Electrode for energy storage device and energy storage device comprising same

Abstract

The present invention relates to an electrode for an energy storage device and an energy storage device comprising same. More specifically, when manufacturing an electrode for an energy storage device by a dry process, calendering process conditions can be changed to control the degree of fiberization of a binder to improve the porosity, tensile strength, or interfacial resistance of the electrode and thereby improve the energy density of the energy storage device.

Description

Electrode for an energy storage device and an energy storage device including the same

[0001] Cross-citation with related applications

[0002] This application claims the benefit of priority based on Korean Patent Application No. 10-2024-0129544 filed September 25, 2024, and all contents disclosed in the document of said Korean patent application are incorporated into this specification.

[0003] Technology field

[0004] The present invention relates to an electrode for an energy storage device and an energy storage device including the same.

[0005] Various batteries capable of overcoming the current limitations of lithium-ion batteries are being researched in terms of capacity, safety, output, scaling up, and miniaturization.

[0006] Continuous research is being conducted in academia and industry on representative technologies, including metal-air batteries, which have a much larger theoretical capacity compared to lithium-ion batteries; all-solid-state batteries, which pose no risk of explosion in terms of safety; supercapacitors in terms of output; NaS batteries or RFBs (redox flow batteries) in terms of scale; and thin-film batteries in terms of miniaturization.

[0007] Among various next-generation batteries, all-solid-state batteries refer to batteries in which the liquid electrolyte used in conventional lithium-ion batteries is replaced with a solid electrolyte. Since flammable solvents are not used within the battery, there is absolutely no ignition or explosion caused by decomposition reactions of conventional electrolytes, thereby significantly improving safety. Furthermore, among all-solid-state batteries, technological development is continuing for sulfide-based all-solid-state batteries, which can achieve a high energy density of theoretically over 900 Wh / L while having high ionic conductivity of the solid electrolyte. In this context, a sulfide-based all-solid-state battery refers to an all-solid-state battery containing a sulfide-based solid electrolyte.

[0008] 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 cathodes for sulfide-based all-solid-state batteries, small-diameter sulfide-based solid electrolyte particles must be added to the cathode to increase the contact interface between the cathode active material and the sulfide-based solid electrolyte particles, thereby enhancing lithium ion conduction. Furthermore, to improve energy density, physical contact between the cathode active material, sulfide-based solid electrolyte particles, and other components within the cathode must be enhanced, and the porosity after rolling the cathode must be reduced and maintained throughout the charging and discharging cycles.

[0009] Accordingly, a technology has been developed to increase and maintain the contact interface between the cathode active material and sulfide-based solid electrolyte particles by introducing a fibrous binder into the cathode. Fibrous binders can be formed as the binder fiberizes when the cathode is manufactured using a solvent-free dry process. Therefore, to obtain a fibrous binder, a binder that fiberizes easily can be introduced into the dry process; for example, poly(tetrafluoroethylene) (PTFE) is a binder that fiberizes easily.

[0010] However, simply introducing a fibrous binder into the cathode of an all-solid-state battery has limitations in reducing the porosity of the cathode. Therefore, there is a need for the development of technology capable of further reducing the porosity of the all-solid-state battery cathode into which the fibrous binder has been introduced.

[0011] Furthermore, since electrodes incorporating fibrous binders are not limited to electrodes for all-solid-state batteries but can be widely applied to electrodes for energy storage devices, there is an increasing demand for the development of energy storage devices containing electrodes with reduced porosity and fibrous binders.

[0012] [Prior Art Literature]

[0013] (Patent Document 1) U.S. Published Patent No. 2024-0079574

[0014] As a result of conducting multifaceted research to solve the above problem, the inventors confirmed that in an energy storage device comprising a fluorine-containing fibrous binder in an electrode, the porosity and tensile strength of the electrode are controlled according to the degree of fiberization of the fluorine-containing fibrous binder, thereby improving the energy density of the energy storage device.

[0015] Accordingly, the object of the present invention is to provide an electrode for an energy storage device comprising a fluorine-containing fibrous binder with a controlled degree of fibrosis.

[0016] In addition, another objective of the present invention is to provide a method for manufacturing an electrode for an energy storage device comprising a fluorine-containing fibrous binder with a controlled degree of fiberization.

[0017] In addition, another objective of the present invention is to provide an energy storage device comprising an electrode for an energy storage device comprising a fluorine-containing fibrous binder with a controlled degree of fiberization.

[0018] To achieve the above objective, the present invention provides an electrode for an energy storage device having an electrode active material layer comprising an electrode active material, a fluorine-containing fibrous binder, and a conductive material, wherein the relative degree of fibrillation (A) of the electrode calculated by the following formula 1 is 4 to 6:

[0019] <Equation 1>

[0020] A = Content of fluorine element on the surface of the electrode active material layer (F1, wt%) / Content of fluorine element inside the electrode active material layer (F2, wt%).

[0021] In one embodiment of the present invention, the fluorine-containing fibrous binder comprises one or more selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same, thereby providing an electrode for an energy storage device.

[0022] In one embodiment of the present invention, an electrode for an energy storage device is provided, wherein the fluorine-containing fibrous binder is included in an amount of 0.1 to 10 weight% based on the total weight of the electrode active material layer.

[0023] In one embodiment of the present invention, an electrode for an energy storage device is provided, wherein the electrode active material layer further comprises a sulfide-based solid electrolyte.

[0024] In one embodiment of the present invention, the electrode is a positive electrode, and the electrode active material layer is a positive active material layer comprising a positive active material, a fluorine-containing fibrous binder, and a conductive material, thereby providing an electrode for an energy storage device.

[0025] In one embodiment of the present invention, an electrode for an energy storage device is provided, wherein the porosity of the positive active material layer is 11% to 15%.

[0026] In one embodiment of the present invention, an electrode for an energy storage device is provided, wherein the positive active material comprises a surface coating layer.

[0027] In one embodiment of the present invention, an electrode for an energy storage device is provided, wherein the surface coating layer comprises a lithium ion conductive oxide.

[0028] In one embodiment of the present invention, the lithium ion conductive oxide is LiNbO3, Li4Ti5O 12 An electrode for an energy storage device is provided, comprising one or more selected from the group consisting of Li3PO4.

[0029] In one embodiment of the present invention, the electrode is a negative electrode, and the electrode active material layer is a negative electrode active material layer comprising a negative electrode active material, a fluorine-containing fibrous binder, and a conductive material, thereby providing an electrode for an energy storage device.

[0030] In one embodiment of the present invention, the electrode may be a dry electrode. The dry electrode refers to an electrode manufactured by a dry process that does not use a solvent.

[0031]

[0032] The present invention also comprises the step of (S1) mixing an electrode active material, a conductive material, and a fluorine-containing binder;

[0033] (S2) A step of fiberizing a fluorine-containing binder by applying a shear force to the mixture obtained in step (S1) above; and

[0034] (S3) A step of obtaining an electrode active material layer by performing a sheeting and calendering process using the mixture obtained in step (S2); the present invention relates to a method for manufacturing an electrode for an energy storage device.

[0035] In one embodiment of the present invention, a method for manufacturing an electrode for an energy storage device is provided, wherein a sulfide-based solid electrolyte is mixed together in step (S1).

[0036] In one embodiment of the present invention, a method for manufacturing an electrode for an energy storage device is provided, wherein the shear force is applied by an agitate mortar, ball milling, kneader, or roll press.

[0037] In one embodiment of the present invention, a method for manufacturing an electrode for an energy storage device is provided, wherein the calendering process is performed 6 to 10 times.

[0038] In one embodiment of the present invention, a method for manufacturing an electrode for an energy storage device is provided, wherein the calendering process is performed uniaxially or biaxially.

[0039]

[0040] The present invention also provides an energy storage device comprising the electrode.

[0041] In one embodiment of the present invention, the energy storage device comprises an all-solid-state battery.

[0042] According to the electrode for an energy storage device of the present invention, the degree of fiberization of the binder is controlled by a calendering process during the manufacture of the electrode active material layer, thereby controlling the porosity of the electrode, and as a result, the energy density of the energy storage device is improved.

[0043] FIG. 1 is a schematic diagram of an electrode to explain the relative degree of fibrosis of an electrode according to one embodiment of the present invention.

[0044] Hereinafter, the present invention will be described in more detail to aid in understanding the invention.

[0045] Terms and words used in this specification and claims should not be interpreted as being limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept consistent with the technical spirit of the invention, based on the principle that the inventor can appropriately define the concept of the terms to best describe his invention.

[0046] As used in this specification, the term “Energy Storage Device (EDS)” refers to a device capable of storing and converting energy.

[0047] As used in this specification, the term “degree of fibrosis” refers to the extent to which a material has progressed into a fibrous state. Specifically, it means that the greater the aspect ratio as the binder becomes fibrous, the greater the degree of fibrosis.

[0048] The term “relative degree of fibrillation of the electrode” as used in this specification refers to the ratio of the degree of fibrillation of the fluorine-containing binder present on the surface of the electrode active material layer to the degree of fibrillation of the fluorine-containing binder present inside the electrode active material layer. Inside and on the surface of the electrode active material layer, the fluorine-containing binder may exist as a fibrous binder in a fibrillated form, or as a secondary particle formed by the aggregation of multiple primary particles. If fluorine elements are detected inside and on the surface of the electrode active material layer, it means that the binder exists as a secondary particle. That is, the higher the content of the fluorine element, the less the fibrillation of the binder proceeds, meaning that the binder exists more as a secondary particle. Therefore, the degree of fibrillation of the binder can be confirmed by the ratio of the content of fluorine elements detected inside and on the surface of the electrode active material layer.

[0049] Additionally, in this specification, when the electrode is an anode or a cathode, the “relative fiberization of the electrode” may be referred to as the “relative fiberization of the anode” or the “relative fiberization of the cathode,” respectively.

[0050]

[0051] Electrode for energy storage device

[0052] The present invention relates to an electrode for an energy storage device.

[0053] An electrode for an energy storage device according to the present invention comprises an electrode active material layer comprising an electrode active material, a fluorine-containing fibrous binder, and a conductive material, wherein the relative degree of fibrillation (A) of the electrode calculated by the following Formula 1 is 4 to 6:

[0054] <Equation 1>

[0055] A = Content of fluorine element on the surface of the electrode active material layer (F1, wt%) / Content of fluorine element inside the electrode active material layer (F2, wt%).

[0056] The above electrode may be an anode or a cathode. If the electrode is an anode, the anode may include an anode active material layer comprising an anode active material. Additionally, if the electrode is a cathode, the cathode may include a cathode active material layer comprising a cathode active material.

[0057] The electrode active material layer may include a fibrous binder formed by the fiberization of a binder and a binder in the form of non-fibrous secondary particles. The distribution of the fibrous binder and the binder in the form of secondary particles may differ within and on the surface of the electrode active material layer. The distribution of the fibrous binder and the binder in the form of secondary particles can be determined by a dry process utilizing sheeting and calendering processes. Since the physical properties of the electrode containing the fibrous binder and the performance of the energy storage device vary depending on the distribution of the fibrous binder and the binder in the form of secondary particles, these distributions are defined as the relative degree of fiberization (A) of the electrode. Here, the secondary particles refer to particles formed by the aggregation of multiple primary particles, which are single particles.

[0058] It is preferable that the relative degree of fiberization (A) of the electrode be greater in the interior than on the surface of the electrode active material layer, and this corresponds to the case where A > 1. More preferably, if 4 ≤ A ≤ 6 is satisfied, the tensile strength of the electrode can be strengthened while preventing an increase in resistance. Specifically, if the relative degree of fiberization (A) of the electrode is less than 4, it means that the fluorine-containing binder exists more in the form of secondary particles rather than fibers within the electrode active material layer, and there is a large amount of detected internal fluorine elements. This implies that the fiberization of the binder within the electrode has not progressed significantly, which may result in a decrease in the tensile strength of the electrode. Furthermore, if the relative degree of fiberization (A) of the electrode is greater than 6, it means that the fluorine-containing binder exists more in the form of fibers rather than secondary particles within the electrode active material layer, and the fiberization of the binder within the electrode has progressed significantly. While the tensile strength of the electrode may increase, the performance of the energy storage device may be degraded because the resistance component increases due to excessive fiberization. Specifically, the relative degree of fibrosis (A) of the electrode may be 4 or more, 4.1 or more, 4.2 or more, 4.3 or more, 4.4 or more, 4.5 or more, 4.6 or more, 4.7 or more, 4.8 or more, 4.9 or more, or 5 or more, and may be 6 or less, 5.9 or less, 5.8 or less, 5.7 or less, 5.6 or less, 5.5 or less, 5.4 or less, 5.3 or less, 5.2 or less, or 5.1 or less.

[0059] The content of fluorine elements on the surface of the electrode active material layer (F1, wt%) and the content of fluorine elements inside the electrode active material layer (F2, wt%) can be measured by energy-dispersive X-ray spectroscopy (EDS). Specifically, (a) after analyzing the inside and surface of the electrode active material layer by EDS, (b) the content of fluorine elements on the surface of the electrode active material layer (F1, wt%) and the content of fluorine elements inside the electrode active material layer (F2, wt%) can be measured.

[0060]

[0061] FIG. 1 is a schematic diagram of an electrode to explain the relative degree of fibrosis of an electrode according to one embodiment of the present invention.

[0062] Referring to FIG. 1, the first region corresponds to the surface of the electrode active material layer, and the second region may correspond to the interior of the electrode active material layer.

[0063] The interior of the electrode active material layer refers to a portion of the electrode cut from the surface by a certain thickness (D). For example, the certain thickness (D) may refer to a thickness corresponding to 20% to 40% of the total thickness of the electrode. Specifically, the certain thickness (D) may be 20% or more, 21% or more, 22% or more, 23% or more, 24% or more, 25% or more, 26% or more, 27% or more, 28% or more, 29% or more, or 30% or more based on the total thickness of the electrode, and may be 40% or less, 39% or less, 38% or less, 37% or less, 36% or less, 35% or less, 34% or less, 33% or less, 32% or less, or 31% or less.

[0064]

[0065] In one embodiment of the present invention, the electrode active material layer may include a fluorine-containing fibrous binder. The fluorine-containing fibrous binder is formed by applying a shear force to the fluorine-containing binder during electrode manufacturing to cause fiberization, and the fiberization of the fluorine-containing binder is controlled by a calendering process. Generally, the binder may be included to facilitate bonding between materials included in the electrode active material layer or between the electrode active material layer and the electrode current collector. Due to the fibrous morphological characteristics of the binder, bonding between materials included in the electrode active material layer is further promoted, which can further reduce the porosity of the electrode and also strengthen the tensile strength.

[0066] The above fluorine-containing fibrous binder may include one or more selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same. However, the above fluorine-containing fibrous binder material is not limited thereto as long as its physical properties can be easily modified and fiberized by a calendering process.

[0067] In addition, the fluorine-containing fibrous binder may be included in an amount of 0.1 to 10 weight% based on the total weight of the electrode active material layer. If the content of the fluorine-containing fibrous binder is less than 0.1 weight%, the effect of improving the binding force between materials included in the electrode active material layer is negligible, which may result in a decrease in tensile strength, and if it exceeds 10 weight%, the ionic conductivity or electrical conductivity of the electrode may decrease. Specifically, the content of the fibrous binder may be 0.1 weight% or more, 0.5 weight% or more, 1 weight% or more, 2 weight% or more, 3 weight% or more, 4 weight% or more, or 5 weight% or more, and may be 10 weight% or less, 9 weight% or less, 8 weight% or less, 7 weight% or less, or 6 weight% or less.

[0068]

[0069] In one embodiment of the present invention, the electrode active material layer may further include a sulfide-based solid electrolyte.

[0070] The above sulfide-based solid electrolyte may include a compound represented by the following chemical formula 1:

[0071] <Chemical Formula 1>

[0072] Li a M b SX c

[0073] In the above chemical formula 1, M is selected from P, Sn, Sb, As, and Ge;

[0074] X is selected from Cl, Br, and I;

[0075] 5≤a<7.5, 0.5 <b<1.5, 및 0.5<c<2이다.

[0076] In addition, the sulfide-based solid electrolyte may be included in an amount of 10 to 50 weight% based on the total weight of the electrode active material layer. Specifically, the content of the sulfide-based solid electrolyte may be 10 weight% or more, 20 weight% or more, or 30 weight% or more, and may be 50 weight% or less, 45 weight% or less, or 40 weight% or less. If the content of the sulfide-based solid electrolyte is less than 10 weight%, it may not be sufficient to fill the voids formed within the electrode active material layer, making it difficult to reduce the porosity of the electrode active material layer; and if it exceeds 50 weight%, the content of the electrode active material, fluorine-containing fibrous binder, or conductive material included in the electrode active material layer may be relatively reduced, which may degrade the performance of the energy storage device.

[0077]

[0078] In one embodiment of the present invention, the electrode is a positive electrode, and the electrode active material layer may be a positive electrode active material layer comprising a positive electrode active material, a fluorine-containing fibrous binder, and a conductive material. The positive electrode active material layer may further comprise a sulfide-based solid electrolyte as described above.

[0079]

[0080] In one embodiment of the present invention, the positive electrode active material is not particularly limited as long as it is a material capable of reversibly absorbing and releasing lithium ions. For example, the positive electrode active material may be lithium cobalt oxide (LiCoO2), lithium nickel oxide (LiNiO2), Li[Ni x Co y Mn z M v ]O2(wherein M is any one element selected from the group consisting of Al, Ga, and In, or two or more of these; 0.3≤x<1.0, 0≤y, z≤0.5, 0≤v≤0.1, x+y+z+v=1), Li(Lia 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 comprises one or more selected from the group consisting of Mn, Ni, Co, Fe, Cr, V, Cu, Zn, and Ti; M' is one or more selected from the group consisting of Al, Mg, and B, and A is one or more selected from the group consisting of P, F, S, and N.) layered compounds such as 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, etc.; lithium copper oxide (Li2CuO2); vanadium oxides such as LiV3O8, LiFe3O4, V2O5, Cu2V2O7, etc.; chemical formula LiNi 1-y Ni-site type lithium nickel oxide represented by MyO2 (where 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 Examples include lithium manganese complex oxides represented by O2 (where M is Co, Ni, Fe, Cr, Zn, or Ta, and y is 0.01 to 0.1) or Li2Mn3MO8 (where M is Fe, Co, Ni, Cu, or Zn); LiMn2O4 in which part of the Li of the chemical formula is substituted with alkaline earth metal ions; disulfide compounds; Fe2(MoO4)3, but are not limited to these.

[0081] In addition, the positive active material may be included in an amount of 55 to 90 weight% based on the total weight of the positive active material layer. Specifically, the content of the positive active material may be 55 weight%, 60 weight% or more, or 65 weight% or more, and may be 83 weight% or less, 85 weight% or less, or 90 weight% or less. If the content of the positive active material is less than 55 weight%, the performance of the energy storage device may be degraded, and if it exceeds 90 weight%, the mass transfer resistance may increase.

[0082] In addition, the positive electrode active material may include a surface coating layer. The surface coating layer may include a lithium ion conductive oxide. When a surface coating layer including a lithium ion conductive oxide is formed on the surface of the positive electrode active material, direct contact between the positive electrode active material and the sulfide-based solid electrolyte is prevented, thereby preventing the decomposition reaction of the sulfide-based solid electrolyte.

[0083] The above lithium ion conductive oxide is LiNbO3, Li4Ti5O 12 It may include one or more selected from the group consisting of and Li3PO4. In addition, the lithium ion conductive oxide may be amorphous or crystalline. In addition, the method of forming a surface coating layer containing the lithium ion conductive oxide may be spray coating, immersion method, etc., but is not limited thereto, and various methods can be used to form a coating layer on the surface of the positive electrode active material.

[0084]

[0085] In one embodiment of the present invention, the conductive material is not particularly limited as long as it prevents adverse reactions in the internal environment of the energy storage device and has excellent electrical conductivity without causing chemical changes in the energy storage device, and can be used as a representative example, graphite or conductive carbon, for example, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, or thermal black; carbon-based material having a crystal structure of graphene or graphite; conductive fiber such as carbon fiber or metal fiber; fluorinated carbon; metal powder such as aluminum powder or nickel powder; conductive whiskey such as zinc oxide or potassium titanate; conductive oxide such as titanium oxide; and conductive polymer such as polyphenylene derivative; can be used alone or in a mixture of two or more types, but is not necessarily limited thereto. Preferably, the conductive material may include carbon nanofibers (CNF) or vapor-grown carbon fibers (VGCF).

[0086] The conductive material may typically be included in an amount of 0.05% to 10% by weight based on the total weight of the positive active material layer. Specifically, the content of the conductive material may be 0.05% by weight or more, 0.1% by weight or more, 0.5% by weight or more, 1% by weight or more, 1.5% by weight or more, 2% by weight or more, 2.5% by weight or more, 3% by weight or more, 3.5% by weight or more, 4% by weight or more, 4.5% by weight or more, or 5% by weight or more, and may be 10% by weight or less, 9.5% by weight or less, 8% by weight or less, 7.5% by weight or less, 6% by weight or less, 6.5% by weight or less, or 6% by weight or less. If the content of the conductive material is too low, less than 0.05 weight%, it is difficult to expect an improvement in electrical conductivity, or the electrochemical properties of the energy storage device may deteriorate; if it is too high, exceeding 10 weight%, the amount of the positive electrode active material becomes relatively small, which may lead to a decrease in capacity and energy density. The method of including the conductive material in the positive electrode is not significantly limited, and conventional methods known in the field, such as mixing with the positive electrode active material or coating, may be used.

[0087]

[0088] In one embodiment of the present invention, the anode active material layer may have reduced porosity, reduced thickness, improved tensile strength, and reduced interfacial resistance depending on the relative fiberization degree (A) of the anode as described above.

[0089] The porosity of the positive active material layer may be 11% to 15%. If the porosity exceeds 15%, the energy density of the energy storage device may decrease. Specifically, the above porosity may be 11% or more, 11.1% or more, 11.2% or more, 11.3% or more, 11.4% or more, 11.5% or more, 11.6% or more, 11.7% or more, 11.8% or more, 11.9% or more, 12% or more, 12.1% or more, 12.2% or more, 12.3% or more, 12.4% or more, 12.5% ​​or more, 12.6% or more, 12.7% or more, 12.8% or more, 12.9% or more, 13% or more, and 15% or less, 14.9% or less, 14.8% or less, 14.7% or less, 14.6% or less, 14.5% or less, 14.4% or less, 14.3% or less, 14.2% or less, It may be 14.2% or less, 14.1% or less, or 14% or less. The above porosity may refer to the volume (vol%) of the pores relative to the total volume of the positive active material layer. Additionally, if the above positive active material layer itself is used as the positive without using the above positive current collector, the porosity of the above positive active material layer may refer to the porosity of the positive active material layer.

[0090]

[0091] In addition, the thickness of the anode including the anode active material layer after rolling may be 120 μm or less. If the thickness exceeds 120 μm, the energy density of the energy storage device utilizing the anode may decrease. Specifically, the thickness may be 120 μm or less, 115 μm or less, 110 μm or less, 105 μm or less, 100 μm or less, 95 μm or less, 90 μm or less, 85 μm or less, or 80 μm or less. The lower limit of the thickness is not specifically limited, but may be 50 μm or more, 55 μm or more, 60 μm or more, or 65 μm or more.

[0092]

[0093] In addition, the interface resistance may be 60 ohm·cm² or less. If the interface resistance exceeds 60 ohm·cm², the electrical conductivity within the anode may decrease and the charge / discharge performance may be reduced. Specifically, the interface resistance may be 60 ohm·cm² or less, 55 ohm·cm² or less, 50 ohm·cm² or less, 45 ohm·cm² or less, 40 ohm·cm² or less, 35 ohm·cm² or less, or 30 ohm·cm² or less. The lower limit of the interface resistance is not specifically limited, but may be greater than 0 ohm·cm², 5 ohm·cm² or more, or 10 ohm·cm² or more.

[0094]

[0095] In one embodiment of the present invention, the positive current collector supports the positive active material layer and serves to transfer electrons between the external wire and the positive active material layer.

[0096] The above positive current collector is not particularly limited as long as it has high electronic conductivity without causing chemical changes in the energy storage device. For example, stainless steel, aluminum, nickel, titanium, palladium, calcined carbon, stainless steel surface treated with carbon, nickel, silver, etc., and aluminum-cadmium alloy may be used as the above positive current collector.

[0097] The above positive current collector may have a fine irregular structure on its surface or adopt a three-dimensional porous structure to strengthen the bonding force with the positive active material layer. Accordingly, the above positive current collector may include various forms such as a film, sheet, foil, mesh, net, porous body, foam, nonwoven fabric, etc.

[0098]

[0099] In one embodiment of the present invention, the electrode is a negative electrode, and the electrode active material layer may be a negative electrode active material layer comprising a negative electrode active material, a fluorine-containing fibrous binder, and a conductive material. The negative electrode active material layer may further include a sulfide-based solid electrolyte as described above. Additionally, the negative electrode active material layer may be formed on one surface of a negative electrode current collector.

[0100] In addition, in the above-mentioned negative electrode active material layer, the negative electrode active material is lithium (Li + It may include a material capable of reversibly intercalating or deintercalating ), a material capable of reacting with lithium ions to reversibly form a lithium-containing compound, a lithium metal, or a lithium alloy.

[0101] The above lithium ion (Li + A material capable of reversibly inserting or deinserting ) may be, for example, crystalline carbon, amorphous carbon, or a mixture thereof. The lithium ions (Li + A material capable of reversibly forming a lithium-containing compound by reacting with ) may be, for example, tin oxide, titanium nitrate, or silicon. The lithium alloy may be, for example, an alloy of a metal selected from the group consisting of lithium (Li) and 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).

[0102] Preferably, the negative electrode active material may be lithium metal or lithium-indium alloy (Li-In), and specifically, may be in the form of a thin film or a lithium-indium alloy thin film or powder with lithium metal or lithium.

[0103] The above-mentioned negative electrode active material may be included in an amount of 40 to 80 weight% based on the total weight of the negative electrode active material layer. Specifically, the content of the above-mentioned negative electrode active material may be 40 weight% or more, 45 weight% or more, or 50 weight% or more, and may be 80 weight% or less, 75 weight% or less, or 70 weight% or less. If the content of the above-mentioned negative electrode active material is less than 40 weight%, connectivity between materials within the negative electrode active material layer may be insufficient, and if it exceeds 80 weight%, mass transfer resistance may increase.

[0104] In addition, the above-mentioned fluorine-containing fibrous binder is a component that assists in the bonding of the cathode active material and the conductive material, etc., and in the bonding to the cathode current collector, and the fluorine-containing fibrous binder material and content are as described above.

[0105]

[0106] In addition, the conductive material is not particularly limited as long as it prevents adverse reactions in the internal environment of the energy storage device and possesses excellent electrical conductivity without causing chemical changes in the energy storage device. Representative examples include graphite or conductive carbon. For instance, graphite such as natural graphite or artificial graphite; carbon black such as carbon black, acetylene black, Ketjen black, Denka black, thermal black, channel black, furnace black, lamp black, or thermal black; carbon-based materials having a crystal structure of graphene or graphite; conductive fibers such as carbon fibers or metal fibers; fluorocarbon; metal powders such as aluminum powder or nickel powder; conductive whiskies such as zinc oxide or potassium titanate; conductive oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives may be used alone or in a mixture of two or more types, but is not necessarily limited thereto. Preferably, the conductive material may include vapor-grown carbon fiber (VGCF).

[0107] The conductive material may typically be included in an amount of 1% to 5% by weight based on the total weight of the cathode active material layer. Specifically, the content of the conductive material may be 1% or more by weight, 1.5% or more by weight, or 2% or more by weight, and 5% or less by weight, 4.5% or less by weight, or 4% or less by weight. If the content of the conductive material is too low (less than 1% by weight), it is difficult to expect an improvement in electrical conductivity, or the electrochemical properties of the energy storage device may deteriorate. If it is too high (more than 5% by weight), the amount of the cathode active material becomes relatively small, which may lead to a decrease in capacity and energy density. The method of including the conductive material in the cathode is not significantly limited, and conventional methods known in the art, such as mixing with the cathode active material or coating, may be used.

[0108] In addition, the above-mentioned negative current collector is not particularly limited as long as it is conductive without causing chemical changes in the energy storage device. For example, the above-mentioned negative current collector may be copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface treated with carbon, nickel, titanium, silver, etc., or aluminum-cadmium alloy. In addition, the above-mentioned negative current collector may be used in various forms such as a film, sheet, foil, net, porous body, foam, or nonwoven fabric having fine irregularities formed on its surface, just like the positive current collector.

[0109]

[0110] In addition, the porosity, thickness, and tensile strength of the above-mentioned cathode may be the same as the porosity, thickness, and tensile strength of the anode.

[0111]

[0112] In one embodiment of the present invention, the electrode active material layer may be solvent-free. That is, the electrode active material layer may be manufactured by a solvent-free process that does not use a solvent.

[0113] Since the above electrode active material layer does not use a solvent in the manufacturing process, the phenomenon in which the crystal structure of the sulfide-based solid electrolyte is destroyed by the solvent and the ion conductivity decreases can be prevented.

[0114]

[0115] Method for manufacturing an electrode for an energy storage device

[0116] The present invention also relates to a method for manufacturing an electrode for an energy storage device.

[0117] A method for manufacturing an electrode for an energy storage device according to the present invention comprises: (S1) a step of mixing an electrode active material, a conductive material, and a fluorine-containing binder; (S2) a step of applying a shear force to the mixture obtained in step (S1) to fiberize the fluorine-containing binder; and (S3) a step of performing a sheeting and calendering process using the mixture obtained in step (S2) to obtain an electrode active material layer. If the manufactured electrode active material layer is in a free-standing form, it can be used as an electrode such as a positive or negative electrode. However, if the electrode active material layer is not in a free-standing form, the method may further include a step (S4) of attaching the film-shaped electrode active material layer obtained in step (S3) to an electrode current collector to manufacture an electrode for an energy storage device.

[0118]

[0119] The specific materials, physical properties, and content of the positive active material, negative active material, sulfide-based solid electrolyte, conductive material, and fluorine-containing binder used in the method for manufacturing an electrode for an energy storage device according to the present invention are as described above. The fluorine-containing binder refers to the raw material of the fluorine-containing fibrous binder included in the electrode.

[0120]

[0121] In step (S1) of the method for manufacturing an anode for an energy storage device according to the present invention, an electrode active material, a conductive material, and a fluorine-containing binder may be mixed. Additionally, a sulfide-based solid electrolyte may be mixed together.

[0122] The electrode active material, sulfide-based solid electrolyte, conductive material, and fluorine-containing binder used as raw materials are all in powder form, and can be uniformly mixed considering processability and product reliability. The mixing method is not particularly limited as long as it is a method capable of uniformly mixing powder-form materials.

[0123]

[0124] In step (S2) of the method for manufacturing an electrode for an energy storage device according to the present invention, a shear force can be applied to the mixture obtained in step (S1) to fiberize the fluorine-containing binder.

[0125] Due to the shear force described above, the fluorine-containing binder contained in the mixture may be physically deformed and fiberized. As previously mentioned, the fluorine-containing binder used as a raw material may possess physical properties that allow it to be easily physically deformed. Furthermore, to apply a shear force to the mixture, the mixture may be introduced into a mortar, ball mill, kneader, or roll press to perform physical mixing. During physical mixing, the shear force applied to the fluorine-containing binder causes it to frictionally rub against the powder particles within the mixture, thereby physically deforming and fiberizing.

[0126]

[0127] In step (S3) of the method for manufacturing an electrode for an energy storage device according to the present invention, an electrode active material layer can be obtained by performing a sheeting and calendering process using the mixture obtained in step (S2). At this time, the mixture obtained in step (S2) may be used as is, or the mixture may be ground before use.

[0128] The above sheeting process is a step of initially forming a mixture containing a fiberized binder from step (S1) into a membrane shape. Additionally, the above calendering process can further roll the membrane-shaped molded product to control the degree of fiberization of the binder and control the porosity, thickness, or tensile strength of the electrode active material layer. Furthermore, due to the above sheeting and calendering processes, the electrode active material layer can be formed into a membrane shape in which physical properties such as the degree of fiberization, porosity, thickness, or tensile strength of the fluorine-containing binder are controlled.

[0129]

[0130] In one embodiment of the present invention, the calendering process enables control of the porosity, thickness, and tensile strength of the electrode active material layer. The calendering process refers to a process of passing a workpiece between two rollers.

[0131] The above calendering process may be performed 6 to 10 times. In this case, the number of calendering processes may refer to the number of times the workpiece passes between the two rollers. If the number of calendering processes is less than 6 times, the effect of reducing the thickness and porosity of the electrode active material layer and the effect of improving tensile strength may be negligible, and if it exceeds 10 times, processability may be reduced. Specifically, the process may be 6 times or more or 7 times or more, and 10 times or less, 9 times or less, or 8 times or less.

[0132]

[0133] In one embodiment of the present invention, the orientation of the calendering process may be performed uniaxially or biaxially. Herein, uniaxial means that the calendering proceeds in one direction, and biaxial means that after calendering proceeds in one direction, it proceeds alternately in the horizontal plane and the vertical direction of the electrode active material layer.

[0134] When the above calendering process is performed uniaxially, the fiberization of the binder becomes directional. On the other hand, when the above calendering process is performed biaxially, the fiberization of the binder becomes uniformly directional, so the difference in strength according to direction can be reduced.

[0135] When the electrode active material layer manufactured by the above calendering process is in a free-standing form, the electrode active material layer itself can be used as an electrode such as a positive or negative electrode without a separate current collector.

[0136]

[0137] In the method for manufacturing an electrode for an energy storage device according to the present invention, if the electrode active material layer is not in a freestanding form, the method may further include the step of attaching the electrode active material layer in a film form obtained in the step (S3) to an electrode current collector as the step (S4), thereby manufacturing an electrode for an energy storage device.

[0138] The types and physical properties of the above electrode current collectors, namely the positive current collector and the negative current collector, are as described above.

[0139]

[0140] Energy storage devices

[0141] The present invention also relates to an energy storage device comprising the electrode.

[0142] In one embodiment of the present invention, the energy storage device may include the positive electrode, the negative electrode, a separator interposed between them, and an electrolyte. The electrolyte may be a liquid electrolyte. The lithium secondary battery may include a lithium-ion secondary battery, a lithium-sulfur secondary battery, or a lithium-air secondary battery.

[0143] In one embodiment of the present invention, the energy storage device may include the anode, the cathode, and a solid electrolyte membrane interposed between them. The cathode may include a cathode active material layer as described above, or may include an anodeless layer. The solid electrolyte membrane may be a sulfide-based solid electrolyte membrane. The energy storage device may be an all-solid-state battery.

[0144] The above-mentioned non-cathode layer refers to a negative electrode layer in which lithium metal or lithium alloy, which can serve as a lithium source among the negative electrode active materials, is not present in the negative electrode during the initial assembly of the battery, but lithium is precipitated in the negative electrode upon charging. A battery comprising the above-mentioned non-cathode layer can be called a negative electrode-free battery.

[0145] In the above-described negative electrode-free battery, lithium ions emitted from the positive electrode move to the negative electrode to form a negative electrode active material layer during the charging and discharging of the battery. For example, when charging the battery, lithium ions are detached from the positive electrode active material and move toward the negative electrode side to form a lithium metal composed purely of lithium, which may form a lithium metal layer in the form of a layer on the negative electrode current collector, or form a lithium metal structure in any shape other than a layer. Any shape may be, for example, a structure in which lithium metal is aggregated into a particle shape.

[0146]

[0147] In one embodiment of the present invention, the sulfide-based solid electrolyte included in the sulfide-based solid electrolyte membrane may be represented by the following chemical formula 1:

[0148] <Chemical Formula 1>

[0149] Li a M b SX c

[0150] In the above chemical formula 1, M is selected from P, Sn, Sb, As, and Ge;

[0151] X is selected from Cl, Br, and I;

[0152] 5≤a<7.5, 0.5 <b<1.5, 0.5<c<2이다

[0153] However, the above sulfide-based solid electrolytes are not limited to these, and sulfide-based solid electrolytes commonly used in the industry may be widely used.

[0154]

[0155] battery module

[0156] The present invention also relates to a battery module comprising the all-solid-state battery as a unit cell, a battery pack comprising the battery module, and a device comprising the battery pack as a power source.

[0157] Specific examples of the above-mentioned device include, but are not limited to, power tools that are powered by an electric motor; electric vehicles including electric vehicles (EV), hybrid electric vehicles (HEV), plug-in hybrid electric vehicles (PHEV); electric two-wheeled vehicles including electric bicycles (E-bike) and electric scooters (E-scooter); electric golf carts; and power storage systems.

[0158] Preferred embodiments are presented below to aid in understanding the present invention; however, the following embodiments are merely illustrative of the invention, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and spirit of the invention, and that such changes and modifications fall within the scope of the appended claims.

[0159]

[0160] In the following examples and comparative examples, a positive electrode and an all-solid-state battery containing the same were manufactured according to the composition of the positive electrode active material layer and the calendering process conditions as described in Table 1 below.

[0161]

[0162] Calendering Process Frequency Example 16 Comparative Example 10 Comparative Example 23

[0163]

[0164] Example 1

[0165] 1-1. Anode Manufacturing

[0166] LiN as a positive active material 0.8 Co 0.1 Mn 0.1 An anode was prepared as follows using O2 (NCM 811), Li6PS5Cl as a sulfide-based solid electrolyte, VGCF as a conductive material, and polytetrafluoroethylene (PTFE) as a binder.

[0167] Powder mixing was performed using a positive electrode active material, a sulfide-based solid electrolyte, a conductive material, and a binder in a weight ratio of 78:19.5:1.5:1. Specifically, the positive electrode active material and the sulfide-based solid electrolyte were measured in powder form and mixed using a blade mixer in a dry room environment. Subsequently, a measured amount of the conductive material was added and mixed further. Then, a measured amount of the binder was added and mixed further to obtain a mixture.

[0168] The above mixture was fed into a mortar and pestle, and the binder contained in the mixture was fiberized using the mortar. Afterward, the mixture was passed between two rollers to perform sheeting, and then rolled through a calendering process to obtain a film-shaped cathode active material layer. The calendering process was performed six times.

[0169]

[0170] Comparative Example 1

[0171] An anode was manufactured in the same manner as in Example 1, except that a calendering process was not performed after the sheeting process.

[0172]

[0173] Comparative Example 2

[0174] The anode was manufactured in the same manner as in Example 1, except that the calendering process was performed three times after the sheeting process.

[0175]

[0176] Experimental Example 1: Evaluation of Anode Properties

[0177] The physical properties of the anode were evaluated according to the number of calendering processes during the anode manufacturing process.

[0178]

[0179] (1) Relative degree of fibrosis of the two axes

[0180] The relative degree of fibrillation of the anode was calculated using Equation 1 below. Equation 1 below applies when the electrode is the anode. When the relative degree of fibrillation of the anode calculated by Equation 1 below is in the range of 4 to 6, the degree of fibrillation of the binder present inside and on the surface of the anode is controlled to an optimal range, thereby improving the energy density of the all-solid-state battery:

[0181] <Equation 1>

[0182] A = Content of fluorine element on the surface of the electrode active material layer (F1, wt%) / Content of fluorine element inside the electrode active material layer (F2, wt%).

[0183] The content of fluorine elements on the surface of the positive active material layer (F1, wt%) and the content of fluorine elements inside the positive active material layer (F2, wt%) were measured by energy-dispersive X-ray spectroscopy (EDS).

[0184] At this time, the above-mentioned interior refers to a portion cut from the surface with a thickness corresponding to 40% of the total thickness of the positive active material layer. Since the above-mentioned positive active material layer is in a freestanding form, the thickness of the above-mentioned positive active material layer may refer to the thickness of the positive.

[0185]

[0186] (2) Qigong

[0187] The anode porosity was calculated using Equation 2 below.

[0188]

[0189] <Equation 2>

[0190] Anode Porosity (%) = (1 - ([Anode Weight] / [Anode Area * Anode Thickness] / [Anode Density]) * 100)

[0191]

[0192] (3) Tensile strength

[0193] According to ASTM D638 standards, the anode was cut into a dog bone-shaped specimen. The tensile strength of the cut specimen was measured by tensile testing at a speed of 5 mm / min using a Universal Testing Machine (UTM).

[0194]

[0195] (4) Interfacial resistance

[0196] After the anode was punched into a specific size, it was placed in contact with a current collector and packaged, and then subjected to WIP (Warm Isostatic Press). Afterward, the anode laminated with the current collector was obtained from inside the packaging, and the resistance of the anode was measured using an electrode resistance measurement system (Hioki, RM2610), and the interface resistance was observed after separation.

[0197]

[0198] Table 2 below shows the results of measuring the physical properties of the anode according to the number of calendering processes.

[0199]

[0200] Example 1 Comparative Example 1 Comparative Example 2 Relative fiberity of anode 5.5 1.07 3.3 Anode thickness before rolling (㎛) 156 3 12 197 Porosity (%) 36.7 3 2.7 3 4.8 Anode thickness after rolling (㎛) 114 27 0 149 Porosity (%) 14.6 2 2.5 16.1 Tensile strength (Mpa) 0.2 11 0.18 0 0.193 Interfacial resistance (ohm·cm²) 559 362

[0201]

[0202] As shown in Table 2 above, in the case of Example 1, in which an appropriate number of calendering processes were performed, it was found that compared to Comparative Examples 1 and 2, the relative degree of fiberization of the anode increased, the thickness decreased, the porosity decreased, the tensile strength increased, and the resistance decreased.

Claims

1. An electrode for an energy storage device having an electrode active material layer comprising an electrode active material, a fluorine-containing fibrous binder, and a conductive material, wherein An electrode for an energy storage device having a relative degree of fibrillation (A) of the electrode calculated by the following Equation 1 that is 4 to 6: <Equation 1> A = Content of fluorine element on the surface of the electrode active material layer (F1, wt%) / Content of fluorine element inside the electrode active material layer (F2, wt%).

2. In Paragraph 1, An electrode for an energy storage device, wherein the above-mentioned fluorine-containing fibrous binder comprises one or more selected from the group consisting of polytetrafluoroethylene (PTFE) and copolymers containing the same.

3. In Paragraph 1, An electrode for an energy storage device, wherein the fluorine-containing fibrous binder is included in an amount of 0.1 to 10 weight percent based on the total weight of the electrode active material layer.

4. In Paragraph 1, The electrode for an energy storage device, wherein the electrode active material layer further comprises a sulfide-based solid electrolyte.

5. In Paragraph 1, The above electrode is a positive electrode, and The electrode for an energy storage device, wherein the electrode active material layer is a positive active material layer comprising a positive active material, a fluorine-containing fibrous binder, and a conductive material.

6. In Paragraph 5, An electrode for an energy storage device, wherein the porosity of the positive active material layer is 11% to 15%.

7. In Paragraph 5, The above positive active material comprises a surface coating layer, an electrode for an energy storage device.

8. In Paragraph 7, The above surface coating layer comprises a lithium ion conductive oxide, an electrode for an energy storage device.

9. In Paragraph 8, The above lithium ion conductive oxide is LiNbO3, Li4Ti5O 12 An electrode for an energy storage device comprising one or more selected from the group consisting of and Li3PO4.

10. In Paragraph 1, The above electrode is a negative electrode, and The electrode for an energy storage device, wherein the electrode active material layer is a negative electrode active material layer comprising a negative electrode active material, a fluorine-containing fibrous binder, and a conductive material.

11. (S1) A step of mixing an electrode active material, a conductive material, and a fluorine-containing binder; (S2) A step of fiberizing a fluorine-containing binder by applying a shear force to the mixture obtained in step (S1) above; and (S3) A step of obtaining an electrode active material layer by performing a sheeting and calendering process using the mixture obtained in step (S2); a method for manufacturing an electrode for an energy storage device.

12. In Paragraph 11, A method for manufacturing an electrode for an energy storage device, wherein a sulfide-based solid electrolyte is mixed together in the above (S1) step.

13. In Paragraph 11, A method for manufacturing an electrode for an energy storage device, wherein the above shear force is applied by a mortar, ball milling, a kneader, or a roll press.

14. In Paragraph 11, A method for manufacturing an electrode for an energy storage device, wherein the above calendering process is performed 6 to 10 times.

15. An energy storage device comprising the electrode of claim 1.

16. In Paragraph 15, The above energy storage device is an energy storage device comprising an all-solid-state battery.

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