KR20210124063A - Swelling tape for secondary battery and cylindrical secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a swelling tape which comprises a base material layer and an adhesive swelling layer, wherein the adhesive swelling layer comprises a water-based self-recovery binder; an electrode assembly having the swelling tape attached on an outer circumference thereof; and a secondary battery comprising the same. According to the present invention, movement of the electrode assembly in the battery can be effectively prevented.

Description

Swelling tape for secondary battery and cylindrical secondary battery comprising same

The present invention relates to a swelling tape for a secondary battery and a cylindrical secondary battery including the same.

Due to the development of the information society, personal IT devices and computer networks are developed, and the overall society's dependence on electric energy increases with it.

Among the technologies developed for this purpose, the most suitable technology for various uses is a secondary battery-based technology, and among them, a lithium secondary battery with the highest theoretical energy density is in the spotlight.

Lithium secondary batteries have an operating voltage of about 3.6V, which has about three times the capacity of nickel-cadmium batteries or nickel-hydrogen batteries, which are often used as power sources for electronic equipment, and has a high energy density per unit weight. is in a rapidly increasing trend.

A lithium secondary battery consists of an electrode assembly in which a positive electrode plate coated with a positive electrode active material and a negative electrode plate coated with a negative electrode active material are disposed with a separator interposed therebetween, an electrolyte, and a packaging material for sealingly accommodating them together.

The lithium secondary battery may be classified into a can-type secondary battery and a pouch-type secondary battery according to the shape of the battery case. The can-type secondary battery can be further classified into a cylindrical secondary battery and a prismatic secondary battery according to the shape of the metal can, and can be manufactured by accommodating a jelly roll-type electrode assembly in which a positive electrode, a separator, and a negative electrode are wound in a metal can. . The pouch-type secondary battery may be manufactured by embedding a stack-type electrode assembly in which a plurality of positive electrodes, separators, and negative electrodes are sequentially stacked in a pouch made of an aluminum laminate sheet, and then sealing.

On the other hand, since the lithium secondary battery is frequently moved and can be accommodated in a machine that is subjected to strong vibration like a car, portability and strong vibration-resistant characteristics are required.

However, in the case of a cylindrical secondary battery, in order to accommodate the electrode assembly inside the cylindrical battery case, since the electrode assembly is formed in a smaller size than that of the cylindrical battery case (metal can), there is a gap between the electrode assembly and the inner wall of the battery case. (gap) is formed. Such a gap causes the electrode assembly to flow up and down or left and right inside the battery case when vibration or shock is applied from the outside due to a drop or the like.

The flow of the electrode assembly may cause an increase in internal resistance of the battery or a power insensitivity phenomenon of the secondary battery due to cutting of a tab connected between the electrode assembly and the cap assembly. In addition, by applying an impact to the cap assembly coupled to the upper open part of the secondary battery, the sealing part is damaged or separated, thereby causing a problem in which the electrolyte inside the secondary battery is leaked.

In order to prevent the movement of the electrode assembly, a method using a special tape such as a swelling tape is recently applied.

As shown in FIG. 1 , a swelling tape consisting of an adhesive layer 110 and a swelling layer 120 is attached to the outer peripheral surface of the jelly-roll type electrode assembly 100 on which the positive electrode, the separator and the negative electrode are wound, and this is a cylindrical battery When the electrolyte is injected after being accommodated in the case, the swelling layer expands and fills a gap existing between the electrode assembly and the battery case, thereby preventing the electrode assembly from flowing.

As the swelling layer, a conventional urethane resin such as thermoplastic polyurethane (TPU, Thermoplastic polyurethane) or curable urethane is used. However, in the case of the urethane resin, heat resistance and fire resistance are low, and since vibration or shock is easily transmitted to the electrode assembly, there is a disadvantage in that it is weak in preventing vibration or shock inside the battery.

Accordingly, there is a need to develop a new swelling tape capable of effectively preventing the electrode assembly from flowing even in strong vibration or impact.

Korean Patent Publication No. 10-2016-0074787

The present invention has been proposed to solve the above problems, and an object of the present invention is to provide a swelling tape for a secondary battery that can effectively prevent the flow of an electrode assembly inside the battery.

Another object of the present invention is to provide an electrode assembly to which the swelling tape for secondary batteries is attached to an outer circumferential surface, and a cylindrical secondary battery including the same.

According to one embodiment, the present invention provides a swelling tape for a secondary battery comprising a base layer and an adhesive swelling layer, wherein the adhesive swelling layer includes a water-based self-healing binder.

The swelling tape for secondary batteries may further include at least one of an adhesive layer and a back coating layer.

According to another embodiment, the present invention provides an electrode assembly in which the swelling tape for a secondary battery is attached to an outer circumferential surface.

According to another embodiment, the present invention provides a cylindrical secondary battery including the electrode assembly, the electrolyte, and a cylindrical battery case accommodating the electrode assembly and the electrolyte.

The swelling tape of the present invention includes an adhesive swelling layer containing a water-based self-healing binder on at least one surface of both surfaces of the base layer, thereby preventing the electrode assembly from being unwound, and at the same time, the electrode assembly and the battery case at low cost By filling the gap between the inner walls, it is possible to effectively prevent the electrode assembly from flowing. Accordingly, it is possible to prevent the secondary battery from being damaged, ignition and explosion due to a short circuit due to deformation of the electrode assembly, and also to prevent electrolyte leakage due to breakage of the coupling portion of the cap assembly. As a result, it is possible to realize a secondary battery having high stability and effectively improved resistance increase rate and power insensitivity phenomenon.

The following drawings attached to the present specification illustrate preferred embodiments of the present invention, and serve to further understand the technical spirit of the present invention together with the above-described contents of the present invention, so the present invention is limited to the matters described in such drawings It should not be construed as being limited.
1 is a schematic view of applying a swelling tape on a conventional jelly-roll type electrode assembly.
2 is a cross-sectional view of a swelling tape according to an embodiment of the present invention.
3 is a schematic diagram exemplarily illustrating a process in which the swelling tape is formed into a three-dimensional shape during a manufacturing process of a secondary battery according to an embodiment of the present invention.

Hereinafter, with reference to the accompanying drawings, various embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. The present invention may be embodied in many different forms and is not limited to the embodiments described herein.

As used herein, the term "swelling tape" is located in a gap between two objects that are spaced apart from each other, fills the gap, and if necessary, serves to fix the two objects to each other. It can mean tape. In one example, the swelling tape is attached to any one of the two objects through the adhesive layer, by the mutual balance of the force generated as the swelling layer expands and the fixing force of the pressure-sensitive adhesive layer. Refers to a tape capable of implementing a three-dimensional shape that can fill the gap.

swelling tape

The swelling tape according to the present invention includes a base layer and an adhesive swelling layer,

The adhesive swelling layer may include a water-based self-healing binder.

(1) base layer

The base layer is a film or sheet-shaped layer having deformation (expansion) properties when in contact with a fluid such as an electrolyte, and may have a shape such as a circle, a triangle, or an amorphous shape in addition to a square shape.

As the base layer, various base layers commonly used in conventional swelling tapes may be used without limitation, and specifically, polyacrylate, thermoplastic polyurethane (TPU), polyvinyl chloride, polyethylene terephthalate, polyethylene, polypropylene, poly It may include at least one polymer material of amide, polycarbonate, polyimide, and polystyrene, and preferably, it may include at least one selected from the group consisting of polyurethane and polystyrene.

The thickness of the base layer may be selected in consideration of the three-dimensional shape to be implemented or the size of the gap to be filled, and may be specifically formed to a thickness of 10 μm to 40 μm, specifically 20 μm to 40 μm.

(2) adhesive swelling layer

Tackiness of the present invention The swelling layer is a layer capable of filling the gap between the electrode assembly and the battery case by swelling when the electrolyte is impregnated or heat is applied, and a volume increase rate of up to 100% or more can be realized.

this stickiness As a component of the swelling layer, a water-based self-healing binder having a glass transition temperature of -50°C to -30°C may be included.

The water-based self-healing binder is a polymer having a property of swelling (expanding) by contact with an organic solvent contained in the electrolyte or swelling by heat, and a representative example thereof is CMC (Ceramic Matrix Composite), arginate. And it may include at least one compound of chitosan (Chitosan). Specifically, the water-based self-healing binder may include at least one compound selected from the group consisting of arginate and chitosan.

The arginate is a very high molecular weight polymer, and since it has excellent self-healing ability, when it is used for swelling tape, it has an excellent effect of filling the internal gap during impact, so that the flow of the electrode assembly can be effectively suppressed. have. In addition, since it has a strong anion component in the side chain, there is an advantage that the ion movement in the electrolyte can be smoothed and the battery driving characteristics can be expressed even under an electric field. The arginate specifically refers to sodium arginate, and in addition to this, ethyl lauroyl arginate or propylene glycol arginate may be applied.

The chitosan is an environmentally friendly material, and has an advantage in that it is inexpensive and has excellent binding performance because it contains a large amount of hydroxyl groups. Therefore, when this is used for the swelling tape, it is possible to improve the adhesion of the swelling tape to the electrode assembly, thereby manufacturing a secondary battery with excellent processability and reduced manufacturing cost. In addition, since the chitosan contains a nitrogen element in its structure, when it is used in a swelling tape, the adsorption and decomposition ability of oxygen is improved by the oxygen reduction reaction by the nitrogen atom, thereby further improving the electrical conductivity of the secondary battery can do.

In the present invention, by using a water-based self-healing binder for the swelling tape, high adhesiveness is ensured, and the use of an additional adhesive such as an acrylic pressure sensitive adhesive ('PSA') can be omitted, and the The gap between the electrode assembly and the battery case may be completely filled by the expansion properties. Therefore, it is possible to prevent the movement of the electrode assembly even when vibration or shock is applied from the outside due to dropping of the battery, and thus a stable secondary battery with improved impact resistance can be realized.

Meanwhile, the adhesive swelling layer may be formed on at least one surface of both surfaces of the base layer.

The adhesive swelling layer may be prepared by dissolving a water-based self-healing binder in water to prepare a binder composition, then coating and drying it on a base layer.

The adhesive swelling layer may be formed to a thickness of about 10 to 50%, specifically, 10 to 30% of the total thickness of the base layer. When the thickness of the adhesive swelling layer satisfies the above range, a gap between the electrode assembly (jelly roll) and the battery case may be filled to provide a battery resistant to external shocks such as vibration. That is, when the thickness of the adhesive swelling layer is about 10% or more with respect to the total thickness of the base layer, the purpose of preventing the electrode assembly from flowing by sufficiently filling the gap may be realized. On the other hand, when the thickness of the adhesive swelling layer exceeds about 50% with respect to the total thickness of the base layer, since the outer diameter of the electrode assembly (J/R) increases due to the increase in the thickness of the swelling tape, the electrode assembly expands during cycle driving Deformation of the cell may occur, resulting in deterioration of cell performance.

On the other hand, the adhesive swelling layer may be formed in the range of 50% to 99%, preferably 70% to 95% of the total area of one surface of the base layer.

When the area of the adhesive swelling layer satisfies the above range, it is possible to implement cost-effective vibration resistance. If the area of the adhesive swelling layer exceeds 99% of the total area of the base layer, it is economically undesirable. The effect may be negligible.

Meanwhile, the swelling tape of the present invention may further include at least one of an adhesive layer and a back coating layer, which will be described later, if necessary, in order to further improve the adhesive force and the swelling effect.

(3) adhesive layer

The adhesive layer is a layer added to further improve the adhesion of the swelling tape to the electrode assembly, and may be designed to implement an appropriate adhesive force to the electrode assembly, that is, an appropriate peel force.

The peeling force of the adhesive layer can be changed according to the size of the three-dimensional shape to be implemented or the gap to be filled, and the lower limit thereof is 100 gf/25mm or more, 200 gf/25mm or more, 400gf/25mm or more, 600 gf/25mm or more. or more, 800 gf/25mm or more, 1,000 gf/25mm or more, 1,200 gf/25mm or more, 1,400 gf/25mm or more, 1,600 gf/25mm or more, or 1800 gf/25mm or more. In addition, the upper limit of the peeling force of the adhesive layer is not particularly limited as long as it has a general range, but may be about 5,000 gf/25mm or less.

The peel force is a peel force measured at room temperature, and is a result of measurement at a peeling rate of 5 mm/sec and a peeling angle of 180°. The "room temperature" is a natural temperature that is not heated or cooled, for example, from about 10°C to about 30°C, specifically from about 20°C to about 30°C, more specifically, it may mean a temperature of about 25°C. have.

When the peeling force of the adhesive layer exceeds the above range, deformation of the swelling layer may be excessively suppressed, thereby making it difficult to implement a three-dimensional shape. In addition, when the peeling force of the adhesive layer is less than the above range, the effect of implementing the adhesiveness to be secured when the swelling tape is expanded may be insignificant.

The adhesive layer may include an acrylic polymer having a weight average molecular weight (Mw) of 400,000 or more. Specifically, the acrylic polymer may include a polymer in which a (meth)acrylic acid ester monomer and a copolymerizable monomer having a crosslinkable functional group are polymerized. At this time, the weight ratio of each monomer is not particularly limited, and may be appropriately designed in consideration of a desired peeling force.

Meanwhile, the (meth)acrylic acid ester monomer may be an alkyl (meth)acrylate having an alkyl group having 1 to 15 carbon atoms in consideration of the cohesive force of the pressure-sensitive adhesive, the glass transition temperature or the adhesiveness. Such monomers include methyl (meth)acrylate, ethyl (meth)acrylate, n-propyl (meth)acrylate, isopropyl (meth)acrylate, n-butyl (meth)acrylate, t-butyl (meth)acrylate Acrylate, sec-butyl (meth)acrylate, pentyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, 2-ethylbutyl (meth)acrylate, n-octyl (meth)acrylate, isooctyl One or two or more of (meth)acrylate, isononyl (meth)acrylate, lauryl (meth)acrylate, and tetradecyl (meth)acrylate may be exemplified, but the present invention is not limited thereto.

The copolymerizable monomer having the crosslinkable functional group may be copolymerized with the (meth)acrylic acid ester monomer through crosslinking, and after copolymerization, a monomer capable of providing a crosslinking point capable of reacting with the polyfunctional crosslinking agent in the main chain of the polymer may include. The crosslinkable functional group may be a hydroxyl group, a carboxyl group, an isocyanate group, a glycidyl group or an amide group, and in some cases, a photocrosslinkable functional group such as an acryloyl group or a methacryloyl group. Representative examples of the copolymerizable monomer having the crosslinkable functional group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, and 6-hydroxy a monomer having a hydroxyl group such as hexyl (meth)acrylate, 8-hydroxyoctyl (meth)acrylate, 2-hydroxyethylene glycol (meth)acrylate or 2-hydroxypropylene glycol (meth)acrylate; (meth)acrylic acid, 2-(meth)acryloyloxy acetic acid, 3-(meth)acryloyloxy propyl acid, 4-(meth)acryloyloxy butyric acid, acrylic acid duplex, itaconic acid, maleic acid and monomers having a carboxyl group such as maleic anhydride; and glycidyl (meth)acrylate, (meth)acrylamide, N-vinyl pyrrolidone, or N-vinyl caprolactam, but is not limited thereto. One or two or more of these monomers may be included in the polymer.

The adhesive layer may be formed to a thickness of 5 μm to 20 μm, specifically 10 μm to 20 μm. If the thickness of the adhesive layer exceeds 20 μm, the outer diameter (volume) of the jelly roll electrode assembly increases and electrolyte dispersibility is lowered due to productivity problems and a decrease in the internal space of the cell, so that the safety and overall performance of the secondary battery may be reduced. can

On the other hand, the adhesive layer may be formed between the base layer and the adhesive swelling layer, or may be formed on at least one surface of the substrate layer and the adhesive swelling layer in order to secure more improved adhesion.

(4) back coating layer

The back coating layer is a layer added to further improve the gap filling effect, and it swells while partially releasing directionality by contact and impregnation with an electrolyte, or a thermosetting adhesive material that exhibits adhesiveness when heat is applied more than a predetermined amount can be made with

Specifically, the back coating layer may include polyimide, polybutylene terephthalate (PBT), polyamideimide (PAI), perfluoroalkoxy (PFA), and polysulfone (PSF). ), polyarylsulfone (PAS), polytetrafluoroethylene (PTFE), fluorinated ethylene propylene (FEP), ethylenetetrafluoroethylene (ETPE), and polyethylene naphthalene , PEN) may include a single substance or a mixture of two or more selected from the group consisting of.

In the case of the back coating layer, since adhesiveness is expressed by heat, adhesiveness is not expressed when the electrode assembly to which the swelling tape to which the back coating layer is applied is attached is inserted into the battery case, so that it can be easily accommodated.

Then, when the electrolyte is injected into the battery case, the gap may be filled while the rear coating layer expands. Moreover, when the heat application process is performed during the manufacturing process of the secondary battery, the adhesiveness of the back coating layer is expressed to improve the adhesive force of the swelling tape, and the flow of the electrode assembly can be more effectively improved. In this case, the heat application process may be an aging process performed during the existing secondary battery manufacturing process, or a separate additional process may be added.

The back coating layer may be formed between the base layer and the adhesive swelling layer, or may be formed on the adhesive swelling layer in order to secure improved adhesion.

On the other hand, the total thickness of the swelling tape of the present invention is preferably formed to a thickness of 200 μm or less, specifically 20 μm to 200 μm, more specifically 20 μm to 150 μm, and more specifically 40 μm to 120 μm. If the thickness of the swelling tape is less than 20 μm, it is difficult to secure a sufficient thickness even by heat or contact with an electrolyte, so that it is difficult to secure the effect of preventing fluidity of the electrode assembly. In addition, when the thickness of the swelling tape exceeds 200 μm, it is not easy to accommodate the electrode assembly inside the battery case, and the space between the battery case and the electrode assembly is reduced to lower electrolyte dispersibility, Since the electrolyte injection amount is reduced by that much, it is difficult to secure the capacity of the secondary battery.

The swelling tape of the present invention may be manufactured in various structures including a base layer and a swelling tape, and optionally an adhesive layer and/or a back coating layer. Specifically, Figure 2 schematically shows examples of various configurations of the swelling tape according to the embodiment of the present invention, respectively.

That is, the swelling tape 200 of the present invention according to an embodiment may include a base layer 202 and an adhesive swelling layer 220 formed on one surface of the base layer, as shown in FIG. 2A .

In addition, the swelling tape 200 of the present invention according to one embodiment, as shown in Figure 2b, the adhesive swelling layer (220 (a) and 220 (b)) formed on both sides of the base layer 202. can

In addition, as shown in FIG. 2c, the swelling tape 200 of the present invention according to an embodiment includes an adhesive layer 201, a base layer 202, a back coating layer 203, and an adhesive swelling layer, and the The back coating layer 203 may be formed between the base layer 202 and the adhesive swelling layer 220 .

Electrode assembly with swelling tape attached to the outer circumferential surface

Next, an electrode assembly to which the swelling tape for a secondary battery according to the present invention is attached to the outer peripheral surface will be described.

(1) Swelling tape for secondary batteries

Since the configuration of the swelling tape for secondary batteries has been described above, a description thereof will be omitted, and the form of the swelling tape attached to the outer peripheral surface of the electrode assembly will be described below.

The swelling tape of the present invention maintains the shape of the electrode assembly on the outer circumferential surface of the wound electrode assembly, and is positioned between the outer circumferential surface of the electrode assembly and the inner surface of the battery case to prevent the electrode assembly from flowing inside the battery case.

Specifically, the swelling tape of the present invention may be attached to surround the entire height of the outer circumferential surface of the electrode assembly, and more preferably, may be attached to a portion of the outer circumferential surface of the electrode assembly except for a portion of the upper end and the lower end.

The upper end of the electrode assembly serves as a space for the electrolyte to permeate between the battery case and the electrode assembly, and the lower end is a portion where the electrolyte injected into the bottom of the battery case comes into contact with the electrode assembly. Therefore, considering the impregnability of the electrolyte impregnated in the electrode assembly, it is preferable not to attach the swelling tape to the upper and lower portions of the electrode assembly.

In addition, the swelling tape may be wound and attached so as to cover the entire length of the outer circumferential surface of the electrode assembly, and in order to prevent fluidity of the electrode assembly, it is preferable to wind and attach it at least once within the range covering the entire length of the outer circumferential surface of the electrode assembly. do.

The length and thickness of the swelling tape of the present invention is not necessarily limited because it can be variably deformed according to the specifications of the battery. ), or less than or equal to about 1% to 10% or less, and most preferably less than about 10% or less. If the minor length (width) of the swelling tape is less than 10% based on the height (length) of the electrode assembly, which will be described later, there is a disadvantage in that the effect of preventing the electrode assembly from flowing cannot be sufficiently implemented. In addition, when the minor axis length (width) of the swelling tape is 1% or more longer than the height (length) of the electrode assembly to be described later, the swelling tape is attached to the upper and lower portions of the electrode assembly, so that the electrolyte impregnating property is There is a disadvantage that this is reduced.

(2) electrode assembly

Next, the electrode assembly will be described.

The electrode assembly according to the present invention includes a positive electrode, a negative electrode, and a separator (not shown) interposed between the positive electrode and the negative electrode to electrically insulate, wherein the positive electrode, the separator, and the negative electrode are wound together in a jelly-roll shape to form can be

i) anode

The positive electrode constituting the electrode assembly according to the present invention may include a positive electrode active material layer including a positive electrode active material, and if necessary, the positive electrode active material layer may further include a conductive material and/or a binder.

The cathode active material may include one or more metals such as cobalt, manganese, nickel, or aluminum and lithium metal oxide including lithium. More specifically, the lithium metal oxide is a lithium-manganese oxide (eg, LiMnO ₂ , LiMn ₂ O _{4 ,} etc.), a lithium-cobalt-based oxide (eg, LiCoO ₂ etc.), a lithium-nickel-based oxide ( For example, LiNiO ₂ etc.), lithium-nickel-manganese oxide (for example, LiNi _1-Y Mn _Y O ₂ (here, 0<Y<1), LiMn _2-z Ni _z O ₄ (here , 0<Z<2, etc.), lithium-nickel-cobalt-based oxides (eg, LiNi _1-Y1 Co _Y1 O ₂ (here, 0<Y1<1), etc.), lithium-manganese-cobalt-based oxides Oxides (eg, LiCo _1-Y2 Mn _Y2 O ₂ (here, 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (here, 0<Z1<2), etc.), lithium-nickel- Manganese-cobalt-based oxide (eg, Li(Ni _p Co _q Mn _r1 )O ₂ (here, 0<p<1, 0<q<1, 0<r1<1, p+q+r1=1) ) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium-nickel -Cobalt-transition metal (M) oxide (eg, Li(Ni _p2 Co _q2 Mn _r3 M _S2 )O ₂ , where M consists of Al, Fe, V, Cr, Ti, Ta, Mg and Mo. is selected from the group, and p2, q2, r3 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+q2+ r3+s2=1), etc.) and the like, and any one or two or more compounds may be included.

The positive active material may be included in an amount of 90 wt% to 99 wt%, specifically 93 wt% to 98 wt%, based on the total weight of the solid content in the cathode active material layer.

The conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and for example, carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black. carbon powder; Graphite powder, such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers and metal fibers; metal powders such as carbon fluoride, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; A conductive material such as a polyphenylene derivative may be used.

The conductive material is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the positive electrode active material layer.

The binder is a component serving to improve adhesion between the positive active material particles and adhesion between the positive active material and the current collector, and is typically added in an amount of 1 to 30% by weight based on the total weight of the solid content in the positive active material layer. Examples of such a binder include a fluororesin-based binder including polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE); a rubber binder including styrene-butadiene rubber (SBR), acrylonitrile-butadiene rubber, and styrene-isoprene rubber; Cellulose binders including carboxyl methyl cellulose (CMC), starch, hydroxypropyl cellulose, and regenerated cellulose; a polyalcohol-based binder comprising polyvinyl alcohol; Polyolefin-based binders including polyethylene and polypropylene; polyimide-based binders; polyester-based binders; and silane-based binders.

* The positive electrode of the present invention may be manufactured according to a method for manufacturing a positive electrode known in the art. For example, in the positive electrode, a positive electrode slurry prepared by dissolving or dispersing a positive electrode active material, a binder and/or a conductive material in a solvent is applied on a positive electrode current collector, followed by drying and rolling to form a positive electrode active material layer; Alternatively, the cathode active material layer may be cast on a separate support, and then a film obtained by peeling the support may be laminated on a cathode current collector.

The positive electrode current collector is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon on the surface of aluminum or stainless steel. , nickel, titanium, silver, etc. may be used. The positive electrode current collector may form fine concavities and convexities on the surface to enhance bonding strength with a positive electrode active material, which will be described later.

The solvent may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount having a desirable viscosity when the positive active material and optionally a binder and a conductive material are included. For example, it may be included such that the solid content concentration in the active material slurry including the positive electrode active material and, optionally, the binder and the conductive material is 10 wt% to 70 wt%, preferably 20 wt% to 60 wt%.

ii) cathode

Next, the negative electrode constituting the electrode assembly according to the present invention includes an anode active material layer including an anode active material, and the anode active material layer may further include a conductive material and/or a binder, if necessary.

The negative active material is natural graphite, artificial graphite, carbonaceous material; lithium-containing titanium composite oxide (LTO), Si, Sn, Li, Zn, Mg, Cd, Ce, Ni or Fe metals (Me); alloys composed of the metals (Me); oxides of the above metals; and one or more negative active materials selected from the group consisting of a composite of the metal and carbon.

The anode active material may be included in an amount of 80 wt% to 99 wt% based on the total weight of the solid content in the anode active material layer.

The conductive material and the binder may be the same or different from those used in manufacturing the positive electrode. In this case, the conductive material may be added in an amount of 1 to 20% by weight based on the total weight of the solid content in the active material layer, and the binder may be added in an amount of 1 to 30% by weight based on the total weight of the solid content in the negative active material layer.

The negative electrode may be manufactured according to a method for manufacturing a negative electrode known in the art. For example, the negative electrode is a method of forming a negative electrode active material layer by applying a negative electrode active material slurry prepared by dissolving or dispersing a negative electrode active material and optionally a binder and a conductive material in a solvent on the negative electrode current collector, rolling and drying the negative electrode active material layer, or It can be prepared by casting the anode active material layer on a separate support and then laminating a film obtained by peeling the support on the anode current collector.

The negative electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. For example, a surface of copper, stainless steel, aluminum, nickel, titanium, sintered carbon, copper or stainless steel. Carbon, nickel, titanium, a surface-treated one with silver, etc., an aluminum-cadmium alloy, etc. may be used. In addition, like the positive electrode current collector, it is possible to strengthen the bonding force of the negative electrode active material by forming fine irregularities on the surface, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven body.

The solvent may include water or an organic solvent such as NMP or alcohol, and may be used in an amount having a desirable viscosity when the negative electrode active material and, optionally, a binder and a conductive material are included. For example, it may be included such that the concentration of solids in the active material slurry including the negative active material and, optionally, the binder and the conductive material is 50 wt% to 75 wt%, preferably 50 wt% to 65 wt%.

iii) separator

The separator included in the electrode assembly according to the present invention is a conventional porous polymer film conventionally used as a separator, for example, ethylene homopolymer, propylene homopolymer, ethylene/butene copolymer, ethylene/hexene copolymer, and ethylene/methacrylic. A porous polymer film made of polyolefin such as a rate copolymer may be used alone or by laminating them, and _{a polyolefin-based porous polymer film coated with inorganic particles (eg, Al 2} O ₃ ) or a conventional porous nonwoven fabric, for example A nonwoven fabric made of glass fiber, polyethylene terephthalate fiber, etc. having a high melting point may be used, but is not limited thereto.

secondary battery

Next, a lithium secondary battery according to the present invention will be described.

A lithium secondary battery according to the present invention provides a cylindrical secondary battery comprising an electrode assembly having a swelling tape for a secondary battery attached to an outer circumferential surface, an electrolyte, and a cylindrical battery case accommodating the electrode assembly and the electrolyte. Since the electrode assembly to which the swelling tape for the secondary battery is attached to the outer circumferential surface has been described above, a description thereof will be omitted, and other components will be described below.

(1) electrolyte

The cylindrical secondary battery according to the present invention includes an electrolyte so that lithium ions generated by an electrochemical reaction in an electrode can move during charging and discharging.

As the electrolyte, a liquid electrolyte containing a non-aqueous organic solvent in which a lithium salt is dissolved, or a gel polymer electrolyte containing a polymer resin capable of being gelled in the non-aqueous organic solvent may be used without limitation.

As the lithium salt, various lithium salts commonly used in electrolytes for lithium secondary batteries may be used without limitation. For example, the lithium salt includes Li ^{+ as a cation and F -} , Cl ^- , Br ^- , I ^- , NO ₃ ^- , N(CN) ₂ ^- , BF ₄ ^- , ClO ₄ ^- as an anion. , AlO ₄ ^- , AlCl ₄ ^- , PF ₆ ^- , SbF ₆ ^- , AsF ₆ ^- , B ₁₀ Cl ₁₀ ^- , BF ₂ C ₂ O ₄ ^- , BC ₄ O ₈ ^- , PF ₄ C ₂ O ₄ ^- , PF ₂ C ₄ O ₈ ^- , (CF ₃ ) ₂ PF ₄ ^- , (CF ₃ ) ₃ PF ₃ ^- , (CF ₃ ) ₄ PF ₂ ^- , (CF ₃ ) ₅ PF ^- , (CF ₃ ) ₆ P ^- , CF ₃ SO ₃ ^- , C ₄ F ₉ SO ₃ ^- , CF ₃ CF ₂ SO ₃ ^- , (CF ₃ SO ₂ ) ₂ N ^- , (FSO ₂ ) ₂ N ^- , CF ₃ CF ₂ (CF ₃ ) ₂ CO ^- , (CF ₃ SO ₂ ) ₂ CH ^- , CH ₃ SO ₃ ^- , CF ₃ (CF ₂ ) ₇ SO ₃ ^- , CF ₃ CO ₂ ^- , CH ₃ CO ₂ ^- , SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ⁻ may include at least one selected from the group consisting of.

Specifically, the lithium salt is LiCl, LiBr, LiI, LiBF ₄ , LiClO ₄ , LiAlO ₄ , LiAlCl ₄ , LiPF ₆ , LiSbF ₆ , LiAsF ₆ , LiB ₁₀ Cl ₁₀ , LiBOB (LiB(C ₂ O ₄ ) ₂ ) , LiCF ₃ SO ₃ , LiTFSI (LiN(SO ₂ CF ₃ ) ₂ ), LiFSI (LiN(SO ₂ F) ₂ ), LiCH ₃ SO ₃ , LiCF ₃ CO ₂ , LiCH ₃ CO _{2 ,} and LiBETI (LiN(SO _{2 )} and at least one selected from the group consisting of _{CF 2} CF ₃ ) _{2. Specifically, the lithium salt is LiBF 4} , LiClO ₄ , LiPF ₆ , LiBOB (LiB(C ₂ O ₄ ) ₂ ), LiCF ₃ SO ₃ , LiTFSI (LiN(SO ₂ CF ₃ ) ₂ ), LiFSI (LiN(SO ₂ F) ₂ ) and LiBETI (LiN(SO ₂ CF ₂ CF ₃ ) _{2 )} can

The lithium salt may be appropriately changed within the range that can be used in general, but to be included in the electrolyte at a concentration of 0.8 M to 4.0 M, specifically, at a concentration of 1.0M to 3.0M, in order to obtain an optimal effect of forming a film for preventing corrosion of the electrode surface. can

The non-aqueous organic solvent may include a cyclic carbonate-based organic solvent, a linear carbonate-based organic solvent, or a mixed organic solvent thereof.

The cyclic carbonate-based organic solvent is a high-viscosity organic solvent that has a high dielectric constant and can well dissociate lithium salts in the electrolyte, and specific examples thereof include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene. At least one organic solvent selected from the group consisting of carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, 2,3-pentylene carbonate and vinylene carbonate, among them, ethylene carbonate may include.

In addition, the linear carbonate-based organic solvent is an organic solvent having a low viscosity and a low dielectric constant, and representative examples thereof include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethylmethyl carbonate ( EMC), at least one organic solvent selected from the group consisting of methylpropyl carbonate, and ethylpropyl carbonate may be used, and specifically, it may include at least one or more of dimethyl carbonate, ethylmethyl carbonate, and dipropyl carbonate.

The electrolyte may easily permeate between the polymer and the polymer constituting the swelling tape for a secondary battery of the present invention, and may be expanded.

(2) Cylindrical battery case

The cylindrical secondary battery according to the present invention may include a cylindrical battery case for accommodating an electrode assembly and a cap assembly for sealing the cylindrical battery case on an upper portion of the cylindrical battery case.

The cap assembly may further include an insulating gasket, and may allow current generated in the electrode assembly to flow to an external device.

The inner surface of the cylindrical battery case of the present invention may be made of a material having relatively good affinity with the electrolyte, such as aluminum (Al) or iron (Fe).

The cylindrical secondary battery 300 according to the present invention may be manufactured by a conventional method.

3, after attaching the swelling tape 310a for a secondary battery of the present invention to the outer circumferential surface of the electrode assembly 330, the electrode assembly 330 to which the swelling tape 310a is attached is applied to the cylindrical battery case. It is stored in (cylindrical can) 320 .

Then, the above-described electrolyte (not shown) is injected into the cylindrical battery case 320 .

As a result, while the swelling tape 310a attached to the outside of the electrode assembly 330 and the electrolyte are in contact, the non-aqueous organic solvent contained in the electrolyte is a base layer and an adhesive swelling layer constituting the swelling tape 310a, etc. Penetrating between the polymer constituting the polymer and the polymer, the swelling tape first expands (not shown). Accordingly, a gap between the electrode assembly 330 and the battery case 320 may be filled.

Then, after assembling the secondary battery by a known method of fixing the cap assembly to the opening of the battery case, a conventional post-treatment process, such as a chemical conversion process and an aging process, may be performed to manufacture the secondary battery.

In this case, the chemical formation process is a process of activating the battery by repeating charging and discharging after assembling the battery. In the chemical conversion process, it is inserted lithium ions emitted from the lithium metal oxide used as the positive electrode upon charging to move to a carbon electrode used as a cathode, wherein the lithium is because reactivity is strongly reacts with the carbon negative electrode, Li ₂ CO _3, LiO , LiOH, etc. are produced, and these form a film called SEI (Solid Electrolyte Interface) on the surface of the carbon electrode.

In addition, the aging process is a process in which the battery is left for a certain period to stabilize the SEI film. In general, the aging process is performed by exposing the secondary battery 5 that has undergone the assembly step to an environment of 50° C. to 70° C. for 18 hours to 36 hours.

As the swelling tape is secondarily expanded 310(b) by the aging process, the gap is completely filled to fix the electrode assembly, thereby effectively preventing the electrode assembly 330 from flowing.

The secondary battery may be applied to various devices. Such a device may be applied to transportation means such as an electric bicycle, an electric vehicle, and a hybrid, but is not limited thereto, and may be applied to various devices capable of using a secondary battery.

Although the preferred embodiment of the present invention has been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements by those skilled in the art using the basic concept of the present invention as defined in the following claims are also provided. is within the scope of the

Example

Example 1.

( Manufacture of swelling tape)

As a base layer, a non-stretched film having a thickness of about 30 μm made of thermoplastic polyurethane (TPU) was prepared. A 10 μm-thick adhesive layer made of an acrylate-based resin is formed on one side of the substrate layer, and a 15 μm-thick rear coating layer is formed using polybutylene terephthalate on one side of the substrate layer opposite to the side on which the adhesive layer is formed. was formed. Then, as a water-based self-healing binder, chitosan (Merck, CAS No. 9012764, product name: 419419) was dissolved in water to prepare a binder composition, and it was 7 μm thick on one surface of the back coating layer (about 23% with respect to the base layer) was coated with and dried to prepare a swelling tape including an adhesive swelling layer (see FIG. 2(c)).

( Manufacture of electrode assembly and battery)

A swelling tape was attached to the outer peripheral surface of a jelly roll-shaped electrode assembly (cross-sectional diameter: 17.2 mm) including a negative electrode (negative electrode active material: artificial graphite), a separator, and a positive electrode (positive electrode active material: LCO). The swelling tape may be attached to cover an area of about 50% of an outer peripheral surface of the electrode assembly.

Then, after inserting the assembly into a cylindrical battery case (cross-sectional diameter: 17.5 mm), electrolyte (1.0M LiPF ₆ /EC:EMC=30:70 volume ratio) is injected, and the upper part of the cylindrical battery case is sealed with a cap assembly Thus, a cylindrical secondary battery was completed.

Example 2.

In the same manner as in Example 1, except that an adhesive swelling layer was formed using sodium alginate (Merck, CAS No. 9005383) as a water-based self-healing binder when the swelling tape was manufactured. A ring tape and a cylindrical secondary battery including the same were manufactured.

Comparative Example 1.

A cylindrical secondary battery was manufactured in the same manner as in Example 1, except that a swelling tape was prepared without forming an adhesive swelling layer on the back coating layer.

Experimental example

Experimental Example 1. Impact resistance evaluation experiment

The cylindrical secondary battery prepared in Examples 1 and 2 and the cylindrical secondary battery prepared in Comparative Example 1 were charged under constant current/constant voltage conditions up to 4.2V at room temperature (25°C) at 0.33C rate and 0.05C cut off charging. , and discharge was performed at 0.33C and 2.5V. Based on the discharge capacity after each of the charge/discharge is performed once, the SOC (State Of Charge) is set to 30%, and the voltage drop appears when a discharge pulse is applied at 5A (2.5C) for 10 seconds. Direct current internal resistance was measured (measured using a PNE-0506 charger/discharger (manufacturer: PNE Solution Co., Ltd., 5V, 6A)). The measured resistance was set as the initial resistance.

Then, after randomly dropping the cylindrical secondary battery prepared in Examples 1 and 2 and the cylindrical secondary battery prepared in Comparative Example 1 from a height of 1.0 m to the concrete ground three times, the degree of external damage was measured. evaluated. The results are shown in Table 1 below.

Example 1 Example 2 Comparative Example 1 Degree of Impact Appearance Damage 4 5 3

In Table 1, the degree of the most severe appearance damage (standard) was indicated as 1, and the degree of the lowest appearance damage was indicated as 5.

Referring to Table 1, in the case of the cylindrical secondary battery including the adhesive swelling layer made of the water-based self-healing binder prepared in Examples 1 and 2 of the present invention, the impact appearance was damaged compared to the cylindrical secondary battery prepared in Comparative Example 1 It can be seen that the level is low.

Experimental Example 2. Resistance increase rate evaluation experiment

The cylindrical secondary battery prepared in Examples 1 and 2 and the cylindrical secondary battery prepared in Comparative Example 1, in which the shock resistance evaluation test of Experimental Example 1 was completed, was subjected to constant current/constant voltage up to 4.2V at room temperature (25° C.) at 3A current density. 50 mA cut-off charge under the condition, discharge under CC condition with 0.4A current density up to 2.5V, rest for 30 minutes, then 30% SOC (State Of Charge) based on Dis-charge capacity (DCH) adjusted to After that, the DC internal resistance (PNE-0506 charger/discharger (manufacturer: PNE Solution, Inc.) 5V, 6A) was measured). The resistance increase rate (%) was calculated as compared with the initial resistance (0%) measured in Experimental Example 1, and the results are shown in Table 2 below.

Example 1 Example 2 Comparative Example 1 Resistance increase rate (%) 16 10 20

Referring to Table 2, in the case of the cylindrical secondary battery including the adhesive swelling layer made of the water-based self-healing binder prepared in Examples 1 and 2 of the present invention, the resistance increase rate is lower than that of the cylindrical secondary battery of Comparative Example 1. can be checked

Experimental Example 3. Voltage increase rate evaluation experiment

Using a voltage resistance measuring instrument (Hioki RM 3548), the voltage increase rate for the cylindrical secondary batteries prepared in Examples 1 and 2 and the cylindrical secondary batteries prepared in Comparative Example 1, in which the shock resistance evaluation experiment of Experimental Example 1 was completed, was measured. and the results are shown in Table 3 below.

Example 1 Example 2 Comparative Example 1 Voltage increase rate (%) 2.0 1.8 2.4

Referring to Table 3, in the case of the cylindrical secondary battery including the adhesive swelling layer made of the water-based self-healing binder prepared in Examples 1 and 2 of the present invention, the voltage increase rate is lower than that of the cylindrical secondary battery of Comparative Example 1. can be checked

100, 330: electrode assembly;
110, 201: adhesive layer
120: swelling layer
200: swelling tape
202: base layer
203: back coating layer
220, 220(a), 220(b): an adhesive swelling layer containing a water-based self-healing binder
300: cylindrical secondary battery
310(a): swelling tape
310(b): Expanded Swelling Tape
320: cylindrical battery case (cylindrical can)

Claims (11)

It includes a base layer and an adhesive swelling layer,
The adhesive swelling layer is a swelling tape for a secondary battery comprising a water-based self-healing binder.
The method according to claim 1,
The adhesive swelling layer is a swelling tape for a secondary battery that is formed on at least one surface of both surfaces of the base layer.
The method according to claim 1,
The water-based self-healing binder is a swelling tape for a secondary battery comprising at least one compound of CMC (Ceramic Matrix Composite), arginate, and chitosan.
The method according to claim 1,
The water-based self-healing binder is a swelling tape for a secondary battery comprising at least one compound selected from the group consisting of arginate and chitosan.
The method according to claim 1,
The thickness of the adhesive swelling layer is a swelling tape for a secondary battery of 10% to 50% based on the total thickness of the base layer.
The method according to claim 1,
The swelling tape is a swelling tape for a secondary battery further comprising at least one layer of an adhesive layer and a back coating layer.
7. The method of claim 6,
The pressure-sensitive adhesive layer and the back coating layer are formed on one side and the other side of the base layer, respectively, a swelling tape for a secondary battery.
7. The method of claim 6,
The adhesive layer is a swelling tape for a secondary battery that is formed between the base layer and the adhesive swelling layer or on the adhesive swelling layer.
7. The method of claim 6,
The back coating layer is a swelling tape for a secondary battery that is formed between the base layer and the adhesive swelling layer or on the adhesive swelling layer.
The electrode assembly in which the swelling tape for a secondary battery of claim 1 is attached to an outer circumferential surface.
The electrode assembly of claim 10,
electrolyte, and
A cylindrical secondary battery comprising a cylindrical battery case for accommodating the electrode assembly and the electrolyte.

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