Negative electrode and lithium-ion secondary battery including the negative electrode

Abstract

The present invention provides a negative electrode including a current collector and a negative electrode active material layer, the negative electrode active material layer including one or more active material layers containing 2 to 10 at% of oxygen, and a lithium ion secondary battery including the negative electrode.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0144769 filed on November 2, 2022 and Korean Patent Application No. 10-2023-0148135 filed on October 31, 2023, and all the contents disclosed in the documents of the Korean patent applications are included as part of this specification.

[0002] The present invention relates to a negative electrode and a lithium-ion secondary battery including the negative electrode.

Background Art

[0003] Recently, all-solid-state secondary batteries using a solid electrolyte as an electrolyte have attracted attention. In order to improve the energy density of such all-solid-state secondary batteries, it has been proposed to use lithium as a negative electrode active material. The capacity density of lithium (capacity per unit weight) is about 10 times that of graphite generally used as a negative electrode active material. Therefore, when lithium is used as a negative electrode active material, it is possible to increase the output while thinning the all-solid-state secondary battery.

[0004] As an all-solid-state lithium-ion secondary battery, for example, an anode-less lithium-ion secondary battery including a negative electrode active material layer containing a metal that forms an alloy with lithium and a carbon material is known.

[0005] The anode-less lithium-ion secondary battery as described above is driven by a mechanism in which metallic lithium is deposited between the negative electrode active material layer and a current collector during charging, and the metallic lithium is ionized and moves to the positive electrode side during discharging.

[0006] The negative electrode active material layer is formed of a very thin film having a micro thickness, but there has been a problem that it is difficult to form a negative electrode active material layer having a low surface roughness.

Prior Art Documents

Patent Documents

[0007] [Patent Document 1] Korean Patent Publication No. 2015-0064697 [Summary of the Invention] [Problems to be Solved by the Invention]

[0008] The present invention has been devised to solve the above-described problems of the prior art, and an object thereof is to provide a negative electrode in which a carbon material and a metal in a negative electrode active material layer are uniformly distributed and the surface roughness is remarkably improved, thereby significantly improving the driving characteristics of a battery, and a lithium ion secondary battery having improved performance including the same. [Means for Solving the Problems]

[0009] To achieve the above object, the present invention provides a negative electrode including a current collector and a negative electrode active material layer, wherein the negative electrode active material layer includes one or more active material layers containing 2 to 10 at% of oxygen.

[0010] Further, the present invention provides a lithium ion secondary battery including the negative electrode; a positive electrode; and an electrolyte interposed between the negative electrode and the positive electrode. [Effects of the Invention]

[0011] The negative electrode of the present invention includes a negative electrode active material layer in which a carbon material and a metal are uniformly distributed and the surface roughness is remarkably improved, thereby providing an effect of significantly improving the driving characteristics of a battery.

[0012] Further, the lithium ion secondary battery of the present invention includes the negative electrode active material layer, thereby providing excellent driving characteristics. [Brief Description of the Drawings]

[0013]

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Mode for Carrying Out the Invention

[0014] Hereinafter, in order to assist the understanding of the present invention, the present invention will be described in more detail.

[0015] The terms and words used in this specification and the claims should not be construed in a normal or dictionary-limited sense. Based on the principle that the inventor can appropriately define the concept of the terms in order to explain his or her invention in the best way, they must be construed in a meaning and concept that conforms to the technical idea of the present invention. Also, the terms used in this specification are merely for explaining exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly indicates a different meaning.

[0016] When a component is referred to as "connected to, provided with, or installed on" another component, it should be understood that it may be directly connected or installed on the other component, but there may also be other components in between. On the contrary, when a component is referred to as "directly connected to, or installed on" another component, it should be understood that there are no other components in between. On the other hand, other expressions for explaining the relationship between components, namely, "above ~" and "directly above", or "between ~" and "immediately between ~", or "adjacent to ~" and "directly adjacent to ~", etc. should be interpreted in the same way.

[0017] In this specification, the term "combination" includes mixtures, alloys, reaction products, etc., unless otherwise stated to the contrary.

[0018] The electrode of the present invention includes a current collector and a negative electrode active material layer. The negative electrode active material layer is characterized by including one or more active material layers containing 2 to 10 at% of oxygen.

[0019] The lower limit value of the oxygen content can be 2.5 at% or more, 3 at% or more, 3.5 at% or more, 4 at% or more, 4.5 at% or more, or 5 at% or more. Also, the upper limit value of the oxygen content can be 9.5 at% or less, 9 at% or less, 8.5 at% or less, 8 at% or less, 7.5 at% or less, 7 at% or less, 6.5 at% or less, 6 at% or less, 5.5 at% or less, 5 at% or less, 4.5 at% or less, 4 at% or less, 3.5 at% or less, or 3 at% or less. The oxygen content can be in the range constituted by the combination of the lower limit value and the upper limit value. Specifically, it may preferably be the case where the oxygen is contained at 2.5 to 10 at%.

[0020] In the above, when oxygen is contained at less than 2 at%, the surface roughness of the active material layer is significantly reduced, which is not preferable. When it exceeds 10 at%, the performance of the battery deteriorates due to side reactions with the solid electrolyte, which is not preferable.

[0021] In one embodiment of the present invention, the one or more active material layers may further contain 65 to 85 at% of carbon and 0.5 to 5 at% of a metal element, and more preferably, may further contain 74 to 85 at% of carbon and 0.5 to 3 at% of a metal element.

[0022] In one embodiment of the present invention, the one or more active material layers may further contain 5 to 25 at% of fluorine (F), and more preferably, may further contain 10 to 20 at% of fluorine (F).

[0023] In one embodiment of the present invention, the one or more active material layers may further contain 0.01 to 1 at% of sulfur (S), and more preferably, may further contain 0.01 to 0.5 at% of sulfur (S).

[0024] In one embodiment of the present invention, the one or more active material layers may contain 2 to 10 at% of oxygen, 65 to 85 at% of carbon, 0.5 to 5 at% of a metal element, and 5 to 25 at% of fluorine (F).

[0025] More preferably, it can contain 2.5 to 5 at% of oxygen, 74 to 85 at% of carbon, 0.5 to 3 at% of a metal element, and 10 to 20 at% of fluorine (F).

[0026] In addition, the sulfur (S) can be further contained as an additional component in the above components.

[0027] The component ratio of the one or more active material layers can be measured using a photoelectron spectrometer (XPS or ESCA). For example, the component ratio of the one or more active material layers can be measured using a Nexsa4 (Thermo Fisher Scientific) apparatus.

[0028] In one embodiment of the present invention, the one or more active material layers can contain carbon material particles and metal particles, and the carbon material particles can be, for example, amorphous carbon material particles. However, the carbon material particles are not limited to amorphous particles. Specific examples of the amorphous carbon material include carbon blacks such as acetylene black, furnace black, and ketjen black, graphene, or combinations thereof.

[0029] When the amorphous carbon material particles contain pores, the size of the pores can be 1 nm or less, preferably 0.5 nm or less. However, it is more preferable that the amorphous carbon material particles do not contain pores. This is because when the amorphous carbon material particles contain pores, lithium may be deposited inside the pores, and such lithium may be inactivated, and the amount of lithium thus inactivated may increase as charge and discharge are repeated.

[0030] The pore size of the amorphous carbon material particles can be measured, for example, through a nitrogen adsorption experiment or through a transmission electron microscope.

[0031] The carbon material particles can be carbon material particles containing 3 to 10 at% of oxygen. In the above, when the oxygen content is less than 3 at%, the surface roughness of the active material layer is significantly reduced, which is not preferable. When it exceeds 10 at%, the performance of the battery deteriorates due to side reactions with the solid electrolyte, which is not preferable.

[0032] In the above, the lower limit value of the oxygen content can be 3.5 at% or more, 4 at% or more, or 4.5 at% or more. Also, the upper limit value of the content can be 9.5 at% or less, 9 at% or less, 8 at% or less, 7.5 at% or less, 7 at% or less, 6.5 at% or less, 6 at% or less, or 5.5 at% or less. The oxygen content can be in the range constituted by the combination of the lower limit value and the upper limit value. Specifically, the oxygen content can preferably be 5 to 10 at%.

[0033] In one embodiment of the present invention, the oxygen can be present in a form contained in a functional group bonded to the carbon material particles. Also, the functional group may contain one or more selected from the group consisting of a carboxyl group, a hydroxyl group, an ether group, an ester group, an aldehyde group, a carbonyl group, and an amide group.

[0034] The carbon material particles containing 3 to 10 at% of oxygen can be produced, for example, by a method of oxidizing a carbon material. Specifically, the carbon material can be treated with an acid and reacted while stirring at a temperature of 25°C to 60°C to introduce oxygen functional groups onto the surface of the carbon material. The type of the acid is not particularly limited, and any acid can be used as long as it can introduce oxygen functional groups onto the surface of the carbon material. Examples of the acid include sulfuric acid, nitric acid, or a mixture thereof, and an oxidizing agent such as potassium permanganate can also be used.

[0035] The content of oxygen contained in the carbon material can be measured using a photoelectron spectrometer (XPS or ESCA). For example, it can be measured using a K-Alpha (Thermo Fisher Scientific) device.

[0036] In one embodiment of the present invention, the oxygen may be present on the surface of the carbon material particles. The surface does not mean only the outer surface of the carbon material particles, and when pores are present, it includes the surfaces of the pores.

[0037] In one embodiment of the present invention, the metal particles may be particles that form an alloy with lithium, and the metal particles may be one or more particles selected from silver (Ag), gold, platinum, palladium, silicon, aluminum, bismuth, tin, indium, and zinc.

[0038] In one embodiment of the present invention, the metal particles may preferably contain silver (Ag).

[0039] In one embodiment of the present invention, the one or more active material layers can have the following surface roughness characteristics: 0.01 μm ≤ Sa ≤ 0.3 μm 0.5 μm ≤ Sz ≤ 5 μm 500 mm -1 ≤ Spc ≤ 1500 mm -1 0.005 ≤ Sdr ≤ 0.15

[0040] When the surface roughness satisfies the above range, the characteristics of the general battery can be improved, and in particular, the life characteristics can be improved. Specifically, when the surface roughness of the negative electrode active material layer exceeds the above range, sufficient contact with the electrolyte layer is not achieved in the electrolyte side direction, and it is not helpful for the uniform precipitation of lithium in the negative electrode current collector side direction, so the characteristics of the battery may be deteriorated.

[0041] In the above, the surface roughness of the negative electrode active material layer can be measured using a microscope device. For example, it can be measured using a 3D confocal laser microscope (manufactured by KEYENCE) device.

[0042] In the above, Sa (arithmetic mean height of profile) can be at most 0.3 μm or less, 0.2 μm or less, 0.1 μm or less, 0.08 μm or less, or 0.075 μm or less, and can be at least 0.01 μm or more, 0.02 μm or more, 0.03 μm or more, 0.04 μm or more, 0.05 μm or more, 0.06 μm or more, or 0.07 μm or more. Also, the Sa can more preferably be in the range of 0.01 μm ≤ Sa ≤ 0.1 μm, but is not limited to these ranges and can be set within the combined range of the maximum and minimum values. The Sa indicates the average value of the absolute values of the differences in height between each point with respect to the average plane of the surface.

[0043] In the above, Sz (maximum height roughness of profile) can be at most 5 μm or less, 4 μm or less, 3 μm or less, 2 μm or less, or 1.5 μm or less, and can be at least 0.5 μm or more, 0.8 μm or more, 1 μm or more, 1.1 μm or more, 1.2 μm or more, or 1.3 μm or more. Also, the Sz can more preferably be in the range of 0.5 μm ≤ Sz ≤ 1.6 μm, but is not limited to these ranges and can be set within the combined range of the maximum and minimum values. The Sz is the maximum height roughness within a single plane and indicates the distance between the highest point and the lowest point within a single plane.

[0044] In the above, Spc (roughness by number of peaks) can be at most 1500 mm -1 or less, 1400 mm -1 or less, 1300 mm -1 or less, 1200 mm -1 or less, 1100 mm -1 or less, or 1000 mm -1 or less, and can be at least 500 mm -1 or more, 600 mm -1 or more, 700 mm -1 or more, 800 mm -1 or more, or 900 mm -1 or more. Also, 500 mm -1 ≤ Spc ≤ 1100 mm -1The range may be more preferably within, but is not limited to, these ranges, and can be set within the combined range of the maximum and minimum values. The Spc is the roughness based on the number of peaks and is a measure indicating the degree of sharpness of the peaks.

[0045] In the above, Sdr (degree of increase in interface area) can be at most 0.15 or less, 0.1 or less, 0.05 or less, 0.03 or less, or 0.02 or less, and can be at least 0.005 or more, 0.01 or more, or 0.015 or more. Also, the range of 0.005 ≤ Sdr ≤ 0.03 may be more preferable, but is not limited to this range, and can be set within the combined range of the maximum and minimum values. The Sdr is the degree of increase in the interface and means the ratio of the increased area to the area when looking vertically at the measurement region of the developed area (the surface area of the measured shape).

[0046] In the above, the meanings of Sa, Sz, Spc, and Sdr are described, and these are used in the same meaning as the meanings commonly used in this field.

[0047] In one embodiment of the present invention, the one or more active material layers can have a porosity of 55 to 70%, and more preferably 62 to 67%. When the porosity satisfies the above range, a preferable effect can be obtained in terms of ensuring the uniformity of the coating layer within the electrode.

[0048] In the above, the porosity of the active material layer is a value calculated using the weight and thickness values of the active material layer.

[0049] In one embodiment of the present invention, the one or more active material layers can contain 60 to 80% by weight of carbon material particles containing 3 to 10 at% of oxygen, 10 to 30% by weight of metal particles, and 3 to 20% by weight of a binder. Also, the one or more active material layers can contain 65 to 75% by weight of carbon material particles containing 3 to 10 at% of oxygen, 20 to 30% by weight of metal particles, and 4 to 8% by weight of a binder.

[0050] In one embodiment of the present invention, the carbon material particles and the metal particles can be included in the form of a carbon material-metal composite.

[0051] Recently, as all-solid-state lithium-ion secondary batteries, for example, anode-less lithium-ion secondary batteries including a negative electrode active material layer containing a metal that forms an alloy with lithium and a carbon material have been variously studied.

[0052] The negative electrode active material layer is formed of a very thin film with a micro thickness and is manufactured in a form including a carbon material-metal composite in which carbon material particles and metal particles are bonded. However, the conventional carbon material-metal composite has a problem that it is difficult for the carbon material particles and the metal particles to be uniformly distributed.

[0053] Furthermore, the conventional carbon material-metal composite has a problem that it is very difficult to form a small particle size. That is, when the particle size of the carbon material-metal composite is too large with respect to the thin film with a micro thickness, it is difficult to form a negative electrode active material layer having excellent surface roughness, and thereby the driving characteristics of the battery also deteriorate. Therefore, it is very important to manufacture the carbon material-metal composite with a small particle size.

[0054] The present invention provides an effect of epoch-making improvement of the above problems of the prior art.

[0055] That is, the carbon material-metal composite forms a carbon material-metal composite having a significantly smaller particle size compared to the case of using a conventional carbon material. The carbon material forming the composite contains 3 at% or more of the oxygen, mixes well with the metal particles, and has a property of being uniformly distributed with the metal particles. Therefore, it is possible to manufacture a carbon material-metal composite having excellent component uniformity. Also, for the above reasons, it is possible to manufacture a carbon material-metal composite having a small and uniform particle size.

[0056] In one embodiment of the present invention, the carbon material-metal composite may be composed of one or more bonds selected from chemical bonds between carbon material particles and metal particles, van der Waals bonds between carbon material particles and metal particles, and bonds by a binder between carbon material particles and metal particles. The chemical bond may be a metal (e.g., Ag)-O bond between a metal particle (e.g., Ag) and oxygen contained in the carbon material.

[0057] In one embodiment of the present invention, the carbon material-metal composite may contain 60 to 90% by weight of a carbon material and 10 to 40% by weight of a metal based on the total weight. Further, it may contain 70 to 80% by weight of a carbon material and 20 to 30% by weight of a metal.

[0058] Further, the carbon material-metal composite may further contain 3 to 10% by weight of a binder based on the total weight of the composite. For example, when wet-producing the carbon material-metal composite, a binder dissolved in a solvent together with carbon material particles and metal particles can be used, and in this case, the carbon material-metal composite can contain the binder. When the binder is contained, the content of the carbon material can be included in a range where the content is decreased by only the content of the binder.

[0059] In one embodiment of the present invention, carbon material particles having a particle size (D50) of 10 nm to 100 nm or 20 nm to 60 nm can be used, and metal particles having a particle size (D50) of 20 nm to 100 nm, 20 nm to 60 nm, or 30 nm to 60 nm can be used.

[0060] In one embodiment of the present invention, the particle size (D50) of the carbon material-metal composite can be 0.1 μm to 0.5 μm. The upper limit value of the particle size can be 0.4 μm or 0.3 μm.

[0061] Further, the maximum particle size of the carbon material-metal composite can be 3 μm or less, 2 μm or less, 1.5 μm or less, 1 μm or less.

[0062] When the particle size of the carbon material-metal composite is too large for a thin film with a micro thickness, it is difficult to form a negative electrode active material layer having excellent surface roughness, and this also deteriorates the driving characteristics of the battery. Therefore, it is very important to produce the carbon material-metal composite with a small particle size.

[0063] The reason for the deterioration of the driving characteristics of the battery is that when the surface roughness of the negative electrode active material layer is large, sufficient contact with the electrolyte layer is not made in the electrolyte side direction, and it does not contribute to the uniform precipitation of lithium in the negative electrode current collector side direction.

[0064] In the anode-less lithium ion secondary battery, the thickness of the negative electrode active material layer can usually be formed in the range of 1 μm to 100 μm, or 10 μm to 60 μm, and specifically, it can be formed with a thickness of 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc.

[0065] For example, when using a carbon material-metal composite with a particle size of 10 μm to form a negative electrode active material layer with a thickness of 20 μm, it is obvious that it is difficult to form a preferable surface roughness.

[0066] When the maximum particle size of the carbon material-metal composite is 3 μm or less, it is preferable because the surface roughness improvement effect can be obtained more surely. On the other hand, when it exceeds 3 μm, it may be difficult to obtain excellent surface roughness during the formation of the thin film.

[0067] The particle size of the carbon material-metal composite can be measured using a particle size analyzer. For example, it can be measured using a Mastersizer 3000 (Malvem panalytical) device.

[0068] The present invention relates to a negative electrode active material slurry containing the carbon material-metal composite.

[0069] The negative electrode active material slurry has a shear rate of 2.5 s -1The viscosity at [specific condition] can be 8 Pa·s or less, 7 Pa·s or less, 6 Pa·s or less, or 5 Pa·s or less.

[0070] The negative electrode active material slurry can contain 15 to 50% by weight of the carbon material-metal composite, 1 to 10% by weight of the binder (based on solid content), and 40 to 80% by weight of the solvent. Preferably, it can contain 25 to 35% by weight of the carbon material-metal composite, 1 to 5% by weight of the binder, and 60 to 70% by weight of the solvent. Further, it can contain additives included in the negative electrode active material slurry in this field.

[0071] The present invention relates to a negative electrode active material layer containing the carbon material-metal composite.

[0072] In the negative electrode active material layer, the carbon material and the metal are uniformly distributed, and the surface roughness is excellent, providing an effect of improving the driving characteristics of the lithium-ion secondary battery including the same.

[0073] Further, the present invention provides a lithium-ion secondary battery including the negative electrode; a positive electrode; and an electrolyte interposed between the negative electrode and the positive electrode.

[0074] The lithium-ion secondary battery can be an anode-less battery.

[0075] By including the negative electrode active material layer of the present invention, the lithium-ion secondary battery provides improved driving characteristics.

[0076] In one embodiment of the present invention, the solid electrolyte can be a sulfide-based solid electrolyte.

[0077] In one embodiment of the present invention, the lithium-ion secondary battery can be an anode-less battery.

[0078] Hereinafter, embodiments of the present invention will be illustrated more specifically.

[0079] <Configuration of All-Solid-State Lithium-Ion Secondary Battery> FIG. 1 is a cross-sectional view showing a schematic configuration of an all-solid-state lithium-ion secondary battery according to an embodiment of the present invention.

[0080] An all-solid-state lithium-ion secondary battery (100) according to an embodiment of the present invention is a so-called lithium-ion secondary battery that performs charge and discharge by the movement of lithium ions between a positive electrode (10) and a negative electrode (20). Specifically, as shown in FIG. 1, this all-solid-state lithium-ion secondary battery (100) is composed of a positive electrode (10), a negative electrode (20), and a solid electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20).

[0081] (1) Positive Electrode As shown in FIG. 1, the positive electrode (10) includes a positive electrode current collector (12) and a positive electrode active material layer (14) arranged in order toward the negative electrode (20).

[0082] The positive electrode current collector (12) can be plate-shaped or foil-shaped. The positive electrode current collector (12) can be, for example, one kind of metal selected from indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, lithium, or an alloy of two or more kinds of metals.

[0083] The positive electrode active material layer (14) can reversibly occlude and release lithium ions. The positive electrode active material layer (14) can include a positive electrode active material and a solid electrolyte.

[0084] The positive electrode active material can be a compound capable of inserting / desorbing lithium. Examples of the compound capable of inserting / desorbing lithium include Li a A 1-b B’ b D’2 (in the above formula, 0.90 ≦ a ≦ 1.8 and 0 ≦ b ≦ 0.5); Li a E1- b B’ b O 2-c D’ c (in the above formula, 0.90 ≦ a ≦ 1.8, 0 ≦ b ≦ 0.5, 0 ≦ c ≦ 0.05); LiE 2-b B’ bO 4-c D’ c (In the above formula, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B’ c D’ α (In the above formula, 0.90 ≤ a ≤ 1.8, 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 (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B’ c D’ α (In the above formula, 0.90 ≤ a ≤ 1.8, 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 (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0.001 ≤ d ≤ 0.1); Li a Ni b Co c Mn d G e O2(In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2(In the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(In the above formula, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG bO2 (in the above formula, 0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); Li a Mn2G b O4 (in the above formula, 0.90 ≦ a ≦ 1.8, 0.001 ≦ b ≦ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI’O2; LiNiVO4; Li (3-f) J2(PO4)3 (0 ≦ f ≦ 2); Li (3-f) Any one of the chemical formulas of Fe2(PO4)3 (0 ≦ f ≦ 2); LiFePO4 can be cited.

[0085] 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.

[0086] Specific examples of the positive electrode active material include lithium salts such as lithium cobaltate (hereinafter referred to as LCO), lithium nickelate, lithium nickel cobaltate, lithium nickel cobalt aluminum oxide (hereinafter referred to as NCA), lithium nickel cobalt manganese oxide (hereinafter referred to as NCM), lithium manganate, and lithium iron phosphate, and lithium sulfide and the like. The positive electrode active material layer (14) may contain only one kind selected from these compounds as the positive electrode active material, or may contain two or more kinds.

[0087] The positive electrode active material can include a lithium salt of a transition metal oxide having a layered rock salt structure among the aforementioned lithium salts. Here, the "layered rock salt structure" is a structure in which oxygen atom layers and metal atom layers are alternately and regularly arranged in the direction of the cubic rock salt structure, and as a result, each atom layer forms a two-dimensional plane. Also, the "cubic rock salt structure" means a sodium chloride type structure which is a kind of crystal structure. For example, the "cubic rock salt structure" indicates a structure in which face-centered cubic lattices formed by cations and anions respectively are arranged with a shift of 1 / 2 of the unit lattice angle from each other.

[0088] Examples of such lithium salts of transition metal oxides having a layered rock salt structure include, for example, LiNi x Co y Al z O2 (NCA) or LiNi x Co y Mn z O2 (NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1), etc., can be ternary lithium transition metal oxides. The positive electrode active material layer (14) contains a lithium salt of a ternary transition metal oxide having such a layered rock salt structure as the positive electrode active material, and can improve the energy density and thermal stability of the all-solid-state lithium ion secondary battery (100).

[0089] Here, examples of the shape of the positive electrode active material can include particle shapes such as true spherical and elliptical spherical. Also, the particle size of the positive electrode active material is not particularly limited as long as it is within the range applicable to the positive electrode active material of a normal all-solid-state lithium ion secondary battery. Also, in the positive electrode active material layer (14), the content of the positive electrode active material is not particularly limited and is possible as long as it is within the range applicable to the positive electrode of a normal all-solid-state lithium ion secondary battery.

[0090] Of course, those having a coating layer on the surface of the compound can also be used, or the compound and the compound having a coating layer can be mixed and used. This coating layer can contain a coating element compound such as an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of the coating element. The compounds constituting these coating layers can be amorphous or crystalline. Examples of the coating element contained in the coating layer include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. As long as the coating layer forming process uses these elements on the compound and can coat it by a method that does not adversely affect the physical properties of the positive electrode active material (for example, spray coating, dipping method, etc.), any coating method can be used. Since this is content that can be understood by those skilled in the art, detailed description thereof is omitted.

[0091] Specific examples of the coating layer include Li2O-ZrO2 and the like.

[0092] The solid electrolyte contained in the positive electrode active material layer (14) may be the same type as or different from the solid electrolyte contained in the solid electrolyte layer (30) described later.

[0093] In addition, the positive electrode active material layer (14) may be appropriately blended with additives such as a conductive material, a binder, a filler, a dispersant, or an ion conductivity assisting agent, in addition to the aforementioned positive electrode active material and solid electrolyte.

[0094] Examples of the conductive material include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or metal powder. Examples of the binder include styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. As the filler, dispersant, or ionic conductivity assisting agent, etc., known materials usually used for electrodes of all-solid-state lithium-ion secondary batteries can be used.

[0095] (2) Negative electrode The negative electrode (20) can include a negative electrode current collector (22) and a negative electrode active material layer (24) arranged in order toward the positive electrode (10).

[0096] The negative electrode current collector (22) can be plate-shaped or foil-shaped. The negative electrode current collector (22) can include a material that does not react with lithium, that is, a material that does not form any alloy or compound with lithium. Examples of the material constituting the negative electrode current collector (22) include copper, stainless steel, titanium, iron, cobalt, and nickel. The negative electrode current collector (22) may consist of one of these metals, or may consist of an alloy or clad material of two or more metals.

[0097] In the initial state or after full discharge, the negative electrode active material layer (24) may not contain lithium between the negative electrode current collector (22), the negative electrode active material layer (24), or between the negative electrode active material layer (24) and the solid electrolyte layer (30). As will be described later, when the all-solid-state lithium-ion secondary battery (100) according to one embodiment is overcharged, the negative electrode active material contained in the negative electrode active material layer (24) and the lithium ions that have migrated from the positive electrode (10) form an alloy or a compound, and as shown in FIG. 2, a metal layer (26) mainly composed of lithium may be formed (deposited) on the negative electrode (20). The metal layer (26) may be deposited and disposed between the negative electrode current collector (22) and the negative electrode active material layer (24), inside the negative electrode active material layer (24), or all of these. Between the negative electrode current collector (22) and the negative electrode active material layer (24), the metal layer (26) mainly composed of lithium may be disposed closer to the negative electrode current collector layer (22) than the negative electrode active material layer (24).

[0098] The negative electrode active material layer (24) according to one embodiment can contain Ag as the negative electrode active material. Therefore, the metal layer (26) formed during overcharging can contain a Li(Ag) alloy containing a γ1 phase, a βLi phase, or a combination of these phases in which Ag is dissolved in lithium. Therefore, during discharge, only Li dissolves from the Li(Ag) alloy constituting the metal layer (26), and the dissolved Ag remains, suppressing the generation of voids. In this case, the content of Ag in the precipitated Li-Ag solid solution can be 60% by weight or less. Within such a range, the decrease in the average discharge potential due to the influence of Ag can be effectively suppressed. On the other hand, if the content of Ag in the precipitated Li-Ag solid solution is too small, the amount of Ag remaining during discharge decreases, and in some cases, the generation of voids cannot be sufficiently suppressed. For this reason, the content of Ag in the precipitated Li-Ag solid solution can be 20% by weight or more, for example, 40% by weight or more.

[0099] If the content of Ag contained in the negative electrode active material layer (24) is too small, the amount of Ag remaining during discharge also decreases, so it may become impossible to suppress the generation of voids. For this reason, the negative electrode active material layer (24) can contain 10% by weight or more, for example, 20% by weight or more of Ag, based on 100% by weight of the total negative electrode active material contained in the negative electrode active material layer in the initial state where charge and discharge are not performed.

[0100] The negative electrode active material layer (24) can further contain, as an arbitrary negative electrode active material other than Ag, for example, one or more selected from amorphous carbon, Au, Pt, Pd, Si, Al, Bi, Sn, In, and Zn.

[0101] As the carbon material contained in the negative electrode active material layer (24), amorphous carbon can be preferably used. However, the carbon material is not limited to amorphous carbon. Specific examples of the amorphous carbon include carbon black such as acetylene black, furnace black, and ketjen black, graphene, or a combination thereof.

[0102] Based on 100% by weight of the total negative electrode active material contained in the negative electrode active material layer (24), the negative electrode active materials other than Ag can be 50% by weight or more, for example, 70% by weight or more. The content of the negative electrode active material other than Ag can be measured by the same method as the content of the Ag.

[0103] The negative electrode active material layer (24) can further contain a binder. By including a binder, the negative electrode active material layer (24) can be stabilized on the negative electrode current collector (22). Examples of the material constituting the binder include resin materials such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. The binder can be composed of one or more selected from these resin materials.

[0104] Further, the negative electrode active material layer (24) may be appropriately blended with additives used in ordinary all-solid-state lithium-ion secondary batteries, such as fillers, dispersants, ion conductive materials, etc. Specific examples of the additives are the same as those described for the positive electrode above.

[0105] The total thickness of the negative electrode active material layer (24) is not particularly limited, but can be 1 μm to 100 μm, or 10 μm to 60 μm. When the thickness of the negative electrode active material layer (24) is less than 1 μm, the performance of the all-solid-state secondary battery may not be sufficiently improved. When the thickness of the negative electrode active material layer (24) exceeds 100 μm, the resistance of the negative electrode active material layer (24) is high, and as a result, the performance of the all-solid-state secondary battery may not be sufficiently improved. When using the above-mentioned binder, the thickness of the negative electrode active material layer (24) can be easily ensured at an appropriate level.

[0106] On the other hand, the negative electrode current collector (22) further includes a film containing a material capable of forming an alloy or compound with lithium, and the film can be disposed between the negative electrode current collector (22) and the negative electrode active material layer (24).

[0107] The negative electrode current collector (22) does not react with lithium metal, but can make it difficult to deposit a smooth lithium metal layer on the upper part. The film can also be used as a wetting layer for the lithium metal to deposit flatly on the upper part of the negative electrode current collector (22).

[0108] Examples of materials capable of forming an alloy with lithium metal used for the film include silicon, magnesium, aluminum, lead, silver, tin, or combinations thereof. Examples of materials capable of forming a compound with lithium metal used for the film include carbon, titanium sulfide, iron sulfide, or combinations thereof. The content of the material used for the film may be small as long as it does not affect the electrochemical properties of the electrode and / or the redox potential of the electrode. The film can be applied flat on the negative electrode current collector (22) to prevent cracks during the charging cycle of the all-solid-state lithium-ion secondary battery (100). For applying the film, methods such as physical vapor deposition like evaporation or sputtering, chemical vapor deposition, or plating methods can be used.

[0109] The thickness of the film can be from 1 nm to 500 nm. For example, the thickness of the film can be from 2 nm to 400 nm. For example, the thickness of the film can be from 3 nm to 300 nm. For example, the thickness of the film can be from 4 nm to 200 nm. For example, the thickness of the film can be from 5 nm to 100 nm.

[0110] (3) Solid electrolyte layer The solid electrolyte layer (30) is disposed between the positive electrode (10) and the negative electrode (20) (for example, between the positive electrode active material layer (14) and the negative electrode active material layer (24)). The solid electrolyte layer (30) contains a solid electrolyte capable of moving ions. The solid electrolyte layer (30) can contain a sulfide-based solid electrolyte.

[0111] Examples of the sulfide-based solid electrolyte include Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n(m and n are positive numbers, and Z is any one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, or In), or combinations thereof can be included. The solid electrolyte may consist of one material selected from these sulfide-based solid electrolyte materials, or may consist of two or more materials.

[0112] The sulfide-based solid electrolyte can include a solid electrolyte represented by the following Chemical Formula 1: [Chemical Formula 1] Li x M’ y PS z A w In Chemical Formula 1, x, y, z, and w are independently 0 or more and 6 or less; M’ is one or more of As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta; A is one or more of F, Cl, Br, or I.

[0113] As the solid electrolyte, among the sulfide solid electrolyte materials, those containing sulfur (S), phosphorus (P), and lithium (Li) as constituent elements can be used. For example, those containing Li2S-P2S5 can be used. When using a material containing Li2S-P2S5 as the sulfide-based solid electrolyte material, the mixing molar ratio of Li2S and P2S5 can be selected, for example, in the range of Li2S:P2S5 = 50:50 to 90:10.

[0114] Also, the solid electrolyte may be in an amorphous state, a crystalline state, or a state in which amorphous and crystalline are mixed.

[0115] The solid electrolyte layer (30) can further contain a binder. Examples of the binder material include resins such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and polyacrylic acid. The binder material may or may not be the same as the material constituting the binder in the positive electrode active material layer (14) and the negative electrode active material layer (24).

[0116] (4) Structure of All-Solid-State Lithium-Ion Secondary Battery The all-solid-state lithium-ion secondary battery (100) of the present invention can be an all-solid-state lithium-ion secondary battery (100) including a positive electrode (10), a solid electrolyte layer (30), and a negative electrode (20) in this order as shown in FIG. 1. The negative electrode (20) includes a negative electrode current collector (22) and a negative electrode active material layer (24), and the negative electrode active material layer (24) includes a carbon material and a metal capable of forming an alloy with lithium.

[0117] The negative electrode current collector (22) can include a Ni foil, a Cu foil coated with Ni, a stainless steel foil, or a combination thereof. Such a negative electrode current collector (22) can further improve the discharge capacity.

[0118] <Manufacturing Method of All-Solid-State Lithium-Ion Secondary Battery> Next, a manufacturing method of the all-solid-state lithium-ion secondary battery (100) will be described. The all-solid-state lithium-ion secondary battery (100) according to one embodiment can be obtained by separately manufacturing the positive electrode (10), the negative electrode (20), and the solid electrolyte layer (30), and then laminating each of the above layers.

[0119] (1) Positive Electrode Manufacturing Step Taking the positive electrode manufacturing process as an example, it is as follows. First, materials constituting the positive electrode active material layer (14) (such as positive electrode active material, binder, etc.) are added to a non-polar solvent to prepare a slurry (or paste). Subsequently, the obtained slurry is coated on the prepared positive electrode current collector (12). This is dried to obtain a laminate. Subsequently, the obtained laminate is pressed, for example, using hydrostatic pressure to obtain the positive electrode (10). Also, the pressing process is omitted.

[0120] (2) Negative electrode manufacturing process Taking the negative electrode manufacturing process as an example, it is as follows. First, materials constituting the negative electrode active material layer (24) (such as carbon material, metal forming an alloy with lithium, binder, etc.) are added to a polar solvent or a non-polar solvent to produce a slurry (paste may also be used). Subsequently, the obtained slurry is coated on the prepared negative electrode current collector (22) to form a negative electrode active material layer.

[0121] When the negative electrode active material layer further includes one or more additional layers, the additional layers can be laminated in the above-described manner.

[0122] Subsequently, the laminate obtained by the above method is pressed, for example, using hydrostatic pressure to produce the negative electrode (20). Also, the pressing process may be omitted. Also, the method of coating the slurry on the negative electrode current collector (22) is not particularly limited, and examples include screen printing method, metal mask printing method, electrostatic coating method, dip coating method, spray coating method, roll coating method, doctor blade method, gravure coating method, etc.

[0123] In the above, the method of forming the negative electrode active material layer with two layers has been described. Even when forming additional layers, a slurry for forming each layer can be manufactured, and each layer can be sequentially laminated in the lamination order according to the method described above to manufacture the negative electrode.

[0124] (3) Solid electrolyte layer manufacturing process The solid electrolyte layer (30) can be manufactured, for example, using a solid electrolyte containing a sulfide-based solid electrolyte material.

[0125] First, starting materials (such as Li2S, P2S5, etc.) are processed by a melt quenching method or a mechanical milling method to obtain a sulfide-based solid electrolyte material. For example, when using the melt quenching method, a predetermined amount of starting materials are mixed, formed into pellets, reacted at a predetermined reaction temperature in a vacuum, and then quenched to produce a sulfide-based solid electrolyte material. Also, the reaction temperature of the mixture of Li2S and P2S5 can be 400°C to 1000°C, for example, 800°C to 900°C. Also, the reaction time can be 0.1 hour to 12 hours, for example, 1 hour to 12 hours. Also, the quenching temperature of the reaction product can be 10°C or lower, for example, 0°C or lower, and the quenching rate is usually 1°C / sec to 10000°C / sec, for example, 1°C / sec to 1000°C / sec.

[0126] Also, when using the mechanical milling method, a sulfide-based solid electrolyte material can be produced by stirring and reacting the starting materials using a ball mill or the like. Also, the stirring speed and stirring time of the mechanical milling method are not particularly limited, but the higher the stirring speed, the faster the production rate of the sulfide-based solid electrolyte material, and the longer the stirring time, the higher the conversion rate of the raw materials to the sulfide-based solid electrolyte material.

[0127] Thereafter, the obtained mixed raw materials (sulfide-based solid electrolyte material) are heat-treated at a predetermined temperature and then pulverized to produce a particulate solid electrolyte. When the solid electrolyte has a glass transition point, it may change from amorphous to crystalline by heat treatment.

[0128] Subsequently, the solid electrolyte obtained by the above method can be formed into a solid electrolyte layer (30) by using a known film-forming method such as an aerosol deposition method, a cold spray method, a sputtering method, etc. Also, the solid electrolyte layer (30) can be produced by pressing solid electrolyte particles. Also, the solid electrolyte layer (30) can be produced by mixing a solid electrolyte, a solvent, and a binder, applying, drying, and pressing.

[0129] (4) Lamination process A solid electrolyte layer (30) is disposed between the positive electrode (10) and the negative electrode (20), and this is pressurized using, for example, hydrostatic pressure or the like, whereby an all-solid-state lithium-ion secondary battery (100) according to one embodiment can be obtained.

[0130] The all-solid-state lithium-ion secondary battery (100) of the present invention does not require the application of a high external pressure using an end plate or the like, and even when the external pressure applied to the positive electrode (10), the negative electrode (20), and the solid electrolyte layer (30) during use is 1 MPa or less, it can provide an improved discharge capacity.

[0131] <Charging method for all-solid-state lithium-ion secondary battery> Next, a charging method for the all-solid-state lithium-ion secondary battery (100) will be described.

[0132] A charging method for the all-solid-state lithium-ion secondary battery (100) according to one embodiment can be to charge (i.e., overcharge) the all-solid-state lithium-ion secondary battery (100) beyond the charging capacity of the negative electrode active material layer (24).

[0133] At the initial stage of charging, lithium may be occluded in the negative electrode active material layer (24). When charging exceeds the charge capacity of the negative electrode active material layer (24), as shown in FIG. 2, lithium is deposited on the back surface of the negative electrode active material layer (24), that is, between the negative electrode current collector (22) and the negative electrode active material layer (24), and a metal layer (26) that did not exist during manufacturing may be formed by this lithium. During discharging, lithium in the negative electrode active material layer (24) and the metal layer (26) can be ionized and move to the positive electrode (10) side. Therefore, in the all-solid-state lithium-ion secondary battery (100) of the present invention, lithium can be used as the negative electrode active material. Further, since the negative electrode active material layer (24) coats the metal layer (26), it functions as a protective layer for the metal layer (26) and at the same time can suppress the precipitation and growth of dendritic metallic lithium. By doing so, short circuit and capacity degradation of the all-solid-state lithium-ion secondary battery (100) can be suppressed, and furthermore, the characteristics of the all-solid-state lithium-ion secondary battery (100) can be improved. Also, according to one embodiment, since the metal layer (26) is not formed in advance, the manufacturing cost of the all-solid-state lithium-ion secondary battery (100) can be reduced.

[0134] Further, the metal layer (26) is not limited to being formed between the negative electrode current collector (22) and the negative electrode active material layer (24) as shown in FIG. 2, and may be formed inside the negative electrode active material layer (24). Also, the metal layer (26) may be formed both between the negative electrode current collector (22) and the negative electrode active material layer (24) and inside the negative electrode active material layer (24).

[0135] The all-solid-state lithium-ion secondary battery (100) of the present invention can be fabricated with a structure of a unit cell having a positive electrode / separator / negative electrode structure, a bicell having a positive electrode / separator / negative electrode / separator / positive electrode structure, or a stacked battery structure in which the structure of the unit cell is repeated.

[0136] The shape of the all-solid-state lithium-ion secondary battery (100) of the present invention is not particularly limited, and examples thereof include a coin type, a button type, a sheet type, a laminated type, a cylindrical type, a flat type, a rectangular type, etc. Further, it can also be applied to large batteries used in electric vehicles and the like. For example, the all-solid-state lithium-ion secondary battery (100) can also be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). Further, it can be used in fields where a large amount of electric power storage is required. For example, it can be used in electric bicycles or electric tools.

[0137] Hereinafter, examples will be given for a specific description of the present invention. However, the examples according to the present invention can be deformed into various other forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to more fully explain the present invention to those having average knowledge in the art.

[0138] Production Example 1: Selection of Carbon Material Sample with Oxygen Functional Group Introduced Various types of commercially available carbon materials were purchased, and the oxygen content contained in each carbon material was analyzed by the following method. Carbon black with an oxygen content of 5.2 at% (Sample 1), carbon black with an oxygen content of 2.6 at% (Sample 2), and carbon black with an oxygen content of 1.3 at% (Sample 3) were selected and used.

[0139] <Analysis Method> (1) Analytical Instrument K-Alpha (Thermo Fisher Scientific), a photoelectron spectrometer (XPS or ESCA), was used.

[0140] (2) Analysis Method First, the survey scan spectrum and narrow scan spectrum for each sample were obtained. For the narrow scan spectrum, four points were measured at each position, and the average and deviation were calculated.

[0141] (3) Common ESCA experimental conditions X-ray source: Monochromated Al Ka (1486.6 eV) X-ray spot size: 400μm Operation mode: Constant Analyzer Energy (CAE) mode Survey scan: pass energy 200eV, energy step 1eV Narrow scan: scanned mode, pass energy 50eV, energy step 0.1eV Charge compensation: flood gun off SF: Al THERMO1, ECF: TPP-2M, BG subtraction: Smart

[0142]

Table 1

[0143] Example 1 and Comparative Examples 1-2: Preparation of the negative electrode active material slurry 6 g of carbon black with a particle size (D50) of 40 nm to 60 nm (Sample 1, Sample 2, or Sample 3), 2 g of Ag with a particle size (D50) of 40 nm to 60 nm, 9.33 g of a PVdF binder (solid content 6%), and 7.19 g of an NMP solution were placed in a Thinky mixer container and mixed 12 times for 3 minutes each at 2000 rpm. Then, after further adding 5 g of the NMP solution, it was mixed 5 times for 3 minutes each at 2000 rpm to produce the negative electrode active material slurries of Example 1 (using carbon black with an oxygen content of 5.2 at%), Comparative Example 1 (using carbon black with an oxygen content of 2.6 at%), and Comparative Example 2 (using carbon black with an oxygen content of 1.3 at%), respectively.

[0144] Experimental Example 1: Particle Size Measurement of Carbon Material-Metal Composite (1) Separation of Carbon Material-Metal Composite Sample A part of the carbon material-metal composite contained in the negative electrode active material slurries of Example 1 and Comparative Example 1 was taken and diluted with an NMP solution to prepare an analysis sample.

[0145] (2) Analytical Instrument Particle size analysis was performed using a particle size analyzer model Mastersizer 3000 (Malvem panalytical). Specifically, the carbon material-metal composite analysis sample 1 (Example 1, containing carbon black with an oxygen content of 5.2 at%) and the carbon material-metal composite analysis sample 2 (containing carbon black with an oxygen content of 2.6 at%) prepared in (1) above were each placed into the sample inlet of the apparatus so that the laser obscuration was 10 to 15%, and measurements were taken.

[0146] The analytical instrument can analyze in the particle size range of 0.01 μm to 3500 μm and is a particle size analyzer suitable for wet and dry dispersion types through laser diffraction.

[0147] (3) Analysis Results The particle size analysis results of the carbon material-metal composite analysis samples 1 and 2 are shown in Table 2 and Figure 3 below.

[0148]

Table 2

[0149] From the results in Table 2 above, it can be seen that the particle size of the carbon material-metal composite containing carbon black with an oxygen content of 5.2 at% is significantly smaller compared to the particle size of the carbon material-metal composite containing carbon black with an oxygen content of 2.6 at%. Also, according to the analysis results shown in Figure 3, the maximum particle size of the carbon material-metal composite containing carbon black with an oxygen content of 5.2 at% is 1 μm or less, and it can be seen that it is significantly smaller compared to the particle size of the carbon material-metal composite containing carbon black with an oxygen content of 2.6 at%.

[0150] Experimental Example 2: Measurement of Rheological Properties of Anode Active Material Slurry The rheological properties of the anode active material slurry of Example 1 (using carbon black with an oxygen content of 5.2 at%) and the anode active material slurry of Comparative Example 1 (using carbon black with an oxygen content of 2.6 at%) were measured using a rheometer, model name DHR-1 (TA instrument).

[0151] At this time, a 40 mm parallel plate was used for the geometry, and the viscosity of the slurry by shear was measured through a flow test. The oscillation frequency test was carried out before and after the viscosity measurement.

[0152] The measurement results of the rheological properties are shown in Figure 4.

[0153] In the case of a slurry with excellent dispersibility, the viscosity reduction rate due to an increase in shear is similar, and the viscosity change due to a decrease after an increase in shear is also similar. The viscosity inflection in the flow test occurs because large particles prevent the flow of other small particles since the particles cannot dissolve.

[0154] As can be confirmed in Fig. 4, the slurry of Example 1 showed no inflection point, and it was shown that the viscosity change when the shear rate increased and then decreased was also almost similar. Therefore, from such results, it can be seen that the slurry of Example 1 has excellent dispersibility.

[0155] On the other hand, the slurry of Comparative Example 1 showed an inflection point and showed irreversible behavior when the shear rate increased and then decreased. Such results mean that an aggregation phenomenon occurred in the slurry.

[0156] Generally, when the viscosity at a shear rate of 2.5 s -1 is 10 Pa·s or less, the slurry has excellent coating properties. Under such criteria, the slurry of Example 1 has a viscosity of 4.134 Pa·s at a shear rate of 2.5 s -1 and it is confirmed that the coating property is excellent. On the contrary, the slurry of Comparative Example 1 has a viscosity of 52.546 Pa·s at a shear rate of 2.5 s -1 and it was confirmed that the coating property is not good.

[0157] Example 2 and Comparative Examples 3 to 5: Manufacture of negative electrode Each negative electrode active material slurry produced in Example 1, Comparative Example 1, and 2 was coated on a SUS foil to a thickness of 10 μm and dried to produce Example 2 (using carbon black with an oxygen content of 5.2 at%), Comparative Example 3 (using carbon black with an oxygen content of 2.6 at%), Comparative Example 4 (using carbon black with an oxygen content of 1.3 at%), and Comparative Example 5 (using carbon black with an oxygen content of 2.4 at%) negative electrodes.

[0158] Experimental Example 3: Measurement of oxygen content in negative electrode active material layer The oxygen content contained in the negative electrode active material layer laminated on the negative electrodes produced in Example 2, Comparative Example 3, and Comparative Example 4 was analyzed by the following method, and the results are shown in Table 3, Fig. 7, and Fig. 8 below.

[0159] <Analysis method> (1) Analysis instrument Nexsa4 (Thermo Fisher Scientific), which is a photoelectron spectrometer (XPS or ESCA), was used.

[0160] (2) Analysis method First, the survey scan spectrum and narrow scan spectrum for each sample were obtained. For the narrow scan spectrum, four points were measured at each position, and the average and deviation were calculated. Next, the survey scan spectrum and narrow scan spectrum were obtained while progressing the depth profile. The depth profile was progressed up to 5000 seconds using monatomic Ar ions.

[0161] (3) Experiment and data processing conditions X-ray source: Monochromated Al Ka (1486.6 eV) X-ray spot size: 400 μm Sputtering gun: Monatomic Ar (energy: 1000 eV, current: Mid, raster width: 2.0 mm) Etching rate: 0.2 nm / s based on Ta2O5 (may vary depending on the sample) Operation mode: Constant Analyzer Energy (CAE) mode Survey scan pass energy: 200 eV, energy step: 1 eV Narrow scan: pass energy 50 eV, energy step 0.1 eV Charge compensation: flood gun off SF: Al THERMO1, ECF: TPP-2M, BG subtraction: Smart

[0162] <Analysis results> (1) Surface elemental composition ratio of the negative electrode active material layer The surface elemental composition ratio of the negative electrode active material layer was measured as shown in Table 3 below.

[0163] [Table 3]

[0164] From the results in Table 3 above, it can be seen that the oxygen content on the surface of the negative electrode active material layer is proportional to the oxygen content in the carbon material contained in the negative electrode active material layers manufactured in Example 2, Comparative Example 3, and Comparative Example 4. Figure 7 shows the 1s spectrum of carbon (C) contained in the negative electrode active material layers manufactured in Example 2, Comparative Example 3, and Comparative Example 4. According to Figure 7, it can be seen that the chemical state of carbon (C) is all similar in the negative electrode active material layers manufactured in Example 2, Comparative Example 3, and Comparative Example 4.

[0165] Figure 8 shows the result of peak deconvolution of the O 1s spectrum for oxygen contained in the negative electrode active material layers manufactured in Example 2, Comparative Example 3, and Comparative Example 4. From the spectrum, it can be confirmed that as the oxygen content in the carbon material constituting the negative electrode active material layer increases (Example 2 > Comparative Example 3 > Comparative Example 4), the Metal oxides peak becomes larger. The Metal oxides peak is considered to be due to the bonding of oxygen on the surface of the carbon material with Ag, which means that the higher the oxygen content on the surface of the carbon material, the better the dispersibility of Ag.

[0166] When the said Figure 8 is shown numerically, it is as shown in Table 4 below.

[0167]

Table 4

[0168] Experimental Example 4: Measurement of the surface roughness of the negative electrode active material layer The surface roughness of the negative electrode active material layer laminated on the negative electrodes manufactured in Example 2 and Comparative Example 5 was measured using a 3D confocal laser microscope device (manufactured by KEYENCE).

[0169] Specifically, the negative electrode for which roughness was to be measured was prepared in an appropriate size. At this time, in order to ensure the reliability of the data and confirm the roughness deviation within the sample, three or more samples were prepared for the same electrode. These samples were attached onto a slide glass using double-sided tape so as not to wrinkle.

[0170] After positioning the slide glass with the prepared sample attached thereon on the measurement stage, focusing was performed and the roughness was measured.

[0171] The SEM images of the negative electrode active material layer laminated on the negative electrodes manufactured in Example 2 and Comparative Example 5 are shown in Figure 9, and the measurement results of the said surface roughness are shown in Table 5 below and Figure 10.

[0172]

Table 5

[0173] Experimental Example 5: Analysis of the density and porosity of the negative electrode active material layer The density and porosity of the negative electrode active material layer laminated on the negative electrodes manufactured in Example 2 and Comparative Examples 3 to 5 were calculated and shown in Table 6 below.

[0174]

Table 6

[0175] Manufacture of All-Solid-State Lithium-Ion Secondary Batteries of Example 3 and Comparative Examples 6 to 7 As the positive electrode, a positive electrode in which a positive electrode active material is loaded on a current collector at 5 mAh / cm 2 was used. As the negative electrode, the negative electrodes manufactured in Example 2 and Comparative Examples 3 to 4 were used. As the electrolyte, a sulfide-based all-solid electrolyte (LPSCl composition) was used, and pouch-type monocells of Example 3, Comparative Example 6, and Comparative Example 7 were fabricated.

[0176] Experimental Example 6: Evaluation of Battery Characteristics The pouch-type monocells of Example 3, Comparative Example 6, and Comparative Example 7 were driven under the following charge and discharge conditions at an operating voltage range of 4.25 V - 3.0 V and a driving temperature of 60°C to evaluate the cycle characteristics, and the results are shown in Figures 5 and 6.

[0177] Charge condition: 0.33C, 4.25V CC / CV, 0.1C cut-off Discharge condition: 0.33C, 3.0V, CC

[0178] From Figure 5, it can be confirmed that in the case of the battery of Example 3, it can be driven without a significant decrease in cell capacity as the cycle progresses.

[0179] Also, from Figure 6, it can be confirmed that in the case of the battery of Example 3, the cycle characteristics are significantly superior to those of the batteries of Comparative Example 6 and Comparative Example 7.

Claims

1. A negative electrode comprising a current collector and a negative electrode active material layer, wherein the negative electrode active material layer comprises one or more active material layers containing 2 to 10 at% of oxygen.

2. The negative electrode according to claim 1, wherein the one or more active material layers further comprise 65 to 85 at% of carbon and 0.5 to 5 at% of a metal element.

3. The negative electrode according to claim 2, wherein the one or more active material layers comprise carbon material particles and metal particles.

4. The negative electrode according to claim 3, wherein the carbon material particles are amorphous carbon material particles.

5. The negative electrode according to claim 3, wherein the carbon material particles contain 3 to 10 at% of oxygen.

6. The negative electrode according to claim 5, wherein the oxygen exists in a form contained in a functional group bonded to the carbon material particles.

7. The negative electrode according to claim 6, wherein the functional group comprises one or more selected from the group consisting of a carboxyl group, a hydroxyl group, an ether group, an ester group, an aldehyde group, a carbonyl group, and an amide group.

8. The negative electrode according to claim 3, wherein the metal particles are particles that form an alloy with lithium.

9. The negative electrode according to claim 8, wherein the metal particles are one or more particles selected from silver (Ag), gold, platinum, palladium, silicon, aluminum, bismuth, tin, indium, and zinc.

10. The negative electrode according to claim 9, wherein the metal particles contain silver (Ag).

11. The negative electrode according to claim 1, wherein the one or more active material layers have the following surface roughness: 0.01 μm ≤ Sa ≤ 0.3 μm 0.5 μm ≤ Sz ≤ 5 μm 500 mm －１≦ Spc ≤ 1500 mm －１ 0.005 ≤ Sdr ≤ 0.15

12. The negative electrode according to claim 1, wherein the one or more active material layers have a porosity of 55 to 70%.

13. The negative electrode according to claim 3, wherein the carbon material particles and the metal particles are contained in the form of a carbon material-metal composite.

14. The negative electrode according to claim 13, wherein the particle size (D50) of the carbon material-metal composite is 0.1 μm to 0.5 μm.

15. The negative electrode according to claim 14, wherein the maximum particle size of the carbon material-metal composite is 3 μm or less.

16. A lithium-ion secondary battery comprising the negative electrode according to claim 1; a positive electrode; and an electrolyte interposed between the negative electrode and the positive electrode.

17. The lithium-ion secondary battery according to claim 16, wherein the electrolyte contains a sulfide-based solid electrolyte.

18. The lithium-ion secondary battery according to claim 17, wherein the lithium-ion secondary battery is an anode-less battery.

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