Electrode structure, positive electrode comprising the same, and electrochemical device and method for manufacturing the same

Abstract

An electrode structure, a positive electrode including the electrode structure, and an electrochemical device, and a method of manufacturing the electrode structure. The electrode structure includes: a current collector; and an electrode active material layer on a surface of the current collector, wherein the electrode active material layer includes an electrode active material and an opening penetrating the electrode active material layer; and a conductive layer including a conductive material and an adhesive on an inner surface of the opening, wherein a content of the conductive material and the adhesive is 0.05% to 3% by weight, based on a total weight of the electrode active material layer.

Description

Technical Field

[0001] This disclosure relates to an electrode structure, a positive electrode including the electrode structure, an electrochemical device, and a method for preparing the electrode structure. Background Technology

[0002] Extensive research has been conducted to develop high-energy-density electrodes for electrochemical devices, such as lithium-ion batteries. Sintered electrodes have been investigated as high-energy-density electrodes. Unlike electrodes prepared using electrode active material slurries, sintered electrode active material layers may not include binders, conductive materials, or a combination thereof, and the sintered electrode active material layer can be bonded to a current collector.

[0003] However, when the sintered body is bonded and fixed to the current collector, cracks may occur between the particles of the electrode active material of the lithium secondary battery that includes the sintered body during charging and discharging. This may lead to the generation of resistance and the deterioration of battery performance, such as reduced capacity.

[0004] Therefore, there is a need to develop electrode structures with high energy density that can enhance high-rate and lifetime characteristics, positive electrodes and electrochemical devices including such electrode structures, and methods for preparing such electrode structures. Summary of the Invention

[0005] An electrode structure with high energy density and enhanced high-rate and lifetime characteristics is provided.

[0006] A positive electrode including this electrode structure is provided.

[0007] An electrochemical device including the positive electrode is provided.

[0008] A method for preparing electrode structures is provided.

[0009] Other aspects will be set forth in part in the description which follows, and will be apparent in part from the description, or may be learned by practicing the embodiments presented in this disclosure.

[0010] According to one embodiment, an electrode structure includes:

[0011] Current collector; and

[0012] Electrode active material layer on the surface of the current collector

[0013] The electrode active material layer includes an electrode active material and an opening penetrating the electrode active material layer; and

[0014] The conductive layer includes a conductive material and an adhesive on the inner surface of the opening, and

[0015] The total weight of the electrode active material layer, the content of conductive materials and binders is 0.05-3% by weight.

[0016] According to one embodiment,

[0017] The positive electrode includes the disclosed electrode structure.

[0018] According to one embodiment, an electrochemical device includes:

[0019] The disclosed positive electrode;

[0020] negative electrode; and

[0021] The electrolyte inserted between the positive and negative electrodes.

[0022] According to one embodiment, a method for preparing an electrode structure includes:

[0023] Provide electrode active material compositions;

[0024] The electrode active material composition is coated onto a substrate;

[0025] Heating the electrode active material composition to prepare an electrode active material layer;

[0026] Forming an opening that penetrates the electrode active material layer;

[0027] A conductive adhesive layer composition is coated onto a current collector to form a coated current collector; and

[0028] An electrode active material layer is pressed onto a coated current collector to prepare a press-fit structure, and a conductive layer is formed on the inner surface of the opening. The press-fit structure includes a conductive bonding layer between the current collector and the electrode active material layer; and

[0029] Annealing the press-fit structure to prepare the electrode structure. Attached Figure Description

[0030] The above and other aspects, features and advantages of certain embodiments of the present disclosure will become more apparent from the following description taken in conjunction with the accompanying drawings, in which:

[0031] Figure 1 This is a schematic diagram illustrating one embodiment of the electrode structure;

[0032] Figure 2 This is a flowchart schematically illustrating an embodiment of a method for preparing an electrode structure;

[0033] Figure 3A This is a scanning electron microscope (SEM) image showing the surface of the positive active material layer of the sintered plate of the positive electrode;

[0034] Figure 3BThis is an SEM image showing the inner wall of the hole;

[0035] Figure 3C yes Figure 3B A magnified SEM image of the inner wall of the hole shown.

[0036] Figure 4 The graphs show the surface resistivity (ohm-cm (Ωcm)) of the positive electrodes prepared in Example 1 and Comparative Example 1, respectively.

[0037] Figure 5 The graph shows the relationship between capacity retention (percentage (%)) and cycle number, illustrating the results of charge and discharge tests on the lithium secondary batteries prepared in Example 2 and Comparative Examples 3 and 4.

[0038] Figure 6A SEM images of the positive active material layer of the sintered plate of the positive electrode of the lithium secondary battery prepared in Example 2 and separated after 500 charge and discharge cycles; and

[0039] Figure 6B This is a SEM image of the positive active material layer of the sintered plate of the positive electrode of a lithium secondary battery prepared in Comparative Example 3 and separated after 500 charge and discharge cycles. Detailed Implementation

[0040] The embodiments will now be described in detail, examples of which are shown in the accompanying drawings, wherein the same reference numerals always refer to the same elements. In this respect, the embodiments may take different forms and should not be construed as limited to the description set forth herein. Therefore, the embodiments are described below only with reference to the accompanying drawings to explain various aspects. As used herein, the term “and / or” includes any and all combinations of one or more related listed items. Expressions such as “at least one of…” modify the entire list of elements, not individual elements within the list, when following a list of elements.

[0041] The electrode structure according to embodiments, the positive electrode including the electrode structure, the electrochemical device, and the method for preparing the electrode structure will be described in more detail below with reference to the accompanying drawings. Therefore, it will be apparent to those skilled in the art that the following description of various embodiments of this disclosure is provided for illustrative purposes only and is not intended to limit the purpose of this disclosure as defined by the appended claims and their equivalents.

[0042] Expressions such as “at least one of…” or “one or more”, when following a list of elements, modify the entire list of elements, not individual elements in the list. As used herein, unless otherwise stated, the term “combination” includes a mixture or composition of one component and another component.

[0043] Throughout this specification, the term "comprising" in relation to a component does not exclude other components, but may include additional components unless otherwise stated.

[0044] As used herein, the terms “first,” “second,” etc., are used to distinguish one component from another, without indicating order, quantity, or importance. Expressions used in the singular form, such as “a” or “one,” including those in the plural form, are used unless otherwise stated or have a distinct meaning in the context. Unless otherwise stated, the term “or” means “and / or.”

[0045] As used herein, the terms "one embodiment," "multiple embodiments," etc., indicate that an element described with respect to one embodiment is included in at least one embodiment described herein and may or may not be present in other embodiments. Furthermore, it will be understood that in various embodiments, the described elements may be combined in any suitable manner.

[0046] Unless otherwise specified, the technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains. All patents, patent applications, and other references cited herein are incorporated herein by reference in their entirety. However, in the event of any conflict or inconsistency between the terms used herein and those cited in the references, the terms used herein shall prevail. Although specific embodiments have been described, alternatives, modifications, variations, improvements, and substantial equivalents not currently anticipated may arise in the mind of the applicant or others skilled in the art. Therefore, the appended claims and their possible modifications are intended to cover all such alternatives, modifications, variations, improvements, and substantial equivalents.

[0047] It will be understood that when an element is referred to as being "on" another element, it can be directly on that other element, or there can be an intervening element between them. Conversely, when an element is referred to as being "directly on" another element, there is no intervening element.

[0048] Furthermore, relative terms such as “lower” and “upper” can be used herein to describe the relationship between one element and another, as shown in the accompanying drawings. It will be understood that, in addition to the orientations depicted in the drawings, the relative terms are also intended to cover different orientations of the device. For example, if the device in one of the drawings is flipped, the element described as being “lower” than the other elements would be oriented “upper” than the other elements. Therefore, the exemplary term “lower” can encompass both “lower” and “upper” orientations, depending on the specific orientation of the drawing.

[0049] As used herein, “about” includes the value and means within an acceptable range of deviation from the particular value, as determined by a person skilled in the art taking into account the measurement in question and the errors associated with the measurement of the particular quantity (i.e., limitations of the measurement system). For example, “about” may mean within one or more standard deviations, or within ±30%, 20%, 10%, or 5% of the value.

[0050] Exemplary embodiments are described herein with reference to cross-sectional views, which are schematic diagrams of idealized embodiments. Therefore, variations in the illustrated shapes due to, for example, manufacturing techniques and / or tolerances are to be expected. Consequently, the embodiments described herein should not be construed as limited to the specific shapes of the areas shown herein, but rather include, for example, shape deviations due to manufacturing processes. For example, areas shown or described as flat may generally have rough and / or non-linear characteristics. Furthermore, acute angles shown may be rounded. Therefore, the areas shown in the figures are schematic in nature, and their shapes are not intended to show the precise shapes of the areas, nor are they intended to limit the scope of the claims.

[0051] As used here, the C-rate describes the current that the battery will release in one hour. For example, the C-rate of a battery with a discharge capacity of 1.6 amp-hours would be 1.6 amps.

[0052] When a sintered electrode active material layer, serving as a high-density electrode structure, is bonded and fixed to a current collector, interfacial resistance may arise from cracks formed between the grains of the electrode active material in an electrochemical device including this electrode structure during charging and discharging. Such interfacial resistance can lead to uneven charging and discharging between the grains of the electrode active material. Uneven volume changes occurring between the grains of the electrode active material can result in the loss of the electrode active material, and the performance of the electrochemical device including the sintered electrode active material layer may be impaired, for example, its capacity may be reduced.

[0053] To address these issues, an electrode structure, a positive electrode including the electrode structure, an electrochemical device, and a method for preparing the electrode structure are provided.

[0054] The electrode structure, the positive electrode including the electrode structure, the electrochemical device, and the method for preparing the electrode structure will be described in more detail below.

[0055] Electrode structure

[0056] An electrode structure according to one embodiment includes: a current collector; and an electrode active material layer (e.g., a sintered plate electrode active material layer) located on the surface of the current collector, wherein the electrode active material layer includes an electrode active material and an opening penetrating the sintered plate electrode active material layer, such as a hole, a crack, or a combination thereof; and a conductive layer, such as a conductive thin film layer, including a conductive material and an adhesive on the inner surface of the opening, wherein the content of the conductive material and the adhesive is 0.05%-3% by weight based on the total weight of the electrode active material layer.

[0057] Based on the total weight of the electrode active material layer, the content of conductive material and binder can be greater than or equal to 0.05%, 0.1%, 0.3%, or 0.5% by weight. Based on the total weight of the electrode active material layer, the content of conductive material and binder can be less than or equal to 3%, 2.5%, 2%, 1.5%, or 1% by weight.

[0058] In at least 90% of the electrode active material region not adjacent to the conductive layer, the content of conductive material and binder is at most 0.01% by weight, based on the total weight of the electrode active material layer. In at least 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% of the electrode active material region not adjacent to the conductive layer, the content of conductive material and binder is at most 0.01% by weight, based on the total weight of the electrode active material layer. As used herein, "electrode active material region not adjacent to the conductive layer" refers to the electrode active material region other than the conductive layer. For example, "electrode active material region not adjacent to the conductive layer" refers to the electrode active material region other than the conductive thin film layer coated on the inner surface of the opening.

[0059] The solid content of the electrode active material layer can range from 25% to 98% by volume. As used herein, "solid content of the electrode active material layer" refers to the content of the electrode active material. The solid content of the electrode active material layer can be greater than or equal to 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, or 95% by volume. The solid content of the electrode active material layer can be less than or equal to 98% or 97% by volume.

[0060] The opening can penetrate the electrode active material layer and extend from the surface of the electrode active material layer facing the current collector to the opposite surface. In one aspect, the sintered plate electrode active material layer can have a hole, crack, or a combination thereof that penetrates the sintered plate electrode active material layer perpendicularly from one surface facing the current collector to the other.

[0061] As used herein, the terms "one surface" and "another surface" refer to a surface perpendicular or substantially perpendicular to the thickness direction of the sintered plate electrode active material layer and the opposite surface. Throughout this specification, the cross-sectional shape of a hole is not limited to a circle. For example, the cross-section of a hole can have any of a variety of suitable shapes, such as circular, elliptical, triangular, square, pentagonal, or hexagonal. A crack refers to a gap having substantially uniform spacing. A crack is different from a non-uniform crack formed between the electrode active materials during charging and discharging. Penetration can refer to penetration in one direction. The penetration direction can include a vertical or substantially vertical direction, a diagonal direction, or a combination thereof.

[0062] In other words, the electrode active material layer includes openings (e.g., pores, cracks, or combinations thereof) that penetrate the electrode active material layer. As used herein, "penetrates the electrode active material layer" means that the opening extends from one surface of the electrode active material layer through the electrode active material layer to the opposite surface of the electrode active material layer.

[0063] Figure 1 This is a schematic diagram showing an electrode structure according to one embodiment.

[0064] like Figure 1 As shown, the electrode structure 10 includes a current collector 1 and a sintered plate electrode active material layer 2 located on the surface of the current collector 1. Through the electrode structure 10, the energy density of the electrode can be increased due to the increased loading of electrode active material in the electrode. The sintered plate electrode active material layer 2 has a plurality of holes 3 penetrating from one surface to the opposite surface of the sintered plate electrode active material layer 2. Specifically, the sintered plate electrode active material layer 2 has a plurality of holes 3 that penetrate perpendicularly from one surface facing the current collector 1 to the other surface of the sintered plate electrode active material layer 2. The sintered plate electrode active material layer 2 can provide a lithium secondary battery with excellent rate characteristics. The holes 3 include a conductive thin film layer 4 formed on their inner walls. The conductive thin film layer 4 can prevent current concentration by forming channels through which electrons move smoothly. Furthermore, the conductive thin film layer 4 can prevent the formation of cracks between the grains constituting the electrode active material during charging and discharging by enhancing the connection between grains. Therefore, the electrode structure 10 can have a high energy density and provide an electrochemical device with enhanced high-rate and lifetime characteristics due to the reduced resistance of the electrode.

[0065] The sintered plate electrode active material layer 2 can have a thickness of about 30 micrometers (μm) or greater. For example, the thickness of the sintered plate electrode active material layer 2 can range from about 30 μm to about 200 μm, such as about 31 μm to about 150 μm, about 32 μm to about 125 μm, about 33 μm to about 100 μm, about 34 μm to about 75 μm, or about 35 μm to about 50 μm. When the thickness of the sintered plate electrode active material layer 2 is within the disclosed range, degradation of battery performance (such as battery capacity) may not occur during charging and discharging. Therefore, the disclosed electrode structure can effectively achieve the effect of improving rate characteristics and lifetime characteristics. The sintered plate electrode active material layer 2 may include two or more layers.

[0066] The active material layer 2 of the sintered plate electrode may include a lithium transition metal oxide. The lithium transition metal oxide can be any suitable lithium transition metal oxide. For example, the lithium transition metal oxide can be a composite oxide of lithium and a metal (such as cobalt, manganese, nickel, or a combination thereof). Examples of composite oxides include compounds represented by the following chemical formula: Li a A 1-b B' b D'2 (where 0.90≤a≤1, 0≤b≤0.5); Li a E 1-b B' b O 2-c D' c (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05); LiE 2-b B' b O 4-c D' c (where 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B' c D' α (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Co b B' c O 2-α F' α (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Co b B' c O 2-α F'2 (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni1-b-c Mn b B' c D' α (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Mn b B' c O 2-α F'2 (where 0.90≤a≤1, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b E c G d O2 (where 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li a Ni b Co c Mn d G e O2 (where 0.90≤a≤1, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2 (where 0.90≤a≤1, 0.001≤b≤0.1); Li a CoG b O2 (where 0.90≤a≤1, 0.001≤b≤0.1); Li a MnG b O2 (where 0.90≤a≤1, 0.001≤b≤0.1); Li a Mn2G b O4 (where 0.90≤a≤1, 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3 (where 0≤f≤2); Li (3-f) Fe2(PO4)3 (where 0≤f≤2); and LiFePO4.

[0067] In the above chemical formula, A is Ni, Co, Mn or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D' is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; F' is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; I' is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0068] For example, the lithium transition metal oxide may include LiCoO2, Li(Ni b Co c Mn d )O2 (where 0<b≤0.9, 0<c≤0.5, 0<d≤0.5, b+c+d=1), Li(Ni b Co c Al e )O2 (where 0<b≤0.9, 0<c≤0.5, 0<e≤0.1, b+c+e=1), LiMn2O4 or LiFePO4.

[0069] The compounds listed above may have a coating on their surface. A mixture of the compounds listed above without a coating and the compounds listed above with a coating may be used. The coating may include a compound of a coating element, such as an oxide, hydroxide, oxyhydroxide, oxycarbonate or hydroxycarbonate of the coating element. The compound constituting the coating may be amorphous or crystalline. The coating element contained in the coating may be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr or a combination thereof. Any suitable method may be used for forming the coating (for example, spray coating or dip coating), and when such a compound of a coating element is used, the physical properties of the positive active material should not be adversely affected.

[0070] If necessary, the sintered-plate electrode active material layer 2 can be prepared by further adding a dispersant, a binder, a plasticizer, a solvent and the like thereto and mixing these components. Examples of the dispersant may include toluene, isopropyl alcohol and N-methylpyrrolidone (NMP). Examples of the binder may include polyvinylidene fluoride or polyvinyl butyral. An example of the plasticizer may include di(2-ethylhexyl) phthalate. An example of the solvent may include NMP. However, the embodiment is not limited thereto, and any suitable dispersant, binder, plasticizer, solvent or the like may be used.

[0071] An opening (e.g., a pore or crack) can be a channel that allows lithium ions to migrate. An electrode structure 10 including such an opening can improve high-rate characteristics. When the pores or cracks are arranged vertically (e.g., substantially perpendicular to the surface of the electrode active material layer), the electrochemical device including such pores or cracks can have improved high-rate characteristics.

[0072] The conductive thin film layer 4 can have a thickness of about 0.1 nanometers (nm) to about 10 μm, for example, about 0.5 nm to about 8 μm, about 1 nm to about 6 μm, about 25 nm to about 4 μm, about 50 nm to about 2 μm, or about 100 nm to about 1 μm. When the thickness of the conductive thin film layer 4 is within the disclosed range, current concentration and local overcharging can be prevented during charging and discharging, thus improving the high-rate and lifetime characteristics of the electrochemical device.

[0073] The conductive thin film layer 4 may include conductive materials and adhesives.

[0074] Conductive materials may include carbonaceous materials, metallic materials, metal oxide materials, or combinations thereof.

[0075] For example, conductive materials may include carbon particles, carbon fibers or carbon tubes, such as carbon black, natural graphite, artificial graphite, acetylene black or Ketjen black; metal particles, metal fibers, metal tubes, metal oxide particles, metal oxide fibers or metal oxide tubes of copper, nickel, aluminum, cobalt, chromium, palladium, molybdenum, silver, gold, thallium, tungsten, iron, titanium, platinum, their oxides or combinations thereof; or combinations thereof.

[0076] For example, the adhesive may include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), polyamide-imide, styrene-butadiene, or combinations thereof.

[0077] The mixing ratio of the conductive material and the adhesive can be within a range suitable for uniformly coating the conductive thin film layer 4. For example, the mixing ratio of the conductive material and the adhesive can be from about 4:9 to about 11:3, such as about 4:8 to about 10:3, about 4:7 to about 9:3, or about 4:6 to about 8:3.

[0078] The current collector 1 can have a thickness of about 3 μm to about 500 μm, for example, about 4 μm to about 200 μm, about 5 μm to about 100 μm, about 6 μm to about 50 μm, about 7 μm to about 25 μm, or about 8 μm to about 20 μm. The current collector 1 should not cause chemical changes in the manufactured electrochemical device and should be conductive. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or stainless steel surface-treated with carbon, nickel, titanium, silver, or aluminum-cadmium alloys can be used. Furthermore, the current collector 1 can be processed to have irregularities on its surface to enhance its adhesion to the electrode active material layer and can be used in any of a variety of suitable forms, including films, sheets, foils, meshes, porous structures, foams, and nonwoven fabrics.

[0079] A conductive bonding layer may also be included between the current collector 1 and the sintered plate electrode active material layer 2. The conductive bonding layer may have a thickness of about 0.1 nm to about 20 μm, for example, about 0.2 nm to about 19 μm, about 0.4 nm to about 18 μm, about 0.6 nm to about 17 μm, about 0.8 nm to about 16 μm, or about 1 nm to about 15 μm. The conductive bonding layer may include a conductive (e.g., conductive) material and an adhesive. When the conductive bonding layer is present between the current collector 1 and the sintered plate electrode active material layer 2, grain-to-grain cracking caused by repeated charge and discharge cycles can be prevented compared to the case where no conductive bonding layer is present.

[0080] The conductive bonding layer may have the same or different composition as the conductive thin film layer 4. For example, the conductive bonding layer may have the same composition as the conductive thin film layer 4.

[0081] Positive electrode and electrochemical device

[0082] The positive electrode according to one embodiment may include the disclosed electrode structure.

[0083] An electrochemical device according to one embodiment may include: a disclosed positive electrode; a negative electrode; and an electrolyte between the positive and negative electrodes. The electrochemical device may include a lithium battery, a capacitor, a supercapacitor, etc. For example, the electrochemical device may be a lithium battery. Examples of lithium batteries may include lithium-ion batteries, all-solid-state lithium batteries, lithium-air batteries, lithium metal batteries, etc. Examples of lithium batteries may include primary batteries or secondary batteries. For example, a lithium battery may be a lithium secondary battery.

[0084] Positive electrodes and electrochemical devices can have high energy density and enhanced high-rate and lifetime characteristics.

[0085] The electrolyte can fill the pores or cracks in the active material layer of the sintered plate electrode of the positive electrode. The electrolyte can fill all or part of the pores or cracks in the active material layer of the sintered plate electrode of the positive electrode.

[0086] Electrolytes can include liquid electrolytes, solid electrolytes, or gel electrolytes.

[0087] Liquid electrolytes consist of lithium salts and organic solvents. Lithium salts are materials soluble in organic solvents and serve as the source of lithium ions in the battery, enabling the basic operation of lithium secondary batteries. Any suitable lithium salt can be used. For example, lithium salts can be LiPF6, LiBF4, LiSbF6, LiAsF6, LiCF3SO3, Li(CF3SO2)3C, Li(CF3SO2)2N, LiC4F9SO3, LiClO4, LiAlO4, LiAlCl4, LiAlF4, LiBPh4, LiB 10 Cl 10 C4F3SO3Li, LiN(C x F 2x+1 SO2)(C x F 2y+1 The following lithium salts can be used as supporting electrolyte salts: SO2 (where x and y are positive integers), CF3CO2Li, LiCl, LiBr, LiI, lithium bis(oxalate)borate (LiBOB), lower aliphatic carboxylic acids, lithium tetraphenylborate, lithium imide, or combinations thereof. The concentration of the lithium salt can be within a suitable range, and the amount of lithium salt in the electrolyte can range, for example, from 0.1 mol / L (molar concentration (M)) to 2.0 M, to obtain the desired performance of the lithium secondary battery. When the concentration of the lithium salt is within the disclosed range, the electrolyte can have appropriate conductivity and viscosity to enhance the performance of the electrolyte and improve the mobility of lithium ions. The electrolyte may also include other additives to further enhance cycle characteristics by forming a stable solid electrolyte interface (SEI) or coating on the surface of the electrode. The additives may be, for example, tris(trimethylsilyl)phosphate (TMSPa), lithium difluorooxaloylborate (LiFOB), vinylene carbonate (VC), propanesulfonyl lactone (PS), succinate (SN), LiBF4, silane compounds having functional groups capable of forming siloxane bonds (such as acryloyl, amino, epoxy, methoxy, ethoxy, or vinyl), and silazane compounds (such as hexamethyldisilazane). These additives may be added individually or in combination of at least two of them. Based on the total weight of the organic solvent, the additives may be included in an amount from about 0.01 wt% to about 10 wt%. For example, based on the total weight of the organic solvent, the additives may be included in an amount from about 0.05 wt% to about 10 wt%, from about 0.1 wt% to about 5 wt%, or from about 0.5 wt% to about 4 wt%. However, the amount of the additives is not particularly limited; the additives should not significantly reduce the effect of improving the capacity retention of the lithium secondary battery by using the electrolyte.

[0088] The solid electrolyte may be an organic solid electrolyte or an inorganic solid electrolyte. Examples of the organic solid electrolyte may include polyethylene derivatives, polyethylene oxide derivatives, polypropylene oxide derivatives, phosphate ester polymers, polylysine, polyester sulfide, polyvinyl alcohol, polyvinylidene fluoride, and polymers containing ionic dissociation groups. Examples of the inorganic solid electrolyte may include nitrides, halides or sulfates of Li, such as Li3N, LiI, Li5NI2, Li3N-LiI-LiOH, LiSiO4, LiSiO4-LiI-LiOH, Li2SiS3, Li4SiO4, Li4SiO4-LiI-LiOH or Li3PO4-Li2S-SiS2.

[0089] The gel electrolyte may include a polymer electrolyte and a lithium salt. If required, the gel electrolyte may further include an ionic liquid or an additive. The polymer electrolyte may include a lithium ion conductive compound. The lithium salt may be any one of the disclosed lithium salts.

[0090] The negative electrode may include a carbonaceous material, a transition metal oxide, a non-transition metal oxide, lithium metal, a metal alloyable with lithium, or a combination thereof. The carbonaceous material may be crystalline carbon, amorphous carbon or a combination thereof. The crystalline carbon may be graphite, such as natural graphite or artificial graphite, which is in amorphous, sheet, spherical or fibrous form; and the amorphous carbon may be soft carbon (low-temperature sintered carbon), hard carbon, mesophase pitch carbide, sintered coke, etc. Examples of the transition metal oxide may include lithium titanium oxide, vanadium oxide and lithium vanadium oxide. Examples of the non-transition metal oxide may include SnO2 and SiO x (where 0<x<2). Examples of the metal alloyable with lithium may include Si, Sn, Al, Ge, Pb, Bi, Sb, Si-Y' alloy (where Y' is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, excluding Si), Sn-Y' alloy (where Y' is an alkali metal, an alkaline earth metal, a Group 13 element, a Group 14 element, a transition metal, a rare earth element, or a combination thereof, excluding Sn). Element Y' may be Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ti, Ge, P, As, Sb, Bi, S, Se, Te, Po, or a combination thereof.

[0091] The negative electrode can be prepared as follows. For example, a negative active material, a binder, a solvent, and (optionally) a conductive material are mixed to prepare a negative electrode slurry composition, and the negative electrode slurry composition is directly coated onto a negative current collector to prepare a negative electrode plate. Alternatively, the negative electrode slurry composition can be cast onto a separate support, and a negative active material film separated from the support can be laminated onto the negative current collector to prepare a negative electrode plate.

[0092] The negative current collector can have a thickness of about 3 μm to about 500 μm, for example, about 3.5 μm to about 250 μm, about 4 μm to about 125 μm, about 4.5 μm to about 100 μm, about 5 μm to about 75 μm, or about 5.5 μm to about 50 μm. There are no particular limitations on the negative current collector; it should not cause a chemical change in the manufactured electrochemical device and should be conductive. For example, copper, stainless steel, aluminum, nickel, titanium, calcined carbon, or stainless steel surface-treated with carbon, nickel, titanium, silver, or aluminum-cadmium alloys can be used. Furthermore, the current collector can be processed to have irregularities on its surface to enhance its adhesion to the negatively active material layer and can be used in any of a variety of suitable forms, including films, sheets, foils, meshes, porous structures, foams, and nonwoven fabrics.

[0093] The electrochemical device may also include a separator. The positive electrode can be separated from the negative electrode by the separator, which can be formed of any suitable material. For example, any suitable separator that has low resistance to ion migration of the electrolyte and excellent electrolyte retention capacity can be used. For example, the separator may comprise glass fiber, polyester, polyethylene, polypropylene, polytetrafluoroethylene (PTFE), or combinations thereof, each of which is a nonwoven or woven fabric. The separator may have a pore size of about 0.01 μm to about 10 μm and a thickness of about 5 μm to about 300 μm.

[0094] For example, a lithium secondary battery can be fabricated by winding or folding a structure including a positive electrode, a separator, and a negative electrode, and housing this structure within a battery case. An organic electrolyte is then injected into the battery case, and the case is sealed with a sealing member, thus completing the manufacture of the lithium secondary battery. The battery case can be cylindrical, rectangular, or thin-film shaped. For example, a lithium secondary battery can be a large-size thin-film battery. A lithium secondary battery can be, for example, a lithium-ion battery.

[0095] A separator can be placed between the positive and negative electrodes to fabricate a battery assembly. The battery assembly can be stacked into a dual-cell structure, impregnated with an organic electrolyte, and then the result is contained in a bag and sealed to complete the fabrication of a lithium-ion polymer battery.

[0096] Furthermore, multiple battery modules can be stacked to form a battery pack, which can be used in any suitable high-capacity and high-output device where high capacity and high output are desired. For example, the battery pack can be used in laptops, smartphones, power tools, electric vehicles, etc.

[0097] The operating voltage of electrochemical devices (such as lithium secondary batteries) can be about 4.0 volts (V) or greater, such as about 4.05V to about 20V, about 4.1V to about 19V, about 4.15V to about 18V, about 4.2V to about 17V, or about 4.25V to about 16V.

[0098] Methods for preparing electrode structures

[0099] A method for preparing an electrode structure according to one embodiment includes: providing an electrode active material composition; coating the electrode active material composition onto a substrate; heating the electrode active material composition to prepare an electrode active material layer; forming an opening, such as a hole or crack, penetrating the electrode active material layer (e.g., a sintered plate electrode active material layer); coating a conductive bonding layer composition onto a current collector to form a coated current collector; pressing the sintered plate electrode active material layer onto the coated current collector to prepare a press-fit structure and forming a conductive layer on the inner surface of the opening, the press-fit structure including a conductive bonding layer between the current collector and the electrode active material layer; and annealing the press-fit structure to prepare the electrode structure.

[0100] In at least 90% of the electrode active material region not adjacent to the conductive layer, the content of conductive material and binder is at most 0.01% by weight, based on the total weight of the electrode active material layer. In at least 91%, 92%, 93%, 94%, 95%, 96%, 97%, 98%, 99%, or 99.9% of the electrode active material region not adjacent to the conductive layer, the content of conductive material and binder is at most 0.01% by weight, based on the total weight of the electrode active material layer.

[0101] The solid content of the electrode active material layer can range from 25% to 98% by volume. As used herein, "solid content of the electrode active material layer" refers to the content of the electrode active material. The solid content of the electrode active material layer can be greater than or equal to 25%, 30%, 35%, 40%, 45%, 50%, 55%, 60%, 65%, 70%, 75%, 80%, 85%, 90%, 92%, or 95% by volume. The solid content of the electrode active material layer can be less than or equal to 98% or 97% by volume.

[0102] According to the method for preparing the electrode structure, an electrode structure with high energy density and enhanced high rate and lifetime characteristics can be provided.

[0103] Figure 2is a schematic flow chart illustrating a method for preparing an electrode structure according to an embodiment.

[0104] As Figure 2 shows, the method for preparing an electrode structure is as follows.

[0105] An electrode active material composition is coated on a substrate, and the coated composition is heated to prepare a sintered plate electrode active material layer 12 (step 1). As the substrate, an organic polymer plate such as polyethylene terephthalate or a conveyor belt can be used. The electrode active material composition may include a powder of lithium transition metal oxide. The electrode active material composition may be a slurry prepared by mixing an electrode active material with a dispersant, a binder, a plasticizer, a solvent, and the like. Examples of the lithium transition metal oxide may include LiCoO2, Li(Ni b Co c Mn d )O2 (where 0<b≤0.9, 0<c≤0.5, 0<d≤0.5, b+c+d=1), Li(Ni b Co c Al e )O2 (where 0<b≤0.9, 0<c≤0.5, 0<e≤0.1, b+c+e=1), LiMn2O4 or LiFePO4. Examples of the dispersant may include toluene, isopropyl alcohol or NMP. Examples of the binder may include polyvinylidene fluoride and polyvinyl butyral. Examples of the plasticizer may include bis(2-ethylhexyl) phthalate. Examples of the solvent may include NMP. However, the embodiment is not limited thereto, and any suitable lithium transition metal oxide, dispersant, binder, plasticizer and solvent may be used. The electrode active material composition may be coated by knife coating, casting, etc. The sintered plate electrode active material layer 12 is prepared by coating the electrode active material composition having a viscosity of about 400 centipoise (cP) to about 5000 cP on a substrate and heating the coated composition in a furnace at a temperature of about 700°C to about 1500°C (for example, about 750°C to about 1450°C, about 800°C to about 1400°C, about 850°C to about 1350°C, about 900°C to about 1300°C, or about 950°C to about 1250°C) for about 1 hour to about 20 hours (for example, about 65 minutes to about 18 hours, about 70 minutes to about 16 hours, about 75 minutes to about 14 hours, about 80 minutes to about 12 hours, or about 85 minutes to about 10 hours). Before heating, the coated electrode active material composition may be subjected to a deformation process under reduced pressure.

[0106] At least one hole 13 or crack penetrating the sintered plate electrode active material layer 12 from one surface to another can be formed (step 2). The penetrating hole 13 or crack can be formed by laser drilling. The hole 13 or crack can be formed to penetrate the sintered plate electrode active material layer 12 perpendicularly from one surface to another. The area of ​​the penetrating hole 13 or crack can be from about 1% to about 10% of the total area of ​​the sintered plate electrode active material layer 12. The size of the hole 13 or crack can be from about 0.1 nm to about 200 μm, for example, from about 0.2 μm to about 150 μm, from about 0.5 μm to about 125 μm, from about 1 μm to about 100 μm, from about 5 μm to about 75 μm, or from about 10 μm to about 50 μm. The size of hole 13 or crack can have different meanings depending on the shape of the particle's cross-section. For example, it can be the "diameter" for a "circular" cross-section, the "length of the principal axis" for an "elliptical" cross-section, the "length of the longest side" for a "rectangular" cross-section, and the "length of one side" for a "pentagonal, hexagonal, etc." cross-section.

[0107] The composition forming the conductive bonding layer can be coated onto the current collector 11. The current collector 11 can have a thickness of about 3 μm to about 500 μm, for example, about 4 μm to about 200 μm, about 5 μm to about 100 μm, about 6 μm to about 50 μm, about 7 μm to about 25 μm, or about 8 μm to about 20 μm. Examples of the current collector 11 may include copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper, or stainless steel surface-treated with carbon, nickel, titanium, silver, or an aluminum-cadmium alloy. The conductive bonding layer 14 can be formed from a composition comprising a conductive material and a binder. The weight ratio of the conductive material to the binder can be in the range of about 4:9 to about 11:3, for example, about 4:8 to about 10:3, about 4:7 to about 9:3, or about 4:6 to about 8:3. When the weight ratio of the conductive material to the binder is within the disclosed range, the conductive bonding layer 14 can be uniformly coated. The conductive material may include carbonaceous materials, metallic materials, metal oxide materials, or combinations thereof. Examples of conductive materials may include carbon particles, carbon fibers, or carbon nanotubes, such as carbon black, natural graphite, artificial graphite, acetylene black, or Ketjen black; metal particles, metal fibers, metal tubes, metal oxide particles, metal oxide fibers, or metal oxide tubes of copper, nickel, aluminum, cobalt, chromium, palladium, molybdenum, silver, gold, thallium, tungsten, iron, titanium, platinum, their oxides, or combinations thereof; or combinations thereof. Examples of adhesives may include vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene (PTFE), polyamide-imide, styrene-butadiene, or combinations thereof. The conductive bonding layer 14 may have a thickness of about 0.1 nm to about 20 μm, for example, about 0.2 nm to about 19 μm, about 0.4 nm to about 18 μm, about 0.6 nm to about 17 μm, about 0.8 nm to about 16 μm, or about 1 nm to about 15 μm.

[0108] The sintered plate electrode active material layer 12 is pressed onto a current collector 11 coated with a composition forming a conductive bonding layer (step 3). During the pressing, pressure is applied using a press. The composition forming the conductive bonding layer is extruded to rise along the inner wall of the holes 13 or cracks in the sintered plate electrode active material layer 12, thereby forming a conductive thin film layer 15 with the composition forming the conductive bonding layer. The conductive thin film layer 15 may have a thickness of about 0.1 nm to about 10 μm, for example, about 0.5 nm to about 8 μm, about 1 nm to about 6 μm, about 25 nm to about 4 μm, about 50 nm to about 2 μm, or about 100 nm to about 1 μm. The conductive thin film layer 15 may also be formed from the disclosed composition for forming the conductive bonding layer.

[0109] Clean the active material layer 12 of the sintered plate electrode to remove any residue present on its surface (step 4). The residue can be removed by wiping with a cleaning solution.

[0110] The press-fitted current collector 11 and the sintered plate electrode active material layer 12 are annealed to prepare the disclosed electrode structure, wherein a conductive bonding layer 14 is between the current collector 11 and the sintered plate electrode active material layer 12 and a conductive thin film layer 15 is formed on the inner surface of the hole 13 or crack (step 5). Annealing can be performed in a vacuum oven at a temperature of about 60°C to about 200°C (e.g., about 70°C to about 190°C, about 80°C to about 180°C, about 90°C to about 170°C, about 100°C to about 160°C, about 110°C to about 150°C) for about 40 minutes to about 200 minutes (e.g., about 50 minutes to about 190 minutes, about 60 minutes to about 180 minutes, about 70 minutes to about 170 minutes, about 80 minutes to about 160 minutes, or about 90 minutes to about 150 minutes).

[0111] The present disclosure will be described in more detail below with reference to the following examples and comparative examples. However, the following examples are presented only as illustrations of the invention, and the scope of the invention is not limited thereto.

[0112] Example

[0113] Preparation of positive electrode

[0114] Example 1: Preparation of the positive electrode

[0115] A sintered plate positive active material layer with a thickness of about 45 micrometers (μm) was prepared by coating a slurry made of LiCoO2 powder, polyvinyl butyral, di(2-ethylhexyl) phthalate and toluene in a weight ratio of 53:6:1:40 onto a conveyor belt and annealing it in a furnace at about 1025°C for 2 hours.

[0116] Multiple holes with a diameter of approximately 30 μm are formed by laser drilling to vertically penetrate the upper and lower surfaces of the positive active material layer of the sintered plate.

[0117] Separately, a composition forming a conductive bonding layer is coated by rod coating on both surfaces of an Al foil current collector having a thickness of 15 μm. This composition is prepared by mixing carbon black (Super-P, TIMCAL) as a conductive material and polyamide-imide as a binder in a weight ratio of 7:3.

[0118] A conductive thin film layer is formed by pressing two sintered plate active material layers onto the two surfaces of an Al foil current collector coated with a composition forming a conductive bonding layer, thereby causing the composition forming the conductive bonding layer to rise along the inner wall of the holes or cracks in the sintered plate active material layers.

[0119] Then, residues on the surface of the positive active material layer of the sintered plate were wiped off using a cleaning wiper, and the structure was annealed in a vacuum furnace at 130°C for 2 hours to prepare the positive electrode. In this case, the thickness of the conductive bonding layer is about 10 μm, and the thickness of the conductive thin film layer is about 500 nanometers (nm).

[0120] Comparative Example 1: Preparation of the positive electrode

[0121] A sintered plate positive active material layer with a thickness of about 45 μm was prepared by coating a slurry made by mixing LiCoO2 powder, polyvinyl butyral, di(2-ethylhexyl) phthalate and toluene in a weight ratio of 53:6:1:40 onto a conveyor belt and annealing it in a heating furnace at about 1025 °C for 2 hours.

[0122] Two sintered plate active material layers were placed on the two surfaces of an Al foil current collector with a thickness of 15 μm to prepare a positive electrode.

[0123] Comparative Example 2: Preparation of the positive electrode

[0124] A sintered plate positive active material layer with a thickness of about 45 μm was prepared by coating a slurry made by mixing LiCoO2 powder, polyvinyl butyral, di(2-ethylhexyl) phthalate and toluene in a weight ratio of 53:6:1:40 onto a conveyor belt and annealing it in a heating furnace at about 1025 °C for 2 hours.

[0125] Separately, a composition for forming a conductive bonding layer, prepared by mixing carbon black (Super-P, TIMCAL) as a conductive material and polyamide-imide as a binder in a weight ratio of 7:3, was coated onto the two surfaces of an Al foil current collector having a thickness of 15 μm by rod coating, and dried at 80°C for 30 minutes to form a conductive bonding layer having a thickness of about 10 μm.

[0126] Two active material layers of two sintered plates were positioned on the two surfaces of an Al foil current collector on which a conductive bonding layer was formed, and dried in a vacuum furnace at 110°C for 2 hours to prepare the positive electrode.

[0127] Preparation of lithium secondary batteries

[0128] Example 2: Preparation of a lithium secondary battery (complete battery cell)

[0129] A mixture of 97 wt% graphite powder (MC20, purity 99.9% or higher, Mitsubishi Chemical), 1.5 wt% styrene-butadiene rubber (SBR) as a binder, and 1.5 wt% carboxymethyl cellulose (CMC) was prepared as the negative active material. N-methyl-2-pyrrolidone solvent was added to the mixture until its solids content reached 70%, and then the mixture was stirred for 60 minutes using a mechanical stirrer to prepare the negative active material composition. The negative active material composition was coated onto both surfaces of a Cu foil current collector with a thickness of 10 μm using a three-roll coater and dried in a hot air dryer at 100°C for 0.5 hours, followed by further drying in a vacuum at 120°C for 4 hours. The resulting material was rolled to prepare a negative electrode comprising a layer of negative active material formed on the current collector.

[0130] A lithium secondary battery (complete battery cell) was prepared using the positive electrode, negative electrode, polyethylene as a separator, and electrolyte prepared in Example 1. The electrolyte was prepared by dissolving 2.0 mol / L (molar concentration (M)) LiPF6 as a lithium salt in a mixed solvent of ethylene carbonate (EC), ethyl methyl carbonate (EMC), dimethyl carbonate (DMC), and fluoroethylene carbonate (FEC) in a volume ratio of 10:5:80:5.

[0131] Comparative Examples 3 and 4: Preparation of Lithium Secondary Batteries (Complete Battery Cells)

[0132] The lithium secondary battery (complete battery cell) was prepared in the same manner as in Example 2, except that the positive electrode prepared in Comparative Examples 1 and 2 was used instead of the positive electrode prepared in Example 1.

[0133] Analysis Example 1: Scanning Electron Microscopy (SEM) Analysis

[0134] SEM analysis was performed on the surface of the positive active material layer and the inner walls of the pores in the sintered plate of the positive electrode prepared in Example 1. The SEM analysis was performed using a JEOL JSM-7600F. The results are shown in [images / details]. Figure 3A , Figure 3B and Figure 3C As shown in the image.

[0135] Reference Figure 3A , Figure 3B and Figure 3C It was confirmed that multiple pores were formed in the active material layer of the sintered plate of the positive electrode prepared in Example 1, and a conductive thin film layer with a thickness of about 500 nm was formed on the inner wall of the pores.

[0136] Evaluation Example 1: Resistivity Test

[0137] Four (4) probe tips were linearly arranged at 1 mm intervals on the surface of the positive electrodes prepared in Example 1 and Comparative Example 1, respectively. A current of 100 mA was supplied to the outer probe tip, and the resistance (voltage / current) was obtained based on the measured potential difference between the inner and outer probe tips. The obtained resistance was multiplied by the thickness (45 μm) of the positive active material layer of the sintered plate and a correction factor to obtain the resistivity value. The results are shown in Figure 4 As shown in Table 1.

[0138] Table 1

[0139] Example 1 0.6 Comparative Example 1 1.7

[0140] Reference Figure 4 As shown in Table 1, the resistivity of the positive electrode prepared in Example 1 is lower than that of the positive electrode prepared in Comparative Example 1. Based on this, it can be confirmed that the positive electrode prepared in Example 1 has a higher conductivity than the positive electrode prepared in Comparative Example 1, thereby resulting in lower resistance. Furthermore, it can be confirmed that the lithium secondary battery including the positive electrode prepared in Example 1 has better output characteristics than the lithium secondary battery including the positive electrode prepared in Comparative Example 1.

[0141] Evaluation Example 2: Charge and Discharge Tests and SEM

[0142] Each of the lithium secondary batteries prepared in Example 2 and Comparative Examples 3 and 4 was charged at a constant current at a rate of 0.1C at room temperature until the voltage reached 4.3 volts (V) (vs. Li / Li). + Then discharge at a constant current at a rate of 0.1C until the voltage reaches the cutoff voltage of 3.0V (vs. Li / Li). + (Molding operation).

[0143] Each lithium-ion battery undergoing the molding process is charged at a constant current at a rate of 0.1C at room temperature until the voltage reaches 4.3V (vs. Li / Li). + Then discharge at a constant current at a rate of 0.1C until the voltage reaches 3.0V (vs. Li / Li). + ).

[0144] Subsequently, the lithium secondary battery was charged with a constant current at a rate of 0.5C until the voltage reached 4.3V (vs. Li / Li). + Then discharge at a constant current at a rate of 0.5C until the voltage reaches 3.0V (vs. Li / Li). + ).

[0145] Subsequently, the lithium secondary battery was charged with a constant current at a rate of 1.0C until the voltage reached 4.3V (vs. Li / Li). +Then discharge at a constant current at a rate of 1.0C until the voltage reaches 3.0V (vs. Li / Li). + This process was repeated 500 times. Capacity retention was calculated using Equation 1 based on discharge capacity relative to cycle number, and some results were obtained in... Figure 5 As shown in Table 2.

[0146] Equation 1

[0147] Capacity retention (%) = (Discharge capacity at 500th cycle / Discharge capacity at 4th cycle) × 100%

[0148] Table 2

[0149] Example 2 88.5 Comparative Example 3 - Comparative Example 4 82.1

[0150] Reference Figure 5 As shown in Table 2, the lithium secondary battery prepared in Example 2 exhibits a higher capacity retention rate than the lithium secondary battery prepared in Comparative Example 4. The lithium secondary battery prepared in Comparative Example 3 failed to reach 50 cycles.

[0151] After 500 charge-discharge cycles, the lithium-ion batteries prepared in Example 2 and Comparative Example 3 were disassembled, and the sintered plate active material layer of each positive electrode was analyzed by SEM. SEM analysis was performed using a JEOL JSM-7600F. Results are shown in [Table data missing]. Figure 6A and Figure 6B As shown in the image.

[0152] Reference Figure 6A After disassembling the lithium secondary battery prepared in Example 2, no cracks were observed between the grains of the positive active material layer in the sintered plate of the positive electrode. (Refer to...) Figure 6B After disassembling the lithium secondary battery prepared in Comparative Example 3, numerous cracks were observed between the grains of the positive active material layer in the sintered plate of the positive electrode.

[0153] The electrode structure according to the embodiment has a high volume fraction of electrode active material layer by including a sintered plate electrode active material layer located on at least one surface of the current collector. Electrochemical devices comprising such an electrode structure have high energy density.

[0154] Furthermore, the active material layer of the sintered plate electrode has at least one pore, crack, or combination thereof penetrating from one surface to another, and includes a conductive thin film layer formed on the inner wall of the pore or crack. Electrochemical devices incorporating such an electrode structure can exhibit improved high-rate and lifetime characteristics.

[0155] It should be understood that the embodiments described herein are to be considered descriptive only and not for limiting purposes. Descriptions of features or aspects within each embodiment should generally be considered applicable to other similar features or aspects in other embodiments. Although one or more embodiments have been described with reference to the accompanying drawings, those skilled in the art will understand that various changes in form and detail may be made therein without departing from the spirit and scope defined by the appended claims.

[0156] This application claims priority and benefit to Korean Patent Application No. 10-2020-0169843, filed on December 7, 2020, with the Korean Intellectual Property Office, the entire contents of which are incorporated herein by reference.

Claims

1. An electrode structure, comprising: Current collector; and The electrode active material layer on the surface of the current collector, The electrode active material layer includes an electrode active material and an opening penetrating the electrode active material layer; and A conductive layer, comprising a conductive material and an adhesive, and on the inner surface of the opening, and The content of the conductive material and the binder is 0.05% to 3% by weight, based on the total weight of the electrode active material layer. The opening extends from the surface of the electrode active material layer facing the current collector to the opposite surface.

2. The electrode structure according to claim 1, wherein in at least 90% of the electrode active material layer not adjacent to the conductive layer, the content of the conductive material and the binder is at most 0.01 by weight based on the total weight of the electrode active material layer.

3. The electrode structure according to claim 1, wherein the solid content of the electrode active material layer is 25% to 98% by volume.

4. The electrode structure according to claim 1, wherein the opening extends in a direction perpendicular to the surface of the electrode active material layer facing the current collector.

5. The electrode structure according to claim 1, wherein the electrode active material layer has a thickness of 30 micrometers to 200 micrometers.

6. The electrode structure according to claim 1, wherein the electrode active material layer comprises lithium transition metal oxide.

7. The electrode structure according to claim 1, wherein the opening is a channel that allows lithium ion migration.

8. The electrode structure according to claim 1, wherein the conductive layer has a thickness of 0.1 nanometers to 10 micrometers.

9. The electrode structure according to claim 1, wherein the conductive material comprises carbonaceous material, metal, metal oxide, or a combination thereof.

10. The electrode structure according to claim 1, wherein the conductive material comprises: Carbon particles, carbon fibers, carbon nanotubes, or combinations thereof, including carbon black, natural graphite, artificial graphite, or combinations thereof; Metal particles, metal fibers, metal tubes, metal oxide particles, metal oxide fibers, or combinations thereof, including copper, nickel, aluminum, cobalt, chromium, palladium, molybdenum, silver, gold, thallium, tungsten, iron, titanium, platinum, or combinations thereof; or Their combination.

11. The electrode structure according to claim 1, wherein the adhesive comprises vinylidene fluoride / hexafluoropropylene copolymer, polyvinylidene fluoride, polyacrylonitrile, polymethyl methacrylate, polytetrafluoroethylene, polyamide-imide, styrene-butadiene, or a combination thereof.

12. The electrode structure according to claim 1, further comprising a conductive bonding layer between the current collector and the electrode active material layer.

13. The electrode structure according to claim 12, wherein the conductive bonding layer comprises a conductive material and an adhesive.

14. The electrode structure according to claim 12, wherein the conductive bonding layer has the same composition as the conductive layer.

15. A positive electrode comprising the electrode structure of claim 1.

16. An electrochemical device, comprising: The positive electrode according to claim 15; negative electrode; as well as The electrolyte between the positive electrode and the negative electrode.

17. The electrochemical device of claim 16, wherein the electrolyte is disposed in the opening.

18. The electrochemical device of claim 17, wherein the electrolyte comprises a liquid electrolyte, a solid electrolyte, or a gel electrolyte.

19. The electrochemical device of claim 16, wherein the negative electrode comprises a carbonaceous material, a transition metal oxide, a non-transition metal oxide, lithium metal, a metal alloyable with lithium, or a combination thereof.

20. The electrochemical device according to claim 16, further comprising a partition.

21. The electrochemical device of claim 16, wherein the operating voltage of the electrochemical device is 4 volts or higher.

22. A method for preparing an electrode structure, the method comprising: Provide electrode active material compositions; The electrode active material composition is coated onto a substrate; Heating the electrode active material composition to prepare an electrode active material layer; An opening is formed that penetrates the electrode active material layer; A conductive bonding layer composition is coated onto a current collector to form a coated current collector; as well as The electrode active material layer is pressed onto the coated current collector to prepare a press-fit structure and a conductive layer is formed on the inner surface of the opening. The press-fit structure includes a conductive bonding layer between the current collector and the electrode active material layer. as well as Annealing the press-fit structure to prepare the electrode structure of claim 1. The opening extends from the surface of the electrode active material layer facing the current collector to the opposite surface.

23. The method of claim 22, wherein the conductive layer comprises a conductive material and an adhesive, and the content of the conductive material and the adhesive is at most 0.01 by weight in at least 90% of the electrode active material layer not adjacent to the conductive layer, based on the total weight of the electrode active material layer.

24. The method of claim 22, wherein the solid content of the electrode active material layer is 25% to 98% by volume.

25. The method of claim 22, wherein the crimping comprises crimping the electrode active material layer to the current collector such that the conductive bonding layer composition coated on the current collector diffuses to the inner surface of the opening.

26. The method of claim 22, wherein the electrode active material composition comprises a lithium transition metal oxide.

27. The method of claim 22, wherein the opening has a size of 0.1 nanometers to 200 micrometers.

28. The method of claim 22, wherein the conductive bonding layer composition and the conductive layer comprise a conductive material and an adhesive.

29. The method of claim 22, wherein the conductive layer comprises a conductive material and an adhesive, the weight ratio of the conductive material to the adhesive being from 4:6 to 7:

3.

30. The method of claim 22, wherein the conductive bonding layer has a thickness of 0.1 nanometers to 20 micrometers.

31. The method of claim 22, wherein the conductive layer has a thickness of 0.1 nanometers to 10 micrometers.

32. The method of claim 22, further comprising cleaning the exposed surface of the electrode active material layer between the pressing and the annealing to remove residues remaining on the exposed surface.

33. An electrode structure comprising: Current collector; and An electrode active material layer on the surface of the current collector comprises a lithium transition metal oxide and has a thickness of 35 micrometers to 50 micrometers, wherein the electrode active material layer includes an opening penetrating the electrode active material layer, and wherein the opening has a size of 10 micrometers to 50 micrometers. The conductive layer on the surface of the opening has a thickness of 100 nanometers to 1 micrometer; as well as A conductive bonding layer between the current collector and the electrode active material layer, wherein the conductive bonding layer has the same composition as the conductive layer. The opening extends from the surface of the electrode active material layer facing the current collector to the opposite surface.

Images