Cathode for all-solid-state battery and all-solid-state battery comprising same

Abstract

The present invention relates to a cathode for an all-solid-state battery, and an all-solid-state battery including same. More specifically, the cathode active material layer included in the cathode comprises a cathode active material, a sulfide-based solid electrolyte, and a conductive material, wherein the particle diameter of the conductive material is configured to lie between the particle diameter of the cathode active material and the particle diameter of the sulfide-based solid electrolyte, thereby increasing the interfacial area between the cathode active material and the sulfide-based solid electrolyte while reducing the overall porosity of the cathode. Consequently, the conductivity of the cathode is maintained, and the energy density of the cell is enhanced without compromising cell performance.

Description

Cathode for all-solid-state battery and all-solid-state battery containing same

[0001] This application claims the benefit of priority from Korean Patent Application No. 10-2023-0121061, dated September 12, 2023, the entire contents of which are incorporated herein by reference.

[0002] The present invention relates to a positive electrode for an all-solid-state battery and an all-solid-state battery including the same.

[0003] Various batteries are being studied to overcome the limitations of current lithium secondary batteries in terms of battery capacity, safety, output, large-scale development, and miniaturization.

[0004] Representative examples include metal-air batteries with much larger theoretical capacity than lithium secondary batteries, all-solid-state batteries with no risk of explosion in terms of safety, supercapacitors for output, NaS batteries or RFBs (redox flow batteries) for large-scale applications, and thin film batteries for miniaturization, all of which are being continuously researched in academia and industry.

[0005] Among the various next-generation batteries, all-solid-state batteries are batteries that replace the liquid electrolytes used in conventional lithium secondary batteries with solid electrolytes. Since they do not use flammable solvents within the battery, there is no risk of fire or explosion due to decomposition reactions of conventional electrolytes, which can significantly improve safety. Furthermore, among all-solid-state batteries, technological development is continuing for sulfide-based all-solid-state batteries, which have high ionic conductivity of solid electrolytes and can theoretically achieve high energy densities of over 900 Wh / L. Here, the term "sulfide-based all-solid-state battery" refers to an all-solid-state battery that contains a sulfide-based solid electrolyte.

[0006] In all-solid-state battery systems, lithium ion conduction does not occur through the liquid electrolyte contained in conventional lithium-ion batteries (LIBs). Therefore, when manufacturing a cathode for a sulfide-based all-solid-state battery, small-diameter sulfide-based solid electrolyte particles must be added to the inside of the cathode to increase the contact interface between the cathode active material and the sulfide-based solid electrolyte particles, thereby increasing lithium ion conduction. Furthermore, to improve energy density, the physical contact between the cathode active material, sulfide-based solid electrolyte particles, and other battery components within the cathode must be promoted, and the porosity of the cathode after rolling must be reduced, which must be maintained during charge and discharge.

[0007] Accordingly, there is a constant need for technological development that can further reduce porosity in the positive electrode of a sulfide-based all-solid-state battery and thereby improve the performance of the all-solid-state battery.

[0008] [Prior Art Literature]

[0009] [Patent Document]

[0010] (Patent Document 1) Japanese Patent Publication No. 2021-144906

[0011] The present inventors have conducted various studies to solve the above problems and, as a result, have confirmed that when manufacturing a positive electrode active material layer of an all-solid-state battery positive electrode, a positive electrode active material, a sulfide-based solid electrolyte and a conductive material are used, and the particle size of the conductive material is between the particle size of the positive electrode active material and the particle size of the sulfide-based solid electrolyte so as to fill the pores between the particles of the positive electrode active material and the sulfide-based solid electrolyte, and at the same time, the specific surface area of ​​the conductive material is limited to a certain level or less, the porosity of the positive electrode active material is reduced, thereby improving the energy density of the all-solid-state battery.

[0012] Accordingly, an object of the present invention is to provide a positive electrode for an all-solid-state battery with reduced porosity.

[0013] Another object of the present invention is to provide an all-solid-state battery including the positive electrode for an all-solid-state battery with reduced porosity.

[0014] In order to achieve the above object, the present invention provides an all-solid-state battery positive electrode comprising a positive electrode active material, a sulfide-based solid electrolyte, and a conductive material, wherein a particle size (D50) of the conductive material is between the particle size (D50) of the positive electrode active material and the particle size (D50) of the sulfide-based solid electrolyte, and a BET specific surface area of ​​the conductive material is 50 m2 / g or less.

[0015] The present invention also provides a positive electrode for an all-solid-state battery, wherein the particle diameter (D50) of the conductive material is 1.5 ㎛ to 3.8 ㎛.

[0016] The present invention also provides a positive electrode for an all-solid-state battery, wherein the bulk density of the conductive material is 0.05 g / cc or more.

[0017] The present invention also provides a positive electrode for an all-solid-state battery, wherein the true density of the conductive material is 1.5 g / cc or more.

[0018] The present invention also provides a positive electrode for an all-solid-state battery, wherein the crystal size (Lc(200)) of the conductive material is 30 nm to 80 nm.

[0019] The present invention also provides a positive electrode for an all-solid-state battery, wherein the particle size (D50) of the positive electrode active material is 4.0 ㎛ to 8.0 ㎛.

[0020] The present invention also provides a positive electrode for an all-solid-state battery, wherein the particle size (D50) of the sulfide-based solid electrolyte is 0.1 ㎛ to 1.5 ㎛.

[0021] The present invention also provides a positive electrode for an all-solid-state battery, wherein the positive electrode is in the form of a pellet including a positive electrode active material, a sulfide-based solid electrolyte, and a conductive material.

[0022] The present invention also comprises: the positive electrode, a positive electrode current collector; and a positive electrode active material layer formed on one surface of the positive electrode current collector;

[0023] The above-mentioned positive electrode active material layer provides a positive electrode for an all-solid-state battery, which includes a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder.

[0024] The present invention also provides a method for producing a composition comprising the binder comprising: polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, A positive electrode for an all-solid-state battery is provided, comprising at least one selected from the group consisting of polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene.

[0025] The present invention also provides a positive electrode for an all-solid-state battery, wherein the conductive material may include graphite, and the graphite is at least one selected from the group consisting of natural graphite and artificial graphite.

[0026] The present invention also provides a positive electrode for an all-solid-state battery, wherein the porosity of the positive electrode active material layer is 5 vol% to 16 vol%.

[0027] The present invention also provides that the positive electrode active material is included in an amount of 55 to 90 wt% based on the total weight of the positive electrode active material layer,

[0028] The above sulfide-based solid electrolyte is included in an amount of 10 to 50 wt% based on the total weight of the positive electrode active material layer,

[0029] The present invention provides a positive electrode for an all-solid-state battery, wherein the above-mentioned conductive material is included in an amount of 0.05 to 10 wt% based on the total weight of the positive electrode active material layer.

[0030]

[0031] The present invention also provides an all-solid-state battery comprising the positive electrode, the negative electrode, and the solid electrolyte membrane interposed therebetween.

[0032] According to the positive electrode for an all-solid-state battery of the present invention, the conductive material fills the pores between the particles of the positive electrode active material and the sulfide-based solid electrolyte, thereby reducing the porosity of the positive electrode, thereby improving the energy density of the all-solid-state battery. Furthermore, the conductive material can exhibit the effect of increasing the electrical conductivity of the entire positive electrode by filling the pores of the positive electrode.

[0033] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0034] The terms and words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term to explain his or her own invention in the best way.

[0035] In this specification, in order to distinguish between positive electrodes manufactured according to whether or not the positive electrode active material layer includes a binder, when the positive electrode does not include a binder, it may be referred to as a “composite positive electrode,” and when the positive electrode includes a binder, it may be referred to as a “positive electrode.”

[0036]

[0037] Cathode for all-solid-state batteries

[0038] The present invention relates to a positive electrode for an all-solid-state battery.

[0039] The positive electrode for an all-solid-state battery according to the present invention includes a positive electrode active material, a sulfide-based solid electrolyte, and a conductive material.

[0040] In one embodiment of the present invention, the positive electrode may be in the form of a pellet. The positive electrode in the form of a pellet may be used in a current collector-free form, or the positive electrode may be formed by placing the pellet on a current collector. The pellet may be formed by pressing a composite powder containing a positive electrode active material, a sulfide-based solid electrolyte, and a conductive material. Since the pellet does not contain a binder, resistance that may be caused by the binder can be eliminated.

[0041] In another embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on one surface of the positive electrode current collector. The positive electrode active material layer may include the positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder.

[0042] The particle size (D50) of the conductive material may be between the particle size (D50) of the positive electrode active material and the particle size (D50) of the sulfide-based solid electrolyte, and the conductive material may have a BET specific surface area of ​​50 m2 / g or less. The conductive material may have a crystal form with a lattice structure. In the present specification, a positive electrode that does not include a binder may correspond to a composite positive electrode.

[0043] In the positive electrode for an all-solid-state battery according to the present invention, a gap is formed due to a difference in particle size between the positive electrode active material and the sulfide-based solid electrolyte, and the gap is filled with the conductive material, so that the porosity of the positive electrode is reduced, thereby improving the energy density. Since the particle size (D50) of the conductive material is larger than the particle size (D50) of the sulfide-based solid electrolyte and smaller than the particle size (D50) of the positive electrode active material, the gap can be filled with the conductive material.

[0044]

[0045] In one embodiment of the present invention, the BET specific surface area of ​​the conductive material may be 50 m2 / g or less. Specifically, the specific surface area of ​​the conductive material may be 50 m2 / g or less, 45 m2 / g or less, 40 m2 / g or less, 35 m2 / g or less, 30 m2 / g or less, 25 m2 / g or less, or 20 m2 / g or less. When the BET specific surface area exceeds 50 m2 / g, the contact interface between the conductive material with a high specific surface area and the sulfide-based all-solid-state electrolyte increases, thereby increasing the electrolyte decomposition reaction and decreasing the ionic conductivity of the positive electrode itself. In addition, the lower limit of the BET specific surface area is not particularly limited, but may be 5 m2 / g or more.

[0046] In addition, the particle diameter (D50) of the conductive material may be 1.5 ㎛ to 3.8 ㎛. Specifically, the particle diameter (D50) of the conductive material may be 1.5 ㎛ or more, 1.7 ㎛ or more, 2.0 ㎛ or more, or 2.2 ㎛ or more, and may be 2.6 ㎛ or less, 2.8 ㎛ or less, 3.0 ㎛ or less, 3.2 ㎛ or less, 3.4 ㎛ or less, 3.6 ㎛ or less, or 3.8 ㎛ or less. If the particle size (D50) of the conductive agent is less than 1.5 ㎛, the particles are excessively small, so that the conductive agent may be adsorbed only on the surface of the positive electrode active material rather than filling the pores formed by the particle size difference between the particles of the positive electrode active material and the sulfide-based solid electrolyte. If the particle size exceeds 3.8 ㎛, it is difficult to fill the pores formed by the particle size difference between the particles of the positive electrode active material and the sulfide-based solid electrolyte, so that the effect of reducing the porosity of the positive electrode may be minimal.

[0047] The above particle size (D50) can be measured by introducing a conductive material into a particle size analyzer (Mastersizer 3000, Malvern).

[0048]

[0049] Additionally, the bulk density of the above-mentioned challenge material may be 0.05 g / cc or more.

[0050] Specifically, the bulk density may be 0.05 g / cc or more, 0.06 g / cc or more, or 0.07 g / cc or more. If the bulk density is less than 0.05 g / cc, the density of the conductive material itself may be low, which may reduce the overall density of the anode. The upper limit of the bulk density is not particularly limited, but may be 0.1 g / cc or less, 0.3 g / cc or less, or 0.5 g / cc or less.

[0051] The above bulk density can be measured using a densitometer following the ASTM D 1895 method.

[0052]

[0053] Additionally, the true density of the above-mentioned challenge material may be 1.5 g / cc or more.

[0054] Specifically, the true density may be 1.5 g / cc or more, 1.7 g / cc or more, 2.0 g / cc or more, or 2.2 g / cc or more. If the true density is less than 1.5 g / cc, the density of the conductive material itself may be low, which may reduce the overall density of the anode. The upper limit of the true density is not particularly limited, but may be 3.0 g / cc or less, 4.0 g / cc or less, or 5.0 g / cc or less.

[0055] The above true density can be measured using a densitometer following the ASTM D 1895 method.

[0056]

[0057] Additionally, the above-mentioned conductive material may have a c-axis direction crystal size (Lc(002)) of 30 nm to 80 nm when measured by XRD.

[0058] Specifically, the crystal size may be 30 nm or more, 35 nm or more, or 40 nm or more, and 65 nm or less, 70 nm or less, 75 nm or less, or 80 nm or less.

[0059] The crystal size in the c-axis direction above represents Lc(002), which is the crystal size in the c-axis direction when measured by XRD, and can be calculated by Scherrer's equation in the following mathematical equation 1.

[0060] <Mathematical Formula 1>

[0061]

[0062] K = Scherrer's constant (K=0.9)

[0063] ß= half-price range

[0064] λ = wavelength (0.154056 nm)

[0065] θ = angle at maximum peak

[0066]

[0067] In addition, the conductive material may include graphite, and the graphite may include at least one selected from the group consisting of natural graphite and artificial graphite, but is not limited thereto as long as the conductive material has the specific surface area, particle size, and crystal structure described above. Preferably, the conductive material may be artificial graphite.

[0068] The above natural graphite may be produced as a conductive material by mining graphite that exists in nature, going through a refining process, and then using the graphite.

[0069] Since the above artificial graphite is formed by applying high heat of 2,500℃ or higher to form a crystal structure, it can have a more stable crystal structure than natural graphite, and it is advantageous for charging and discharging because there are many movement paths for lithium ions.

[0070] In addition, the conductive material may be included in an amount of 0.05 to 10 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the conductive material may be 0.05 wt% or more, 0.1 wt% or more, 0.5 wt% or more, 1 wt% or more, 2 wt% or more, or 3 wt% or more, and may be 5 wt% or less, 7 wt% or less, or 10 wt% or less. If the content of the conductive material is less than 0.05 wt%, the electrical conductivity of the positive electrode may be reduced, and if it exceeds 10 wt%, the content of the positive electrode active material and the sulfide-based solid electrolyte may be relatively reduced, thereby deteriorating battery performance.

[0071]

[0072] In one embodiment of the present invention, the particle size (D50) of the positive electrode active material may be 4.0 ㎛ to 8.0 ㎛.

[0073] Specifically, the particle size (D50) of the positive electrode active material may be 4.0 ㎛ or more, 4.5 ㎛ or more, or 5.0 ㎛ or more, and may be 6.0 ㎛ or less, 6.5 ㎛ or less, 7.0 ㎛ or less, 7.5 ㎛ or less, or 8.0 ㎛ or less. If the particle size (D50) of the positive electrode active material is less than 4.0 ㎛, even if the positive electrode active material and the sulfide-based solid electrolyte are dispersed at the same weight ratio, the particle size of the positive electrode active material may be small, which may reduce dispersibility, and if it exceeds 8.0 ㎛, excessively large pores may be formed within the positive electrode active material layer, which may reduce the performance of the all-solid-state battery.

[0074] The above particle size (D50) can be measured by putting the positive electrode active material powder into a particle size analyzer (Mastersizer 3000, Malvern).

[0075] In addition, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions, and examples thereof include lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), and Li[Ni x Co y Mn z M v ]O2 (wherein M is one or two or more elements selected from the group consisting of Al, Ga, and In; 0.3≤x<1.0, 0≤y, z≤0.5, 0≤v≤0.1, x+y+z+v=1), Li(Li a M b-a-b' M' b' )O 2-c A c(In the above formula, 0≤a≤0.2, 0.6≤b≤1, 0≤b'≤0.2, 0≤c≤0.2; M includes at least one selected from the group consisting of Mn and Ni, Co, Fe, Cr, V, Cu, Zn and Ti; M' is at least one selected from the group consisting of Al, Mg and B, and A is at least one selected from the group consisting of P, F, S and N.) layered compounds or compounds substituted with one or more transition metals; chemical formula Li 1+y Mn 2-y Lithium manganese oxides such as O4 (where y is 0 to 0.33), LiMnO3, LiMn2O3, LiMnO2; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7; chemical formula LiNi 1-y Ni-site type lithium nickel oxide represented by MyO2 (wherein, M=Co, Mn, Al, Cu, Fe, Mg, B or Ga, and y is 0.01 to 0.3); chemical formula LiMn 2-y M y Lithium manganese composite oxides represented by O2 (wherein M is Co, Ni, Fe, Cr, Zn or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (wherein M is Fe, Co, Ni, Cu or Zn); LiMn2O4 in which a portion of Li in the chemical formula is replaced by an alkaline earth metal ion; disulfide compounds; Fe2(MoO4)3, etc., but are not limited thereto.

[0076] In addition, the positive electrode active material may be included in an amount of 55 to 90 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the positive electrode active material may be 55 wt%, 60 wt% or more, or 65 wt% or more, and may be 83 wt% or less, 85 wt% or less, or 90 wt% or less. If the content of the positive electrode active material is less than 55 wt%, battery performance may deteriorate, and if it is more than 90 wt%, mass transfer resistance may increase.

[0077]

[0078] In one embodiment of the present invention, the particle size (D50) of the sulfide-based solid electrolyte may be 0.1 ㎛ to 1.5 ㎛.

[0079] Specifically, the particle size (D50) of the sulfide-based solid electrolyte may be 0.1 ㎛ or more, 0.3 ㎛ or more, or 0.5 ㎛ or more, and may be 0.9 ㎛ or less, 1.0 ㎛ or less, 1.2 ㎛ or less, or 1.5 ㎛ or less. If the particle size (D50) of the sulfide-based solid electrolyte is less than 0.1 ㎛, the ultrafine solid electrolyte particles may not be sufficiently dispersed within the positive electrode layer and may aggregate, and if it exceeds 1.5 ㎛, dispersion may be somewhat easy, but the contact surface with the positive electrode active material particles may decrease and the positive electrode porosity may increase.

[0080] In addition, the sulfide-based solid electrolyte may include at least one selected from the group consisting of LiPSX (X = Cl, Br or I), LiGePS, and LiPS. However, the sulfide-based solid electrolyte is not limited to these, and a sulfide-based solid electrolyte commonly used in the art can be widely used.

[0081] In addition, the sulfide-based solid electrolyte may be included in an amount of 10 to 50 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the sulfide-based solid electrolyte may be 10 wt% or more, 20 wt% or more, or 30 wt% or more, and may be 40 wt% or less, 45 wt% or less, or 50 wt% or less. If the content of the positive electrode active material is less than 10 wt%, it may not be sufficient to fill the pores formed in the positive electrode active material layer, making it difficult to reduce the porosity of the positive electrode active material. If it exceeds 50 wt%, the content of the positive electrode active material and the conductive material may be relatively reduced, resulting in deterioration in battery performance.

[0082]

[0083] In one embodiment of the present invention, the positive electrode active material layer may further include a binder. The binder may be included to facilitate bonding between materials included in the positive electrode active material layer and between the positive electrode active material layer and the positive electrode current collector. The binder may promote bonding between materials included in the positive electrode active material layer, thereby further reducing the positive electrode porosity.

[0084] The above binder may be a fibrous binder. During the mixing process of manufacturing the positive electrode, the binder may undergo fiberization and be incorporated into the positive electrode active material layer in a fibrous form. Therefore, it is preferable that the binder have physical properties that can be easily modified.

[0085] In addition, the binder is polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, It may include at least one selected from the group consisting of polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0086] In addition, the binder may be included in an amount of 0.1 to 3 wt% based on the total weight of the positive electrode active material layer. Specifically, the content of the binder may be 0.1 wt% or more, 0.5 wt% or more, or 0.8 wt% or more, and may be 1.5 wt% or less, 2 wt% or less, or 3 wt% or less. If the content of the binder is less than 0.1 wt%, the effect of improving the bonding strength between materials included in the positive electrode active material layer may be minimal, and thus the electrode sheet may not be properly formed. If the content of the binder is more than 3 wt%, ionic conductivity or electrical conductivity may be reduced.

[0087]

[0088] In one embodiment of the present invention, the porosity of the positive electrode active material layer may be 5 vol% to 16 vol%.

[0089] Specifically, the porosity may be 5 vol% or more, 8 vol% or more, 10 vol% or more, or 13 vol% or more, and may be 13.8 vol% or less, 14 vol% or less, 14.5 vol% or less, 15 vol% or less, 15.5 vol% or less, or 16 vol% or less. The porosity is an optimized range considering performance such as the energy density of the battery, and if the porosity exceeds 16 vol%, the energy density of the battery may be reduced.

[0090]

[0091] In one embodiment of the present invention, the positive electrode current collector supports the positive electrode active material layer and serves to transfer electrons between the external conductor and the positive electrode active material layer.

[0092] The positive electrode current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes in the all-solid-state battery. For example, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, stainless steel surface-treated with carbon, nickel, silver, etc., aluminum-cadmium alloy, etc. can be used as the positive electrode current collector.

[0093] The positive electrode current collector may have a finely irregular structure on its surface or may employ a three-dimensional porous structure to strengthen the bonding strength with the positive electrode active material layer. Accordingly, the positive electrode current collector may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, or non-woven fabric.

[0094]

[0095] Method for manufacturing a cathode for an all-solid-state battery

[0096] The present invention also relates to a method for manufacturing a positive electrode for an all-solid-state battery. The specific materials, properties, and contents of the positive electrode active material, sulfide-based solid electrolyte, conductive agent, and binder used in the method for manufacturing a positive electrode for an all-solid-state battery according to the present invention are as described above.

[0097] In the present invention, the positive electrode may be referred to as a “composite positive electrode” when it does not contain a binder, or as a “positive electrode” when it contains a binder, depending on whether or not it contains a binder.

[0098] In one embodiment of the present invention, a method for manufacturing a composite positive electrode not including a binder may include: (A1) a step of mixing a positive electrode active material, a sulfide-based solid electrolyte, and a conductive material; and (A2) a step of manufacturing the mixed powder obtained in step (A1) into a pellet form. At this time, the pellet form in step (A2) may be formed by pressing with a jig.

[0099] The composite anode manufactured as described above can be applied to a pressure jig cell. Since the composite anode does not contain a binder, the binder's resistance factor can be eliminated. Therefore, the composite anode can be used to conduct performance evaluations using a pressure jig cell, eliminating the resistance factor.

[0100]

[0101] In addition, in one embodiment of the present invention, a method for manufacturing a positive electrode including a binder includes: (B1) a step of mixing a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder; (B2) a step of applying the mixed powder obtained in step (B1) to a calendaring process to form it into a film shape; and (B3) a step of attaching a positive electrode active material layer in a film shape obtained in step (B2) to a positive electrode current collector.

[0102] The mixing in step (B1) above may be physical mixing, and the physical mixing may cause the binder to be fiberized. During the physical mixing, the binder may be physically deformed by friction with the particles in the mixed powder due to shear force, thereby causing fiberization. For example, PTFE, which has properties that facilitate physical deformation, may be used as the binder. Furthermore, to facilitate physical deformation, the mixing may be performed by introducing an induction heating device, ball milling, or roll pressing.

[0103]

[0104] Additionally, in the above step (B2), the mixed powder obtained in the above step (B1) can be formed into a film shape by applying a calendaring process.

[0105] The conditions for the above-mentioned calendering process may be applied by appropriately controlling process conditions that can be formed into a film form. For example, the calendering process may be performed at a temperature of 50°C to 200°C for 5 to 50 loops. However, any of the calendering process conditions, such as temperature, pressure, and number of loops, that are used in electrode manufacturing processes commonly used in the battery field may be used.

[0106]

[0107] In addition, in the step (B3), a film-shaped positive electrode active material layer obtained in the step (B2) can be attached to a positive electrode current collector to manufacture a positive electrode for an all-solid-state battery.

[0108]

[0109] All-solid-state batteries

[0110] The present invention also relates to an all-solid-state battery including the above sulfide-based solid electrolyte layer.

[0111] The all-solid-state battery according to the present invention comprises the positive electrode, the negative electrode, and a sulfide-based solid electrolyte layer interposed therebetween. The positive electrode is as described above.

[0112]

[0113] In one embodiment of the present invention, the negative electrode includes a negative electrode active material layer, and the negative electrode active material layer may be formed on one surface of a negative electrode current collector.

[0114] The above negative active material layer may include a negative active material, a conductive material, and a binder. Alternatively, the negative active material layer may be an anodeless layer.

[0115]

[0116] In the above negative electrode active material layer, the negative electrode active material is lithium (Li + ) can be reversibly intercalated or deintercalated, a material that can react with lithium ions to form a reversibly lithium-containing compound, or a lithium metal or a lithium alloy.

[0117] The above lithium ion (Li + ) can be reversibly inserted or de-inserted, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The lithium ion (Li + ) can be, for example, tin oxide, titanium nitrate or silicon. The lithium alloy can be, for example, an alloy of lithium (Li) and a metal selected from the group consisting of indium (In), sodium (Na), potassium (K), rubidium (Rb), cesium (Cs), francium (Fr), beryllium (Be), magnesium (Mg), calcium (Ca), strontium (Sr), barium (Ba), radium (Ra), aluminum (Al) and tin (Sn).

[0118] Preferably, the negative electrode active material may be lithium metal or a lithium-indium alloy (Li-In), and specifically, may be in the form of lithium metal or lithium and a thin film or a lithium-indium alloy thin film or powder.

[0119] The negative electrode active material may be included in an amount of 40 to 80 wt% based on the total weight of the negative electrode active material layer. Specifically, the content of the negative electrode active material may be 40 wt% or more or 50 wt% or more, and 70 wt% or less or 80 wt% or less. If the content of the negative electrode active material is less than 40 wt%, the connectivity between the wet negative electrode active material layer and the dry negative electrode active material layer may be insufficient, and if it exceeds 80 wt%, the material transfer resistance may increase.

[0120] In addition, the binder is a component that assists in the bonding of the negative electrode active material and the conductive material and the bonding to the negative electrode current collector, and includes styrene-butadiene rubber, acrylated styrene-butadiene rubber, acrylonitrile copolymer, acrylonitrile-butadiene rubber, nitrile butadiene rubber, acrylonitrile-styrene-butadiene copolymer, acrylic rubber, butyl rubber, fluorine rubber, polytetrafluoroethylene, polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose It may include at least one selected from the group consisting of acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethylsucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene. Preferably, the binder may include polytetrafluoroethylene (PTFE).

[0121] In addition, the binder may be included in an amount of 0.5 wt% to 4 wt% based on the total weight of the negative electrode active material layer, and specifically, the content of the binder may be 0.5 wt% or more, 1 wt% or more, or 1.5 wt% or more, and 3 wt% or less, 3.5 wt% or less, or 4 wt% or less. If the content of the binder is less than 0.5 wt%, the adhesive strength between the positive electrode active material and the negative electrode current collector may be reduced, and if it exceeds 4 wt%, the adhesive strength may be improved, but the content of the negative electrode active material may be reduced, which may lower the battery capacity.

[0122]

[0123] In addition, the conductive material is not particularly limited as long as it prevents side reactions in the internal environment of the all-solid-state battery, does not cause chemical changes in the battery, and has excellent electrical conductivity. Representative examples thereof include graphite or conductive carbon, and examples thereof include graphite such as natural graphite and artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, and summer black; carbon-based materials having a crystal structure of graphene or graphite; conductive fibers such as carbon fiber and metal fiber; fluorinated carbon; metal powder such as aluminum powder and nickel powder; conductive whiskey such as zinc oxide and potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives; which may be used alone or in combination of two or more thereof, but are not necessarily limited thereto. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

[0124] The conductive material may typically be included in an amount of 1 wt% to 5 wt% based on the total weight of the negative electrode active material layer, and specifically, the content of the conductive material may be 1 wt% or more, 1.5 wt% or more, or 2 wt% or more, and 4 wt% or less, 4.5 wt% or less, or 5 wt% or less. If the content of the conductive material is too low, such as less than 1 wt%, it may be difficult to expect an effect of improving electrical conductivity or the electrochemical characteristics of the battery may deteriorate, and if it exceeds 5 wt%, the amount of the negative electrode active material may be relatively small, which may lower the capacity and energy density. The method of including the conductive material in the negative electrode is not particularly limited, and conventional methods known in the art, such as mixing with the negative electrode active material or coating, may be used.

[0125] In addition, the negative electrode current collector is not particularly limited as long as it is conductive and does not cause a chemical change in the battery. For example, the negative electrode current collector may be made of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., an aluminum-cadmium alloy, etc. In addition, the negative electrode current collector, like the positive electrode current collector, may be made of various forms such as a film, sheet, foil, net, porous body, foam, non-woven fabric, etc. having fine irregularities formed on the surface.

[0126] The method for manufacturing the above negative electrode is not particularly limited, and can be manufactured by forming a negative electrode active material layer on the negative electrode current collector using a method for forming a layer or film commonly used in the art. For example, methods such as compression, coating, and deposition can be used. In addition, a case in which a battery is assembled on the negative electrode current collector without a lithium thin film and then a metallic lithium thin film is formed on the metal plate through initial charging is also included in the negative electrode of the present invention.

[0127]

[0128] In addition, the above-mentioned non-cathode layer refers to a cathode layer in which lithium metal or lithium alloy, which can be a lithium source among the cathode active materials, does not exist in the cathode when the battery is first assembled, and lithium is deposited in the cathode through charging. A battery including the above-mentioned non-cathode layer can be referred to as a cathode-free battery.

[0129] In the above negative electrode-free battery, while the battery is being charged and discharged, lithium ions released from the positive electrode move to the negative electrode to form a negative electrode active material layer. For example, when the battery is being charged, lithium ions are desorbed from the positive electrode active material and move to the negative electrode, forming a lithium metal layer in the form of a layer on the negative electrode current collector, which is purely composed of lithium, or a lithium metal structure in an arbitrary form other than a layer form can be formed. The arbitrary form can be, for example, a structure in which lithium metal is aggregated in the form of particles.

[0130]

[0131] In one embodiment of the present invention, the sulfide-based solid electrolyte included in the sulfide-based solid electrolyte layer may include at least one selected from the group consisting of LiPSX (X = Cl, Br or I), LiGePS, and LiPS. However, the sulfide-based solid electrolyte is not limited to these, and a sulfide-based solid electrolyte commonly used in the art can be widely used.

[0132]

[0133] battery module

[0134] The present invention also relates to a battery module including the all-solid-state battery as a unit battery, a battery pack including the battery module, and a device including the battery pack as a power source.

[0135] At this time, specific examples of the device include, but are not limited to, a power tool that is powered by an electric motor; an electric vehicle including an electric vehicle (EV), a hybrid electric vehicle (HEV), a plug-in hybrid electric vehicle (PHEV), etc.; an electric two-wheeled vehicle including an electric bicycle (E-bike) and an electric scooter (E-scooter); an electric golf cart; and a power storage system.

[0136]

[0137] Hereinafter, preferred examples are presented to help understand the present invention, but the following examples are only illustrative of the present invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea of ​​the present invention, and it is also natural that such changes and modifications fall within the scope of the appended patent claims.

[0138]

[0139] In the following examples and comparative examples, a positive electrode and an all-solid-state battery including the same were manufactured using a conductive material having the properties described in Table 1 below, according to the composition of the positive electrode active material layer and the properties of the raw materials described in Table 2 below.

[0140]

[0141] Conductive material Graphite A (Imerys) Graphite B (Imerys) Carbon black Specific surface area (㎡ / g) < 30 < 30~1300 D50 (㎛) 2.4 3.5 0.5 Bulk density (g / cc) 0.07 0.06 0.03 True density (g / cc) 2.25 5 2.25 5 1.8 Lc (0.02) (nm) 60 75 < 5

[0142]

[0143] Composition (wt%) of the positive electrode active material layer Properties of raw materials Conductive material Positive electrode active material Sulfide-based solid electrolyte Positive electrode active material Sulfide-based solid electrolyte Conductive material Binder BET specific surface area (㎡ / g) Particle size (D50) (㎛) Particle size (D50) (㎛) Particle size (D50) (㎛) Example 160355 (Graphite A) - < 302.4 5.30.8 Example 27819.51 (Graphite A) 1.5 < 302.4 5.30.8 Example 360355 (Graphite B) - < 303.5 5.30.8 Example 47819.51 (Graphite B) 1.5 < 303.5 5.30.8 Comparative example 160355 (Carbon Black) - ~13000.55.30.8 Comparative Example 27819.51 (Carbon Black) 1.5~13000.55.30.8

[0144]

[0145] Example 1: Preparation of composite anode

[0146] LiN as a cathode active material 0.8 Co 0.1 Mn 0.1 A positive electrode was manufactured as follows using O2 (NCM 811), Li6PS5Cl as a sulfide-based solid electrolyte, and graphite A as a conductive material. The properties of the graphite A are as described in Table 1 above.

[0147] Powder mixing was performed with a weight ratio of 60:35:5 for the positive active material, sulfide-based solid electrolyte, and conductive agent. Specifically, the positive active material and sulfide-based solid electrolyte were quantified in powder form and mixed for 15 minutes using an agate mortar in a dry room environment to obtain a mixture. Thereafter, the conductive agent was quantified and added to the mixture, followed by mixing for an additional 15 minutes to obtain a mixed powder.

[0148] The above mixed powder was pressurized using a pressurizing jig to produce a composite positive electrode in the form of a pellet with a loading of 3 mAh / cm2.

[0149]

[0150] Example 2: Anode fabrication

[0151] LiN as a cathode active material 0.8 Co 0.1 Mn 0.1 A positive electrode was manufactured as follows using O2 (NCM 811), Li6PS5Cl as a sulfide-based solid electrolyte, graphite A as a conductive material, and polytetrafluoroethylene (PTFE) as a binder. The properties of the graphite A are as described in Table 1.

[0152] Powder mixing was performed with a weight ratio of 78:19.5:1:1.5 for the positive active material, sulfide-based solid electrolyte, conductive agent, and binder. Specifically, the positive active material and sulfide-based solid electrolyte were quantified in powder form and then mixed for 15 minutes using a blade mixer in a dry room environment to obtain a mixture. After that, the conductive agent was quantified and added to the mixture, and then mixed. The binder PTFE (Polytetrafluoroethylene) powder was quantified and further mixed to obtain a mixed powder.

[0153] After the above mixed powder was injected into the inducer, fiberization was performed in the inducer, and calendaring was performed on a roller to manufacture a positive electrode with a loading of 6 mAh / cm2.

[0154]

[0155] Example 3: Preparation of composite anode

[0156] The same procedure as Example 1 was followed, except that graphite B was used instead of graphite A as the conductive material. The properties of the graphite B are as described in Table 1 above.

[0157]

[0158] Example 4: Anode fabrication

[0159] The same procedure as Example 2 was followed, except that graphite B was used instead of graphite A as the conductive agent. The properties of the graphite B are as described in Table 1 above.

[0160]

[0161] Comparative Example 1

[0162] The same procedure as Example 1 was followed, except that carbon black was used instead of graphite A as the conductive agent. The properties of the carbon black are as described in Table 1 above.

[0163]

[0164] Comparative Example 2

[0165] The same procedure as Example 2 was followed, except that carbon black was used instead of graphite A as the conductive agent. The properties of the carbon black are as described in Table 1 above.

[0166]

[0167] Experimental Example 1: Performance Evaluation of All-Solid-State Battery

[0168] The performance of all-solid-state batteries was evaluated according to the type of conductive material within the positive electrode active material layer. The composite positive electrodes manufactured in Examples 1, 3, and Comparative Example 1 were evaluated.

[0169] To evaluate the performance of the above all-solid-state battery, a pressure jig cell was manufactured using the following method.

[0170] After transferring the composite anode in the form of a pellet to a pressure jig cell, a sulfide-based solid electrolyte powder (200 mg) was placed on the pellet, and pressurized with a force of 400 Mpa for 60 seconds to form a membrane-like sulfide-based solid electrolyte layer. Thereafter, a lithium metal negative electrode was placed facing one side of the sulfide-based solid electrolyte layer, and pressurized again with a force of 100 Mpa to increase the contact between the sulfide-based solid electrolyte layer and the negative electrode. Thereafter, the pressure jig cell was manufactured by fastening with an appropriate pressure.

[0171] The capacity capability was observed through a protocol in which the pressure jig cell was activated in a charger / discharger at 0.05 C for 2 cycles and then discharged up to 1 C, and the results are shown in Tables 3 and 4 below. Specifically, the capacity capability was observed through a protocol in which 0.05 C CC / CV (Constant Current / Constant Voltage) charging, 0.05 C CC (Constant Current) discharge 2 cycles, and then 0.1 C CC / CV charging was maintained, but CC discharge was performed at 0.1 C / 0.2 C / 0.33 C / 0.5 C / 1 C.

[0172]

[0173] Voltage range / temperature 3.0 ~ 4.25 V / 60℃ Classification Example 1 Example 3 Comparative Example 1 Loading (mAh / ㎠) 31 st Charging capacity (0.05C) mAh / g 2202082641 st Discharge capacity (0.05C) 204195210 Efficiency % 9394792 nd Charging capacity (0.05C) mAh / g 2091972252 nd Discharge capacity (0.05C) 201194204 Efficiency % 969891

[0174]

[0175] Referring to Table 3 above, Examples 1 and 3 have particle diameters (D 50 ) was between the particle size of the positive electrode active material and the particle size of the sulfide-based solid electrolyte, and when graphite A and graphite B having a low specific surface area of ​​< 30 ㎡ / g were used, it was confirmed that the comparative example 1 using carbon black having a high specific surface area of ​​~ 1300 ㎡ / g as the conductive material showed superior performance in terms of discharge capacity. In addition, it was confirmed that the initial charge capacity of comparative example 1 rapidly increased, resulting in a decrease in efficiency, and that it showed lower efficiency than examples 1 and 3 even during the second charge / discharge.

[0176]

[0177] mAh (%)Example 1Example 3Comparative Example 1Rate (0.1C charge)0.1C1971901880.2C1911741630.33C1831591370.5C173163761.0C15415028

[0178]

[0179] Referring to Table 4 above, it was confirmed that Examples 1 and 3 had superior discharge capacity retention rates compared to Comparative Example 1. Specifically, Examples 1 and 3 maintained a discharge capacity of 150 mAh / g even at 1C discharge, while Comparative Example 1 had a measured discharge capacity of 28 mAh / g. This is due to the phenomenon that when the specific surface area of ​​the carbon material in the composite positive electrode is high (Comparative Example 1), the decomposition reaction of the sulfide-based solid electrolyte in contact with the carbon material is accelerated as the c-rate increases.

[0180]

[0181] Experimental Example 2: Confirming the Internal Structure of the Anode

[0182] An experiment was conducted to measure the internal structure of a positive electrode according to the type of conductive agent within the positive electrode active material layer including a binder. Examples 2, 4, and Comparative Example 2 were evaluated. All of these include a binder in the positive electrode active material layer. Examples 2, 4, and Comparative Example 2 all use a binder in the manufacture of the positive electrode. Example 2 includes graphite A as a conductive agent, Example 4 includes graphite B as a conductive agent, and Comparative Example 2 includes carbon black as a conductive agent. As shown in Table 1 above, carbon black has a significantly larger specific surface area than graphite A and graphite B.

[0183] The anodes manufactured according to Examples 2, 4, and Comparative Example 2 were further pressed using WIP (Warm Isostatic Press) to form a completely sealed anode element, and then the thickness and porosity were measured, and the results are shown in Table 5 below. At this time, the porosity was measured using the anode density calculated from 1) the thickness of the anode after WIP rolling, 2) the weight of the anode, 3) the area of ​​the anode, and 4) the true density of the anode elements used, according to the following mathematical equation 2.

[0184]

[0185] <Mathematical Formula 2>

[0186] Anode porosity (%) = (1-([Anode weight] / [Anode area x Anode thickness] / [Anode density] x 100)

[0187]

[0188] Example 2 Example 4 Comparative Example 2 Loading (mAh / cm2) 666 Thickness of pre-rolled anode (㎛) 155.8 156.3 168.4 Porosity (%) 32.9 33.1 37.9 Thickness of post-rolled anode (㎛) 121 122.5 126.3 Porosity (%) 13.6 14.7 17.2

[0189]

[0190] Referring to Table 5 above, the anode thickness and porosity of Examples 2 and 4 were found to be smaller than those of Comparative Example 2 both before and after rolling. From this, it can be seen that graphite A and graphite B, which have smaller specific surface areas than carbon black, effectively fill the pores within the anode, thereby reducing the anode thickness and porosity.

[0191] Therefore, in Example 2, when the particle size of the conductive agent is between the particle size of the positive electrode active material and the particle size of the sulfide-based solid electrolyte and has a low specific surface area, it can be predicted that the porosity of the positive electrode active material layer will be reduced, thereby increasing the performance of the positive electrode.

Claims

1. A positive electrode for an all-solid-state battery comprising a positive electrode active material, a sulfide-based solid electrolyte, and a conductive material, The particle size (D50) of the above-mentioned conductive material is between the particle size (D50) of the positive electrode active material and the particle size (D50) of the sulfide-based solid electrolyte, A positive electrode for an all-solid-state battery, wherein the BET specific surface area of ​​the above-mentioned conductive material is 50 m2 / g or less.

2. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the particle size (D50) of the above-mentioned conductive material is 1.5 ㎛ to 3.8 ㎛.

3. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the bulk density of the above-mentioned conductive material is 0.05 g / cc or more.

4. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the true density of the above-mentioned conductive material is 1.5 g / cc or more.

5. In paragraph 1, A cathode for an all-solid-state battery, wherein the crystal size (Lc(200)) of the above-mentioned conductive material is 30 nm to 80 nm.

6. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the particle size (D50) of the positive electrode active material is 4.0 ㎛ to 8.0 ㎛.

7. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the particle size (D50) of the above sulfide-based solid electrolyte is 0.1 ㎛ to 1.5 ㎛.

8. In paragraph 1, An all-solid-state battery positive electrode, wherein the positive electrode is in the form of a pellet containing a positive electrode active material, a sulfide-based solid electrolyte, and a conductive material.

9. In paragraph 1, The above positive electrode includes a positive electrode current collector; and a positive electrode active material layer formed on one surface of the positive electrode current collector, An all-solid-state battery positive electrode, wherein the positive electrode active material layer comprises a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder.

10. In paragraph 9, The above binder is polytetrafluoroethylene (PTFE), polyethylene, polypropylene, ethylene / propylene copolymer, polybutadiene, polyethylene oxide, chlorosulfonated polyethylene, polyvinylpyrrolidone, polyvinylpyridine, polyvinyl alcohol, polyvinyl acetate, polyepichlorohydrin, polyphosphazene, polyacrylonitrile, polystyrene, latex, acrylic resin, phenol resin, epoxy resin, carboxymethylcellulose, hydroxypropyl cellulose, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethylcellulose, cyanoethyl sucrose, polyester, polyamide, polyether, polyimide, polycarboxylate, polycarboxylic acid, polyacrylic acid, polyacrylate, lithium polyacrylate, polymethacrylic acid, An all-solid-state battery positive electrode comprising at least one selected from the group consisting of polymethacrylate, polyacrylamide, polyurethane, polyvinylidene fluoride, and poly(vinylidene fluoride)-hexafluoropropene.

11. In paragraph 1, An all-solid-state battery positive electrode, wherein the above-mentioned conductive material comprises graphite, and the graphite is at least one selected from the group consisting of natural graphite and artificial graphite.

12. In paragraph 1, A positive electrode for an all-solid-state battery, wherein the porosity of the positive electrode active material layer is 5 vol% to 16 vol%.

13. In paragraph 1, The above positive electrode active material is included in an amount of 55 to 90 wt% based on the total weight of the positive electrode active material layer, The above sulfide-based solid electrolyte is included in an amount of 10 to 50 wt% based on the total weight of the positive electrode active material layer, A positive electrode for an all-solid-state battery, wherein the above-mentioned conductive material is contained in an amount of 0.05 to 10 wt% based on the total weight of the positive electrode active material layer.

14. An all-solid-state battery comprising the positive electrode, negative electrode and a sulfide-based solid electrolyte layer interposed therebetween.

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