Insulating composition, electrode comprising insulating layer derived therefrom, and secondary battery comprising same

Abstract

An insulating composition according to an embodiment of the present invention comprises a solid portion at a content of 35 wt % or less with respect to the total weight thereof, wherein the solid portion comprises inorganic particles, a polymer material, and clay, the clay has positive and negative charges distributed in the particles and is included in an amount of 0.01 parts by weight to 10 parts by weight with respect to 100 parts by weight of the solid portion, and the polymer material comprises a functional group-containing polymer. The insulating composition exhibits low viscosity at high shear rates and high viscosity at low shear rates, thereby providing excellent coating processability. During formation of an insulating layer, sliding portions are minimized so that the insulation width can be formed narrowly, thereby preventing a problem in which the positive / negative electrode capacity ratio may be reversed due to sliding portions.

Description

Insulating composition, electrode comprising an insulating layer derived therefrom, and secondary battery comprising the same

[0001] In this specification, a technology relating to an insulating composition, an electrode including an insulating layer derived therefrom, and a secondary battery including the same is disclosed.

[0002]

[0003] With the recent technological development and increasing demand for mobile devices, the demand for batteries as an energy source is rapidly increasing. Consequently, diverse research is being conducted to develop batteries that can meet diverse needs. In particular, active research is being conducted on secondary batteries, which possess high energy density and excellent lifespan and cycling characteristics, as power sources for these devices.

[0004] A secondary battery includes a positive electrode containing a positive electrode active material capable of insertion / de-insertion of lithium ions, a negative electrode containing a negative electrode active material capable of insertion / de-insertion of lithium ions, and a separator and an electrolyte interposed between the positive electrode and the negative electrode. The positive electrode and the negative electrode have a structure in which an electrode active material layer is formed on one surface of an electrode current collector or on the positive electrode, and recently, a technology for forming an insulating layer on the outer surface of the electrode active material layer is being developed to improve the stability of the electrode. By forming an insulating layer on the outer surface of the electrode active material layer, the electrode active material layer can be protected from heat generated during electrode operation, and insulation between electrodes can be improved.

[0005] Conventional electrode insulating layers have typically been formed using binders with insulating properties. However, binders have poor heat resistance. Therefore, conventional binder-based insulating layers exhibit reduced adhesive strength under high-temperature conditions associated with battery operation, thereby compromising battery safety. To address this issue, a technique has been proposed to improve the heat resistance of the insulating layer by adding inorganic particles to an electrode insulating coating composition.

[0006] Meanwhile, electrode insulating layers, in addition to their basic safety-enhancing effects and functions, such as preventing short circuits between electrodes, can also minimize sliding of the side portions that inevitably occur during the electrode slurry coating and drying processes. To minimize sliding, methods for controlling the coating process during the insulating composition and slurry coating are being developed. However, controlling process conditions has limitations and requires significant costs, such as equipment replacement and process modifications. Therefore, the development of an insulating composition that can address these issues is necessary.

[0007]

[0008] In one aspect of the present specification, it is an object to provide an insulating composition capable of improving viscosity characteristics by including a functional group-containing polymer and a clay having positive and negative charges distributed in a specific amount in an insulating composition having a solid content below a specific value.

[0009] In another aspect of the present specification, by including an insulating layer derived from the insulating composition, the insulating layer is easy to implement in thickness, so that the loading amount is high, and even when the electrode composite layer is thick, the insulating width is thin and the formation of a sliding portion is minimized, providing an electrode.

[0010] In another aspect of the present specification, by including the electrode, an insulating layer is stably formed while having a high loading amount, thereby providing a secondary battery capable of securing a high capacity and preventing the problem of the positive / negative capacity ratio (N / P ratio) being reversed due to a sliding portion.

[0011]

[0012] [1] In one aspect, an insulating composition is provided, which comprises a solid content of 35 wt% or less based on the total weight, wherein the solid content comprises inorganic particles, a polymer material, and clay, wherein the clay has positive and negative charges distributed within the particles and is comprised of 0.01 to 10 wt% based on 100 wt% of the solid content, and wherein the polymer material comprises a functional group-containing polymer.

[0013] [2] In the above [1], the solid content may be included in an amount of 27 wt% or less based on the total weight of the insulating composition.

[0014] [3] In the above [1] and / or [2], the clay may be included in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of solid content.

[0015] [4] In at least one of the above [1] to [3], the inorganic particles may be included in an amount of 60 to 92 parts by weight based on 100 parts by weight of the solid content, and the polymer material may be included in an amount of 5 to 20 parts by weight based on 100 parts by weight of the solid content.

[0016] [5] In at least one of the above [1] to [4], the inorganic particles may include at least one selected from the group consisting of boehmite (AlOOH), aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), alumina (Al2O3), and zirconia (ZrO2).

[0017] [6] In at least one of the above [1] to [5], the functional group-containing polymer may include at least one functional group selected from the group consisting of a carboxyl group, an ester group, an amide group, and a cyano group.

[0018] [7] In at least one of the above [1] to [6], the polymer material further comprises a binder, and the binder may comprise at least one selected from the group consisting of a styrene-butadiene copolymer, an acrylate styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, an acrylonitrile-butadiene-styrene copolymer, an acrylic rubber, a butyl rubber, a fluoroelastomer, a polytetrafluoroethylene, a polyethylene, a polypropylene, an ethylene propylene copolymer, a polyethylene oxide, a polyvinylpyrrolidone, a polyepichlorohydrin, a polyphosphazene, a polyacrylonitrile, a polystyrene, an ethylene propylene diene copolymer, a polyvinylpyridine, a chlorosulfonated polyethylene, a latex, a polyester resin, an acrylic resin, a phenol resin, an epoxy resin, and a polyvinyl alcohol.

[0019] [8] In at least one of the above [1] to [7], the clay may be a plate-shaped particle, and may include at least one selected from the group consisting of hectorite, saponite, and bentonite.

[0020] [9] In at least one of the above [1] to [8], the insulating composition may further include an aqueous solvent.

[0021]

[0010] In at least one of the above [1] to [9], the insulating composition may further include a hydrophobic additive, and the hydrophobic additive may include activated carbon.

[0022]

[0023]

[0011] In another aspect, an electrode is provided, comprising: a current collector; an electrode composite layer provided on a portion of the current collector and including an electrode active material; and an insulating layer disposed adjacent to the electrode composite layer but on a current collector not provided with the electrode composite layer; wherein the insulating layer includes inorganic particles, a polymer material, and clay, wherein the clay has positive and negative charges distributed within the particles and is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the insulating layer, and wherein the polymer material includes a functional group-containing polymer.

[0024]

[0012] In the above

[0011] , the electrode active material is a negative electrode active material, and the negative electrode active material may include at least one selected from the group consisting of a silicon-based active material, a carbon-based active material, and a silicon-carbon composite active material.

[0025]

[0013] In the above

[0011] and / or

[0012] , the electrode composite layer may further include a binder and a conductive material.

[0026]

[0027]

[0014] In another aspect, a secondary battery including at least one electrode among

[0011] to

[0013] is provided.

[0028]

[0029] An insulating composition according to one aspect of the present disclosure can improve viscosity characteristics by including a functional group-containing polymer and clay having positive and negative charges distributed in an insulating composition having a solid content below a specific value, thereby improving storage stability and coating processability of the composition.

[0030] According to another aspect of the present specification, an electrode includes an insulating layer derived from the insulating composition, so that the insulating layer can be easily implemented in a thick form, and thus the loading amount is high, so that even when the electrode composite layer is thick, the insulating width is thin and the formation of a sliding portion is minimized, enabling high loading.

[0031] A secondary battery according to another aspect of the present specification includes the electrode, thereby forming an insulating layer stably while having a high loading capacity, thereby securing a high capacity and preventing the problem of the positive / negative electrode capacity ratio (N / P ratio) being reversed due to a sliding portion.

[0032]

[0033] The advantages and features of the present invention, and the methods for achieving them, will become clearer with reference to the embodiments described in detail below together with the accompanying drawings. However, the present invention is not limited to the embodiments disclosed below and may be implemented in various different forms. These embodiments are provided only to ensure that the disclosure of the present invention is complete and to fully inform those skilled in the art of the scope of the invention, and the present invention is defined only by the scope of the claims. Like reference numerals designate like elements throughout the specification.

[0034] Unless otherwise defined, all terms (including technical and scientific terms) used herein may be used in their common sense to those of ordinary skill in the art to which the present invention pertains. Furthermore, terms defined in commonly used dictionaries are not to be interpreted ideally or excessively unless explicitly and specifically defined otherwise.

[0035] The terminology used herein is for the purpose of describing embodiments and is not intended to limit the present invention. In this specification, singular forms also include plural forms, unless specifically stated otherwise. As used herein, the terms "comprises" and / or "comprising" do not exclude the presence or addition of one or more other components in addition to the components mentioned.

[0036] In this specification, when it is said that a part includes a certain component, this does not mean that other components are excluded, but rather that other components may be included, unless specifically stated otherwise.

[0037] In this specification, the description of “A and / or B” means A, or B, or A and B.

[0038] In this specification, “%” means weight percent unless explicitly indicated otherwise.

[0039] In this specification, D 50 In the particle size distribution curve of silver particles, it means the particle size corresponding to 50% of the volume accumulation, and D 90 In the particle size distribution curve of silver particles, it means the particle size corresponding to 90% of the accumulated number. The above D 50 and D 90 For example, it can be measured using the laser diffraction method. The laser diffraction method can generally measure particle diameters from the submicron range to several mm, and can obtain results with high reproducibility and high resolution.

[0040]

[0041] In this specification, each of the insulating composition, electrode, and secondary battery includes at least one of the technical features and / or technical configurations described below, and these technical features and / or technical configurations can be combined in various ways.

[0042]

[0043] 1. Insulating composition according to the first aspect

[0044] An insulating composition according to the first aspect is an insulating composition comprising a solid content of 35 wt% or less based on the total weight, wherein the solid content comprises inorganic particles, a polymer material, and clay, wherein the clay has positive and negative charges distributed within the particles and is comprised of 0.01 to 10 wt% based on 100 wt% of the solid content, and the polymer material may be characterized in that it comprises a functional group-containing polymer.

[0045]

[0046] In the first aspect, the insulating composition is characterized by having a solid content of 35 wt% or less, and preferably, 33 wt% or less, 30 wt% or less, 27 wt% or less, or 25 wt% or less.

[0047] The solid content in the insulating composition can be a factor that determines the viscosity of the composition, and can be determined by considering the wet thickness when forming the insulating layer, the ease of dispensing from the coating nozzle, and the content of components to be included in the insulating layer. However, if the solid content is higher than the above range, the nozzle may become clogged when the insulating composition is dispensed from the coating nozzle, or the coating thickness of the insulating layer may not be uniform. Therefore, it is preferable to lower the solid content within the above range as much as possible.

[0048]

[0049] In the first aspect, the insulating composition is characterized by including inorganic particles, clay, and a polymer material. In general, the insulating composition can be arranged on the non-coated portion of the side of the electrode active material layer on the electrode current collector, thereby preventing short circuits between electrodes and unnecessary side reactions at the electrode terminals, and for this purpose, inorganic particles are included, and the inorganic particles are appropriately arranged in the insulating layer, and a polymer material is included for maintaining the same. The polymer material may be included in one or more types to impart various functions to the composition, and for example, a binder that functions to impart binding strength and a polymer material that functions to implement wet thickness by increasing viscosity may be added.

[0050] The insulating composition above is designed to have a lower viscosity by lowering the solid content for ease of dispensing from a coating device during coating and uniformity of insulating layer thickness formation. Furthermore, efforts are needed to increase the viscosity to increase the thickness in a wet state after dispensing from a coating device onto a current collector. To this end, the insulating composition may include a polymer material, and the polymer material is characterized by including a functional group-containing polymer.

[0051] The functional group-containing polymer can function to increase the viscosity of the composition, which can be expected to have the advantage of facilitating wet thickness implementation. However, when the functional group-containing polymer is added, the viscosity increases, and this increase in viscosity can cause problems when the insulating composition is dispensed from the coating equipment.

[0052] Accordingly, the inventors of the present invention propose an insulating composition including clay having positive and negative charges distributed within particles in order to implement viscosity characteristics that can maintain the viscosity at as low a level as possible when the composition is discharged from a coating device and maintain the viscosity at as high a level as possible on a current collector after being discharged from the device.

[0053]

[0054] 1) Clay

[0055] In the first aspect, the clay is characterized in that positive and negative charges are distributed within the particles and is included in the insulating composition in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the solid content.

[0056] The above clay is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the solid content. However, if it is included in an amount less than 0.01 parts by weight, it is difficult to exhibit an effect capable of crosslinking a functional group-containing polymer through bonding by electrical attraction, which will be described later, and thus it is difficult to achieve viscosity characteristics. In addition, if it is added in an amount greater than 10 parts by weight, even if the bonding by electrical attraction is dissociated at a high shear rate, the bonding may be reactivated as the shear force is relieved and changed to low shear, which may cause a problem of a rapid increase in viscosity. In addition, the insulating composition may be discharged after being mixed in the coating equipment, which may cause a problem of clogging of the pipe. Therefore, the clay may be preferably included in an amount of 0.05 parts by weight or more, 0.08 parts by weight or more, or 0.1 parts by weight or more, and may also be included in an amount of 9 parts by weight or less, 8 parts by weight or less, 7 parts by weight or less, 6 parts by weight or less, or 5 parts by weight or less.

[0057] The above clay may be a plate-shaped particle, and may include, for example, a 2:1 type clay mineral having a ratio of tetrahedral sheets to octahedral sheets of 2:1, and may be a layer in which two or more layers are laminated in a form in which an octahedral sheet is positioned between tetrahedral sheets. The above clay may have a positive charge (δ+) distributed on the edge portion of the plate on the particle surface, and a negative charge (δ-) distributed on the surface portion inside the edge portion of the plate.

[0058] As positive and negative charges are distributed in the clay, when included with a polymer material, for example, a functional group-containing polymer, the carboxyl groups can be ionized due to the separated and distributed charges within the clay particles, and the separated cations can be adsorbed into the interlayer spaces of the platelets, which can also contain water.

[0059] Since the above-mentioned carboxyl group is an anion, it can form a bond by the positive charge distributed at the edge of the plate and the electric attraction, such as a polar interaction or dipole interaction. This bond can exert an effect similar to a cross-linking bond between functional group-containing polymer molecules, and the bonding and dissociation can freely and reversibly occur depending on the external force applied, and through this reversible dissociation and bonding, a desired level of viscosity can be achieved depending on the shear rate. This interaction between the clay and the functional group-containing polymer can be expressed more strongly when the solid content is 35 wt% or less, and when the solid content is relatively low, the reversible reaction of bonding and dissociation can be performed more smoothly.

[0060] The above clay has an average particle size (D 50) may be 10 nm to 2 ㎛, preferably 20 nm or more, 25 nm or more, or 30 nm or more, and 1.8 ㎛ or less, 1.7 ㎛ or less, or 1.5 ㎛ or less. In this case, the average particle diameter D50 may be measured through the laser diffraction method for a dispersion liquid in which 1.1 wt% of the clay is dispersed in water.

[0061] The clay may be, for example, a smectite-based clay mineral. The clay may preferably include at least one selected from the group consisting of hectorite, saponite, and bentonite. In addition, the hectorite, saponite, and bentonite may be commercially available as laponite (BYK), smecton (sumecton, kunimine industries), and cloisite (BYK), respectively.

[0062]

[0063] 2) Polymer materials

[0064] In the first aspect, the insulating composition comprises a polymer material, wherein the polymer material comprises a functional group-containing polymer. The functional group-containing polymer may comprise at least one functional group selected from the group consisting of a carboxyl group, an ester group, an amide group, and a cyano group.

[0065] For example, the functional group-containing polymer may include at least one selected from the group consisting of carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. Preferably, the functional group-containing polymer may include at least one selected from the group consisting of carboxymethyl cellulose, hydroxypropylmethyl cellulose, and hydroxypropyl cellulose. The functional group-containing polymer may function as a thickener in the insulating composition.

[0066] The polymer material may further include a binder, and as a representative example, the binder may include at least one selected from the group consisting of styrene-butadiene copolymer, acrylate styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, acrylic rubber, butyl rubber, fluoroelastomer, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, acrylic resin, phenol resin, epoxy resin, and polyvinyl alcohol. Among these, it is preferable to apply a styrene-butadiene copolymer, an acrylate styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, an acrylonitrile-butadiene-styrene copolymer, or a mixture thereof.

[0067] The above polymer material may be included in the insulating composition in an amount of 5 to 20 parts by weight based on 100 parts by weight of solid content, preferably 6 parts by weight or more, 7 parts by weight or more, 8 parts by weight or more, 9 parts by weight or more, or 10 parts by weight or more, and further, 18 parts by weight or less, 16 parts by weight or less, 15 parts by weight or less, or 14 parts by weight or less.

[0068] The above content may be the total weight of the binder and the functional group-containing polymer, and the functional group-containing polymer may be 1 part by weight or more, 2 parts by weight or more, or 3 parts by weight or more, and may also be 8 parts by weight or less, 7 parts by weight or less, or 6 parts by weight or less, based on 100 parts by weight of the solid content. Within the above range, the thickening effect of the functional group-containing polymer may have an appropriate effect on the insulating composition, and if it is out of the range, viscosity control at a high shear rate or a low shear rate may be difficult. In this case, the binder may include the remainder excluding the content of the functional group-containing polymer within the content range of the polymer material.

[0069]

[0070] 3) Inorganic particles

[0071] In the first aspect, the insulating composition is characterized in that it contains inorganic particles.

[0072] The above insulating composition is placed on the side of the active material layer on the electrode non-conductive portion to prevent potentially hazardous events such as thermal runaway or explosion caused by a short circuit between electrodes when the battery malfunctions. Therefore, it may be essential to have properties that do not melt and withstand high temperatures. To address this issue, the insulating layer, which previously used only a binder, has been improved by including inorganic particles with heat-resistant properties in the insulating layer.

[0073] The above-mentioned inorganic particles can, most importantly, perform a function of increasing heat resistance. Since the above-mentioned inorganic particles do not soften or melt even at high temperatures, such as temperatures exceeding 900°C, when such inorganic particles are included in the insulating layer, electrode insulation can be maintained even at very high temperatures.

[0074] The above inorganic particles may include, for example, at least one selected from the group consisting of boehmite (AlOOH), aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), alumina (Al2O3), and zirconia (ZrO2). Preferably, boehmite may be applied, and in this case, there is an advantage in that better heat resistance can be secured while having excellent dispersibility, so that heat resistance characteristics can be uniformly obtained throughout the entire insulating layer, and the ability to maintain adhesiveness even after electrolyte impregnation can be excellent due to the presence of hydroxyl groups included in the above inorganic particles.

[0075] D of the above inorganic particles 50 The D of the inorganic particles may be 0.1 ㎛ to 5.0 ㎛, preferably 0.1 ㎛ to 3.0 ㎛, more preferably 0.3 ㎛ or more, 0.5 ㎛ or more, and also 2.0 ㎛ or less, 1.5 ㎛ or less. 50 When the above range is satisfied, the occurrence of agglomeration of the inorganic particles within the insulating coating composition during the formation of the insulating layer is minimized, thereby forming an insulating layer having a uniform thickness and surface.

[0076] The inorganic particles may be included in an amount of 60 to 92 parts by weight, based on 100 parts by weight of the solid content in the insulating composition, preferably 65 parts by weight or more, 70 parts by weight or more, or 75 parts by weight or more, and further 91 parts by weight or less, 90 parts by weight or less, 89 parts by weight or less, or 88 parts by weight or less. When the content of the inorganic particles satisfies the above range, the agglomeration of the inorganic particles in the insulating composition is minimized when forming the insulating layer, so that the viscosity of the composition can be appropriately maintained, and an insulating layer having a uniform thickness and surface can be formed.

[0077]

[0078] 4) Hydrophobic additives

[0079] In the first aspect, the insulating composition may further include the hydrophobic additive, and the hydrophobic additive may include activated carbon.

[0080] The above hydrophobic additive has a specific surface area (BET) of 700 m 2 / g to 3,000 m 2 / g range, preferably 750 m 2 / g or more, 800 m 2 / g or more, 850 m 2 / g or more, 900 m 2 / g or more, or 950 m 2 / g or more, and 2,700 m 2 / g or less, 2,500 m 2 / g or less, 2,200 m 2 / g or less, 2,000 m 2 / g or less, 1,800 m 2 / g or less, or 1,500 m 2 / g or less. When the specific surface area of ​​the hydrophobic additive satisfies the above range, the problem of the maximum height becoming higher than that of the active material layer when forming the insulating layer can be prevented.

[0081] The hydrophobic additive may be a carbon-based additive, such as activated carbon. The activated carbon may be composed of graphite and have a porous structure connected by carbon-carbon bonds. The activated carbon has a porous structure with a large specific surface area, and can achieve high surface tension even in small quantities by adsorbing SBR binders and the like within the pores.

[0082] The above hydrophobic additive has a specific surface area of ​​700 m 2 / g to 1,500 m 2 / g of the first additive; and a specific surface area of ​​1,500 m 2 / g to 3,000 m 2 / g may include at least one of the second additives. For example, the first additive may have a specific surface area of ​​700 m 2 / g to 1,500 m 2 / g, preferably 1,000 m 2 / g to 1,250 m 2 / g can be, and the average particle size (D 50 ) may be 25 ㎛ to 60 ㎛, preferably 35 ㎛ to 45 ㎛. In addition, the second additive may have a specific surface area of ​​1,500 m 2 / g to 2,200 m 2 / g, preferably 1,600 m 2 / g to 2,100 m 2 / g, and the average particle size (D 50 ) may be 2 ㎛ to 10 ㎛, preferably 3 ㎛ to 6 ㎛.

[0083] There are several methods that can be applied to increase the hydrophobicity of the hydrophobic additive. For example, hydrophobicity can be increased by using activated carbon with a high specific surface area, performing heat treatment, for example, at a temperature of 500°C, or using acid or base treatment.

[0084]

[0085] 5) Others

[0086] The insulating composition may include a solvent, and the solvent may be an aqueous solvent, for example, the aqueous solvent may be water (H2O).

[0087] The insulating composition may be substantially non-conductive. For example, the insulating composition may have a volume resistance of 1,000 Ω·cm or more, or in the range of 1,000 Ω·cm to 5,000 Ω·cm.

[0088] The insulating composition may have a surface tension of 70 mN / m or more. The insulating composition may have a high surface tension when it contains an appropriate amount of a hydrophobic additive, for example, 70 mN / m to 100 mN / m, or 70 mN / m to 80 mN / m.

[0089]

[0090] 2. Insulating composition according to the second aspect

[0091] An insulating composition according to the second aspect is an insulating composition comprising a solid content of 35 wt% or less based on the total weight, an insulating composition comprising a solid content of 35 wt% or less based on the total weight, wherein the solid content includes inorganic particles and polymeric materials, and has a shear rate of 0.0251 s. -1 The viscosity is 4,000 mPa·s or more and the shear rate is 251 s -1 It can be characterized by a viscosity of 400 mPa·s or less.

[0092] The viscosity according to the above shear rate may be measured at room temperature, for example, 20°C to 30°C, 21°C to 27°C, 22°C to 25°C, 23°C to 25°C, and preferably 23°C.

[0093] The insulating composition according to the second aspect may have substantially the same components as the insulating composition according to the first aspect, and the differences from the insulating composition according to the first aspect will be described below, and unless otherwise stated, the insulating composition may share the characteristics and operational effects with the insulating composition according to the first aspect.

[0094]

[0095] In the second aspect, the insulating composition comprises inorganic particles and polymeric materials as the solid content, and has a shear rate of 0.0251 s. -1 The viscosity is 4,000 mPa·s or more and the shear rate is 251 s -1 It is characterized by a viscosity of 400 mPa·s or less.

[0096] The insulating composition is characterized in that the viscosity can be controlled within a specific range depending on the shear rate. In the case of the insulating composition, the viscosity must be low in coating equipment to facilitate dispensing and improve processability, and when forming an insulating layer on a current collector after dispensing, the viscosity must be high to maintain a thick wet thickness and form a narrow insulation width. The insulating composition according to the second aspect reflects such characteristics, and has a shear rate of 0.0251 s. -1 The viscosity is 4,000 mPa·s or more and the shear rate is 251 s -1 By satisfying that the viscosity is 400 mPa·s or less, it is possible to achieve both the advantages of ease of dispensing during coating and implementation of a thick and narrow insulating layer as described above.

[0097] The insulating composition preferably has a shear rate of 0.0251 s -1The viscosity may be 4,300 mPa·s or more, 4,500 mPa·s or more, 4,700 mPa·s or more, 4,900 mPa·s or more, 5,100 mPa·s or more, or 5,200 mPa·s or more, and may also be 200,000 mPa·s or less, 180,000 mPa·s or less, or 175,000 mPa·s or less. In addition, the insulating composition preferably has a shear rate of 251 s -1 The viscosity may be 395 mPa·s or less, 390 mPa·s or less, 380 mPa·s or less, 375 mPa·s or less, or 370 mPa·s or less, and may also be 70 mPa·s or more, 80 mPa·s or more, 90 mPa·s or more, 100 mPa·s or more, or 120 mPa·s or more. The viscosity range according to the above shear rate is a range for implementing the coating processability (ease of discharge from the coating nozzle) and the wet thickness of the insulation layer, and it is preferable to control the types and contents of the components included in the insulation composition and the solid content to satisfy this.

[0098] The insulating composition further comprises clay, wherein the clay has positive and negative charges distributed within the particles and is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the solid content, and the polymer material may include a functional group-containing polymer. The characteristics of the clay and the polymer material are the same as those of the insulating composition according to the first aspect.

[0099] The viscosity range depending on the shear rate of the insulating composition can be determined according to the solid content in the composition, the type and content of the functional group-containing polymer, and whether clay is added and the content, as described in the insulating composition according to the first aspect.

[0100] The above insulating composition can induce bonding and dissociation by electrical attraction between the two substances by injecting clay in which both positive and negative charges are distributed within the particles, and by simultaneously injecting a functional group-containing polymer that can be ionized into cations and anions. For example, at a high shear rate, the external force applied to the functional group-containing polymer and clay in the composition is strong, so that the bonding by electrical attraction is dissociated, and thus a relatively low viscosity can be maintained. In addition, at a low shear rate, the external force applied is not strong enough to dissociate the bonding by electrical attraction between the two substances, so that they can function as if they are cross-linked with each other, and thus a high viscosity can be maintained.

[0101]

[0102] 3. Electrode according to the third aspect

[0103] According to a third aspect, an electrode is provided, comprising: a current collector; an electrode composite layer provided on a portion of the current collector and including an electrode active material; and an insulating layer disposed adjacent to the electrode composite layer but on a current collector not provided with the electrode composite layer; wherein the insulating layer includes inorganic particles, a polymer material, and clay, wherein the clay has positive and negative charges distributed within the particles and is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of the insulating layer, and wherein the polymer material includes a functional group-containing polymer.

[0104] The electrode is characterized in that it comprises an insulating layer derived from an insulating composition according to the first aspect and / or the second aspect, wherein the insulating layer may have substantially the same components and contents of the solid components of the insulating composition.

[0105] The types, characteristics and contents of the materials constituting the insulating layer, such as inorganic particles, polymer materials and clay, may be substantially the same as those described in the insulating composition according to the first aspect and / or the second aspect, and thus a detailed description thereof is omitted.

[0106] According to a third aspect, the electrode composite layer includes an electrode active material and may further include a binder and a conductive material. The electrode active material may be a positive electrode active material or a negative electrode active material, and preferably, a negative electrode active material, and the negative electrode active material may include at least one selected from the group consisting of a silicon-based active material, a carbon-based active material, and a silicon-carbon composite active material.

[0107]

[0108] 1) Cathode

[0109] When the above electrode is a negative electrode, it includes a negative electrode current collector and a negative electrode composite layer positioned on the negative electrode current collector, and the negative electrode composite layer may include a negative electrode active material, a binder, and a conductive material.

[0110] The above negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, stainless steel, aluminum, nickel, titanium, heat-treated carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., aluminum-cadmium alloy, etc. can be used.

[0111] The negative electrode current collector may typically have a thickness of 3 μm to 500 μm, and preferably may have a thickness of 300 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less. Fine unevenness may be formed on the surface of the current collector to strengthen the bonding strength with the negative electrode active material.

[0112] The above-described negative electrode current collector can be used in various forms, such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. In addition, the above-described negative electrode current collector can be a metal foil, and a composite film in which a metal is deposited on at least one surface of a resin can be used.

[0113] The negative active material may be a compound capable of reversible intercalation and deintercalation of lithium, and examples thereof include carbon materials such as artificial graphite, natural graphite, Kish graphite, pyrolytic carbon, meso-carbon microbeads, mesophase pitches, petroleum or coal tar pitch derived cokes, mesophase pitch based carbon fiber, graphitized carbon fiber, amorphous carbon, soft carbon, or hardened carbon; (semi-)metallic materials capable of alloying with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; SiO b (0 <b≤2), SnO2, 바나듐 산화물, 리튬 바나듐 산화물과 같이 리튬을 도프 및 탈도프할 수 있는 (준)금속 산화물 재료; Si-C 복합체 또는 Sn-C 복합체과 같은 이종 복합 재료; 또는 금속 리튬 박막 등을 들 수 있으며, 이들 중 어느 하나 또는 둘 이상의 혼합물이 사용될 수 있다.

[0114] Preferably, the negative electrode active material may include at least one selected from the group consisting of a silicon-based active material, a carbon-based active material, and a silicon-carbon composite active material, and more preferably, the carbon-based active material may include at least one selected from the group consisting of artificial graphite, natural graphite, softened carbon, and hardened carbon, and the silicon-based active material may include pure Si particles and / or SiO.b (0 <b≤2)를 포함할 수 있으며, 상기 실리콘-탄소 복합계 활물질은 Si-C 복합체를 포함할 수 있다. 또한, 상기 음극 활물질은 상기한 물질들 중에서 2 이상이 혼합된 혼합 활물질이 적용될 수도 있다.

[0115] The above negative electrode active material may be included in an amount of 60 wt% to 99 wt% based on the total weight of the negative electrode active material layer, preferably 70 wt% or more, 80 wt% or more, 85 wt% or more, or 90 wt% or more, and further may be included in an amount of 98 wt% or less, 97 wt% or less, or 95 wt% or less.

[0116] The above binder is a component that assists in bonding between the conductive material, the active material, and the current collector, and can typically be added in an amount of 0.1 wt% to 10 wt% based on the total weight of the negative electrode active material layer, and can be included in an amount of 0.2 wt% or more, 0.3 wt% or more, or 0.5 wt% or more, and can also be included in an amount of 8 wt% or less, or 5 wt% or less. Examples of such binders may include at least one selected from the group consisting of styrene-butadiene copolymers, acrylated styrene-butadiene copolymers, acrylonitrile-butadiene copolymers, acrylonitrile-butadiene-styrene copolymers, acrylic rubber, butyl rubber, fluoroelastomer, polytetrafluoroethylene, polyethylene, polypropylene, ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resins, acrylic resins, phenol resins, epoxy resins, and polyvinyl alcohol. Among these, it may include at least one selected from the group consisting of styrene-butadiene copolymer, acrylate styrene-butadiene copolymer, acrylonitrile-butadiene copolymer, acrylonitrile-butadiene-styrene copolymer, carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, and cyanoethyl sucrose. Preferably, it is preferable to apply carboxymethyl cellulose, hydroxypropylmethyl cellulose, hydroxypropyl cellulose, or a mixture thereof.

[0117] The conductive agent is a component for further improving the conductivity of the negative electrode active material, and may be added in an amount of 10 wt% or less, preferably 5 wt% or less, 3 wt% or less, 2 wt% or less, or 1 wt% or less, based on the total weight of the negative electrode composite layer, and may also be included in an amount of 0.01 wt% or more, 0.05 wt% or more, 0.08 wt% or more, 0.1 wt% or more, or 0.3 wt% or more. The conductive agent is not particularly limited as long as it has conductivity and does not cause a chemical change in the battery, and examples thereof include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; conductive fibers such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives.

[0118] The above negative electrode composite layer can be manufactured by applying and drying a negative electrode slurry composition prepared by dissolving or dispersing a negative electrode active material, and optionally a binder and a conductive material in a solvent, on a negative electrode current collector, or by casting the negative electrode slurry composition on a separate support, and then laminating the obtained film by peeling it off from the support on a negative electrode current collector.

[0119]

[0120] 2) Bipolar

[0121] When the above electrode is a positive electrode, it includes a positive electrode current collector and a positive electrode composite layer positioned on the positive electrode current collector, and the positive electrode composite layer may include a positive electrode active material, a binder, and a conductive material.

[0122] The positive electrode current collector may be any conductive material that does not induce chemical changes in the battery, and is not particularly limited thereto. For example, the positive electrode current collector may be made of stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface-treated with carbon, nickel, titanium, silver, or the like.

[0123] The above-described positive electrode current collector may typically have a thickness of 3 μm to 500 μm, and preferably may have a thickness of 300 μm or less, 200 μm or less, 100 μm or less, or 80 μm or less. Fine unevenness may be formed on the surface of the positive electrode current collector to strengthen the bonding strength with the positive electrode active material.

[0124] The positive electrode current collector may be used in various forms, such as a film, sheet, foil, net, porous body, foam, or non-woven fabric. In addition, the positive electrode current collector may be a metal foil, or a composite film in which a metal is deposited on at least one surface of a resin.

[0125] The above positive electrode active material may include a lithium transition metal compound containing at least one selected from the group consisting of nickel (Ni), cobalt (Co), manganese (Mn), and iron (Fe), which is a compound capable of reversible intercalation and deintercalation of lithium.

[0126] For example, it may include a lithium metal oxide containing lithium and one or more metals such as cobalt, manganese, nickel or aluminum. More specifically, the lithium metal oxide may include a lithium-manganese oxide (e.g., LiMnO2, LiMn2O4, etc.), a lithium-cobalt oxide (e.g., LiCoO2, etc.), a lithium-nickel oxide (e.g., LiNiO2, etc.), a lithium-nickel-manganese oxide (e.g., LiNi 1-Y Mn Y O2(0 <Y<1), LiMn 2-Z Ni ZO4(0<Z<2) etc.), lithium-nickel-cobalt oxides (e.g., LiNi 1-Y1 Co Y1 O2(0 <Y1<1) 등), 리튬-망간-코발트계 산화물(예를 들면, LiCo 1-Y2 Mn Y2 O2(0 <Y2<1), LiMn 2-Z1 Co Z1 O4(0<Z1<2) etc.), lithium-nickel-manganese-cobalt oxides (e.g., Li(Ni p Co q Mn r )O2(0<p<1, 0<q<1, 0<r<1, p+q+r=1) or Li(Ni p1 Co q1 Mn r1 )2O4(0<p1<2, 0<q1<2, 0<r1<2, p1+q1+r1=2) etc.), or lithium-nickel-cobalt-transition metal(M) oxides (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (M is selected from the group consisting of Al, Fe, V, Cr, Ti, Ta, Mg and Mo, and p2, q2, r2 and s2 are atomic fractions of independent elements, respectively, 0<p2<1, 0<q2<1, 0<r2<1, 0<s2<1, p2+q2+r2+s2=1), etc.), lithium iron phosphate (e.g., Li 1+a Fe 1-x M x (PO 4-b )X b (M is at least one selected from Al, Mg, and Ti, X is at least one selected from F, S, and N, -0.5≤a≤0.5, 0≤x≤0.5, 0≤b≤0.1), and any one or two or more compounds thereof may be included.

[0127] The above-mentioned positive electrode active material may comprise 80 wt% to 99 wt% based on the total weight of the positive electrode composite layer, preferably 85 wt% or more, 88 wt% or more, 90 wt% or more, 92 wt% or more, 93 wt% or more, or 95 wt% or more, and may also be comprised at 98.5 wt% or less, 98 wt% or less, or 97.5 wt% or less. When comprised within the above range, it may be preferable in terms of both increasing the capacity and energy density of the electrode and optimizing the functions of the conductive material and binder, which are auxiliary materials.

[0128] The conductive agent is a component for further improving the conductivity of the positive electrode active material. The conductive agent is not particularly limited as long as it has conductivity without causing a chemical change in the battery. For example, carbon black powder such as acetylene black, Ketjen black, channel black, furnace black, lamp black, or thermal black; graphite powder such as natural graphite, artificial graphite, or graphite with a highly developed crystal structure; conductive fibers such as carbon fibers or metal fibers; conductive powders such as fluorinated carbon powder, aluminum powder, or nickel powder; conductive whiskers such as zinc oxide or potassium titanate; conductive metal oxides such as titanium oxide; and conductive materials such as polyphenylene derivatives can be used. Specifically, the conductive agent may include at least one selected from the group consisting of activated carbon, graphite, carbon black, and carbon nanotubes (CNTs) for uniform mixing of the conductive agent and improvement of conductivity.

[0129] The conductive agent may be included in an amount of 0.1 wt% to 10.0 wt% based on the total weight of the positive electrode composite layer. Preferably, it may be included in an amount of 0.2 wt% or more, 0.3 wt% or more, 0.5 wt% or more, or 0.7 wt% or more, and may also be included in an amount of 8.0 wt% or less, 6.0 wt% or less, or 5.0 wt% or less. The more the conductive agent is added, the more advantageous it is for conductive path formation. However, the capacity may be reduced due to a relative decrease in the amount of active material, and it is not easy to control the amount added due to dispersion issues. However, by optimizing the dispersibility within the above range, the effect of conductive path formation can be maximized, so it may be desirable to apply the conductive agent within the above range.

[0130] The above binder serves to improve the adhesion between positive electrode active material particles and the adhesion between the positive electrode active material and the current collector. Specific examples include polyvinylidene fluoride (PVDF), polyvinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylalcohol, polyacrylonitrile, polymethyl methacrylate, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene polymer (EPDM), sulfonated-EPDM, styrene butadiene rubber (SBR), fluoroelastomer, polyacrylic acid, and polymers in which hydrogens of these are substituted with Li, Na, or Ca, or various copolymers thereof, and one of these may be used alone or a mixture of two or more thereof.

[0131] The binder may be included in an amount of 0.1 wt% to 10.0 wt% based on the total weight of the positive electrode composite layer. Preferably, it may be included in an amount of 0.2 wt% or more, 0.3 wt% or more, 0.5 wt% or more, or 0.7 wt% or more, and may also be included in an amount of 8.0 wt% or less, 6.0 wt% or less, or 5.0 wt% or less.

[0132]

[0133] 3) Method for manufacturing electrodes

[0134] An electrode according to a third aspect can be manufactured by the following manufacturing method. The manufacturing method includes a step (S1a) of applying an electrode slurry containing an electrode active material to a portion of a current collector; a step (S1b) of applying an insulating composition on a current collector adjacent to a region where the electrode slurry is applied but not where the electrode slurry is applied; and a step (S2) of drying the electrode slurry and insulating composition applied on the current collector to form an electrode composite layer and an insulating layer. In this case, the insulating composition may be according to the first aspect and / or the second aspect.

[0135] The above S1a step can be manufactured according to a conventional electrode manufacturing method. Specifically, it can be manufactured by dissolving or dispersing an electrode active material, a binder, and a conductive agent in a solvent, applying an electrode slurry onto an electrode current collector, and then drying and rolling.

[0136] The above S1b step can also be manufactured according to a conventional insulating layer manufacturing method. For example, the insulating composition can be manufactured by mixing inorganic particles and a binder in a solvent and performing a dispersion process. Specifically, each component of the composition is mixed by placing the particles in a solvent and mixing them. At this time, the mixing can be performed using mixing devices well known in the art, such as a homo mixer, but is not limited thereto.

[0137] The composition that has undergone the above mixing process is dispersed by milling. The milling can be performed using a ball mill, a bead mill, or a basket mill, and more specifically, can be performed using a bead mill. Meanwhile, the degree of dispersion of the composition can be controlled by controlling milling conditions, such as the number of times the composition is passed through the ball mill, bead mill, or basket mill (hereinafter, "number of passes"), the rotor speed, etc.

[0138] The above steps S1a and S1b may be performed simultaneously, or sequentially before the drying process of step S2 is performed. Specifically, a coater having multiple nozzles may be used to simultaneously apply electrode slurry and insulating composition onto a current collector, and the process may be designed so that electrode slurry coating equipment and insulating composition coating equipment are sequentially arranged in the direction of movement of the conveyor so that both coatings can be performed before drying.

[0139] The above S2 step is a drying process, and conditions generally applied in this technical field can be applied, for example, 50°C to 300°C, preferably 60°C or higher, or 70°C or higher, and further, drying can be performed at a temperature of 250°C or lower, 200°C or lower, or 150°C or lower.

[0140] The above electrode slurry may have a solid content of 40 wt% to 80 wt%, and the solid content may be appropriately controlled depending on whether the electrode slurry is a positive electrode slurry or a negative electrode slurry, and may preferably be appropriately controlled within a range of 45 wt% to 75 wt%. When the solid content is controlled within the above range, mixing of the electrode slurry and the insulating composition may not occur, and the problem of the insulating composition penetrating into the interface between the electrode composite layer and the current collector may not occur.

[0141]

[0142] 4. Electrode according to the fourth aspect

[0143] According to the fourth aspect, the present invention comprises: a current collector; an electrode composite layer provided on a portion of the current collector and including an electrode active material; and an insulating layer disposed adjacent to the electrode composite layer but on a current collector not provided with the electrode composite layer; wherein the electrode composite layer has a loading amount of 400 mg / 25 cm 2 Above, the insulating layer is provided with an electrode having a maximum width of 2.0 mm or less.

[0144] The above electrode has the advantage of being able to increase the loading amount despite the narrow width of the insulating layer, thereby enabling high capacity and high energy density to be expected. This may be realized due to the insulating layer being derived from the insulating composition according to the first aspect and / or the second aspect, and the insulating layer may have substantially the same solid content as the component and content of the component of the insulating composition.

[0145] When forming an insulating layer using the insulating composition according to the first aspect and / or the second aspect, the width of the insulating layer may be at most 2.0 mm or less, and preferably, 1.9 mm or less, 1.8 mm or less, 1.7 mm or less, 1.6 mm or less, or 1.5 mm or less.

[0146] This narrow width formation is possible while simultaneously allowing for a thick wetted layer, resulting in a uniform and thick insulating layer. Therefore, the formation of this insulating layer has the advantage of functioning as a dam for the electrode slurry, thereby minimizing sliding areas.

[0147] If the sliding portion is excessively formed, the capacity ratio (N / P ratio) of the positive and negative electrodes may be reversed, which may cause the negative electrode to not be able to accept lithium ions transferred from the positive electrode, resulting in lithium precipitation. If this precipitation continues, a short circuit may occur, potentially leading to a risk of fire.

[0148] However, since the electrode according to the fourth aspect can minimize the sliding part through the insulating layer, the above problem can be prevented. In addition, even if the loading amount of the electrode composite layer is increased to make it a little thicker, the formation of the sliding part as described above can be minimized, so that high capacity can be achieved, and since the width of the insulating layer is narrow, the phenomenon of interference occurring during electrode tab welding can be prevented, so that the possibility of short circuit can be significantly reduced. This is because the loading amount is 400 mg / 25 cm 2 This effect can be said to be due to the fact that it is possible to implement an electrode with an insulating layer width of up to 2.0 mm.

[0149] When the maximum value of the insulation layer width is greater than 2.0 mm, there is a problem that the capacity may be reduced, and when manufacturing a single stack cell by stacking unit cells, welding is performed between electrode tabs. At this time, electrode tabs arranged at various heights are gathered into one place and welded, and in this process, if the width of the insulation layer is wide, the electrode tab may fold and cause a disconnection problem. In other words, the electrode according to the fourth aspect can have the effect of preventing the disconnection problem of the electrode tab along with the high-loading and high-energy-density characteristics because the loading amount is greater than a specific value and the maximum value of the insulation layer width is less than 2.0 mm.

[0150] Additionally, the insulating layer may have an average thickness (Dave) of 10 μm to 100 μm. Preferably, it may be 15 μm or more, 20 μm or more, 25 μm or more, or 30 μm or more, and further, it may be 90 μm or less, 80 μm or less, 70 μm or less, 60 μm or less, or 50 μm or less.

[0151] The materials constituting the insulating layer, such as the types, characteristics and contents of inorganic particles, polymer materials and clay, may be substantially the same as those described in the insulating composition according to the first aspect and / or the second aspect, and the technical characteristics of the components, types and contents of the electrode composite layer constituting the electrode, the current collector, the positive electrode and the negative electrode, etc. may be substantially the same as those described in the electrode according to the third aspect, so a specific description thereof is omitted, and for matters not specifically described, the description of the electrode according to the third aspect may be applied as is unless otherwise stated.

[0152]

[0153] 5. Secondary battery according to the fifth aspect

[0154] A secondary battery according to the fifth aspect may include an electrode assembly in which a plurality of electrodes and separators are alternately stacked, and at least one of the electrodes is an electrode according to the third aspect and / or the fourth aspect.

[0155] Since the above electrodes are the same as those described above, a detailed description will be omitted, and only the remaining components will be described in detail below.

[0156] The secondary battery may be a lithium secondary battery or a sodium secondary battery, and may be an all-solid-state secondary battery or a non-aqueous electrolyte secondary battery. If the secondary battery is a non-aqueous electrolyte secondary battery, the secondary battery may optionally further include a battery container that houses an electrode assembly, which is a collection of unit cells including the positive electrode, the negative electrode, and the separator, and a sealing member that seals the battery container. In addition, if the secondary battery is an all-solid-state secondary battery, a solid electrolyte membrane may be applied instead of the separator.

[0157]

[0158] In the above secondary battery, the separator separates the negative electrode and the positive electrode and provides a passage for lithium ions to move. Any separator commonly used in secondary batteries can be used without special restrictions, and in particular, one having low resistance to ion movement of the electrolyte and excellent electrolyte moisture retention capacity is preferable. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene / butene copolymer, an ethylene / hexene copolymer, and an ethylene / methacrylate copolymer, or a laminated structure of two or more layers thereof, may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high-melting-point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, a coated separator containing a ceramic component or a polymer material may be used to secure heat resistance or mechanical strength, and may optionally be used in a single-layer or multi-layer structure.

[0159] The electrolyte used in the secondary battery may include, but is not limited to, an organic liquid electrolyte or an inorganic liquid electrolyte that can be used in the manufacture of a secondary battery.

[0160] The electrolyte may include an organic solvent and a lithium salt. The organic solvent may be used without particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, the organic solvent may include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonate solvents such as dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R represents a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms and may include a double-bonded aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes can be used. Among these, a carbonate solvent is preferable, and a mixture of a cyclic carbonate (e.g., ethylene carbonate or propylene carbonate, etc.) having high ionic conductivity and high dielectric constant that can improve the charge / discharge performance of the battery and a linear carbonate compound having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, or diethyl carbonate, etc.) is more preferable.

[0161] The above lithium salt can be used without any special limitation as long as it is a compound that can provide lithium ions used in secondary batteries. Specifically, the anion of the above lithium salt is F - , Cl - , Br - , I - , NO3 - , N(CN)2 - , BF4 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be at least one selected from the group consisting of, and the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAl04, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. It is preferable to use the concentration of the lithium salt within the range of 0.1 to 2.0 M. When the concentration of the lithium salt is within the above range, the electrolyte can exhibit excellent electrolyte performance because it has appropriate conductivity and viscosity, and lithium ions can move effectively.

[0162] In addition to the electrolyte components, the electrolyte may further include one or more additives, such as haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ethers, ethylene diamine, n-glyme, hexaphosphoric acid triamide, nitrobenzene derivatives, sulfur, quinone imine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, or aluminum trichloride, for the purpose of improving the life characteristics of the battery, suppressing battery capacity decrease, and improving the discharge capacity of the battery. At this time, the additives may be included in an amount of 0.1 to 5 wt% based on the total weight of the electrolyte.

[0163] If the secondary battery is an all-solid-state secondary battery, the applicable solid electrolyte may be selected from a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, or a molten inorganic electrolyte, and the inorganic electrolyte may be a sulfide-based solid electrolyte or an oxide-based solid electrolyte. The specific type of compound may be appropriately applied according to what is known in the industry.

[0164]

[0165] Since the above secondary battery stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, it can be useful in portable devices such as mobile phones, laptop computers, and digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs).

[0166] In another aspect, a battery box comprising the secondary battery as a unit cell may be provided. The battery box may include a plurality of battery cells, which are unit cells, and may include packaging that accommodates the plurality of battery cells. Here, the battery box may be, for example, a battery module or a battery pack.

[0167] In addition, in another aspect, an electrical device including the battery box may be provided. The battery box may be used as a power source for the electrical device. The electrical device may be, for example, one or more medium- to large-sized devices, such as a power tool; an electric vehicle (EV), a hybrid electric vehicle, and an electric vehicle (PHEV), including a plug-in hybrid electric vehicle; or a power storage system.

[0168]

[0169] Example

[0170] Hereinafter, the present invention will be described in more detail by way of examples. However, the following examples are intended to illustrate the present invention and are not intended to limit the scope of the present invention solely to these examples.

[0171]

[0172] Examples 1 to 6 and Comparative Examples 1 to 3

[0173] Carboxymethyl cellulose (CMC), a functional group-containing polymer, and clay in water as an aqueous solvent, with an average particle size (D 50 ) 25 nm hectorite (laponite, BYK) was added and mixed in a homomixer (Dispermat LC, VMA) at 2,500 rpm for 5 minutes, and then D 50 This 1.0 μm, specific surface area is about 5.0 m 2 / g to 8.5 m 2 / g of boehmite (product name: BP10, manufacturer: KEATON), styrene-butadiene copolymer (SBR) and activated carbon were added to the mixture and mixed at 2,500 rpm for 25 minutes.

[0174] Next, an insulating coating composition was manufactured by performing a dispersion process using a bead mill (product name: LS-1, manufacturer: Netsch) at a rotor speed of 3300 RPM, a 1-pass discharge amount of 540 g / min, and a pass number of 8.

[0175] The contents of the components applied in each example and comparative example (parts by weight based on 100 parts by weight of solid content) are as described in Table 1 below. The SBR and activated carbon were added in amounts of 8 parts by weight and 0.2 parts by weight, respectively, and the amount of water, which is an aqueous solvent, was adjusted so that the solid content was as described in Table 1 below.

[0176] Inorganic particle functional group containing polymer (CMC) clay solid content (wt%) Example 187.7 4.0 0.123 Example 287.4 4.0 0.417 Example 386.1 4.6 1.114 Example 486.8 4.0 1.011 Example 582.8 4.0 5.09 Example 679.8 4.0 8.05 Comparative Example 188.3 3.5 0 27 Comparative Example 277.3 4.0 10.54 Comparative Example 390.8 0 1.011

[0177] Experimental Example 1: Evaluation of Insulating Compositions

[0178] For the insulating compositions manufactured in Examples 1 to 6 and Comparative Examples 1 to 3, the constant temperature viscosity and shear rate were 251 s. -1 and 0.0251 s -1 The viscosity and surface tension were measured using the following method and are shown in Table 2 below.

[0179] 1) Constant temperature viscosity (cP): Using a temperature-compensated viscometer, when the viscosity was 10,000 cP or less, 4.2 ml of each composition was used as a sample, and the constant temperature viscosity was measured at room temperature (approximately 25°C) with an SC4-16 spindle in an SC4-8RP chamber at 12 rpm for 3 minutes. When the viscosity was 8,000 cP to 30,000 cP, 16.1 ml of each composition was used as a sample, and the constant temperature viscosity was measured with an SC4-25 spindle in an SC4-13RP chamber at 16 rpm for 3 minutes.

[0180] 2) Viscosity (mPa·s) by shear rate: Each of the above compositions was put as a sample into a rheometer (HR-20 Rheometer, TA) with a Cup&Bob accessory, and viscosity data by shear rate were obtained at room temperature (approximately 23°C) (1 st descending value), with a shear rate of 251 s -1 and 0.0251 s -1 The viscosity values ​​in are shown in Table 2 below.

[0181] 3) Surface tension (mN / m): Measurement was performed using DCA-200 (Dynamic Contract Angle System, SEO Co.) under the following conditions: Motor speed: 15 / Probe type: Ring / Immersion Depth: 4 / Surface Detact Weight: 0.005 / Stabilization Time: 5.

[0182] Constant temperature viscosity 0.0251 s -1 Viscosity 251 s -1Viscosity Surface Tension Example 15,1808,87037077.2 Example 24,73015,60026079.2 Example 36,80033,42024082.9 Example 42,2805,25012075.4 Example 54,460109,40015084.1 Example 63,530171,91011086.3 Comparative Example 13,4003,20041072.1 Comparative Example 24,700226,00014086.2 Comparative Example 31,2402,31011071.1

[0183] Referring to Table 2 above, in the case of Comparative Example 1 with a solid content of 27 wt%, despite the high solid content, it can be confirmed that the viscosity was low even at a low shear rate due to the absence of clay, and the viscosity was measured to be relatively high at a high shear rate. In addition, Comparative Example 2 was a case where clay was excessively added, and it can be confirmed that a problem of a rapid increase in viscosity occurred at low shear, and Comparative Example 3 did not add a functional group-containing polymer, so it can be indirectly confirmed that the viscosity at low shear was low, making it difficult to implement a narrow insulation width. However, in the case of Examples 1 to 6, clay was added, and despite the extremely low solid content, the viscosity at low shear rate was greatly increased due to the relative increasing effect of CMC in the solid content and the effect of adding clay, so it can be expected that it will be easy to implement a thick wet thickness of the insulation layer, and the viscosity was rather lowered at a high shear rate, so it can be inferred that the processability is also excellent.

[0184]

[0185] Experimental Example 2: Evaluation of the Width of the Insulation Layer

[0186] Using the insulating compositions manufactured in Examples 1 to 6 and Comparative Examples 1 to 3, simultaneous coating was performed on a copper current collector together with a cathode slurry using equipment having multiple coating nozzles in a slot die, thereby manufacturing an electrode. At this time, the loading amount of the cathode composite layer was 400 mg / 25 cm2 The average thickness was set to be approximately 180 ㎛, and the thickness of the insulation layer was set to be 150 ㎛ in wet thickness and 15 ㎛ in dry thickness, and the maximum value of the insulation layer width was measured.

[0187] Insulation layer width (mm) Example 11.5 Example 21.3 Example 31.3 Example 42.0 Example 51.2 Example 61.2 Comparative Example 12.5 Comparative Example 2 - Comparative Example 32.5

[0188] Referring to Table 3 above, it can be confirmed that Examples 1 to 6 were formed with an insulation width smaller than 2.0 mm, but Comparative Examples 1 and 3 were formed with an insulation width wider than 2.0 mm, as expected from the results in Table 1 above, and it can be confirmed that high-loading, high-energy-density electrodes could not be implemented indirectly. In the case of Comparative Example 2, the high shear viscosity was low, so mixing inside the equipment was easy, but when the insulating liquid was discharged to the outside through the die inside the equipment, there was a part where the shear force was low, and in this part, the viscosity increased rapidly, causing a problem of clogging the discharge port, so that insulating coating could not be performed. In other words, it can be confirmed from the results above that by including a functional group-containing polymer and controlling the content of clay, the viscosity of the insulating composition can be excellently controlled according to the shear rate, and through this, a narrow insulation width can be implemented.

Claims

1. An insulating composition containing a solid content of 35 wt% or less based on the total weight, The above solid content includes inorganic particles, polymer materials and clay, The above clay has positive and negative charges distributed within the particles, and is included in an amount of 0.01 to 10 parts by weight based on 100 parts by weight of solid content. An insulating composition comprising a polymer material containing a functional group.

2. In paragraph 1, An insulating composition in which the above solid content is included in an amount of 27 wt% or less based on the total weight of the insulating composition.

3. In paragraph 1, An insulating composition, wherein the clay is included in an amount of 0.05 to 5 parts by weight based on 100 parts by weight of solid content.

4. In paragraph 1, The above inorganic particles are included in an amount of 60 to 92 parts by weight based on 100 parts by weight of solid content, An insulating composition, wherein the polymer material is included in an amount of 5 to 20 parts by weight based on 100 parts by weight of solid content.

5. In paragraph 1, An insulating composition, wherein the inorganic particles include at least one selected from the group consisting of boehmite (AlOOH), aluminum hydroxide (Al(OH)3), magnesium hydroxide (Mg(OH)2), alumina (Al2O3), and zirconia (ZrO2).

6. In paragraph 1, An insulating composition wherein the functional group-containing polymer comprises at least one functional group selected from the group consisting of a carboxyl group, an ester group, an amide group, and a cyano group.

7. In paragraph 1, The above polymer material further comprises a binder, An insulating composition comprising at least one selected from the group consisting of a styrene-butadiene copolymer, an acrylate styrene-butadiene copolymer, an acrylonitrile-butadiene copolymer, an acrylonitrile-butadiene-styrene copolymer, an acrylic rubber, a butyl rubber, a fluoroelastomer, polytetrafluoroethylene, polyethylene, polypropylene, an ethylene propylene copolymer, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, an ethylene propylene diene copolymer, polyvinylpyridine, a chlorosulfonated polyethylene, latex, a polyester resin, an acrylic resin, a phenol resin, an epoxy resin, and polyvinyl alcohol.

8. In paragraph 1, An insulating composition wherein the clay is a plate-shaped particle and comprises at least one selected from the group consisting of hectorite, saponite, and bentonite.

9. In paragraph 1, An insulating composition further comprising an aqueous solvent.

10. In paragraph 1, The above insulating composition further comprises a hydrophobic additive, An insulating composition wherein the hydrophobic additive comprises activated carbon.

11. A current collector; an electrode composite layer provided on a portion of the current collector and including an electrode active material; and an insulating layer disposed adjacent to the electrode composite layer but on a current collector not provided with the electrode composite layer; The above insulating layer comprises inorganic particles, polymer material and clay, The above clay has positive and negative charges distributed within the particles, and is included in an amount of 0.01 to 10 parts by weight relative to 100 parts by weight of the insulating layer. An electrode, wherein the polymer material comprises a functional group-containing polymer.

12. In paragraph 11, The above electrode active material is a negative electrode active material, An electrode wherein the negative electrode active material comprises at least one selected from the group consisting of a silicon-based active material, a carbon-based active material, and a silicon-carbon composite active material.

13. In paragraph 11, An electrode, wherein the electrode composite layer further comprises a binder and a conductive material.

14. A secondary battery comprising the electrode described in Article 11.