KR20240097491A - Method for manufacturing electrode for all solid battery - Google Patents

Abstract

The present invention relates to a method of manufacturing an electrode for an all-solid-state battery. Specifically, the present invention relates to a method of manufacturing an electrode for an all-solid-state battery, which includes forming an electrode in the form of a sheet, then folding the sheet to form a double layer, and performing a plurality of rolling processes. It is about manufacturing method.

Description

Method for manufacturing electrodes for all-solid-state batteries {METHOD FOR MANUFACTURING ELECTRODE FOR ALL SOLID BATTERY}

The present invention relates to a method of manufacturing an electrode for an all-solid-state battery. Specifically, it relates to a method of manufacturing an electrode for an all-solid-state battery, which includes forming a sheet-shaped electrode, folding the sheet to form a double layer, and performing a plurality of rolling processes.

As technology development and demand for mobile devices increase, the demand for secondary batteries as an energy source is rapidly increasing. Among these secondary batteries, lithium secondary batteries, which have high energy density and voltage, long cycle life, and low self-discharge rate, have been commercialized and are widely used. In addition, various batteries that can overcome the limitations of current lithium secondary batteries are being studied in terms of battery capacity, safety, output, large size, and ultra-miniaturization.

Representative examples include a metal-air battery with a very large theoretical capacity compared to lithium secondary batteries, an all-solid-state battery with no risk of explosion in terms of safety, and a super capacitor in terms of output. Continuous research is being conducted in academia and industry on supercapacitors, NaS batteries or RFBs (redox flow batteries) in terms of large size, and thin film batteries in terms of miniaturization.

Among these, an all-solid-state battery refers to a battery in which the liquid electrolyte used in existing lithium secondary batteries has been replaced with a solid one. Since flammable solvents are not used in the battery, ignition or explosion due to the decomposition reaction of the conventional electrolyte solution does not occur at all. Safety can be significantly improved.

Generally, an all-solid-state battery consists of an anode, a cathode, and a solid electrolyte. Among these, the electrode may include an electrode active material, a solid electrolyte, a conductive material, and a binder.

The electrode manufacturing method currently used is a wet method using a solvent. Specifically, an electrode active material, electrolyte, conductive material, and binder are added to a solvent and mixed to prepare an electrode slurry, and the slurry is applied on a current collector and dried to produce an electrode, which corresponds to a general wet method. However, when manufacturing an electrode using an electrode slurry using a solvent, a process of drying the electrode slurry applied on the current collector is required to remove the solvent. In this process, the thickness of the electrode active material layer decreases and a uniform thickness is maintained. There is a problem that it is difficult to manufacture the electrode active material layer.

To solve these problems, a method of manufacturing an electrode active material layer by mixing an electrode active material, a conductive material, and a binder in a dry state without using the solvent is being considered.

When manufacturing an electrode for an all-solid-state battery, an electrode active material, a solid electrolyte, a conductive material, and a binder are mixed to prepare a mixture containing the electrode active material. The mixture prepared in this way is applied on an electrode current collector and then pressed through equipment such as a roll to manufacture an electrode. A binder such as polytetrafluoroethylene (PTFE) undergoes fiberization centered on the surface in contact with the roll when the roll is pressed. However, even if the binder is fiberized, the electrode active material, conductive material, and binder located inside the electrode are still dispersed in the form of small particles, so the durability of the electrode may be insufficient. The durability of the electrode is a factor that can be related to the lifespan of the electrode and can directly affect the performance of the battery. In particular, when the electrode is manufactured in a dry manner, the cohesion between the particles of the electrode active material, solid electrolyte, conductive material, and binder may be relatively reduced. Therefore, in order to improve the durability of the electrode, the dispersion of the particles of the mixture of electrolyte and active material, etc. may play an even more important role.

Accordingly, the present inventor completed the present invention after researching a method for solving the problem of dispersion of mixture particles such as solid electrolyte and active material in the production of electrodes for all-solid-state batteries.

Republic of Korea Patent Publication No. 10-2014-0136952

The present invention seeks to provide a method for manufacturing an electrode for an all-solid-state battery that can improve the durability of the electrode by improving the dispersion of mixture particles containing an electrode active material, a solid electrolyte, a binder, and a conductive material.

According to the first aspect of the present invention,

(S1) mixing electrode active material, solid electrolyte, binder, and conductive material; (S2) converting the mixed materials into fibers at room temperature; (S3) pulverizing the fibrous material at room temperature; (S4) manufacturing a first sheet using pulverized material; And (S5) manufacturing a second sheet using the first sheet, wherein the second sheet includes folding the first sheet to form a double layer and then rolling a plurality of times. A method for manufacturing electrodes for all-solid-state batteries is provided.

In one embodiment of the present invention, the rolling step uses a first roll and a second roll, and the distance between the first roll and the second roll is 80 ㎛ to 150 ㎛.

In one embodiment of the present invention, the gear ratio between the first roll and the second roll is 1:1 to 1:1.5.

In one embodiment of the present invention, the rolling step further includes a third roll, and the third roll is arranged in a straight line with the first roll and the second roll.

In one embodiment of the present invention, the gap between the second roll and the third roll is 80 ㎛ to 150 ㎛.

In one embodiment of the present invention, the gear ratio between the second roll and the third roll is the same as the gear ratio between the first roll and the second roll.

In one embodiment of the present invention, the plurality of rolling steps includes gradually narrowing the gap between roll mills.

In one embodiment of the present invention, the rolling step uses a roll mill rotating at 10 RPM to 20 RPM at 20°C to 40°C.

In one embodiment of the present invention, in step (S1), the electrode active material, solid electrolyte, binder, and conductive material are mixed at 1 ℃ to 20 ℃ with a mixer including a mixing vessel rotating at 1 RPM to 30 RPM. .

In one embodiment of the present invention, in step (S2), a kneader that applies a shear force of 20 N·m to 200 N·m to the mixed material is used.

In one embodiment of the present invention, in step (S2), the mixed material is fiberized with a twin screw kneader rotating at 10 RPM to 50 RPM at 20 ° C. to 60 ° C.

In one embodiment of the present invention, in step (S3), the fiberized material is pulverized with a lab mill rotating at 10,000 RPM to 30,000 RPM at room temperature.

In one embodiment of the present invention, the particles pulverized in step (S3) are selected so that only particles with a particle size of 1 mm or less are included before being manufactured into the first sheet in step (S4).

In one embodiment of the present invention, the electrode active material is a lithium transition metal oxide having an average particle diameter (D50) of 7 ㎛ to 30 ㎛.

In one embodiment of the present invention, the conductive material is a carbon-based material or a metal material.

In one embodiment of the present invention, the binder includes polytetrafluoroethylene.

The electrode for an all-solid-state battery according to the present invention has improved dispersion of particles of a mixture of electrode active material, solid electrolyte, binder, and conductive material, and improved durability of the electrode.

The method for manufacturing an electrode for an all-solid-state battery according to the present invention manufactures an electrode through a dry method without using a solvent, so the electrode slurry preparation step is unnecessary, simplifying the process, and enabling a continuous process, making it economical.

1 is a scanning electron microscope (SEM) image of the surface of an electrode prepared according to Example 1.
Figure 2 is a scanning electron microscope (SEM) image of the surface of an electrode prepared according to Example 2.
Figure 3 is a diagram showing the results of measuring the tensile strength of electrodes manufactured according to Examples 1 and 2.

The embodiments provided according to the present invention can all be achieved by the following description. It should be understood that the following description describes preferred embodiments of the present invention, and that the present invention is not necessarily limited thereto.

For the physical properties described in this specification, if the measurement conditions and methods are not specifically described, the physical properties are measured according to the measurement conditions and methods generally used by those skilled in the art.

Generally, when manufacturing electrodes for an all-solid-state battery, an electrode active material, a solid electrolyte, a conductive material, and a binder are mixed to prepare a mixture containing the electrode active material. Considering the processability of the mixture, the mixture may be used in the form of a slurry by adding it to a solvent such as water or an organic solvent. The mixture is applied on an electrode current collector and then pressed through equipment such as a roll to manufacture an electrode. When preparing the mixture in a dry manner without a solvent, the functionality of the binder may be reduced and the bonding strength of the electrode active material, conductive material, and binder may be reduced. This problem can be solved by fiberizing the binder through pressurization.

However, even though the binder is fiberized, the electrode active material, conductive material, and binder located inside the electrode are still dispersed in the form of small particles, so there is a shortcoming in securing the durability of the electrode. Accordingly, the present invention provides a method of manufacturing an electrode for an all-solid-state battery with improved dispersion of mixture particles such as a solid electrolyte and an active material within the electrode, and a battery accordingly.

According to one embodiment of the present invention, a method for manufacturing an electrode for an all-solid-state battery is provided including the following steps:

(S1) mixing electrode active material, solid electrolyte, binder, and conductive material;

(S2) fiberizing the mixed material;

(S3) pulverizing the fibrous material;

(S4) manufacturing a first sheet using pulverized material; and

(S5) manufacturing a second sheet using the first sheet,

The second sheet may include a plurality of rolling steps after folding the first sheet to form a double layer.

The step (S1) is a step of uniformly mixing the electrode active material, solid electrolyte, binder, and conductive material, and a mixture in the form of particles can be prepared from their mixture.

In one embodiment of the present invention, the step (S1) may be performed by mixing the electrode active material, solid electrolyte, binder, and conductive material at 1°C to 20°C. Specifically, the manufacturing temperature of the mixture is 1 ℃ or higher, 2 ℃ or higher, 3 ℃ or higher, 4 ℃ or higher, 5 ℃ or lower, or 20 ℃ or lower, 19 ℃ or lower, 18 ℃ or lower, 17 ℃ or lower, 16 ℃ or lower, It may be 15 ℃ or lower, 14 ℃ or lower, 13 ℃ or lower, 12 ℃ or lower, 11 ℃ or lower, and 10 ℃ or lower. This manufacturing temperature can prevent the solid electrolyte from clumping and coagulating.

The electrode active material, solid electrolyte, binder, and conductive material may each be sequentially mixed. For example, after mixing an electrode active material and a solid electrolyte, a binder may be added and mixed to the mixture of the electrode active material and the solid electrolyte. Thereafter, a conductive material may be added and mixed to the mixture of the electrode active material, solid electrolyte, and binder. The mixture may be mixed sequentially, but their mixing order is not limited to that described above.

The reason why the electrode active material, solid electrolyte, binder, and conductive material are sequentially mixed in this way is to prevent phase separation during the mixing process due to the difference in specific gravity between each material.

In one embodiment of the present invention, in step (S1), the electrode active material, solid electrolyte, binder, and conductive material are mixed with a mixer in which the blade in the mixing container rotates at a speed of 3,000 RPM to 15,000 RPM. . Specifically, the rotation speed of the blade in the mixing vessel is 3,000 RPM or more, 3,500 RPM or more, 4,000 RPM or more, 4,500 RPM or more, 5,000 RPM or more, 5,500 RPM or more, 6,000 RPM or more, or 15,000 RPM or less, 14,500 RPM or less, or 14,000 RPM or more. It may be below RPM, below 13,500 RPM, below 13,000 RPM, below 12,500 RPM, below 12,000 RPM. The rotation speed of these blades can effectively and uniformly mix the mixture in a short period of time.

Additionally, in step (S1), the electrode active material, solid electrolyte, binder, and conductive material may be placed in a mixing vessel and mixed using a mixer whose rotation speed is 1 RPM to 30 RPM. Specifically, the rotation speed of the mixing vessel is 1 RPM or more, 2 RPM or more, 3 RPM or more, 4 RPM or more, 5 RPM or more, 6 RPM or more, 7 RPM or more, 8 RPM or more, 9 RPM or more, or 10 RPM or more. , 30 RPM or less, 29 RPM or less, 28 RPM or less, 27 RPM or less, 26 RPM or less, 25 RPM or less, 24 RPM or less, 23 RPM or less, 22 RPM or less, 21 RPM or less, or 20 RPM or less. The rotation speed of this mixing vessel is to ensure sufficient time for uniform mixing when preparing the mixture.

The step (S2) is a step of fiberizing the mixed material, and the binder included in the mixed material is fiberized and bound to the electrode active material, solid electrolyte, and conductive material. In the fiberization step, a kneader capable of imparting a certain level of shear force to the mixture may be used. The term “kneader” used in this specification refers to a device capable of imparting a shear force of, for example, 20 N·m to 200 N·m to the mixture. If the above-described shear force can be applied, “ A device named “Mixer” may also be included in “Kneader” in this specification. The shear force refers to the maximum shear force that the device adds to the mixture, and its value is measured using a torque rheometer. Specifically, the shear force is 20 N·m or more, 25 N·m or more, 30 N·m or more, 35 N·m or more, 40 N·m or more, 45 N·m or more, 50 N·m or more, and 200 N·m or more. N·m or less, 190 N·m or less, 180 N·m or less, 170 N·m or less, 160 N·m or less, 150 N·m or less, 20 N·m to 200 N·m, 35 N·m It may be from 170 N·m to 50 N·m to 150 N·m. The shear force produced by these devices may be suitable for fiberizing the binder.

According to one embodiment of the present invention, the kneader may be a twin screw kneader or a paradoxical mixer, and specifically, it may be a twin screw kneader.

According to one embodiment of the present invention, the mixed material is fiberized with a twin screw kneader rotating at 10 RPM to 50 RPM. Specifically, the rotation speed may be 10 RPM or more, 15 RPM or more, 20 RPM or more, 25 RPM or more, 30 RPM or more, 50 RPM or less, 45 RPM or less, 40 RPM or less, 35 RPM or less, and 10 RPM to 50 RPM. It may be RPM, 15 RPM to 45 RPM, or 20 RPM to 40 RPM. This rotation speed is intended to ensure sufficient time for fiberization to proceed when preparing the mixture. By using a twin screw kneader, sufficient pressure is transmitted to the inside of the mixed material to enable overall fiberization. A sufficient effect can be obtained by performing the fiberization for about 5 to 10 minutes.

According to one embodiment of the present invention, the fiberizing step is performed at 20°C to 60°C. Specifically, the temperature of the fiberization step may be 20 ℃ or higher, 25 ℃ or higher, 30 ℃ or higher, 35 ℃ or higher, 40 ℃ or lower, or 60 ℃ or lower, 55 ℃ or lower, 50 ℃ or lower, or 45 ℃ or lower. The temperature may be suitable for fiberization of the binder.

The step (S3) is a step of pulverizing the fibrous material, and through the pulverization, the particles of the mixture in the electrode can be evenly distributed.

According to one embodiment of the present invention, the fiberized material can be pulverized with a lab mill rotating at 10,000 RPM to 30,000 RPM. Specifically, the rotation speed of the lap mill is 10,000 RPM or more, 12,000 RPM or more, 14,000 RPM or more, 16,000 RPM or more, 18,000 RPM or more, 20,000 RPM or more, 30,000 RPM or less, 28,000 RPM or less, 26,000 RPM or less, 24,000 RPM or less, It may be below 22,000 RPM or below 20,000 RPM. This rotation speed is significantly faster than during mixing and grinding, and enables grinding to an appropriate size effectively within a short period of time. Performing the grinding for a short period of time, less than 1 minute, can prevent excessive grinding of the fiberized particles.

The particles pulverized in step (S3) may be selected from the pulverized material before being manufactured into the first sheet in step (S4). When manufacturing a sheet-shaped electrode through the step of selecting materials that can be evenly dispersed among the pulverized materials and then manufacturing the first sheet, it is possible to manufacture a uniform sheet shape without agglomeration of particles on the electrode surface. Let it be done. Ground material can be sorted based on particle size. When selecting based on particle size, a sieve can be used.

In one embodiment of the present invention, particles with a particle size of 1 mm or less are selected from the pulverized material in step (S3). If the particle size is 1 mm or less, the degree of fluidity is above normal, so there may be no problem in forming a uniform sheet, but if the particle size is more than 1 mm, the degree of fluidity is very poor. , defects such as pores may occur in the manufactured sheet. Basically, the particle size distribution determined through grinding increases the number of particles centered on the average diameter of the particles, so small particles not only have a small number but also occupy a small volume, so they do not have a significant adverse effect on the formation of the sheet. .

The step (S4) is a step of manufacturing a first sheet using pulverized material. The pulverized material can be placed on a current collector and then rolled through a roll to form a sheet.

The step of disposing the pulverized material on the current collector may include disposing the pulverized material on the current collector in the following manner. Specifically, the pulverized material may be disposed with a uniform thickness on the current collector using a scattering method. More specifically, when using the scattering method, the pulverized material is moved through a feeding roller, and when the pulverized material is applied to the current collector, a brush is used to apply the pulverized material to the current collector. Can be applied in a fixed amount.

The step of rolling the current collector on which the pulverized material is disposed may include applying pressure to the current collector, and in this case, the pressure may include compressive force. The pressure may be applied through a roll press method. A device for a roll press may include a roll that applies pressure to the pulverized material and a current collector and a belt that moves the current collector. The current collector is moved by the vent, and at the same time, the mixture and the current collector receive pressure from the roll. At this time, pressure includes compression force. Before applying the pressure, the belt is preheated to 50° C. to 100° C. so that heat can be transferred to the current collector on which the pulverized material is disposed. Additionally, when applying the pressure, the temperature of the roll may be 50°C to 150°C.

The step (S5) is a step of manufacturing a second sheet using the first sheet. The second sheet is formed by folding the first sheet to form a double layer, and then going through a plurality of rolling steps to finally form a sheet. Electrodes of this type can be manufactured.

In one embodiment of the present invention, in step (S5), a first roll and a second roll are used in the rolling step, and the gap between the first roll and the second roll may be 80 ㎛ to 150 ㎛. Specifically, the spacing between the first roll and the second roll may be 80 ㎛, 90 ㎛, 100 ㎛, 110 ㎛, 120 ㎛, 130 ㎛, 140 ㎛, and 150 ㎛.

In one embodiment of the present invention, in step (S5), a plurality of rolls may be used in the rolling step. For example, a first roll and a second roll may be used as the roll. Additionally, a third roll may be further included in the first roll and the second roll. The first roll and the second roll may be arranged horizontally or vertically side by side. Additionally, the third roll may be connected to the first roll and the second roll and arranged in a straight line.

The gear ratio between the first roll and the second roll may be 1:1 to 1:1.5. Specifically, the gear ratio between the first roll and the second roll may be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5, but is not limited to these examples.

The gear ratio between the second roll and the third roll may be the same as the gear ratio between the first roll and the second roll. That is, the gear ratio between the second roll and the third roll may be 1:1 to 1:1.5. Specifically, the gear ratio between the second roll and the third roll may be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5, but is not limited to these examples.

Therefore, if three rolls are used, the gear ratios between the first roll, second roll and third roll are 1:1:1, 1:1.1:1.21, 1:1.2:1.44, 1:1.3:1.69, 1: It may be 1.4:1.96 or 1:1.5:2.25, but is not limited to these examples.

If the gear ratio between the rolls is outside the above range, there is a problem that the sheet-shaped electrode is torn.

The rolling step in step (S5) can be performed by gradually narrowing the gap between roll mills. For example, after folding the first sheet to form a double layer, one rolling step is performed on a roll mill with a gap of 150 μm, and then two rolling steps are performed on a roll mill with a gap of 140 μm, , then 3 rolling steps are performed on a roll mill with a spacing of 130 ㎛, then 4 rolling steps are performed on a roll mill with a spacing of 120 ㎛, and then 5 rolling steps are performed on a roll mill with a spacing of 110 ㎛. ㎛, then 6 rolling steps are carried out on a roll mill with a gap of 100 ㎛, then 7 rolling steps are carried out on a roll mill with a gap of 90 ㎛, then 8 Each rolling step can be performed in a roll mill with a spacing of 80 μm, but the spacing between the rolling number and the roll mill is not limited to this. In this way, by performing a plurality of rolling steps while gradually narrowing the interval between roll mills, the particles of the mixture on the surface of the electrode can be manufactured so that they are evenly dispersed. On the other hand, when the target thickness of the electrode is manufactured through one rolling step instead of multiple rolling steps, there is a problem that the particles of the mixture on the electrode surface are not dispersed.

In one embodiment of the present invention, in step (S5), rolling may be performed at 20°C to 40°C. Specifically, in step (S5), the rolling temperature is 20 ℃ or higher, 21 ℃ or higher, 22 ℃ or higher, 23 ℃ or higher, 24 ℃ or higher, 25 ℃ or higher, 26 ℃ or higher, 27 ℃ or higher, 28 ℃ or higher, 29 ℃ or higher. or more than 30 ℃, or below 40 ℃, below 39 ℃, below 38 ℃, below 37 ℃, below 36 ℃, below 35 ℃, below 34 ℃, below 33 ℃, below 32 ℃, below 31 ℃, below 30 ℃ You can. The temperature may be suitable for rolling without deformation of the mixture in the sheet.

In one embodiment of the present invention, in step (S5), rolling may be performed using a roll mill rotating at a speed of 1 RPM to 20 RPM. Specifically, the roll mill rotation speed of the rolling is 1 RPM or more, 2 RPM or more, 3 RPM or more, 4 RPM or more, 5 RPM or more, 6 RPM or more, 7 RPM or more, 8 RPM or more, 9 RPM or more, or 10 RPM or more. , 20 RPM or less, 19 RPM or less, 18 RPM or less, 17 RPM or less, 16 RPM or less, 15 RPM or less, 14 RPM or less, 13 RPM or less, 12 RPM or less, 11 RPM or less. This rotation speed may be suitable for rolling the sheet shape without distortion.

According to one embodiment of the present invention, the positive electrode active material is lithium transition metal oxide. In the lithium transition metal oxide, the transition metal has the form Li _1+x M _y O _2+Z (0≤x≤5, 0<y≤2, 0≤z≤2), where M is Ni, Co , Mn, Fe, P, Al, Mg, Ca, Zr, Zn, Ti, Ru, Nb, W, B, Si, Na, K, Mo, V and combinations thereof, within the above range. There are no particular restrictions. More specifically, lithium transition metal oxides are LiCoO ₂ , LiNiO ₂ , LiMnO ₂ , Li ₂ MnO ₃ , LiMn ₂ O ₄ , Li(Ni _a Co _b Mn _c )O ₂ (0<a<1, 0<b<1 , 0<c<1, a+b+c=1), LiNi _1-y Co _y O ₂ (O<y<1), LiCo _1-y Mn _y O ₂ , LiNi _1-y Mn _y O ₂ ( O<y<1), Li(Ni _a Co _b Mn _c )O ₄ (0<a<2, 0<b<2, 0<c<2, a+b+c=2), LiMn _2-z It is selected from Ni _z O ₄ (0<z<2), LiMn _2-z Co _z O ₄ (0<z<2), and combinations thereof.

According to one embodiment of the present invention, the negative electrode active material is a compound capable of reversible intercalation and deintercalation of lithium. Specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; Metallic compounds that can be alloyed with lithium, such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloy, Sn alloy, or Al alloy; Metal oxides that can dope and undope lithium, such as SiO _β (0<β<2), SnO ₂ , vanadium oxide, and lithium vanadium oxide; Alternatively, a composite containing the above-described metallic compound and a carbonaceous material, such as a Si-C composite or Sn-C composite, may be used, and any one or a mixture of two or more of these may be used. Additionally, a metallic lithium thin film may be used as the negative electrode active material. Additionally, both low-crystalline carbon and high-crystalline carbon can be used as the carbon material. Representative examples of low-crystalline carbon include soft carbon and hard carbon, and high-crystalline carbon includes amorphous, plate-shaped, flaky, spherical, or fibrous natural graphite, artificial graphite, and Kish graphite. graphite, pyrolytic carbon, mesophase pitch based carbon fiber, meso-carbon microbeads, mesophase pitches, and petroleum or coal tar pitch. High-temperature calcined carbon such as derived cokes is a representative example.

According to one embodiment of the present invention, the electrode active material is a lithium transition metal oxide having an average particle diameter (D ₅₀ ) of 7 ㎛ to 30 ㎛. Specifically, the average diameter (D ₅₀ ) of the particles is 7 ㎛ or more, 7.5 ㎛ or more, 8 ㎛ or more, 8.5 ㎛ or more, 9 ㎛ or more, 9.5 ㎛ or more, 10 ㎛ or more, 30 ㎛ or less, 28 ㎛ or less, It may be 26 ㎛ or less, 24 ㎛ or less, 22 ㎛ or less, 20 ㎛ or less, 7 ㎛ to 30 ㎛, 8.5 ㎛ to 24 ㎛, and 10 ㎛ to 20 ㎛.

The conductive material is used to provide conductivity to the electrode, and can be used without particular limitation as long as it does not cause chemical change and has electronic conductivity in the battery being constructed. Specific examples include graphite such as natural graphite and artificial graphite; Carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, summer black, single-walled or multi-walled carbon nanotubes, carbon fiber, graphene, activated carbon, and activated carbon fiber; Metal powders or metal fibers such as copper, nickel, aluminum, and silver; Conductive whiskers such as zinc oxide and potassium titanate; Conductive metal oxides such as titanium oxide; Or conductive polymers such as polyphenylene derivatives, etc., of which one type alone or a mixture of two or more types may be used.

The conductive material may be a carbon-based material or a metal material, and the metal material may include the above-described metal powder, metal fiber, or conductive metal oxide. The conductive material may be spherical or linear particles. When the conductive material is a spherical particle, the average diameter (D ₅₀ ) of the particles may be 1 nm to 100 nm, specifically 5 nm to 70 nm, and more specifically 10 nm to 40 nm. When the conductive material is a linear particle, the length of the linear particle may be 1 ㎛ to 10 ㎛, specifically 2 ㎛ to 9 ㎛, more specifically 3 ㎛ to 8 ㎛, the diameter of the vertical cross section is 10 nm to 500 nm, Specifically, it may be 50 nm to 350 nm, and more specifically, 100 nm to 200 nm.

The binder serves to improve adhesion between electrode active material particles and adhesion between the electrode active material and the electrode current collector. In order to achieve the purpose of the present invention, the binder is a material that can be fiberized by pressure, etc., and is not particularly limited as long as it is a material that can be fiberized and is generally used as a binder in the relevant technical field. According to one embodiment of the present invention, the binder includes polytetrafluoroethylene. In the case of the binder, since it exists in a fibrous state in the active layer, its particle size is less important than other components.

If the binder basically includes a fibrous binder such as polytetrafluoroethylene, it can be used by modifying the fibrous binder or mixing an additional binder. The additional binder may be a binder commonly used in the relevant technical field, as long as it has the functionality of improving adhesion between electrode active material particles and adhesion between the electrode active material and the electrode current collector. According to one embodiment of the present invention, the additional binder is polyvinylidene fluoride (PVDF), vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinyl alcohol, starch, hydroxypropyl Cellulose, regenerated cellulose, polyvinylpyrrolidone, polyimide, polyamidoimide, polyethylene, polypropylene, ethylene-propylene-diene monomer (EPDM), sulfonated EPDM, styrene butyrene rubber, fluorine rubber and the like. It may be selected from a combination, but is not limited thereto.

A mixture containing the electrode active material, solid electrolyte, conductive material, and binder may be applied on an electrode current collector and included in the electrode. The electrode current collector is not particularly limited as long as it is conductive without causing chemical changes in the battery, for example, stainless steel, aluminum, nickel, titanium, calcined carbon, or carbon, nickel, titanium on the surface of aluminum or stainless steel. , surface treated with silver, etc. may be used. Additionally, the electrode current collector may typically have a thickness of 3 to 500 ㎛, and fine irregularities may be formed on the surface of the electrode current collector to increase the adhesion of the electrode active material. For example, it can be used in various forms such as films, sheets, foils, nets, porous materials, foams, and non-woven materials.

In one aspect of the present invention, an all-solid-state battery is provided including the above-described all-solid-state battery electrode as an anode and/or a cathode. In constructing the all-solid-state battery, in addition to the solid electrolyte contained in the electrode, a separate solid electrolyte layer may be introduced between the anode and the cathode, and this solid electrolyte layer plays the same role as a separator in a general lithium secondary battery. can do. In some cases, the above-mentioned electrodes can be used together with a liquid electrolyte to be used as a semi-solid battery. In this case, a separate polymer separator may be needed.

The solid electrolyte is a polymer-based solid electrolyte, which is formed by adding a polymer resin to a solvated lithium salt, or an organic electrolyte containing an organic solvent and a lithium salt, an ionic liquid, a monomer or an oligomer, etc., is added to the polymer resin. It may be a polymer gel electrolyte contained therein. The solid electrolyte may be one or more selected from the group consisting of a polymer-based solid electrolyte, a sulfide-based solid electrolyte, and an oxide-based solid electrolyte. According to one embodiment of the present invention, a sulfide-based solid electrolyte is used as the solid electrolyte.

In one embodiment of the present invention, the sulfide-based solid electrolyte contains sulfur (S) and has ionic conductivity of a metal belonging to Group 1 or 2 of the periodic table, and is Li-PS-based glass or Li-PS-based glass. May include ceramics. Non-limiting examples of such sulfide-based solid electrolytes include Li ₂ SP ₂ S ₅ , Li ₂ S-LiI-P ₂ S ₅ , Li ₂ S-LiI-Li ₂ OP ₂ S ₅ , Li ₂ S-LiBr-P ₂ S ₅ , Li ₂ S-LiCl-P ₂ S ₅ , Li ₂ S-Li ₂ OP ₂ S ₅ , Li ₂ S-Li ₃ PO ₄ -P ₂ S ₅ , Li ₂ SP ₂ S ₅ -P ₂ O ₅ , Li ₂ SP ₂ S ₅ -SiS ₂ , Li ₂ SP ₂ S ₅ -SnS, Li ₂ SP ₂ S ₅ -Al ₂ S ₃ , Li ₂ S-GeS ₂ , Li ₂ S-GeS ₂ -ZnS, etc. and may include one or more of these.

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 includes ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; Ether-based solvents such as dibutyl ether or tetrahydrofuran; Ketone-based solvents such as cyclohexanone; Aromatic hydrocarbon solvents such as benzene and fluorobenzene; Dimethylcarbonate (DMC), diethylcarbonate (DEC), methylethylcarbonate (MEC), ethylmethylcarbonate (EMC), ethylene carbonate (EC), propylene carbonate carbonate-based solvents such as PC); Alcohol-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2 to C20 straight-chain, branched or ring-structured hydrocarbon group and may include a double bond aromatic ring or ether bond); Amides such as dimethylformamide; Dioxolanes such as 1,3-dioxolane; Alternatively, sulfolane, etc. may be used. Among these, carbonate-based solvents are preferable, and cyclic carbonates (e.g., ethylene carbonate or propylene carbonate, etc.) with high ionic conductivity and high dielectric constant that can improve the charging and discharging performance of the battery, and low-viscosity linear carbonate-based compounds ( For example, ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) are more preferred. In this case, excellent electrolyte performance can be obtained by mixing cyclic carbonate and chain carbonate in a volume ratio of about 1:1 to about 1:9.

The lithium salt can be used without particular restrictions as long as it is a compound that can provide lithium ions used in lithium secondary batteries. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAl0 ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ . LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of lithium salt is within the above range, the electrolyte has appropriate conductivity and viscosity, so excellent electrolyte performance can be achieved and lithium ions can move effectively.

As described above, the all-solid-state battery containing the electrode according to the present invention stably exhibits excellent discharge capacity, output characteristics, and capacity retention rate, and is therefore widely used in portable devices such as mobile phones, laptop computers, digital cameras, and hybrid electric vehicles (hybrid electric vehicles). It is useful in the field of electric vehicles such as electric vehicle (HEV).

Accordingly, according to another aspect of the present invention, a battery module including the all-solid-state battery as a unit cell and a battery pack including the same are provided.

The battery module or battery pack is a power tool; Electric vehicles, including electric vehicles (EV), hybrid electric vehicles, and plug-in hybrid electric vehicles (PHEV); Alternatively, it can be used as a power source for any one or more mid- to large-sized devices among power storage systems.

Hereinafter, preferred examples are presented to aid understanding of the present invention. However, the following examples are provided to facilitate understanding of the present invention and do not limit the present invention thereto.

Example

Example 1

The electrode active material is 84.6% by weight of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ (average particle diameter (D ₅₀ ): 10㎛, manufacturer: LG Chem, product: HN803S), and the solid electrolyte is Li ₂ SP ₂ S ₅ (14% by weight). Weight %, 0.2 weight % of CNF (Carbon nano fiber, average diameter: 150 nm, average length: 6 ㎛, manufacturer: Teijin, product: Potencia) as a conductive material, and polytetrafluoroethylene (average particle diameter (particle diameter) as a binder. D ₅₀ ): 500 ㎛, manufacturer: Daikin, product: F106) 1.2% by weight was used.

The LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and Li ₂ SP ₂ S ₅ were mixed for 30 seconds at a rotation speed of 10 RPM at 5°C using a tumbling mixer (5000 rpm, manufacturer: KMtech), There was a rest period of 3 minutes (1 cycle). The above cycle was repeated a total of 8 times to perform 8 cycles.

Afterwards, CNF was added to the mixture of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ and Li ₂ SP ₂ S ₅ and rotated at 5° C. at 10 RPM using a tumbling mixer (5000 rpm, manufacturer: KMtech). Mixed at speed for 30 seconds, followed by a rest period of 3 minutes (1 cycle). The above cycle was repeated a total of 2 times to perform 2 cycles.

Afterwards, polytetrafluoroethylene was added to the mixture of LiNi _0.8 Co _0.1 Mn _0.1 O ₂ , Li ₂ SP ₂ S ₅ and CNF, and stirred at 5°C using a tumbling mixer (5000 rpm, manufacturer). After mixing for 30 seconds at a rotation speed of 10 RPM, there was a rest period of 3 minutes (1 cycle). The above cycle was repeated a total of 2 times to perform 2 cycles.

The mixed material was fiberized in a twin screw kneader (manufacturer: Brabender, product: Torque rheometer) at room temperature and a rotation speed of 30 RPM for 5 minutes.

The fibrous material was ground in a lab mill (manufacturer: OSAKA CHEMICAL, product: OML-1) for 30 seconds at room temperature and a rotation speed of 20,000 RPM.

After separately selecting only particles with a particle size of 1 mm or less among the pulverized particles, the selected particles are applied to the current collector and then rolled through a roll mill (roll spacing: 150㎛/150㎛, manufacturer: Kmtech, product: KRM-80B) The first sheet was manufactured by rolling at room temperature conditions and a rotation speed of 10 RPM.

After folding the first sheet once, rolling it in a mill with a roll spacing of 140㎛/140㎛, then folding it once again and rolling it in a mill with a roll spacing of 130㎛/130㎛ to form a second sheet. and finally produced a sheet-shaped electrode.

Example 2

After manufacturing the first sheet in the same manner as in Example 1, the first sheet was folded once, rolled in a mill with a roll spacing of 140㎛/140㎛, and then folded once again. , rolling on a mill with a roll spacing of 130㎛/130㎛, then folding once again, rolling on a mill with a roll spacing of 120㎛/120㎛, then folding once again, and then folding once again, with a roll spacing of Rolled on a mill with 110㎛/110㎛, then folded once again, rolled on a mill with a roll spacing of 100㎛/100㎛, then folded once again, and then rolled again with a roll spacing of 90㎛/90. A second sheet was manufactured by rolling in a ㎛ mill, and finally, a sheet-shaped electrode was manufactured.

Comparative Example 1

After manufacturing the first sheet, a sheet-shaped electrode was manufactured in the same manner as that manufactured in Example 1, except that the sheet was rolled multiple times.

Experiment example

Experimental Example 1

The structures of the surface and internal cross-section of each electrode manufactured according to Examples 1 and 2 were confirmed through a scanning electron microscope (SEM, magnification: ×3,000, manufacturer: JEOL, product: JSM-7200F), and are shown in Figures 1 and 2. shown in

1 is a scanning electron microscope (SEM) image of the surface of an electrode prepared according to Example 1. In FIG. 1, the surface is an image taken at a magnification of ×1,000, and the cross section is an image taken at a magnification of ×2,000.

Figure 2 is a scanning electron microscope (SEM) image of the surface of an electrode prepared according to Example 2. In FIG. 1, the surface is an image taken at a magnification of ×1,000, and the cross section is an image taken at a magnification of ×2,000.

Comparing Figures 1 and 2 for the surface of the electrode, particles of a mixture of electrolyte and active material were observed on the surface of the electrode manufactured according to Example 1, and it was confirmed that the degree of partial dispersion was insignificant. In addition, it was confirmed that the mixture of electrolyte and active material was evenly dispersed on the surface of the electrode manufactured according to Example 2.

In addition, the internal cross section of the electrode manufactured according to Example 1 confirmed that only compression occurred between particles of the mixture of electrolyte and active material and that polytetrafluoroethylene was partially fiberized between pores between particles. In addition, the internal cross section of the electrode manufactured according to Example 2 confirmed that polytetrafluoroethylene was fiberized in the pores between the particles, thereby reducing the volume of the pores.

Experimental Example 2

The tensile strength of each sheet-shaped electrode manufactured according to Examples 1 and 2 was analyzed using a tensile strength measuring device (manufacturer: LLOYD, product: LS1). The results are shown in Table 1 below.

tensile strength Example 1 Example 2 Comparative Example 1 MD direction (MPa) 0.4 0.8 0.1 or less

According to Table 1, both Examples 1 and 2 showed high tensile strength in the MD direction of 0.4 MPa or more, but in the case of Comparative Example 1, the tensile strength in the MD direction was 0.1 MPa or less, confirming that the tensile strength was low. there was.

Experimental Example 3

The all-solid-state battery manufactured using the electrode according to Examples 1 and 2 and Comparative Example 1 was fixed to a jig inside a chamber at 60 ° C. and initial charge and discharge were performed under conditions of 0.1 C, so that the initial charge capacity was 203. Discharge capacity was measured based on mAh/g. The measured discharge capacities are listed in Table 2 below.

Example 1 Example 2 Comparative Example 1 Discharge capacity (mAh/g) 161 182 149

As shown in Table 2, the discharge capacity of the all-solid-state battery containing the electrodes of Examples 1 and 2 manufactured through multiple rolling steps was higher than that of the all-solid-state battery containing the electrodes of Comparative Example 1 manufactured through simple rolling. I was able to confirm something big.

All simple modifications or changes of the present invention fall within the scope of the present invention, and the specific scope of protection of the present invention will be made clear by the appended claims.

Claims (16)

(S1) mixing electrode active material, solid electrolyte, binder, and conductive material;
(S2) converting the mixed materials into fibers at room temperature;
(S3) pulverizing the fibrous material at room temperature;
(S4) manufacturing a first sheet using pulverized material; and
(S5) manufacturing a second sheet using the first sheet,
The second sheet is a method of manufacturing an electrode for an all-solid-state battery, characterized in that it includes a plurality of rolling steps after folding the first sheet to form a double layer. According to paragraph 1,
The rolling step is a method of manufacturing an electrode for an all-solid-state battery, wherein a first roll and a second roll are used, and the gap between the first roll and the second roll is 80 ㎛ to 150 ㎛. According to paragraph 2,
A method of manufacturing an electrode for an all-solid-state battery, characterized in that the gear ratio between the first roll and the second roll is 1:1 to 1:1.5. According to paragraph 2,
The rolling step further includes a third roll, and the third roll is disposed in a straight line with the first roll and the second roll. According to clause 4,
A method of manufacturing an electrode for an all-solid-state battery, characterized in that the gap between the second roll and the third roll is 80 ㎛ to 150 ㎛. According to clause 4,
A method of manufacturing an electrode for an all-solid-state battery, characterized in that the gear ratio between the second roll and the third roll is the same as the gear ratio between the first roll and the second roll. According to paragraph 1,
A method of manufacturing an electrode for an all-solid-state battery, wherein the plurality of rolling steps includes gradually narrowing the gap between roll mills. According to paragraph 1,
The rolling step is a method of manufacturing an electrode for an all-solid-state battery, characterized in that a roll mill rotating at 1 RPM to 20 RPM is used at 20 ℃ to 40 ℃. According to paragraph 1,
The step (S1) is an electrode for an all-solid-state battery, characterized in that the electrode active material, solid electrolyte, binder, and conductive material are mixed with a mixer including a mixing vessel rotating at 1 ℃ to 20 ℃ and 1 RPM to 30 RPM. Manufacturing method. According to paragraph 1,
The (S2) step is a method of manufacturing an electrode for an all-solid-state battery, characterized in that a kneader is used to apply a shear force of 20 N·m to 200 N·m to the mixed material. According to paragraph 1,
In the step (S2), the mixed material is fiberized with a twin screw kneader rotating at 10 RPM to 50 RPM at 20 ℃ to 60 ℃. A method of manufacturing an electrode for an all-solid-state battery. According to paragraph 1,
In the step (S3), the fibrous material is pulverized with a lab mill rotating at 10,000 RPM to 30,000 RPM at room temperature. According to paragraph 1,
A method of manufacturing an electrode for an all-solid-state battery, characterized in that the particles pulverized in the step (S3) are selected to contain only particles with a particle size of 1 mm or less before being manufactured into the first sheet in the step (S4). According to paragraph 1,
A method of manufacturing an electrode for an all-solid-state battery, wherein the electrode active material is a lithium transition metal oxide having an average particle diameter (D ₅₀ ) of 7 ㎛ to 30 ㎛. According to paragraph 1,
A method of manufacturing an electrode for an all-solid-state battery, wherein the conductive material is a carbon-based material or a metal material. According to paragraph 1,
A method of manufacturing an electrode for an all-solid-state battery, characterized in that the binder contains polytetrafluoroethylene.