KR20090084203A - Electrode assembly and secondary battery having the same - Google Patents

Abstract

An electrode assembly and a secondary battery including the same are provided to prevent the generation of deform when winding the electrode assembly while satisfying low-temperature discharge characteristic and overcharging property. An electrode assembly comprises a positive electrode equipped with a positive electrode active material layer; a negative electrode equipped with a negative electrode active material layer; and a porous membrane which separates the positive electrode and negative electrode and is bound by a flake type ceramic material and binder. The porous film comprises 1-10 parts by weight of an antacid agent based on 100.0 parts by weight of the ceramic materials.

Description

Electrode assembly and secondary battery having same {Electrode Assembly and Secondary Battery having the Same}

The present invention relates to an electrode assembly and a secondary battery having the same, and more particularly, to a secondary battery that suppresses battery corrosion and simultaneously satisfies low-temperature discharge characteristics and overcharge characteristics.

As miniaturization and light weight of portable electronic devices have recently advanced, the necessity for miniaturization and high capacity of batteries used as driving power sources thereof is increasing. In particular, the lithium secondary battery has an operating voltage of 3.6 V or more, which is three times higher than that of a nickel-cadmium battery or a nickel-hydrogen battery, which is widely used as a power source for portable electronic devices, and rapidly expands in terms of high energy density per unit weight. There is a trend.

Lithium secondary batteries generate electrical energy by oxidation and reduction reactions when lithium ions are intercalated / deintercalated at the positive and negative electrodes. A lithium secondary battery is prepared by using a material capable of reversibly intercalating / deintercalating lithium ions as an active material of a positive electrode and a negative electrode, and filling an organic electrolyte or a polymer electrolyte between the positive electrode and the negative electrode.

A lithium secondary battery includes an electrode assembly in which a negative electrode plate and a positive electrode plate are wound in a form such as a jelly-roll with a separator interposed therebetween, a can containing the electrode assembly and an electrolyte, and a can It consists of a cap assembly assembled on the top.

In the conventional separator, polyolefin-based microporous polymer membranes such as polypropylene and polyethylene or multiple membranes thereof are used. However, since the porous membrane layer has a sheet or film shape, internal short-circuit or overcharge The sheet-like separator also shrinks due to pore blocking of the porous membrane due to heat generation by the heat generation.

Therefore, when the sheet-like separator breaks down due to internal heat generation of the battery, the separator is reduced and the missing part is directly in contact with the positive electrode and the negative electrode, which leads to ignition, rupture, and explosion.

Therefore, in order to compensate for the above problems of the film-like separator, the ceramic material of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ) and titanium oxide (TiO ₂ ) is combined with a binder. There is an active research on ceramic separators that apply a porous membrane formed as a separator.

In this case, the ceramic separator serves to compensate for the disadvantage that the polyolefin-like film separator is melted and shrunk at a high temperature of 120 ° C. or higher. Therefore, the ceramic separator is used in combination with the conventional film-like separator and the ceramic separator.

However, when the film-like separator and the ceramic separator are used together, the cost of the material increases due to the addition of the material, and the matching between the film-like separator and the ceramic separator becomes important. In addition, since the design of the battery must be designed in consideration of not only the design but also the correlation of each separator, there is a problem in that the material, the design, and the process cost are increased.

Therefore, the existing film-like separator has a fundamental problem that is thermally vulnerable, so a method of acting as a separator with only the ceramic separator is actively devised. In this case, the ceramic layer must be denser in order to completely prevent the internal short circuit with only the ceramic separator. There is a need to do it.

However, if too close, there is a risk that high-rate charge-discharge characteristics, low-temperature characteristics, and life-span characteristics may be impaired by preventing the smooth movement of lithium ions.

Therefore, in order to replace the separator film with the ceramic layer, an optimal design is required to secure the maximum safety in a range that does not decrease the existing reliability.

Accordingly, an object of the present invention is to provide a secondary battery that satisfies all the disadvantages and problems of the prior art as described above, and simultaneously satisfies low-temperature discharge characteristics and overcharge characteristics.

The present invention is a positive electrode having a positive electrode active material layer; A negative electrode having a negative electrode active material layer; And a porous membrane which separates the positive electrode and the negative electrode and is bonded by a flake ceramic material and a binder, wherein the porous film includes an antacid, and the content of the antacid is 100 parts by weight of the ceramic material. It provides an electrode assembly, characterized in that 1 to 10 parts by weight relative to.

In addition, the present invention is an electrode including a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer, and a porous membrane formed by separating the positive electrode and the negative electrode and bonded by a flake ceramic material and a binder. Assembly; And an electrolyte solution, wherein the porous membrane includes an antacid, and the content of the antacid is 1 part by weight to 10 parts by weight with respect to 100 parts by weight of the ceramic material.

In addition, the present invention provides an electrode assembly and a secondary battery, characterized in that the antacid is at least one material selected from the group consisting of magnesium oxide, magnesium hydroxide and magnesium silicate.

In addition, the present invention is characterized in that the ceramic material is at least one material selected from the group consisting of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ) and titanium oxide (TiO ₂ ). It provides an electrode assembly and a secondary battery.

In addition, the present invention provides an electrode assembly and a secondary battery, characterized in that the width of the long diameter of the flake-shaped ceramic material particles is 100nm to 1㎛.

In addition, the present invention provides an electrode assembly and a secondary battery having the same, wherein the size of the antacid is 10 nm or more and less than the width of the long diameter of the flake ceramic material particles.

Therefore, the electrode assembly of the present invention and the secondary battery having the same have an effect of providing a secondary battery satisfying both low-temperature discharge characteristics and overcharge characteristics.

In addition, the present invention has the effect of preventing the deformation (deform) occurs when the electrode assembly is wound.

In addition, the present invention has an effect of suppressing deterioration of battery performance by corroding the metal of the battery can inner wall with a strong acid such as HF.

Details of the above object and technical configuration of the present invention and the effects thereof will be more clearly understood by the following detailed description of the present invention.

Referring to the electrode assembly including a separator of the present invention and a secondary battery having the same as follows.

The separator of the present invention is composed of a porous membrane formed by bonding a ceramic material and a binder. The paste is prepared by mixing the ceramic material and the binder in a solvent, and then the porous membrane is formed on the positive electrode, the negative electrode, or both electrodes using the paste. Can be formed.

The porous membrane may serve as a film-like separator of conventional polyethylene (PE), polypropylene (PP) and the like.

The ceramic material may be at least one material selected from the group consisting of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ), titanium oxide (TiO ₂ ), and further, zirconium, Insulating nitrides, hydroxides, ketones, or mixtures of these compounds, each of aluminum, silicon, titanium, can be used. In this case, the limitation of insulating nitride is mentioned because titanium nitride (TiN) and the like have conductivity and are not suitable for the ceramic material of the present invention.

In this case, the ceramic material in the present invention is characterized in using flake particles (flake).

Generally, the ceramic material may be manufactured in various shapes such as ball, amorphous, peanut, and lean flakes. However, the ceramic material is more dense than flake particles in the shape of fish scales than other particles, for example, spherical particles. Since a layer can be formed, in the present invention, lean flake particles are used, and the lean flake ceramic particles have an advantage of being easy to be densified because they have stronger intermolecular forces than spherical particles.

In this case, the flake ceramic particles (flake) is preferably a long diameter of 100nm to 1㎛.

The smaller the width of the particles can form a dense porous membrane layer, but if the width of the particles is too small, the cohesive force between particles due to static electricity is strong, so that uniform mixing is difficult, and in the case of an extremely dense ceramic layer, the same pores are blocked. Since the state of the lithium ion prevents the smooth movement of lithium ions, thereby reducing the reliability of the battery, it is preferable that the length of the long diameter of the lean-like ceramic particles be 100 nm or more. There is this.

In addition, the porous membrane formed by bonding the ceramic material and the binder according to the present invention is characterized in that it comprises an antacid (antiacid).

The antiacid serves to remove strong acids such as HF generated in a battery, and examples thereof include magnesium oxide, magnesium hydroxide, and magnesium silicate.

If the ceramic powder is fine, the specific surface area becomes large, which makes it easy to adsorb moisture in the air, and when the ceramic powder, which contains a lot of moisture, exists in the battery, lithium such as LiPF ₆ and LiBF ₄ in the electrolyte It reacts with salts to make strong acids such as HF, and when HF is produced, it corrodes the current collector of aluminum or copper foil and metals inside the battery can to deteriorate battery performance, and also generates O ₂ gas to rupture or explode the battery. There is a risk.

However, when the antacid is included, for example, when magnesium oxide is included, a reaction such as 2HF + MgO-> MgF ₂ + H ₂ O occurs, and the water produced by the reaction of HF and MgO is actually a crystal of MgF ₂ . Since the water becomes the same as the state where MgF ₂ is absorbed, the water-absorbed MgF ₂ is adsorbed to a part of the ceramic powder surface in a thin film state, thereby suppressing corrosion caused by conventional HF and preventing battery performance from deteriorating. In addition, O ₂ O ₂ by suppressing the generation of gas The risk of battery rupture or explosion due to gas can be prevented.

In addition, since the portion in which the antacid such as MgO was present in the porous membrane is changed to pores by the above-described reaction, the porous membrane made of the ceramic material of the lean piece particles maintains the insulation and the pores of the separator. It has a function, and therefore the movement of lithium ions becomes more smooth.

At this time, the size of the antacid is preferably 10nm or more in order to form a pore (pore) that contributes to battery performance, it is preferably less than the width of the long diameter of the lean piece particles.

In addition, the content of the antacid is preferably added in an amount of 1 to 10 parts by weight based on 100 parts by weight of the lean piece ceramic particles.

When the content of the antacid is added less than 1 part by weight, the antacid effect and the pore-forming effect is inadequate, and the ceramic layer is too dense so that lithium ions cannot move smoothly at low temperatures, and thus low temperature discharge characteristics are not good. When the amount exceeds 10 parts by weight, the mixing dispersibility is not good, so that the coating thickness of the ceramic layer cannot be uniform, and when rolled with jelly roll, deform occurs.

The binder may be a synthetic rubber latex binder or an acrylic rubber having a crosslinked structure.

The synthetic rubber latex binder is styrene butadiene rubber (SBR) latex, nitrile butadiene rubber (NBR) latex, methyl methacrylate butadiene rubber latex, chloroprene rubber latex, carboxy modified styrene butadiene rubber latex and modified polyorganosiloxane polymer latex. It may include one or more selected from the group consisting of. It is preferable that the polymer latex is made of an aqueous dispersion, and the content thereof is preferably used in an amount of 0.1 to 20 parts by weight based on 100 parts by weight of the electrode active material, and when it is less than 0.1 parts by weight, good adhesion to a current collector or the like may not be obtained. There is a concern, and when it exceeds 20 parts by weight, it is not preferable because it may adversely affect the battery characteristics.

In addition, the acrylic rubber having the crosslinked structure may be formed by the crosslinking reaction of the polymer or copolymer of the acrylic main monomer with the crosslinkable comonomer. If only one type of polymer or copolymer of acrylic main monomer is used, the bonding structure is weak and easy to break. Combined with the structure, you can create a more rigid net structure. The polymer having such a net structure is less likely to swell in a solvent as the degree of crosslinking increases. The acrylic rubber binder having the crosslinking structure may have a three-dimensional crosslinking structure having 2 to 10 crosslinking points, preferably 4 to 5 crosslinking points, for 10,000 molecular weight units of the main chain molecule. Therefore, the acrylic rubber having a crosslinked structure of the present invention may have expansion resistance that does not swell when the electrolyte solution is moistened.

Due to the inherent characteristics of ceramic materials, acrylic rubber binders having a crosslinked structure having a decomposition temperature of 1000 ° C. or higher and a decomposition temperature of 250 ° C. or higher are used, thereby obtaining a battery having high heat resistance and increasing stability against internal short circuits. .

The acrylic main monomers are methoxymethyl acrylate, methoxyethyl acrylate, (methoxyethyl acrylate), ethoxyethyl acrylate, butoxyethyl acrylate, methoxyethoxyethyl Alkoxyalkyl acrylate selected from methoxyethoxyethyl acrylate and dicyclopentenyloxyethyl acrylate; Vinyl methacrylate, vinyl acrylate, allyl methacrylate, 1,1-dimethylpropenyl methacrylate, 1,1-dimethacrylate 1,1-dimethylpropenyl acrylate, 3,3-dimethylbutenyl methacrylate, 3,3-dimethylbutenyl acrylate Alkenyl acrylate or alkenyl methacrylate selected from among; Unsaturated dicarboxylic acid esters selected from divinyl itaconate and divinyl maleate; Vinyl group-containing ethers selected from vinyl 1,1-dimethylpropenyl ether and vinyl 3,3-dimethylbutenyl ether; 1-acryloyloxy-1-phenylethene; And methyl methacrylate (methyl methacrylate) may be used one or more selected from the group consisting of.

The crosslinkable comonomers include 2-ethylhexyl acrylate, 2-methylhexyl acrylate, methyl acrylate, ethyl acrylate, propyl acrylate, and butyl acrylate. ), An alkyl acrylate selected from octyl acrylate and isooctyl acrylate; an alkyl selected from vinyl chloroacetate and acryl chloroacetate. Alkenyl chloroacetate; Glycidyl group-containing esters or ethers selected from glycidyl acrylate, vinylglycidyl ether, and acryl glycidyl ether; Unsaturated carboxylic acids selected from acrylic acid, methacrylic acid and maleic acid; 2-chloroethyl vinyl ether; Chloromethyl styrene; And one or more selected from the group consisting of acrylonitrile can be used.

Next, an electrode assembly including the separator of the present invention and a secondary battery having the same include a positive electrode and a negative electrode.

The positive electrode includes a positive electrode active material capable of reversibly intercalating and deintercalating lithium ions. Representative examples of the positive electrode active material include LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , LiMn ₂ O ₄ , or LiNi _{1 −} Lithium-transition metal oxides such as _{x- y} Co xMyO ₂ (0 ≤ x ≤ 1, 0 ≤ y ≤ 1, 0 ≤ x + y ≤ 1, M is a metal of Al, Sr, Mg, La, etc.) can be used However, the present invention is not limited to the type of the cathode active material.

The negative electrode includes a negative electrode active material capable of intercalating and deintercalating lithium ions, and as the negative electrode active material, crystalline or amorphous carbon or a carbon-based negative electrode active material of a carbon composite may be used. In the present invention, the type of the negative electrode active material is not limited.

In addition, the positive electrode includes a positive electrode current collector, aluminum and an aluminum alloy may be used as the positive electrode current collector, the negative electrode may include a negative electrode current collector, and copper and a copper alloy may be used as the negative electrode current collector. Can be. Examples of the positive electrode current collector and the negative electrode current collector include a foil, a film, a sheet, a punched one, a porous body, a foam, and the like.

The two electrodes may be laminated in a state in which the porous membrane of the present invention is formed on the positive electrode or the negative electrode, or both, or may be wound after the lamination to form an electrode group. As described above, since the porous membrane itself may serve as a separator, it may be omitted to provide a separate separator between the two electrodes.

Conventional film type separators have a problem of shrinkage at high temperatures, but the porous membrane is not likely to shrink or melt. Conventional polyolefin-based film separators generate harder shorts because the peripheral film is continuously shrunk or melted in addition to the parts damaged by initial heat generation during internal short-circuit, and thus the film separator burns out. The electrode on which the porous membrane is formed has only a small damage in a portion where an internal short circuit occurs, and does not lead to a widening of the short circuit region. In addition, the electrode formed with the porous membrane generates a very small short instead of a hard short when overcharging and continuously consumes the overcharge current, thereby maintaining a constant voltage between 5V and 6V and a battery temperature of 100 ° C. or less. Stability can also be improved.

In particular, in the present invention, since the ceramic layer can be densely formed by using the lean piece ceramic particles, the internal short circuit can be effectively prevented to improve the overcharge characteristic, and a predetermined amount of the porous film layer containing the ceramic material By including the antacid, it is possible to improve the low-temperature discharge characteristics while preventing the deform (deform) occurs when rolled with jelly roll.

Next, the secondary battery provided with the electrode assembly containing the separator of the present invention contains an electrolyte solution.

The electrolyte according to the present invention includes a non-aqueous organic solvent, and the non-aqueous organic solvent may be carbonate, ester, ether or ketone. The carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methylpropyl carbonate (MPC), ethylpropyl carbonate (EPC), methylethyl carbonate (MEC) ethylene carbonate (EC), Propylene carbonate (PC), butylene carbonate (BC) and the like can be used, and the ester is butyrolactone (BL), decanolide (decanolide), valerolactone, mevalonolactone (mevalonolactone) , Caprolactone, n-methyl acetate, n-ethyl acetate, n-propyl acetate, and the like may be used. The ether may be dibutyl ether, and the like, and the ketone may include polymethylvinyl ketone. The present invention is not limited to the type of nonaqueous organic solvent.

When the non-aqueous organic solvent is a carbonate-based organic solvent, it is preferable to use a mixture of cyclic carbonate and chain carbonate. In this case, the cyclic carbonate and the chain carbonate are preferably used by mixing in a volume ratio of 1: 1 to 1: 9, and more preferably used by mixing in a volume ratio of 1: 1.5 to 1: 4. The performance of the electrolyte is preferable when mixed in the above volume ratio.

The electrolyte solution of the present invention may further include an aromatic hydrocarbon organic solvent in the carbonate solvent. An aromatic hydrocarbon compound may be used as the aromatic hydrocarbon organic solvent.

Specific examples of the aromatic hydrocarbon-based organic solvent include benzene, fluorobenzene, chlorobenzene, nitrobenzene, toluene, fluorotoluene, trifluorotoluene, xylene and the like. In the electrolyte containing an aromatic hydrocarbon-based organic solvent, the volume ratio of the carbonate solvent / aromatic hydrocarbon solvent is preferably 1: 1 to 30: 1. The performance of the electrolyte is preferable when mixed in the above volume ratio.

In addition, the electrolyte according to the present invention includes a lithium salt, the lithium salt acts as a source of lithium ions in the battery to enable the operation of the basic lithium battery, for example LiPF ₆ , LiBF ₄ , LiSbF ₆ , LiAsF ₆ , LiClO ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ , LiN (C ₂ F ₅ SO ₂ ) ₂ , LiAlO ₄ , LiAlCl ₄ , LiN (C _x F _{2x +1} SO ₂ ) (CyF _{2x + 1} SO ₂ ), where x and y are natural water and LiSO ₃ CF ₃ , including one or more or mixtures thereof.

At this time, the concentration of the lithium salt can be used within the range of 0.6 to 2.0M, preferably 0.7 to 1.6M range. If the concentration of the lithium salt is less than 0.6M, the conductivity of the electrolyte is lowered and the performance of the electrolyte is lowered. If the lithium salt is more than 2.0M, the viscosity of the electrolyte is increased, thereby reducing the mobility of lithium ions.

The separator of the present invention as described above is laminated between the negative electrode and the positive electrode, or after lamination, is wound up to form an electrode group, and then placed in a can or a similar container, and then an electrolyte is injected to prepare a secondary battery. .

Hereinafter, preferred examples and comparative examples of the present invention are described. However, the following examples are only preferred embodiments of the present invention and the present invention is not limited to the following examples.

Example 1

LiCoO ₂ as a positive electrode active material, polyvinylidene fluoride (PVDF) as a binder and carbon as a conductive agent were mixed in a weight ratio of 92: 4: 4, and then dispersed in N-methyl-2-pyrrolidone to prepare a positive electrode slurry. It was. The slurry was coated on an aluminum foil having a thickness of 20 μm, dried, and rolled to prepare a positive electrode. Synthetic graphite as a negative electrode active material, styrene-butadiene rubber as a binder, and carboxymethyl cellulose as a thickener were mixed in a weight ratio of 96: 2: 2, and then dispersed in water to prepare a negative electrode active material slurry. The slurry was coated on a copper foil having a thickness of 15 μm, dried, and rolled to prepare a negative electrode.

A porous membrane made of a ceramic material and a binder was interposed between the prepared electrodes, and the coils were wound and compressed to be inserted into a cylindrical can.

In this case, alumina (Al ₂ O ₃ ) was used as the ceramic material, and acrylic rubber was mixed as a binder, and diluted in an N-methyl-2-pyrrolidone / cyclohexanone mixed solvent to form a porous film paste. A porous film was formed between the cathode and the anode.

In addition, as the ceramic material, flake ceramic particles were used, and magnesium oxide was added in an amount of 1 part by weight based on 100 parts by weight of the ceramic material as an antacid.

An electrolyte was injected into the cylindrical can to prepare a lithium secondary battery.

Example 2

The same procedure as in Example 1 was conducted except that 10 parts by weight of magnesium oxide was added as the antacid.

Example 3

The same procedure as in Example 1 was performed except that magnesium hydroxide was added in an amount of 2 parts by weight relative to the ceramic material as an antacid.

Example 4

The same procedure as in Example 1 was performed except that magnesium hydroxide was added in an amount of 9 parts by weight relative to the ceramic material as an antacid.

Example 5

The same procedure as in Example 1 was performed except that magnesium silicate was added in an amount of 3 parts by weight relative to the ceramic material as an antacid.

Example 6

Magnesium silicate was added in the same manner as in Example 1 except that 8 parts by weight of magnesium silicate was added as the antacid.

Comparative Example 1

The same process as in Example 1 was carried out except that a ball-shaped ceramic particle was used as the ceramic material and no antacid was added.

Comparative Example 2

It was carried out in the same manner as in Example 1 except that the ball-shaped ceramic particles were used as the ceramic material and 0.9 parts by weight of magnesium oxide was added as the antacid.

Comparative Example 3

It was carried out in the same manner as in Example 1 except that the ball-shaped ceramic particles were used as the ceramic material and 11 parts by weight of magnesium oxide was added as the antacid.

[Comparative Example 4]

The same process as in Example 1 was carried out except that ball-shaped ceramic particles were used as the ceramic material and 0.5 parts by weight of magnesium hydroxide was added as the antacid.

[Comparative Example 5]

It was carried out in the same manner as in Example 1 except that a ball-shaped ceramic particle was used as the ceramic material and 13 parts by weight of magnesium hydroxide was added as an antacid.

Comparative Example 6

It was carried out in the same manner as in Example 1 except that the ball-shaped ceramic particles were used as the ceramic material and 0.8 parts by weight of magnesium silicate was added as the antacid.

Comparative Example 7

It was carried out in the same manner as in Example 1 except that ball-shaped ceramic particles were used as the ceramic material and 10.5 parts by weight of magnesium silicate was added as the antacid.

Comparative Example 8

The same procedure as in Example 1 was conducted except that no antacid was added.

Comparative Example 9

Magnesium oxide was added as an antacid in the same manner as in Example 1 except that 0.8 parts by weight of the ceramic material was added.

Comparative Example 10

Magnesium oxide as an antacid was added in the same manner as in Example 1 except that 11 parts by weight of the ceramic material was added.

Comparative Example 11

Magnesium hydroxide was added in the same manner as in Example 1 except that 0.7 parts by weight of magnesium hydroxide was added as the antacid.

Comparative Example 12

Magnesium hydroxide was added in the same manner as in Example 1 except that 12 parts by weight of magnesium hydroxide was added as a antacid.

Comparative Example 13

Magnesium silicate was added in the same manner as in Example 1 except that 0.9 parts by weight of the ceramic material was added as an antacid.

Comparative Example 14

Magnesium silicate was added in the same manner as in Example 1 except that 13 parts by weight of magnesium silicate was added as the antacid.

The lithium batteries of Examples 1 to 6 and Comparative Examples 1 to 14 were discharged at -20 ° C. at 3 C at 1 C charge / discharge rate to measure low-temperature discharge capacity, and when this was less than 10% of the normal-temperature discharge capacity, “NG”, 10 In the case of% or more, "OK" was indicated.

In addition, the lithium batteries of Examples 1 to 6 and Comparative Examples 1 to 14 were charged for 3 hours at 1C charge / discharge rate for 12 hours to measure overcharge characteristics, and when ignition or rupture occurred, "NG", ignition or rupture occurred. When this did not occur, "OK" was displayed.

In addition, by measuring the wound electrode assembly of the lithium battery of Examples 1 to 6 and Comparative Examples 1 to 14 by X-ray tomography by comparing the degree of distortion compared to the standard round shape jelly jelly deform (deform) characteristics are measured When this is not satisfied, "NG" is indicated, and when it is satisfied, "OK" is indicated.

The measurement results are shown in Table 1 below.

TABLE 1

division Ceramic shape Antacid Type Antacid content Deform characteristic Low temperature discharge characteristics Overcharge Characteristics Example 1 Lean Magnesium oxide One OK OK OK Example 2 Lean Magnesium oxide 10 OK OK OK Example 3 Lean Magnesium hydroxide 2 OK OK OK Example 4 Lean Magnesium hydroxide 9 OK OK OK Example 5 Lean Magnesium silicate 3 OK OK OK Example 6 Lean Magnesium silicate 8 OK OK OK Comparative Example 1 Ball shape × 0 OK OK NG Comparative Example 2 Ball shape Magnesium oxide 0.9 OK OK NG Comparative Example 3 Ball shape Magnesium oxide 11 NG OK NG Comparative Example 4 Ball shape Magnesium hydroxide 0.5 OK OK NG Comparative Example 5 Ball shape Magnesium hydroxide 13 NG OK NG Comparative Example 6 Ball shape Magnesium silicate 0.8 OK OK NG Comparative Example 7 Ball shape Magnesium silicate 10.5 NG OK NG Comparative Example 8 Lean × 0 OK NG OK Comparative Example 9 Lean Magnesium oxide 0.8 OK NG OK Comparative Example 10 Lean Magnesium oxide 11 NG OK OK Comparative Example 11 Lean Magnesium hydroxide 0.7 OK NG OK Comparative Example 12 Lean Magnesium hydroxide 12 NG OK OK Comparative Example 13 Lean Magnesium silicate 0.9 OK NG OK Comparative Example 14 Lean Magnesium silicate 13 NG OK OK

Referring to Table 1, Examples 1 to 6 use lean piece ceramic particles, and by adding magnesium oxide, magnesium hydroxide and magnesium silicate within the range of 1 to 10 parts by weight with respect to the ceramic particles as antacid, It can be seen that the ceramic particles have insulation properties to satisfy the overcharging characteristics, and the antacid removes HF and secures pores, which are lithium ion passageways, to satisfy both low-temperature discharge characteristics and overcharge characteristics.

However, Comparative Examples 1 to 7 are in the shape of a ceramic particle ball, Comparative Example 1 is a case in which no antacid is added, and in Comparative Examples 2 to 7 the content of the antacid is less than 1 part by weight relative to the ceramic particles, or 10 In the case of exceeding the weight part, first, regardless of the addition of the antacid, the ball-shaped ceramic has a high porosity, and thus satisfies the low-temperature discharge characteristics, but because it is too porous, the internal short circuit cannot be completely prevented. When lithium dendrites were precipitated at the cathode, the anode and the short were eventually generated, causing fire and explosion. In addition, when the content of the antacid is less than 1 part by weight, there is no problem, but when the content of the antacid exceeds 10 parts by weight, the mixing dispersibility is not good, so that the coating thickness of the ceramic layer cannot be uniform, deform).

In addition, Comparative Examples 8 to 14 are in the form of lean flakes, Comparative Example 8 is a case in which the antacid is not added, and in Comparative Examples 9 to 14, the content of the antacid is less than 1 part by weight or 10 parts by weight relative to the ceramic particles. In case of exceeding, the ceramic layer can be densely formed regardless of whether or not the antacid is included, thereby effectively preventing the internal short circuit, thereby satisfying the overcharge characteristic, but the content of Comparative Example 8 and the antacid without the antacid is 1 part by weight. In the case of Comparative Examples 9, 11, and 13 added below, the ceramic layer is too dense so that lithium ions cannot move smoothly at low temperatures, and thus low temperature discharge characteristics are not good. In addition, in the case of Comparative Examples 10, 12, 14, the content of the antacid was added in excess of 10 parts by weight, the low-temperature discharge characteristics were improved, but the coating thickness of the ceramic layer could not be uniformed due to poor mixing dispersibility, deformed when wound (deform) occurred.

Therefore, in the present invention, by using the lean flake ceramic particles, by adding the content of the antacid in an amount of 1 to 10 parts by weight relative to the ceramic material, while satisfying low-temperature discharge characteristics and overcharge characteristics, deform during winding of the electrode assembly (deform) This can be prevented from occurring.

The present invention has been shown and described with reference to the preferred embodiments as described above, but is not limited to the above embodiments and those skilled in the art without departing from the spirit of the present invention. Various changes and modifications will be possible.

Claims (13)

A positive electrode having a positive electrode active material layer; A negative electrode having a negative electrode active material layer; And A porous membrane which separates the positive electrode and the negative electrode and is bonded by a flake ceramic material and a binder; The porous membrane includes an antacid, and the content of the antacid is 1 to 10 parts by weight based on 100 parts by weight of the ceramic material. The method of claim 1, The antacid is an electrode assembly, characterized in that at least one material selected from the group consisting of magnesium oxide, magnesium hydroxide and magnesium silicate. The method of claim 1, The ceramic material is at least one material selected from the group consisting of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ) and titanium oxide (TiO ₂ ). The method of claim 1, The electrode assembly, characterized in that the width of the long diameter of the flake ceramic material particles of 100nm to 1㎛. The method of claim 1, Wherein the antacid is greater than or equal to 10 nm and less than or equal to the width of the long diameter of the flake-shaped ceramic material particles. The method of claim 1, The binder is an electrode assembly, characterized in that the synthetic rubber-based latex binder or acrylic rubber having a crosslinked structure. An electrode assembly including a positive electrode having a positive electrode active material layer, a negative electrode having a negative electrode active material layer, and a porous membrane separating the positive electrode and the negative electrode and bonded by a flake ceramic material and a binder; And Including an electrolyte solution, The porous film includes an antacid, and the content of the antacid is 1 to 10 parts by weight based on 100 parts by weight of the ceramic material. The method of claim 7, wherein The antacid is a secondary battery, characterized in that at least one material selected from the group consisting of magnesium oxide, magnesium hydroxide and magnesium silicate. The method of claim 7, wherein The ceramic material is at least one material selected from the group consisting of silica (SiO ₂ ), alumina (Al ₂ O ₃ ), zirconium oxide (ZrO ₂ ) and titanium oxide (TiO ₂ ). The method of claim 7, wherein A secondary battery, characterized in that the width of the long diameter of the flake-shaped ceramic material particles is 100nm to 1㎛. The method of claim 7, wherein The size of the antacid is 10nm or more, characterized in that less than the width of the long diameter of the flake-like ceramic material particles. The method of claim 7, wherein The binder is a secondary rubber, characterized in that the synthetic rubber-based latex binder or acrylic rubber having a crosslinked structure. The method of claim 7, wherein The electrolyte solution is a secondary battery comprising a non-aqueous organic solvent and a lithium salt.