KR101547385B1 - Process for preparing secondary battery without impregnation process - Google Patents

Abstract

The present invention is a technique for manufacturing a secondary battery without a pouring process, in which the electrode assembly is carried on an electrolyte solution, is sufficiently wetted, and then enclosed in a battery case to seal the electrolyte solution, thereby avoiding a wetting process under vacuum and a pouring process. Therefore, not only the efficiency of the battery production is increased through the simplified process, but also the performance deterioration of the electrode caused by failing to sufficiently impregnate the electrolyte with the electrolyte can be improved.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a method of manufacturing a secondary battery,

The present invention relates to a method of manufacturing a secondary battery that does not include a liquid injection process.

Recently, a mobile energy source is required for various mobile and multi-contents use. Lithium rechargeable batteries have been used to meet these demands, and over time, consumers require a greater amount of energy.

However, at present, the energy density of the battery is limited. In order to increase the energy density of the battery, it is necessary to increase the loading amount of the electrode while reducing the volume and weight of other other parts. That is, in order to produce a battery having a high energy density, the thickness of the mixture layer applied to the collector of the electrode must be increased. In order to prevent an increase in the volume of the battery due to an increase in the thickness of the electrode, a technique for further increasing the energy density of the final battery while reducing the number of stacks is required. However, when the thickness of the electrode is increased, various problems occur.

One of the biggest problems is that the electrode is not sufficiently wetted with electrolyte. In general, the electrolyte does not have high affinity for the electrode material mixture components, and when the volume of the mixture layer is made large, the flow path of the electrolyte solution becomes long, so that the electrolyte solution is not easily permeated and it is difficult to achieve sufficient wettability . If the electrolyte does not sufficiently penetrate into the electrode, the movement of the ions is slowed down and the electrode reaction can not be smoothly performed, resulting in a deterioration of the efficiency of the battery.

Accordingly, there is a high need for a technique capable of shortening the manufacturing time of the battery and improving the performance of the battery by increasing the wettability of the electrode with respect to the electrolyte during the manufacturing process of the battery.

The present invention provides a method for manufacturing a secondary battery capable of improving the wettability of an electrode with respect to an electrolyte, shortening a manufacturing time of the battery, and improving battery performance.

The present invention provides a method of manufacturing a secondary battery that does not undergo a liquid injection process and a wetting process including the following steps.

Preparing an electrode assembly having a laminated structure of a positive electrode / separator / negative electrode;

Immersing the electrode assembly in the electrolyte solution for several seconds to several minutes; And

Storing the electrode assembly impregnated with the electrolyte in the battery case;

The electrode assembly is not particularly limited and may be any of a jelly-roll type, a stack type, and a stack / folding type.

The electrode assembly may be a unidirectional cell or a bidirectional cell.

The electrolytic solution may be selected from the group consisting of a non-aqueous electrolyte containing a lithium salt, a nonaqueous electrolyte, a solid electrolyte, and an inorganic solid electrolyte.

The battery case may be a pouch type case made of an aluminum laminate sheet, but is not limited thereto, and a cylindrical or rectangular case may be used.

The present invention also provides a lithium secondary battery produced by the above method.

The present invention does not include a liquid injection process, and a secondary battery is manufactured. The electrode assembly is loaded on an electrolyte solution, is sufficiently wetted, and is then closed to prevent the liquid injection process and the wetting process under vacuum. Therefore, not only the efficiency of the battery production is increased through the simplified process, but also the performance deterioration of the electrode caused by failing to sufficiently impregnate the electrolyte with the electrolyte can be improved.

In addition, aging can be performed in a state in which the electrolytic solution has already been fully impregnated. As a result, the aging process can be completed in a short time compared with the conventional process, and the process time required for manufacturing the completed cell is greatly shortened as a whole.

Unless defined otherwise, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. In general, the nomenclature used herein and the experimental methods described below are well known and commonly used in the art.

The present invention provides a method of manufacturing a secondary battery including the following steps.

(a) fabricating an electrode assembly having a laminated structure of a positive electrode / separator / negative electrode;

(b) immersing the electrode assembly in the electrolytic solution for a few seconds to several minutes;

(c) housing the electrode assembly impregnated with the electrolyte in the battery case;

According to the manufacturing method of the present invention, the electrode assembly is first directly immersed in an electrolytic solution, and is then sealed with a battery case.

Conventionally, a secondary battery is usually subjected to a pouring process in which an electrode assembly is housed in a battery case and then an electrolyte is injected, and a vacuum process is performed to make the electrolyte solution wet well on the electrode. However, this electrolytic solution impregnation process is only a few seconds to several minutes and is not enough time to be injected into an electrode having a large porosity. In addition, if each electrode is not uniformly impregnated, the performance of the cell is adversely affected, and the injected electrolyte may leak out of the pouch by decompression.

However, according to the present invention, only the dipping process of the electrode assembly into the electrolytic solution and the impregnation process through the vacuum process are achieved through a single process. As a result of the simplified process, the battery production efficiency is improved, and the performance degradation of the electrode due to failure to sufficiently impregnate the electrode with the electrolyte can be improved.

Hereinafter, a method of manufacturing a secondary battery according to the present invention will be described in detail.

The step (a) may be manufactured by a conventional method known in the art as a step of producing an electrode assembly. In general, an electrode assembly constituting a secondary battery is largely classified into a jelly-roll type (winding type) and a stack type (laminate type) according to its structure.

In the jelly-roll type electrode assembly, an electrode active material or the like is coated on a metal foil used as a current collector, dried and pressed, cut into a band shape having a desired width and length, and a cathode and an anode are diaphragm Spiral wound. Although the jelly-roll type electrode assembly is suitable for a cylindrical battery, when it is applied to a square or pouch type battery, it has disadvantages such as separation of electrode active material and low space utilization.

On the other hand, the stacked electrode assembly has a structure in which a plurality of anode and cathode unit cells are sequentially stacked, and it is easy to obtain a rectangular shape. However, when the manufacturing process is troublesome and impact is applied, There is a disadvantage that it is caused.

The electrode assembly of the present invention has a structure in which a full cell or a bi cell having a constant unit size is folded by using a continuous separation film having a long length, Was developed by the present applicant. The electrode assembly having such a structure is referred to as a so-called stack / folding type electrode assembly, which is a combined structure of a folding type and a stacking type.

The 'full cell' is a unit cell having a unit structure of a cathode / separator / cathode, in which an anode and a cathode are positioned on both sides of the cell. Such a full cell includes a cathode / separator / cathode cell and an anode / separator / cathode / separator / anode / separator / cathode cell having the most basic structure. In order to construct an electrochemical cell such as a secondary cell using such a full cell, a plurality of full cells must be stacked such that the anode and the cathode face each other with the separation film interposed therebetween.

The 'bicell' is a unit cell in which the same electrode is located on both sides of a cell, such as a unit structure of a cathode / separator / cathode / separator / anode and a unit structure of a cathode / separator / anode / separator / cathode. In order to construct an electrochemical cell including a secondary cell using such a bi-cell, a bi-cell (anodic bi-cell) and a cathode / separator / an anode / separator / anode / separator / separator / A plurality of bi-cells must be stacked such that bi-cells (cathode bi-cells) of the separator / cathode structure face each other. In some cases, more bipolar cells of the stacked number are possible, for example, a positive electrode / separator / cathode / separator / anode / separator / cathode / separator / anode and cathode / separator / anode / separator / / Bi-cell of anode / separator / cathode structure is also possible.

Further details of the stack / folding structure of the electrode assembly are disclosed in Korean Patent Application Publication Nos. 2001-0082058, 2001-0082059 and 2001-0082060 of the present applicants, It is incorporated as a reference in the content.

The electrode assembly of the present invention may be a unidirectional cell in which the positive electrode tab and the negative electrode tab are located in the same direction or a bidirectional cell in which the positive electrode tab and the negative electrode tab are disposed in opposite directions. Specifically, when the cell is immersed horizontally in a container containing an electrolytic solution, it can be applied to both unidirectional cells and bidirectional cells. However, when the cell is immersed vertically in a container containing an electrolyte, in the case of a bidirectional cell, one of the tabs and leads of the anode or the cathode may be in direct contact with the electrolyte and corrosion may occur. .

The positive electrode and the negative electrode may be manufactured by a conventional method known in the art. For example, the electrode may be manufactured by applying a mixture of an electrode active material, a conductive agent, and a binder on an electrode current collector, Therefore, a filler may be further added to the mixture.

The cathode active material may be a layered compound such as lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), or a compound substituted with one or more transition metals; A lithium manganese oxide (LiMnO2) such as Li1 + xMn2-xO4 (where x is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; Lithium copper oxide (Li2CuO2); Vanadium oxides such as LiV3O8, LiFe3O4, V2O5, and Cu2V2O7; A nickel-situ type lithium nickel oxide represented by the formula LiNi1-xMxO2 (where M = Co, Mn, Al, Cu, Fe, Mg, B or Ga and x = 0.01 to 0.3); (Wherein M is Fe, Co, Ni, Cu or Zn) or Li2Mn3MO8 (wherein M = Fe, Co, Ni, Cu or Zn) Lithium manganese complex oxide; LiMn2O4 in which part of the lithium in the formula is substituted with an alkaline earth metal ion; Disulfide compounds; Fe2 (MoO4) 3, or a composite oxide formed by a combination of these materials, or the like, may be mixed with a compound containing a lithium intercalation material as a main component.

The negative electrode active material includes amorphous carbon or regular carbon, and specifically carbon such as non-graphitized carbon and graphite carbon; B, P, Si, Group 1 of the periodic table, LixFe2O3 (0? X? 1), LixWO2 (0? X? 1), SnxMe1-xMe'yOz (Me: Mn, Fe, Pb, 2 < / RTI > group III element, halogen, 0 < x < Lithium metal; Lithium alloy; Silicon-based alloys; Tin alloy; Oxides such as SnO 2, 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 2, 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.

The electrode 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 separator may be a polyolefin separator commonly known for insulating the electrodes between an anode and a cathode, or a composite separator having an organic and inorganic composite layer formed on the olefin-based substrate, and is not particularly limited.

The immersion step (b) is a process of immersing the electrode assembly in a bath containing an electrolyte solution for a few seconds or several minutes, and the process can be very quick and simple. The specific impregnation time may vary depending on the thickness of the folded cell, the type of the active material and the membrane used, and may be impregnated for a time of, for example, 5 minutes to 10 minutes. In addition, the impregnation time can be more effectively shortened by instantaneous decompression (for example, decompression for about 30 seconds) by closing the lid of the container containing the electrolyte at the same time as the impregnation.

The electrolytic solution is, for example, a non-aqueous electrolyte containing a 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, But are not limited to, lactone, 1,2-dimethoxyethane, tetrahydroxyfuran, 2-methyltetrahydrofuran, dimethylsulfoxide, 1,3-dioxolane, formamide, dimethylformamide, Nitrile, nitromethane, methyl formate, methyl acetate, phosphoric acid triester, trimethoxymethane, dioxolane derivatives, sulfolane, methyl sulfolane, 1,3-dimethyl-2-imidazolidinone, propylene carbonate derivatives , Tetrahydrofuran derivatives, ethers, methyl propionate, ethyl propionate and the like can 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, such as Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4- LiI- LiOH, Li2SiS3, Li4SiO4, Li4SiO4- LiI- LiOH, Li3PO4- Li2S- Nitrides, halides, sulfates and the like can be used.

The lithium salt is a substance that is soluble in the non-aqueous electrolyte. For example, LiCl, LiBr, LiI, LiClO4, LiBF4, LiB10Cl10, LiPF6, LiCF3SO3, LiCF3CO2, LiAsF6, LiSbF6, LiAlCl4, CH3SO3Li, CF3SO3Li, 2NLi, chloroborane lithium, lithium lower aliphatic carboxylate, lithium 4-phenylborate, imide and the like can be used.

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 and the like 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.

The step (c) is a step of housing the electrode assembly impregnated with the electrolytic solution in the battery case. The battery case is not particularly limited, and a cylindrical, coin, square or pouch type can be used. For example, the pouch type case may be manufactured by processing an aluminum laminate sheet.

The method for manufacturing a lithium secondary battery according to the present invention may further include a formation process or an aging process in addition to the steps described above.

The conversion step is a step of forming an SEI film on the surface of the negative electrode by partially performing charge and discharge in order to activate the battery. Generally, charging and discharging are repeatedly performed with a constant current or constant voltage.

The aging step stabilizes the activated battery by leaving the activated battery for a predetermined period.

Further, it may include a degassing step after the aging step. In this case, a gas such as carbon dioxide and methane generated during the formation of the SEI film in the formation step, as well as the swelling phenomenon The above-mentioned components of the gas and the like which cause the above-mentioned problems are removed.

The above-described production method is not limited thereto, and in some cases, the above-described processes may be selectively added or excluded from the pre- and post-steps, or may be merged into one.

The present invention also provides a lithium secondary battery produced by the above method. The lithium secondary battery manufactured by the above method includes a lithium metal secondary battery, a lithium ion secondary battery, a lithium polymer secondary battery, or a lithium ion polymer secondary battery.

Also, the present invention provides a battery module having a plurality of secondary batteries connected in series or parallel according to a conventional method in the art, thereby improving the stability.

It is also possible to provide a battery pack with improved safety including the battery module according to a conventional method in the art.

The battery pack with improved safety includes a power tool; Electric vehicles such as Electric Vehicle (EV), Hybrid Electric Vehicle (HEV) and Plug-in Hybrid Electric Vehicle (PHEV); An electric motorcycle such as an E-bike or an E-scooter; Electric golf cart; Electric truck; And electric commercial vehicles.

Hereinafter, the present invention will be described in more detail with reference to Examples, but the present invention is not limited to these Examples.

Example  1. Preparation of lithium secondary battery

1-1. Anode manufacturing

LiCoO2 was used as a positive electrode active material and added to NMP (N-methyl-2-pyrrolidone) as a solvent in a composition of 95% by weight of LiCoO2, 2.5% by weight of Super-P (conductive agent) and 2.5% by weight of PVDF The slurry of the mixture was prepared, coated on the aluminum current collector, dried and pressed to prepare a positive electrode.

1-2. Cathode manufacture

Artificial graphite was used as the negative electrode active material, and the negative electrode mixture slurry was prepared by adding NMP as a solvent in the composition of 95.3% by weight of artificial graphite, 0.7% by weight of Super-P (conductive agent) and 4% by weight of PVDF , Coated on a copper collector, dried and pressed to produce a negative electrode.

1-3. Electrolytic solution manufacturing

An electrolyte solution was prepared by dissolving 1 mole of LiPF6 in a solution having a volume ratio of ethylene carbonate (EC) and dimethyl carbonate (DMC) of 1: 2.

1-4. Battery Manufacturing

An electrode assembly was prepared by sandwiching a porous separator (trademark: Celgard) between the positive electrode and negative electrode prepared in the above 1-1 and 1-2, and the electrode assembly was immersed in a bath containing the electrolyte prepared in 1-3 above, And immersed for 0.2 hour. Then, the electrode assembly was taken out and charged into a pouch-shaped battery case to complete the battery.

Comparative Example  1. Manufacture of lithium secondary battery by conventional method

The electrode assemblies were manufactured by interposing a polypropylene separator between the positive and negative electrodes prepared in 1-1 and 1-2 in the steps 1-4 of Example 1, and then charged into a pouch-shaped battery case. To prepare a battery.

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. The scope of the present invention should be interpreted based on the scope of the following claims and all technical ideas within the scope of equivalents thereof are to be construed as being included in the scope of the present invention. It is to be understood that the invention is not limited thereto.

Claims (5)

Preparing an electrode assembly having a laminated structure of a positive electrode / separator / negative electrode;
Immersing the electrode assembly in a non-aqueous electrolyte containing a lithium salt-containing non-aqueous electrolyte for 5 minutes to 10 minutes; And
Storing the electrode assembly impregnated with the electrolyte in the battery case;
Wherein the nonaqueous electrolyte secondary battery comprises a nonaqueous electrolyte secondary battery.
The method according to claim 1,
Wherein the electrode assembly is selected from the group consisting of a jelly-roll type, a stack type, and a stack / folding type.
The method according to claim 1,
Wherein the electrode assembly is a unidirectional cell or a bidirectional cell.
The method according to claim 1,
Wherein the step of immersing the electrode assembly is performed under a reduced pressure of the electrode assembly.
The method according to claim 1,
Wherein the battery case is a pouch type case made of an aluminum laminate sheet.