WO2018070701A1

WO2018070701A1 - Secondary battery unit cell having improved wettability and manufacturing method therefor

Info

Publication number: WO2018070701A1
Application number: PCT/KR2017/010646
Authority: WO
Inventors: 이상균; 조주현; 김덕회; 구자훈
Original assignee: 주식회사 엘지화학
Priority date: 2016-10-10
Filing date: 2017-09-26
Publication date: 2018-04-19
Also published as: HUE059998T2; PL3396767T3; ES2928898T3

Abstract

A unit cell according to one embodiment of the present invention comprises: a center electrode having a first polarity; a pair of separation membranes respectively laminated on both surfaces of the center electrode; and an upper electrode and a lower electrode respectively laminated on the pair of separation membranes and having a second polarity, wherein the separation membranes have patternized adhesion.

Description

Unit cell for secondary battery with improved wettability and manufacturing method thereof

The present invention relates to a secondary battery cell with improved wettability and a method of manufacturing the same, and more particularly, to a secondary battery cell with improved wettability through an adhesive force control between a separator and an electrode and a method of manufacturing the same.

This application is a priority application for Korean Patent Application No. 10-2016-0130780, filed Oct. 10, 2016, and all the contents disclosed in the specification and drawings of the application are incorporated herein by reference.

In addition, this application is a priority application for Korean Patent Application No. 10-2017-0123465, filed on September 25, 2017, and all contents disclosed in the specification and drawings of the application are incorporated herein by reference. do.

In the conventional polymer cell manufacturing process, since the bicells are laminated at a constant temperature / pressure for fairness, there is a problem in that wettability at the interface between the electrode and the separator is lowered.

That is, when the adhesive force at the interface between the electrode and the separator is constant and the electrode / separation membrane is completely and completely in close contact with each other, it is difficult for the electrolyte to penetrate between the electrode and the separator and the performance of the secondary battery cannot be fully exhibited. do.

In particular, under the same process conditions, the adhesion at the anode / separator interface is stronger, and thus, the wettability tends to be more prominent, and thus, the performance of the secondary battery is inevitably deteriorated.

In addition, when the adhesion between the electrode / separator interface is uniformly high as a whole, there is a problem that it is difficult to smoothly discharge the gas generated in the formation process performed in the manufacturing process of the secondary battery. If the gas is not discharged smoothly, there may also be a problem that a lithium plating phenomenon may occur.

The present invention was devised in consideration of the above-described problems, and in the unit cell used for fabricating a secondary battery, the wettability of the electrolyte is improved by allowing a weak or non-adhesive region between the electrode and the separator to exist. On the other hand, an object of the present invention is to enable smooth discharge of the gas generated in the secondary battery in the formation process.

However, the technical problem to be solved by the present invention is not limited to the above-described problem, another task that is not mentioned will be clearly understood by those skilled in the art from the description of the invention described below.

According to an aspect of the present invention, there is provided a unit cell including: a central electrode having a first polarity; A pair of separators each laminated on both surfaces of the center electrode; And an upper electrode and a lower electrode each laminated on the pair of separators and having a second polarity, wherein the separators have a patterned adhesive force.

The separator may include a first region having a first adhesive force; And a second region having an adhesive force lower than the first adhesive force.

The first region may be a plasma treated region, and the second region may be a region not subjected to plasma treatment.

On the other hand, the manufacturing method of a unit cell according to an embodiment of the present invention for solving the above technical problem, the step of supplying a central electrode; Supplying separators on both sides of the center electrode; Treating plasma on the surface of the separator, but performing plasma treatment on a portion of the separator and preventing plasma treatment on the remaining region; Supplying an upper electrode and a lower electrode on the separator; And performing lamination so that each of the center electrode, the upper electrode, and the lower electrode is adhered to the separator.

The laminating may include: applying heat on the upper electrode and the lower electrode; And compressing by applying pressure on the upper electrode and the lower electrode to which heat is applied.

The method of manufacturing a unit cell for a secondary battery may further include cutting each of the supplied central electrode, upper electrode, lower electrode, and separator to a predetermined length.

The method of manufacturing a unit cell for a secondary battery may further include inspecting and discharging the unit cell for a secondary battery in which lamination is completed.

According to an aspect of the present invention, the electrolyte wettability at the electrode / separation membrane interface is improved, resulting in performance improvement of the secondary battery.

According to another aspect of the present invention, in the formation process of the secondary battery manufacturing process, it is possible to smoothly remove the gas generated in the secondary battery.

The following drawings attached to this specification are illustrative of the preferred embodiments of the present invention, and together with the detailed description of the invention to serve to further understand the technical spirit of the present invention, the present invention is a matter described in such drawings It should not be construed as limited to.

1 and 2 are views illustrating a unit cell for a secondary battery according to an embodiment of the present invention.

3 and 4 are views showing a positive electrode and a negative electrode applied to the unit cell for a secondary battery according to an embodiment of the present invention.

5 is a schematic view showing a facility for manufacturing a unit cell for a secondary battery according to the present invention.

6 is a view showing a plasma processing apparatus used for manufacturing a unit cell for a secondary battery according to an embodiment of the present invention.

FIG. 7 is a diagram illustrating a mask applied to the plasma processing apparatus illustrated in FIG. 6.

FIG. 8 is a view illustrating a wettability test result of a conventional unit cell for a secondary battery. FIG.

9 is a view showing the wettability test results of the unit cell for a secondary battery according to an embodiment of the present invention.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the common or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own invention. Based on the principle that can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the embodiments described in the specification and the drawings shown in the drawings are only some of the most preferred embodiments of the present invention and do not represent all of the technical spirit of the present invention, various modifications that can be replaced at the time of the present application It should be understood that there may be equivalents and variations.

First, the structure of a unit cell for a secondary battery according to an embodiment of the present invention will be described with reference to FIGS. 1 to 4.

1 and 2 are views showing a unit cell for a secondary battery according to an embodiment of the present invention, Figures 3 and 4 are views showing a positive electrode and a negative electrode applied to the unit cell for a secondary battery according to an embodiment of the present invention.

1 and 2, a unit cell for a secondary battery according to an exemplary embodiment of the present invention may include a center electrode having a first polarity, a pair of separators 3 laminated on both surfaces of the center electrode, and An upper electrode and a lower electrode are laminated on the pair of separators and have a second polarity opposite to the first polarity.

The unit cells configured such that the electrodes located at the outermost sides have the same polarity with each other are commonly referred to as bicells.

As shown in FIG. 1, a unit cell of the bicell type includes a bipolar bicell having an upper electrode and a lower electrode as the anode 1, and a central electrode as the cathode 2, and as shown in FIG. 2. The upper electrode and the lower electrode may be categorized into a cathode type bicell including the cathode 2 and the center electrode composed of the anode 1.

A secondary battery constructed using such a bicell may have a form in which a bipolar bipolar cell and a negative bipolar cell are alternately stacked with a separator interposed therebetween. As the stacking method of the bicells, a simple stacking method, a stacking / folding method, or the like may be applied.

The positive electrode 1 applied to the unit cell for a secondary battery according to an embodiment of the present invention, as shown in FIG. 3, includes a positive electrode current collector 1 a and a positive electrode active material 1 b laminated on the surface thereof. It consists of.

As the cathode current collector 1a, a foil made of aluminum, nickel, or a material in which they are combined may be used.

As the cathode active material 1b, conventional cathode active materials that may be used in the cathode of a secondary battery in the art may be used, and non-limiting examples thereof include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O _4. _{_{, Li (Ni a Co b Mn}} c) O 2 (0 <a <1, 0 <b <1, a + b + c = 1), LiNi 1 - Y Co Y O 2, LiCo 1-Y Mn Y O ₂ , LiNi ₁ _- _Y Mn _Y O ₂ , where 0 ≦ Y <1, Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, a + b + c = _{_{_{2), LiMn 2 - Z Ni}}} Z O 4, LiMn 2 - Z Co Z O 4 ( here, there are 0 <Z <2), LiCoPO 4, LiFePO 4 , and mixtures thereof and the like.

In addition, the negative electrode 2 applied to the unit cell for a secondary battery according to an embodiment of the present invention includes a negative electrode current collector 2a and a negative electrode active material 2b laminated on the surface thereof, as shown in FIG. 4. It consists of a form.

As the negative electrode current collector 2a, a foil made of stainless steel, nickel, copper, titanium, or an alloy thereof may be used.

As the negative electrode active material 2b, conventional negative electrode active materials that may be used in the negative electrode of a secondary battery in the art may be used, and non-limiting examples thereof include carbon such as non-graphitizable carbon and 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' Al, B, P, Si, a

group

1, 2, 3 element of the periodic table, a halogen, a metal complex oxide of 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 , Oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

Meanwhile, the separator 3 interposed between the anode 1 and the cathode 2 may be implemented in a form including a porous coating layer formed on one or both sides of the porous polymer substrate.

The porous polymer substrate used for the separator 3 is not particularly limited as long as it is a porous polymer substrate having a planar shape that is usually applied to a secondary battery. Such porous polymer substrates are low density polyethylene, linear low density polyethylene, polyethylene terephthalate, high density polyethylene, propylene homopolymer, polypropylene random copolymer, poly1-butene, poly4-methyl-1-pentene, ethylene-propylene random copolymer , Ethylene 1-butene random copolymer, propylene 1-butene random copolymer, polyethylene terephthalate, polybutylene terephthalate, polyester, polyacetal, polyamide ( polyamide, polycarbonate, polyimide, polyetheretherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole polybenzimidazole, polyethersulfone, polyphenylenoxide eoxide), cyclic olefin copolymer (cyclic olefin copolymer), polyphenylenesulfide (polyphenylenesulfide) and polyethylenenaphthalene (polyethylenenaphthalene) may be formed from one or two or more mixtures selected from the group consisting of. The porous polymer substrate may be in the form of a film or nonwoven fabric.

The porous coating layer is formed on one side or both sides of the porous polymer substrate, the inorganic particles are connected and fixed by the binder polymer for the porous coating layer, the micro-pores due to the interstitial volume between the inorganic particles Formed.

The binder polymer for the porous coating layer is excellent in binding strength with inorganic particles, and is not particularly limited as long as it is a component that is not easily dissolved by the electrolyte solution. Non-limiting examples of compounds usable as binder polymers for porous coating layers include polyvinylidene fluoride-co-hexafluoro propylene (PVDF-co-HFP), polyvinylidene fluoride-trichloroethylene ( polyvinylidene fluoride-co-trichloro ethylene, polyvinylidene fluoride-co-chlorotrifluoro ethylene, polymethyl methacrylate, polyacrylonitrile, polyvinyl Pyrrolidone (polyvinylpyrrolidone), polyvinylacetate, ethylene vinyl acetate copolymer (polyethylene-co-vinyl acetate), polyethylene oxide, cellulose acetate, cellulose acetate butyrate ), Cellulose acetate propionate tate propionate, cyanoethylpullulan, cyanoethylpolyvinylalcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxyl methyl Carboxyl methyl cellulose (CMC), acrylonitrile-styrene-butadiene copolymer, polyimide, polyvinylidenefluoride, polyacrylonitrile and It may be one or a mixture of two or more selected from the group consisting of styrene butadiene rubber (SBR).

On the other hand, the secondary cell unit cell according to an embodiment of the present invention, at the interface between the positive electrode 1 and the separator 3 and / or the interface between the negative electrode 2 and the separator 3 is formed with the same adhesive force as a whole It has no patterned adhesion. In other words, the interface between the

electrodes

1 and 2 and the separator 3 has different adhesive strengths for each region, and thus the adhesion between the

electrodes

1 and 2 and the separator 3 differs for each region. The method will be described in more detail with reference to FIGS. 5 and 6 below.

Next, a manufacturing process of a unit cell according to an embodiment of the present invention will be described with reference to FIGS. 5 to 7.

FIG. 5 is a schematic view showing a facility for manufacturing a unit cell for a secondary battery according to the present invention, FIG. 6 is a view showing a plasma processing apparatus used for manufacturing a unit cell for a secondary battery according to an embodiment of the present invention. FIG. 6 is a diagram illustrating a mask applied to the plasma processing apparatus illustrated in FIG. 6.

First, referring to FIG. 5, in the manufacturing process of a unit cell according to an exemplary embodiment of the present disclosure, supplying a central electrode P1, supplying separators S1 and S2, and performing a plasma treatment may be performed. Supplying an upper electrode P2 and a lower electrode P3, and lamination.

The supplying of the center electrode P1 is a step of supplying the central electrode P1 having a long fabric shape wound on the center electrode supply roll 11.

The separator (S1, S2) supply step is a step of supplying the separation membrane (S1, S2) of the long fabric shape wound on each of the separator supply roll (12, 13) on both sides of the central electrode (P1).

In the plasma treatment step, plasma treatment is performed on the surfaces of the separation membranes S1 and S2 by using the plasma processing apparatus 16 to modify the surfaces of the separation membranes S1 and S2 and the electrodes P1, P2 and P3. A step of performing a patterned plasma treatment to increase the adhesive strength of the separator, but to prevent the plasma treatment is performed on a portion of the surface of the separators S1 and S2 and the plasma treatment is not performed on the remaining regions.

The supplying of the upper electrode P2 and the lower electrode P3 is performed by using the electrode supply rolls 12 and 13 on the separation membranes S1 and S2 on which plasma treatment is performed, and forming the upper electrode P2 and the lower fabric. It is a step of supplying the electrode P3.

The lamination step may include a lower electrode (P2), a separator (S2), a center electrode (P1), a separator (S1), and an upper electrode (P1), which are sequentially stacked from the lower layer. Lamination is performed to bond the membrane interface. The lamination step may include a heating step of applying heat using the heater 17 on the upper electrode P2 and the lower electrode P3 disposed on the separators S1 and S2, and the upper electrode P2 and the lower part of the applied heat. And compressing the electrodes between the electrodes and the separator by applying pressure using the lamination rolls 18 on the electrodes P3.

Meanwhile, in the manufacturing process of the unit cell for secondary batteries, each of the supplied central electrodes P1, P2, P3 and the separators S1, S2 may be previously cut using the

cutters

19, 20, 21, and 22. The method may further include cutting to a predetermined length.

In addition, although not shown in the drawings, the manufacturing process of the unit cell for secondary batteries may further include inspecting and discharging the secondary cell unit cells completed by lamination.

Here, the inspection of the unit cell means an inspection of whether foreign matter exists between the electrode and the separation membrane, whether the unit cell is made to the correct size, or the like, in the lamination process for manufacturing the unit cell.

Meanwhile, referring to FIGS. 6 and 7, the configuration of the plasma processing apparatus is shown in more detail. That is, referring to FIG. 6, the plasma processing apparatus applied to the present invention includes a power supply unit 16a and an electrode unit 16b, and a patterned plasma is formed between the electrode unit 16b and the separator S1. A mask M is provided that is applied to perform the process.

Referring to FIGS. 6 and 7, the mask M passes through a plasma treatment in order to prevent a plasma treatment of a portion of the surface of the separation film S1 and a plasma treatment of the remaining regions. It is composed of a first region (M1) that can be made and a second region (M2) that can not pass through the plasma.

That is, while the separation membrane S1 faces the surface of the first region M1 during the plasma treatment, the surface of the separation membrane S1 is strongly modified with the electrode during the lamination by performing surface modification by the plasma treatment. The portion facing the second region is not subjected to plasma treatment, and thus relatively weakly adheres to the electrode during lamination. However, the pattern of the mask M shown in FIG. 7 is merely exemplary, and the pattern of the mask M for realizing a patterned adhesive force may be variously formed.

As described above, the interface between the separator S1 subjected to the plasma treatment using the mask M and the electrode includes a region where the adhesive force is strong and a region where the adhesive force is relatively weak. In manufacturing a secondary battery using a unit cell, an electrolyte is filled together with a unit cell in the case. The unit cell according to the exemplary embodiment of the present invention has a region in which adhesion strength between the separator and the electrode is relatively weak, and thus the adhesion strength is increased. Impregnation of the electrolyte through the weak area can be made quickly, thereby bringing about an improvement in the performance of the secondary battery.

On the other hand, the manufacturing conditions of the unit cell for a secondary battery according to the present invention are as follows:

(One). (Membrane information used):

SRS separator (composition: PVDF + Al ₂ O ₂ ) manufactured using PP fabric is used.

(2). (Plasma treatment conditions):

Plasma treatment is performed at 2-4.5 kV, 10-30 kHz.

(3). (Experimental method to demonstrate the effect of plasma treatment):

Compare the height of the wetted area with electrolyte by position in a state in which the prepared bicell is immersed in the electrolyte by a predetermined depth (5 mm or less).

8 and 9, the conventional secondary cell unit cells (FIG. 8) and the secondary cell unit cells (FIG. 9) according to an embodiment of the present invention may have a wettability with respect to an electrolyte. It can be seen that there is a big difference.

That is, in the electrolyte solution impregnation experiment using a conventional unit cell, electrolyte impregnation occurred at a height of approximately 5.5 to 6.0 mm from the bottom (FIG. 8), whereas in the electrolyte solution impregnation experiment using the unit cell according to an embodiment of the present invention, It can be seen that the area where the electrolyte impregnation occurred and the region where the electrolyte impregnation occurred to a much higher region (approximately 18 to 26 mm from the bottom) coexist with the height of approximately 6 mm.

As such, the region in which the electrolyte solution is impregnated to a higher region corresponds to a region in which the adhesion of the electrode / separation membrane is relatively lower than the surroundings because plasma treatment is not performed due to masking during plasma treatment.

That is, the adhesion between materials can be classified into chemical adhesion and mechanical interlocking. The improvement of adhesion by plasma treatment as in the present invention is a phenomenon caused by enhanced chemical adhesion. Types of chemical adhesion include electrostatic attraction, chemical absorption, chemical bonding, and the like. When plasma treatment is performed on a part of the surface of the separator as in the present invention, plasma treatment is performed. For example, the electrostatic attraction and chemical properties are due to the surface modification such as bonding structure such as CH, C = C, CC to bonding structure such as CO, C = O, OCO, OC = O. Chemical Absorption, Chemical Bonding, etc. are strengthened. On the other hand, in the region where the plasma treatment is not performed, the adhesive strength is relatively low, so that the impregnation of the electrolyte in the region is improved.

Although the present invention has been described above by means of limited embodiments and drawings, the present invention is not limited thereto and will be described below by the person skilled in the art to which the present invention pertains. Of course, various modifications and variations are possible within the scope of the claims.

Claims

A central electrode having a first polarity;

A pair of separators each laminated on both surfaces of the center electrode; And

An upper electrode and a lower electrode each laminated on the pair of separators and having a second polarity;

Including;

The separator is a secondary cell unit cell having a patterned adhesive force.
The method of claim 1,

The separator,

A first region having a first adhesive force; And

A second region having an adhesive force lower than the first adhesive force;

Unit cell for a secondary battery comprising a.
The method of claim 2,

Wherein the first region is a plasma treated region and the second region is a region not subjected to plasma treatment.
Supplying a central electrode;

Supplying separators on both sides of the center electrode;

Treating plasma on the surface of the separator, but performing plasma treatment on a portion of the separator and preventing plasma treatment on the remaining region;

Supplying an upper electrode and a lower electrode on the separator; And

Performing lamination so that each of the center electrode, the upper electrode, and the lower electrode is adhered to the separator;

Method for manufacturing a unit cell for a secondary battery comprising a.
The method of claim 4, wherein

Performing the lamination is,

Applying heat on the upper and lower electrodes; And

Compressing by applying pressure on the heated upper and lower electrodes;

Method for producing a unit cell for a secondary battery comprising a.
The method of claim 3,

The manufacturing method of the unit cell for secondary batteries,

And cutting each of the supplied central electrode, upper electrode, lower electrode, and separator into a predetermined length.
The method of claim 3,

The manufacturing method of the unit cell for secondary batteries,

The method of manufacturing a unit cell for a secondary battery, characterized in that it further comprises the step of inspecting and discharging the unit cell for a secondary battery is completed lamination.