KR101584752B1 - Electrochemical device - Google Patents

Abstract

A cathode having a current collector, a coating region of the cathode active material formed on at least one surface of the current collector, and an uncoated region on which the cathode active material is not coated; Anode; A separator interposed between the cathode and the anode; And a cathode tape film attached over the boundary between the application region and the non-application region of the cathode active material, wherein the cathode tape film has an activation portion capable of moving lithium ions and an inactive portion capable of preventing lithium ions from moving, There is provided an electrochemical device in which an activating part is attached to a coating area of a cathode active material and the deactivating part is attached to an uncoated area of the cathode active material.

Description

[0001] Electrochemical device [0002]

The present invention relates to an electrochemical device such as a lithium secondary battery, and more particularly, to an electrochemical device having a cathode tape film attached over a boundary between a coated region of a cathode active material on a collector and an uncoated region.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs and even electric vehicles are expanding, efforts for research and development of electrochemical devices are becoming more and more specified. Electrochemical devices have attracted the greatest attention in this respect. Among them, the development of rechargeable secondary batteries has become a focus of attention. In recent years, in order to improve capacity density and specific energy, And research and development on the design of the battery.

Among the currently applied electrochemical devices, the lithium secondary battery developed in the early 1990s has higher operating voltage and higher energy density than conventional batteries such as Ni-MH, Ni-Cd and sulfuric acid-lead batteries using an aqueous electrolyte solution It is attracting attention as an advantage. However, such a lithium ion battery has safety problems such as ignition and explosion when using an organic electrolytic solution, and it is disadvantageous in that it is difficult to manufacture. Recently, the lithium ion polymer battery is considered to be one of the next generation batteries by improving the weak point of the lithium ion battery. However, since the capacity of the battery is still relatively low as compared with the lithium ion battery and the discharge capacity at low temperature is insufficient, Is urgently required.

Such a lithium secondary battery mainly uses a lithium-based oxide as a cathode active material and a carbonaceous material as an anode active material. Generally, a battery using a liquid electrolyte is referred to as a lithium ion battery, and a battery using a polymer electrolyte is referred to as a lithium polymer battery, which is classified as a liquid electrolyte cell and a polymer electrolyte cell, depending on the type of the electrolyte. In addition, the lithium secondary battery is manufactured in various shapes. Typical shapes include a cylindrical shape, a square shape, and a pouch shape.

Typically, the lithium secondary battery includes a cathode electrode plate coated with a cathode active material, an anode electrode plate coated with an anode active material, and a cathode disposed between the cathode electrode plate and the anode electrode plate to prevent short- A case for accommodating the electrode assembly; and an electrolyte solution injected into the case to enable movement of lithium ions, and the like.

Such a lithium secondary battery is manufactured as follows.

First, the cathode and the anode active material coated with the cathode active material are coated, and the anode and the separator connected with the anode tab are laminated, and the electrode assembly is manufactured by winding the anode and the separator. In the case of a cylindrical lithium secondary battery, an electrolyte is injected into the case and is then sealed. In the case of a prismatic lithium secondary battery, And then an electrolyte is injected to complete the lithium secondary battery.

The cathode includes a coating region of an active material coated with an active material and an uncoated region on which an active material is not coated. At this time, the boundary portion between the application region and the non-application region of the active material prevents concentration of foreign matter when foreign substances are generated inside the battery, deactivates the island of the cathode active material generated during the coating process, In order to improve the durability and stability of the electrochemical device, taping treatment is performed with a tape film at the beginning and end of coating of the cathode active material.

However, such a conventional tape film can improve the safety of the battery, but causes a problem of battery capacity deterioration. 2, the tape film 10 is attached over the coating region 12 of the active material formed on the current collector 11 and the boundary of the non-coated region. Therefore, The attached portion becomes an area which is unnecessarily inactivated, and battery capacity decrease corresponding to about 30 to 40 mAh may occur.

Therefore, there is a need to maintain the durability and stability of the electrochemical device, which is the main purpose of tapping the cathode, and to maximize the capacity of the battery by removing the inactive area on the cathode caused by such taping treatment.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an electrochemical device having a cathode tape film capable of solving the above-described problems and improving the safety of the cathode and maximizing the battery capacity.

According to an aspect of the present invention,

A cathode having a current collector, a coating region of the cathode active material formed on at least one surface of the current collector, and an uncoated region on which the cathode active material is not coated;

Anode;

A separator interposed between the cathode and the anode; And

And a cathode tape film attached over the boundary between the coated region of the cathode active material and the uncoated region,

Wherein the cathode tape film has an activating portion capable of moving lithium ions and an inactivating portion capable of preventing lithium ions from moving,

There is provided an electrochemical device in which the activating part is attached to a coating area of a cathode active material, and the deactivating part is provided in an uncoated area of the cathode active material.

The activated portion may be composed of a porous polymer film or a nonwoven fabric.

The porous polymeric film may be formed of any one of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, But are not limited to, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, Polyethylene terephthalate, polyethylene naphthalene, or a mixture of two or more thereof.

The inactivating portion may be made of a high density film.

The cathode tape film may be formed such that the sides of the activating part and the inactivating part are joined to each other.

The cathode tape film may be formed by bonding a deactivating part to a part of a lower surface of the activating part.

The electrochemical device may be a lithium secondary battery.

An electrochemical device according to one aspect of the present invention employs a cathode film having an activating portion capable of moving lithium ions and a deactivating portion capable of preventing lithium ions from moving, the activating portion being attached to a coating region of the cathode active material, By attaching to the uncoated region of the additional cathode active material, the cathode coating portion which is inevitably taped in the cathode manufacturing process can be activated to contribute to the battery capacity as it is, so that the tri-angle region (tri- angle zone of the cathode active material and the coating of the island portion of the cathode active material can be simultaneously performed, thereby improving the stability of the electrochemical device and maximizing the capacity.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate presently preferred embodiments of the invention and, together with the description of the preferred embodiments thereof, serve to explain the principles of the invention.
1 is a perspective view showing a conventional cathode tape.
2 is a perspective view illustrating a cathode tape according to an embodiment of the present invention.
3 is a perspective view illustrating a cathode tape according to an embodiment of the present invention.
Figure 4 shows a cross section of a cathode with a conventional cathode tape.
5 shows a cross section of a cathode with a cathode tape according to an embodiment of the invention.
6 illustrates a cross section of a cathode with a cathode tape according to an embodiment of the present invention.

Hereinafter, the present invention will be described in detail. Prior to this, terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms, and the inventor should appropriately interpret the concepts of the terms appropriately It should be construed in accordance with the meaning and concept consistent with the technical idea of the present invention based on the principle that it can be defined. Therefore, the embodiments described in the present specification and the configurations shown in the drawings are merely examples of the present invention and are not intended to represent all of the technical ideas of the present invention. Therefore, various equivalents And variations are possible.

An electrochemical device according to one aspect of the present invention includes: a cathode having a current collector, a coating region of the cathode active material formed on at least one surface of the current collector, and an uncoated region on the current collector, the coating region not coated with the cathode active material; Anode; A separator interposed between the cathode and the anode; And a cathode tape film attached over the boundary between the application region and the non-application region of the cathode active material, wherein the cathode tape film has an activation portion capable of moving lithium ions and an inactive portion capable of preventing lithium ions from moving, The activating part is attached to the application area of the cathode active material, and the deactivating part is attached to the non-application area of the cathode active material.

1, a cathode tape film 10 having a single structure of a dense film like an OPP (Oriented Polypropylene) film is employed as a base film in a conventional tape used for cathode taping.

As a result, referring to FIG. 2, the conventional cathode tape 10 is attached to the active material application region 12 formed on the current collector 11 over the uncoated region, but the same is applied to both the active material application region and the non- It is made of material. Therefore, lithium ions can not move in the coated region of the active material coated with the cathode tape 10, which results in an inactive area as much as the surface on which the cathode tape 10 is adhered.

On the other hand, the cathode tape according to one aspect of the present invention is characterized in that the cathode tape film has an activating part capable of moving lithium ions and an inactivating part making it impossible to move lithium ions, and the activating part is attached to a coating area of the cathode active material, Since the inactivating portion is attached to the uncoated region of the cathode active material, the cathode coating portion inevitably taped in the cathode manufacturing process can be activated, so that the portion can contribute to the battery capacity. Thus, the tri-angle region tri-angle zone of the cathode active material and coating of the island portion of the cathode active material can be simultaneously performed, thereby improving the stability of the electrochemical device and maximizing the capacity.

The activated portion of the cathode tape may be applied to any porous substrate used in an electrochemical device. For example, a polyolefin porous polymer film or a nonwoven fabric may be used, but the present invention is not limited thereto.

Examples of the porous polymer film include high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, Polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, polyphenylene sulfide, , And polyethylene naphthalene (polyethylene naphthalene), or a film formed of a mixture of two or more thereof.

The nonwoven fabric may include, in addition to the polyolefin nonwoven fabric, for example, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate ), Polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, and polyethylenenaphthalene are used alone or in combination. Or a nonwoven fabric formed of a polymer mixed with these. The structure of the nonwoven fabric may be a spun bond nonwoven fabric or a meltblown nonwoven fabric composed of long fibers.

The thickness of the activated portion of the cathode tape is not particularly limited, but may be 5 to 50 占 퐉, and the porosity present in the activated portion is also not particularly limited, but it may be 10 to 95%.

The inactive portion of the cathode tape can be applied without limitation as long as it is a high-density film, not a porous film. Examples of such high-density films include polypropylene, stretched polypropylene (OPP), or polyethylene terephthalate.

Referring to FIG. 3, the cathode tape film 20 may be formed such that the side surfaces of the activation part 22 and the inactive part 21 are joined to each other. The width of each of the active portion and the inactive portion may be varied according to the width of the cathode tape film or the thickness of the cathode active material layer coated on the electrode body. The width of the cathode tape film may be generally 10 to 15 mm. The ratio of active to inactive portions may range from 1: 1 to 1: 3. When the ratio of the width of the active portion to the width of the inactive portion is satisfied, it is possible to maximize the battery capacity while achieving the taping effect of securing stability and durability of the electrochemical device.

Referring to FIG. 4, the cathode tape film 30 may be formed by bonding a deactivating part 31 to a part of the lower surface of the activating part 32. At this time, in the entire cathode tape film, the ratio of the width of the active portion to the inactive portion to which the inactivating portion is not bonded can be adjusted to correspond to the structure of FIG. 3 described above.

The cathode has a structure in which a cathode layer including a cathode active material, a conductive material and a binder is supported on one or both surfaces of the current collector.

As the cathode active material, a lithium-containing transition metal oxide may be preferably used. For example, Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), Li _x MnO ₂ <x <1.3, 0 <a <1, 0 <b <1), Li _x Mn ₂ O ₄ (0.5 <x <1.3), Li _x (Ni _a Co _b Mn _c ) O ₂ , 0 <c <1, a + b + c = 1), Li x Ni 1-y Co y O 2 (0.5 <x <1.3, 0 <y <1), Li x Co 1-y Mn y O 2 (0.5 <x <1.3, 0≤y <1), Li x Ni 1-y Mn y O 2 (0.5 <x <1.3, O≤y <1), Li x (Ni a Co b Mn c) O 4 (0.5 <x <1.3, 0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), Li _x Mn _{2 -z} Ni _z O ₄ Li _x CoPO ₄ (0.5 <x <1.3) and Li _x FePO ₄ (0.5 <x <1.3, 0 <z <2), 0 <z <2, Li _x Mn _{2 -z} Co _z O ₄ < x < 1.3), or a mixture of two or more thereof.

The lithium-containing transition metal oxide may be coated with a metal such as aluminum (Al) or a metal oxide. In addition to the lithium-containing transition metal oxide, sulfide, selenide and halide may also be used.

The conductive material is not particularly limited as long as it is an electron conductive material that does not cause a chemical change in an electrochemical device. In general, carbon black, graphite, carbon fiber, carbon nanotube, metal powder, conductive metal oxide, organic conductive material and the like can be used. Commercially available products as the conductive material include acetylene black series (manufactured by Chevron Chemical Co., (Chevron Chemical Company or Gulf Oil Company products), Ketjen Black EC series (Armak Company), Vulcan XC-72 (Cabot Company) and Super P (MM (MMM)). For example, acetylene black, carbon black and graphite. The conductive material may typically be added in an amount of 1 to 50 wt% based on the total weight of the mixture including the cathode active material.

The binder has a function of holding the cathode active material in the current collector and connecting the active materials, and a commonly used binder may be used without limitation. Typically from 1 to 50% by weight, based on the total weight of the mixture comprising the cathode active material.

For example, it is possible to use vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, polymethylmethacrylate, styrene Various types of binder polymers such as styrene butadiene rubber (SBR), carboxymethyl cellulose (CMC), and the like can be used.

The current collector used in the cathode may be any metal that is highly conductive and can easily adhere to the slurry of the active material and is not reactive in the voltage range of the battery. Specifically, in the case of the current collector for a cathode, it is important that the current collector metal is not oxidized in a high potential region, and examples thereof include stainless steel, aluminum, nickel, titanium, sintered carbon, , Nickel, titanium, silver, or the like may be used. The current collector may have fine irregularities on the surface thereof to increase the adhesive force of the cathode active material, and various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric are possible. Copper is oxidized at 3V and can not be applied to the cathode.

Further, the thickness of the electrode layer of the cathode (per one surface of the collector) may be 30 to 120 占 퐉, or 50 to 100 占 퐉. When the cathode satisfies such a thickness range, the amount of active material in the electrode material layer is sufficiently secured, the battery capacity can be prevented from being reduced, and the cycle characteristics and rate characteristics can be improved.

The cathode is formed by applying a mixture obtained by kneading using a cathode active material, a conductive agent, a binder and a high boiling point solvent on a current collector, drying and pressing the mixture, and then heating the mixture at a temperature of about 50 캜 to 250 캜 for about 2 hours under vacuum Followed by heat treatment to produce a cathode sheet. Then, a cathode tape film is attached to the cathode sheet to finally produce the cathode. If necessary, a filler may be further added to the mixture. The filler is optionally used as a component for suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

5, the activation portion 22 of the cathode tape film 20 is formed on the current collector 23 so as to cover the application region 24 of the cathode active material and the application region of the cathode active material on the application region 24 And the inactive portion 21 of the cathode tape film 20 is adhered to the uncoated region of the cathode active material to finally produce the cathode.

6, a cathode tape film 30 having a deactivating portion 31 joined to a part of the lower surface of the activating portion 32 is used to apply the active material applied on the current collector 33 34 to form the cathode.

The anode has a structure in which the anode layer including the anode active material and the binder is supported on one or both surfaces of the current collector. The anode layer may further include components as described in the cathode layer, if necessary.

As the anode active material, a carbon material, a lithium metal, a metal compound, or a mixture thereof, in which lithium ions can be occluded and released, can be used.

Concretely, as the carbon material, both low-crystalline carbon and highly-crystalline carbon may be used. Examples of the low crystalline carbon include soft carbon and hard carbon. Examples of highly crystalline carbon include natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch carbon fiber high temperature sintered carbon such as mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches and petroleum or coal tar pitch derived cokes.

Examples of the metal compound include metal elements such as Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Mg, , And the like. These metal compounds can be used in any form such as a single body, an alloy, an oxide (TiO ₂ , SnO _2, etc.), a nitride, a sulfide, a boride and an alloy with lithium, but an alloy with a single body, alloy, It can be increased in capacity. Among them, it may contain at least one element selected from Si, Ge and Sn, and it may further increase the capacity of the battery including at least one element selected from Si and Sn.

As the current collector for the anode, a metal exhibiting electrochemical inactivity at a working potential range of the carbon electrode (0.01 to 3.0 V relative to lithium) is used, and non-limiting examples thereof include copper, gold, nickel or a copper alloy, And the like. In addition, the current collector may be used by laminating the substrates made of the above materials.

The anode is prepared by applying a mixture obtained by kneading using an anode active material, a conductive agent, a binder and a high boiling point solvent on a current collector, drying and pressing the mixture, and then heating the mixture at a temperature of about 50 캜 to 250 캜 for about 2 hours under vacuum Heat treatment.

The thickness of the electrode layer of the anode may be 1 to 100 占 퐉, or 3 to 70 占 퐉. When the anode satisfies such a thickness range, the amount of active material in the electrode material layer is sufficiently secured, battery capacity can be prevented from being reduced, and cycle characteristics and rate characteristics can be improved.

The separator may be a conventional porous polymer film conventionally used as a separator, such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer The porous polymer film made of a polyolefin-based polymer may be used alone or in a laminate thereof, or a nonwoven fabric made of a conventional porous nonwoven fabric, for example, a glass fiber of high melting point, polyethylene terephthalate fiber or the like may be used. It is not.

According to an aspect of the present invention, there is provided an electrochemical device comprising a structure in which an electrolyte is impregnated in an electrode assembly having a structure in which a separator is interposed between a cathode and an anode.

The electrolytic solution A ⁺ B ^- A salt of the structure, such as, A ⁺ is Li ^+, Na ^+, K ⁺ comprises an alkaline metal cation or an ion composed of a combination thereof, such as, and B ^- is PF ₆ ^-, BF ₄ ^{- , Cl -, Br -, I} -, ClO 4 -, AsF 6 -, CH 3 CO 2 -, CF 3 SO 3 -, N (CF 3 SO 2) 2 -, C (CF 2 SO 2) 3 - and (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), dipropyl carbonate (DPC), dimethylsulfoxide, dimethyl sulfoxide and the like. (NMP), ethylmethyl carbonate (EMC), gamma-butyrolactone (g-butyrolactone), or mixtures thereof, in the presence of a base such as acetonitrile, dimethoxyethane, diethoxyethane, tetrahydrofuran, , But the present invention is not limited thereto.

The electrolyte injection may be performed at an appropriate stage of the battery manufacturing process, depending on the manufacturing process and required properties of the final product. That is, it can be applied before assembling the cell or at the final stage of assembling the cell.

The electrochemical device according to one aspect of the present invention includes all devices that perform an electrochemical reaction. Specific examples of the electrochemical device include capacitors such as all kinds of primary, secondary, fuel cell, solar cell or super capacitor devices. ). In particular, a lithium secondary battery including a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery may be applied to the secondary battery.

The lithium secondary battery is not limited in its outer shape, but may be cylindrical, square, pouch type, coin type, or the like using a can.

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, the present invention will be described in detail with reference to examples. However, the embodiments according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. The embodiments of the present invention are provided to enable those skilled in the art to more fully understand the present invention.

Example

94 parts by weight of a cathode active material LiCoO ₂ , 3 parts by weight of Super-P (conductive material) and 3 parts by weight of PVdF (binder) were added to NMP (N-methyl-2-pyrrolidone) as a solvent to prepare a cathode mixture slurry. A cathode sheet was prepared by coating, drying and pressing on a sheet-like aluminum foil. Thereafter, a cathode tape film composed of an active portion of a porous PE material having a width of 5 mm and an inactive portion of an OPP material having a width of 10 mm was placed on the application region of the cathode active material, Respectively.

Artificial graphite was used as the anode active material, and 92 parts by weight of artificial graphite, 4 parts by weight of Super-P (conductive material) and 4 parts by weight of PVdF (binder) were added to NMP as a solvent to prepare an anode mixture slurry. An anode sheet was prepared by coating, drying and pressing on a sheet-like copper foil.

The unit cells were assembled by stacking the cathode and anode electrode sheets prepared above and the separator of PP / PE having a thickness of 18 탆. Then, an electrolyte (ethylene carbonate (EC) / propylene carbonate (PC) / diethyl carbonate (DEC) = 3/2/5 (volume ratio) and 1 mol of lithium hexafluorophosphate (LiPF6) .

Comparative Example

A lithium secondary battery was produced in the same manner as in Example except that a cathode tape film having a width of 15 mm as a single material of OPP was used.

Evaluation of characteristics of lithium secondary battery

The capacity was evaluated using the unit cells of the lithium secondary battery produced in the above Examples and Comparative Examples.

After confirming the capacity, the battery was fully charged at 4.20 V, and the cell was disassembled to see whether the cathode active material existed in the form of an island in the cathode tape film and whether or not there was lithium precipitation on the anode facing the relevant portion The results are shown in Table 1 below.

Example Comparative Example 0.2C discharge capacity 102% 100% Lithium deposition on the anode foil surface none none

Referring to Table 1, in the case of the embodiment, the capacity was increased in comparison with the comparative example, and lithium precipitation phenomenon on the anode foil surface by the cathode islands coated abnormally by the cathode tape was not observed.

10, 20, 30: cathode tape film
11, 21, 31: Inactivating unit
12, 22, 32:
23, 33: Whole house
24, 34: application region of the active material

Claims (7)

A cathode having a current collector, a coating region of the cathode active material formed on at least one surface of the current collector, and an uncoated region on which the cathode active material is not coated;
Anode;
A separator interposed between the cathode and the anode; And
And a cathode tape film attached over the boundary between the coated region of the cathode active material and the uncoated region,
Wherein the cathode tape film has an activating portion capable of moving lithium ions and an inactivating portion capable of preventing lithium ions from moving,
Wherein the activating part is attached to the application area of the cathode active material, the deactivating part is attached to the non-application area of the cathode active material,
Wherein the activating part comprises a porous polymer film or a nonwoven fabric, and the deactivating part comprises a high-density film. delete The method according to claim 1,
Wherein the porous polymeric film is selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultra high molecular weight polyethylene, polypropylene polyethylene terephthalate, polybutyleneterephthalate, polyester, polyacetal, But are not limited to, polyamide, polycarbonate, polyimide, polyetheretherketone, polyethersulfone, polyphenylene oxide, polyphenylenesulfrode, Wherein the electrochemical device is formed of any one selected from the group consisting of polyethylene naphthalene, or a mixture of two or more thereof. delete The method according to claim 1,
Wherein the cathode tape film is formed by extending the activating portion and the side surface of the inactivating portion by bonding to each other. The method according to claim 1,
Wherein the cathode tape film is formed by bonding a deactivating portion to a part of the lower surface of the activating portion. The method according to claim 1,
Wherein the electrochemical device is a lithium secondary battery.

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