KR20100016711A - Electrochemical cell having high voltage and preparation method the same - Google Patents

Abstract

PURPOSE: A method for manufacturing an electrochemical device is provided to obtain an electrochemical device with high voltage output characteristic by stably laminating a plurality of unit cells. CONSTITUTION: A method for manufacturing an electrochemical device comprises the steps of: manufacturing unit cells(10,20,30); serially connecting uncoated parts of positive and negative electrode of each unit cell; forming an insulating layer between unit cells; sealing a position contacting the unit cell with an insulating layer; installing electrode tabs(15a,15b); and sealing a serially connected module with a pouch.

Description

High voltage electrochemical device and manufacturing method thereof {Electrochemical cell having high voltage and preparation method the same}

The present invention relates to a high voltage electrochemical device and a method of manufacturing the same, and more particularly, to an electrochemical device having a high voltage and a method of manufacturing the same by connecting each of the unit cells in a triple multiple unit electrode uncoated portion of each unit cell in series. .

As portable wireless devices such as video cameras, portable telephones, and portable PCs become lighter and more functional, the demand for secondary batteries is rapidly increasing as a source of energy, and research on lithium secondary batteries having high energy density and discharge voltage among such secondary batteries is possible. Is being actively made and also commercialized and widely used.

Secondary batteries are attracting attention as a power source for electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are proposed as solutions for air pollution of conventional gasoline and diesel vehicles that use fossil fuels.

Since medium and large battery modules used in hybrid vehicles are preferably manufactured in a small size and weight as possible, square batteries and pouch-type batteries, which can be charged with high integration and have a small weight to capacity, are mainly used as battery cells of medium and large battery modules. It is used. In particular, a pouch-type battery using an aluminum laminate sheet or the like as an exterior member has attracted much attention in recent years due to the advantages of low weight and low manufacturing cost.

One or two or four battery cells are used for small mobile devices, whereas medium and large battery modules, which are electrically connected to a plurality of battery cells, are used in medium and large devices such as automobiles due to the necessity of high output capacity.

For example, when a high power lithium battery is required, such as a hybrid car, a high voltage is obtained by connecting several tens to hundreds of unit cells in series. In this series connection, a positive electrode tab and a negative electrode tab of each unit cell are connected by a printed circuit board (PCB) in which a circuit pattern is formed and put in a case. However, in this case, there is a problem that is unsafe to environmental changes such as external impact.

In addition, a plurality of unit cells are stacked to connect each positive electrode terminal and a negative electrode terminal in series to be connected in series. For this purpose, there is a problem that a free space is required between the electrode terminal and the case, and since each unit cell is stacked and stacked, a lithium secondary battery There is a problem that heat generated inside is not easily released.

That is, in the case of constructing a medium-large battery module using a plurality of battery cells or a medium-large battery module using a plurality of unit modules consisting of a predetermined unit of battery cells, there are generally many Since the members are needed, the process of assembling these members is very complicated. Moreover, space is required for joining, welding, soldering, etc. a plurality of members for mechanical fastening and electrical connection, thereby increasing the overall size of the system.

Therefore, there is a demand for a method for more robustly and stably connecting unit cells constituting a lithium battery used as a high output power source.

Therefore, the present invention is to solve the problems in the prior art in manufacturing a high-output battery by connecting the unit cells as described above.

In the present invention, in order to manufacture a high-voltage battery by connecting the unit cells in series, directly connecting the electrode ignorance of each of the unit cells, including an insulating film between each of the unit cells, the electrode tab is provided on each of the last unit cells By doing so, the above problems can be solved.

Accordingly, it is an object of the present invention to provide an electrochemical device in which a plurality of unit cells are firmly and stably stacked, and have high voltage output characteristics.

In addition, another object of the present invention to provide a method for producing a stable electrochemical device laminated as described above.

In series connection of each unit cell as in the present invention, the electrode ignorance portion of each unit cell is directly connected by welding or the like, and a plurality of unit cells are connected, and an insulating film is formed between each unit cell to stably and effectively connect the unit cells. It is possible to provide a high voltage electrochemical device.

Electrochemical device of the present invention for achieving the above object is connected by connecting the electrode uncoated portion of each unit cell in series, including an insulating film between each of the unit cells, the electrode tab is provided at both ends of each unit cell It is characterized by that.

In addition, a method of manufacturing an electrochemical device for achieving another object of the present invention comprises the steps of manufacturing a unit cell, the step of connecting the electrode uncoated portion of each unit cell in series, forming an insulating film between each unit cell Sealing the position where the unit cell and the insulating layer are in contact with each other, installing an electrode tab, and sealing the series-connected module with a pouch.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings.

1 shows a unit cell 10 according to the present invention.

An electrode assembly 11 manufactured by winding a cathode between an anode, a cathode, and a separator interposed between the anode and the cathode is configured to be housed in a pouch 12 packaging material. Since it is connected in series by ultrasonic welding, as shown in FIG. 1, only the electrode leads 13 ′ and 13 ″ are exposed to the outside of the pouch sheath.

The manufacturing process of the high voltage electrochemical device according to the present invention will be described in detail with reference to FIGS. 2A to 2D.

First, a unit cell as shown in FIG. 1 is manufactured. The unit cell may be formed of a bicell having the same electrode structure on both sides and / or a full cell having an electrode structure having different sides.

The general structure of a full cell has a structure in which the anode, the cathode, and the layered structure of the separator are cut into regular shapes and sizes and then stacked. In this case, all the electrodes use those coated on both sides of the electrode active material around the current collector. This structure is treated as one unit cell for constructing a battery by lamination, and for this purpose, the electrode and the separator film must be adhered to each other.

A full cell having the structure described above is an electrode stacked such that electrodes at both ends may form an anode and a cathode, such as an anode, a separator, a cathode, or an anode, a separator, a cathode, a separator, an anode, a separator, and an anode. Means an assembly. In order to construct an electrochemical cell including a secondary battery using such a full cell, a plurality of full cells should be stacked such that the positive electrode and the negative electrode face each other with the separation film interposed therebetween.

On the other hand, a bicell is an electrode assembly in which electrodes at both ends are stacked to form the same electrode, and a bipolar and a cathode, a separator, an anode, a separator, and a cathode are formed of an anode, a separator, a cathode, a separator, and an anode. It is divided into bipolar bicell consisting of.

Meanwhile, the unit cell as described above is configured by injecting an electrolyte layer into an electrode assembly including a positive electrode including a positive electrode active material, a negative electrode including a negative electrode active material, and a separator.

Specifically, the positive electrode is prepared by, for example, applying a mixture of a positive electrode active material, a conductive agent, and a binder onto a positive electrode current collector, followed by drying, and optionally, a filler may be further added to the mixture.

It is preferable that the positive electrode active material which concerns on this invention contains the compound containing an olivine structure. The compound containing the olivine structure is LiFePO ₄ . Specifically, a compound containing the olivine structure alone or a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides (LiMnO ₂ ) such as Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO ₂ ; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ , Cu ₂ V ₂ O ₇ and the like; Nickel-site lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B or Ga, and x = 0.01 to 0.3 oxide); Formula LiMn _2-x M _x O ₂ , wherein M = Co, Ni, Fe, Cr, Zn or Ta, and x = 0.01 to 0.1, or Li ₂ Mn ₃ MO ₈ , where M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu, or Zn); LiMn ₂ O _{4 in} which a part of lithium of the formula is substituted with alkaline earth metal ions; Disulfide compounds; It can be mixed with a compound containing a lithium intercalation material as a main component, such as a composite oxide formed by Fe ₂ (MoO ₄ ) ₃ or a combination thereof, and mainly uses a compound containing an olivine structure. It is preferable.

The positive electrode current collector is generally made to 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. For example, the surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel Surface treated with carbon, nickel, titanium, silver or the like can be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The conductive agent is typically added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Such a conductive agent is not particularly limited as long as it has conductivity without causing chemical change in the battery. Examples of the conductive agent include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists in bonding the active material and the conductive agent to the current collector, and is generally added in an amount of 1 to 50 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, Polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers, and the like.

The filler is optionally used as a component for inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

In addition, the negative electrode is manufactured by coating and drying a negative electrode material on the negative electrode current collector, and if necessary, the components as described above may be further included.

The negative electrode current collector is generally made to a thickness of 3 to 500 ㎛. Such a negative electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the surface of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver, and the like, aluminum-cadmium alloy, and the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The negative electrode material includes amorphous carbon or amorphous carbon, and specifically, carbon such as egg graphitized carbon and graphite carbon; Li _x Fe ₂ O ₃ (0 ≦ x ≦ 1), LixWO ₂ (0 ≦ x ≦ 1), Sn _x Me _1-x Me ' _y O _z (Me: Mn, Fe, Pb, Ge; Me': Al Metal complex oxides such as B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen, 0 <x ≦ 1; 1 ≦ y ≦ 3; 1 ≦ z ≦ 8); Lithium metal; Lithium alloys; Silicon-based alloys; Tin-based alloys; 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 oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

As the separator that insulates the electrodes between the anode and the cathode, a conventionally known polyolefin-based separator or a composite separator in which an organic and inorganic composite layer is formed on the olefin-based substrate may be used, and is not particularly limited.

In addition, the electrolyte layer according to the present invention is a lithium salt-containing non-aqueous electrolyte, which consists of a non-aqueous electrolyte and lithium. As the nonaqueous electrolyte, a nonaqueous electrolyte, a solid electrolyte, an inorganic solid electrolyte, and the like are used.

As said non-aqueous electrolyte, N-methyl- 2-pyrrolidinone, a propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, gamma-butyl Low lactone, 1,2-dimethoxy ethane, tetrahydroxy franc

(franc), 2-methyl tetrahydrofuran, dimethyl sulfoxide, 1,3-dioxolon, formamide, dimethylformamide, dioxolon, acetonitrile, nitromethane, methyl formate, methyl acetate, phosphate triester, Trimethoxy methane, dioxorone derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ethers, methyl pyrionate, propionic acid An aprotic organic solvent such as ethyl may be used.

Examples of the organic solid electrolyte include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polyedgetion lysine, polyester sulfides, polyvinyl alcohols, polyvinylidene fluorides, Polymers containing ionic dissociating groups and the like can be used.

Examples of the inorganic solid electrolyte include Li ₃ N, LiI, Li ₅ NI ₂ , Li ₃ N-LiI-LiOH, LiSiO ₄ , LiSiO ₄ -LiI-LiOH, Li ₂ SiS ₃ , Li ₄ SiO ₄ , Nitrides, halides, sulfates and the like of Li, such as Li ₄ SiO ₄ -LiI-LiOH, Li ₃ PO ₄ -Li ₂ S-SiS ₂ , and the like, may be used.

The lithium salt is a good material to dissolve in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO ₄ , LiBF ₄ , LiB ₁₀ Cl ₁₀ , LiPF 6, LiCF ₃ SO ₃ , LiCF ₃ CO ₂ , LiAsF ₆ , LiSbF ₆ , LiAlCl ₄ , CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, (CF ₃ SO ₂ ) ₂ NLi, chloroborane lithium, lower aliphatic lithium carbonate, lithium 4-phenyl borate, imide and the like can be used have.

In addition, for the purpose of improving charge / discharge characteristics, flame retardancy, etc., for example, pyridine, triethyl phosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, hexaphosphate triamide, etc. Nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N, N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrroles, 2-methoxy ethanol, aluminum trichloride, etc. It may be. In some cases, in order to impart nonflammability, halogen-containing solvents such as carbon tetrachloride and ethylene trifluoride may be further included, and carbon dioxide gas may be further included to improve high temperature storage characteristics.

On the other hand, the electrolyte layer according to the present invention preferably comprises a redox shuttle having a oxidation initiation potential higher than 4.2V with respect to lithium. The redox shuttle is a compound having a function of preventing the potential difference (battery voltage) between the positive electrode and the negative electrode from exceeding a predetermined value (that is, overcharge) by using a redox reaction. Specifically, the reduced type (non-ionic) redox shuttle is oxidized at the positive electrode when the battery voltage reaches a predetermined value or more during charging, and becomes the oxidized type. You are returned to). This cycle is repeated to prevent overcharging, thereby reducing the reliability of the battery.

The oxidation initiation potential of the redox shuttle is 4.2 V or more, preferably 4.2 to 5.0 V, more preferably 4.3 to 4.7 V, but is not limited thereto.

The redox shuttle is not particularly limited as long as it can exert the above effects, but specific examples thereof include hexaethyl benzene, Li ₂ B ₁₂ F ₁₂ , Li ₂ B ₁₂ F ₉ H ₃ etc. are used individually or in mixture. When the redox shuttle is included in the electrolyte layer, it is preferably included in 1 to 50 mol% based on the lithium ion concentration.

On the other hand, each unit cell having the configuration as described above is a step of connecting in series by bonding the uncoated portion of each unit cell as shown in Figure 2a. The series connection connects the uncoated parts (lead parts, 13a and 23a, 23b and 33b) of each unit cell by ultrasonic welding. That is, when each unit cell is stacked in a state as shown in FIG. 2A, the electrode unit portions 13a and 23a of one end of the first unit cell 10 and the second unit cell 20 are ultrasonically welded to each other. In addition, the electrode unit portions 23b and 33b of one end of the second unit cell 20 and the third unit cell 30 are ultrasonically welded to each other. Accordingly, when the three unit cells are unfolded, a series-connected battery can be manufactured as shown in FIG. 2D.

In the accompanying drawings of the present invention, only three unit cells are connected in series, but the present invention is not limited thereto. However, the unit cells are not limited thereto.

Next, as shown in FIG. 2B, insulating layers 40a and 40b are formed between the unit cells 10, 20, and 30. The insulating film is configured for the purpose of preventing a short circuit due to an electrode current collector portion between each unit cell or an unexpected contact between each unit cell.

It is preferable that the thickness of the said insulating film is 0.1 micrometer-2 mm, For example, Polyolefin polymer, such as polyethylene and polypropylene of chemical resistance and hydrophobicity; Sheet or nonwoven fabric made of glass fiber or polyethylene; Relatively inexpensive materials such as kraft paper are preferred.

On the other hand, when the insulating film is formed between the three unit cells as shown in the present invention as shown in Fig. 2c is then attached to the one unit cell, the insulating tape 14a, 14b, 14c). Since only three surfaces are bonded to each other, the other side is where the electrode tab is located, and thus can be welded together at the step of installing the electrode tab. However, when six or more unit cells are connected in series and an insulating film is formed between these unit cells, it is safe for the insulating tape to be formed on all four surfaces of an intermediate unit cell in which no electrode tab is provided.

The insulating tape may be a polymer film such as polyethylene terephthalate or polyimide, but is not limited thereto.

After the above steps, the positive electrode and the negative electrode tabs 15a and 15b are installed to be connected to the lead of each unit cell positioned at the end as shown in FIG. 2D. The material which comprises the said electrode tab is not specifically limited, Aluminum, titanium, copper, nickel, stainless steel, etc. can be used.

Next, FIG. 2D illustrates an unfolded cell manufactured through each of the above-described steps. Three unit cells are connected in series, and electrode tabs are installed only at both ends of each unit cell positioned at the end.

On the other hand, the electrochemical device according to the present invention includes all devices that undergo an electrochemical reaction, and specific examples thereof include all kinds of primary, secondary cells, fuel cells, solar cells, or capacitors. In particular, a lithium secondary battery is preferable among secondary batteries, and specific examples thereof include a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

According to the present invention, in connecting the unit cells in series, the electrode supporting parts of the unit cells are directly connected by welding and the like, and a plurality of unit cells are connected, and an insulating film is formed between the unit cells to stably and effectively It can be connected to provide a high voltage electrochemical device.

1 shows a unit cell according to the present invention,

2A to 2D illustrate a manufacturing process of a high voltage electrochemical device according to the present invention.

Claims (13)

Connect the negative parts of each unit cell with the uncoated part of the positive electrode and connect them in series, An insulating film between each unit cell; Electrochemical devices are provided with electrode tabs at both ends of each unit cell. The electrochemical device according to claim 1, wherein the unit cell is a full cell of which electrodes on both sides are different from each other. The electrochemical device of claim 1, wherein the unit cell is a bicell having a structure in which electrodes on both sides are the same. The electrochemical device of claim 1, wherein the unit cells connected in series are connected in units of 3n. The electrochemical device according to claim 1, wherein the bonding of the uncoated portion of the anode and the cathode is performed by ultrasonic welding. The electrochemical device according to claim 1, wherein the insulating film between each unit cell is a polyolefin-based. The electrochemical device of claim 6, wherein the insulating layer has a thickness of 0.1 μm to 2 mm. The electrochemical device of claim 6, wherein the remaining portion of the insulating layer and each unit cell is sealed with an insulating tape. The method of claim 1, wherein each unit cell is composed of an electrolyte layer is injected into the electrode assembly consisting of a positive electrode including a positive electrode active material, a positive electrode containing a negative electrode active material, and a separator, the positive electrode active material has an olivine structure An electrochemical device comprising a compound. The electrochemical device of claim 9, wherein the anode active material comprises amorphous carbon or crystalline carbon. 10. The electrochemical device of claim 9, wherein the electrolyte layer comprises a redox shuttle having an oxidation initiation potential of at least 4.2V relative to lithium. Manufacturing a unit cell, Bonding the uncoated parts of the positive electrode and the negative electrode of each unit cell and connecting them in series; Forming an insulating film between the unit cells; Sealing a position where the unit cell and the insulating layer are in contact with each other, Installing electrode tabs, and Sealing the series-connected module with a pouch. The method of claim 12, wherein the unit cells connected in series are connected in units of 3n.

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