having a total thickness of 154 μm was prepared by the following procedure: an aluminum foil having a thickness of 15 μm and a length of 63.9mm in the width direction was prepared as a positive electrode current collector, and a positive electrode active material slurry including NMCA (Ni-Mn-Co-Al) composite having a Ni content of 92% or more as a positive electrode active material and including CNTs as a conductive material was applied on the positive electrode current collector and dried to form a positive electrode active material layer.

Thereafter, a swelling tape having a thickness of 52 μm was prepared, which had an adhesive layer comprising a copolymer of Ethyl Acrylate (EA) and polyethyl methacrylate (PEMA) on one surface of a base layer made of Polyurethane (PU), and the swelling tape was attached to have a length of 62mm in the width direction and a length of 10mm in the longitudinal direction on one surface of a slit region of the positive electrode.

Next, a negative electrode having a total thickness of 187 μm was prepared by the following procedure: a copper foil having a thickness of 10 μm and a length of 62mm in the width direction was prepared as a negative electrode current collector, and a negative electrode active material slurry including artificial graphite and natural graphite as a negative electrode active material in an amount of 50 parts by weight, respectively, was applied on the negative electrode current collector and dried to form a negative electrode active material layer.

Note that two sheet-like polyethylene separators were prepared as the first separator and the second separator.

Thereafter, the positive electrode, the first separator, the negative electrode, and the second separator are sequentially arranged to form a stack, which is then pressurized and heat-fused. The central portion of the slit region is slit, the stack is wound such that a first end portion of the positive electrode from which winding is started is located in the core portion, and a sealing tape made of PET is attached to a second end portion at the end of winding to wrap and trim the upper and lower outer peripheral surfaces of the wound electrode assembly, thereby forming the wound electrode assembly. In this case, a sealing tape having a length of 62mm in the longitudinal direction, a length of 10mm in the width direction, and a thickness of 22 μm was used, and the length of the swelling tape after slitting was 5mm.

Preparation of secondary battery

The secondary battery was prepared by inserting a wound electrode assembly into a cylindrical battery case, injecting an electrolyte solution in which Ethylene Carbonate (EC), dimethyl carbonate (DMC) and ethylmethyl carbonate (EMC) are contained in an amount of 4:9:3 and LiPF ₆ was dissolved to 15wt%.

Example 2

A rolled electrode assembly and a secondary battery were prepared in the same manner as in example 1, except that the swelling tape was attached to each of the two surfaces of the slit region of the positive electrode to have a length of 62mm in the width direction and a length of 5mm in the longitudinal direction.

Comparative example 1

A rolled electrode assembly and a secondary battery were prepared in the same manner as in example 1, except that a PET tape was attached to one surface of the slit region of the positive electrode to have a length of 62mm in the width direction and a length of 10mm in the longitudinal direction.

Comparative example 2

A rolled electrode assembly and a secondary battery were prepared in the same manner as in example 1, except that the swelling tape was not attached in the split region of the positive electrode.

Comparative example 3

A rolled electrode assembly and a secondary battery were prepared in the same manner as in example 1, except that the central portion of the slitting region was slit without attaching the swelling tape in the slitting region of the positive electrode, the slit positive electrode was spaced apart, the PET tape was attached on each of both surfaces of the slitting region to have a length of 62mm in the width direction and a length of 10mm in the longitudinal direction, and then the central portion was additionally slit, thereby forming the structure of (b) of fig. 1.

Experimental example

Experimental example 1 swelling evaluation

Samples made of the same material as the swelling tapes used in examples 1 and 2 (length of 10mm in the longitudinal direction and length of 62mm in the width direction) were prepared, and an electrolyte solution in which LiPF ₆ was dissolved as an electrolyte in a mixed solvent of Ethylene Carbonate (EC), dimethyl carbonate (DMC) and ethylmethyl carbonate (EMC) was prepared. Thereafter, the swollen band sample was impregnated with the electrolyte solution for 60 minutes, and the length of the swollen band before swelling and the length of the swollen band after swelling were measured, respectively. Here, the components of the electrolyte solution used for the swelling evaluation are shown in table 1 below. The swelling characteristics of the swollen band samples were evaluated in the same manner in experimental examples 1-1 to 1-6, except that the samples were impregnated with electrolyte solutions of the components shown in table 1 below.

TABLE 1

Thereafter, the ratio of the length of the swelling tape after expansion to the length of the swelling tape before expansion was calculated and is shown in table 1 and fig. 4. Specifically, FIG. 4 shows calculated ratios of the lengths of the swollen band after swelling in the width direction (transverse direction; TD) and the longitudinal direction (machine direction; MD) relative to the length of the swollen band before swelling after swelling for 60 minutes after immersing the swollen band sample in DMC and electrolyte solutions having the components of Experimental example 1-1, respectively.

Referring to table 1, it was confirmed that the length of the swelling tape after expansion in the longitudinal direction and the width direction was about 140% of the length of the swelling tape before expansion when impregnated with the electrolyte solutions having the components of experimental examples 1-1 to 1-6. Specifically, referring to experimental examples 1-1 to 1-6, it was confirmed that the presence or absence of other solvent components, namely, ethylene Carbonate (EC), propylene Carbonate (PC) and methyl ethyl carbonate (EMC) in addition to Dimethyl Carbonate (DC) and the adjusted content slightly affected the swelling characteristics of the swollen band according to the components of the mixed solvent, but were not significantly different. On the other hand, referring to reference example 1-1 and experimental examples 1-1 to 1-6, it was confirmed that when LiPF ₆ used as an electrolyte was added at about 7wt% and about 15wt%, i.e., when the contents of the electrolytes were different, the difference in the degree of expansion was within about 3%, i.e., the difference was not large. On the other hand, it was confirmed that when the content of the electrolyte was 0%, that is, when the electrolyte was not added, the difference in the degree of expansion was about 15%. From the above results, it can be seen that the presence or absence of the electrolyte shows a relatively large difference in the swelling characteristics of the swelling belt.

Referring to fig. 4, it was confirmed that the length of the swelling tape after swelling in the longitudinal direction and the width direction was about 140% of the length of the swelling tape before swelling when impregnated with the electrolyte solution having the composition of experimental example 1-1. Specifically, it was confirmed that the length expansion of the swelling tape occurred at the same ratio in both the longitudinal direction and the width direction, and that the swelling tape was expanded by about 120% from the central portion to one end portion of the swelling tape before the expansion. From the above results, it is known that the minimum length in the width direction and the longitudinal direction of the swollen band should be attached in order for one end portion of the swollen band to protect one end portion of the first electrode.

Experimental example 2-activation assessment

The secondary batteries prepared in example 1 and comparative example 1 were activated by performing 2 cycles of 4.2V-2.5V, 0.2C charge and 0.2C discharge, respectively, and then disassembled to prepare wound electrode assemblies before and after activation. Then, an end portion of the positive electrode of each of the wound-type electrode assemblies was observed with naked eyes, and the evaluation results are shown in fig. 5 and 6 below.

Specifically, fig. 5 (a) shows a first end portion of a first electrode of a wound-type electrode assembly before activation according to example 1, fig. 5 (b) shows a first end portion of a first electrode of a wound-type electrode assembly after activation according to example 1, fig. 6 (a) shows a first end portion of a first electrode of a wound-type electrode assembly before activation according to comparative example 1, and fig. 6 (b) shows a first end portion of a first electrode of a wound-type electrode assembly after activation according to comparative example 1.

Referring to fig. 5, in the case of the rolled electrode assembly according to example 1, it was confirmed that the swelling tape attached such that one end portion matches with the first end portion of the first electrode before activation was expanded to wrap the first end portion of the first electrode after activation. In this case, the length (2L) of the swelling tape attached on at least one surface of the slit region included in the first electrode was 10mm, and after the step of slitting the longitudinal center portion of the slit region of the first electrode, the length (L) of the swelling tape before swelling was 5mm, the length (L') of the swelling tape after swelling was 7mm, and the swelling length (Ls) of the swelling tape was 2mm in total. In other words, it was confirmed that the length (L') of the swelling tape after expansion was about 140% of the length (L) of the swelling tape before expansion, and was expanded by 1mm on the side from the central portion of the swelling tape before expansion to one end portion, that is, by 120% of the length (L) of the swelling tape before expansion. From the above results, it was confirmed that the rolled electrode assembly including the swelling tape according to the present invention was expanded by the electrolyte solution, and after the expansion, the swelling tape effectively wrapped around the first end portion of the first electrode.

On the other hand, referring to fig. 6, in the case of the wound electrode assembly according to comparative example 1, it was confirmed that the PET tape attached such that one end portion matched with the first end portion of the first electrode before activation did not expand even after activation, and the first end portion of the first electrode was exposed.

Experimental example 3-evaluation of cycle stability

In the 25 ℃ cycle test, the battery characteristics of the secondary batteries prepared in example 1 and comparative example 2 were tested.

Specifically, after 500 cycles, coulombic efficiency was analyzed to check short-circuit behavior during the cycle, room temperature-voltage tracking was performed to evaluate abnormal behavior in more detail, and the evaluation results are shown in fig. 7.

Specifically, (a) of fig. 7 shows the change in coulombic efficiency with respect to the cycle course of the secondary batteries prepared in example 1 and comparative example 2, and (b) of fig. 7 shows the tracking evaluation result of the room temperature-voltage of the secondary batteries prepared in example 1 and comparative example 2 over time.

Referring to (a) of fig. 7, it was confirmed that the secondary battery according to example 1 did not exhibit any particular abnormal behavior, but the secondary battery according to comparative example 2 exhibited abnormal coulomb efficiency behavior, i.e., exhibited leakage current. Further, referring to (b) of fig. 7, it was confirmed that the secondary battery according to example 1 maintained a voltage of 1.0V or more even after 12 hours, but the secondary battery according to comparative example 2 failed to maintain a constant voltage and the voltage gradually decreased with the lapse of time. From this, it can be seen that the separator is damaged and an internal short circuit occurs.

Thereafter, the secondary battery according to example 1 was disassembled and the presence or absence of damage to the separator was visually evaluated, and the result is shown in fig. 8.

Specifically, (a) of fig. 8 is an image showing a state of a portion of the separator facing the first electrode included in the secondary battery prepared in example 1, and (b) of fig. 8 is an image showing a state of a portion of the separator facing the first electrode included in the secondary battery prepared in comparative example 2.

Referring to fig. 8, it was confirmed that damage occurred in the separator of the secondary battery according to comparative example 2, to which the swelling tape was not attached.

Thus, it was confirmed that the secondary battery according to the present invention can prevent an internal short circuit between the positive electrode and the negative electrode even when the electrode assembly is deformed due to shrinkage/expansion of the electrode during charge and discharge of the battery, thereby improving the stability and life characteristics of the battery.

Experimental example 4-roundness evaluation and productivity evaluation

In order to confirm the degree of improvement in the deformation of the secondary batteries prepared in example 1 and comparative example 3, the roundness was evaluated after cycling at 25 ℃ for 20 times, and the results thereof are shown in table 2 and fig. 9. Here, roundness (circularity) (%) means a degree to which the shape of the electrode assembly is more nearly circular. For roundness, the maximum and minimum separation distances between the winding axis and the positive electrode are measured from a Computed Tomography (CT) image of the positive electrode, and a ratio (%) of the minimum separation distance between the winding axis and the positive electrode to 100% of the maximum separation distance between the winding axis and the positive electrode is calculated.

Further, in order to evaluate the productivity of each of the wound-type electrode assemblies, the time required to prepare the wound-type electrode assemblies, that is, the tact time, was measured, and is shown in table 2.

TABLE 2

	Time to birth (seconds)	Roundness (%)
			Example 1	1.55	91
Comparative example 3	3.0	89.0-89.9

Fig. 9 is an image showing the result of roundness evaluation of the secondary batteries prepared in example 1 and comparative example 3. Referring to table 2, in the case of the secondary battery according to comparative example 3, it was confirmed that the tact time was 3.0s, i.e., increased by about two times, and the productivity was poor, as compared with the secondary battery according to example 1, in which the longitudinal end portion of the positive electrode was wrapped with the PET protective tape, and after swelling, a structure similar to that of the secondary battery including the swelling tape according to example 1 was provided.

Thus, it can be seen that the method for manufacturing a rolled electrode assembly according to an exemplary embodiment of the present invention includes a step of attaching a swelling tape attached so as to wrap one longitudinal end portion of a positive electrode while minimizing a separate additional process, and thus enables the rolled electrode assembly including the swelling tape to be provided and manufactured in a continuous process using an existing roll-to-roll processing apparatus, thereby enabling to secure productivity and economic efficiency.

Note that referring to table 2 and fig. 9, in the case of the secondary battery according to comparative example 3, it was confirmed that the roundness was 90% or less, which was similar to or worse than the degree of improvement in safety of the secondary battery according to example 1.

From this, it can be seen that the secondary battery according to the present invention includes a structure in which the swelling tape wraps the longitudinal end portion of the first electrode after expansion, so that even when the electrode assembly is deformed due to shrinkage/expansion of the electrode during charge and discharge of the battery, internal short circuit between the positive electrode and the negative electrode can be prevented to improve stability and life characteristics of the battery, and the effect of relieving internal stress and improving roundness of the core portion is excellent due to the porous material characteristics of the swelling tape.

The foregoing detailed description is intended to illustrate and explain the present invention. Furthermore, the foregoing description is only intended to illustrate and describe the preferred embodiments of the invention, and as described above, the invention is capable of use in various other combinations, modifications, and environments and is capable of changes or modifications within the scope of the inventive concept as disclosed in the present specification, commensurate with the above disclosure, and/or within the skill or knowledge of the relevant art. Thus, the foregoing detailed description of the invention is not intended to limit the invention to the embodiments disclosed. Furthermore, the appended claims should be construed to include other embodiments as well.

Claims

1. A wound electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound,

Wherein the rolled electrode assembly includes a swelling tape attached to at least one surface of the first electrode,

Wherein the first electrode includes a first end portion and a second end portion, winding is started from the first end portion in a longitudinal direction, and winding is ended at the second end portion, and

Wherein the swelling tape is attached such that one end portion mates with the first end portion of the first electrode.

2. The rolled electrode assembly according to claim 1, wherein a length of the swelling tape in a width direction is 60% or more and 100% or less of a width of 100% of the first electrode.

3. The rolled electrode assembly according to claim 1, wherein the length of the swelling tape in the longitudinal direction is 250% or more and 3500% or less of the thickness of 100% of the first electrode.

4. The rolled electrode assembly according to claim 1, wherein the swelling tape is expanded by an electrolyte solution, and

Wherein, after expansion, the swelling tape wraps around the first end portion of the first electrode.

5. The wound electrode assembly of claim 4, wherein the electrolyte solution comprises 70wt% or more of any one of the following: ethylene Carbonate (EC), propylene Carbonate (PC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC) and mixtures thereof.

6. The rolled electrode assembly according to claim 4, wherein the length of the swelling tape after being impregnated with an electrolyte solution comprising 45wt% of dimethyl carbonate, 20wt% of ethylene carbonate, 15wt% of ethylmethyl carbonate, and 15wt% of LiPF ₆ as an electrolyte for 60 minutes is 120% or more and 160% or less of the length of the swelling tape before being expanded.

7. The rolled electrode assembly of claim 1 wherein the swelling tape comprises a base layer and an adhesive layer, and

Wherein the adhesive layer is disposed on at least one surface of the base layer.

8. The rolled electrode assembly of claim 7 wherein the adhesive layer comprises a pressure sensitive adhesive comprising a polyacrylic resin.

9. The rolled electrode assembly of claim 7, wherein the adhesive layer comprises one or more comonomers selected from the group consisting of polymethyl methacrylate (PMMA), polyethyl methacrylate (PEMA), and polybutyl methacrylate (PBMA).

10. The rolled electrode assembly of claim 7 wherein the base layer comprises a urethane-based resin.

11. The rolled electrode assembly of claim 1 wherein the first electrode is a positive electrode and the second electrode is a negative electrode.

12. The rolled electrode assembly according to claim 1, wherein the first electrode comprises a current collector and an active material layer disposed on the current collector.

13. A method for manufacturing a wound-type electrode assembly in which a first electrode, a first separator, a second electrode, and a second separator are sequentially stacked and wound, the method comprising:

(a) Transferring the first electrode in a roll-to-roll manner;

(b) Attaching a swelling tape on at least one surface of a slit region included in the first electrode; and

(C) Dividing a longitudinal central portion of the divided region of the first electrode,

Wherein in the attaching of (b), the swelling tape is attached such that a longitudinal center portion of the swelling tape matches the longitudinal center portion of the slit region of the first electrode, and

Wherein in the slitting of (c), the longitudinal center portion of the slitting region is slit such that the first electrode is provided with a first end portion from which winding is started in the longitudinal direction and a second end portion at which winding is ended.

14. The method according to claim 13, wherein a length of the swelling tape in a width direction is 60% or more and 100% or less of a width of 100% of the first electrode.

15. The method according to claim 13, wherein a length of the swelling tape in a longitudinal direction is 500% or more and 7000% or less of a thickness of 100% of the first electrode.

16. The method of claim 13, wherein the first electrode is a positive electrode and the second electrode is a negative electrode.

17. A wound electrode assembly manufactured by the method according to claim 13.

18. A secondary battery, comprising:

the rolled electrode assembly according to any one of claims 1-12, 17; and

And a battery case for accommodating the electrode assembly.

19. The secondary battery according to claim 18, wherein the battery case has a cylindrical shape.