KR101414334B1 - Electrochemical cell having high voltage and preparation method the same - Google Patents

Abstract

The present invention relates to a high-capacity electrochemical device in which unoccupied portions of each unit cell are connected in series and an insulating film is provided between each unit cell, and electrode tabs are provided at both ends of each unit cell, and a method of manufacturing the same. In the unit connection of the unit cells in series, the unit cells of each unit cell are directly connected by welding or the like, a plurality of unit cells are connected to each other, and an insulating film is formed between the unit cells to stably and effectively connect the unit cells. A chemical device can be provided.

Membrane * Physical Properties * Battery * Device * Safety

Description

TECHNICAL FIELD The present invention relates to a high voltage electrochemical device and a method of manufacturing 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 by serially connecting electrode unit parts of each unit cell in units of three units of each unit cell and a manufacturing method thereof .

As portable wireless devices such as video cameras, portable telephones, and portable PCs have become lighter and more sophisticated, the demand for secondary batteries as energy sources is rapidly increasing. Research on lithium secondary batteries having such high energy density and discharge voltage Has been actively performed, and has been commercialized and widely used.

Secondary batteries are attracting attention as power sources for electric vehicles (EVs) and hybrid electric vehicles (HEVs), which are proposed to solve air pollution in conventional gasoline vehicles and diesel vehicles using fossil fuels.

Since a middle- or large-sized battery module used in a hybrid vehicle or the like is preferably manufactured with a small size and a weight as much as possible, a prismatic battery, a pouch-type battery, and the like, which can be charged with a high degree of integration and have a small weight- . Particularly, a pouch-shaped battery using an aluminum laminate sheet or the like as an exterior member has recently attracted a great deal of attention due to its advantages such as a small weight and a low manufacturing cost.

In a small mobile device, one or two or more battery cells are used per device, while a middle- or large-sized battery module such as an automobile is used as a middle- or large-sized battery module in which a plurality of battery cells are electrically connected due to the necessity of a large-

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

In addition, since a plurality of unit cells are stacked on top of each other and each of the positive and negative terminals are welded and connected in series, there is a problem in that a clearance space is required between the electrode terminal and the case. Since each unit cell is stacked and stacked, There is a problem that the heat generated inside is not easily released.

That is, when a middle- or large-sized battery module is formed by using a plurality of battery cells or a middle- or large-sized battery module is formed by using a plurality of unit modules including battery cells of a predetermined unit, Since the members are required, the process of assembling these members is very complicated. Moreover, space is required for the joining, welding, soldering and the like of a number of members for mechanical fastening and electrical connection, thereby increasing the overall size of the system.

Accordingly, there is a need for a method of connecting the unit cells constituting a lithium battery used as a high-output power source more stably and stably.

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

In the present invention, in manufacturing a high-voltage battery by connecting unit cells in series, the electrode uncoated portions of the unit cells are directly connected, an insulating film is included between the unit cells, and electrode tabs The above problems can be solved.

SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an electrochemical device having a plurality of unit cells stacked firmly and stably and having high output characteristics.

Another object of the present invention is to provide a method of manufacturing an electrochemical device stably stacked as described above.

In the present invention, when the unit cells are connected in series, the unit cells of each unit cell are directly connected by welding or the like, a plurality of unit cells are connected, and an insulating film is formed between the unit cells, thereby stably and effectively connecting the unit cells Thereby providing a high-voltage electrochemical device.

According to an aspect of the present invention, there is provided an electrochemical device comprising: a plurality of unit cells connected in series, each unit cell including an insulating layer between the unit cells; .

According to another aspect of the present invention, there is provided a method of manufacturing an electrochemical device, comprising the steps of: fabricating a unit cell, connecting the electrode uncoated portions of the unit cells to form a series connection, , Sealing a position where the unit cell and the insulating film are in contact with each other, installing an electrode tab, and sealing the series-connected module with a pouch.

Hereinafter, 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.

The electrode assembly 11 is manufactured by winding a separator between an anode and a cathode and between the anode and the cathode. The electrode assembly 11 is housed in a casing 12 of the pouch 12. So that only the electrode lead portions 13 'and 13' 'are exposed to the outside of the pouch outer cover material as shown in FIG. 1, since they are connected in series through ultrasonic welding.

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

First, the unit cell as shown in FIG. 1 is manufactured. The unit cell may be a bi-cell having the same electrode structure on both sides and / or a pull cell having a different electrode structure on both sides.

In general, the structure of a pull cell has a structure in which a layered structure of an anode, a cathode, and a separator is cut into regular shapes and sizes and then laminated. Here, all of the electrodes are coated with an electrode active material on both sides of the current collector. This structure is handled as one unit cell for constituting the battery by lamination, and the electrodes and the separator film should be adhered to each other.

The full cell having the above structure may be a full cell having a structure in which electrodes at both ends such as a cathode / separator / cathode or a cathode / separator / cathode / separator / anode / separator / Assembly. In order to construct an electrochemical cell including the secondary cell by using such a pull cell, a plurality of pull cells should be stacked such that the anode and the cathode 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 formed so as to form the same electrode, and includes a cathode type separator composed of a cathode / separator / cathode / separator / anode, a cathode / separator / anode / separator / And a positive bipolar cell composed of a positive bipolar cell.

The unit cell includes an anode including a cathode active material, a cathode including a cathode active material, and a separator. The electrolyte layer is injected into the electrode assembly.

Specifically, the anode is prepared, for example, by coating a mixture of a cathode active material, a conductive agent and a binder on a cathode current collector, and then drying the cathode active material. Optionally, a filler may be further added to the mixture.

The cathode active material according to the present invention preferably includes a compound containing an olivine structure. Compound comprising the olivine structure is LiFePO _4. Specifically, the compound containing the olivine structure may be used 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; A lithium manganese oxide (LiMnO ₂ ) such as LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, etc. represented by the formula Li _{1 + x} Mn _{2 -x} O ₄ (where x is 0 to 0.33); Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiFe ₃ O ₄ , V ₂ O ₅ and Cu ₂ V ₂ O ₇ ; A nickel-situ type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ (where 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} ( where, M = Co, Ni, Fe , Cr, and Zn, or Ta, x = 0.01 ~ 0.1 Im) or Li ₂ Mn ₃ MO ₈ (where, M = Fe, Co, Ni, Cu, or Zn); LiMn ₂ O _{4 in} which part of the lithium in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe ₂ (MoO ₄ ) _3, or a composite oxide formed by a combination of these compounds, and the like, and a compound mainly containing an olivine structure can be used in combination with a compound containing a lithium intercalation material as a main component .

The cathode current collector generally has a thickness of 3 to 500 mu m. Such a positive electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery, and may be formed of a material such as stainless steel, aluminum, nickel, titanium, sintered carbon, or a surface of aluminum or stainless steel 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.

The conductive agent is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture including the cathode active material. Such a conductive agent is not particularly limited as long as it has electrical conductivity without causing a chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon black 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, aluminum, and nickel powder; Conductive whiskey 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 which assists in binding of the active material and the conductive agent and bonding to the current collector, and is usually added in an amount of 1 to 50% by weight based on the total weight of the mixture containing the cathode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, 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 suppressing the expansion of the anode, and is not particularly limited as long as it is a fibrous material without causing a chemical change in the battery. Examples of the filler include olefin polymers such as polyethylene and polypropylene; Fibrous materials such as glass fibers and carbon fibers are used.

The negative electrode is manufactured by applying a negative electrode material on a negative electrode collector and drying the same, and may further include the above-described components as needed.

The negative electrode collector is generally made to have a thickness of 3 to 500 mu m. Such an anode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery, and may be formed of a material such as copper, stainless steel, aluminum, nickel, titanium, fired carbon, 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 negative electrode material includes amorphous carbon or regular carbon, and specifically carbon such as hard 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, , B, P, Si, Group 1, Group 2 and Group 3 elements of the periodic table, Halogen, 0 <x <1> 1 <y> 3, 1 <z <8); 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.

A polyolefin-based separator commonly known as a separator for insulating the electrodes between the anode and the cathode or a composite separator having an organic-inorganic composite layer formed on the olefin-based substrate may be used without particular limitation.

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

Examples of the nonaqueous electrolytic solution include N-methyl-2-pyrrolidinone, propylene carbonate, ethylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, 1,2-dimethoxyethane, tetrahydroxyfuran

the organic solvent is selected from the group consisting of tetrahydrofuran, 2-methyl tetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, dioxolane, acetonitrile, nitromethane, methyl formate, methyl acetate, Diethoxymethane, dioxolane derivatives, sulfolane, methylsulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives, tetrahydrofuran derivatives, ether, methyl pyrophosphate, Ethylenic organic solvents such as ethyl acetate may be used.

Examples of the organic solid electrolyte include a polymer electrolyte such as a polyethylene derivative, a polyethylene oxide derivative, a polypropylene oxide derivative, a phosphate ester polymer, an agitation lysine, a polyester sulfide, a polyvinyl alcohol, a polyvinylidene fluoride, Polymers containing ionic dissociation 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 and sulfates of Li such as Li ₄ SiO ₄ -LiI-LiOH and Li ₃ PO ₄ -Li ₂ S-SiS ₂ can be used.

The lithium salt is a material that is readily soluble in the non-aqueous electrolyte, for example, LiCl, LiBr, LiI, LiClO 4, LiBF 4, LiB 10 Cl 10, LiPF6, 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 carboxylate lithium, 4-phenylborate lithium, have.

For the purpose of improving charge / discharge characteristics, flame retardancy, etc., non-aqueous electrolytes may be used in the form of, for example, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylenediamine, glyme, N, N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. are added It is possible. In some cases, a halogen-containing solvent such as carbon tetrachloride or ethylene trifluoride may be further added to impart nonflammability, or a carbon dioxide gas may be further added to improve high-temperature storage characteristics.

Meanwhile, the electrolyte layer according to the present invention preferably includes a redox shuttle having an oxidation initiation potential of 4.2 V or more with respect to lithium. The redox shuttle is a compound having a function of preventing a potential difference (battery voltage) between positive and negative electrodes from exceeding a predetermined value (that is, overcharge) by using an oxidation-reduction reaction. Specifically, a reduced (non-ionic) redox shuttle oxidizes at the anode when the battery voltage becomes a predetermined value or more at the time of charging, and the oxidized form is reduced at the cathode, ). This cycle is repeated to prevent overcharging, thereby preventing the reliability of the battery from deteriorating.

The oxidation start potential of the redox shuttle is preferably 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.

Specific examples of the redox shuttle are not particularly limited as long as they can exhibit the above-mentioned effects. Specific examples thereof include hexa ethyl benzene, Li ₂ B ₁₂ F ₁₂ , Li ₂ B ₁₂ F ₉ H _3, etc. may be used alone or in combination. When the redox shuttle is contained in the electrolyte layer, it is preferably contained in an amount of 1 to 50 mol% based on the lithium ion concentration.

In the meantime, each unit cell having the above-described structure is connected in series by connecting unoccupied portions of the unit cells as shown in FIG. 2A. The series connection connects the uncoated portions (lead portions 13a and 23a, 23b and 33b) of each unit cell through ultrasonic welding. 2A, the electrode uncoated portions 13a and 23a at one end of the first unit cell 10 and the second unit cell 20 are welded to each other by ultrasonic welding And the electrode uncoated portions 23b and 33b at 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 expanded, a series-connected battery can be manufactured as shown in FIG. 2D.

Although the number of unit cells connected in series is three in the accompanying drawings of the present invention, the present invention is not limited thereto.

The next step is to form the insulating films 40a and 40b between the unit cells 10, 20 and 30 as shown in FIG. 2b. The insulating film is formed for the purpose of preventing electrode current collecting portions between the unit cells from contacting each other or short-circuiting due to unexpected contact between the unit cells.

The thickness of the insulating film is preferably 0.1 to 2 mm, and examples thereof include polyolefin-based polymers such as polyethylene and polypropylene which are chemically resistant and hydrophobic; A sheet or nonwoven fabric made of glass fiber, polyethylene or the like; Relatively cheap materials such as kraft paper are preferable.

When the insulating film is formed between three unit cells as in the present invention, the insulating film is attached to one unit cell as shown in FIG. 2C. Insulating tapes 14a, 14b, 14c. The reason why only the three surfaces are bonded is that the other surface is where the electrode tabs are located, so that the same can be welded in the step of installing the electrode tabs. However, when six or more unit cells are connected in series and an insulating film is formed between these unit cells, it is safe that the insulating tape is formed on all four sides in an intermediate unit cell where 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, anode and cathode tabs 15a and 15b are provided to be connected to the lead portions of the unit cells positioned at the end as shown in FIG. 2D. The material constituting the electrode tab is not particularly limited, and aluminum, titanium, copper, nickel, stainless steel, or the like can be used.

FIG. 2D is a plan view of the cell fabricated through the above steps, in which three unit cells are connected in series, and electrode tabs are provided at both ends of each unit cell positioned at the end.

Meanwhile, the electrochemical device according to the present invention includes all devices that perform an electrochemical reaction, and specific examples thereof include all kinds of primary and secondary batteries, a fuel cell, a solar cell, and a capacitor. Particularly, a lithium secondary battery among the secondary batteries is preferable, 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, when the unit cells are connected in series, the electrode-free portion of each unit cell is directly connected by welding or the like, a plurality of unit cells are connected, and an insulating film is formed between each unit cell, So that it is possible to provide a high-voltage electrochemical device.

1 shows a unit cell according to the present invention,

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

Claims (13)

A first unit cell having first and second uncoated portions having different polarities at both ends and a second uncoated portion having a second polarity; A second unit cell having third and fourth uncoated portions having different polarities at both ends; An insulating film formed between the first unit cell and the second unit cell and formed of a polyolefin-based material; And And an electrode tab formed on the first non-coated portion and the fourth coated portion, The different polarities are cathode or anode, Wherein the second uncoated portion and the third uncoated portion are joined and connected in series to seal the position of the first unit cell in contact with the insulating film of the remaining surface excluding the first uncoated portion, . The electrochemical device according to claim 1, wherein the first unit cell and the second unit cell are electrodes of a double-sided structure having different structures. The electrochemical device according to claim 1, wherein the first unit cell and the second unit cell are bi-cells having the same structure of electrodes on both sides. The electrochemical device according to 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 second unconsumed portion and the third unconsumed portion is performed by ultrasonic welding. delete The electrochemical device according to claim 1, wherein the thickness of the insulating film is 0.1 to 2 mm. The electrochemical device according to claim 1, wherein the remaining portion of the insulating film, which is in contact with the first unit cell, is sealed with an insulating tape. The method according to claim 1, wherein the first unit cell and the second unit cell are formed by injecting an electrolyte layer into an electrode assembly composed of a positive electrode including a positive electrode active material, a positive electrode including a negative electrode active material, and a separator, Wherein the active material comprises a compound having an olivine structure. 10. The electrochemical device according to claim 9, wherein the negative electrode active material comprises amorphous carbon or crystalline carbon. 10. The electrochemical device according to claim 9, wherein the electrolyte layer comprises a redox shuttle having an oxidation initiation potential higher than 4.2 V with respect to lithium. Manufacturing a unit cell, Connecting the positive electrode of each unit cell and the non-negative portion of the negative electrode to connect them in series, Forming a polyol-based insulating film between the unit cells, A step of sealing a position where a unit cell of the other surface of the unit cell other than one of the plurality of surfaces is in contact with the insulating film, Providing an electrode tab on the uncoated portion of the unsealed surface, and And sealing the serially connected module with a pouch. 13. The method of claim 12, wherein the unit cells connected in series are connected in units of 3n.

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