KR101313070B1 - A case for lithium secondary battery and lithium secondary battery comprising the same - Google Patents

Abstract

The present invention relates to a lithium secondary battery case and a lithium secondary battery comprising the same. The lithium secondary battery case of the present invention is an electrolyte storage portion formed of an inner wall of a battery case and a polymer thin film adhered to the inner wall, wherein the polymer thin film is attached to a predetermined portion of the battery case inner wall as an adhesive portion, An electrolyte storage unit having a sealed inner space of a predetermined volume between a battery case inner wall and the polymer thin film; And a battery case for a lithium secondary battery having an electrolyte stored in the electrolyte storage unit, wherein the electrolyte storage unit is destroyed by the internal pressure of the battery increased during charging and discharging of the lithium secondary battery. . The lithium secondary battery case of the present invention can improve the battery life by maintaining the cycle performance of the battery by enabling additional replenishment of the electrolyte during operation of the battery.

Description

Case for lithium secondary battery and lithium secondary battery comprising same {A CASE FOR LITHIUM SECONDARY BATTERY AND LITHIUM SECONDARY BATTERY COMPRISING THE SAME}

The present invention relates to a lithium secondary battery case and a lithium secondary battery including the same, and more particularly, to a lithium secondary battery case and a lithium secondary battery including the same, which can maintain a cycle performance of a battery for a long time.

Recently, interest in energy storage technology is increasing. As the application fields of cell phones, camcorders, notebook PCs, and electric vehicles further expand, there is a growing demand for higher energy density of batteries used as power sources for such electronic devices. Lithium secondary batteries are the ones that can best meet these demands, and researches on them are actively under way.

Among the secondary batteries currently applied, lithium secondary batteries developed in the early 1990's include lithium salts dissolved in an appropriate amount of a negative electrode such as a carbon material capable of occluding and releasing lithium ions, a positive electrode made of lithium-containing oxide, and a mixed organic solvent. The nonaqueous electrolyte is prepared to be provided in the battery case.

Organic solvents currently widely used in nonaqueous electrolytes include ethylene carbonate, propylene carbonate, dimethoxyethane, gamma butyrolactone, N, N-dimethylformamide, tetrahydrofuran or acetonitrile.

However, these organic solvents generally have a problem in that gas is generated inside the battery due to decomposition of the organic solvent and / or side reaction between the organic solvent and the electrode during charging and discharging, thereby expanding the thickness of the battery. Thus, the amount of gas generated is further increased.

This continuously generated gas causes an increase in the internal pressure of the battery, which causes the center of the specific surface of the battery to deform such as swelling of the square battery in a specific direction, as well as a local difference in adhesion at the electrode surface of the battery. This causes the problem that the electrode reaction does not occur equally in the entire electrode surface. In addition, since the gas generation is due to the loss of the electrolyte, the increase in the internal pressure due to the generation of the gas means that the loss of the electrolyte is large. As a result, battery performance and safety deterioration are necessarily caused.

In order to solve this problem, various attempts have been made, such as adjusting the composition of the electrolyte or adding an additive to the electrolyte.

However, the above studies are only to suppress or slow down the decomposition of the electrolyte, and it is known that no solution that can prevent the decomposition of the electrolyte itself has not been reported.

Accordingly, an object of the present invention is to provide a lithium secondary battery case and a lithium secondary battery including the same, which can additionally replenish the electrolyte during operation of the battery as a new solution for the loss of the electrolyte due to the decomposition of the electrolyte.

In order to solve the above problems, the lithium secondary battery case of the present invention is an electrolyte storage unit formed of a polymer thin film attached to the inner wall and the inner wall of the battery case, the polymer thin film is a predetermined portion is attached to the inner wall of the battery case as an adhesive portion; An electrolyte storage unit having a predetermined volume of a sealed inner space between the battery case inner wall and the polymer thin film by the adhesive unit; And a battery case for a lithium secondary battery having an electrolyte stored in the electrolyte storage unit, wherein the electrolyte storage unit is destroyed by the internal pressure of the battery increased during charging and discharging of the lithium secondary battery. .

The lithium secondary battery case of the present invention can prevent the degradation of the battery due to the decomposition of the electrolyte by enabling additional electrolyte replenishment during use of the battery, the electrolyte replenishment mechanism is the pressure inside the battery increases with the use of the battery It does not require a separate device because it uses. In addition, since the composition and the components of the electrolyte used are irrelevant, the problem of electrolyte decomposition is solved in a completely different manner from the prior art.

The polymer thin film that may be used in the lithium secondary battery case of the present invention may be manufactured using polyethylene, polypropylene, or a copolymer thereof, but is not limited thereto.

The lithium secondary battery case of the present invention comprises an electrode structure including a positive electrode, a negative electrode and a separator interposed between the positive and negative electrodes in the case; And it can be used in the manufacture of a lithium secondary battery by providing an electrolyte therein.

The lithium secondary battery case of the present invention can improve the battery life by preventing the degradation of the cycle performance due to the loss of the electrolyte by enabling additional replenishment of the electrolyte during use of the battery.

BRIEF DESCRIPTION OF THE DRAWINGS The accompanying drawings, which are incorporated in and constitute a part of the specification, illustrate exemplary embodiments of the invention and, together with the description of the invention, It should not be construed as limited.
1 is a cross-sectional view schematically illustrating a battery case in which an electrolyte storage unit is formed on an inner wall according to the present invention.
2 is a cross-sectional view schematically illustrating a battery case in which a plurality of electrolyte storage portions are formed on an inner wall according to the present invention.
3 is a plan view schematically illustrating a battery case in which a plurality of electrolyte storage portions are formed on an inner wall according to the present invention.

Hereinafter, the present invention will be described in detail with reference to the drawings. The terms and words used in the present specification and claims should not be construed as limited to ordinary or dictionary terms and the inventor may appropriately define the concept of the term in order to best describe its invention It should be construed as meaning and concept consistent with the technical idea of the present invention.

1 schematically shows an embodiment of a battery case 10 according to the present invention. It should be noted, however, that the embodiments shown in the following description and the configurations shown in the drawings are only the most preferred embodiments of the present invention and do not represent all the technical ideas of the present invention. Therefore, It should be understood that various equivalents and modifications may be present.

As shown in FIG. 1, the battery case 10 of the present invention includes an electrolyte storage unit 12 formed of an inner wall 11 and a polymer thin film 13 of the battery case. A portion of the polymer thin film 13 is attached to the inner wall 11 of the case as an adhesive portion 15, so that the inner space 14 is defined and the inner space 14 is sealed.

The shape of the electrolyte storage portion 12 is determined by the attachment form of the adhesive portion 15. Only one electrolyte storage part 12 may be formed on one surface of the battery case inner wall 11 in a planar shape, may be formed in a plurality of lines, or may be formed in a plurality of microcapsules. . 2 and 3 illustrate another embodiment of the battery case 10 of the present invention in which a plurality of electrolyte storage portions 12 are formed. FIG. 2 is a cross-sectional view illustrating a cross section in which a plurality of electrolyte storage units 12 are formed, and FIG. 3 illustrates a plurality of electrolyte storage units 12 formed in a lattice form in a microcapsule form.

The electrolyte storage unit 12 according to the present invention may store the electrolyte in the internal space 14. The method for storing a predetermined solution in the polymer thin film or inside the microcapsules formed of the polymer thin film may use any known technique without limitation. For example, Japanese Patent Application Laid-Open No. 1994-340168 discloses a method of storing a colorant in the microcapsule. have.

The present invention is characterized in that the sealed state forming the electrolyte storage portion 12 is destroyed by the internal pressure of the battery. Specifically, as the lithium secondary battery is repeatedly charged and discharged, the electrolyte is decomposed and lost. Disappearance of the electrolyte degrades the ability of the ions to move, leading to a decrease in battery performance. On the other hand, the decomposed electrolyte is generated as a gas component, and the generated gas causes an increase in the pressure inside the battery.

The present invention contemplates that loss of electrolyte results in an increase in the cell internal pressure, thereby providing a system for replenishing the lost electrolyte using increased internal pressure. That is, the polymer thin film 13 or the adhesive portion 15 according to the present invention is designed and formed to be destroyed by the increased pressure inside the battery. Specifically, when the thickness of the polymer thin film 13 and the degree of adhesion of the adhesive part 15 are adjusted according to the type of battery used and the range in which the internal pressure of the battery can reach, the electrolyte storage part 12 is applied to a predetermined internal pressure. It can be manufactured to be destroyed. When the sealed state of the internal space of the electrolyte storage unit 12 is broken, the electrolyte stored in the internal space is released to replenish the lost electrolyte, and the performance of the battery can be excellently maintained for a long time.

In addition, the polymer forming the polymer thin film 13 is not limited as long as the polymer may have a thin film form. For example, a polymer such as polyethylene, polypropylene, or a copolymer thereof may be used.

The electrolyte stored in the electrolyte storage unit 12 of the present invention is preferably the same or similar to the electrolyte used between the positive electrode and the negative electrode inside the battery. Typically, the electrolyte for a lithium secondary battery includes a lithium salt and an organic solvent. The electrolyte stored in the electrolyte storage unit 12 according to the present invention may store a lithium salt and an organic solvent, or may store only an organic solvent.

Lithium salt that can be included as an electrolyte in the electrolyte stored in the electrolyte storage unit 12 according to the present invention can be used without limitation those conventionally used in the electrolyte for lithium secondary batteries, for example, F ^{− , Cl -, Br -, I} -, NO 3 -, N (CN) 2 -, BF 4 -, ClO 4 -, PF 6 -, (CF 3) 2 PF 4 -, (CF 3) 3 PF 3 - _{, (CF 3) 4 PF 2} -, (CF 3) 5 PF -, (CF 3) 6 P -, CF 3 SO 3 -, CF 3 CF 2 SO 3 -, (CF 3 SO 2) 2 N -, _{^{(FSO 2) 2 N -,}} CF 3 CF 2 (CF 3) 2 CO -, (CF 3 SO 2) 2 CH -, (SF 5) 3 C -, (CF 3 SO 2) 3 C -, CF 3 ^{_{(CF 2) 7 SO 3 -}} , CF 3 CO 2 -, CH 3 CO 2 -, SCN ^- and (CF ₃ CF ₂ SO ₂ ) ₂ N ^- .

As the organic solvent included in the electrolyte stored in the electrolyte storage unit 12 according to the present invention, those conventionally used in the electrolyte for lithium secondary batteries may be used without limitation, and typically propylene carbonate (PC), ethylene carbonate (ethylene carbonate, EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethylsulfuroxide, acetonitrile, dimethoxy Ethylene, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, tetrahydrofuran, any one selected from the group consisting of, or a mixture of two or more thereof may be representatively used. In particular, ethylene carbonate and propylene carbonate, which are cyclic carbonates in the carbonate-based organic solvent, can be preferably used because they have high permittivity as a high-viscosity organic solvent and dissociate the lithium salt in the electrolyte well. In this cyclic carbonate, dimethyl carbonate and diethyl When a low viscosity, low dielectric constant linear carbonate such as carbonate is mixed in an appropriate ratio, an electrolyte having a high electric conductivity can be prepared, and thus it can be more preferably used.

Alternatively, the electrolytic solution stored in accordance with the present invention may further include an additive such as an overcharge inhibitor or the like contained in an ordinary electrolytic solution.

The battery case 10 used in the present invention may be adopted that is commonly used in the art, there is no limitation on the appearance according to the use of the battery, for example, cylindrical, square, pouch using a can It may be a type or coin (coin) and the like.

The battery case 10 of the present invention houses an electrode structure composed of a lithium secondary battery positive electrode, a negative electrode and a separator interposed between the positive electrode and the negative electrode commonly used in the art, and the electrolyte is injected into a lithium secondary battery.

As a specific example, a lithium-containing transition metal oxide may be preferably used as the cathode active material, for example, 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, 0 <c <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 (O ≦ y <1), Li (Ni _a Co _b Mn _c ) O ₄ (0 <a <2, 0 <b <2, 0 <c <2, a + b + c = 2), LiMn _{2 - z Ni z O 4, LiMn} 2 -z Co z O 4 (0 <z <2), LiCoPO may be used any one or a mixture of two or more of these _four and is selected from the group consisting of LiFePO _4. In addition to these oxides, sulfide, selenide and halide may also be used.

As the negative electrode active material, a carbon material, lithium metal, silicon, tin, or the like, which can normally occlude and release lithium ions, may be used, and a metal oxide such as TiO ₂ and SnO ₂ having a potential of less than ₂ V may be used. Preferably, carbon materials can be used, and carbon materials such as low-crystalline carbon and highly-crystalline carbon can be used. Soft crystalline carbon and hard carbon are typical low crystalline carbon, and high crystalline carbon is natural graphite, Kish graphite, pyrolytic carbon, liquid crystal pitch-based carbon fiber. High temperature calcined carbon such as (mesophase pitch based carbon fiber), meso-carbon microbeads, Mesophase pitches and petroleum or coal tar pitch derived cokes. In this case, the negative electrode may include a binder, and the binder may include vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride, polyacrylonitrile, Various kinds of binder polymers such as polymethylmethacrylate may be used.

As the separator, a conventional porous polymer film conventionally used as a separator, for example, a polyolefin such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer and an ethylene / methacrylate copolymer A porous polymer film made of a high molecular weight polymer may be used alone or in a laminated manner, or a nonwoven fabric made of a conventional porous nonwoven fabric such as a glass fiber having a high melting point, a polyethylene terephthalate fiber or the like may be used. It is not.

According to the present invention, the lithium secondary battery electrolyte injected into the battery case together with the electrode structure includes a lithium salt and an organic solvent, and the lithium salt and the organic solvent are lithium salt stored in the electrolyte storage unit according to the present invention. It may be the same or similar to the organic solvent.

In the above, in order to demonstrate this invention concretely, it demonstrated the Example in detail. However, embodiments according to the present invention can be modified in many different forms, and the scope of the present invention should not be construed as being limited to the above-described embodiments.

Claims (5)

An electrolyte storage portion formed of an inner wall of a battery case and a polymer thin film attached to the inner wall, wherein the polymer thin film is attached to a portion of the battery case inner wall as an adhesive part, and is formed between the inner surface of the battery case and the polymer thin film by the adhesive part. An electrolyte storage unit having a predetermined volume of a sealed inner space; And
Electrolyte solution stored in the electrolyte storage unit
A battery case for a lithium secondary battery, comprising: the electrolyte storage unit is a lithium secondary battery case, characterized in that the sealed state of the internal space is destroyed by the internal pressure of the battery increases during the charge and discharge of the lithium secondary battery. The method of claim 1,
The polymer thin film is a lithium secondary battery case, characterized in that made of a polymer selected from the group consisting of polyethylene, polypropylene-based and copolymers thereof. The method of claim 1,
The electrolyte stored in the electrolyte storage unit is propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, dipropyl carbonate, dimethylsulfuroxide, acetonitrile, dimethoxyethane, diethoxyethane, vinyl A case for a lithium secondary battery comprising any one or a mixture of two or more thereof selected from the group consisting of ethylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran. The method of claim 1,
The battery case is a lithium secondary battery case, characterized in that the cylindrical, square, pouch type or coin type. In a lithium secondary battery in which a positive electrode, a negative electrode, a separator, and an electrolyte solution are contained in a battery case,
The battery case is a lithium secondary battery, characterized in that the battery case of any one of claims 1 to 4.

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