All-solid-state lithium ion secondary battery

Abstract

Provided is an all-solid-state lithium ion secondary battery including a positive electrode, a negative electrode, and a solid electrolyte interposed between the positive electrode and the negative electrode, in which the negative electrode includes a negative electrode current collector and a negative electrode active material layer, and in which the negative electrode active material layer includes a carbon material and Ag, and includes two or more layers.

Description

Technical Field

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2022-0144772 filed on November 2, 2022 and Korean Patent Application No. 10-2023-0148468 filed on October 31, 2023, the entire contents of which are incorporated herein by reference.

[0002] The invention relates to an all-solid-state lithium-ion secondary battery. Background Art

[0003] Recently, all-solid-state secondary batteries using solid electrolytes as electrolytes have attracted much attention. In order to increase 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 (capacity per unit weight) of lithium is about 10 times that of graphite, which is commonly used as a negative electrode active material. Therefore, if lithium is used as a negative electrode active material, the output can be increased while making the all-solid-state secondary battery thinner.

[0004] As an all-solid-state lithium-ion secondary battery, for example, it is known to provide a metal layer formed of a metal that forms an alloy with lithium as a negative electrode active material layer, and to provide an interface layer made of amorphous carbon on the negative electrode active material layer. In the case of such an all-solid-state lithium-ion secondary battery, when charging, metallic lithium is precipitated between the amorphous carbon interface layer and the negative electrode active material layer, and when discharging, the corresponding metallic lithium is ionized and moves to the positive electrode.

[0005] However, when the all-solid-state lithium-ion secondary battery as described above is repeatedly charged and discharged, the metallic lithium precipitated between the amorphous carbon interface layer and the negative electrode active material layer may be ionized and dissolved, resulting in voids, thereby making it impossible to use it as a battery. Therefore, when such an all-solid-state lithium-ion secondary battery is actually used, in order to prevent the formation of voids due to charging and discharging, it is necessary to insert end plates on both sides of the positive electrode collector and the negative electrode collector to apply high external pressure. However, the presence of the end plates that apply external pressure may become an obstacle to the thinning of the all-solid-state lithium-ion secondary battery.

[0006] Therefore, development of all-solid-state lithium-ion secondary batteries that do not require high external pressure and have excellent discharge capacity is being actively pursued.

[0007] [Prior art literature]

[0008] [Patent Document]

[0009] Korean Patent Publication No.10-2015-0064697 Summary of the invention

[0010] [Technical issues]

[0011] The present invention is designed to solve the above-mentioned problems of the prior art, and an object of the present invention is to provide an all-solid-state lithium-ion secondary battery which does not require application of high external pressure, suppresses the formation of dendrites and has excellent discharge capacity and life characteristics.

[0012] [Technical solution]

[0013] In order to achieve the above object, the present invention provides an all-solid-state lithium-ion secondary battery, comprising:

[0014] A positive electrode, a negative electrode, and a solid electrolyte between the positive electrode and the negative electrode,

[0015] Wherein, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer, and

[0016] The negative electrode active material layer contains a carbon material and Ag, and includes two or more layers.

[0017] [Beneficial Effects]

[0018] The all-solid-state lithium-ion secondary battery of the present invention suppresses the formation of dendrites without applying high external pressure and provides excellent discharge capacity and life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figures 1 to 4 It is a cross-sectional view schematically showing the structure of the all-solid-state lithium-ion secondary battery of the present invention.

[0020] Figure 5 : is a graph showing the measurement results of the cycle characteristics of the all-solid-state lithium ion secondary batteries of Example 7 of the present invention and Comparative Example 2.

[0021] Figure 6 A SEM image of the negative electrode of Example 6 of the present invention is shown.

[0022] Figure 7 This is a graph showing the particle size distribution of the carbon material-metal composite of the present invention. DETAILED DESCRIPTION

[0023] Hereinafter, the present invention will be described in more detail to help understanding of the present invention.

[0024] The terms and words used in this specification and claims should not be interpreted as limited to general or dictionary terms, but should be interpreted based on the principle that the inventor can appropriately define the concept of the term to describe his invention in the best possible way with the meaning and concept consistent with the technical idea of ​​the present invention. In addition, the terms used herein are only used to describe exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless the context clearly dictates otherwise.

[0025] When it is mentioned that a certain component is "connected, provided or arranged" to another component, it should be understood that it can be directly connected or arranged to another component, but other components may also exist therebetween. On the other hand, when it is mentioned that a certain component is "directly connected or arranged" to another component, it should be understood that no other components exist therebetween. At the same time, other expressions describing the relationship between components, such as "on top" and "directly on top" or "between" and "immediately between" or "adjacent to" and "directly adjacent to", etc., should also be interpreted similarly.

[0026] As used herein, the term "combination" includes mixtures, alloys, reaction products, etc. unless otherwise specifically stated. As used herein, the terms "first" and "second" and the like do not denote order, quantity, or importance, but are used to distinguish one element from another.

[0027] like Figure 1 As shown, the all-solid-state lithium-ion secondary battery 100 of the present invention includes a positive electrode 10, a negative electrode 20, and a solid electrolyte 30 between the positive electrode and the negative electrode.

[0028] The negative electrode includes a current collector 22 and a negative electrode active material layer 24, and

[0029] The negative electrode active material layer 24 contains a carbon material and Ag, and includes two or more layers.

[0030] In one embodiment of the present invention, it is characterized in that the two or more layers include two layers containing a carbon material and Ag, and the two layers include different Ag contents.

[0031] In one embodiment of the present invention, of the two layers containing the carbon material and Ag, the layer disposed adjacent to the negative electrode current collector 22 (eg, Figure 1 , 24a) may be characterized in that the layer disposed adjacent to the solid electrolyte 30 (e.g., Figure 1 , 24b) a higher Ag content ratio. All-solid-state batteries with this structure can provide better discharge capacity and life characteristics.

[0032] Specifically, the layer disposed adjacent to the negative electrode current collector may contain 1.5 to 10 times, preferably 2 to 8 times, 2 to 4 times, or 2 to 3 times more Ag than the layer disposed adjacent to the solid electrolyte.

[0033] The layer disposed adjacent to the negative electrode current collector may contain 20 to 80 wt%, 20 to 60 wt%, or 25 to 55 wt% Ag based on 100 wt% of the total negative electrode active material, and may contain 20 to 80 wt% or 40 to 80 wt% of the carbon material based on 100 wt% of the total negative electrode active material.

[0034] In addition, the negative electrode active material layer disposed adjacent to the negative electrode current collector may further include a binder. In this case, it may include 20 to 75 wt % of Ag, 20 to 75 wt % of carbon material, and 1 to 10 wt % of binder, and may also include 25 to 55 wt % of Ag, 40 to 73 wt % of carbon material, and 1 to 10 wt % of binder.

[0035] The layer disposed adjacent to the solid electrolyte may contain 10 to 60 wt%, 15 to 40 wt%, or 15 to 30 wt% of Ag based on a total of 100 wt% of the negative electrode active material, and may contain 40 to 90 wt%, 60 to 85 wt%, or 70 to 85 wt% of the carbon material based on a total of 100 wt% of the negative electrode active material.

[0036] In addition, the negative electrode active material layer disposed adjacent to the solid electrolyte may further include a binder. In this case, it may include 10 to 55 wt % of Ag, 40 to 85 wt % of carbon material, and 1 to 10 wt % of binder, and may also include 15 to 30 wt % of Ag, 65 to 83 wt % of carbon material, and 1 to 10 wt % of binder.

[0037] In one embodiment of the present invention, the two layers including the carbon material and Ag may each independently have a thickness of 1 μm to 50 μm.

[0038] In one embodiment of the present invention, Figure 2 or Figure 3 As shown, the all-solid-state lithium-ion secondary battery of the present invention may further include a layer 24c containing 0 to 5 wt % or 0 to 2 wt % of Ag based on a total of 100 wt % of the negative electrode active material in addition to two layers 24a and 24b of carbon material and Ag. The layer may further include 95 to 100 wt % or 98 to 100 wt % of carbon material. In addition, if the layer includes a binder, it may include 0 to 5 wt % of Ag, 90 to 99 wt % of carbon material and 1 to 10 wt % of binder, and may include 0 to 2 wt % of Ag, 90 to 99 wt % of carbon material and 1 to 10 wt % of binder.

[0039] In one embodiment of the present invention, it may be preferred that a layer containing 0 to 5 wt % of Ag and a carbon material is formed as a layer without Ag. In addition, the layer may further contain a binder. In this case, it may contain 90 to 99 wt % of a carbon material and 1 to 10 wt % of a binder.

[0040] In one embodiment of the present invention, Figure 3As shown, a layer 24c containing 0 to 5 wt% of Ag and a carbon material is disposed between two layers 24a and 24b containing a carbon material and Ag, or as shown in FIG. Figure 2 As shown, it may be disposed between the layer 24 b adjacent to the solid electrolyte and the solid electrolyte 30 of the two layers.

[0041] In one embodiment of the present invention, it may be preferred that the layer 24c containing 0 to 5 wt% of Ag and carbon material is disposed between the layer 24b adjacent to the solid electrolyte of the two layers and the solid electrolyte 30, such as Figure 2 shown.

[0042] In one embodiment of the present invention, the layer 24c containing 0 to 5 wt% of Ag and the carbon material may have a thickness of 1 μm to 30 μm.

[0043] In one embodiment of the present invention, the negative electrode active material layer of the present invention may further include a layer containing 80 to 100 weight %, 90 to 100 weight % or 95 to 100 weight % of Ag based on a total of 100 weight % of the negative electrode active material in addition to two layers of carbon material and Ag. The layer may further include 0 to 20 weight %, 0 to 10 weight % or 0 to 5 weight % of carbon material. In addition, the layer may further include a binder. In this case, it may include 80 to 99 weight % of Ag, 0 to 19 weight % of carbon material and 1 to 10 weight % of binder, may include 90 to 99 weight % of Ag, 0 to 9 weight % of carbon material and 1 to 10 weight % of binder, and may also include 95 to 99 weight % of Ag, 0 to 4 weight % of carbon material and 1 to 10 weight % of binder.

[0044] In one embodiment of the present invention, a layer containing 80 to 100 wt % of Ag may be disposed between the layer adjacent to the negative electrode collector and the negative electrode collector of the two layers.

[0045] In one embodiment of the present invention, the layer containing 80 to 100 wt % of Ag may have a thickness of 1 μm to 30 μm.

[0046] In one embodiment of the present invention, the two or more layers may include one layer containing a carbon material and Ag and one layer containing 0 to 5 wt % of Ag and a carbon material.

[0047] In this case, a layer containing carbon material and Ag can be relatively located on one side of the current collector, and a layer containing 0 to 5 weight % of Ag and carbon material can be relatively located on one side of the solid electrolyte. Here, a layer containing 0 to 5 weight % of Ag and carbon material is the same as described above.

[0048] In one embodiment of the present invention, the carbon material particles contained in one or more layers of the negative electrode active material layer may be, for example, amorphous carbon material particles. However, the carbon material particles are not limited to amorphous particles. Specific examples of amorphous carbon materials may be carbon black such as acetylene black, furnace black and Ketjen black, graphene or a combination thereof.

[0049] If the amorphous carbon material particles contain pores, the size of the pores may be 1 nm or less, preferably 0.5 nm or less. However, it may be more preferred that the amorphous carbon material particles do not contain pores. This is because, if the amorphous carbon material particles contain pores, lithium may precipitate inside the pores, such lithium may be deactivated, and the amount of lithium thus deactivated may increase with repeated charging and discharging.

[0050] The pore size in the amorphous carbon material particles can be measured, for example, by nitrogen adsorption experiments or by transmission electron microscopy.

[0051] The carbon material particles may be carbon material particles containing 3 to 10 atomic % of oxygen. If the oxygen content is within the above range, the surface roughness of the negative electrode active material layer can be significantly improved, which is desirable because the operating characteristics of the battery are also improved. In particular, in the case of a layer containing Ag, it is preferred to contain carbon material particles containing 3 to 10 atomic % of oxygen.

[0052] In one embodiment of the present invention, oxygen may be present in the form of being contained in a functional group bonded to the carbon material particle. In addition, the functional group may include 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.

[0053] Carbon material particles having an oxygen content of 3 to 10 atomic % can be produced by, for example, a method of oxidizing a carbon material. Specifically, oxygen functional groups can be introduced into the surface of the carbon material by treating the carbon material with an acid and reacting it at a temperature of 25° C. to 60° C. while stirring. The type of acid is not particularly limited, and any acid capable of introducing oxygen functional groups into the surface of the carbon material can be used. The acid can include, for example, sulfuric acid, nitric acid, or a mixture thereof, and an oxidizing agent such as potassium permanganate can be used.

[0054] The oxygen content contained in the carbon material can be measured using a photoelectron spectrometer (XPS or ESCA). For example, the oxygen content contained in the carbon material can be measured using a K-Alpha (Thermo Fisher Scientific) device.

[0055] In one embodiment of the present invention, oxygen may exist on the surface of the carbon material particles. The surface refers not only to the outer surface of the carbon material particles but also includes the surface of pores when pores exist.

[0056] In one embodiment of the present invention, each negative electrode active material layer may further contain particles of one or more selected from the group consisting of gold, platinum, palladium, silicon, aluminum, bismuth, tin, indium and zinc in addition to Ag particles.

[0057] In one embodiment of the present invention, the carbon material particles may have a particle size (D50) of 10nm to 100nm or 20nm to 60nm, and the Ag particles and other metal particles may have a particle size (D50) of 20nm to 100nm, 20nm to 60nm, or 30nm to 60nm.

[0058] In one embodiment of the present invention, one or more layers included in the negative electrode active material layer may contain 2 to 10 atomic % of oxygen. If the oxygen content is within the above range, the surface roughness of the corresponding layer is significantly improved, which is desirable because the operating characteristics of the battery can be improved.

[0059] Among the layers included in the negative electrode active material layer, any one or more layers containing carbon material and Ag may further contain 65 to 85 atomic % of carbon and 0.5 to 5 atomic % of Ag and oxygen, and more preferably may further contain 74 to 85 atomic % of carbon and 0.5 to 3 atomic % of Ag.

[0060] Any one or more of the above-mentioned layers may further contain 5 to 25 atomic % of fluorine (F), and more preferably may further contain 10 to 20 atomic % of fluorine (F).

[0061] Any one or more of the above-mentioned layers may further contain 0.01 to 1 atomic % of sulfur (S), and more preferably may further contain 0.01 to 0.5 atomic % of sulfur (S).

[0062] In one embodiment of the present invention, any one or more of the above layers may contain 2 to 10 atomic % of oxygen, 65 to 85 atomic % of carbon, 0.5 to 5 atomic % of Ag, and 5 to 25 atomic % of fluorine (F).

[0063] In addition, it may more preferably contain 2.5 to 5 atomic % of oxygen, 74 to 85 atomic % of carbon, 0.5 to 3 atomic % of Ag, and 10 to 20 atomic % of fluorine (F).

[0064] Furthermore, sulfur (S) may be further contained in addition to the above components.

[0065] In the above, the atomic composition ratio can be measured using photoelectron spectroscopy (XPS or ESCA). For example, the composition ratio can be measured using a Nexsa4 (Thermo Fisher Scientific) device.

[0066] In one embodiment of the present invention, any one or more of the above layers included in the negative electrode active material layer may have the following surface roughness characteristics:

[0067] 0.01μm≤Sa≤0.3μm

[0068] 0.5μm≤Sz≤5μm

[0069] 500mm -1 ≤Spc≤1500mm -1

[0070] 0.005≤Sdr≤0.15.

[0071] If the surface roughness satisfies the above range, the overall characteristics of the battery can be improved, and in particular, the life characteristics can be improved. Specifically, if the surface roughness of the negative electrode active material layer exceeds the above range, the contact with the electrolyte layer in the direction toward the electrolyte is insufficient and is not conducive to the uniform precipitation of lithium in the direction toward the negative electrode current collector, so the characteristics of the battery may be deteriorated.

[0072] In the above, the surface roughness of the negative electrode active material layer can be measured using a microscope device. For example, the surface roughness can be measured using a 3D laser confocal microscope (manufactured by KEYENCE Corporation) device.

[0073] In the above, Sa (arithmetic mean height of the 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 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. In addition, 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 to a range of a combination of a maximum value and a minimum value. Sa represents the average value of the absolute value of the height difference between each point relative to the average surface of the surface.

[0074] In the above, Sz (maximum height roughness of the profile) may 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 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. In addition, Sz may more preferably be in the range of 0.5 μm ≤ Sz ≤ 1.6 μm, but is not limited to these ranges, and may be set to a range of a combination of a maximum value and a minimum value. Sz represents the maximum height roughness in a single plane, that is, the distance between the highest point and the lowest point in a single plane.

[0075] In the above, Spc (roughness expressed in peaks) can be up to 1500 mm -1 Below, 1400mm -1 Below, 1300mm -1 Below, 1200mm -1 Below, 1100mm -1 Below, or 1000mm -1 Below, and at least 500mm -1 Above, 600mm -1 Above, 700mm -1 Above, 800mm -1 Above, or 900mm -1 In addition, Spc can be more preferably 500mm -1 ≤Spc≤1100mm -1 The range of is within, but not limited to, these ranges, and can be set to a range of a combination of a maximum value and a minimum value. Spc is a measure of roughness expressed in terms of the number of peaks, that is, a measure of peak steepness.

[0076] 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 at least 0.005 or more, 0.01 or more, or 0.015 or more. In addition, Sdr can more preferably be in the range of 0.005≤Sa≤0.03, but is not limited to these ranges, and can be set to a range of a combination of a maximum value and a minimum value. Sdr refers to the degree of increase in interface area, that is, the area ratio increased relative to the area of ​​the measurement area when the expansion area (surface area of ​​the measurement shape) is observed vertically.

[0077] In the above, the meanings of Sa, Sz, Spc, and Sdr are described, but they are the same as those commonly used in the art.

[0078] In one embodiment of the present invention, the carbon material particles and the Ag particles contained in any one or more layers of the negative electrode active material layer may be contained in the form of a carbon material-metal composite.

[0079] In the present invention, the negative electrode active material layer is formed into a very thin film with a micro thickness and can be manufactured in the form of a carbon material-Ag composite containing carbon material particles and Ag. However, conventional carbon material-Ag composites have the problem that carbon material particles and Ag particles are difficult to be uniformly distributed.

[0080] In addition, conventional carbon material-Ag composites have a problem that it is very difficult to form a composite with a small particle size. That is, if the particle size of the carbon material-Ag composite is too large compared to a thin film with a micro thickness, it is difficult to form a negative electrode active material layer with excellent surface roughness and thus the operating characteristics of the battery are also reduced, so it is very important to prepare a carbon material-Ag composite with a small particle size.

[0081] The present invention provides the effect of significantly improving the above-mentioned problems of the prior art.

[0082] That is, the carbon material-Ag composite forms a carbon material-Ag composite having a significantly smaller particle size than when a conventional carbon material is used. The carbon material forming the composite contains more than 3 atomic % of oxygen, and thus is fully mixed with the metal particles and has the characteristic of being uniformly distributed with the Ag particles. Therefore, a carbon material-Ag composite having excellent component uniformity can be prepared. In addition, due to the above reasons, a carbon material-Ag composite having a small and uniform particle size can be prepared.

[0083] In one embodiment of the present invention, the carbon material-Ag composite may be composed of one or more bonds selected from the group consisting of chemical bonds between carbon material particles and Ag particles, van der Waals bonds between carbon material particles and Ag particles, and bonds between carbon material particles and Ag particles via a binder. The chemical bond may be an Ag-O bond between Ag particles and oxygen contained in the carbon material.

[0084] In one embodiment of the present invention, carbon material particles having a particle size (D50) of 10nm to 100nm or 20nm to 60nm may be used, and Ag particles having a particle size (D50) of 20nm to 100nm, 20nm to 60nm, or 30nm to 60nm may be used.

[0085] In one embodiment of the present invention, the particle size (D50) of the carbon material-Ag composite may be 0.1 μm to 0.5 μm. The upper limit of the particle size may be 0.4 μm or 0.3 μm.

[0086] In addition, the maximum particle size of the carbon material-Ag composite may be 3 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less.

[0087] If the particle size of the carbon material-Ag composite is too large compared to a thin film with a micro thickness, it is difficult to form a negative electrode active material layer with excellent surface roughness and thus the operating characteristics of the battery are also reduced, so it is very important to prepare a carbon material-Ag composite with a small particle size.

[0088] The reason why the operating characteristics of the battery are deteriorated is that if the surface roughness of the negative electrode active material layer is large, the contact with the electrolyte layer is insufficient and it is not conducive to the uniform precipitation of lithium into the negative electrode current collector.

[0089] In an anode-free lithium ion secondary battery, the thickness of the negative electrode active material layer may generally be formed in the range of 1 μm to 100 μm or 10 μm to 60 μm, specifically 10 μm, 20 μm, 30 μm, 40 μm or 50 μm, etc.

[0090] For example, if a carbon material-Ag composite having a particle size of 10 μm is used to form a negative electrode active material layer having a thickness of 20 μm, it is apparently difficult to form a desired surface roughness.

[0091] If the maximum particle size of the carbon material-metal composite is 3 μm or less, the effect of improving the surface roughness can be more reliably obtained, so it is preferred. On the other hand, when the maximum particle size exceeds 3 μm, it may be difficult to obtain excellent surface roughness when forming a thin film. Therefore, the maximum particle size of the carbon material-Ag composite may be 3 μm or less, 2 μm or less, 1.5 μm or less, and 1 μm or less.

[0092] The particle size of the carbon material-Ag composite can be measured using a particle size analyzer, for example, Mastersizer 3000 (Malvem panalytical) instrument.

[0093] In one embodiment of the present invention, the positive electrode may include a positive electrode current collector and a positive electrode active material layer.

[0094] In one embodiment of the present invention, the solid electrolyte may be a sulfide-based solid electrolyte.

[0095] Hereinafter, embodiments of the present invention will be described in more detail.

[0096] <Composition of all-solid-state lithium-ion secondary battery>

[0097] Figure 1 A cross-sectional view schematically showing a schematic configuration of an all-solid-state lithium-ion secondary battery according to an embodiment of the present invention is shown.

[0098] The all-solid-state lithium-ion secondary battery 100 according to the embodiment of the present invention is a so-called lithium-ion secondary battery that is charged and discharged by moving lithium ions between the positive electrode 10 and the negative electrode 20. Specifically, the 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 provided between the positive electrode 10 and the negative electrode 20. Figure 1 shown.

[0099] (1) Positive electrode

[0100] like Figure 1As shown, the positive electrode 10 includes a positive electrode current collector 12 and a positive electrode active material layer 14 which are sequentially disposed toward the negative electrode 20 .

[0101] The positive electrode current collector 12 may be in the form of a plate or foil. The positive electrode current collector 12 may be, for example, a metal selected from indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium and lithium, or an alloy of two or more of these metals.

[0102] The positive electrode active material layer 14 may reversibly intercalate and deintercalate lithium ions. The positive electrode active material layer 14 may include a positive electrode active material and a solid electrolyte.

[0103] The positive electrode active material may be a compound capable of intercalating / deintercalating lithium. Examples of the compound capable of intercalating / deintercalating lithium may be a compound represented by any one of the following formulae: Li a A 1-b B' b D'2 (where 0.90≤a≤1.8 and 0≤b≤0.5); Li a E 1-b B' b O 2-c D' c (where 0.90≤a≤1.8, 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≤1.8, 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 (where 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 (where 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(where 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 (where 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 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NeG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1); Li a MnG b O2 (where 0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn b O4 (where 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 )Fe2(PO4)3(0≤f≤2); LiFePO4.

[0104] In the above 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.

[0105] Specific examples of the positive electrode active material may be lithium salts, such as lithium cobalt oxide (hereinafter referred to as LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (hereinafter referred to as NCA), and lithium nickel cobalt manganese oxide (hereinafter referred to as NCM), lithium manganese oxide, lithium iron phosphate, and lithium sulfide. The positive electrode active material layer 14 may contain only one selected from these compounds or may contain two or more as the positive electrode active material.

[0106] The positive electrode active material may contain a lithium salt of a transition metal oxide having a layered rock salt structure among the above 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, resulting in each atomic layer forming a two-dimensional plane. In addition, the "cubic rock salt structure" refers to the sodium chloride type structure, which is one of the crystal structures. For example, the "cubic rock salt structure" refers to a structure in which face-centered cubic lattices formed by positive ions and negative ions are offset by 1 / 2 of the edge of the unit lattice from each other.

[0107] The lithium salt of the transition metal oxide having such a layered rock salt structure may be, for example, a ternary lithium transition metal oxide, such as 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, and x + y + z = 1). The positive electrode active material layer 14 can improve the energy density and thermal stability of the all-solid-state lithium-ion secondary battery 100 by containing a lithium salt of a ternary transition metal oxide having such a layered rock salt structure as the positive electrode active material.

[0108] Here, the shape of the positive electrode active material may be, for example, a particulate shape, such as a true spherical shape or an elliptical spherical shape. In addition, the particle size of the positive electrode active material is not particularly limited and may be within the range applicable to the positive electrode active material of a typical all-solid-state lithium-ion secondary battery. In addition, the content of the positive electrode active material in the positive electrode active material layer 14 is also not particularly limited as long as it is within the range applicable to the positive electrode of a typical all-solid-state lithium-ion secondary battery.

[0109] Of course, a material having a coating on the surface of the compound can be used, or a mixture of the compound and a compound having a coating can also be used. The coating can include a coating element compound of an oxide or hydroxide of a coating element, an oxyhydroxide of a coating element, an oxycarbonate of a coating element, or a hydroxycarbonate of a coating element. The compounds constituting these coatings can be amorphous or crystalline. The coating element contained in the coating can be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating formation process can use any coating method (e.g., spraying, dipping, etc.), as long as it can be coated by using these elements in the compound without adversely affecting the performance of the positive active material, and because it can be well understood by those skilled in the art, its detailed description will be omitted.

[0110] A specific example of the coating layer may be Li2O-ZrO2.

[0111] The solid electrolyte contained in the positive electrode active material layer 14 may also be the same as or different from the solid electrolyte contained in the solid electrolyte layer 30 described later.

[0112] In addition, the positive electrode active material layer 14 may be a layer obtained by appropriately mixing additives such as a conductive agent, a binder (binder), a filler, a dispersant, or an ion conduction aid with the above-mentioned positive electrode active material and a solid electrolyte.

[0113] Conductive agent can be, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber or metal powder. In addition, binder (adhesive) can be, for example, styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride or polyethylene. In addition, filler, dispersant or ion conductive aid etc. can be known materials commonly used in electrodes of all-solid-state lithium ion secondary batteries.

[0114] (2) Negative electrode

[0115] The negative electrode 20 may include a negative electrode current collector 22 and a negative electrode active material layer 24 sequentially disposed toward the positive electrode 10 .

[0116] The negative electrode current collector 22 may be in the form of a plate or foil. The negative electrode current collector 22 may include a material that does not react with lithium, i.e., does not form any of an alloy or a compound with lithium. The material constituting the negative electrode current collector 22 may be, for example, copper, stainless steel, titanium, iron, cobalt, and nickel. The negative electrode current collector 22 may be composed of one of these metals, or may be composed of an alloy or a coating (coating) material of two or more of these metals.

[0117] The negative electrode active material layer 24 may include one or more negative electrode active materials that can form an alloy or compound with lithium. In the initial state or in the state after full discharge, lithium may not be contained in the negative electrode current collector 22, in the negative electrode active material layer 24, or between the negative electrode active material layer 24 and the solid electrolyte layer 30. As described later, if the all-solid-state lithium ion secondary battery 100 according to the embodiment is overcharged, the negative electrode active material contained in the negative electrode active material layer 24 and the lithium ions moved from the positive electrode 10 form an alloy or compound, and a metal layer 26 containing lithium as a main component may be formed (precipitated) on the negative electrode 20, such as Figure 4 The metal layer 26 may be precipitated and disposed between the negative electrode current collector 22 and the negative electrode active material layer 24 and / or in the negative electrode active material layer 24. The metal layer 26 containing lithium as a main component between the negative electrode current collector 22 and the negative electrode active material layer 24 may be disposed closer to the negative electrode current collector 22 than the negative electrode active material layer 24.

[0118] The negative electrode active material layer 24 according to the embodiment may include Ag as an essential negative electrode active material. Therefore, the metal layer 26 formed during overcharge may include a Li(Ag) alloy including a γ1 phase, a βLi phase, or a combination thereof in which Ag is solid-dissolved in lithium. Therefore, during discharge, only Li is dissolved in the Li(Ag) alloy constituting the metal layer 26, and solid-dissolved Ag remains, thereby suppressing the generation of voids. In this case, the content of Ag in the precipitated Li-Ag solid solution may be 60 wt % or less. If the content is within this range, the reduction 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 is reduced, and the generation of voids may not be fully suppressed. To this end, the content of Ag in the precipitated Li-Ag solid solution may be 20 wt % or more, for example, 40 wt % or more.

[0119] The fact that the metal layer 26 contains at least one Li-Ag solid solution of the γ1 phase or the βLi phase can be confirmed, for example, by analyzing the peak position and the peak intensity ratio through XRD measurement. In addition, the Ag content in the precipitated Li-Ag solid solution can be measured, for example, by XRD measurement. In this case, the diffraction peak position of pure metallic lithium is different from the diffraction peak position of metallic lithium (Li-Ag solid solution) solid-dissolved with Ag. As the solid solution concentration of Ag decreases, the diffraction peak position of metallic lithium solid-dissolved with Ag approaches the diffraction peak position of pure metallic lithium. For example, when using a Cu target for XRD measurement, if the solid solution concentration of Ag decreases, the diffraction peak moves from about 2θ=37.0° to about 36.5°. The solid solution amount of Ag can be inferred based on the peak position. In addition, the solid solution amount can be measured using ICP or the like.

[0120] In one embodiment, Ag does not necessarily exist uniformly in the negative electrode active material layer 24, but may be localized on one side of the negative electrode current collector 22 in the negative electrode active material layer 24. In this case, lithium ions may react with the localized layer of Ag in the negative electrode active material layer 24 that reaches the vicinity of the negative electrode current collector 22, and thus a Li(Ag) alloy may be formed as the metal layer 26.

[0121] If the content of Ag contained in the negative electrode active material layer 24 is too small, the Ag remaining during discharge also decreases, so the generation of voids may not be suppressed. For this reason, in an initial state where charging and discharging are not performed, the content of Ag in the negative electrode active material layer 24 is 10 wt % or more, for example, 20 wt % or more, based on 100 wt % of the total negative electrode active material contained in the negative electrode active material layer.

[0122] Meanwhile, the upper limit of the Ag content in the negative electrode active material contained in the negative electrode active material layer 24 may be 100 wt %. However, in the relationship between the reaction potentials of Ag and Li, if Ag increases, the average discharge potential may decrease, and thus the energy density of the battery may also decrease. Therefore, from the viewpoint of high energy densification, the Ag content may be 80 wt % or less, for example, 50 wt % or less.

[0123] The Ag content (wt%) in the negative electrode active material layer 24 can be measured, for example, as follows. That is, the all-solid-state lithium ion secondary battery 100 is discharged, then disassembled, and the negative electrode active material layer 24 is recovered from the surface of the negative electrode 20. Then, the Ag content in the recovered product can be measured using EDX, XRF or ICP. In addition, for example, the Ag content can be determined by SEM-EDS analysis in the cross-sectional direction.

[0124] In addition, in the negative electrode active material layer 24, when viewed from the stacking direction of the negative electrode 20, if the Ag content per unit area is too low, the Ag remaining during discharge also decreases, so there is a risk that the generation of voids may not be suppressed. Therefore, the Ag content per unit area in the negative electrode active material layer 24 may be 0.05 mg / cm 2 Above, for example 0.10 mg / cm 2 above.

[0125] At the same time, if the Ag content per unit area is too high, there is a risk that the average discharge potential will decrease and thus the energy density of the battery will decrease. Therefore, the Ag content per unit area can be 5.0 mg / cm 2 Below, for example 2.0 mg / cm 2 the following.

[0126] The Ag content per unit area of ​​the negative electrode active material layer 24 can be measured, for example, as follows. That is, the all-solid-state lithium ion secondary battery 100 is discharged and then disassembled, and the Ag content can be determined by composition analysis of SEM-EDS on the surface or cross-sectional direction of the negative electrode 20. Without being limited thereto, the Ag content can also be determined using XPS, ICP, etc.

[0127] In addition, in the initial state where charging and discharging are not performed, Ag contained in the negative electrode active material layer 24 may be in the form of particles or films. When present in the form of particles, the average particle size (d50) (diameter length or average diameter) of Ag may be 20 nm to 1 μm, but is not limited thereto.

[0128] The negative electrode active material layer 24 may further contain, for example, one or more selected from amorphous carbon, Au, Pt, Pd, Si, Al, Bi, Sn, In, and Zn as an optional negative electrode active material other than Ag.

[0129] The carbon material contained in the negative electrode active material layer 24 may preferably be amorphous carbon. Specific examples of the amorphous carbon may be carbon black such as acetylene black, furnace black, and Ketjen black, graphene, or a combination thereof.

[0130] The sum of negative electrode active materials other than Ag may be 50 wt % or more, for example 70 wt % or more, based on 100 wt % of the total negative electrode active materials contained in the negative electrode active material layer 24. The content of negative electrode active materials other than Ag may be measured in the same manner as the Ag content.

[0131] The negative electrode active material layer 24 may further include a binder. The negative electrode active material layer 24 may be stabilized on the negative electrode current collector 22 by including a binder. The material constituting the binder may be, for example, a resin material such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. The binder may be composed of one or more selected from these resin materials.

[0132] In addition, the negative electrode active material layer 24 may be in a state where additives used in conventional all-solid lithium ion secondary batteries (eg, fillers, dispersants, ion conductive agents, etc.) are appropriately blended. Specific examples of the additives are the same as those described in the positive electrode above.

[0133] The total thickness of the negative electrode active material layer 24 is not particularly limited, but may be 1 μm to 100 μm, or 10 μm to 60 μm. If 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. If 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 thus the performance of the all-solid-state secondary battery may not be sufficiently improved. If the above-mentioned binder is used, the thickness of the negative electrode active material layer 24 can be easily ensured at an appropriate level.

[0134] On the other hand, a film containing a material capable of forming an alloy or a compound with lithium is further included on the negative electrode collector 22 , and the film may be provided between the negative electrode collector 22 and the negative electrode active material layer.

[0135] The negative electrode current collector 22 does not react with lithium metal, but it may be difficult to deposit a smooth lithium metal layer thereon. The film may also serve as a wetting layer to allow lithium metal to be deposited evenly on the negative electrode current collector 22 .

[0136] The material used in the film that can form an alloy with lithium metal may include silicon, magnesium, aluminum, lead, silver, tin or a combination thereof. The material used in the film that can form a compound with lithium metal may include carbon, titanium sulfide, iron sulfide or a combination thereof. Within the limit of not affecting the electrochemical properties of the electrode and / or the redox potential of the electrode, the content of the material used in the film may be small. The film can be applied flatly on the negative electrode current collector 22 to prevent cracks from occurring during the charging cycle of the all-solid-state lithium-ion secondary battery 100. The film can be applied by methods such as physical vapor deposition (e.g., evaporation or sputtering), chemical vapor deposition or plating methods.

[0137] The thickness of the film may be 1 nm to 500 nm. The thickness of the film may be, for example, 2 nm to 400 nm. The thickness of the film may be, for example, 3 nm to 300 nm. The thickness of the film may be, for example, 4 nm to 200 nm. The thickness of the film may be, for example, 5 nm to 100 nm.

[0138] (3) Solid electrolyte layer

[0139] The solid electrolyte layer 30 is disposed between the positive electrode 10 and the negative electrode 20 (eg, between the positive electrode active material layer 14 and the negative electrode active material layer 24). The solid electrolyte layer 30 includes a solid electrolyte capable of transporting ions. The solid electrolyte layer 30 may include a sulfide-based solid electrolyte.

[0140] Sulfide-based solid electrolytes may 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, Z is 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 one of P, Si, Ge, B, Al, Ga, or In) or a combination thereof. The solid electrolyte may be composed of one material or two or more materials selected from these sulfide-based solid electrolyte materials.

[0141] The sulfide-based solid electrolyte may include a solid electrolyte represented by the following Formula 1:

[0142] <Formula 1>

[0143] Li x M' y PS z A w

[0144] in,

[0145] x, y, z and w are each independently 0 or more and 6 or less;

[0146] M' is at least one of As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb or Ta; and

[0147] A is at least one of F, Cl, Br or I.

[0148] As a solid electrolyte, a material containing sulfur (S), phosphorus (P) and lithium (Li) as constituent elements in a sulfide-based solid electrolyte material can be used. For example, a material containing Li2S-P2S5 can be used. When a material containing Li2S-P2S5 is used as a 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.

[0149] Furthermore, the solid electrolyte may be in an amorphous or crystalline state. Additionally, the solid electrolyte may be a mixture of amorphous and crystalline forms.

[0150] The solid electrolyte layer 30 may further include a binder. The binder material may be, for example, a resin such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or polyacrylic acid. The binder material may be the same as or different from the material constituting the binder in the positive electrode active material layer 14 and the negative electrode active material layer 24.

[0151] (4) Initial charge capacity ratio

[0152] In an all-solid-state lithium-ion secondary battery 100 of one embodiment, the initial charge capacity of the positive electrode active material layer 14 is too large relative to the initial charge capacity of the negative electrode active material layer 24. As described later, the all-solid-state lithium-ion secondary battery 100 of one embodiment can be used after charging exceeding the initial charge capacity of the negative electrode active material layer 24 (i.e., overcharging). At the start of charging, lithium can be embedded in the negative electrode active material layer 24. That is, the negative electrode active material can form an alloy or a compound with lithium ions migrated from the positive electrode 10. When charging exceeds the initial charge capacity of the negative electrode active material layer 24, lithium can be precipitated on the back side 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 then a metal layer 26 can be formed from this lithium, as shown in FIG. Figure 4 As shown. The metal layer 26 may be mainly composed of lithium in which Ag is solid-dissolved (i.e., Ag-Li solid solution). This phenomenon may be caused by a negative electrode active material, such as a material that forms an alloy or compound with lithium. During discharge, the lithium in the negative electrode active material layer 24 and the metal layer 26 may be ionized and moved to the positive electrode 10, while leaving the solid-dissolved Ag. Therefore, in the all-solid-state lithium-ion secondary battery 100, lithium can be used as a negative electrode active material. In addition, since the negative electrode active material layer 24 covers the metal layer 26, it can act as a protective layer for the metal layer 26 while inhibiting the precipitation and growth of dendrite metal lithium.

[0153] Preferably, the all-solid-state lithium-ion secondary battery 100 of one embodiment satisfies the ratio of the initial charge capacity of the positive electrode active material layer 14 to the initial charge capacity of the negative electrode active material layer 24, that is, the initial charge capacity ratio b / a of the following equation (100):

[0154] 0.01< b / a< 0.5 (100)

[0155] Here, a is the initial charge capacity (mAh) of the positive electrode active material layer 14 , and b is the initial charge capacity (mAh) of the negative electrode active material layer 24 .

[0156] If the initial charge capacity is less than 0.01, there is a risk that the characteristics of the all-solid-state lithium-ion secondary battery 100 may deteriorate. The reason may be that the negative electrode active material layer 24 cannot fully act as a protective layer. For example, if the thickness of the negative electrode active material layer 24 is very thin, the capacity ratio may be less than 0.01. In this case, there is a risk that the negative electrode active material layer 24 may collapse and dendrite metal lithium may precipitate and grow due to repeated charging and discharging. Therefore, the characteristics of the all-solid-state lithium-ion secondary battery 100 may deteriorate. Therefore, the initial charge capacity may be more than 0.01. At the same time, if the initial charge capacity is greater than 0.5, the amount of lithium deposited on the negative electrode may decrease, and therefore the capacity of the battery may decrease. Therefore, the initial charge capacity may be less than 0.5.

[0157] (5) Composition of all-solid-state lithium-ion secondary batteries

[0158] The all-solid lithium ion secondary battery 100 of the present invention is an all-solid lithium ion secondary battery 100 that sequentially includes a positive electrode 10, a solid electrolyte layer 30, and a negative electrode 20. 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 contains a carbon material and Ag, and may include two or more layers.

[0159] The negative electrode current collector 22 may include Ni foil, Ni-coated Cu foil, stainless steel foil, or a combination thereof. The negative electrode current collector 22 may have a further improved discharge capacity.

[0160] <Method for manufacturing all-solid-state lithium-ion secondary battery>

[0161] Next, a description will be given of a method for manufacturing the all-solid lithium ion secondary battery 100. The all-solid lithium ion secondary battery 100 according to the embodiment may be obtained by separately manufacturing the cathode 10, the anode 20, and the solid electrolyte layer 30 and then stacking the layers.

[0162] (10) Cathode manufacturing process

[0163] The positive electrode manufacturing process is illustrated as follows. First, the materials constituting the positive electrode active material layer 14 (positive electrode active material, binder (adhesive), etc.) are added to a non-polar solvent to prepare a slurry (or paste). Then, the obtained slurry is applied to the prepared positive electrode current collector 12, and it is dried to obtain a laminate. Next, the obtained laminate is pressurized using, for example, hydrostatic pressure to obtain the positive electrode 10. In addition, the pressing process is omitted.

[0164] (20) Negative electrode manufacturing process

[0165] The negative electrode manufacturing process is illustrated as follows. First, the material constituting the negative electrode active material layer 24 (negative electrode active material containing Ag, binder (adhesive), etc.) is added to a polar solvent or a non-polar solvent to prepare a slurry (which may be a paste). Then, the obtained slurry is applied to the prepared negative electrode current collector 22 to form the negative electrode active material layer of the first layer. Next, a slurry (which may be a paste) having an Ag content different from that of the first layer is prepared. Then, the obtained slurry is applied to the upper surface of the second layer and dried to obtain a laminate.

[0166] If the negative electrode active material layer further includes more than one layer, the additional layers may be stacked in the same manner as described above.

[0167] Next, the obtained laminate is pressurized using, for example, a hydrostatic pressure to manufacture the negative electrode 20. In addition, the pressurization process may be omitted. In addition, the method of applying the slurry to the negative electrode collector 22 is not particularly limited, and may be, for example, a screen printing method, a metal mask printing method, an electrostatic coating method, a dip coating method, a spray coating method, a roll coating method, a doctor blade method, and a gravure coating method.

[0168] Hereinbefore, a method of forming the negative electrode active material layer as two layers has been described, but even in the case of forming an additional layer, slurry for forming each layer is prepared and each layer is sequentially stacked according to the stacking order by the above method to manufacture a negative electrode.

[0169] (3) Solid electrolyte layer manufacturing process

[0170] The solid electrolyte layer 30 may be made of, for example, a solid electrolyte including a sulfide-based solid electrolyte material.

[0171] First, the starting material (such as Li2S, P2S5, etc.) is processed by a melt quenching method or a mechanical grinding method to obtain a sulfide-based solid electrolyte material. For example, when using a melt quenching method, the starting material is mixed in a predetermined amount, and the obtained mixture is granulated, reacted at a predetermined reaction temperature in a vacuum, and then quenched to prepare a sulfide-based solid electrolyte material. In addition, the reaction temperature of the mixture of Li2S and P2S5 can be 400°C to 1000°C, such as 800°C to 900°C. In addition, the reaction time can be 0.1 hours to 12 hours, such as 1 hour to 12 hours. In addition, the quenching temperature of the reactant can be below 10°C, such as below 0°C, and the quenching rate can generally be 1°C / second to 10000°C / second, such as 1°C / second to 1000°C / second.

[0172] In addition, when the mechanical grinding method is used, the starting material is stirred and reacted to prepare the sulfide-based solid electrolyte material using a ball mill, etc. In addition, the stirring speed and stirring time in the mechanical grinding method are not particularly limited, but the faster 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 material to the sulfide-based solid electrolyte material.

[0173] Then, the obtained mixed raw material (sulfide-based solid electrolyte material) is heat-treated at a predetermined temperature and then pulverized to prepare a particulate solid electrolyte. If the solid electrolyte has a glass transition point, it is sometimes transformed from amorphous to crystalline by heat treatment.

[0174] Next, the solid electrolyte obtained by the above method can be formed into a film using, for example, a known film forming method (such as an aerosol positioning method, a cold spray method, or a sputtering method) to prepare a solid electrolyte layer 30. In addition, the solid electrolyte layer 30 can be manufactured by pressing solid electrolyte particles. In addition, the solid electrolyte layer 30 can be prepared by mixing a solid electrolyte, a solvent, and a binder, applying the mixture, and drying and pressing it.

[0175] (4) Stacking process

[0176] The solid electrolyte layer 30 is provided between the cathode 10 and the anode 20 , and they are pressurized using, for example, hydrostatic pressure to obtain the all-solid lithium ion secondary battery 100 according to the embodiment.

[0177] The all-solid lithium ion secondary battery 100 of the present invention can provide improved discharge capacity without applying high external pressure using end plates 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.

[0178] <Method for Charging All-Solid-State Lithium-Ion Secondary Battery>

[0179] Next, a charging method of the all-solid lithium ion secondary battery 100 will be described.

[0180] In the charging method of the all-solid lithium ion secondary battery 100 according to the embodiment, the all-solid lithium ion secondary battery 100 may be charged to exceed the charge capacity of the negative electrode active material layer 24 (ie, overcharge).

[0181] When charging starts, lithium can be inserted into the negative electrode active material layer 24. When the battery is charged to exceed the charge capacity of the negative electrode active material layer 24, lithium is precipitated on the back side 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, as shown in FIG. Figure 4As shown, a metal layer 26 that does not exist during manufacturing can be formed by the precipitated lithium. During discharge, the lithium in the negative electrode active material layer 24 and the metal layer 26 is ionized and can migrate toward the positive electrode 10. Therefore, in the all-solid-state lithium ion secondary battery 100 of the present invention, lithium can be used as a negative electrode active material. In addition, since the negative electrode active material layer 24 covers the metal layer 26, it can act as a protective layer for the metal layer 26, and at the same time, the precipitation and growth of dendrite metal lithium can be suppressed. In this way, the short circuit and capacity decline of the all-solid-state lithium ion secondary battery 100 can be suppressed, and in addition, the characteristics of the all-solid-state lithium ion secondary battery 100 can be improved. In addition, 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.

[0182] In addition, 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. Figure 4 As shown, and may also be formed inside the negative electrode active material layer 24. In addition, the metal layer 26 may be formed between the negative electrode collector 22 and the negative electrode active material layer 24 and inside the negative electrode active material layer 24.

[0183] The all-solid-state lithium-ion secondary battery 100 of the present invention can be manufactured as a unit cell having a positive electrode / separator / negative electrode structure, a dual cell having a positive electrode / separator / negative electrode / separator / positive electrode structure, or a stacked battery structure in which the unit cell structure is repeated.

[0184] The shape of the all-solid-state lithium ion secondary battery 100 of the present invention is not particularly limited, and can be exemplified as coin type, button type, sheet type, stack type, cylindrical type, flat type, horn type, etc. In addition, it can also be used for large batteries used in electric vehicles, etc. For example, the all-solid-state lithium ion secondary battery 100 can also be used for hybrid vehicles, such as plug-in hybrid electric vehicles (PHEV). In addition, it can be used in fields that require a large amount of power storage. For example, it can be used for electric bicycles or electric tools.

[0185] Hereinafter, in order to specifically describe the present invention, the present invention will be described in detail with reference to embodiments. However, the embodiments of the present invention may be modified in various other forms, and the scope of the present invention should not be construed as being limited to the embodiments described below. Embodiments of the present invention are provided in order to more completely explain the present invention to those of ordinary skill in the art.

[0186] Comparative Example 1: Preparation of negative electrode

[0187] 6g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 2g of Ag having a particle size (D50) of 40nm to 60nm, 9.33g of PVdF binder (6% solid content) and 7.67g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a negative electrode active material slurry.

[0188] Then, the slurry was coated on a SUS foil to a thickness of 60 μm and dried to prepare a negative electrode.

[0189] Example 1: Preparation of negative electrode

[0190] 3g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 1.33g of Ag having a particle size (D50) of 40nm to 60nm, 4.67g of PVdF binder (6% solid content) and 1.5g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a first negative active material slurry.

[0191] 3g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 0.66g of Ag having a particle size (D50) of 40nm to 60nm, 4.67g of PVdF binder (6% solid content) and 1.5g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a second negative active material slurry.

[0192] Then, the first negative active material slurry was coated on the SUS foil to a thickness of 30 μm and dried, and then the second negative active material slurry was coated on the upper surface of the first negative active material layer formed by coating to a thickness of 30 μm and dried to prepare a negative electrode.

[0193] Example 2: Preparation of negative electrode

[0194] 3g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 2g of Ag having a particle size (D50) of 40nm to 60nm, 4.67g of PVdF binder (6% solid content) and 1.5g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a first negative active material slurry.

[0195] 3 g of carbon black having a particle size (D50) of 40 nm to 60 nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 4.67 g of PVdF binder (6% solid content) and 1.5 g of NMP solution were placed in a Thinky mixer container and mixed at 2000 rpm for 12 times for 3 minutes each time. Then, 5 g of NMP solution was added and then mixed at 2000 rpm for 5 times for 3 minutes each time to prepare a second negative active material slurry.

[0196] Then, the first negative active material slurry was coated on the SUS foil to a thickness of 30 μm and dried, and then the second negative active material slurry was coated on the upper surface of the first negative active material layer formed by coating to a thickness of 30 μm and dried to prepare a negative electrode.

[0197] Example 3: Preparation of negative electrode

[0198] 2g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 1.33g of Ag having a particle size (D50) of 40nm to 60nm, 3.11g of PVdF binder (6% solid content) and 1.5g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a first negative active material slurry.

[0199] 2g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 0.66g of Ag having a particle size (D50) of 40nm to 60nm, 3.11g of PVdF binder (6% solid content) and 1.5g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a second negative active material slurry.

[0200] 2 g of carbon black having a particle size (D50) of 40 nm to 60 nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 3.11 g of PVdF binder (6% solid content) and 1.5 g of NMP solution were placed in a Thinky mixer container and mixed at 2000 rpm for 12 times for 3 minutes each time. Then, 5 g of NMP solution was added and then mixed at 2000 rpm for 5 times for 3 minutes each time to prepare a third negative active material slurry.

[0201] Then, the first negative electrode active material slurry was coated on the SUS foil to a thickness of 20 μm and dried, and then the second negative electrode active material slurry was coated on the upper surface of the first negative electrode active material layer formed by coating to a thickness of 20 μm and dried.

[0202] Next, the third negative electrode active material slurry was coated on the upper surface of the second negative electrode active material layer formed by coating to a thickness of 20 μm and dried to prepare a negative electrode.

[0203] Example 4: Preparation of negative electrode

[0204] The first negative electrode active material slurry prepared in Example 1 was coated on a SUS foil to a thickness of 40 μm (Example 1: 30 μm) and dried, and then a negative electrode was prepared in the same manner as in Example 1, except that a second negative electrode active material slurry was coated on the upper surface of the first negative electrode active material layer formed by coating to a thickness of 20 μm (Example 1: 30 μm) and dried.

[0205] Example 5: Preparation of negative electrode

[0206] 2g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 1.33g of Ag having a particle size (D50) of 40nm to 60nm, 3.11g of PVdF binder (6% solid content) and 1.5g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a first negative active material slurry.

[0207] 2g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 0.66g of Ag having a particle size (D50) of 40nm to 60nm, 3.11g of PVdF binder (6% solid content) and 1.5g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a second negative active material slurry.

[0208] 2 to 5 g of Ag with a particle size (D50) of 40 nm to 60 nm, 3.11 g of PVdF binder (6% solid content) and 1.5 g of NMP solution were placed in a Thinky mixer container and mixed at 2000 rpm for 12 times for 3 minutes each time. Then, 5 g of NMP solution was added and then mixed at 2000 rpm for 5 times for 3 minutes each time to prepare a third negative active material slurry.

[0209] Then, the third negative electrode active material slurry was coated on the SUS foil to a thickness of 10 μm and dried, and then the first negative electrode active material slurry was coated on the upper surface of the third coating layer to a thickness of 20 μm and dried, and then the second negative electrode active material slurry was coated on the upper surface of the first negative electrode active material layer formed by coating to a thickness of 20 μm and dried to prepare a negative electrode.

[0210] Example 6: Preparation of negative electrode

[0211] 6g of carbon black having a particle size (D50) of 40nm to 60nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 6g of Ag having a particle size (D50) of 40nm to 60nm, 4.67g of PVdF binder (6% solid content) and 1.5g of NMP solution were placed in a Thinky mixer container and mixed at 2000rpm for 12 times for 3 minutes each time. Then, 5g of NMP solution was added and then mixed at 2000rpm for 5 times for 3 minutes each time to prepare a first negative active material slurry.

[0212] 6 g of carbon black having a particle size (D50) of 40 nm to 60 nm and an oxygen content of 5.2 atomic % as an amorphous carbon material, 4.67 g of PVdF binder (6% solid content) and 1.5 g of NMP solution were placed in a Thinky mixer container and mixed at 2000 rpm for 12 times for 3 minutes each time. Then, 5 g of NMP solution was added and then mixed at 2000 rpm for 5 times for 3 minutes each time to prepare a second negative electrode active material slurry.

[0213] Then, the first negative active material slurry was coated on the SUS foil to a thickness of 20 μm and dried, and then the second negative active material slurry was coated on the upper surface of the first negative active material layer formed by coating to a thickness of 40 μm and dried to prepare a negative electrode.

[0214] Preparation of All-Solid-State Lithium Ion Secondary Batteries of Example 7 and Comparative Example 2

[0215] The positive electrode active material is used at 5 mAh / cm 2 The positive electrode loaded on the current collector was used as the positive electrode, the negative electrode manufactured in Example 6 and Comparative Example 1 was used as the negative electrode, and the sulfide-based all-solid electrolyte was used as the electrolyte to manufacture the pouch-type single cells of Example 7 and Comparative Example 2.

[0216] Experimental Example 1: Evaluation of battery characteristics

[0217] The pouch-type single cells of Example 7 and Comparative Example 2 were operated in the operating voltage range of 4.25V-3.0V and at an operating temperature of 60°C under the following charging and discharging conditions to evaluate the cycle characteristics, and the results are shown in Figure 6 middle.

[0218] Charging conditions: 0.33C, 4.25V CC / CV, 0.1C cut-off

[0219] Discharge conditions: 0.33C, 3.0V, CC

[0220] from Figure 5 It can be seen that in the case of the battery of Example 7, compared with the battery of Comparative Example 2, it operates without a significant decrease in cell capacity as the cycle progresses.

[0221] Figure 6 The SEM image of the negative electrode of Example 6 is shown. Figure 6 It can be seen that the negative electrode of Example 6 has many Ag particles arranged in the active material layer close to the current collector, and the battery of Example 7 seems to have improved cycle characteristics by including the negative electrode having such a structure.

[0222] Experimental Example 2: Measurement of the particle size of carbon material-Ag composite

[0223] (1) Separation of carbon material-metal composite samples

[0224] The sample for analysis was prepared by taking a portion of the carbon material-metal composite contained in the first negative electrode active material slurry of Example 1 and the negative electrode active material slurry of Comparative Example 2 (prepared in the same manner as the first negative electrode active material slurry of Example 1, except that carbon black with an oxygen content of 2.6 atomic % was used instead of carbon black with an oxygen content of 5.2 atomic %) and diluting it in an NMP solution.

[0225] (2) Analytical instruments

[0226] The 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 having an oxygen content of 5.2 atomic %) and the carbon material-metal composite analysis sample 2 (containing carbon black having an oxygen content of 2.6 atomic %) prepared in (1) above were placed in the sample inlet of the device to achieve a laser shielding of 10-15%, and the measurement was performed.

[0227] The analyzer can analyze particle sizes ranging from 0.01μm to 3500μm and is a particle size analyzer that uses laser diffraction and is suitable for both wet and dry dispersion types.

[0228] (3) Analysis results

[0229] The particle size analysis results of carbon material-metal composite sample 1 and sample 2 are shown in Tables 1 and Figure 6 middle.

[0230] [Table 1]

[0231]

[0232] From the results in Table 1, it can be seen that the particle size of the carbon material-metal composite containing carbon black having an oxygen content of 5.2 atomic % is significantly smaller than that of the carbon material-metal composite containing carbon black having an oxygen content of 2.6 atomic %. Figure 3 From the analysis results shown, it can be seen that the maximum particle size of the carbon material-metal composite containing carbon black with an oxygen content of 5.2 atomic % is less than 1 μm, which is significantly smaller than the particle size of the carbon material-metal composite containing carbon black with an oxygen content of 2.6 atomic %.

Claims

1. An all-solid-state lithium-ion secondary battery, comprising: A positive electrode, a negative electrode, and a solid electrolyte between the positive electrode and the negative electrode, Wherein, the negative electrode comprises a negative electrode current collector and a negative electrode active material layer, and The negative electrode active material layer contains carbon material and Ag, and includes two or more layers.

2. The all-solid-state lithium-ion secondary battery according to claim 1, wherein: The two or more layers include two layers containing a carbon material and Ag, and the two layers have different Ag contents.

3. The all-solid-state lithium-ion secondary battery according to claim 2, wherein: Of the two layers containing the carbon material and Ag, the layer disposed adjacent to the negative electrode current collector has a higher Ag content ratio than the layer disposed adjacent to the solid electrolyte.

4. The all-solid-state lithium-ion secondary battery according to claim 3, wherein: The layer disposed adjacent to the negative electrode current collector contains 1.5 to 10 times more Ag than the layer disposed adjacent to the solid electrolyte.

5. The all-solid-state lithium-ion secondary battery according to claim 3, wherein: The two layers containing the carbon material and Ag each independently have a thickness of 1 μm to 50 μm.

6. The all-solid lithium ion secondary battery according to claim 3, further comprising, in addition to the two layers containing the carbon material and Ag, a layer containing 0 to 5 wt% of Ag and the carbon material based on 100 wt% in total of the negative electrode active material.

7. The all-solid-state lithium-ion secondary battery according to claim 6, wherein: The layer containing 0 to 5 wt % of Ag and a carbon material is a layer free of Ag.

8. The all-solid-state lithium-ion secondary battery according to claim 6, wherein: The layer containing 0 to 5 wt % of Ag and a carbon material is provided between the two layers containing the carbon material and Ag, or between a layer adjacent to a solid electrolyte and the solid electrolyte of the two layers.

9. The all-solid-state lithium-ion secondary battery according to claim 8, wherein: The layer containing 0 to 5 wt % of Ag and a carbon material is provided between the layer adjacent to the solid electrolyte of the two layers and the solid electrolyte.

10. The all-solid-state lithium-ion secondary battery according to claim 6, wherein: The layer containing 0 to 5 wt % of Ag and carbon material has a thickness of 1 to 30 μm.

11. The all-solid lithium ion secondary battery according to claim 3, further comprising a layer containing 80 to 100 wt% of Ag based on 100 wt% in total of the negative electrode active material, in addition to the two layers containing the carbon material and Ag.

12. The all-solid-state lithium-ion secondary battery according to claim 11, wherein: The layer containing 80 to 100 wt % of Ag based on 100 wt % in total of the negative electrode active material is disposed between the layer adjacent to the negative electrode collector and the negative electrode collector of the two layers.

13. The all-solid-state lithium-ion secondary battery according to claim 1, wherein: The two or more layers include a layer containing a carbon material and Ag and a layer containing 0 to 5 wt % of Ag and a carbon material.

14. The all-solid-state lithium-ion secondary battery according to claim 1, wherein: The positive electrode includes a positive electrode current collector and a positive electrode active material layer.

15. The all-solid-state lithium-ion secondary battery according to claim 1, wherein: The solid electrolyte is a sulfide-based solid electrolyte.

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