KR100571256B1 - Lithium Ion Polymer Battery and Manufacturing Method Thereof - Google Patents

Abstract

Disclosed are a lithium ion polymer battery and a method of manufacturing the same.

The battery of the present invention is a lithium ion polymer battery in which a positive electrode having a polymer component, a separator for both electrolytes, and a negative electrode form an integrated electrode assembly by laminating, wherein each of the negative electrode, the separator, and the positive electrode includes a polyol-based plasticizer. Characterized in that the polyol-based plasticizer is preferably contained 2 to 20% by mass.

 Therefore, compared to the prior art, while maintaining a high adhesion between the electrode and the separator in the electrode assembly formed integrally, the process can be simplified to increase the efficiency of the process, the battery material cost can be reduced and the electrical capacity can be increased.

Description

Lithium ion polymer battery and manufacturing method thereof

1 is a partial process explanatory diagram schematically showing a method of forming an electrode and a separator into an integrated electrode assembly in a belcore manner;

2 is an explanatory diagram conceptually illustrating features of a manufacturing process of a lithium ion polymer battery according to an embodiment of the present invention;

3 is a structural diagram schematically showing the detailed structure of each electrode and separator according to the lithium ion polymer battery of the present invention.

* Explanation of symbols for the main parts of the drawings

10,100: cathode 11,31,110,310: electrode plate

13,33,130,330: electrode current collector 20,200: separator

30,300 anode 40,400 electrode assembly

50: extraction solvent 60, 600: electrolyte

113: binder 115: plasticizer

The present invention relates to a lithium ion polymer battery (PLI battery: Plastic Lithium Ion Battery, Lithium Ion Polymer Battery) and a method of manufacturing the same, and more particularly, to a lithium ion polymer battery and its manufacturing method characterized by the configuration of each electrode will be.

Lithium is a suitable material for manufacturing a battery having a small atomic weight of the element itself and a large electric capacity per unit mass. Therefore, a lithium secondary battery using a lithium metal, a material such as carbon capable of lithium intercalation, as a cathode, and a lithium composite oxide such as lithium cobalt or lithium manganate, which can also pass in and out of lithium ions, as a cathode. The research and development of is continued.

On the other hand, since lithium reacts violently with moisture, a non-aqueous electrolyte is used in a lithium battery. In this case, since it is not affected by the electrolysis voltage of water, the lithium-based battery has an advantage of generating an electromotive force of about 3 to 4 volts.

The non-aqueous electrolyte used in the lithium secondary battery is largely a liquid electrolyte and a solid electrolyte. Liquid electrolytes are usually used in lithium ion batteries and dissociate lithium salts into organic solvents. As the organic solvent, ethylene carbonate, propylene carbonate or other alkyl group-containing carbonates or similar organic compounds can be used. Practical at room temperature as a solid electrolyte is usually made of a polymer and can be used in lithium ion polymer batteries and lithium metal polymer batteries. In this case, a lithium ion polymer battery generally refers to a battery using a polymer in an electrolyte serving as a separator or a polymer in forming an electrode, particularly an anode.

On the other hand, depending on the type of the polymer electrolyte, the lithium ion polymer battery may be divided into a fully solid intrinsic lithium ion polymer battery containing no organic electrolyte at all and a gel type lithium ion polymer battery containing the organic electrolyte. . A fully solid lithium ion polymer battery has a problem of very low ionic conductivity compared to a liquid electrolyte, and a gel type lithium ion polymer battery can be implemented in various forms. When many plasticizers are used to increase the ionic conductivity, the mechanical strength and the film thickness are reduced. Difficulty of control is a problem.

In addition, the positive and negative electrodes repeat expansion and contraction during charging and discharging. In this process, the adhesion between the layers of the positive electrode, the negative electrode, and the electrolyte and separator may decrease. Degradation of the interlayer adhesion may cause a problem in the movement of lithium ions and increase the internal resistance may lead to deterioration of battery characteristics and malfunction.

One typical method of the conventional lithium ion polymer battery is the Bellcore method proposed by Bell comunication research Inc. An example of this approach is described in US Pat. No. 5456000 and the like. According to this method, the binder and separator of the positive and negative electrodes of the battery are composed of a copolymer of vinylidene fluoride (VDF) and hexafluoropropylene (HFP) (P (VDF-HFP)) to improve the adhesion between the layers of the electrode assembly. You can see the improvement.

1 is a process explanatory diagram schematically showing a method of forming an electrode and a separator as an integrated electrode assembly in a belcore manner.

Referring to FIG. 1, a more detailed description of a bel-core lithium ion polymer battery is described below. First, in order to form the separator 20, this copolymer is mixed with plasticizer DBP (Dibutyl Phthalate), silica particles, and acetone with a solvent, and then the temperature is increased. To dissolve the copolymer. This is cast to a glass plate in a cast manner and dried to remove the solvent to obtain a separator 20 film.

In order to form the electrodes 10 and 30, the copolymer (P (VDF-HFP)), the plasticizer DBP, the conductive aid, the lithium cobalt acid (LiCoO ₂ ), and the solvent, similarly to the separator 20 are formed. Acetone is mixed, molded by coating, and dried to obtain electrode films 11 and 31. The electrodes 10 and 30 are formed by stacking the electrode films 11 and 31 on sandwiched surfaces of the electrode dust collectors with the center electrode current collectors 13 and 33 onto a sandwich and heating and welding them through a roller. The electrode current collectors 13 and 33 use a mesh-type aluminum or copper grid depending on the polarity.

As each electrode (10,30) is formed, the electrode assembly (10) through the lamination (lamination) by laminating the negative electrode 10 and the positive electrode 30 on both sides of the sandwich 20 in the center of the sandwich (rolling) to form a integrated electrode assembly ( 40) is formed. DBP is extracted by dipping the electrode assembly 40 consisting of the negative electrode 10, the positive electrode 30, and the separator 20 containing DBP in an extraction solvent 50 which can elute plasticizers such as diethyl ether and methanol. (extraction) Thus, the positive electrode, the negative electrode, and the separator each become a microporous membrane. The electrode assembly made of a microporous membrane is impregnated with a separate electrolyte 60 and sealed with a pouch. Alternatively, once the pouch film is placed, the electrolyte is injected to allow the electrode and the separator to absorb the electrolyte, and then the pouch is sealed.

However, in the above Belcoa type lithium ion polymer battery, an electrode film and a separator film containing DBP are formed once to form an electrode and a gel electrolyte separator, and then the DBP extraction process is performed on these films to impregnate the electrolyte solution. There are a few steps to getting it done. In addition, the process of forming an electrode assembly in which the negative electrode, the separator, and the positive electrode are integrally laminated through heat rolling, and the process of removing the plasticizer DBP therein cannot be performed in a consistent manner, thus reducing the efficiency of the process. There was a problem that the probability of defects also increased.

In particular, the use of a mesh-type aluminum grid, which is difficult to process with a positive electrode current collector, is used to remove the DBP above a certain thickness, thereby increasing the manufacturing cost of the battery. .

The present invention is to eliminate the above-mentioned problems, the process is simplified while maintaining a high adhesion between the electrode and the separator in the electrode assembly formed integrally through the lamination process, compared to the conventional belcore method using DBP It is an object of the present invention to provide a lithium ion polymer battery and a method for producing the same, which can increase the efficiency of the process.

It is another object of the present invention to provide a lithium ion polymer battery and a method of manufacturing the same, which can reduce battery material cost and increase electric capacity, compared to the conventional Belcore method using DBP.

The lithium ion polymer battery of the present invention for achieving the above object,

In a lithium ion polymer battery in which a positive electrode having a polymer component, a separator having both an electrolyte, and a negative electrode form an integrated electrode assembly by laminating, the negative electrode, the separator, and the positive electrode each include a polyol-based plasticizer. .

At this time, the polyol-based plasticizer is preferably contained 2 to 20% by mass.

In the present invention, the main polymer component may include polyvinyl defluoride, which forms a polymer matrix (net structure) of the binder of the electrode and the separator, and the polyol may be a polyethylene glycol (CH ₃ − ( CH ₂ ) _n -OH), polyethylene glycol dimethyl ether (CH ₃ -O (CH ₂ CH ₂ O) _n -CH ₃ ), polyethylene glycol monomethyl ether: CH ₃ -O (CH ₂ CH ₂ O) _n -H) and the like. At this time, it is preferable to use a polyol having a molecular weight of about 200 to 1000.

In the present invention, the electrode current collector is characterized in that the positive electrode, the negative electrode both have a metal foil form. That is, it does not use a mesh form.

The lithium ion polymer battery manufacturing method of the present invention for achieving the above object,

Forming a positive electrode and a negative electrode having a binder polymer, a polyol plasticizer, and an electrode active material,

Forming a separator film comprising a polymer and a polyol plasticizer,

And forming an integrated electrode assembly by superposing an anode and a cathode on both sides of the separator film.

In the present invention, the forming of the positive electrode and the negative electrode may be performed by first forming an electrode plate including a binder polymer, a polyol plasticizer, and an electrode active material, and then laminating the electrode plate on a foil current collector.

The present invention is usually further provided with a step of impregnating a separate electrolyte solution containing a lithium salt in the electrode assembly after forming the integral electrode assembly. At this time, the step of impregnating the electrolyte is preferably made of a work consistent with the step of forming the electrode assembly.

In the present invention, the electrode and the separator is preferably formed using polyvinylidene fluoride as the polymer.

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

FIG. 2 is an explanatory diagram conceptually showing features of a manufacturing process of a lithium ion polymer battery according to an embodiment of the present invention, and FIG. 3 schematically shows a detailed structure of each electrode and separator according to the lithium ion polymer battery of the present invention. It is explanatory drawing shown by.

Referring to FIGS. 2 and 3, first, the positive electrode 300, the negative electrode 100, and the separator 200 of the battery having the structure as shown in FIG. 3 are formed. Although not shown, each electrode is a polyvinylidene fluoride (PVDF) and a polyol plasticizer polyethylene glycol dimethyl ether, the active material of each electrode, a conductive aid and a solvent are mixed to form a paste and then applied to a glass plate to apply a solvent The electrode plates 110 and 310 formed by drying may be coated on the electrode current collectors 130 and 330 through lamination, or may be directly applied and dried on metal foils that are electrode current collectors 130 and 330 of the respective electrodes 100 and 300.

In the case of forming the positive electrode, lithium cobaltate is usually used as an electrode active material, and an organic solvent such as acetone capable of dissolving polyvinylidene fluoride may be used as a solvent. In-process heating can be done to dissolve the polymer. In addition to the active material, a conductive aid may be further included to increase conductivity. In the case of the negative electrode, carbon is usually used as the electrode active material, and a separate conductive aid may not be used.

The separator 200 may be formed by mixing a polymer such as polyvinylidene fluoride, an organic solvent such as acetone, or a polyol-based plasticizer, and applying the composition to a glass plate to remove the solvent and drying the solvent. In this case, it is preferable to use the same polymer used for forming the electrode for the lamination process between the kind of the plasticizer and the mixing ratio electrode. As the constituent components of the separator, silica particles and the like can be further added. Silica may play a role of improving electrolyte retention and increasing ionic conductivity.

Polyol-based plasticizers are supplied to form about 2 to 20% by weight of the finished electrode and the separator material to form each electrode and the separator. The polyol type is polyethylene glycol and polyethylene glycol instead of polyethylene glycol dimethyl ether. Monomethyl ether and the like can be used.

The composition ratio of the polyol-based plasticizer for each film is considered such that when the polyol-based plasticizer is included in the electrode and the separator as in the present invention, the adhesive force between the electrode and the separator is sufficiently maintained so as not to cause an abnormality in internal resistance. In addition, the composition ratio of the polyol-based plasticizer in the present invention is a specific kind of plasticizer, the swelling inhibitory force at high temperatures, to ensure sufficient ionic conductivity for function when forming a film with a polymer such as polyvinylidene fluoride, mechanical strength for self-support of each film And the ease of film formation are determined.

The polyol-based plasticizer used in the present invention has a low melting point, high boiling point, high electrochemical stability and high stability in process use, and high dielectric constant as a separator and electrolyte, compared to DBPs commonly used as plasticizers. .

In the present invention, after the process of forming the electrode assembly 400, there is no DBP removal process as in the prior art, and proceeds directly to the electrolyte 600 impregnation step. Accordingly, when forming the electrodes 100 and 300, the electrode current collectors 130 and 330 do not need to use a metal grid in a mesh state that facilitates DBP removal, and are easy to manufacture and use, and use low-cost metal foils. Depending on the polarity of the battery, aluminum is usually used for the positive electrode and copper for the negative electrode.

3 shows a form in which the polyvinylidene fluoride as the binder 113 forms a polymer matrix and a polyol plasticizer 115 is distributed therebetween, and active materials in the positive electrode and the negative electrode are distributed therein. do. When impregnated with an electrolyte solution containing a high concentration of lithium salt in the post-process, the electrolyte is more rapidly diffused through the polyol-based plasticizer portion having a relatively small molecular weight than the polyvinylidene fluoride portion of the polymer, even during charge and discharge Lithium ions move faster through the plasticizer section, increasing the ionic conductivity of the entire electrolyte. For this action of the polyol plasticizer, the polyol plasticizer of the present invention preferably uses a molecular weight of about 200 to 1000.

After each electrode and the separator are formed, an electrode assembly forming step of attaching the cathode and the anode to both sides with the separator film in the center through lamination processing is performed. At this time, when passing the roller while feeding the cathode and the anode from both sides with the separator in the center, the heating is performed in the state of overlapping the sandwich to form an integrated electrode assembly while the electrode and the polymer component of the separator are fused.

Then, through an integrated process, preferably, an additional electrolyte containing 1.1% or more of a high concentration of lithium salt is further impregnated and sealed with a pouch, or once put into an open pouch film, and then injected with electrolyte to induce the electrode and separator to absorb the electrolyte. Then seal the pouch. Before and after impregnation, the integrated electrode assembly is cut to size to place in the pouch. If necessary, a process of changing the shape of the cut electrode assembly may be added.

According to the present invention, the electrode and the separator include a polyol-based plasticizer, and when forming the electrode and the separator does not have a process of forming a microporous membrane by removing the DBP as conventionally.

Therefore, the cost of using an extract such as methanol in the DBP removal process, and the cost of using a mesh type aluminum grid instead of aluminum foil as the current collector to increase the DBP removal rate when forming the anode can be eliminated.

In addition, as the DBP removal process is eliminated, the process of impregnating the electrolyte solution in the integrated electrode assembly may be easily performed, thereby reducing the process cost and lowering the defective rate.

In addition, since the mass-based composition ratio of the polyol-based plasticizer can be lowered compared to that of DBP, if a battery having the same mass as in the prior art is formed, the amount of the electrode active material can be increased to increase the electric capacity. For example, in the case of the negative electrode, the content of the electrode active material may be about 9%, and in the case of the positive electrode, the content of the electrode active material may be increased to about 3%.

In addition, since the microporous membrane structure is eliminated, there is an advantage in that the rolling ratio of the membrane is increased in comparison with the conventional microporous structure in the rolling process for increasing the area of the electrode to increase the current supply capability of the battery.

Claims (7)

In a lithium ion polymer battery having a positive electrode, an electrolytic separator, and a negative electrode having a polymer component forming an integrated electrode assembly by laminating, And each of the negative electrode, the separator, and the positive electrode contains 2 to 20% of a polyol-based plasticizer on a mass basis. The method of claim 1, The polymer component comprises a polyvinyl defluoride, The polyol-based plasticizer is polyethylene glycol (CH _3- (CH ₂ ) _n -OH), polyethylene glycol dimethyl ether (CH ₃ -O (CH ₂ CH ₂ O) _n -CH ₃ ), a lithium ion polymer battery, characterized in that one of polyethylene glycol monomethyl ether (CH ₃ -O (CH ₂ CH ₂ O) _n -H). The method of claim 2, The polyol-based plasticizer is a lithium ion polymer battery, characterized in that the material having a molecular weight of 200 to 1000. The method of claim 1, Lithium ion polymer battery, characterized in that the electrode current collector of the positive electrode made of aluminum foil. Forming a positive electrode and a negative electrode having a binder polymer, a polyol plasticizer, and an electrode active material, Forming a separator film including the polymer and the polyol plasticizer, And forming an integrated electrode assembly by overlapping the positive electrode and the negative electrode on both surfaces of the separator film, wherein the integrated electrode assembly is formed. The method of claim 5, wherein Forming the positive electrode and the negative electrode, Forming an electrode plate including the binder polymer, the polyol plasticizer, and the electrode active material; And laminating the electrode plate to a foil-type current collector. The method of claim 5, wherein And subsequently impregnating the electrode assembly with the electrolyte containing lithium salt in the electrode assembly.

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