KR20200005965A - Separator for Secondary Battery Comprising Anti-flame Inorganic Materials - Google Patents

Abstract

The present invention relates to a separator for a secondary battery comprising a flame-retardant inorganic material. Specifically, the present invention relates to a separator for a secondary battery comprising a flame retardant inorganic material, wherein the flame-retardant inorganic material is an inorganic material having 9 m^2/g of a specific surface area. The separator for a secondary battery represents flame retardancy and can maintain similar electrochemical characteristics.

Description

Separator for Secondary Battery Comprising Anti-flame Inorganic Materials

The present invention relates to a secondary battery separator comprising a flame retardant inorganic material, and more particularly, to a secondary battery separator having a specific surface area of 9 m 2 / g or more.

BACKGROUND ART With the lighter weight and higher functionality of portable devices such as smartphones, laptops, tablet PCs, and portable game machines, demand for secondary batteries used as driving power sources is increasing. In the past, nickel-cadmium, nickel-hydrogen, nickel-zinc batteries and the like have been used. Currently, lithium secondary batteries with high operating voltage and high energy density per unit weight are used.

The demand for lithium secondary batteries is increasing in proportion to the growth of the portable device market. Recently, the use of lithium secondary batteries has been expanded to include power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), and storage of renewable energy. .

The lithium secondary battery has a structure in which an electrode assembly capable of charging / discharging a cathode / separator / cathode structure is mounted in a battery case. A positive electrode and a negative electrode are manufactured by apply | coating, drying, and rolling the slurry containing an electrode active material etc. to one or both surfaces of a metal current collector.

Separator is one of the important factors that determine the life of the secondary battery, the ion permeability and mechanical strength is required to electrically pass the electrolyte while electrically insulating the positive electrode and the negative electrode. As the application of high-energy lithium secondary battery is expanding, the demand for safety at high temperature of the separator is also increasing. Beyond the stability under non-specific conditions, there is a need for a specific technique in which the temperature of the battery may not rise above the flash point even in an internal short circuit caused by penetration by a conductor such as a nail.

Hydroxide-based inorganic flame retardants are used in resins and the like as flame retardants that absorb heat at a constant temperature. Hydroxide-based inorganic flame retardants have been used in various ways to increase the flame retardancy of secondary batteries.

Patent document 1 relates to a lithium ion battery having improved high temperature storage characteristics, and uses a metal hydroxide having a large specific surface area as an additive for a positive electrode. This is to minimize the decomposition reaction caused by the self-discharge and the reactivity of the anode to the non-aqueous electrolyte, which may occur when long-term exposure to 40 ℃ during storage after full charge.

Although Patent Literature 1 uses a metal hydroxide having a large specific surface area, it is used only as an additive for a positive electrode, and does not consider any flame retardant characteristics due to decomposition of hydroxides generated at 100 ° C. or higher, such as through a nail.

Patent document 2 relates to a lithium secondary battery having improved heat resistance, and proposes an electrode on which an organic / inorganic composite porous coating layer including endothermic inorganic particles and a binder polymer is formed on a surface of an electrode. The endothermic inorganic particles may be at least one selected from the group consisting of antimony-containing compounds, metal hydroxides, guanidine-based compounds, boron-containing compounds, and zinc stannate, and the endothermic inorganic particles may be used as components or coating components of the separator. Used.

Patent document 3 relates to an electrode assembly including an asymmetrically coated separator and an electrochemical device including the electrode assembly, a positive electrode current collector; A cathode unit comprising a cathode active material layer coated on both surfaces of the cathode current collector and a separator attached to one surface of the cathode current collector; And a negative electrode current collector; In the electrode assembly composed of a plurality of negative electrode unit consisting of a negative electrode active material layer coated on both sides of the negative electrode current collector and a separator attached to one surface of the negative electrode current collector in a crossover, the separator is each of the positive or negative electrode unit One surface in contact with the active material therein relates to an electrode assembly comprising an asymmetric coating separator, characterized in that the other surface is asymmetrically coated with an adhesion-strengthening member. Patent document 2 can be asymmetrically coated with the hydroxide inorganic flame retardant only on the positive electrode or the negative electrode.

Patent document 4 is a separator used for a non-aqueous electrolyte secondary battery, and is composed of a laminate in which at least two layers are stacked, and at least one of the at least two layers has a shutdown temperature of 140 ° C. or lower, and at least one further heat. The strain temperature (JIS K 7207 A method) is 100 degreeC or more, and the oxygen index (JIS K 7201) of the layer which opposes an anode is 26 or more, It is related with the separator for non-aqueous electrolyte secondary batteries.

In patent document 4, the layer which opposes the cathode of a separator is comprised from the material based on polyolefin, and the layer which opposes an anode is comprised from fluorine-type resin, an inorganic compound, and a flame retardant.

Although various flame retardants are used to increase the safety of the lithium secondary battery as described above, it has been observed by the present inventors that the flame retardant properties are non-uniform even though the flame retardants have the same chemical formula. This non-uniform flame retardant property is a problem that does not appear even if the flame retardant is added as a component of the separator. In the related art, it is understood that such non-uniform flame retardant characteristics are not recognized as a problem, and of course, no solution has been suggested.

Republic of Korea Patent Publication No. 2005-0014701 Republic of Korea Patent Publication No. 0833038 Republic of Korea Patent Publication No. 2012-0079515 Japanese Laid-Open Patent Publication No. 2006-269359

The present invention is to solve the above problems, it is an object to solve the non-uniformity of the flame retardant properties despite being a flame retardant of the same formula. An object of the present invention is to provide a secondary battery separator and a secondary battery comprising the same, including a flame retardant capable of expressing flame retardant properties by solving the above problems.

In the first aspect of the present invention for solving the above problems is a secondary battery separator comprising a flame retardant inorganic material,

The flame retardant inorganic material provides a separator for secondary batteries having a specific surface area of 9 m 2 / g or more.

The flame retardant inorganic material is at least one selected from the group consisting of antimony-containing compounds, metal hydroxides or metal hydrates, guanidine-based compounds, boron-containing compounds and zinc stannate.

The antimony-containing compound is selected from antimony trioxide (Sb ₂ O ₃ ), antimony tetraoxide (Sb ₂ O ₄ ), and antimony pentoxide (Sb ₂ O ₅ );

The metal hydroxide or metal hydrate is selected from aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), aluminum oxyhydroxide (AlO (OH)), CaO.Al ₂ O ₃ .6H ₂ O. Selected;

The guanidine-based compound is selected from the group consisting of guanidine nitrate, guanidine sulfamic acid, guanidine phosphate and guanyl urea phosphate;

The boron-containing compound is H ₃ BO ₃ or HBO ₂ ;

The zinc stannate compound is selected from Zn ₂ SnO ₄ , ZnSnO ₃ , ZnSn (OH) ₆ .

The flame retardant inorganic material is at least one of aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), aluminum oxyhydroxide (AlO (OH)), CaO-Al ₂ O ₃ .6H ₂ O. .

The flame retardant inorganic material is aluminum hydroxide (Al (OH) ₃ ).

The flame retardant inorganic material is present asymmetrically in only one of the positive or negative electrode faces.

The secondary battery separator is a mixture of inorganic particles and a binder polymer and is an organic / inorganic composite porous separator without a polyolefin substrate,

A separator for forming an organic / inorganic composite porous coating layer coated with a mixture of inorganic particles and a binder polymer on the surface of a porous polyolefin substrate and / or pores of the substrate,

The flame retardant inorganic material may be distributed over the separator or coated on a part of the surface.

The inorganic particles are added separately from the flame retardant inorganic material,

High dielectric constant inorganic particles having a dielectric constant of 1 or more, inorganic particles having piezoelectricity, inorganic particles having lithium ion transfer ability, or a mixture of two or more thereof.

The inorganic particles are at least one member selected from the group consisting of Al ₂ O ₃ , SiO ₂ , MgO, TiO _2, and BaTiO ₂ .

The flame retardant mineral is at least 2% by weight of the total inorganic.

The flame retardant mineral is at least 5% by weight of the total inorganic

The binder polymer is polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride Chlorotrifluoroethylene (PVdF-CTFE), polymethylmethacrylate, polyvinylacetate, ethylene-co-vinylacetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyano Ethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxy methyl cellulose, acrylonitrile styrene butadiene copolymer, polyimide, polyacrylonitrile-styrene copolymer, gelatin , Polyethylene glycol, polyethylene glycol dimethyl ether, ethyl - it is at least one selected from diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber (SBR), tetrafluoroethylene base ethylene (TFE), the group consisting of fluorine rubber and polyimide-propylene.

The binder polymer is at least one member selected from the group consisting of PVdF, TFE and polyimide.

The binder polymer is a phenolic compound including bicalin, luteolin, taxoxyline, mycetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, picethenol, tannic acid, pyrogallic It further comprises at least one or more of an aqueous or non-aqueous polymer consisting of acid, amylose, amylopectin, xanthan gum, fatty acid.

Secondary battery separator according to the present invention has the advantage that 1) the flame retardant properties are necessarily expressed, and 2) similar electrochemical properties compared to the conventional inorganic coating separator.

1 is a graph and a photograph showing the results of safety measurements of Example 1 and Comparative Example 1. FIG.
2 is a heat shrinkage test result of Example 1 and Comparative Example 1.

Hereinafter, the present invention will be described in detail. Prior to this, terms or words used in the present specification and claims should not be construed as being limited to the ordinary or dictionary meanings, and the inventors should properly explain the concept of terms in order to best explain their own inventions. Based on the principle that it can be defined, it should be interpreted as meaning and concept corresponding to the technical idea of the present invention. Therefore, the configurations presented in the embodiments described herein are only one of the most preferred embodiments of the present invention, and do not represent all of the technical idea of the present invention, and various equivalents may be substituted for them at the time of the present application. It should be understood that there may be variations.

The present invention provides a secondary battery separator comprising a flame-retardant inorganic separator, the specific surface area of the flame-retardant inorganic material is 9 m 2 / g or more. Preferably, the specific surface area of the flame retardant inorganic material may be 9 m 2 / g or more and 300 m 2 / g or less.

1) Flame Retardant Minerals

The flame retardant mineral according to the present invention is at least one selected from the group consisting of antimony-containing compounds, metal hydroxides or metal hydrates, guanidine-based compounds, boron-containing compounds and zinc stannate.

The antimony-containing compound is selected from antimony trioxide (Sb ₂ O ₃ ), antimony tetraoxide (Sb ₂ O ₄ ), antimony pentoxide (Sb ₂ O ₅ ); The metal hydroxide or metal hydrate is selected from aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), aluminum oxyhydroxide (AlO (OH)), CaOAl ₂ O ₃ 6H ₂ O; The guanidine-based compound is selected from the group consisting of guanidine nitrate, guanidine sulfamic acid, guanidine phosphate and guanyl urea phosphate; The boron-containing compound is H ₃ BO ₃ or HBO ₂ ; The zinc stannate compound is selected from Zn ₂ SnO ₄ , ZnSnO ₃ , ZnSn (OH) ₆ .

Preferred flame retardant minerals are one or more of aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), aluminum oxyhydroxide (AlO (OH)), CaOAl ₂ O ₃ 6H ₂ O, or more. Preferably the flame retardant inorganic material is aluminum hydroxide (Al (OH) ₃ ).

Al (OH) ₃ , Mg (OH) ₂ , AlOOH, CaOAl ₂ O ₃ 6H ₂ O are flame retardant by the following formula.

2Al (OH) ₃ → Al ₂ O ₃ + 3H ₂ O (mainly 180 ~ 300 ℃, -280cal / g (-1172kJ / kg))

Mg (OH) ₂ → MgO + H ₂ O (Mainly 300 ~ 400 ℃,-328ca / g (-1372kJ / kg))

3CaOAl ₂ O ₃ 6H ₂ O → Al ₂ O ₃ + 3CaO + 6H ₂ O (mainly 250 ° C, -340cal / mol)

The metal hydroxide in the flame retardant inorganic material according to the present invention undergoes decomposition while an endothermic reaction, which is an endothermic reaction, occurs as the temperature increases.

Metal hydroxides or metal hydrates have a larger specific surface area As the reactivity increases, dehydration occurs at a low temperature, thus the flame retardant properties can be exhibited at a low temperature.

The flame retardant properties of metal hydroxides according to these specific surface areas have not been recognized as a problem until now. The present inventors have made efforts to solve the non-uniform flame retardant properties appearing intermittently to recognize the non-uniform flame retardant properties due to the above problems and to derive the present invention that solved them.

The flame retardant mineral is 2% by weight, preferably 5% by weight or more of the total flame retardant minerals. In addition, the flame retardant inorganic material may be present asymmetrically at only one of the anode or cathode face of the separator. This is because water, which is a product of the decomposition reaction of the metal hydroxide in the flame retardant inorganic material, may cause an additional reaction with the lithium of the electrode.

The surface area of the metal hydroxide can be controlled by milling, pulverizing, or the like, and also by controlling the heat treatment temperature during the production of the particles.

2) separator

The secondary battery separator according to the present invention uses a mixture of inorganic particles and a binder polymer and is an organic / inorganic composite porous separator without a polyolefin substrate, or a surface of a porous polyolefin substrate and / or a porous portion of a substrate with inorganic particles and a binder polymer. As a separator forming an organic / inorganic composite porous coating layer coated with a mixture, the flame retardant inorganic material may be distributed throughout the separator or coated on a part of a surface thereof.

In lithium secondary batteries, the deposition of lithium ions occurs mainly at the negative electrode, so that a hydroxide-based inorganic flame retardant may be coated on only the separator facing the positive electrode, resulting in the flame retardant effect, but the reaction of the precipitated lithium and moisture occurs. Can be prevented.

At this time, the opposite side of the negative electrode side can be coated with a binder for forming an adhesive layer or a conventional alumina-based SRS, but in order to increase the flame retardant effect, it is effective to make the positive electrode side thicker than the negative electrode side.

The overall thickness of the separator according to the present invention is usually similar to the separator coated with inorganic on the opposite side of the anode and cathode. The thickness may be in the range of 5 μm to 30 μm. When the thickness of the separator is smaller than 5 μm, the strength of the separator may be weak and easily damaged. When the thickness of the separator is larger than 30 μm, the thickness of the electrode assembly may be increased and the capacity may be decreased, which is not preferable.

The charge-discharge cycle characteristics at 35 ° C. or more and 50 ° C. or less of a battery including a separator according to the present invention are the same as those of a battery composed of a separator coated on both sides with the inorganic material. The effect of temperature is not distinguished below 35 ° C., and at 50 ° C. or higher, both sides of the conventional membrane are coated with the inorganic material because thermal stability is inferior to the separator according to the present invention.

3) inorganic particles

The inorganic particles used in the separator according to the present invention are added separately from the flame retardant inorganic material. It enables the formation of empty spaces between inorganic particles and serves as a form of spacers to maintain micro-pores and to maintain physical shape, and in general, physical properties do not change even at high temperatures of 200 ° C or higher. .

Such inorganic particles are not particularly limited as long as they are electrochemically stable, i.e., the inorganic particles that can be used in the present invention are oxidized and / Or it will not specifically limit, if a reduction reaction does not occur. In particular, when inorganic particles having high electrolyte ion transfer ability are used, since the performance in the electrochemical device can be improved, it is preferable that the electrolyte ion transfer ability as high as possible. In addition, when the inorganic particles have a high density, it is not only difficult to disperse when forming the separator, but also has a problem of weight increase during battery manufacturing, and therefore, the smallest possible density is preferable. In addition, in the case of an inorganic material having a high dielectric constant, it is possible to contribute to an increase in the degree of dissociation of an electrolyte salt such as lithium salt in the liquid electrolyte, thereby improving the ionic conductivity of the electrolyte solution.

For these reasons, the inorganic particles are high dielectric constant inorganic particles having a dielectric constant of 1 or more, preferably 10 or more, inorganic particles having piezoelectricity, inorganic particles having lithium ion transfer ability, or two or more thereof. It may be a mixture.

Examples of the inorganic particles having a dielectric constant of 1 or more include SrTiO ₃ , SnO ₂ , CeO ₂ , MgO, NiO, CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , Al ₂ O ₃ , TiO ₂ , SiC, or a mixture thereof. There is, but is not limited to this.

The piezoelectric inorganic particles are insulators at normal pressure, but mean a material having electrical properties through electrical structure change when a predetermined pressure is applied. The piezoelectricity inorganic particles not only exhibit a high dielectric constant having a dielectric constant of 100 or more, but also have a constant pressure. When tension or compression is applied, electric charge is generated so that one side is positively charged and the other side is negatively charged, thereby generating a potential difference between both surfaces.

In the case of using the inorganic particles having the above characteristics, when the internal short circuit of the positive electrode occurs due to external impact such as local crush, nail, etc., the anode and the cathode do not directly contact due to the inorganic particles coated on the separator. In addition, due to the piezoelectricity of the inorganic particles, the potential difference in the particles is generated, which results in electron movement between the positive electrodes, that is, a minute current flow, thereby reducing the voltage of the gentle battery and thereby improving safety. can do.

Examples of the inorganic particles having piezoelectric properties include BaTiO ₃ , Pb (Zr, Ti) O ₃ (PZT), Pb _1-x La _x Zr _1-y Ti _y O ₃ (PLZT), Pb (Mg _1/3 Nb _{2 / 3} ) O ₃ -PbTiO ₃ (PMN-PT) hafnia (HfO ₂ ) or mixtures thereof, but is not limited thereto.

The inorganic particles having a lithium ion transfer capacity refers to inorganic particles containing lithium elements but having a function of transferring lithium ions without storing lithium, and the inorganic particles having lithium ion transfer ability are present in the particle structure. Since the lithium ions can be transferred and moved due to a kind of defect, the lithium ion conductivity in the battery is improved, thereby improving battery performance.

Examples of the inorganic particles having the lithium ion transfer ability include lithium phosphate (Li ₃ PO ₄ ), lithium titanium phosphate (Li _x Ti _y (PO ₄ ) ₃ , 0 <x <2, 0 <y <3), and lithium aluminum Titanium Phosphate (Li _x Al _y Ti _z (PO ₄ ) ₃ , 0 <x <2, 0 <y <1, 0 <z <3), 14Li ₂ O-9Al ₂ O ₃ -38 TiO ₂ -39P ₂ O ₅ (LiAlTiP) xOy series glass (0 <x <4, 0 <y <13), lithium lanthanum titanate _{(Li x La y TiO 3,} 0 <x <2, 0 <y <3) , such as, Li _3.25 Ge Li germanium thiophosphate such as _0.25 P _0.75 S _4, etc. (Li _x Ge _y P _z S _w , 0 <x <4, 0 <y <1, 0 <z <1, 0 <w <5), Li ₃ Li nitride such as N (Li _x N _y , 0 <x <4, 0 <y <2), Si ₃ series glass such as Li ₃ PO ₄ -Li ₂ S-SiS ₂ (Li _x Si _y S _z , P ₂ S ₅ series glass (Li _x P _y S _z , 0 <x <3, 0) such as 0 <x <3, 0 <y <2, 0 <z <4), LiI-Li ₂ SP ₂ S ₅ <y <3, 0 <z <7), or mixtures thereof, but is not limited thereto.

When the above-mentioned high dielectric constant inorganic particles, piezoelectric inorganic particles, and inorganic particles having lithium ion transfer capability are mixed, their synergistic effect may be doubled.

The size of the inorganic particles is not limited, but is preferably in the range of 0.001 μm to 10 μm as much as possible for film formation of a uniform thickness and proper porosity. If the thickness is less than 0.001 μm, it is difficult to control the properties of the separator due to the deterioration of dispersibility. If the thickness is greater than 10 μm, the thickness of the separator manufactured with the same solid content is increased, and the mechanical properties are deteriorated. The probability of internal short circuit during discharge increases.

4) Binder

The binder is also commonly referred to as a polymeric binder and may have a feature that can be gelled during liquid electrolyte impregnation to exhibit a high degree of swelling. In fact, when the binder polymers are polymers having an excellent electrolyte impregnation rate, the electrolyte injected after battery assembly is permeated into the polymer, and the polymer having the absorbed electrolyte has electrolyte ion conducting ability. In addition, compared with the conventional hydrophobic polyolefin-based separator, the wettability of the battery electrolyte is improved and the polar electrolyte solution for the battery, which has been difficult to be used in the related art, is also possible. Thus, from, the polymer solubility parameter of 15 to 45MPa preferably ^1/2, more preferably from 15 to 25MPa ^1/2 and ^1/2 of 30 to 45MPa range. When the solubility parameter greater than ^1/2 to less than 15MPa and 45MPa ^1/2, it is difficult to be impregnated with (swelling) by conventional liquid electrolyte batteries.

Specifically polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride trichloroethylene, polyvinylidene fluoride chloro Trifluoroethylene (PVdF-CTFE), polymethyl methacrylate, polyvinylacetate, ethylene-co-vinylacetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullul Column, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile styrene butadiene copolymer, polyimide, polyacrylonitrile-styrene copolymer, gelatin, polyethylene Glycol, polyethylene glycol dimethyl ether, ethylene-propyl - it is at least one selected from the group consisting of diene-terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber (SBR), tetrafluoroethylene base ethylene (TFE), fluorinated rubber and polyimide. Preferably at least one selected from the group consisting of PVdF, TFE and polyimide.

The binder material is a phenolic compound, including pyocalin, luteolin, taxoxyline, mycetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, piacethenol and tannic acid, It may further include at least one or more of an aqueous or non-aqueous polymer consisting of acid, amylose, amylopectin, xanthan gum, fatty acid. The binder material contains a large amount of OH group to increase the adhesive strength of the binder-inorganic material and the substrate-binder, and at the same time, to prevent internal short circuit through self-healing function against some damage of the separator, and to prevent the separator from the anode and the cathode. It can improve the adhesion and can cope with the elution of the cathode material transition metal.

The binder content is 5 to 50 parts by weight, preferably 10 to 40 parts by weight based on 100 parts by weight of the inorganic particles.

5) solvent

The solvent for preparing the separator according to the present invention can be used without limitation conventional solvents known in the art, preferably acetone, tetrahydrofuran, acetonitrile, dimethyl formamide, dimethyl sulfoxide, dimethylacetamide, N- Methylpyrrole or water can be used, and these can also be used in mixture of 2 or more type.

The solvent is included 60 to 85 parts by weight based on 100 parts by weight of the slurry composition for the membrane coating. The content ratio (weight%) of an inorganic material: binder is 60-90: 40-10.

6) Composition and Application of Electrode Assembly

The present invention also provides an electrochemical device including an anode and a cathode, the separator interposed between the cathode and the cathode, and an electrolyte, wherein the electrochemical device may be a lithium secondary battery.

The positive electrode is manufactured by applying a mixture of a positive electrode active material, a conductive material, and a binder on a positive electrode current collector, followed by drying, and optionally, a filler may be further added.

The positive electrode current collector is generally made of a thickness of 3 μm or more and 500 μm or less. Such a positive electrode current collector is not particularly limited as long as it has conductivity without causing chemical change in the battery. For example, the positive electrode current collector may be formed on a surface of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel. The surface-treated with carbon, nickel, titanium, silver, etc. can be used. The current collector may form fine irregularities on its surface to increase the adhesion of the positive electrode active material, and may be in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

The positive electrode active material may be a layered compound such as lithium cobalt oxide (LiCoO ₂ ), lithium nickel oxide (LiNiO ₂ ), or a compound substituted with one or more transition metals; Lithium manganese oxides such as Li _{1 + x} Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _2, and the like; Lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , V ₂ O ₅ , Cu ₂ V ₂ O _7, and the like; Ni-site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ , wherein M = Co, Mn, Al, Cu, Fe, Mg, B, or Ga, and x = 0.01 to 0.3; Formula LiMn _2-x M _x O ₂ (wherein M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.01 to 0.1) or Li ₂ Mn ₃ MO ₈ (wherein M = Fe, Co, Lithium manganese composite oxide represented by Ni, Cu or Zn); LiMn ₂ O _{4 in} which a part of Li in the formula is substituted with alkaline earth metal ions; Disulfide compounds; Fe ₂ (MoO ₄ ) ₃ and the like, but are not limited to these.

The conductive material is typically added in an amount of 1 to 30 wt% based on the total weight of the mixture including the positive electrode active material. Such a conductive material is not particularly limited as long as it has conductivity without causing chemical change in the battery, and examples thereof include graphite such as natural graphite and artificial graphite; Carbon blacks such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fibers and metal fibers; Metal powders such as carbon fluoride powder, aluminum powder and nickel powder; Conductive whiskeys such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Conductive materials such as polyphenylene derivatives and the like can be used.

The binder is a component that assists the bonding of the active material and the conductive material to the current collector, and is generally added in an amount of 1 to 30 wt% based on the total weight of the mixture including the positive electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene , Polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber, fluorine rubber, various copolymers and the like.

The filler is optionally used as a component for inhibiting expansion of the positive electrode, and is not particularly limited as long as it is a fibrous material without causing chemical change in the battery. Examples of the filler include olefinic polymers such as polyethylene and polypropylene; Fibrous materials, such as glass fiber and carbon fiber, are used.

The negative electrode is manufactured by coating and drying a negative electrode material on a negative electrode current collector, and optionally, the components as described above may be further included if necessary.

The negative electrode current collector is generally made to a thickness of 3 μm or more and 500 μm or less. Such a negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical change in the battery. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel Surface-treated with carbon, nickel, titanium, silver and the like on the surface, aluminum-cadmium alloy and the like can be used. In addition, like the positive electrode current collector, fine concavities and convexities may be formed on the surface to enhance the bonding strength of the negative electrode active material, and may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, and a nonwoven fabric.

As said negative electrode active material, For example, carbon, such as hardly graphitized carbon and graphite type 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 ': metals such as Al, B, P, Si, Group 1, Group 2, Group 3 elements of the periodic table, halogen; 0 <x = 1; 1≤ = y≤ = 3; 1≤ = z≤ = 8) Complex oxides; 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 , and metal oxides such as Bi ₂ O ₅ ; Conductive polymers such as polyacetylene; Li-Co-Ni-based materials and the like can be used.

The present invention may also provide a battery pack including the electrochemical device.

Specifically, the battery pack may be used as a power source of a device requiring high temperature safety, long cycle characteristics, high rate characteristics, and the like, and a detailed example of such a device may include a mobile device and a wearable device. A power tool that is driven by an electric motor; Electric vehicles including electric vehicles (EVs), hybrid electric vehicles (HEVs), plug-in hybrid electric vehicles (PHEVs), and the like; Electric motorcycles including electric bicycles (E-bikes) and electric scooters (E-scooters); Electric golf carts; An energy storage system and the like, but are not limited thereto.

Since the structure of these devices and their fabrication methods are known in the art, detailed description thereof is omitted herein.

Hereinafter, the present invention will be described in more detail with reference to Examples and Experimental Examples, but the present invention is not limited to these Examples and Experimental Examples. Embodiments according to the present invention may be modified in many different forms, and the scope of the present invention should not be construed as limited to the embodiments described below. The embodiments of the present invention are provided to fully explain the present invention to those skilled in the art.

<Example 1>

After dissolving four binders of 30 wt% of the inorganic material in acetone, a slurry was prepared by mixing Al (OH) ₃ having a specific surface area of 14 m 2 / g.

The slurry was coated on a separator substrate and dried to complete the separator.

Comparative Example 1

After dissolving four binders of 30 wt% of the inorganic material in acetone, Al (OH) ₃ having a specific surface area of 7 m 2 / g was mixed to prepare a slurry, and a separator was prepared in the same manner as in Example 1.

<Measurement of specific surface area of metal hydroxide>

BET analysis was conducted to measure the specific surface area. The BET analysis was measured according to the measurement conditions of BELSORP-mini II of BEL Japan. The volumetric adsorption method was used for the measurement. First, the sample vessel is vacuumed and the adsorption isotherm is recorded by continuously increasing the nitrogen pressure to 0.995 atm under vacuum so that nitrogen can be physically adsorbed on the sample surface. The nitrogen pressure is then vacuumed and the desorption isotherm is recorded. Based on the results, it was calculated as the amount of nitrogen gas adsorption at liquid nitrogen temperature (77K) and the correlation coefficient was about 0.999.

<Heat shrinkage test of battery including separator>

After the battery was manufactured using the separators of Comparative Example 1 and Example 1, a heat shrinkage test was conducted on the battery.

The method for measuring the thermal contraction rate of the separator is not particularly limited, it can be used a method commonly used in the art. Non-limiting examples are as follows: fabricate five separator specimens cut at five different locations with 50 mm horizontal (MD) 50 mm vertical (TD) marking the MD / TD direction and marking the specimen at 150 ° C. After leaving for 30 minutes in a convection oven, calculate the average thermal shrinkage by measuring the horizontal and longitudinal shrinkage of each specimen.

2 is a heat shrinkage test result of Example 1 and Comparative Example 1.

As a result of the heat shrinkage test, the heat shrinkage in the machine direction (Machine Direction, MD) and the transverse direction (TD) of Comparative Example 1 was 46% and 39%, respectively, while Example 1 was 8% and 4%, respectively. Appeared in%.

That is, in the case of a membrane containing a flame retardant inorganic material having a specific surface area of 14 m 2 / g, the heat shrinkage is about 5.7 times in the machine direction (Machine Direction, MD) compared to a membrane containing a flame retardant inorganic material having a specific surface area of 7 m 2 / g, It can be seen that the heat shrinkage of the separator can be effectively suppressed by decreasing 9.7 times in the perpendicular direction (Transverse Direction, TD).

<Safety Measurement of Batteries with Separation Membrane-Nail Penetration Test

After the battery was manufactured using the separators of Comparative Example 1 and Example 1, a nail penetration test was performed on the battery, and a graph showing the voltage and temperature change with time and a result photograph are shown in FIG. 1.

The nail is 3 mm in diameter, has a slope of 30 degrees, and the speed of penetration through the nail is 80 mm / sec.

Referring to FIG. 1, in Comparative Example 1, the surface temperature of the battery rapidly increased, indicating that the safety was very poor. On the other hand, Example 1 according to the present invention was confirmed that the surface temperature of the battery is maintained at about 20 ℃, respectively, very excellent flame retardant performance. As a result of disassembling each cell, it was observed that all the inner fabric melted and all the pores of the fabric itself disappeared.

Therefore, the internal temperature of Example 1 can also be guessed as having risen more than 135 degreeC which is a melting point of a separator base material. Nevertheless, it was confirmed that the battery to which the flame retardant according to the present invention was added was very stable even at a very serious damage such as nail penetration since the external temperature was kept very stable.

Claims (15)

In the separator for secondary batteries containing a flame retardant inorganic material,
The flame retardant inorganic material has a specific surface area of 9 m 2 / g or more separator for secondary batteries. The method of claim 1,
The flame retardant inorganic material is at least one secondary battery separator selected from the group consisting of antimony-containing compounds, metal hydroxides or metal hydrates, guanidine-based compounds, boron-containing compounds and zinc stannate. The method of claim 2,
The antimony-containing compound is selected from antimony trioxide (Sb ₂ O ₃ ), antimony tetraoxide (Sb ₂ O ₄ ), antimony pentoxide (Sb ₂ O ₅ );
The metal hydroxide or metal hydrate is selected from aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), aluminum oxyhydroxide (AlO (OH)), CaOAl ₂ O ₃ 6H ₂ O;
The guanidine-based compound is selected from the group consisting of guanidine nitrate, guanidine sulfamic acid, guanidine phosphate and guanyl urea phosphate;
The boron-containing compound is H ₃ BO ₃ or HBO ₂ ;
The zinc stannate compound is Zn ₂ SnO ₄ , ZnSnO ₃ , ZnSn (OH) _{6 The} separator for secondary batteries. The method of claim 3,
The flame retardant inorganic material is at least one of aluminum hydroxide (Al (OH) ₃ ), magnesium hydroxide (Mg (OH) ₂ ), aluminum oxy hydroxide (AlO (OH)), CaOAl ₂ O ₃ 6H ₂ O separator. The method of claim 4, wherein
The flame retardant inorganic material is aluminum hydroxide (Al (OH) ₃ ) separator for secondary batteries. The method of claim 1,
The flame-retardant inorganic membrane is a secondary battery separator that exists asymmetrically in only one of the positive or negative electrode facing. The method of claim 1,
The secondary battery separator is an organic / inorganic composite porous separator using a mixture of inorganic particles and a binder polymer and without a polyolefin base material,
A separator for forming an organic / inorganic composite porous coating layer coated with a mixture of inorganic particles and a binder polymer on the surface of a porous polyolefin substrate and / or pores of the substrate,
Separation membrane for a secondary battery that the flame-retardant inorganic material may be distributed over the separator or coated on a portion of the surface. The method of claim 7, wherein
The inorganic particles are added separately from the flame retardant inorganic material,
Separation membrane for a secondary battery, which is a high dielectric constant inorganic particles having a dielectric constant of 1 or more, inorganic particles having piezoelectricity, inorganic particles having a lithium ion transfer ability or a mixture of two or more thereof. The method of claim 7, wherein
The inorganic particles are at least one secondary battery separator selected from the group consisting of Al ₂ O ₃ , SiO ₂ , MgO, TiO ₂ and BaTiO ₂ . The method of claim 7, wherein
The flame retardant inorganic material is at least 2% by weight of the secondary battery separator. The method of claim 7, wherein
The flame retardant inorganic material is at least 5% by weight of the secondary battery separator. The method of claim 7, wherein
The binder polymer is polyvinylidene fluoride (PVdF), polyvinylidene fluoride-hexafluoropropylene, polyvinylpyrrolidone, polyacrylonitrile, polyvinylidene fluoride-trichloroethylene, polyvinylidene fluoride Chlorotrifluoroethylene (PVdF-CTFE), polymethylmethacrylate, polyvinylacetate, ethylene-co-vinylacetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyano Ethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxy methyl cellulose, acrylonitrile styrene butadiene copolymer, polyimide, polyacrylonitrile-styrene copolymer, gelatin , Polyethylene glycol, polyethylene glycol dimethyl ether, ethyl -Propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene butylene rubber (SBR), tetrafluoroethylene base ethylene (TFE), fluorinated rubber and at least one member secondary battery separator is selected from the group consisting of polyimide. The method of claim 12,
The binder polymer is at least one secondary battery separator selected from the group consisting of PVdF, TFE and polyimide. The method of claim 12,
The binder polymer is a phenolic compound including bicalin, luteolin, taxoxyline, mycetin, quercetin, rutin, catechin, epigallocatechin gallate, butein, picethenol, tannic acid, pyrogallic Separation membrane for a secondary battery further comprising at least one of an aqueous or non-aqueous polymer consisting of acid, amylose, amylopectin, xanthan gum, fatty acid. A secondary battery comprising the secondary battery separator according to any one of claims 1 to 14.

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