KR20150069779A - Electrochemical device having improved corrosion resistance - Google Patents

Abstract

The present invention relates to an electrochemical device, comprising: an electrode assembly including a cathode, an anode and a separator interposed between the cathode and the anode; a metal can accommodating the electrode assembly, and including a base metal can and a plating layer formed on either an inner surface or an outer surface of the base metal can; a non-aqueous electrolyte solution injected into the metal can, and impregnating the electrode assembly; a cap assembly assembled on an open upper end of the metal can; a sacrificial anode disposed in the open upper end of the cap assembly, and having a greater ionization tendency than the base metal can; washer positioned on an upper end of the sacrificial anode; and a heat-shrinkable tube formed on the outside of the metal can, the sacrificial anode and the washer, and for fixing the sacrificial anode and the washer to an upper end of the metal can. The sacrificial anode and the washer have a groove formed in a way to expose one terminal, which is connected to the electrode assembly, to the outside. The diameter of the groove formed in the sacrificial anode is greater than that of the groove formed in the washer. According to one embodiment of the present invention, the sacrificial anode, which has a greater ionization tendency than the base metal can, is attached to a lower surface of the washer having insulation functions. Accordingly, even if an impact is applied to the metal can, the plating layer is damaged, and the base metal can is exposed to the outside, the sacrificial anode, which is more susceptible to oxidation, is oxidized before the base metal can, thereby preventing the corrosion of the metal can.

Description

[0001] The present invention relates to an electrochemical device having improved corrosion resistance,

The present invention relates to an electrochemical device having improved corrosion resistance, and more particularly, to a method for manufacturing a metal can including a metal can, wherein a base metal of a metal can is oxidized by adhering a sacrificial anode having a larger ionization tendency than a base metal forming the metal can, To an electrochemical device having improved corrosion resistance.

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. The electrochemical device has received the most attention in this respect. Of these, the development of a rechargeable secondary battery has become a focus of attention. Recently, in developing such a battery, Research and development on the design of electrodes and batteries are underway.

Among the currently applied secondary batteries, the lithium secondary battery developed in the early 1990s has advantages such as 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 .

On the other hand, such an electrochemical device can be classified into a can-type electrochemical device in which an electrode assembly is embedded in a metal can, and a pouch-type electrochemical device in which an electrode assembly is embedded in a pouch of an aluminum laminate sheet, depending on the shape of the battery case . The can-type electrochemical device can be classified into a cylindrical electrochemical device and a rectangular electrochemical device depending on the shape of the metal can. The battery case of such a prismatic or cylindrical electrochemical device has a cap assembly which is hermetically sealed to the open upper end of a case with an open top, that is, a metal can and a metal can.

In general, a cylindrical electrochemical device includes a cylindrical metal can, an electrode assembly in the form of a jelly-roll, which is accommodated in a metal can, an electrolytic solution injected into the metal can, An assembly, a beading portion provided at the tip of the metal can to mount the cap assembly, and a clamping portion for sealing the electrochemical device. The metal can used in the present cylindrical electrochemical device is mainly made of nickel-plated iron.

 However, in this case, when the metal can is deformed during the assembling process, or when the nickel plating layer is damaged by the external impact and the iron is exposed to the outside, local corrosion occurs in the iron exposed to the outside under a high humidity environment. Iron is a metal with a higher ionization tendency than nickel, so that when the nickel plating layer is damaged and the iron is exposed to the outside, a phenomenon of 'small anode-to-cathode' phenomenon occurs so that a relatively small area of iron provides electrons to a large area of nickel There is a problem that corrosion of the metal can can proceed rapidly.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide a washer having an insulating function by attaching a sacrificial anode having a larger ionization tendency than a base metal can to a lower surface of an insulating washer, , The sacrificial anode which is oxidized better than the base metal can is first oxidized, thereby preventing the corrosion of the base metal can, thereby providing an electrochemical device with improved corrosion resistance.

According to an aspect of the present invention, there is provided an electrode assembly including a cathode, an anode, and a separator interposed between the cathode and the anode; A metal can containing the electrode assembly and including a base metal can, and a plating layer formed on at least one of the inner and outer surfaces of the base metal can; A non-aqueous electrolyte injected into the metal can to impregnate the electrode assembly; A cap assembly assembled to an open top of the metal can; A sacrificial anode located at an upper end of the cap assembly and having a greater ionization tendency than the base metal can; A washer located at the top of the sacrificial anode; And a heat-shrinkable tube formed outside the metal can, the sacrificial anode, and the washer, the heat shrinkable tube fixing the sacrificial anode and the washer to the upper end of the metal can, And the diameter of the groove formed in the sacrificial anode is larger than the diameter of the groove formed in the washer.

At this time, the base metal can is made of iron.

The plating layer may be made of nickel or a nickel alloy.

The metal can is a cylindrical can, and the cap assembly may have a protruding terminal of a cathode connected to the electrode assembly formed at the center.

The washer may be made of an insulating material, and the insulating material may be any one selected from the group consisting of polybutylene terephthalate, polyethylene terephthalate, polyethylene, polypropylene, and polytetrafluoroethylene. It may be a mixture of two or more.

The washer may have a thickness of 0.15 mm to 0.8 mm.

The sacrificial anode may be made of any one selected from the group consisting of magnesium, aluminum, and zinc, or a mixture of two or more thereof.

The sacrificial anode may have a thickness of 0.15 mm to 0.8 mm.

Meanwhile, the cathode may include a cathode active material containing a lithium-containing oxide.

The lithium-containing transition metal oxide may be at least one selected from the group consisting of Li _x CoO ₂ (0.5 <x <1.3), Li _x NiO ₂ (0.5 <x <1.3), Li _{x MnO 2 (0.5 <x <} 1.3), Li x Mn 2 O 4 (0.5 <x <1.3), Li x (Ni a Co b Mn c) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b <1, 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 0.5 <x <1.3, 0 < z <2), Li x Mn 2 -z Co z O 4 (0.5 <x <1.3, 0 <z <2), Li x CoPO 4 (0.5 <x <1.3) , and Li _x FePO ₄ may be (0.5 <x <1.3) or any mixture of two or more of those selected from the group consisting of.

The anode may include an anode active material containing lithium metal, a carbon material, a metal compound, or a mixture thereof.

The metal compound may be at least one selected from the group consisting of Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Or a mixture of two or more thereof.

The separator may be a porous polymer substrate or a separator including a porous coating layer comprising inorganic particles and a polymeric binder coated on at least one side of the porous polymer substrate.

At this time, the porous polymer base material may be at least one selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultrahigh molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, Polyether sulfone, polyether ether ketone, polyether sulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene, or a mixture of two or more thereof.

According to one embodiment of the present invention, a sacrificial anode having a greater ionization tendency than the base metal can is attached to the lower surface of the washer having an insulating function, an impact is applied to the metal can to damage the plating layer, Even if the sacrificial anode is oxidized better than the base metal can, the sacrificial anode is first oxidized, thereby preventing corrosion of the metal can.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate preferred embodiments of the invention and, together with the description of the invention given above, serve to further the understanding of the technical idea of the invention, It should not be construed as limited.
1 is a cross-sectional view schematically showing an upper structure of a can-type electrochemical device to which a sacrificial anode is attached on a lower surface of a washer according to an embodiment of the present invention.
Fig. 2 is a perspective view schematically showing a washer with a sacrificial anode attached to a lower surface used in the can-type electrochemical device of Fig. 1;
3 is a cross-sectional view schematically showing a cross section of a washer with a sacrificial anode attached to its lower surface.
FIG. 4 is a cross-sectional view schematically showing a state where a base metal can is oxidized due to a damaged plating layer, which is a battery case of a conventional can-type electrochemical device.
5 is a cross-sectional view schematically showing a sacrificial anode of a can-type electrochemical device with a sacrificial anode attached to a lower surface of a washer according to an embodiment of the present invention, in which a sacrificial anode is oxidized instead of a base metal can due to a damaged plated layer .

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

Therefore, the embodiments described in the present specification and the constitutions described in the drawings are merely the most preferred embodiments of the present invention, and are not intended to represent all of the technical ideas of the present invention. Therefore, It is to be understood that equivalents and modifications are possible.

FIG. 1 is a cross-sectional view schematically showing an upper structure of a can-type electrochemical device having a sacrificial anode attached to a lower surface of a washer according to an embodiment of the present invention. FIGS. 2 and 3 are cross- And Fig.

1 to 3, an electrochemical device according to an aspect of the present invention includes an electrode assembly 30 including a cathode, an anode, and a separator interposed between the cathode and the anode; A metal can (20) containing the electrode assembly (30) and comprising a base metal can, and a plating layer formed on at least one of the inner and outer surfaces of the base metal can; A nonaqueous electrolyte (not shown) injected into the metal can 20 and impregnating the electrode assembly 30; A cap assembly (10) assembled to the open upper end of the metal can (20); A sacrificial anode 60 located at the top of the cap assembly 10 and having a greater ionization tendency than the base metal can; A washer 70 positioned at the top of the sacrificial anode 60; And the metal can (20), the sacrificial anode (60), and the washer (70), and the sacrificial anode (60) and the washer (70) Wherein the sacrificial anode 60 and the washer 70 are formed with grooves such that one terminal connected to the electrode assembly 30 is exposed to the outside and the sacrificial anode 60 The diameter of the groove portion formed in the washer 70 is larger than the diameter of the groove portion formed in the washer 70. [

Meanwhile, the cathode may be connected to the cap assembly 10 with the electrode lead 31 attached thereto, and the anode may be electrically connected to the lower end of the metal can 20. Conversely, the cathode may be electrically connected to the lower end of the metal can 20, and the anode may be attached to the electrode lead 31 and connected to the cap assembly 10.

The cap assembly 10 includes a top cap 11 for forming a cathode terminal or an anode terminal, a safety vent 12 for shutting off current or discharging gas when pressure inside the electrochemical device rises, a safety vent An insulating member 13 electrically separating the current blocking member 14 from the current blocking member 14 and a current blocking member 14 connected to the cathode or the electrode lead 31 connected to the anode are sequentially stacked. The cap assembly 10 is mounted on the bead 40 formed in the metal can 20 while being mounted on the gasket 15. The cathode or the anode of the electrode assembly 30 is connected to the top cap 11 via the electrode lead 31, the current blocking member 14 and the safety vent 12 to be energized under normal operating conditions. Therefore, the top cap 11 may be formed of a metal material such as stainless steel or aluminum for energization.

At this time, the metal can 20 may be a cylindrical can or a square can, and the protruding terminal of the cathode connected to the cap assembly 10 or the protruding terminal of the anode may be formed at the center.

Further, a safety element may be further provided between the top cap 11 and the safety vent 12. However, in the case of a power tool such as a power tool or an apparatus such as an electric car or a hybrid automobile, a high output is required, 11 and the safety vent 12 may not be provided.

The safety vent 12 is disposed in such a manner that an outer circumferential surface, that is, a rim portion of the safety vent 12 is in contact with the top cap 11 at a lower portion of the top cap 11. The safety vent 12 is configured to be ruptured when the internal pressure of the electrochemical device increases to a certain level or more. For example, the safety vent 12 may be ruptured when the internal pressure of the electrochemical device is 12 to 25 kgf / cm ² . As shown in the figure, the safety vent 12 is formed so that the central portion protrudes downward, and a predetermined notch 16 may be formed near the central portion. Accordingly, when gas is generated from the inside of the electrochemical device, that is, from the electrode assembly 30 side to increase the internal pressure, the shape of the safety vent 12 is reversed and protrudes upward, It can be ruptured. Therefore, the gas that has accumulated inside the metal can 20 can be discharged to the outside through the ruptured portion of the safety vent 12.

The gasket 15 is formed by wrapping them around the rim of the top cap 11 and the safety vent 12. Accordingly, as shown in FIG. 1, the gasket 15 may have a bent portion in a 'C' shape. These gaskets 15 are made of electrically insulating material so that the rims of the top cap 11 and the safety vent 12 can be insulated from the metal can 20. Further, the gasket 15 may be made of a material having impact resistance, elasticity, and durability to support and protect the cap assembly 10. Thus, the gasket 15 can be made of, for example, polyolefine or polypropylene (PP). It is preferable that the gasket 15 is bent by mechanical working without heat treatment in order to prevent the electrical insulation from being weakened.

The current blocking member 14 is a component of the cap assembly 10, at least a portion of which is connected to the lower end of the safety vent 12. Therefore, in a normal state, the lower protruding portion of the safety vent 12 can be brought into contact with the current blocking member 14 to establish an electrical connection. However, when the internal pressure of the battery increases due to the generation of gas, the shape of the safety vent 12 is reversed, so that the electrical connection between the current blocking member 14 and the safety vent 12 can be cut off. The lower portion of the current blocking member 14 may be connected to the electrode assembly 30, and more particularly, to the electrode leads 31 attached to the electrode assembly 30. [ Therefore, in a normal state, the current blocking member 14 allows the current between the electrode assembly 30 and the safety vent 12 to be energized. A notch may be formed at a predetermined portion of the current blocking member 14 and the current blocking member 14 may be deformed together with the safety vent 12 by the internal pressure of the electrochemical device.

The insulating member 13 is sandwiched between the safety vent 12 and the current blocking member 14 so as to prevent the portion of the safety vent 12 from contacting the protruding portion of the current blocking member 14 So that the current blocking member 14 and the safety vent 12 are electrically insulated from each other.

The washer 70 covers the top cap 11 and is mounted on the bead 40. The top cap 11 having a structure as a whole is a disk or a rectangular plate and is a terminal at the center, And a sacrificial anode 70 having a diameter larger than the diameter of the groove portion formed in the washer 70 and having a greater ionization tendency than the base metal can is attached to the lower surface of the groove portion .

The washer 70 prevents the occurrence of an internal short circuit that may occur when the top cap 11 and the metal can 20 come into contact with each other. The washer 70 may be made of an insulating material. The insulating material may be polybutylene terephthalate , Polyethylene terephthalate, polyethylene, polypropylene, and polytetrafluoroethylene, or a mixture of two or more thereof.

At this time, the washer and the sacrificial anode may each have a thickness of 0.15 mm to 0.8 mm, but they are not particularly limited as they may vary depending on the material thereof. If the thickness of the washer is too thin, it can not be exhibited the desired mechanical stiffness and can be destroyed by a weak external impact. However, if the thickness of the washer is too thick, The size of the electrochemical device is increased, which is undesirable. The thickness of the sacrificial anode may vary depending on the external environment in which the electrochemical device is used.

The sacrificial anode is not limited as long as it is a metal that is larger than the ionization tendency of the base metal can. However, when the base metal can is iron, any one selected from the group consisting of magnesium, aluminum and zinc, Or a mixture thereof.

The heat-shrinkable tube 80 is formed on the outer side of the battery case after the top cap 11 and the washer 70 are coupled. When the heat-shrinkable tube 70 is retracted, the outer peripheral surface of the washer 70 The mounting of the washer 70 to the cap assembly 10 is carried out.

The heat-shrinkable tube 80 may be formed of a soft polyethyleneterephthalate resin with high shock absorption. That is, the heat-shrinkable tube 80 is a polymer synthetic resin and shrinks at a constant rate of about 25 to 75% when heat of a certain temperature (about 90 to 130 ° C) is applied. Therefore, the heat-shrinkable tube 80 is formed so as to entirely cover the outer surface of the battery case. The heat-shrinkable tube 80 has excellent insulating properties, and thus has an electrical short-circuit prevention function and an appearance-protecting function of an electrochemical device.

4 is a cross-sectional view schematically showing a metal case of a conventional can-type electrochemical device in which a damaged metal layer is oxidized due to a damaged plating layer. FIG. 5 is a cross- Sectional view schematically showing a state in which a sacrificial anode is oxidized instead of a metal can due to a damaged plating layer as a battery case of a can-type electrochemical device to which an anode is attached.

4 and 5, during the assembling process of the conventional can-type electrochemical device, deformation of the metal can is caused, or the plating layer 22 is damaged by external impact, so that the base metal can 21 When exposed to the outside, it can be exposed to an external humid environment, such as electrolyte, or directly exposed to moisture or air.

In general, the base metal can 21 may be made of iron, and the plating layer 22 may be made of nickel or a nickel alloy. The base metal of the iron material exposed through the nickel plating layer has a greater ionization tendency than nickel Since there is a strong tendency to oxidize, there is a phenomenon of 'small anode-to-cathode' in which a relatively small area of the base metal provides electrons to a large area of the plating layer, so that the corrosion of the metal can can proceed rapidly.

However, by attaching the sacrificial anode having a larger ionization tendency than the metal can to the lower surface of the washer, as in the present invention, even if the plating metal is damaged and the base metal is exposed to the outside, the sacrificial anode is first oxidized to prevent corrosion of the metal can .

On the other hand, the cathode according to the present invention has a structure in which the cathode active material layer including the cathode active material, the conductive material, and the binder is supported on one or both surfaces of the current collector.

The cathode active material may include a lithium-containing oxide, and 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 (0.5 <x <1.3), Li _x Mn ₂ O _{4 1.3), Li x (Ni a} Co b Mn c) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b <1, 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, 0≤y <1), Li _x (Ni _a Co _b Mn _c ) O ₄ (0.5 <x <1.3, 0 <a < 2, 0 <c <2, a + b + c = 2), Li x Mn 2 -z Ni z O 4 (0.5 <x <1.3, 0 <z <2), Li x Mn 2 -z Co z O _{4 (0.5 <x <1.3,} 0 <z <2), Li x CoPO 4 (0.5 <x <1.3) and 2 out of any one or combinations selected from the group consisting of _{Li x FePO 4 (0.5 <x} <1.3) And 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 anode has a structure in which an anode active material layer including an anode active material and a binder is supported on one surface or both surfaces of the current collector.

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

Concretely, as the carbonaceous material, both low-crystalline carbon and highly-crystalline carbon can 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 may be a single substance, an alloy, an oxide (TiO ₂ , SnO ₂ Or the like), a nitride, a sulfide, a boride, an alloy with lithium, or the like, but an alloy with a single substance, an alloy, an oxide, and lithium 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.

The binder used for the cathode and the anode has a function of holding the cathode active material and the anode active material on the current collector and also connecting the active materials, and a commonly used binder may be used without limitation.

For example, polyvinylidene fluoride-hexafluoropropylene (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate various kinds of binders such as polymethyl methacrylate, styrene butadiene rubber (SBR), and carboxyl methyl cellulose (CMC) can be used.

The current collector used for the cathode and the anode may be any metal having a high conductivity and a metal which can easily adhere to the slurry of the active material and is not reactive in the voltage range of the battery. Specifically, examples of the current collector for a cathode include aluminum, nickel, or a combination thereof. Examples of the current collector for an anode include copper, gold, nickel, or a copper alloy or a combination thereof And the like. In addition, the current collector may be used by laminating the substrates made of the above materials.

The cathode and the anode are kneaded using an active material, a conductive material, a binder, and a high boiling point solvent to form an electrode mixture, and then the mixture is applied to a copper foil or the like of the current collector and dried and press- Respectively, for 2 hours under a vacuum.

The thickness of the cathode active material layer may be 30 to 120 占 퐉 or 50 to 100 占 퐉 and the thickness of the anode active material layer may be 1 to 100 占 퐉 or 3 to 70 占 퐉. When the cathode active material layer and the anode active material layer satisfy such a thickness range, the amount of active material in the electrode layer is sufficiently secured, the battery capacity can be prevented from being reduced, and the cycle characteristics and rate characteristics can be improved.

On the other hand, as the separator according to the present invention, any porous polymer substrate used for an electrochemical device can be used. For example, a polyolefin porous membrane or a nonwoven fabric may be used, but the present invention is not limited thereto.

Examples of the polyolefin-based porous film include polyolefin-based polymers such as polyethylene, polypropylene, polybutylene, and polypentene, such as high-density polyethylene, linear low-density polyethylene, low-density polyethylene and ultra-high molecular weight polyethylene, One membrane can be mentioned.

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, polyphenylenesulfide, and polyethylene naphthalene, which may be used alone or in combination, And nonwoven fabrics formed by mixing these polymers. 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 porous polymer base material is not particularly limited, but may be 5 to 50 탆. The pore size and porosity present in the porous polymer base material are also not particularly limited, but may be 0.01 to 50 탆 and 10 to 95%, respectively.

The porous polymer substrate may further include a porous coating layer having inorganic particles and a polymer binder on at least one surface of the porous polymer substrate to improve the mechanical strength of the separator composed of the porous polymer substrate and to prevent a short circuit between the cathode and the anode.

In the porous coating layer, the polymer binder binds the inorganic particles together (that is, the polymer binder binds and fixes the inorganic particles) so that the inorganic particles can remain bonded to each other, and the porous coating layer is formed by the polymeric binder And maintains the engaged state. As a result, an interstitial volume is formed between the inorganic particles, and an interstitial volume between the inorganic particles becomes an empty space to form pores.

At this time, the inorganic particles used are not particularly limited as long as they are electrochemically stable. That is, the inorganic particles are not particularly limited as long as the oxidation and / or reduction reaction does not occur in the operating voltage range of the applied electrochemical device (for example, 0 to 5 V based on Li / Li ⁺ ). Particularly, when inorganic particles having ion transfer ability are used, the ion conductivity in the electrochemical device can be increased to improve the performance.

When inorganic particles having a high dielectric constant are used as the inorganic particles, dissociation of an electrolyte salt, for example, a lithium salt, in the liquid electrolyte is also increased, and ion conductivity of the electrolyte can be improved.

For the reasons stated above, the inorganic particles may include high-permittivity inorganic particles having a dielectric constant of 5 or more, or 10 or more, inorganic particles having lithium ion-transporting ability, or a mixture thereof.

Nonlimiting examples of inorganic particles having a dielectric constant of 5 or more include BaTiO ₃ , Pb (Zr _x Ti _{1 -x} ) O ₃ (PZT, where 0 <x <1), Pb _{1 - x} La _x Zr _{1 - y} Ti _y O ₃ (PLZT, where, 0 <x <1, 0 <y <1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 -xPbTiO 3 (PMN-PT, where 0 < xO, x <1), hafnia (HfO ₂ ), SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , SiC, TiO ₂ May be used alone or in combination of two or more.

In particular, the above-described _{BaTiO 3, Pb (Zr x Ti} 1 -x) O 3 (PZT, where 0 <x <1), Pb 1 - x La x Zr 1 -y Ti y O 3 (PLZT, where 0 < x <1, 0 <y < 1 Im), (1-x) Pb (Mg 1/3 Nb 2/3) O 3 - x PbTiO 3 (PMN-PT, where 0 <x <1), hafnia ( HfO ₂ ) exhibits a high dielectric constant with a dielectric constant of 100 or more, as well as a piezoelectricity in which a potential difference is generated between both surfaces due to the generation of charge when a certain pressure is applied to the piezoelectric element by being stretched or compressed. It is possible to prevent internal short-circuiting of both electrodes due to the impact, thereby improving the safety of the electrochemical device. Further, when the above-mentioned high-permittivity inorganic particles and inorganic particles having lithium ion transferring ability are mixed, their synergistic effect can be doubled.

The inorganic particles having the lithium ion transferring ability refer to inorganic particles that contain a lithium element but do not store lithium but have a function of transferring lithium ions. The inorganic particles having lithium ion transferring ability exist in the particle structure Since lithium ions can be transferred and transferred due to a kind of defect, the lithium ion conductivity in the battery can be improved and the battery performance can be improved. Examples of the inorganic particles having lithium ion transferring ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y < (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38TiO ₂ -39P ₂ O ₅ as such (LiAlTiP) _x O _y series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2, 0 <y <3 ), Li _{3 .25} Ge _{0 .25} P _{0 .75} S ₄ Lithium, such as germanium Mani help thiophosphate lithium nitro, such as _{(Li x Ge y P z S} w, 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), Li 3 N fluoride _{(Li x N y, 0 <} x <4, 0 <y <2), Li 3 PO 4 -Li 2 S-SiS 2 SiS 2 based glass, such as _{(Li x Si y S z,} 0 <x <3 , 0 <y <2, 0 <z <4), LiI-Li ₂ SP ₂ S ₅ There is P ₂ S ₅ based glass _{(Li x P y S z,} 0 <x <3, 0 <y <3, 0 <z <7) or a mixture thereof as such.

As the polymer binder used for forming the porous coating layer, a polymer commonly used in the formation of the porous coating layer in the art can be used. In particular, a polymer having a glass transition temperature (T _g ) of -200 to 200 ° C can be used because it can improve mechanical properties such as flexibility and elasticity of a finally formed porous coating layer. Such a polymer binder faithfully performs a binder function to connect and stably fix inorganic particles, thereby contributing to prevention of degradation of mechanical properties of the separator into which the porous coating layer is introduced.

Further, the polymer binder does not necessarily have ion conductivity, but when the polymer having ion conductivity is used, the performance of the electrochemical device can be further improved. Therefore, a polymer binder having a high permittivity constant can be used. Actually, the dissociation degree of the salt in the electrolytic solution depends on the permittivity constant of the solvent of the electrolyte. Therefore, the higher the permittivity constant of the polymer, the better the salt dissociation degree in the electrolyte. The permittivity constant of such a polymeric binder may be in the range of 1.0 to 100 (measurement frequency = 1 kHz), in particular, 10 or more.

In addition to the functions described above, the polymeric binder may be characterized by being capable of exhibiting a high degree of swelling of the electrolyte due to gelation upon impregnation with a liquid electrolyte. Accordingly, the solubility parameter of the polymeric binder is from 15 to 45 MPa ^1/2 or 15 to 25 MPa ^1/2, and 30 to 45 MPa ^1/2 range. Therefore, hydrophilic polymers having many polar groups can be used more than hydrophobic polymers such as polyolefins. If the solubility is more than ^1/2 and less than 15 MPa 45 MPa ^1/2, because it can be difficult to swell (swelling) by conventional liquid electrolyte batteries.

Non-limiting examples of such polymeric binders include polyvinylidene fluoride-co-hexafluoropropylene, polyvinylidene fluoride-co-trichlorethylene, poly But are not limited to, polymethylmethacrylate, polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co- polyvinyl acetate, vinyl acetate, polyethylene oxide, polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, Cyanoethylpullulan, cyanoethylpolybi Cyanoethylpolyvinylalcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxyl methyl cellulose can be given.

The weight ratio of the inorganic particles to the polymeric binder may be 50:50 to 99: 1, or 60:40 to 90:10, or 70:30 to 80:20.

The thickness of the porous coating layer composed of the inorganic particles and the polymer binder is not particularly limited, but may be in the range of 0.01 to 20 占 퐉. The pore size and porosity are also not particularly limited, but the pore size may be in the range of 0.01 to 10 mu m, and the porosity may be in the range of 5 to 90%.

Here, the electrochemical device includes all devices that perform an electrochemical reaction, and specific examples thereof include capacitors such as all kinds of secondary cells, fuel cells, solar cells, or super-capacitor devices. Particularly, 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 among the above secondary batteries is preferable.

Meanwhile, the non-aqueous electrolyte may include an electrolyte salt and an organic solvent, and the electrolyte salt is a lithium salt. The lithium salt may be any of those conventionally used for non-aqueous electrolytes for lithium secondary batteries. For example is the above lithium salt anion ^{F -, Cl -, Br -} , I -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (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 -, 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 -, (SF 5) 3 C -, ( CF ₃ SO ₂ ) ₃ C ^- , 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 ^- .

Examples of the organic solvent included in the non-aqueous electrolyte include those commonly used in non-aqueous electrolytes for lithium secondary batteries, such as ether, ester, amide, linear carbonate, cyclic carbonate, etc., Or more.

Among them, a carbonate compound which is typically a cyclic carbonate, a linear carbonate, or a mixture thereof may be included.

Specific examples of the cyclic carbonate compound include ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, Propylene carbonate, 2,3-pentylene carbonate, vinylene carbonate, vinylethylene carbonate, and halides thereof, or a mixture of two or more thereof. Examples of such halides include, but are not limited to, fluoroethylene carbonate (FEC) and the like.

Specific examples of the linear carbonate compound include any one selected from the group consisting of dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, ethyl methyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate And mixtures of two or more of them may be used as typical examples, but the present invention is not limited thereto.

In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, are high-viscosity organic solvents having a high dielectric constant and can dissociate the lithium salt in the electrolyte more easily. In addition, such cyclic carbonates can be used as dimethyl carbonate and diethyl carbonate When a low viscosity, low dielectric constant linear carbonate is mixed in an appropriate ratio, an electrolyte having a higher electric conductivity can be produced.

As the ether in the organic solvent, any one selected from the group consisting of dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether or a mixture of two or more thereof may be used , But is not limited thereto.

Examples of the ester in the organic solvent include methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate,? -Butyrolactone,? -Valerolactone,? -Caprolactone,? -Valerolactone, ε-caprolactone, or a mixture of two or more thereof, but the present invention is not limited thereto.

The injection of the nonaqueous electrolyte solution can be performed at an appropriate stage of the manufacturing process of the electrochemical device according to the manufacturing process and required properties of the final product. That is, it can be applied before assembling the electrochemical device or in the final stage of assembling the electrochemical device.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas within the scope of equivalents should be construed as falling within the scope of the present invention.

10: cap assembly 11: top cap
12: safety vent 13: insulating member
14: current blocking member 15: gasket
16: notch 20: metal can
21: base metal can 22: plated layer
30: electrode assembly 31: electrode lead
40: beading part 50: clamping part
60: Sacrificial anode 70: Washer
80: Heat-shrinkable tube

Claims (16)

An electrode assembly including a cathode, an anode, and a separator interposed between the cathode and the anode;
A metal can containing the electrode assembly and including a base metal can, and a plating layer formed on at least one of the inner and outer surfaces of the base metal can;
A non-aqueous electrolyte injected into the metal can to impregnate the electrode assembly;
A cap assembly assembled to an open top of the metal can;
A sacrificial anode located at an upper end of the cap assembly and having a greater ionization tendency than the base metal can;
A washer located at the top of the sacrificial anode; And
And a heat-shrinkable tube formed outside the metal can, the sacrificial anode, and the washer to fix the sacrificial anode and the washer to the upper end of the metal can,
Wherein the sacrificial anode and the washer are formed with a groove portion so that one terminal connected to the electrode assembly is exposed to the outside and the diameter of the groove portion formed in the sacrificial anode is larger than the diameter of the groove portion formed in the washer. The method according to claim 1,
Wherein the base metal can is made of iron. The method according to claim 1,
Wherein the plating layer is made of nickel or a nickel alloy. The method according to claim 1,
Wherein the metal can is a cylindrical can, and the cap assembly has a protruding terminal of a cathode connected to the electrode assembly formed at the center thereof. The method according to claim 1,
Wherein the washer is made of an insulating material. 6. The method of claim 5,
Wherein the insulating material is any one selected from the group consisting of polybutylene terephthalate, polyethylene terephthalate, polyethylene, polypropylene, and polytetrafluoroethylene, or a mixture of two or more thereof. The method according to claim 1,
Wherein the washer has a thickness of 0.15 mm to 0.8 mm. The method according to claim 1,
Wherein the sacrificial anode is made of any one selected from the group consisting of magnesium, aluminum and zinc, or a mixture of two or more thereof. The method according to claim 1,
Wherein the sacrificial anode has a thickness of 0.15 mm to 0.8 mm. The method according to claim 1,
Wherein the cathode comprises a cathode active material containing a lithium-containing oxide. 11. The method of claim 10,
Wherein the lithium-containing oxide is a lithium-containing transition metal oxide. 12. The method of claim 11,
The lithium-containing transition metal _{oxides, Li x CoO 2 (0.5 <} x <1.3), Li x NiO 2 (0.5 <x <1.3), Li x MnO 2 (0.5 <x <1.3), Li x Mn 2 O 4 (0.5 <x <1.3), Li x (Ni a Co b Mn c) O 2 (0.5 <x <1.3, 0 <a <1, 0 <b <1, 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 ), 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 (0.5 <x <1.3, 0 <z <2), Li x Mn 2 in _{-z Co z O 4 (0.5 <} x <1.3, 0 <z <2), Li x CoPO 4 (0.5 <x <1.3) and _{Li x FePO 4 (0.5 <x} <1.3) which is selected from the group consisting of Or a mixture of two or more thereof. The method according to claim 1,
Wherein the anode comprises an anode active material comprising lithium metal, a carbonaceous material, a metal compound, or a mixture thereof. 14. The method of claim 13,
The metal compound may be at least one selected from the group consisting of Si, Ge, Sn, Pb, P, Sb, Bi, Al, Ga, In, Ti, Mn, Fe, Co, Ni, Cu, Zn, Ag, Or a mixture of two or more thereof. The method according to claim 1,
Wherein the separator is a porous polymer substrate, or a separator comprising a porous coating layer comprising inorganic particles coated on at least one side of the porous polymer substrate and a polymeric binder. 16. The method of claim 15,
The porous polymer substrate may be at least one selected from the group consisting of high density polyethylene, low density polyethylene, linear low density polyethylene, ultrahigh molecular weight polyethylene, polypropylene, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide, polycarbonate, Wherein the electrochemical device is formed of any one selected from the group consisting of ether ketone, polyethersulfone, polyphenylene oxide, polyphenylene sulfide, and polyethylene naphthalene, or a mixture of two or more thereof.

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