KR102648386B1 - Method of manufacturing for electrode-separator complex comprising multi-layer structure of inorganic layers and electrode-separator complex manufactured thereby - Google Patents

Abstract

The present invention relates to a method of manufacturing a separator composite electrode having a multi-layered inorganic material layer and a separator composite electrode resulting therefrom. By forming a multi-layer inorganic material layer that acts as an insulating layer, safety is improved due to the absence of a separator substrate, and battery capacity is improved. A method of manufacturing a separator composite electrode that does not decrease compared to existing batteries and a separator composite electrode resulting therefrom are provided.

Description

Method of manufacturing a separator composite electrode comprising an inorganic layer having a multi-layer structure and a separator composite electrode resulting therefrom

The present invention relates to a method of manufacturing a separator composite electrode including an inorganic layer with a multi-layer structure and a separator composite electrode resulting therefrom. Specifically, it includes a first inorganic layer containing first inorganic particles with a diameter larger than the pore size of the unit electrode electrode active material layer, and a second inorganic layer containing second inorganic particles with a smaller diameter than the diameter of the first inorganic particles. It relates to a method of manufacturing a separator composite electrode and a separator composite electrode resulting therefrom.

Among the components of a secondary battery, the separator serves to isolate the anode and cathode, prevent electrical short circuit between the two electrodes, and allow electrolyte and ions to pass through. Although the separator itself does not participate in the electrochemical reaction of the secondary battery, it has a significant impact on the performance and safety of the secondary battery due to physical properties such as wettability to the electrolyte solution, degree of porosity, and thermal shrinkage rate.

Polyolefin-based porous substrates are often used as separators for secondary batteries. Since the above porous substrate undergoes thermal contraction at high temperatures, it does not properly perform its role of isolating the anode and cathode. As a result, safety issues, such as secondary batteries short-circuiting or batteries igniting or exploding, have continued to be raised.

In order to compensate for the shortcomings of the porous substrate, a coating layer is added to one or both sides of the porous substrate, and various materials that can compensate for the shortcomings of the porous substrate are added to the coating layer or a method of changing the physical properties of the coating layer is used. Metal oxides such as alumina (Al ₂ O ₃ ) or aluminum hydroxide (Al(OH) ₃ ) are added as inorganic substances to the coating layer to suppress heat shrinkage or improve heat resistance of the separator.

Coating layers containing inorganic materials have the disadvantage of weak adhesion to electrodes. Additionally, since a coating layer is added to one or both sides of the porous substrate, there is a disadvantage that the portion of the secondary battery that does not participate in the chemical reaction increases.

In order to improve the shortcomings of these separators, a separator composite electrode was proposed that functions as a conventional separator by forming an inorganic coating layer on the electrode active material layer. The electrode assembly using the separator composite electrode does not have a separate porous substrate, so there is no risk of heat shrinkage and resulting short circuit, and it also has the advantage of minimizing the parts of the secondary battery that do not participate in chemical reactions.

Figure 1 is a schematic diagram of a conventional separator composite electrode. A conventional separator composite electrode is formed by directly applying or coating an inorganic material on the electrode active material layer 20 or by bonding an inorganic material layer 30 previously formed on the electrode active material layer 20. An electrode active material layer 20 is applied to one side of the current collector 10, and an inorganic material layer 30 is applied to the uppermost layer.

The diameter of the particles of the inorganic material layer 30 of a conventional separator composite electrode as shown in FIG. 1 is often smaller than the pores of the electrode active material layer 20 formed on the electrode. Although small-sized inorganic particles were used to serve as a separator, the particles of the inorganic material layer 30 may block the pores of the electrode active material layer 20, thereby increasing the resistance of the battery. Additionally, the binder that adheres the inorganic material layer may block the pores of the electrode active material layer 20 formed on the electrode. When the resistance of the battery increases as described above, the problem occurs that the battery capacity decreases and the lifespan of the battery is shortened.

Patent Document 1 has an inorganic particle layer composed of several layers, but this is a multi-layer structure that functions as an inorganic coating layer, and the structure for not blocking the pores of the electrode is not recognized.

Patent Document 2 also relates to an electrode having a current collector, an active material layer, and an inorganic material layer. Patent Document 2 uses ceramic fillers of various sizes and shapes to increase the ionic conductivity of the ceramic separator itself by providing an inorganic material layer with two or more particle diameters, but this is to improve the performance of the separator itself and to improve the performance of the battery. They are not aware of blocking pores or deteriorating battery performance due to this.

In order to improve the safety of secondary batteries that are closely used in daily life and to develop secondary batteries that can meet the demand for high capacity and high density, it is necessary to provide a separator composite electrode that does not block the pores of the electrode and a secondary battery using the same. There is.

Republic of Korea Patent Publication No. 2016-0112266 (2016.09.28) ('Patent Document 1') Republic of Korea Patent Publication No. 2008-0082289 (2008.09.11) ('Patent Document 2')

The present invention is intended to solve the above problems, in a separator composite electrode in which an inorganic material layer with a multi-layer structure serving as a separator is attached to one side of the electrode without a separate separator, and the pores of the electrode active material layer are not blocked, thereby improving battery performance. The purpose is to provide a method of manufacturing a separator composite electrode that not only has no degradation but also has low resistance. In addition, the present invention aims to provide a separator composite electrode that has excellent safety even at high temperatures since there is no separate separator and the multi-layered inorganic material layer serving as the separator does not include a polymer base.

In order to achieve this purpose, the method for manufacturing a separator composite electrode provided by the present invention includes the steps of S1) preparing a first inorganic layer slurry containing first inorganic particles and a first binder and having a viscosity of 5000 cP to 20000 cP, S2) Preparing a second inorganic layer slurry containing second inorganic particles and a second binder, S3) preparing a unit electrode having an electrode active material layer formed on at least one surface of the electrode current collector, and S4) the unit of step S3) A step of forming a first inorganic layer composed of the first inorganic slurry on at least one surface of the electrode active material layer, and forming a second inorganic layer composed of the second inorganic slurry on the first inorganic layer, wherein the first inorganic layer consists of the first inorganic slurry. The diameter of the inorganic particle is larger than the pore size of the unit electrode electrode active material layer, the diameter of the second inorganic particle is smaller than the diameter of the first inorganic particle, and steps S1) to S3) are performed in any order. Alternatively, two or more may occur simultaneously.

The step S1) includes preparing a first inorganic solution by mixing the first inorganic particles and a first solvent; Preparing a first binder solution by mixing the first binder polymer and the first solvent; And it may include mixing the first inorganic solution and the first binder solution to prepare a first inorganic layer slurry.

The step S2) includes preparing a second inorganic solution by mixing the second inorganic particles and a second solvent; Preparing a second binder solution by mixing the second binder polymer and the second solvent; And it may include mixing the second inorganic solution and the second binder solution to prepare a second inorganic layer slurry.

The first inorganic particle may have a diameter of 500 nm to 3 ㎚, and the second inorganic particle may have a diameter of 20 nm to 300 nm.

The first inorganic layer slurry in step S1) and/or the second inorganic layer slurry in step S2) may further include a dispersant.

The type of the dispersant is not limited as long as it is a material that can be generally used in batteries. As an example, the dispersant may be a mixture of one or more types selected from the group consisting of acrylic copolymers. Additionally, the dispersant may be a mixture of one or more types selected from the group consisting of acids.

The second inorganic particles may be a mixture of particles with different diameters.

The second inorganic particles may include sequentially mixing the second inorganic particles in descending order of diameter in step S2).

When mixing the second inorganic particles, the step of mixing a dispersant may be further included between the step of mixing particles with small particle diameters and the step of mixing particles with large particle diameters.

The first inorganic layer slurry may have a higher viscosity than the second inorganic layer slurry.

The viscosity of the second inorganic layer slurry may be 300 cP to 3000 cP.

In step S4), the first inorganic layer slurry and the second inorganic layer slurry may be simultaneously coated on at least one surface of the unit electrode electrode active material layer.

In step S4), the first inorganic material layer slurry is applied to at least one surface of the unit electrode electrode active material layer to form the first inorganic material layer, and the second inorganic material layer slurry is applied on the first inorganic material layer. A second inorganic layer can be formed.

The first inorganic layer and/or the second inorganic layer may further include a step of lamination after formation.

The lamination may be performed at 50°C to 200°C.

The first inorganic particles and/or the second inorganic particles may include at least one of AlOOH, Al(OH) ₃ , and Al ₂ O ₃ .

The second inorganic particle may be surface modified.

The first binder polymer and the second binder polymer are the same material and may differ only in molecular weight or copolymer composition ratio.

The second binder polymer may have a different chemical composition from the first binder polymer.

The molecular structure of the second binder polymer may be branched.

The thickness of the first inorganic layer and/or the second inorganic layer may each be 3 ㎛ or more and less than 20 ㎛. Preferably, the thickness of the first inorganic layer and/or the second inorganic layer may be 3 μm or more and 10 μm or less.

The total thickness of the inorganic layer, which is the sum of the thickness of the first inorganic layer and the thickness of the second inorganic layer, may be less than 30 μm. Preferably, the thickness of the entire inorganic layer may be 20㎛ or less.

The first inorganic layer and the second inorganic layer may have the same thickness.

The present invention may be a separator composite electrode manufactured according to any one of the above-mentioned manufacturing methods.

The present invention also provides an electrode assembly including the separator composite electrode.

The present invention may also include the step of stacking at least one layer of the separator composite electrode and laminating them to manufacture a unit cell.

The unit cell may be capable of being used by charging and discharging more than 20 times.

In the present invention, one or two or more non-conflicting configurations among the above configurations can be selected and combined.

The method of manufacturing a separator composite electrode according to the present invention forms a first inorganic layer and a second inorganic layer that differ in the diameter and nature of the inorganic particles and the nature of the slurry forming the inorganic layer, and the existing electrode is formed by the first inorganic layer. It maintains the pores of the electrode, ensures that the pores of the electrode are formed uniformly by the second inorganic layer, and plays a role in preventing electrical short-circuiting.

The separator composite electrode according to the present invention has excellent safety even at high temperatures because it does not have a porous polymer substrate and uses an inorganic material that undergoes an endothermic reaction. In addition, because the first inorganic material layer allows the unit electrode electrode active material layer to maintain existing pores, an electrode assembly with lower resistance than a conventional separator composite electrode can be provided. As the resistance of the electrode assembly decreases, the capacity and lifespan of the battery improve.

The present invention is also more effective in preventing electrical short circuits than conventional separator composite electrodes by controlling the pore size of the second inorganic layer. In theory, if the pores of the second inorganic layer are reduced to a level that approaches the pore size of the conventional polymer porous substrate, electrical short circuits are prevented to a similar extent as those of the conventional polymer porous substrate, and the durability of the second inorganic layer and the separator composite electrode is improved. It can have an effect.

In addition, since there is no separator substrate, the manufacturing method is simpler than the conventional electrode assembly manufacturing method with a separator substrate, so the electrode assembly manufacturing method and lamination process can be simplified.

Figure 1 is a schematic diagram of a conventional separator composite electrode.
Figure 2 is a schematic diagram of a separator composite electrode according to the first embodiment of the present invention.
Figure 3 is a schematic diagram of a separator composite electrode according to a second embodiment of the present invention.
Figure 4 is a schematic diagram of an electrode assembly in which separator composite electrodes are stacked according to the first embodiment of the present invention.
Figure 5 is a schematic diagram of an electrode assembly in which separator composite electrodes are stacked according to a third embodiment of the present invention.
Figure 6 is a schematic diagram of an electrode assembly in which separator composite electrodes are stacked according to a fourth embodiment of the present invention.
Figure 7 is a graph of the capacity maintenance rate after 45 charging and discharging of the comparative examples and examples of the present invention.

Hereinafter, an embodiment in which the present invention can be easily implemented by a person skilled in the art to which the present invention pertains will be described in detail. However, when explaining in detail the operating principle of a preferred embodiment of the present invention, if it is determined that a detailed description of a related known function or configuration may unnecessarily obscure the gist of the present invention, the detailed description will be omitted.

Throughout the specification, when a part is said to be connected to another part, this includes not only cases where it is directly connected, but also cases where it is indirectly connected through another element in between. Additionally, including a certain component does not mean excluding other components unless specifically stated to the contrary, but rather means that other components may be further included.

Hereinafter, the present invention will be described with reference to examples, but this is for easier understanding of the present invention, and the scope of the present invention is not limited thereto.

Hereinafter, the present invention will be described in more detail.

The method of manufacturing a separator composite electrode according to the present invention includes the steps of S1) preparing a first inorganic layer slurry containing first inorganic particles and a first binder and having a viscosity of 5000 cP to 20000 cP, S2) second inorganic particles, second Preparing a second inorganic material layer slurry containing a binder; S3) Preparing a unit electrode having an electrode active material layer formed on at least one surface of the electrode current collector; and S4) At least the electrode active material layer of the unit electrode of step S3) Forming a first inorganic layer composed of the first inorganic slurry on one surface, and a second inorganic layer composed of the second inorganic slurry on the first inorganic layer, wherein the diameter of the first inorganic particles is The pore size of the unit electrode electrode active material layer is larger, the diameter of the second inorganic particle is smaller than the diameter of the first inorganic particle, and steps S1) to S3) may be performed in any order or in two or more steps. It is characterized by the fact that it can be carried out simultaneously.

In step S1), the first inorganic layer slurry may be prepared by mixing the first inorganic particles and the first binder in a first solvent at once. Additionally, mixing the first inorganic particles and a first solvent to prepare a first inorganic solution; Preparing a first binder solution by mixing the first binder polymer and the first solvent; And mixing the first inorganic solution and the first binder solution to prepare the first inorganic layer slurry.

If the first inorganic solution is prepared as described above and then a separately prepared first binder solution is prepared, there is an advantage that it is easier to control the viscosity of the first inorganic layer slurry.

The above method can also be applied when forming the first inorganic layer slurry.

A schematic diagram of a first example of a separator composite electrode manufactured by the manufacturing method according to the present invention is shown in Figure 2.

As shown in Figure 2, the separator composite electrode according to the first embodiment of the present invention includes a unit electrode 250 including an electrode current collector 100 on one side of which an electrode active material layer 200 is formed, and the unit electrode 250 A first inorganic layer 300 and the first inorganic layer ( 300) and may include a second inorganic layer 400 including second inorganic particles with a diameter smaller than the first inorganic particles and a second binder polymer.

The unit electrode 250 is composed of an electrode current collector 100 and an electrode active material layer 200 formed on at least one surface thereof. Figure 2 is an example and includes the electrode active material layer 200 formed on only one side, but the electrode active material layer 200 can be formed on both sides.

Therefore, possible embodiments of the present invention include a unit electrode based on two combinations of electrode active material layers formed on one or both sides of the electrode current collector, and two combinations of an inorganic material layer formed on one or both sides of the unit electrode electrode active material layer. A total of 5 combinations can be formed. Specifically, a combination of two layers according to the present invention formed on each side of the electrode current collector, a combination of two electrode active material layers formed on both sides of the electrode current collector and two inorganic layers formed on each side, and a combination of one inorganic layer formed on both sides. A total of 5 combinations are possible.

The electrode current collector 100 may generally have a thickness of 3㎛ to 500㎛. The electrode current collector 100 can increase the adhesion of the electrode active material by forming fine irregularities on its surface, and can be used in various physical forms such as films, sheets, foils, nets, porous materials, foams, and non-woven fabrics. The material used as the electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery. Both the positive electrode current collector and the negative electrode current collector can be used as the electrode current collector of the present invention.

The positive electrode current collector may be one selected from stainless steel, aluminum, nickel, titanium, and aluminum or stainless steel surface treated with carbon, nickel, titanium, or silver, and aluminum may be preferably used. there is. The negative electrode current collector may be copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or an aluminum-cadmium alloy.

The electrode active material layer 200 may be formed on one or both sides of the electrode current collector 100. The thickness of the electrode active material layer 200 may vary depending on the capacity of the battery and the type of active material. In general, the electrode active material layer 200 formed on one side of the electrode current collector 100 may have a thickness of 3 μm to 500 μm.

When using a positive electrode current collector in the electrode active material layer 200, the positive electrode active materials that can be used include, for example, layered compounds such as lithium nickel oxide (LiNiO2) or compounds substituted with one or more transition metals; Lithium manganese oxide with the formula Li _1+x Mn _2-x O ₄ (where x is 0 to 0.33), LiMnO ₃ , LiMn ₂ O ₃ , LiMnO _{2 ,} etc.; lithium copper oxide (Li ₂ CuO ₂ ); Vanadium oxides such as LiV ₃ O ₈ , LiV ₃ O ₄ , V ₂ O ₅ , and Cu ₂ V ₂ O ₇ ; Ni site type lithium nickel oxide represented by the formula LiNi _1-x M _x O ₂ where 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 where M = Co, Ni, Fe, Cr, Zn or Ta and x = 0.0 to 0.1 or Li ₂ Mn ₃ MO ₈ where M = Fe, Co Lithium manganese complex oxide expressed as Ni, Cu or Zn); LiMn ₂ O ₄ in which part of Li in the chemical formula is replaced with an alkaline earth metal ion; disulfide compounds; It may be composed of Fe ₂ (MoO ₄ ) ₃ , etc., but is not limited to these alone.

When using a negative electrode current collector, negative electrode active materials that can be used include, for example, carbon such as non-graphitizable carbon and graphitic carbon; Li _x Fe ₂ O ₃ (0≤x≤1), _{Li x} WO ₂ (0≤x≤1 _{) , Sn} : Al, B, P, Si, elements of groups 1, 2, and 3 of the periodic table, halogen; metal complex oxides such as 0<x≤1;1≤y≤3;1≤z≤8); lithium metal; lithium alloy; silicon-based alloy; tin-based alloy; 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; It may be composed of Li-Co-Ni based materials, etc.

The electrode active material layer 200 may further include a conductive material and a binder.

The conductive material can typically be added in an amount of 0.1 to 30% by weight based on the total weight of the mixture including the electrode active material. These conductive materials are not particularly limited as long as they have conductivity without causing chemical changes in the battery, and examples include graphite such as natural graphite or artificial graphite; Carbon black such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, and summer black; Conductive fibers such as carbon fiber and metal fiber; Metal powders such as carbon fluoride, aluminum, 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 may be used.

The binder is a component that assists in the bonding of the electrode active material and the conductive material and the bonding to the electrode current collector, and is usually added in an amount of 0.1 to 30% by weight based on the total weight of the mixture containing the electrode active material. Examples of such binders include polyvinylidene fluoride, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, tetrafluoroethylene, and polyethylene. , polypropylene, ethylene-propylene-non-conjugated diene (EPDM), sulfonated EPDM, styrene-butadiene rubber, fluorine rubber, various copolymers, etc.

The electrode active material may have a uniform particle diameter and shape, but may also use various particles having different sizes and shapes. The diameter of the particles of the electrode active material may be 800 nm to 20 μm. Additionally, the particles may have various shapes, such as spherical or rod-shaped.

The electrode current collectors 10 and 100 and the electrode active material layers 20 and 200 are equally applied to the electrode current collectors and electrode active material layers described below.

A first inorganic layer 300 is located on at least one surface of the electrode active material layer 200 of the unit electrode 250, and a second inorganic layer 400 is always located on the upper surface of the first inorganic layer.

The first inorganic layer 300 may include first inorganic particles having a larger diameter than the pore size of the electrode active material layer 200 of the unit electrode 250, and a first binder polymer for fixing them.

Additionally, the second inorganic layer 400 may include second inorganic particles whose diameter is smaller than that of the first inorganic particles, and a second binder polymer for fixing them.

In various possible configurations, the first inorganic layer 300 and the second inorganic layer 400 may exist as separate layers or may be formed as a single layer. When the first inorganic layer 300 and the second inorganic layer 400 exist as one layer, the second inorganic particles 410 are packed in the pores of the first inorganic particles 310, as shown in FIG. 3. It can be configured in the form of: At this time, the weight of the first inorganic particles 310 is 50% to 90% based on the total weight of the inorganic particles, and the weight of the second inorganic particles 410 is 10% to 90% based on the weight of the total inorganic particles. 50% may be included. This is because, when the composition ratio of the second inorganic particles 410 increases, the second inorganic particles 410 with a small particle diameter may enter the pores of the electrode active material layer and increase the resistance. When the inorganic particles are packed as shown in FIG. 3, the first inorganic slurry containing the first inorganic particles 310 and the second inorganic slurry containing the second inorganic particles 410 have similar viscosity. has This is to prevent the second inorganic particles and the second binder polymer from penetrating into the pores of the electrode active material.

When the first inorganic layer 300 and the second inorganic layer 400 exist as separate layers, the first inorganic layer 300 is connected to the unit electrode 250 and the second inorganic layer 400. It can be located in between. At this time, the thickness of the first inorganic layer 300 may be 3 ㎛ or more and less than 20 ㎛. If the first inorganic layer 300 is 20㎛ or more, a problem occurs in which the capacity of the battery decreases by increasing resistance, and if the first inorganic layer 300 is less than 3㎛, the inorganic material intended by the present invention The effect of preventing penetration into the pores of the electrode is not exerted. In addition, the effect of electrical insulation is lost and a short circuit occurs. The thickness of the second inorganic layer 400 may be 3 μm or more and less than 20 μm. As with the first inorganic layer 300, if it is 20㎛ or more, the resistance may increase and the capacity of the battery may decrease, and if it is too thin, the pore size of the entire inorganic layer cannot be reduced, thereby failing to function as an insulating layer. There is a problem that it cannot be performed and may cause a short circuit of the battery.

The first inorganic layer 300 may be formed thinner than the thickness of the second inorganic layer 400. The first inorganic layer 300 is formed to the extent that the second inorganic particles constituting the second inorganic layer 400 do not penetrate into the pores of the electrode, and can serve as a boundary between the unit electrode and the inorganic layer. . If the thickness difference between the first inorganic layer 300 and the second inorganic layer 400 is too large, the second inorganic particles of the second inorganic layer may penetrate into the pores of the unit electrode 250. Therefore, it is preferable that the first inorganic layer 300 has a similar thickness to the second inorganic layer 400, that is, the first inorganic layer 300 has a thickness of 0.6 to 1 times the thickness of the second inorganic layer 400.

If the thickness of the first inorganic layer 300 and the second inorganic layer 400, which correspond to the separator, increases, the capacity maintenance rate according to the charge and discharge cycle may drop rapidly. The preferred thickness of the first inorganic layer 300 and the second inorganic layer 400 is 6 ㎛ or more and 40 ㎛ or less. The thicknesses of the first inorganic layer 300 and the second inorganic layer 400 are equally applied to all embodiments of the present invention.

In order to obtain a separator composite electrode that does not allow inorganic substances to penetrate into the battery, two types of inorganic substances can be used in one layer, or inorganic substances of different sizes, distributions, and shapes can be mixed in multiple layers. However, if the inorganic layer is too thick, the resistance increases, so it is necessary to control the number of layers with the same pore size as the existing separator substrate while preventing inorganic particles from penetrating into the unit electrode. However, it is appropriate to place it in five or fewer floors.

In the case of a multilayer as described above, the average size of pores of all inorganic layers may be 0.01㎛ to 10㎛, and the average porosity may be 10% to 95%. The sum of the thicknesses of the inorganic layers of the multi-layer structure must be at least 6㎛ and less than 40㎛. This is the range that can minimize the resistance of the battery while demonstrating the electrode insulation effect.

The diameter of the first inorganic particle may be larger than the pore size of the unit electrode 250.

The first inorganic layer 300 may serve to prevent inorganic substances from penetrating into the pores of the unit electrode 250. The diameter of the particles of the first inorganic layer 300 may be 500 nm to 3 μm. However, the particle diameter of the first inorganic layer 300 may vary depending on the type of electrode used and the material facing it. Since the pores of an electrode containing a negative electrode active material and a negative electrode current collector are on average within 0.5 μm to 1 μm, the first inorganic layer may have a diameter of 0.5 μm to 8 μm. Additionally, in the case of a positive electrode including a positive electrode active material and a positive electrode current collector, the pores are slightly larger, so the diameter of the first inorganic layer 300 may be 1 μm to 8 μm. This diameter size can be measured using an SEM or Particle Size Analyzer (Product Name: MASTERSIZER 3000; Manufacturer: Malvern).

The first inorganic layer 300 may be formed using inorganic materials with different diameters to form a boundary. Inorganic materials of the same diameter can also be used if they can form a boundary to prevent the second inorganic material 400 from penetrating into the pores of the electrode.

The second inorganic particle may have a diameter smaller than the pore size of the electrode active material layer 200 of the unit electrode 250. The second inorganic particles play a role in preventing short circuit of the battery and maintaining ionic conductivity by ensuring that the inorganic material layer in the separator composite electrode has the same pore size and porosity as that of a conventional separator. The diameter of the second inorganic particle may vary depending on the size of the active material used, but may be 20 nm to 300 nm. More preferably, it may be 20 nm to 150 nm for insulation.

Additionally, the second inorganic particle may be made of two types of inorganic particles of different sizes for insulation purposes. As for the two types of inorganic particles of different sizes, the diameter (D50) of the largest inorganic particle may be 60 nm to 300 nm, and the diameter (D50) of the smallest inorganic particle may be 20 nm to 80 nm.

When using inorganic particles of different sizes as described above, it is preferable to first mix the inorganic particles with a smaller diameter and then mix them in the order of the particles with a larger diameter to form an inorganic layer slurry. At this time, it is more efficient to lower the resistance of the electrode by mixing small-sized inorganic particles and then mixing a dispersant to prevent the small-sized inorganic particles from agglomerating and then mixing large-sized inorganic particles. Inorganic materials with different particle diameters may vary depending on the type, use, composition, etc. of the inorganic material, but the large diameter inorganic particles are in a similar range to the small diameter inorganic particles, that is, 0.5 times to 0.5 times the size of the inorganic particles with the same or smaller diameter. It is desirable to include about 4 times as much.

The first inorganic particle may be in various shapes, such as spherical, oval, dumbbell, terrapor, or amorphous. At this time, a shape that can easily form a boundary on the unit electrode and prevent the second inorganic particles from passing through the first inorganic layer 300, such as a network structure when forming the layer, is desirable. Additionally, additional materials may be introduced to further comprise a single-layer network structure.

The second inorganic particles can have various shapes, but spherical shapes are preferable because the pore size and porosity of the inorganic layer can be adjusted.

The first inorganic layer 300 and the second inorganic layer 400 may function as an insulating layer. The type of the first and second inorganic particles used in the insulating layer is not particularly limited as long as oxidation and/or reduction reactions do not occur in the operating voltage range of the secondary battery. When inorganic particles with ion transport ability are used, battery performance can be improved by increasing ion conductivity within the electrochemical device. When inorganic particles with a high dielectric constant are used as the inorganic particles, the ionic conductivity of the electrolyte solution can be improved by contributing to an increase in the degree of dissociation of electrolyte salts, such as lithium salts, in the liquid electrolyte.

The first inorganic particles and the second inorganic particles may be chemically different substances. The materials for the first inorganic particles and the second inorganic particles can be inorganic particles generally used in separation membranes. In addition, the first inorganic particles and the second inorganic particles according to the present invention may be chemically different materials as described above, but it is also possible to use the same material.

Examples of the first inorganic particles and the second inorganic particles include BaTiO ₃ , SnO ₂ , CeO ₂ , MgO, Mg(OH) ₂ , NiO, CaCO ₃ , CaO, ZnO, ZrO ₂ , Y ₂ O ₃ , SiO ₂ , Al(OH) ₃ , AlOOH, Al ₂ O ₃ , TiO ₂ or mixtures thereof may be mentioned. Among these, it is preferable to use Al(OH) ₃ and AlOOH, which have excellent safety due to their endothermic properties at high temperatures.

The second inorganic particles may be surface-modified particles. This surface modification may be surface treatment to have hydrophilic properties. The surface treatment may be treating the inorganic particles with an acidic solution. The acidic solution may be any material that can impart only hydrophilic properties while maintaining the insulating properties of the inorganic material. The surface treatment may use plasma surface treatment.

The content of the first inorganic particles or the second inorganic particles in the first inorganic layer or the second inorganic layer may be 50 parts by weight to 95 parts by weight based on 100 parts by weight of the total solid content of each first inorganic layer or the second inorganic layer. and may preferably be included in 60 to 95 parts by weight. If the content of the first inorganic particles or the second inorganic particles is less than 50 parts by weight based on 100 parts by weight of the total solid content of the first inorganic layer or the second inorganic layer, the content of the binder is too high and the empty space formed between the inorganic particles is formed. It decreases. For this reason, the pore size and porosity of the inorganic material layer may decrease, thereby reducing battery performance. Additionally, if the inorganic content exceeds 95 parts by weight based on 100 parts by weight of the total solid content of the inorganic material layer, the binder content is too small, which weakens the adhesion between the inorganic materials and may cause an electrical short circuit.

The first binder polymer used in the first inorganic layer 300 serves to allow the first inorganic particles to bond to each other while preventing the second inorganic particles from penetrating the unit electrode through the first inorganic layer. The type of material of the first binder polymer is irrelevant as long as it can provide binding force without affecting the battery. Materials that can be used as the binder include polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, and polymethylmethacrylate. , polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinylacetate, polyethyleneoxide. ), polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl poly. Any one selected from the group consisting of vinyl alcohol (cyanoethylpolyvinylalcohol), cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxymethylcellulose, or a mixture of two or more of these An example is given.

The second binder polymer serves to allow the second inorganic particles to bind to each other. The type of material of the second binder polymer is irrelevant as long as it provides binding force without affecting the battery. For example, the second binder polymer is polyvinylidene fluoride-hexafluoropropylene, polyvinylidene fluoride-trichloroethylene, and polymethylmethacrylate. , polybutylacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinylacetate, polyethylene-co-vinylacetate, polyethyleneoxide. ), polyarylate, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylpullulan, cyanoethyl poly. Any one selected from the group consisting of vinyl alcohol (cyanoethylpolyvinylalcohol), cyanoethylcellulose, cyanoethylsucrose, pullulan, and carboxymethylcellulose, or a mixture of two or more of these You can use it.

The first inorganic layer slurry may have a higher viscosity than the second inorganic layer slurry. The first inorganic layer slurry has a higher viscosity than the second inorganic layer slurry, thereby preventing the binder of the first inorganic layer from penetrating into the unit electrode and preventing the second inorganic particles of the second inorganic layer 400 from penetrating into the unit electrode. It can play a role in preventing it. For example, the first inorganic layer forming slurry containing the first inorganic layer slurry may have a viscosity of 5,000 cP to 20,000 cP, and the second inorganic layer slurry containing the second binder polymer may have a viscosity of 300 cP to 3000 cP. You can have it.

The viscosity of the inorganic layer slurry may vary depending on the binder polymer contained in each inorganic layer.

The first binder polymer is the same material as the second binder polymer and may differ only in molecular weight or copolymer composition ratio. The weight average molecular weight of the first binder polymer may be 600,000 to 1.3 million, and the weight average molecular weight of the second binder polymer may be 200,000 to 1.2 million. The first binder polymer may be 5 to 45 parts by weight based on 100 parts by weight of the total solid content of the first inorganic layer 300. Additionally, the second binder polymer may be 5 to 30 parts by weight based on 100 parts by weight of the total solid content of the second inorganic layer 400.

The first binder polymer may be a material that is chemically different from the second binder polymer. At this time, if the first binder polymer has a higher viscosity than the second binder polymer, there are no restrictions on the material.

The molecular structure of the second binder polymer may be branched. At this time, the first binder polymer may have a linear molecular structure with a higher viscosity than the second binder polymer. However, the above molecular structure is given as an example, and if the viscosity of the first binder polymer is higher than the viscosity of the second binder polymer, the structure can be selected in various ways.

The first binder polymer and the second binder polymer may be selected by varying one or more of the above-mentioned molecular weight, composition ratio, molecular structure, and chemical composition.

In addition, the viscosity of the inorganic material layer slurry may vary depending on the weight ratio of materials such as inorganic particles, binder polymer, and dispersant contained in the inorganic material layer slurry, or may vary depending on the ratio of solid content and solvent contained in the inorganic material layer slurry. .

The electrode current collector can be both a positive electrode current collector and a negative electrode current collector. The electrode active material may be mixed with a binder and applied on the electrode current collector in the form of a slurry. The method of coating the slurry containing the electrode active material (hereinafter referred to as 'electrode slurry') on the current collector is a method of distributing the electrode slurry on the current collector and then uniformly dispersing it using a doctor blade, etc., die Examples include die casting, comma coating, screen printing, and gravure coating. In addition, a method of forming the electrode slurry on a separate substrate and then bonding it to the current collector by pressing or lamination can also be considered. The final coating thickness can be adjusted by adjusting the coating gap, the concentration of the electrode slurry solution, or the number of coatings.

After forming the electrode slurry, it may be dried. The drying process is a process of removing solvent and moisture in the electrode slurry coated on the electrode current collector, and specific conditions such as process process and time may vary depending on the solvent used. For example, the drying process may be performed in a vacuum oven at 50°C to 200°C. Drying methods include, for example, drying with warm air, hot air, or low humidity air, vacuum drying, and drying with irradiation of (far) infrared rays or electron beams. There is no particular limitation on the drying time, but it is usually performed within the range of 30 seconds to 24 hours.

After the drying process, a cooling process may be further included, and the cooling process may be slow cooling to room temperature so that the recrystallization structure of the binder is well formed.

In addition, if necessary, in order to increase the capacity density of the electrode after the drying process and increase the adhesion between the electrode current collector and the electrode active materials, a lamination process is performed in which the unit electrode is passed between two rolls heated at high temperature and compressed to the desired thickness. can do. The lamination process is not particularly limited in the present invention, and a known lamination process (pressing) is possible. For example, it is performed by passing it between rotating rolls or using a flat press.

The drying process, cooling process, and lamination process may be performed after each step S1), S2), and S3), or may be performed only after step S3).

A first slurry containing first inorganic particles and a first binder polymer may be applied to at least one surface of the unit electrode to form a first inorganic layer. The first inorganic particles and the first binder polymer may each be dissolved in a solvent and mixed to form a first inorganic layer slurry. The second slurry layer slurry containing the second inorganic particles and the second binder polymer may also be formed in a similar manner to the first inorganic layer slurry. At this time, a dispersant may be used to ensure that the first inorganic particles and/or the second inorganic particles are evenly dispersed.

The solvent is not limited as long as it has no effect on the battery and is capable of dissolving the binder polymer. Examples of the solvent include acetone, polycarbonate, methylethylketone, tetrahydrofuran, methylene chloride, chloroform, dimethylformamide, Any one of N-methyl-2-pyrrolidone (NMP), cyclohexane, water, or mixtures thereof may be mentioned. The solvent used in the first slurry and the solvent used in the second slurry may be the same or different from each other. The solvent may be used in an amount of 100 to 500 parts by weight based on 100 parts by weight of the solid content of the first slurry in the first slurry, and 200 to 1,000 parts by weight based on 100 parts by weight of the solid content of the first slurry in the second slurry.

The first slurry or a method of applying the first slurry includes distributing it on a current collector and then uniformly dispersing it using a doctor blade, etc., die casting, or comma coating. , screen printing, gravure coating, etc. can be given as examples. In addition, a method of forming the electrode slurry on a separate substrate and then bonding it to the current collector by pressing or lamination can also be considered. The final coating thickness can be adjusted by adjusting the coating gap, the concentration of the electrode slurry solution, or the number of coatings.

In step S4), the first inorganic particles of the first slurry may be applied to form a network structure. When the first inorganic particles of the first slurry form a network structure, the structure can prevent the second inorganic particles from blocking the pores of the unit electrode.

In step S4), the first inorganic layer slurry and the second inorganic layer slurry may be simultaneously coated on at least one surface of the unit electrode.

The case where the first inorganic layer slurry and the second inorganic layer slurry are coated simultaneously includes the case where the second slurry is applied immediately while applying the first slurry.

In step S4), the first inorganic layer slurry may be coated and dried on at least one surface of the unit electrode, and then the second inorganic layer slurry may be coated and dried on the first inorganic layer. At this time, the step of coating and drying each of the first inorganic layer slurry and coating and drying the second inorganic layer slurry may be further included, followed by lamination (pressing).

The lamination (press) may be a method of rolling or flat pressing the separator composite electrode at 20°C to 200°C. Energy density can be increased by reducing the thickness of the separator composite electrode through the lamination (press).

It is preferable that the lamination (press) is performed only after forming the electrode layer or after forming the second inorganic layer.

The present invention may be a separator composite electrode manufactured according to the method for manufacturing a separator composite electrode described above.

In addition, the present invention may be a unit cell manufacturing method including the step of stacking at least two of the above-mentioned separator composite electrodes and laminating them to manufacture a unit cell.

The materials and manufacturing methods mentioned in the above examples can be equally applied to the following examples or comparative examples of the present invention.

The electrode assembly may be formed by stacking a separator composite electrode including a first inorganic layer 300 and a second inorganic layer 400 on one side, as shown in FIG. 4. At this time, the direction of the surface on which the first inorganic layer 300 and the second inorganic layer 400 exist may be formed to face one direction. In FIG. 4, the active material layers 210 and 220 are depicted as being present only on one side of the negative electrode current collector 110 and the positive electrode current collector 120. However, as shown in the drawing, the active material layer may be present on one side or on both sides. .

The electrode assembly is formed by stacking a separator composite electrode in which the first inorganic layer 300 and the second inorganic layer 400 are present in the cross section, as shown in FIG. 4, by placing it between the electrode current collector and the electrode in which only the active material layer is present. You can.

Additionally, as shown in FIG. 5, an electrode assembly may be formed by laminating only the separator composite electrode having the first inorganic layer 300 and the second inorganic layer 400 on both sides.

The present invention may be an electrode assembly including a separator composite electrode according to the above description. The electrode assembly does not include a separator substrate.

In the present invention, the unit electrode 250 includes both a positive electrode unit electrode and a negative electrode unit electrode, and includes electrode active material layers 20 and 200, an inorganic material layer 30, a first inorganic layer 300, and a first inorganic material. The particles 310, the second inorganic layer 400, and the second inorganic particles 410 also include both an anode and a cathode.

Hereinafter, the present invention will be described with reference to examples, but this is for easier understanding of the present invention, and the scope of the present invention is not limited thereto.

<Example 1-1>

S1) Boehmite (first inorganic particle) with a diameter of 500㎚ to 3㎛, NMP solvent (first solvent), and dispersant were added and stirred to prepare a first inorganic mixture, and then PVdF binder (first binder polymer) and NMP solvent (first solvent) are mixed with the first inorganic mixture, so that the slurry particles have a diameter of 500㎚ to 3㎛ based on D50 and a viscosity of 10000cP (solid content about 29% by weight). A first inorganic layer slurry is prepared.

S2) Boehmite (part of the second inorganic particle) with a diameter of 20 nm to 80 nm and surface modified by acid treatment, a dispersant, and boehmite (part of the second inorganic particle) with a diameter of 60 nm to 300 nm, in that order, NMP solvent. The second inorganic mixture solution added and stirred in (second solvent) and the second binder solution mixed with PVdF binder (second binder) in NMP solvent (second solvent) are mixed, so that the diameter of the slurry particles is 150㎚ based on D50. A second inorganic layer slurry having a thickness of 1 μm and a viscosity of 2000 cP (solid content of about 20% by weight) is prepared.

S3) Prepare a negative electrode unit electrode in which a negative electrode active material layer containing graphite is formed on one side of the copper electrode current collector.

S4) The first inorganic layer slurry is applied on the negative electrode active material layer formed on one side of the unit electrode in step S3) and then dried to form a first inorganic layer with a thickness of 5 μm, and on the first inorganic layer The second inorganic layer slurry with a thickness of 5㎛ is applied and dried to form a second inorganic layer.

S5) A unit cell is formed by stacking a unit electrode on which a positive electrode active material layer containing NCM is formed on one side of an aluminum electrode current collector on the second inorganic layer of step S4).

<Example 1-2>

Example 1-2 was formed in the same manner as in Example 1-1, except that unit cells were formed so that the first inorganic layer had a thickness of 10 μm and the second inorganic layer had a thickness of 10 μm.

<Comparative Example 1>

Comparative Example 1 did not go through step S1) of Example 1-1, but applied the second inorganic layer slurry on the negative electrode active material layer of the unit electrode in step S4) and dried it to form a second inorganic material layer slurry with a thickness of 20 μm. The unit cell of Comparative Example 1 was formed through the same steps, except that only two inorganic layers were formed.

<Comparative Example 2>

In Comparative Example 2, the unit cell of Comparative Example 2 was formed through the same steps in Example 1-2, except that the viscosity of the first inorganic layer slurry in step S1) was 2000 cP (solid content about 20% by weight). .

<Experiment 1> - Capacity measurement experiment

The unit cells according to the above examples and comparative examples were charged at 0.3C and discharged at 0.3C to measure the initial capacity and are shown in Table 1 below.

<Experiment 2> - Resistance measurement

After performing one cycle of charging and discharging the unit cells according to the above examples and comparative examples at 0.3C, charging at 0.3C and charging to 4.2V (SOC 100), only 50% of the discharge capacity of the first cycle was 0.3C. DOD50 (= SOC 50) was maintained by discharging at C. The resistance of the unit cell was measured by discharging at 3C for 10 seconds at DOD 50 (= SOC 50%). Table 1 below shows resistance at DOD50 (=SOC 50).

<Experiment 3> - Capacity maintenance rate experiment

The unit cells according to the above examples and comparative examples were charged and discharged for 50 cycles at 45°C, and the discharge capacity after 50 cycles was calculated compared to the first discharge capacity. At this time, charging was done at 0.3C until it reached 4.2V, and discharging was done at a constant current of 1C until it reached 2.5V. This is shown in Table 1 and Figure 7 below. In Figure 7, the graphs from top to bottom are Example 1-1, Example 1-2, Comparative Example 1, and Comparative Example 2, respectively.

Example 1-1 Example 1-2 Comparative Example 1 Comparative Example 2 Cell capacity (mAh) 69.1 67.0 65.5 66.1 Resistance (Ω) 2.07 2.18 2.51 2.46 Capacity maintenance rate (%) 94.6 92.1 82.3 84.7

As can be seen in Table 1 and Figure 7, the cell capacity of Example 1-1 (Ex.1) and Example 1-2 (Ex.2) according to the present invention is that of Comparative Example 1 (Comp. Ex.1). and Comp. Ex.2, and the resistance is also low. As described above, because the cell capacity is large and the resistance is low, Examples 1-1 and 1-2 have a higher capacity retention rate after 50 cycles when compared to Comparative Examples 1 and 2. It can be seen that it is higher. Through the above experimental results, when two or more inorganic layers with different diameters of inorganic particles are formed as in the present invention, and the viscosity of the slurry forming the lowest layer is high, the second inorganic particles It can be seen that penetration of the binder into the electrode layer is suppressed, and the initial cell capacity, resistance, and capacity maintenance rate are improved.

Anyone skilled in the art to which the present invention pertains will be able to perform various applications and modifications within the scope of the present invention based on the above contents.

10, 100: Electrode current collector
110: negative electrode current collector
120: positive electrode current collector
20, 200: Electrode active material layer
210: Negative active material layer
220: positive electrode active material layer
250: unit electrode
30: inorganic layer
300: first inorganic layer
310: first inorganic particle
400: Second inorganic layer
410: secondary inorganic particle

Claims (19)

S1) preparing a first inorganic layer slurry containing first inorganic particles and a first binder and having a viscosity of 5000 cP to 20000 cP;
S2) preparing a second inorganic layer slurry containing second inorganic particles and a second binder;
S3) preparing a unit electrode having an electrode active material layer formed on at least one side of the electrode current collector; and
S4) Forming a first inorganic layer composed of the first inorganic slurry on at least one surface of the unit electrode electrode active material layer in step S3), and a second inorganic layer composed of the second inorganic slurry on the first inorganic layer. step;
Includes,
The D50 diameter of the first inorganic particle is larger than the pore size of the unit electrode electrode active material layer, and the diameter of the second inorganic particle is smaller than the D50 diameter of the first inorganic particle,
In the separator composite electrode manufacturing method, steps S1) to S3) may be performed in any order, or two or more steps may be performed simultaneously,
In step S1),
Preparing a first inorganic solution by mixing the first inorganic particles and a first solvent;
Preparing a first binder solution by mixing the first binder polymer and the first solvent; and
mixing the first inorganic solution and the first binder solution to prepare a first inorganic layer slurry;
Including,
In step S2),
Preparing a second inorganic solution by mixing the second inorganic particles and a second solvent;
Preparing a second binder solution by mixing the second binder polymer and the second solvent; and
mixing the second inorganic solution and the second binder solution to prepare a second inorganic layer slurry;
Includes,
A method of manufacturing a separator composite electrode wherein the first inorganic layer slurry has a higher viscosity than the second inorganic layer slurry. delete delete According to paragraph 1,
The diameter of the first inorganic particle is 500 nm to 3 μm,
A method of manufacturing a separator composite electrode wherein the second inorganic particle has a diameter of 20 nm to 300 nm. According to paragraph 1,
A separator composite electrode manufacturing method further comprising a dispersant in the first inorganic layer slurry of step S1) and/or the second inorganic layer slurry of step S2). According to paragraph 1,
The second inorganic particle is a separator composite electrode manufacturing method in which particles of different diameters are mixed. According to clause 6,
The method of manufacturing a separator composite electrode in which the second inorganic particles are manufactured by sequentially mixing the particles in the order of decreasing diameter in step S2). In clause 7,
When mixing the second inorganic particles, the method of manufacturing a separator composite electrode further includes mixing a dispersant between the step of mixing particles with small particle diameters and the step of mixing particles with large particle diameters. delete According to paragraph 1,
A method of manufacturing a separator composite electrode wherein the second inorganic layer slurry has a viscosity of 300 cP to 3000 cP. According to paragraph 1,
In step S4), the first inorganic layer slurry and the second inorganic layer slurry are simultaneously coated on at least one surface of the unit electrode electrode active material layer. According to paragraph 1,
In step S4), the first inorganic layer slurry is applied to at least one surface of the unit electrode electrode active material layer and dried to form the first inorganic layer, and the second inorganic layer slurry is applied on the first inorganic layer. A method of manufacturing a separator composite electrode that is applied and then dried to form a second inorganic layer. According to clause 12,
A separator composite electrode manufacturing method further comprising laminating each of the first inorganic layer and/or the second inorganic layer after formation. According to clause 13,
The method of manufacturing a separator composite electrode comprising performing the lamination at 20°C to 200°C. According to paragraph 1,
The first inorganic particle and/or the second inorganic particle includes at least one of AlOOH, Al(OH) ₃ , and Al ₂ O ₃ . According to paragraph 1,
A method of manufacturing a separator composite electrode, wherein the second inorganic particle includes surface modification. A separator composite electrode manufactured according to the method for manufacturing a separator composite electrode according to any one of claims 1, 4 to 8, and 10 to 16. A method of manufacturing an electrode assembly comprising the step of stacking at least one layer of the separator composite electrode according to claim 17 and laminating them to manufacture a unit cell. An electrode assembly including the separator composite electrode according to claim 17.