KR20220058421A - Electrode assembly and battery cell including the same - Google Patents

Abstract

An electrode assembly according to an embodiment of the present invention includes: a separator; a positive electrode active material layer attached to a first surface of the separator; and a negative electrode active material layer attached to a second surface of the separator, wherein the positive electrode active material layer is made of a first electrode composition in which a positive electrode active material, a conductive material and a binder are dry mixed, and the negative electrode active material layer is made of a second electrode composition in which a negative electrode active material, the conductive material, and the binder are dry mixed.

Description

Electrode assembly and battery cell including the same

The present invention relates to an electrode assembly and a battery cell including the same, and more particularly, to an electrode assembly having improved productivity and resistance reduction effects, and a battery cell including the same.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among such secondary batteries, lithium secondary batteries with high energy density and voltage, long cycle life, and low self-discharge rate has been used and is widely used.

In particular, secondary batteries are of great interest not only as mobile devices such as mobile phones, digital cameras, notebooks, and wearable devices, but also as energy sources for power devices such as electric bicycles, electric vehicles, and hybrid electric vehicles.

In addition, as interest in environmental problems grows, research on electric vehicles and hybrid electric vehicles that can replace vehicles using fossil fuels such as gasoline vehicles and diesel vehicles, which are one of the main causes of air pollution, is being conducted. there is. Although nickel-metal hydride secondary batteries are mainly used as power sources for such electric vehicles and hybrid electric vehicles, research using lithium secondary batteries with high energy density and discharge voltage is being actively conducted, and some are in the commercialization stage.

Conventional electrodes for secondary batteries are generally manufactured by a wet method. However, when the electrode is manufactured by a wet method, a heat treatment process at a high temperature is essential, and there is a risk that the metal oxide may be damaged. Accordingly, in recent years, the development of electrodes manufactured by a dry method is in progress.

1 is a view showing a conventional electrode assembly. Referring to FIG. 1 , a conventional electrode assembly includes a positive electrode 10 , a negative electrode 20 , and a separator 30 interposed between the positive electrode 10 and the negative electrode 20 . Here, in the positive electrode 10 , the positive electrode active material layer 11 is positioned on the positive electrode current collector 15 , and the negative electrode 20 has the negative active material layer 21 positioned on the negative current collector 25 .

FIG. 2 is a view illustrating a manufacturing process of an electrode included in the electrode assembly of FIG. 1 . Referring to FIG. 2 , the cathode active material layer 11 is formed in the form of a freestanding film by dry mixing an electrode composition containing polytetrafluoroethylene (PTFE, Polytetrafluoroethylene) as a binder. At this time, the positive electrode 10 is attached to the positive electrode current collector 15 by roll pressing the positive electrode active material layer 11 . This is also explained in the case of the cathode 20 .

However, when the positive electrode 10 and the negative electrode 20 are manufactured in a dry method as shown in FIG. 2 , fiberization is prevented by shear force, not by a chemical bonding method by high temperature and pressure due to the characteristics of polytetrafluoroethylene (PTFE, Polytetrafluoroethylene). The electrode composition is prepared by a bonding method that wraps the active material through the In particular, in order to attach the electrode composition to the current collectors 15 and 25 in the form of a free-standing film, a separate binder needs to be additionally applied or coated between the free-standing film and the current collector.

For example, conventionally, by adding polyvinylidene fluoride (PVDF, Polyinylidene fluoride), an acrylic binder, etc. to the electrode composition in addition to polytetrafluoroethylene (PTFE, Polytetrafluoroethylene), the adhesion of the freestanding film is increased, or the current collector The adhesive force of the current collectors 15 and 25 was increased by coating the adhesive binder on the (15, 25) in advance. At this time, the adhesive binder was coated on the current collectors 15 and 25 by using a slurry coating method or a pattern coating method such as general bar coating and gravure coating.

However, the adhesive layer formed between the free-standing film and the current collectors 15 and 25 blocks contact between the free-standing film and the current collectors 15 and 25, thereby limiting electron movement. Accordingly, in the prior art, a conductive material having conductivity was mixed with the adhesive layer to solve the above problem. However, in the conventional method, since the binder is positioned between the freestanding film and the current collectors 15 and 25 , the binder acts as a resistor in the high-rate region, thereby reducing the discharge capacity.

3 is an exploded view of the electrode assembly of FIG. 1 . 1 to 3 , the conventional electrode assembly has a structure in which a separator 30 is interposed between the anode 10 and the cathode 20 respectively manufactured as shown in FIG. 2 . Accordingly, in the conventional electrode assembly, the positive electrode 10 and the negative electrode 20 are limited in the form of a film to secure a predetermined strength, and the productivity is lowered as the positive electrode 10 and the negative electrode 20 are separately manufactured. there is

Accordingly, unlike the related art, there is a growing need for developing an electrode assembly with improved resistance reduction effect and improved productivity by minimizing the binder content while including the electrode manufactured by the dry method.

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode assembly having improved productivity and resistance reduction effects, and a battery cell including the same.

The problem to be solved by the present invention is not limited to the above-mentioned problems, and the problems not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention belongs from the present specification and the accompanying drawings. .

An electrode assembly according to an embodiment of the present invention includes a separator; a positive active material layer attached to the first surface of the separator; and a negative active material layer attached to the second surface of the separator, wherein the positive active material layer is formed of a first electrode composition in which a positive electrode active material, a conductive material, and a binder are dry mixed, and the negative electrode active material layer is a negative electrode It is formed of a second electrode composition in which an active material, a conductive material, and a binder are dry mixed.

The positive electrode active material layer may have a positive electrode current collector stacked on a surface opposite to a surface in contact with the separator, and a negative electrode current collector may be stacked on a surface opposite to the negative active material layer in contact with the separator.

At least one of the positive electrode current collector and the negative electrode current collector may be formed of a flat sheet.

At least one of the positive electrode current collector and the negative electrode current collector may be formed of at least two or more linear sheets, and the linear sheets may be spaced apart from each other.

The linear sheets may have the same pattern as each other.

At least one of the positive electrode current collector and the negative electrode current collector may be formed of a fibrous sheet having a random arrangement.

The first electrode composition and the second electrode composition each include a binder, and the content of the binder included in the first electrode composition is 1 wt% or more and 5 wt% or less based on the total weight of the first electrode composition and the content of the binder included in the second electrode composition may be 1 wt% or more and 5 wt% or less based on the total weight of the second electrode composition.

The binder may include polytetrafluoroethylene (PTFE, polytetrafluoroethylene).

The content of the positive active material included in the first electrode composition may be 90% by weight or more and 98% by weight or less based on the total weight of the first electrode composition.

The positive active material is lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide, lithium copper oxide (Li ₂ CuO ₂ ), vanadium oxide, Ni site-type lithium nickel oxide, lithium manganese composite oxide, spinel Lithium manganese composite oxide of the structure, LiMn ₂ O ₄ in which a part of formula Li is substituted with alkaline earth metal ions, a disulfide compound, Fe ₂ (MoO ₄ ) _3, Lithium Manganese Oxide (LMO, Lithium Manganese Oxide) can

The content of the negative active material included in the second electrode composition may be 90% by weight or more and 98% by weight or less based on the total weight of the second electrode composition.

The negative active material may include at least one of lithium metal, lithium alloy, petroleum coke, activated carbon, graphite, silicon, tin, and metal oxide.

Each of the positive active material layer and the negative active material layer may be manufactured as a freestanding film.

An adhesive layer is formed between the separator and the positive active material layer, and between the separator and the negative active material layer, and the adhesive layer may have a porous structure.

The battery cell according to another embodiment of the present invention may include the above-described electrode assembly.

In the battery cell, at least two of the electrode assemblies are stacked, and the at least two electrode assemblies may be disposed such that the positive active material layers included in each electrode assembly face each other, or the negative active material layers face each other. there is.

In the at least two electrode assemblies, a positive electrode current collector may be stacked between each of the positive electrode active material layers, and a negative electrode current collector may be stacked between each of the negative electrode active material layers.

An electrode assembly manufacturing method according to another embodiment of the present invention includes: manufacturing a positive electrode active material layer formed of a first electrode composition in which a positive electrode active material, a conductive material, and a binder are dryly mixed; preparing an anode active material layer formed of a second electrode composition in which an anode active material, a conductive material, and a binder are dry mixed; and attaching the positive active material layer to the first surface of the separator, and attaching the negative active material layer to the second surface of the separator.

The positive electrode active material layer and the negative electrode active material layer may be made of a freestanding film.

The method may further include laminating a positive electrode current collector on a surface of the positive active material layer opposite to the surface in contact with the separator, and laminating a negative current collector on a surface opposite to the surface in contact with the separator in the negative active material layer. .

According to an embodiment of the present invention, by providing an electrode assembly in which a freestanding film manufactured by a dry method is attached to a separator and a battery cell including the same, productivity and resistance reduction effect can be improved.

Effects of the present invention are not limited to the above-described effects, and effects not mentioned will be clearly understood by those of ordinary skill in the art to which the present invention pertains from the present specification and accompanying drawings.

1 is a view showing a conventional electrode assembly.
FIG. 2 is a view illustrating a manufacturing process of an electrode included in the electrode assembly of FIG. 1 .
3 is an exploded view of the electrode assembly of FIG. 1 .
4 is a view showing an electrode assembly according to an embodiment of the present invention.
5 is a view illustrating a current collector included in the electrode assembly of FIG. 4 .
6 is a flowchart illustrating a process of manufacturing the electrode assembly of FIG. 4 .
7 is a view illustrating a manufacturing step of the electrode assembly of FIG. 6 .
8 is an exploded view of the electrode assembly manufactured in the electrode assembly manufacturing step of FIG. 6 .

Hereinafter, 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. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein.

Hereinafter, an electrode assembly according to an embodiment of the present invention will be described.

4 is a view showing an electrode assembly according to an embodiment of the present invention.

Referring to FIG. 4 , the electrode assembly according to an embodiment of the present invention includes a positive active material layer 110 , a negative active material layer 210 , and a separator 300 . In the separator 300 , the positive active material layer 110 is attached to the first surface of the separator 300 , and the negative active material layer 210 is attached to the second surface of the separator 300 .

For example, in a state in which the positive active material layer 110 is laminated on the first surface of the separator 300 and the negative active material layer 210 is laminated on the second surface of the separator 300, the positive active material layer 110, The anode active material layer 210 and the separator 300 may be attached by roll pressing.

Here, the separator 300 can be used without any particular limitation as long as it is usually used as a separator in a lithium secondary battery. In particular, it is preferable to have low resistance to ion movement of the electrolyte and excellent electrolyte moisture content while having surface adhesion. For example, the separator 300 is a porous polymer film, and is made of a polyolefin (PO)-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an itelin/hexene copolymer, and an ethylene/methacrylate copolymer. It may be a prepared porous polymer film. Alternatively, a Safety Reinforced Separator (SRS) may be used. Alternatively, as a conventional porous nonwoven fabric, a nonwoven fabric made of glass fiber having a high melting point, polyethylene terephthalate fiber, or the like may be used.

Accordingly, the separator 300 separates the cathode active material layer 110 and the anode active material layer 210 to serve as a lithium ion passage, while the cathode active material layer 110 and the anode active material layer 210 attached to each side. ) can serve as a support for In addition, through the surface adhesive force of the separator 300, as the content of the binder included in the electrode assembly is minimized, the effect of reducing the resistance may be improved.

In the electrode assembly according to another embodiment of the present invention, the separator 300 may include an adhesive layer (not shown) between the separator 300 and the positive active material layer 110 , and the separator 300 and the negative electrode. An adhesive layer (not shown) may be included between the active material layers 210 .

The adhesive layer (not shown) is attached to the separator 300 , and may have a porous structure that does not impede the movement of lithium ions moving through the separator 300 . For example, the adhesive layer (not shown) may be formed on the separation film 300 by a humidified phase separation method. In addition, the adhesive layer (not shown) can be used without limitation as long as it is a coating technique that does not block the pores formed in the separator 300 , and methods such as binder pattern coating, coating of a mixed composition of an inorganic material and a binder, and the like can be applied.

In addition, the adhesive layer may be formed of a coating slurry including an adhesive binder such as polyvinylidene fluoride (PVDF) or an acrylic binder. However, the material constituting the adhesive layer is not limited thereto, and any material having adhesive properties while being coated on the surface of the separator 300 may be used without limitation.

Accordingly, the separator 300 may have improved adhesion to each of the positive active material layer 110 and the negative active material layer 210 . In addition, the separator 300 is not limited in its role as a passage for lithium ions even if the adhesive layer is formed. In addition, through the surface adhesive force of the separator 300 , the content of the binder included in the adhesive layer formed on the separator 300 may be reduced compared to the prior art, and thus the effect of reducing resistance may be improved. In addition, the increase in resistance according to the adhesive layer may not be large, and the discharge capacity may also be improved in a high rate region.

In addition, the adhesive force between the separator 300 and the positive active material layer 110 or the negative active material layer 210 may be 13 gf/15 mm or more and 100 gf/15 mm or less. More specifically, the adhesive force between the separator 300 and the positive active material layer 110 or the negative active material layer 210 may be 15 gf/15 mm or more and 95 gf/15 mm or less. For example, the adhesive force between the separator 300 and the positive active material layer 110 or the negative active material layer 210 may be 20 gf/15 mm or more and 90 gf/15 mm or less.

Accordingly, in the electrode assembly of this embodiment, the adhesive force between the separator 300 and the positive electrode active material layer 110 or the negative active material layer 210 may have an adhesive strength in the above-described range, and the separator 300 and the positive electrode active material layer (110) or the anode active material layer 210 may be stably fixed.

On the other hand, when the adhesive force between the separator 300 and the positive electrode active material layer 110 or the negative electrode active material layer 210 is too small outside the above-mentioned range, the separator 300 and the positive electrode active material layer 110 or the negative active material layer ( 210) may not be stably fixed. In addition, when the adhesive force between the separator 300 and the positive electrode active material layer 110 or the negative electrode active material layer 210 is too large outside the above-described range, there is a problem in that the manufacturing cost increases or the implementation is difficult in terms of the manufacturing process.

In addition, the positive electrode active material layer 110 is formed of a first electrode composition in which the positive electrode active material is dry mixed. The anode active material layer 210 is formed of a second electrode composition in which the anode active material is dry mixed. For example, each of the positive active material layer 110 and the negative active material layer 210 may be made of a freestanding film. Accordingly, before the positive active material layer 110 and the negative active material layer 210 are manufactured into an electrode assembly, each freestanding film may be stored in a roll form, and thus productivity may be improved.

The positive active material included in the first electrode composition may include, for example, lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ); lithium manganese oxide; lithium copper oxide (Li ₂ CuO ₂ ); vanadium oxide; Ni site-type lithium nickel oxide; lithium manganese composite oxide; Lithium-manganese composite oxide of spinel structure; LiMn ₂ O ₄ in which a part of the formula Li is substituted with an alkaline earth metal ion; disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like. For example, the positive active material may include lithium manganese oxide (LMO).

Here, the positive active material may be included in an amount of 88 wt% to 99 wt% based on the total weight of the first electrode composition. More preferably, the positive active material may be included in an amount of 89 wt% to 98.5 wt% based on the total weight of the first electrode composition. For example, the positive active material may be included in an amount of 90 wt% to 98 wt% based on the total weight of the first electrode composition.

The negative active material included in the second electrode composition may use a conventional negative electrode active material for a lithium secondary battery in the art, for example, lithium metal, lithium alloy, petroleum coke, activated carbon (activated carbon), graphite (graphite) , silicon, tin, metal oxides, or other carbons may be used.

Here, the negative active material may be included in an amount of 88 wt% to 99 wt% based on the total weight of the second electrode composition. More preferably, the negative active material may be included in an amount of 89 wt% to 98.5 wt% based on the total weight of the second electrode composition. For example, the negative active material may be included in an amount of 90 wt% to 98 wt% based on the total weight of the second electrode composition.

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

For example, each of the binders may include polytetrafluoroethylene (PTFE). Here, polytetrafluoroethylene (PTFE) has a characteristic that the fibers are pulled out from the particles as a shear force is applied. That is, in one embodiment of the present invention, the first electrode composition and the second electrode composition each include polytetrafluoroethylene (PTFE) as a binder, but the first electrode composition and the second electrode composition are strong It can be mixed by a physical mixing method according to the fiberization of polytetrafluoroethylene (PTFE) by applying shear force.

Accordingly, in an embodiment of the present invention, the first electrode composition and the second electrode composition may be dry mixed without a separate solvent or additive, so that bridging between the active material particles or between the active material particles and the current collector While very effective for bridging, damage to the active material generated during the heat treatment at high temperature according to the conventional mixing method can be prevented.

In addition, the content of the binder included in the first electrode composition is 1% by weight or more and 5% by weight or less based on the total weight of the first electrode composition, and the content of the binder included in the second electrode composition is It may be 1 wt% or more and 5 wt% or less based on the total weight of the second electrode composition. More preferably, the content of the binder included in the first electrode composition is 2% by weight or more and 4% by weight or less based on the total weight of the first electrode composition, and the amount of the binder included in the second electrode composition is The content may be 2 wt% or more and 4 wt% or less based on the total weight of the second electrode composition.

Accordingly, the first electrode composition and the second electrode composition may have sufficient tensile strength and discharge capacity to form the positive electrode active material layer 110 and the negative electrode active material layer 210 . On the other hand, when the content of the binder is less than 1% by weight, the tensile strength of the positive active material layer 110 and the negative active material layer 210 may be reduced. In addition, when the content of the binder is more than 5% by weight, the binder acts as a resistance in the positive active material layer 110 and the negative active material layer 210 , and thus the discharge capacity may be reduced.

In addition, the first electrode composition and the second electrode composition may each include a conductive material. The conductive material is used to impart conductivity to the electrode, and in the configured battery, it can be used without any particular limitation as long as it does not cause chemical change and has electronic conductivity. Specific examples include carbon-based materials such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, summer black, carbon graphene, and carbon fiber; graphite such as natural graphite and artificial graphite; metal powders or metal fibers, such as copper, nickel, aluminum, and silver; conductive whiskeys such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or a conductive polymer such as a polyphenylene derivative, and the like, and one or a mixture of two or more thereof may be used. Here, the conductive material may be included in an amount of 1 wt% to 10 wt% based on the total weight of the electrode.

Hereinafter, the current collectors 150 and 250 included in the electrode assembly according to the present embodiment will be described in detail.

5 is a view illustrating a current collector included in the electrode assembly of FIG. 4 .

4 and 5 , in the electrode assembly according to an embodiment of the present invention, the positive electrode current collector 150 is stacked on the surface of the positive electrode active material layer 110 in contact with the separator 300 and the opposite surface. . In addition, in the negative active material layer 210 , the negative electrode current collector 250 is stacked on the surface opposite to the surface in contact with the separator 300 .

Accordingly, the electrode assembly according to the present embodiment is laminated without a separate adhesive layer between the positive electrode active material layer 110 and the positive electrode current collector 150 , so that between the positive electrode active material layer 100 and the positive electrode current collector 150 . The contact area may be increased, and the discharge capacity may also be improved because electron movement between the positive electrode active material layer 100 and the positive electrode current collector 150 is not limited. This may be equally described for the anode active material layer 210 and the anode current collector 250 .

Here, the positive electrode current collector 150 and the negative electrode current collector 250 are not particularly limited as long as they have high conductivity without causing chemical change in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium. , calcined carbon, one in which the surface of copper or stainless steel is surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. may be used.

Also, there may be little adhesion between the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative electrode active material layer 210 . If there is an adhesive force between the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative electrode active material layer 210, the adhesive force is the current collector 150, 250 and the active material layer 210, 250) may be self-adhesive.

In this case, the adhesive force between the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative electrode active material layer 210 may be 0 gf/15 mm or more and 5 gf/15 mm or less. More specifically, the adhesive force between the separator 300 and the positive active material layer 110 or the negative active material layer 210 may be 0.05 gf/15 mm or more and 4.5 gf/15 mm or less. For example, the adhesive force between the separator 300 and the positive active material layer 110 or the negative active material layer 210 may be 0.1 gf/15 mm or more and 4 gf/15 mm or less.

Accordingly, in the electrode assembly of the present embodiment, the adhesive force between the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative electrode active material layer 210 may have an adhesive strength within the above-described range. , there may be little adhesion between the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative electrode active material layer 210 . That is, since a separate adhesive layer is not formed between the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative electrode active material layer 210 , the electron movement obstruction is also reduced, thereby improving the discharge capacity. can be

On the other hand, when the adhesive force between the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative electrode active material layer 210 is too large outside the above-described range, the positive electrode current collector 150 and It can be seen that a separate adhesive layer is formed between the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative electrode active material layer 210 . In this case, the adhesive layer located between the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode current collector 250 and the negative active material layer 210 is the positive electrode current collector 150 and the positive electrode active material layer 110 or the negative electrode. Electron movement between the current collector 250 and the anode active material layer 210 may be prevented, and discharge capacity in a high rate region may also be reduced.

In addition, referring to FIGS. 4 and 5 , in the electrode assembly according to the present embodiment, the positive active material layer 110 and the negative active material layer 210 are attached to the separator 300 , so that the positive electrode current collector 150 and The negative electrode current collector 250 is not limited to the conventionally used film form, and may be used in various forms.

Referring to FIG. 5A , at least one of the positive electrode current collector 150 and the negative electrode current collector 250 may be formed of a flat sheet. For example, when the positive electrode current collector 150 is formed of a flat sheet, the positive electrode current collector 150 may have the same size or smaller size than that of one surface of the positive electrode active material layer 110 . In addition, the positive electrode current collector 150 does not need to serve as a support for the positive electrode active material layer 110 , unlike the conventional one, and may have a smaller thickness than the conventional one. This may be equally described for the negative electrode current collector 250 .

5(b) and (c), at least one of the positive electrode current collector 150 and the negative electrode current collector 250 is formed of at least two or more linear sheets, and the linear sheets may be spaced apart from each other. there is. Here, the linear sheet may be formed in various forms such as a fiber type, a rod type, and a thin plate type. Also, the linear sheets may have the same pattern as each other. As an example, the pattern may be a curved, straight, dotted, etc. pattern.

Referring to FIG. 5D , at least one of the positive electrode current collector 150 and the negative electrode current collector 250 may be formed of a fibrous sheet having a random arrangement.

Accordingly, the electrode assembly according to the present embodiment may include various types of current collectors 150 and 250 , thereby reducing the total area of the current collectors 150 and 250 and sufficiently serving as an electron transfer chamber. In addition, when assembling the battery cell, the overall weight is reduced and the manufacturing form is easy, so that productivity can be improved. In addition, more active material layers 110 and 210 may be included than in the related art, and discharge capacity may be further increased.

In addition, in the electrode assembly according to the present embodiment, a notching process in which an electrode tab is formed at one end of the current collectors 150 and 250 may proceed together when the current collectors 150 and 250 of the above-described type are manufactured, so that productivity This can be further improved.

Hereinafter, a method of manufacturing an electrode assembly according to another embodiment of the present invention will be described in detail.

6 is a flowchart illustrating a process of manufacturing the electrode assembly of FIG. 4 . 7 is a view illustrating a manufacturing step of the electrode assembly of FIG. 6 . 8 is an exploded view of the electrode assembly manufactured in the electrode assembly manufacturing step of FIG. 6 .

6, the electrode assembly manufacturing method according to this embodiment includes a pre-mixing step of dry mixing an active material, a conductive material, and a binder (S10), a mixing step of preparing an electrode composition by applying a high shear force (S20), Preparing a free-standing film using the electrode composition (S30), and performing a lamination process after attaching the free-standing film on a separator, and laminating a current collector on the free-standing film to prepare an electrode assembly (S50).

More specifically, referring to FIGS. 6 and 7 , in the electrode assembly manufacturing step S50 , the positive active material layer 110 prepared in the freestanding step S30 is attached to one surface of the separator 300 , and the freestanding step The anode active material layer 210 prepared in ( S30 ) is attached to the other surface of the separator 300 . For example, in a state in which the positive electrode active material layer 110 and the negative electrode active material layer 210 are laminated on the upper and lower surfaces of the separator 300, respectively, the positive electrode active material layer 110-separator 300-negative electrode active material layer is adhered by a flat press. An electrode assembly having a 210 structure may be formed.

In addition, referring to FIGS. 6 to 8 , the electrode assembly manufacturing step S50 includes a positive electrode current collector 150 and A negative electrode current collector 250 may be additionally stacked. For example, at least two electrode assemblies are stacked, and the at least two electrode assemblies have a positive electrode active material layer 110 included in each electrode assembly facing each other or a negative electrode active material layer 210 facing each other. can be placed. In addition, in at least two of the electrode assemblies, a positive electrode current collector 150 may be stacked between each positive electrode active material layer 110 , and a negative electrode current collector 250 may be stacked between each negative electrode active material layer 210 . .

Accordingly, the electrode assembly manufacturing method according to the present embodiment is a conventional process in which an electrode assembly having a structure of the positive electrode active material layer 110 - the separator 300 - the negative electrode active material layer 210 is manufactured, and the positive electrode and the negative electrode are separately manufactured. In comparison, the manufacturing process can be simplified. In addition, the electrode assembly having the structure of the positive electrode active material layer 110-separator 300-negative electrode active material layer 210 has a positive electrode active material layer 110 and a positive electrode current collector 150 or a negative electrode active material layer 210 and a negative electrode current collector ( 250), since a separate adhesive layer is not included, the electron movement is not limited, and thus the discharge capacity can also be improved.

The battery cell according to another embodiment of the present invention may include the above-described electrode assembly. In addition, the battery cell according to another embodiment of the present invention may include the above-described electrode assembly and the electrolyte.

Examples of the electrolyte used in the present invention include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., which can be used in the manufacture of lithium secondary batteries. not.

Specifically, the electrolyte may include an organic solvent and a lithium salt. The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery.

In addition to the above components, the electrolyte includes, for example, haloalkylene carbonate-based compounds such as difluoroethylene carbonate, pyridine, triethyl, for the purpose of improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity. Phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazoli One or more additives such as din, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol or aluminum trichloride may be further included. In this case, the additive may be included in an amount of 0.1 wt% to 5 wt% based on the total weight of the electrolyte.

Hereinafter, the contents of the present invention will be described by way of examples, but the following examples are for illustrative purposes only, and the scope of the present invention is not limited thereto.

<Example>

In the embodiment, a pre-mixing step of preparing a mixture in which a positive active material, a conductive material, and a binder is dry mixed using a blender equipment of Waring is performed. Here, the positive active material is 94% by weight of lithium manganese oxide (LMO, Lithium Manganese Oxide), and the conductive material is 3% by weight of Super C65. In addition, the binder contains 3% by weight of polytetrafluoroethylene (PTFE). At this time, the pre-mixing step (S10) was performed at room temperature at 5000 rpm for 1 minute. Thereafter, a mixing step (S20) of preparing a first electrode composition by applying a shear force to the mixture prepared in the pre-mixing step (S10) is performed using Irie Shokai's PBV-0.1L equipment. At this time, the mixing step (S20) was performed for 5 minutes at 30 rpm at room temperature. Then, using Inoue's Two roll mill MR-3 equipment, the positive active material layer 110 in the form of a freestanding film was prepared using the first electrode composition prepared in the mixing step (S20). In the case of the anode active material layer 210 , all were manufactured in the same manner except that an anode active material, which is graphite, is used to replace the cathode active material.

Thereafter, PVDF-HFP (Mw. 500,000) resin was added to acetone to prepare a polymer solution (solid content of 5 wt% concentration). Here, Al2O3 (Japan Light Metals, LS235) was added and dispersed in a ball mill method to prepare a slurry for a porous coating layer. The prepared slurry for the porous coating layer was coated on the separator 300 made of polyolefin (PO) having a thickness of 15 μm by a dip coating method. Here, the thickness of the adhesive layer coated with the slurry for the porous coating layer is 2 μm. At this time, the temperature was carried out under a level of 23 degrees Celsius, relative humidity (RH) 40%.

Thereafter, the positive active material layer 110 and the negative active material layer 210 are respectively stacked on the separator 300 coated with the slurry for the porous coating layer, and then roll pressing is performed, the positive active material layer 110-separator 300 - An electrode assembly having a structure of the anode active material layer 210 was manufactured.

Then, the negative electrode comprising at least two or more of the electrode assemblies, wherein the positive electrode current collector 150, which is an aluminum foil of 20 μm, is laminated on the positive active material layer 110, and is a copper foil of 20 μm on the negative electrode active material layer 210 After the current collector 250 was laminated, it was packaged in a pouch together with an electrolyte to prepare a battery cell. Here, as the electrolyte, a 1.0M LiPF ₆ solution was used as a mixed solvent of ethylene carbonate (EC)/ethylmethyl carbonate (EMC) (20/80; volume ratio).

<Comparative Example 1>

In the above embodiment, Comparative Example 1 does not include a separate adhesive layer in the separator 30 , and is an adhesive slurry in which PVDF and carbon are mixed between the positive electrode active material layer 11 and the positive electrode current collector 15 . includes an adhesive layer coated to a thickness of 0.5 μm, and the positive electrode active material layer 11 and the positive electrode current collector 15 were roll-pressed to prepare the positive electrode 10 . In addition, between the negative electrode active material layer 21 and the negative electrode current collector 25, an adhesive slurry in which PVDF and carbon are mixed includes an adhesive layer coated to a thickness of 0.5 μm, and the negative electrode active material layer 21 The negative electrode current collector 25 and the negative electrode current collector 25 were roll-pressed to prepare the negative electrode 10 . In addition, by stacking the separator 30 between the positive electrode 10 and the negative electrode 20, the electrode assembly of the positive electrode 10-separator 30-negative electrode 20 structure is manufactured and packaged in a pouch together with the electrolyte. Except that the battery cell was manufactured, it was manufactured in the same manner as in Example.

<Comparative Example 2>

In the above embodiment, in Comparative Example 2, the separator 30 does not include a separate adhesive layer, and PVDF and carbon are mixed between the positive electrode active material layer 11 and the positive electrode current collector 15 for an adhesion slurry includes an adhesive layer coated to a thickness of 1.5 μm, and the positive electrode active material layer 11 and the positive electrode current collector 15 were roll-pressed to prepare the positive electrode 10 . In addition, between the negative electrode active material layer 21 and the negative electrode current collector 25, an adhesive slurry in which PVDF and carbon are mixed includes an adhesive layer coated to a thickness of 1.5 μm, and the negative electrode active material layer 21 The negative electrode current collector 25 and the negative electrode current collector 25 were roll-pressed to prepare the negative electrode 10 . In addition, by stacking the separator 30 between the positive electrode 10 and the negative electrode 20, the electrode assembly of the positive electrode 10-separator 30-negative electrode 20 structure is manufactured and packaged in a pouch together with the electrolyte. Except that the battery cell was manufactured, it was manufactured in the same manner as in Example.

<Experimental Example 1 (Adhesive force measurement)>

The adhesive force between the positive active material layers 11 and 110 and the negative active materials 21 and 210 in the form of free-standing films prepared in Examples, Comparative Examples 1, and 2, respectively, and other substrates was measured. At this time, the adhesive force was sampled with a width of 15 mm, and then, using Instron's UTM equipment, the adhesive force was measured through peel strength at an angle of 90 degrees at a speed of 300 mm/min. Here, for the adhesive force, the adhesive force between the current collector and the active material layer and the adhesive force between the separator and the active material layer were measured, respectively, and the results are shown in Table 1.

Example Comparative Example 1 Comparative Example 2 Adhesion between the current collector and the active material layer (gf/15mm) 0.2 5.6 12.5 Adhesion between the separator and the active material layer (gf/15mm) 74.6 - -

Referring to Table 1, unlike Comparative Examples 1 and 2, when the adhesive layer is formed between the active material layer and the separator as in Examples, it can be seen that the adhesive force between the active material layer and the separator is very excellent.

On the other hand, when the adhesive layer is formed between the current collector and the active material layer as in Comparative Examples 1 and 2, the adhesive force between the current collector and the active material layer is superior to that of the Example, but between the separator and the active material layer of the Example. It can be seen that the adhesive strength is very low. In addition, in Comparative Examples 1 and 2, it can be seen that, unlike in Examples, there is no adhesive force between the separator and the active material layer.

Accordingly, the positive active material layer 110 and the negative active material layer 210 according to the present embodiment, even if manufactured in the form of a free-standing film in the same manner as in the comparative example, between the active material layers 110 and 210 and the separator 300 Adhesion is very good, and as the active material layers 110 and 210 and the separator 300 are stably fixed to each other, the stability of the battery cell is improved in the charging/discharging process of the battery cell, and the lifespan can also be extended.

<Experimental Example 2 (discharge capacity measurement)>

After charging and discharging the battery cells prepared in Examples and Comparative Examples under 0.1C/0.1C, 1C/1C, and 2C/2C conditions in a voltage range of 3.0 to 4.3V, the discharge capacity value of the first cycle was calculated, and the result was Table 2 shows.

Example Comparative Example 1 Comparative Example 2 0.1C initial discharge capacity (mAh/g) 4.97 4.97 4.99 1C discharge capacity (mAh/g) 4.56 4.28 4.17 2C discharge capacity (mAh/g) 3.72 2.99 2.21

Referring to Table 2, it can be seen that, unlike Comparative Examples 1 and 2, the Example exhibits excellent discharge capacity overall. In particular, unlike Comparative Examples 1 and 2, it can be confirmed that the discharge capacity is improved in the Example in the high-rate region. In addition, in Comparative Examples 1 and 2, the adhesive layer located between the current collectors 15 and 25 and the active material layers 11 and 21 includes a mixture of a binder and a conductive material, but the binder included in the adhesive layer is the current collector ( 15 and 25) and the active material layers 11 and 21, it can be seen that they are inferior in the high-rate region in that they interfere with the movement of electrons. In particular, when comparing Comparative Example 1 and Comparative Example 2, the thicker the adhesive layer positioned between the current collectors 15 and 25 and the active material layers 11 and 21, the greater the degree of inferiority.

Contrary to this, in the case of the embodiment, a separate adhesive layer is not formed between the current collectors 150 and 250 and the active material layers 110 and 210, so they are in complete contact with each other, so the adhesive layer is the current collectors 150 and 250 and the active material layer. It can be seen that the discharging capacity is superior to that of Comparative Example even in a high-rate region without interfering with electron movement between (110, 210).

Accordingly, in the case of including the electrode assembly having the structure of the positive electrode active material layer 110 - the separator 300 - the negative electrode active material layer 210 as in the embodiment, the content of the binder included in the electrode assembly is minimized, so that the resistance improvement effect is improved. It can be confirmed that the overall discharge capacity is excellent as the electron movement interference by the adhesive layer is also reduced.

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 presented. It belongs to the scope of the right of the invention.

Claims (20)

separator;
a positive active material layer attached to the first surface of the separator; and
and an anode active material layer attached to the second surface of the separator,
The positive electrode active material layer is formed of a first electrode composition in which a positive electrode active material, a binder, and a conductive material are dry mixed,
The anode active material layer is an electrode assembly formed of a second electrode composition in which an anode active material, a binder, and a conductive material are dry mixed. In claim 1,
In the positive active material layer, a positive electrode current collector is laminated on a surface opposite to a surface in contact with the separator,
The negative electrode active material layer is an electrode assembly in which an anode current collector is laminated on a surface opposite to a surface in contact with the separator. In claim 2,
At least one of the positive electrode current collector and the negative electrode current collector is formed of a flat sheet. In claim 2,
At least one of the positive electrode current collector and the negative electrode current collector is formed of at least two or more linear sheets,
The linear sheet is an electrode assembly spaced apart from each other. In claim 4,
The linear sheet electrode assembly having the same pattern as each other. In claim 2,
At least one of the positive electrode current collector and the negative electrode current collector is an electrode assembly formed of a fibrous sheet having a random arrangement. In claim 1,
The content of the binder included in the first electrode composition is 1 wt% or more and 5 wt% or less, based on the total weight of the first electrode composition,
The content of the binder included in the second electrode composition is 1 wt% or more and 5 wt% or less based on the total weight of the second electrode composition. In claim 7,
The binder is an electrode assembly comprising polytetrafluoroethylene (PTFE, Polytetrafluoroethylene). In claim 1,
The content of the positive electrode active material included in the first electrode composition is 90% by weight or more and 98% by weight or less based on the total weight of the first electrode composition. In claim 9,
The positive active material is lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), lithium manganese oxide, lithium copper oxide (Li ₂ CuO ₂ ), vanadium oxide, Ni site-type lithium nickel oxide, lithium manganese composite oxide, spinel Lithium manganese complex oxide of the structure, LiMn ₂ O ₄ in which a part of the formula Li is substituted with alkaline earth metal ions, a disulfide compound, Fe ₂ (MoO ₄ ) _3, Lithium Manganese Oxide (LMO, Lithium Manganese Oxide) containing at least one electrode assembly. In claim 1,
The content of the negative active material included in the second electrode composition is 90% by weight or more and 98% by weight or less based on the total weight of the second electrode composition. In claim 11,
The negative active material is an electrode assembly including at least one of lithium metal, lithium alloy, petroleum coke, activated carbon, graphite, silicon, tin, and a metal oxide. In claim 1,
The positive electrode active material layer and the negative electrode active material layer are each made of a freestanding film electrode assembly. In claim 1,
An adhesive layer is formed between the separator and the cathode active material layer, and between the separator and the anode active material layer,
The adhesive layer has a porous structure, the electrode assembly. A battery cell comprising the electrode assembly of claim 1 . In claim 15,
In the battery cell, at least two of the electrode assemblies are stacked,
In the at least two electrode assemblies, the positive electrode active material layer included in each electrode assembly faces each other or the negative electrode active material layer is disposed to face each other. 17. In claim 16,
At least two of the electrode assemblies have a positive electrode current collector stacked between each of the positive electrode active material layers,
A battery cell in which an anode current collector is stacked between each of the anode active material layers. manufacturing a positive electrode active material layer formed of a first electrode composition in which a positive electrode active material, a conductive material, and a binder are dryly mixed;
preparing an anode active material layer formed of a second electrode composition in which an anode active material, a conductive material, and a binder are dry mixed; and
and attaching the positive active material layer to a first surface of the separator, and attaching the negative active material layer to a second surface of the separator. In claim 18,
The cathode active material layer and the anode active material layer are manufactured as a freestanding film, the electrode assembly manufacturing method. In claim 18,
A positive electrode current collector is laminated on a surface opposite to the surface in contact with the separator in the positive electrode active material layer, and the negative electrode current collector is laminated on a surface opposite to the surface in contact with the separator in the negative active material layer, the electrode comprising the steps of: A method of manufacturing an assembly.

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