KR20160047693A - Method of Preparing Unit Electrodes - Google Patents

Abstract

The present invention relates to a method for producing an unit electrode, comprising: a coating layer where an electrode mixture is applied on a surface of a current collector; and a blank unit where an electrode mixture is not applied. The method for producing an unit electrode comprises the steps of: (a) forming a coating layer by applying an electrode mixture including an electrode active material for positioning a blank unit on one side end unit of the electrode sheet for a current collector, on a surface of an electrode sheet; (b) heating the blank unit to a transformation point of the electrode sheet; (c) cooling the heated blank unit; and (d) forming an electrode tab by cutting the cooled blank unit.

Description

[0001] The present invention relates to a method of manufacturing a unit electrode,

The present invention relates to a method of manufacturing a unit electrode with improved safety.

BACKGROUND ART [0002] In recent years, rechargeable secondary batteries have been widely used as energy sources for wireless mobile devices. The secondary battery is also attracting attention as an energy source for electric vehicles and hybrid electric vehicles, which are proposed to solve air pollution of existing gasoline vehicles and diesel vehicles using fossil fuels. Accordingly, the types of applications using secondary batteries are diversifying due to the advantages of secondary batteries, and it is expected that secondary batteries will be applied to many fields and products in the future.

As the application fields and the products of the secondary battery are diversified, small mobile devices such as mobile phones, PDAs, digital cameras, wearable electronic devices, and notebook computers can be classified into small mobile devices One or a few small and lightweight battery cells are used. On the other hand, middle- or large-sized devices such as electric bicycles, electric motorcycles, electric vehicles, hybrid electric vehicles and the like are required to have high power and large capacity, so that a middle- or large-sized battery pack or a middle- or large-sized battery pack in which a plurality of battery cells are electrically connected is used.

Devices that receive a lot of shocks and vibrations from the outside, such as electric bicycles and electric vehicles, should have a stable electrical connection and physical connection between the elements constituting the battery module, and use a large number of batteries for high output and large capacity The safety aspect is also important because it must be implemented.

As a unit battery of such a battery module or a battery pack, a cylindrical battery cell, a prismatic battery cell, a pouch-shaped battery cell, or the like is used depending on its shape. Among them, the unit cell can be stacked with a high degree of integration, Easy pouch type battery cells are attracting much attention.

The battery cell is classified according to the structure of the electrode assembly having the anode, the cathode, and the separator interposed between the anode and the cathode. Typically, the separator includes a long sheet- A stacked (laminated) electrode assembly in which a plurality of positive electrodes and negative electrodes cut in a predetermined size unit are sequentially stacked with a separator interposed therebetween, and the like, The electrode assembly of the present invention has a structure in which a positive electrode and a negative electrode of a predetermined unit are stacked on a separation film with a separator interposed therebetween, A stacked / folded type electrode assembly having a structure in which the electrode assembly is wound with the electrode assembly may be used.

However, in the process of manufacturing the electrodes used in such an electrode assembly, wrinkles are generated in the electrode uncoated portion (connected to the electrode lead later as an exposed portion of the current collector) by thinning of the current collector and high loading of the electrode active material, There is a problem that a welding defect occurs at the time of connection, and the resistance increases, thereby affecting the safety of the battery cell in the future.

Therefore, there is a high need for a method of manufacturing an electrode for a secondary battery that can improve the safety of the battery more effectively.

SUMMARY OF THE INVENTION It is an object of the present invention to solve the above-mentioned problems of the prior art and the technical problems required from the past.

The inventors of the present application have conducted intensive research and various experiments and have found that a method of manufacturing a unit electrode including a coating layer coated with an electrode mixture on the surface of a current collector and a non- , It has been found that an unexpectedly excellent effect can be achieved when a non-coated portion is irradiated with a laser or the like and rapidly heated to perform low-speed cooling, thereby completing the present invention.

Accordingly, the present invention provides a method for manufacturing a unit electrode including a coating layer coated with an electrode mixture on a surface of a current collector and an uncoated portion coated with an electrode mixture,

(a) forming a coating layer by applying an electrode mixture containing an electrode active material on the surface of an electrode sheet so that the unoccupied portion is located at one end of the current collector electrode sheet;

(b) heating the non-coated portion to the transformation point of the electrode sheet;

(c) cooling the heated uncoated portion; And

(d) cutting the cooled uncoated portion to form an electrode tab;

As shown in Fig.

According to the present invention, by heating the non-coated portion in the process (b) and cooling the non-coated portion in the process (c), the local stress remaining in the non-coated portion due to the metal annealing phenomenon is eliminated, But the strength is prevented from lowering, and the stability of the battery cell is improved later.

In the step (a), the non-coated portion may be located at one end or both ends of the electrode sheet in the width direction perpendicular to the longitudinal direction of the electrode sheet, and may be 3% to 30% . ≪ / RTI > However, the position and size of the non-coated portion can be varied depending on the shape and size of the electrode tab of a desired battery, and therefore, it is not necessarily limited to the range of the hardness.

In the case of the sheet for a positive electrode current collector, the electrode sheet is generally made to have a thickness of 3 to 500 μm. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Examples of the positive electrode current collector include stainless steel, aluminum, nickel, titanium, sintered carbon, aluminum or stainless steel A surface treated with 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.

In the case of a sheet for an anode current collector, the thickness is generally 3 to 500 μm. Such an anode current collector is not particularly limited as long as it has electrical conductivity without causing chemical changes in the battery, and examples of the anode current collector include copper, stainless steel, aluminum, nickel, titanium, sintered carbon, a surface of copper or stainless steel A surface treated with carbon, nickel, titanium, silver or the like, an aluminum-cadmium alloy, or the like can be used. In addition, like the positive electrode collector, fine unevenness can be formed on the surface to enhance the bonding force of the negative electrode active material, and it can be used in various forms such as films, sheets, foils, nets, porous bodies, foams and nonwoven fabrics.

The cathode active material may be a cathode active material or a cathode active material. The cathode active material may be a lithium transition metal oxide, for example, lithium cobalt oxide (LiCoO ₂ ) substituted with one or more transition metals, lithium nickel oxide (LiNiO ₂ ); Lithium manganese oxide substituted with one or more transition metals; Formula _{LiNi 1-y M y O 2} ( where, M = Co, Mn, Al , Cu, Fe, Mg, B, Cr, Zn or Ga and Lim, 0.01≤y≤0.7 include one or more elements of the element) A lithium nickel-based oxide represented by the following formula: _{Li 1 + z Ni 1/3 Co 1/3} Mn 1/3 O 2, Li 1 + z Ni 0.4 Mn 0.4 Co 0.2 O 2 , such as _{Li 1 + z Ni b Mn c} Co 1- (b + c + d _{) M d O (2-e} ) A e ( where, -0.5≤z≤0.5, 0.1≤b≤0.8, 0.1≤c≤0.8, 0≤d≤0.2 , 0≤e≤0.2, b + c + d <1, M = Al, Mg, Cr, Ti, Si or Y, and A = F, P or Cl; lithium nickel cobalt manganese composite oxide; And the formula _{Li 1 + x M 1-y} M 'y PO 4-z X z ( wherein, M = a transition metal, preferably Fe, Mn, Co or Ni, M' = Al, Mg or Ti, X = F, S or N, and -0.5? X? +0.5, 0? Y? 0.5, and 0? Z? 0.1), but the present invention is not limited thereto.

The negative electrode active material may be carbon such as, for example, non-graphitized carbon or graphite carbon; _{Li x Fe 2 O 3 (0≤x≤1} ), Li x WO 2 (0≤x≤1), Sn x Me 1-x Me 'y O z (Me: Mn, Fe, Pb, Ge; Me' : Metal complex oxides such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, Halogen, 0 &lt; x &lt; Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; _{SnO, SnO 2, PbO, PbO} 2, Pb 2 O 3, Pb 3 O 4, Sb 2 O 3, Sb 2 O 4, Sb 2 O 5, GeO, GeO 2, Bi 2 O 3, Bi 2 O 4, and Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

In one specific example, the step (b) may be a method of irradiating the non-coated portion with a laser to rapidly heat the non-coated portion.

As a heating method, a high frequency induction heating method may be considered. However, since the uncoated portion subjected to the high-frequency heating treatment is deformed instead of removing wrinkles, its strength is weakened and it is easily broken by an external impact, It is not preferable.

Specifically, rapid heating by laser irradiation is performed for less than 10 seconds, and the wavelength of the laser used may be in the range of 0.6 to 11 mu m.

If the heating time is too short or the wavelength of the used laser is too long, it is difficult to exert the desired effect. On the other hand, if the wavelength of the laser is too short, excessive deformation of the non- not.

In this heating process, the uncoated portion is heated up to the transformation point of the electrode sheet. The transformation point may vary depending on the type of the electrode sheet, but may range, for example, from 350 to 550 degrees centigrade.

In the step (c), the non-coated portion may be set to cool to room temperature. Through this cooling, as described above, the local stresses remaining in the plain portion due to the metal unwinding phenomenon are eliminated.

In one specific example, the process (c) can be performed by air cooling between the process (b) and the process (d).

The process of step (c) may be set to be performed during a work time in a self-quenching manner.

The present invention also provides an electrode assembly including at least two unit electrodes. The electrode assembly may include two or more unit cells in which two or more unit electrodes are bonded together with a separator interposed therebetween.

The unit cells may be a bicell having electrodes of the same polarity positioned at both ends of the unit cell, and / or a full cell having electrodes of different polarity located at both ends of the unit cell.

Such a unit cell may be a laminated structure (lamination & stack structure) in which a separator is interposed, and in some cases, the unit cells may be a structure (stack &amp; folding structure) wound by a separator sheet.

The separation membrane is interposed between the anode and the cathode, and an insulating thin film having high ion permeability and mechanical strength is used. The pore diameter of the separator is generally 0.01 to 10 mu m and the thickness is generally 5 to 30 mu m. Such separation membranes include, for example, olefinic polymers such as polypropylene, which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like is used. When a solid electrolyte such as a polymer is used as an electrolyte, the solid electrolyte may also serve as a separation membrane.

The present invention also provides a battery cell in which an electrode assembly is embedded in a battery case.

The battery case may be a rectangular case or a laminate sheet comprising an outer coating layer made of a weather resistant polymer, an inner sealant layer made of a heat sealable polymer, and a barrier layer interposed between the outer coating layer and the inner sealant layer It may be a pouch-type battery case. Specifically, a pouch-shaped battery case made of an aluminum laminate sheet having a barrier layer made of Al.

The present invention also provides a battery pack including the battery cell as a unit cell, and a device including the battery pack.

Specific examples of such a device include a small device such as a mobile phone, a tablet computer, a notebook computer, and a wearable electronic device; a power tool powered by an electric motor; An electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), and the like; An electric motorcycle including an electric bike (E-bike) and an electric scooter (E-scooter); An electric golf cart; Power storage systems, and the like, but are not limited thereto.

The structure of the battery pack and the device are well known in the art, so a detailed description thereof will be omitted herein.

As described above, the electrode assembly according to the present invention has the effect of improving the stability of the battery cell in the future by preventing the generation of wrinkles as well as the strength of the uncoated portion by cooling the uncoated portion after heating.

1 is a flow chart illustrating a process of manufacturing a unit electrode according to an embodiment of the present invention.
FIG. 2 is a schematic view showing a coating layer coated with an electrode material mixture containing an active material on the surface of an electrode sheet in FIG. 1, and an uncoated portion coated with an electrode material mixture;
FIG. 3 is a schematic view showing a method of rapidly heating the non-coated portion in the process of FIG.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings, but the present invention is not limited by the scope of the present invention.

FIG. 1 is a flow chart showing a manufacturing process of a unit electrode according to one embodiment of the present invention. FIG. 2 is a cross-sectional view of the electrode assembly 100 including an electrode assembly 100 including an active material And a non-coated portion 120 to which an electrode mixture is not applied.

Referring to FIG. 1, a coating layer 110 coated with an electrode mixture and an uncoated portion 120 coated with an electrode mixture are present on the surface of the electrode sheet 100. The non-coated portion 120 is positioned at one end of the electrode sheet 100 in the width direction perpendicular to the longitudinal direction of the electrode sheet 100. [ The non-coated portion 120 is formed to have a size of 3% to 30% based on the width W of the electrode sheet 100.

3 is a schematic view showing a method of heating the non-coated portion 120 to the transformation point of the electrode sheet in the process of FIG.

3, the electrode sheet 100 having been subjected to the process 10 of FIG. 1 is transferred to the process 20 of FIG. 2 by a transfer device (not shown) including the roller 300, And the lower surface thereof are irradiated to the laser 210 and 211 and rapidly heated.

At this time, the rapid heating is performed for less than about 10 seconds, and the laser used is a laser having a wavelength of about 0.6 to 11 mu m. By this heating, the solid portion is heated to about 550 degrees centigrade.

The electrode sheet 100 having been subjected to the process 20 of FIG. 1 is cooled at a low speed so as to eliminate the local stress remaining in the non-coated portion 120 by the metal releasing phenomenon. This slow cooling is performed air-cooled for about 10 seconds between deliveries to the 40 process.

The electrode sheet 100 after step 30 of FIG. 1 is cut to form an electrode tab.

It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

Claims (22)

A method for manufacturing a unit electrode comprising a coating layer coated with an electrode mixture on a surface of a current collector and an uncoated portion coated with an electrode mixture,
(a) forming a coating layer by applying an electrode mixture containing an electrode active material on the surface of an electrode sheet so that the unoccupied portion is located at one end of the current collector electrode sheet;
(b) heating the non-coated portion to the transformation point of the electrode sheet;
(c) cooling the heated uncoated portion; And
(d) cutting the cooled uncoated portion to form an electrode tab;
And forming a unit electrode on the substrate. The method according to claim 1, wherein the electrode sheet is made of aluminum or copper. The method according to claim 1, wherein the electrode active material is a cathode active material or a cathode active material. The method according to claim 1, wherein in the step (a), the non-coated portion is located at one end or both ends of the electrode sheet in the width direction perpendicular to the longitudinal direction of the electrode sheet. The method according to claim 4, wherein the non-coated portion is formed to have a size of 3% to 30% based on the width of the electrode sheet. The method of manufacturing a unit electrode according to claim 1, wherein in step (b), a laser is irradiated to the non-coated area to rapidly heat the uncoated area. The method according to claim 6, wherein the rapid heating is performed for 0.1 to 10 seconds. The method according to claim 6, wherein a wavelength of the laser is 0.6 to 11 탆. The method according to claim 1, wherein in the step (b), the non-coated portion is heated to 350 to 550 degrees. The method according to claim 1, wherein in step (c), the non-coated part is cooled to 20 to 40 degrees Celsius. The method according to claim 1, wherein the local stress remaining in the uncoated portion is removed by metal annealing in the step (c). The method according to claim 1, wherein the step (c) is performed by air cooling between steps (b) and (d). The method according to claim 1, wherein the step (c) is performed for 10 to 60 seconds. An electrode assembly comprising at least two unit electrodes according to any one of claims 1 to 13. 15. The electrode assembly according to claim 14, wherein the electrode assembly includes two or more unit cells each having two or more unit electrodes joined together with a separator interposed therebetween. [16] The method of claim 15, wherein the unit cells are bicells having electrodes of the same polarity positioned at both ends of the unit cells, and / or full cells having electrodes of different polarity located at both ends of the unit cells. . The electrode assembly according to claim 15, wherein the unit cells are stacked with a separator interposed therebetween. The electrode assembly according to claim 15, wherein the unit cells are wound by a separation sheet. The battery cell according to claim 14, wherein the electrode assembly is embedded in a battery case. The battery cell according to claim 19, wherein the battery case is a pouch type case or a rectangular case. A device comprising a battery cell according to claim 19. 22. The device of claim 21, wherein the device is any one selected from the group consisting of a cell phone, a tablet computer, a notebook computer, a power tool, a wearable electronic device, an electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, . &Lt; / RTI &gt;

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