KR102812166B1 - A negative electrode and a lithium ion secondary battery including the negative electrode - Google Patents

Abstract

The present invention provides an anode 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, and a lithium ion secondary battery including the negative electrode.

Description

A negative electrode and a lithium ion secondary battery including the negative electrode

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

Recently, all-solid-state secondary batteries using solid electrolytes as electrolytes have been attracting attention. In order to improve the energy density of such all-solid-state secondary batteries, it has been proposed to use lithium as an anode active material. The capacity density (capacity per unit weight) of lithium is about 10 times that of graphite, which is generally used as an anode active material. Therefore, when lithium is used as an anode active material, it is possible to increase the output while making the all-solid-state secondary battery thinner.

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

The above anode-less lithium-ion secondary battery is driven by a mechanism in which metallic lithium is deposited between the negative electrode active material layer and the current collector during charging, and the metallic lithium is ionized and moves toward the positive electrode during discharge.

The above negative active material layer is formed as a very thin film with a micro-thickness, but there was a problem that it was difficult to form a negative active material layer with low surface roughness.

Republic of Korea Publication Patent No. 10-2015-0064697

The present invention has been devised to solve the above problems of the prior art.

The purpose of the present invention is to provide an anode having improved performance and a lithium ion secondary battery including the same, which significantly improves the operating characteristics of a battery by uniformly distributing carbon material and metal in the anode active material layer and significantly improving the surface roughness.

In order to achieve the above purpose, the present invention

Contains a collector and a negative electrode active material layer,

The above negative electrode active material layer provides a negative electrode including one or more active material layers containing 2 to 10 at% of oxygen.

In addition, the present invention

A lithium ion secondary battery is provided, comprising the above negative electrode; the positive electrode; and an electrolyte disposed between the negative electrode and the positive electrode.

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

In addition, the lithium ion secondary battery of the present invention provides excellent driving characteristics by including the negative electrode active material layer.

Figures 1 and 2 are cross-sectional views schematically showing the structure of the lithium ion secondary battery of the present invention.
Figure 3 is a graph showing the particle size distribution of the carbon material-metal composite of the present invention.
Figure 4 is a graph showing the results of rheological analysis of a negative electrode active material slurry containing a carbon material-metal composite of the present invention.
Figures 5 and 6 are graphs showing the cycle characteristics of a lithium ion secondary battery including a negative active material layer including a carbon material-metal composite of the present invention.
Figure 7 shows the 1s spectrum of carbon (C) included in the negative electrode active material layer manufactured in Example 2, Comparative Example 3, and Comparative Example 4.
Figure 8 shows the results of peak deconvolution in the O 1s spectrum for oxygen included in the negative electrode active material layers manufactured in Example 2, Comparative Example 3, and Comparative Example 4.
Figure 9 is a SEM image of the surface of the negative electrode active material layer laminated on the negative electrode manufactured in Example 2 and Comparative Example 5 of the present invention.
Figure 10 is a laser confocal microscope photograph showing the results of measuring the surface roughness of the negative electrode active material layer laminated on the negative electrode manufactured in Example 2 and Comparative Example 5 of the present invention.

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

The terms or words used in this specification and claims should not be interpreted as limited to their usual or dictionary meanings, but should be interpreted as meanings and concepts that conform to the technical idea of the present invention based on the principle that the inventor can appropriately define the concept of the term to best describe his or her own invention. In addition, the terms used in this specification are only used to describe exemplary embodiments and are not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly indicates otherwise.

When a component is said to be "connected to, provided with, or installed" another component, it should be understood that it may be directly connected or installed to the other component, but there may also be other components in between. On the other hand, when a component is said to be "directly connected to or installed" another component, it should be understood that there are no other components in between. Meanwhile, other expressions that describe the relationship between components, such as "above" and "directly above", "between" and "directly between", or "adjacent to" and "directly adjacent to", should be interpreted similarly.

The term "combination" as used herein includes mixtures, alloys, reaction products, etc., unless specifically stated otherwise.

The electrode of the present invention comprises a current collector and a negative electrode active material layer,

The above negative active material layer is characterized by including one or more active material layers containing 2 to 10 at% of oxygen.

The lower limit of the oxygen content may 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. In addition, the upper limit of the oxygen content may 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 may be in a range formed by a combination of the lower limit value and the upper limit value. Specifically, it may be preferable when the oxygen is included in an amount of 2.5 to 10 at%.

In the above, if the oxygen content is less than 2 at%, the surface roughness of the active material layer is significantly reduced, which is not desirable, and if it exceeds 10 at%, the performance of the battery deteriorates due to a side reaction with the solid electrolyte, which is not desirable.

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

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

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

In one embodiment of the present invention, the one or more active material layers may include 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).

Additionally, it may more preferably 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).

In addition, sulfur (s) may be further included in addition to the above components.

The composition ratio of the one or more active material layers can be measured using a photoelectron spectroscopy (XPS or ESCA). For example, the composition ratio of the one or more active material layers can be measured using a Nexsa4 (Thermo Fisher Scientific) device.

In one embodiment of the present invention, the one or more active material layers may include carbon material particles and metal particles, and the carbon material particles may be, for example, amorphous carbon material particles. Specific examples of the amorphous carbon material include carbon black such as acetylene black, furnace black, and Ketjen black.

When the amorphous carbon material particles include pores, the size of the pores may be 1 nm or less, preferably 0.5 nm or less. However, it may be more preferable that the amorphous carbon material particles do not include pores. This is because when the amorphous carbon material particles include pores, lithium may be precipitated inside the pores, and the lithium may be deactivated, and the amount of lithium deactivated in this way may increase as charge and discharge are repeated.

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

The above carbon material particles may be carbon material particles containing 3 to 10 at% of oxygen. If the oxygen content is less than 3 at%, the surface roughness of the active material layer is significantly reduced, which is not preferable. If the oxygen content exceeds 10 at%, the performance of the battery is reduced due to a side reaction with the solid electrolyte, which is not preferable.

In the above, the lower limit of the oxygen content may be 3.5 at% or more, 4 at% or more, or 4.5 at% or more. In addition, the upper limit of the content may 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 may be in a range formed by a combination of the lower limit value and the upper limit value. Specifically, the oxygen content may be preferably 5 to 10 at%.

In one embodiment of the present invention, the oxygen may be present in a form included in a functional group bonded to carbon material particles. In addition, the functional group may include at least one 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.

The carbon material particles containing 3 to 10 at% of oxygen can be produced, for example, by a method of oxidizing the carbon material. Specifically, the carbon material is treated with an acid and reacted while stirring at a temperature of 25 to 60° C., thereby introducing an oxygen functional group to the surface of the carbon material. The type of the acid is not particularly limited, and any acid that can introduce an oxygen functional group to the surface of the carbon material can be used. 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.

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

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 includes the surface of the pores if pores exist.

In one embodiment of the present invention, the metal particles may be particles forming an alloy with lithium, and the metal particles may be at least one particle selected from silver (Ag), gold, platinum, palladium, silicon, aluminum, bismuth, tin, indium, and zinc.

In one embodiment of the present invention, it may be preferable that the metal particles include silver (Ag).

In one embodiment of the present invention, the one or more active material layers may have the following surface roughness characteristics:

0.01 ㎛ ≤ Sa ≤ 0.3 ㎛

0.5 ㎛ ≤ Sz ≤ 5 ㎛

500 mm ^-1 ≤ Spc ≤ 1500 mm ^-1

0.005 ≤ Sdr ≤ 0.15.

When the surface roughness satisfies the above range, the overall battery characteristics are 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 made in the electrolyte side direction, and uniform deposition of lithium is not facilitated in the negative electrode current collector side direction, which may deteriorate the battery characteristics.

The surface roughness of the negative electrode active material layer as described above can be measured using a microscope device. For example, it can be measured using a 3D laser confocal microscope device (manufactured by KEYENCE Corporation).

In the above, Sa (arithmetic mean height of the profile) may be at most 0.3 ㎛ or less, 0.2 ㎛ or less, 0.1 ㎛ or less, 0.08 ㎛ or less, or 0.075 ㎛ or less, and at least 0.01 ㎛ or more, 0.02 ㎛ or more, 0.03 ㎛ or more, 0.04 ㎛ or more, 0.05 ㎛ or more, 0.06 ㎛ or more, or 0.07 ㎛ or more. In addition, it may be more preferable that Sa is in the range of 0.01 ㎛ ≤ Sa ≤ 0.1 ㎛, but is not limited to these ranges, and may be set as a combined range of the maximum and minimum values. The Sa represents the average value of the absolute value of the height difference between each point with respect to the average plane of the surface.

In the above, Sz (maximum height roughness of the profile) may be at most 5 ㎛ or less, 4 ㎛ or less, 3 ㎛ or less, 2 ㎛ or less, or 1.5 ㎛ or less, and may be at least 0.5 ㎛ or more, 0.8 ㎛ or more, 1 ㎛ or more, 1.1 ㎛ or more, 1.2 ㎛ or more, or 1.3 ㎛ or more. In addition, it may be more preferable that the Sz is in the range of 0.5 ㎛ ≤ Sz ≤ 1.6 ㎛, but is not limited to these ranges, and may be set as a combination range of the maximum and minimum values. The Sz is the maximum height roughness within a single plane, and represents the distance between the highest point and the lowest point within the single plane.

In the above, Spc (roughness by number of peaks) may 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 may 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. In addition, a range of 500 mm ^-1 ≤ Spc ≤ 1100 mm ^-1 may be more preferable, but is not limited to these ranges, and may be set as a combined range of the maximum and minimum values. The Spc is a roughness by number of peaks and is a measure of the steepness of a peak.

In the above, Sdr (degree of increase in interface area) may 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, a range of 0.005 ≤ Sdr ≤ 0.03 may be more preferable, but is not limited to this range, and may be set to a range combined 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 viewing the measurement area of the expanded area (surface area of the measured shape) vertically.

Although the meanings of Sa, Sz, Spc, and Sdr are described above, they are used in the same meanings as commonly used in this field.

In one embodiment of the present invention, the at least one active material layer may have a porosity of 55 to 70%, more preferably 62 to 67%. When the porosity satisfies the above range, a desirable effect can be obtained in terms of securing uniformity of the coating layer within the electrode.

The porosity of the active material layer above is a value calculated using the weight and thickness values of the active material layer.

In one embodiment of the present invention, the at least one active material layer may include 60 to 80 wt% of carbon material particles containing 3 to 10 at% of oxygen, 10 to 30 wt% of metal particles, and 3 to 20 wt% of binder. Additionally, the at least one active material layer may include 65 to 75 wt% of carbon material particles containing 3 to 10 at% of oxygen, 20 to 30 wt% of metal particles, and 4 to 8 wt% of binder.

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

Recently, various studies have been conducted on all-solid-state lithium-ion secondary batteries, for example, anodeless lithium-ion secondary batteries including a negative electrode active material layer containing a metal that forms an alloy with lithium and a carbon material.

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

Furthermore, conventional carbon-metal composites have the problem that it is very difficult to form them into small particle sizes. That is, if the particle size of the carbon-metal composite is too large compared to the micro-thick film, it is difficult to form a negative electrode active material layer having excellent surface roughness, and accordingly, the operating characteristics of the battery deteriorate. Therefore, it is very important to manufacture the carbon-metal composite into small particle sizes.

The present invention provides an effect that dramatically improves the above-mentioned problems of the prior art.

That is, the carbon material-metal composite forms a carbon material-metal composite having a significantly smaller particle size compared to a case where a conventional carbon material is used. The carbon material forming the composite has the characteristics of containing 3 at% or more of oxygen, being well mixed with the metal particles, and being uniformly distributed with the metal particles. Therefore, it is possible to manufacture a carbon material-metal composite having excellent component uniformity. In addition, for the above reason, it is possible to manufacture a carbon material-metal composite having a small and uniform particle size.

In one embodiment of the present invention, the carbon material-metal composite may be formed by at least one bond selected from a chemical bond between carbon material particles and metal particles, a van der Waals bond between carbon material particles and metal particles, and a bond between carbon material particles and metal particles via a binder. 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.

In one embodiment of the present invention, the carbon material-metal composite may include 60 to 90 wt% of carbon material and 10 to 40 wt% of metal based on the total weight. In addition, it may include 70 to 80 wt% of carbon material and 20 to 30 wt% of metal.

In addition, the carbon material-metal composite may further include 3 to 10 wt% 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 may be used, in which case the binder may be included in the carbon material-metal composite. When the binder is included, the content of the carbon material described above may be included in a content range reduced by the content of the binder.

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

In one embodiment of the present invention, the particle size (D50) of the carbon material-metal 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.

Additionally, the maximum particle size of the carbon material-metal composite may be 3 ㎛ or less, 2 ㎛ or less, 1.5 ㎛ or less, or 1 ㎛ or less.

If the particle size of the carbon material-metal composite is too large compared to the micro-thick film, it is difficult to form a negative active material layer with excellent surface roughness, and thus the operating characteristics of the battery deteriorate. Therefore, it is very important to manufacture the carbon material-metal composite with a small particle size.

The reason why the operating characteristics of the above battery are deteriorated 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 direction of the electrolyte, and it does not help in the uniform deposition of lithium in the direction of the negative electrode current collector.

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

For example, if a carbon-metal 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 obvious that it is difficult to form a desirable surface roughness.

When the maximum particle size of the above carbon material-metal composite is 3㎛ or less, the effect of improving surface roughness can be more reliably obtained, which is preferable. On the other hand, when it exceeds 3㎛, it may be difficult to obtain excellent surface roughness when forming a thin film.

The particle size of the above carbon-metal composite can be measured using a particle size analyzer. For example, it can be measured using a Mastersizer 3000 (Malvem panalytical) instrument.

The present invention

It relates to a negative electrode active material slurry comprising the above carbon material-metal composite.

The above negative active material slurry may have a viscosity at a shear rate of 2.5 s ^-1 of 8 Pa·s or less, 7 Pa·s or less, 6 Pa·s or less, or 5 Pa·s or less.

The above-described negative active material slurry may include 15 to 50 wt% of the carbon material-metal composite, 1 to 10 wt% of the binder (based on solid content), and 40 to 80 wt% of the solvent, and preferably 25 to 35 wt% of the carbon material-metal composite, 1 to 5 wt% of the binder, and 60 to 70 wt% of the solvent. In addition, an additive included in the negative active material slurry of this field may be further included.

The present invention

It relates to a negative electrode active material layer including the above carbon material-metal composite.

The above negative active material layer has carbon material and metal uniformly distributed and has excellent surface roughness, thereby providing the effect of improving the operating characteristics of a lithium ion secondary battery including the same.

In addition, the present invention

A lithium ion secondary battery is provided, comprising the above negative electrode; the positive electrode; and an electrolyte disposed between the negative electrode and the positive electrode.

The above lithium ion secondary battery may be an anodeless battery.

The above lithium ion secondary battery provides improved driving characteristics by including the negative electrode active material layer of the present invention.

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

In one embodiment of the present invention, the lithium ion secondary battery may be an anodeless battery.

Hereinafter, embodiments of the present invention are exemplified in more detail.

<Composition of an all-solid-state lithium-ion secondary battery>

FIG. 1 is a cross-sectional view schematically showing the configuration of an all-solid-state lithium ion secondary battery according to one embodiment of the present invention.

An all-solid-state lithium ion secondary battery (100) according to one embodiment of the present invention is a so-called lithium ion secondary battery that performs charging and discharging by lithium ions moving between a positive electrode (10) and an 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) arranged between the positive electrode (10) and the negative electrode (20).

(1) Bipolar

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 sequence toward the negative electrode (20).

The positive electrode collector (12) may be plate-shaped or foil-shaped. The positive electrode collector (12) may be, for example, one type of metal or an alloy of two or more types of metals selected from indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, and lithium.

The cathode active material layer (14) can reversibly absorb and release lithium ions. The cathode active material layer (14) can include a cathode active material and a solid electrolyte.

The above cathode active material may be a compound capable of lithium insertion/de-insertion. Examples of the compound capable of lithium insertion/de-insertion include Li _a A _1-b B' _b D' ₂ (wherein the above formula, 0.90≤a≤1.8, and 0≤b≤0.5); Li _a E ₁ - _b B' _b O _2-c D' _c (wherein the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiE _2-b B' _b O _4-c D' _c (wherein the above formula, 0≤b≤0.5, 0≤c≤0.05); Li _a Ni _1-bc Co _b B' _c D' _α (wherein the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li _a Ni _1-bc 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-bc 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-bc 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 O ₂ (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 O ₂ (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 O ₂ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a CoG _b O ₂ (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a MnG _b O ₂ (wherein 0.90≤a≤1.8, 0.001≤b≤0.1); Li _a Mn ₂ G _b O ₄ (wherein 0.90≤a≤1.8, 0.001≤b≤0.1); QO ₂ ; QS ₂ ; LiQS ₂ ; V ₂ O 5 ; LiV ₂ O ₅ ; LiI'O ₂ ; LiNiVO ₄ ; Li _{( 3-f)} J ₂ (PO ₄ ) ₃ (0≤f≤2); Li _(3-f) Fe ₂ (PO ₄ ) ₃ (0≤f≤2); LiFePO ₄ .

In the 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.

Specific examples of the above-mentioned positive electrode active material include lithium cobaltate (hereinafter referred to as LCO), lithium nickelate, lithium nickel cobaltate, lithium nickel cobalt aluminum acid (hereinafter referred to as NCA), lithium nickel cobalt manganese acid (hereinafter referred to as NCM), lithium manganese acid, lithium iron phosphate, and lithium salts, and lithium sulfide. The positive electrode active material layer (14) may include only one selected from these compounds as the positive electrode active material, or may include two or more.

The above-described positive electrode active material may include a lithium salt of a transition metal oxide having a layered salt-like structure among the lithium salts described above. Here, the “layered salt-like structure” is a structure in which oxygen atomic layers and metal atomic layers are alternately and regularly arranged in the direction of the cubic salt-like structure, and as a result, each atomic layer forms a two-dimensional plane. In addition, the “cubic salt-like structure” means a sodium chloride-like structure, which is a type of crystal structure. For example, the “cubic salt-like structure” refers to a structure in which face-centered cubic lattices in which cations and anions are respectively formed are arranged displaced by half of the edges of the unit cell.

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 O ₂ (NCA) or LiNi _x Co _y Mn _z O ₂ (NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1). The cathode active material layer (14) includes a lithium salt of the ternary transition metal oxide having such a layered rock salt structure as a cathode active material, thereby improving the energy density and thermal stability of the all-solid-state lithium ion secondary battery (100).

Here, as the shape of the positive electrode active material, examples thereof include particle shapes such as spherical, elliptical, and spherical. In addition, the particle size of the positive electrode active material is not particularly limited, and may be within a range applicable to positive electrode active materials 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 not particularly limited, and may be within a range applicable to positive electrodes of a typical all-solid-state lithium-ion secondary battery.

Of course, it is also possible to use one having a coating layer on the surface of the compound, or it is also possible to use a mixture of the compound and the compound having the coating layer. The coating layer may include a coating element compound of an oxide, a hydroxide, an oxyhydroxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element of the coating element. The compounds forming these coating layers may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer forming process may use any coating method as long as it can coat the compound with these elements by a method (for example, spray coating, dipping, etc.) that does not adversely affect the properties of the positive electrode active material, and since this is well understood by those engaged in this field, a detailed description thereof will be omitted.

Specific examples of the above coating layer include Li ₂ O-ZrO ₂ , etc.

The solid electrolyte included in the cathode active material layer (14) may be the same as or different from the solid electrolyte included in the solid electrolyte layer (30) described later.

In addition, the cathode active material layer (14) may be a mixture of not only the cathode active material and solid electrolyte described above, but also an appropriate amount of additives such as a conductive agent, a binder, a filler, a dispersant, or an ion conductive assistant.

As the above-mentioned challenge agent, for example, graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or metal powder may be mentioned. In addition, as the above-mentioned binder, for example, styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene may be mentioned. In addition, as the above-mentioned filler, dispersant, or ion conductive auxiliary agent, a known material typically used in an electrode of an all-solid-state lithium ion secondary battery may be used.

(2) Cathode

The negative electrode (20) may include a negative electrode current collector (22) and a negative electrode active material layer (24) arranged sequentially toward the positive electrode (10).

The negative electrode current collector (22) may be plate-shaped or foil-shaped. The negative electrode current collector (22) may include a material that does not react with lithium, that is, does not form any alloy or compound with lithium. Examples of materials constituting the negative electrode current collector (22) include 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 of two or more metals or a clad material.

The negative active material layer (24) may not contain lithium between the negative current collector (22), the negative active material layer (24), or the negative active material layer (24) and the solid electrolyte layer (30) in the initial state or the fully discharged state. As described below, when the all-solid-state lithium ion secondary battery (100) according to one embodiment is overcharged, the negative active material contained in the negative active material layer (24) and lithium ions moved from the positive electrode (10) may form an alloy or compound, and a metal layer (26) mainly composed of lithium may be formed (deposited) on the negative electrode (20) as shown in FIG. 2. The metal layer (26) may be deposited and arranged between the negative current collector (22) and the negative active material layer (24), inside the negative active material layer (24), or in both. Between the negative electrode current collector (22) and the negative electrode active material layer (24), the metal layer (26) containing lithium as a main component may be arranged closer to the negative electrode current collector layer (22) than to the negative electrode active material layer (24).

The negative active material layer (24) according to one embodiment may include Ag as the negative active material. Accordingly, 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 dissolved in lithium. Therefore, during discharge, only Li is dissolved in the Li(Ag) alloy constituting the metal layer (26), and the dissolved Ag remains, thereby suppressing the occurrence of pores. In this case, the content of Ag in the precipitated Li-Ag solid solution may be 60 wt% or less. Within this 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 becomes small, and the occurrence of pores may not be sufficiently suppressed. For this reason, the content of Ag in the precipitated Li-Ag solid solution may be 20 wt% or more, for example, 40 wt% or more.

If the content of Ag included in the above-described negative electrode active material layer (24) is too small, the Ag remaining during discharge also decreases, so it may become impossible to suppress the occurrence of pores. For this reason, the negative electrode active material layer (24) may include Ag at 10 wt% or more, for example, 20 wt% or more, based on 100 wt% of the total negative electrode active material included in the negative electrode active material layer, in the initial state where no charge or discharge has been performed.

The above negative electrode active material layer (24) may further include any negative electrode active material other than Ag, for example, at least one selected from amorphous carbon, Au, Pt, Pd, Si, Al, Bi, Sn, In, and Zn.

Amorphous carbon can be preferably used as the carbon material included in the negative electrode active material layer (24). 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.

Based on 100 wt% of the total negative electrode active material included in the negative electrode active material layer (24), the negative electrode active material other than Ag may be combined to be 50 wt% or more, for example, 70 wt% or more. The content of the negative electrode active material other than Ag may be measured in the same manner as the content of Ag.

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

In addition, the negative electrode active material layer (24) may be appropriately mixed with additives used in conventional all-solid-state lithium ion secondary batteries, such as fillers, dispersants, and ionic conductors. Specific examples of the additives are the same as those described for the positive electrode described above.

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

Meanwhile, a film including a material capable of forming an alloy or compound with lithium may be further included on the negative electrode current collector (22), and the film may be placed between the negative electrode current collector (22) and the negative electrode active material layer.

The above negative electrode current collector (22) does not react with lithium metal, but can make it difficult to deposit a smooth lithium metal layer on top. The above film can also be used as a wetting layer that allows lithium metal to be deposited evenly on top of the negative electrode current collector (22).

The material capable of forming an alloy with lithium metal used in the film may include silicon, magnesium, aluminum, lead, silver, tin, or a combination thereof. The material capable of forming a compound with lithium metal used in the film may include carbon, titanium sulfide, iron sulfide, or a combination thereof. The content of the material used in the film may be a small amount within a range that does not affect the electrochemical properties of the electrode or/and the redox potential of the electrode. The film may be applied flatly on the negative electrode current collector (22) to prevent cracking during the charge cycle of the all-solid-state lithium ion secondary battery (100). The film may be applied using a method such as physical deposition such as evaporation or sputtering, chemical deposition, or a plating method.

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

(3) Solid electrolyte layer

A solid electrolyte layer (30) is arranged 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) includes a solid electrolyte capable of moving ions. The solid electrolyte layer (30) may include a sulfide-based solid electrolyte.

The above sulfide-based solid electrolyte is Li ₂ SP ₂ S ₅ , Li ₂ SP ₂ S ₅ -LiX (X is a halogen element), Li ₂ SP ₂ S ₅ -Li ₂ O, Li ₂ SP ₂ S ₅ -Li ₂ O-LiI, Li ₂ S-SiS ₂ , Li ₂ S-SiS ₂ -LiI, Li ₂ S-SiS ₂ -LiBr, Li ₂ S-SiS ₂ -LiCl, Li ₂ S-SiS ₂ -B ₂ S ₃ -LiI, Li ₂ S-SiS ₂ -P ₂ S ₅ -LiI, Li ₂ SB ₂ S ₃ , Li ₂ SP ₂ S ₅ -Z _m S _n (m and n are positive numbers, Z is one of Ge, Zn, or Ga), Li ₂ S-GeS ₂ , Li ₂ S-SiS ₂ -Li ₃ PO ₄ , Li ₂ S-SiS ₂ -Li _p MO _q (p and q are positive numbers, 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 selected from these sulfide-based solid electrolyte materials, or may be composed of two or more materials.

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

<Chemical Formula 1>

Li _x M' _y PS _z A _w

In the above chemical formula 1,

x, y, z, w are independently greater than or equal to 0 and less than or equal to 6;

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.

As a solid electrolyte, one containing sulfur (S), phosphorus (P), and lithium (Li) as constituent elements among the above sulfide solid electrolyte materials can be used. For example, one containing Li ₂ SP ₂ S ₅ can be used. When one containing Li ₂ SP ₂ S ₅ is used as the sulfide-based solid electrolyte material, the mixing molar ratio of Li ₂ S and P ₂ S ₅ can be selected in the range of, for example, Li ₂ S:P ₂ S ₅ = 50:50 to 90:10.

In addition, the solid electrolyte may be in an amorphous or crystalline state. In addition, it may be in a mixed amorphous and crystalline state.

The solid electrolyte layer (30) may further include 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 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).

(4) Composition of all-solid-state lithium-ion secondary battery

The all-solid-state lithium ion secondary battery (100) of the present invention may be an all-solid-state lithium ion secondary battery (100) including a positive electrode (10), a solid electrolyte layer (30), and an anode (20) in this order, as illustrated in FIG. 1. The anode (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 metal capable of forming an alloy with a carbon material and lithium.

The above negative electrode current collector (22) may include Ni foil, Ni-coated Cu foil, stainless steel foil, or a combination thereof. Such a negative electrode current collector (22) may further improve the discharge capacity.

<Method for manufacturing an all-solid-state lithium-ion secondary battery>

Next, a method for manufacturing the above-described 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 manufacturing a positive electrode (10), a negative electrode (20), and a solid electrolyte layer (30), respectively, and then laminating each of the above layers.

(1) Bipolar manufacturing process

The positive electrode manufacturing process is explained as follows with an example. First, materials (positive electrode active material, binder, etc.) constituting the positive electrode active material layer (14) are added to a non-polar solvent to produce a slurry (or paste). Then, the obtained slurry is applied onto the prepared positive electrode current collector (12). This is dried to obtain a laminate. Then, the obtained laminate is pressurized using, for example, hydrostatic pressure to obtain a positive electrode (10). In addition, the pressurizing process is omitted.

(2) Cathode manufacturing process

The negative electrode manufacturing process is explained as follows with an example. First, materials (carbon material, metal forming an alloy with lithium, binder, etc.) constituting the negative electrode active material layer (24) are added to a polar solvent or a nonpolar solvent to prepare a slurry (paste may also be used). Then, the obtained slurry is applied onto the prepared negative electrode current collector (22) to form a negative electrode active material layer.

If the above negative active material layer additionally includes one or more layers, additional layers can be laminated in the same manner as above.

Next, the laminate obtained by the above method is pressurized, for example, using hydrostatic pressure, to produce a negative electrode (20). In addition, the pressurizing process may be omitted. In addition, the method of applying the slurry to the negative electrode current collector (22) is not particularly limited, and examples thereof include screen printing, metal mask printing, electrostatic painting, dip coating, spray coating, roll coating, doctor blade, and gravure coating.

The method of forming a two-layer negative electrode active material layer is described above, but even in the case of forming additional layers, the negative electrode can be manufactured by preparing a slurry for forming each layer and sequentially stacking each layer according to the stacking order using the method described above.

(3) Solid electrolyte layer manufacturing process

The solid electrolyte layer (30) can be manufactured using a solid electrolyte including, for example, a sulfide-based solid electrolyte material.

First, the starting materials (e.g., Li ₂ S, P ₂ S ₅ , etc.) are processed by a melting quenching method or a mechanical milling method to obtain a sulfide-based solid electrolyte material. For example, when the melting quenching method is used, the starting materials are mixed in a predetermined amount, made into pellets, reacted in a vacuum at a predetermined reaction temperature, and then quenched to produce a sulfide-based solid electrolyte material. In addition, the reaction temperature of the mixture of Li 2 S and P 2 S 5 can be 400 ° C to 1000 ° C, for example, 800 ° C to 900 ° C. In addition, the reaction time can be 0.1 hour to 12 hours, for example, 1 hour to 12 hours. In addition, the quenching temperature of the reactants can be 10 ° C or less, for example, 0 ° C or less, and the quenching speed can be typically 1 ° C/sec to 10,000 ° C/sec, for example, 1 ° C/sec to 1000 ° C/sec.

In addition, when using a mechanical milling method, a sulfide-based solid electrolyte material can be manufactured by stirring and reacting the starting materials using a ball mill, etc. In addition, the stirring speed and stirring time of the mechanical milling method are not particularly limited, but the faster the stirring speed, the faster the production speed of the sulfide-based solid electrolyte material can be, and the longer the stirring time, the higher the conversion rate of the raw material into the sulfide-based solid electrolyte material can be.

After that, the obtained mixed raw material (sulfide-based solid electrolyte material) is heat-treated at a predetermined temperature and then pulverized to produce a particle-shaped solid electrolyte. In cases where the solid electrolyte has a glass transition point, it may change from amorphous to crystalline through heat treatment.

Next, the solid electrolyte obtained by the above method can be formed into a film using a known film forming method such as an aerosol position method, a cold spray method, a sputtering method, etc., thereby manufacturing a solid electrolyte layer (30). In addition, the solid electrolyte layer (30) can be manufactured by pressurizing solid electrolyte particles. In addition, the solid electrolyte layer (30) can be manufactured by mixing a solid electrolyte, a solvent, and a binder, applying, drying, and pressurizing the solid electrolyte layer (30).

(4) Lamination process

A solid electrolyte layer (30) is placed between a positive electrode (10) and a negative electrode (20), and this is pressurized using, for example, hydrostatic pressure, to obtain an all-solid-state lithium ion secondary battery (100) according to one embodiment.

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

<Charging method for all-solid-state lithium-ion secondary batteries>

Next, a charging method of an all-solid-state lithium ion secondary battery (100) is described.

A charging method of an all-solid-state lithium ion secondary battery (100) according to one embodiment may 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).

At the beginning of charging, lithium may be absorbed into the negative electrode active material layer (24). If charging is performed exceeding the charge capacity of the negative electrode active material layer (24), as shown in FIG. 2, lithium may be precipitated on the back 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 was not present during manufacturing may be formed by this lithium. During discharge, lithium in the negative electrode active material layer (24) and the metal layer (26) may be ionized and move toward the positive electrode (10). Therefore, lithium may be used as the negative electrode active material in the all-solid-state lithium ion secondary battery (100) of the present invention. In addition, since the negative electrode active material layer (24) coats the metal layer (26), it may function as a protective layer for the metal layer (26) and may suppress precipitation and growth of dendritic metal lithium. In this way, short circuit and capacity reduction of the all-solid-state lithium ion secondary battery (100) can be suppressed, and further, 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.

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) as shown in Fig. 2, but may also be formed inside the negative electrode active material layer (24). In addition, 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).

The all-solid-state lithium ion secondary battery (100) of the present invention can be manufactured as a unit cell having a structure of positive electrode/separator/negative electrode, a bicell having a structure of positive electrode/separator/negative electrode/separator/positive electrode, or a laminated battery having a structure of repeating unit cells.

The shape of the all-solid-state lithium ion secondary battery (100) of the present invention is not particularly limited, and examples thereof include coin-shaped, button-shaped, sheet-shaped, stacked, cylindrical, flat, and cone-shaped batteries. In addition, the all-solid-state lithium ion secondary battery (100) can be applied to large batteries used in electric vehicles, etc. For example, the all-solid-state lithium ion secondary battery (100) can be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). In addition, it can be used in fields requiring a large amount of power storage. For example, it can be used in electric bicycles or power tools, etc.

Hereinafter, the present invention will be described in detail by way of examples in order to specifically explain the present invention. However, the examples according to the present invention may be modified in various different forms, and the scope of the present invention should not be construed as being limited to the examples described below. The examples of the present invention are provided in order to more completely explain the present invention to a person having average knowledge in the art.

Manufacturing Example 1: Selection of carbon material sample with oxygen functional group introduced

Various types of carbon materials sold on the market were purchased and the oxygen content contained in each carbon material was analyzed using 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.

<Analysis method>

(1) Analysis device

Using K-Alpha (Thermo Fisher Scientific), a photoelectron spectrometer (XPS or ESCA)

(2) Analysis method

First, the Survey scan spectrum and Narrow scan spectrum were obtained for each sample. The Narrow scan spectrum was measured at 4 points for each location and the average and deviation were calculated.

(3) ESCA common experimental conditions

X-ray source: Monochromated Al Ka (1486.6 eV)

X-ray spot size: 400㎛

Operation mode: CAE (Constant Analyzer Energy) mode

Survey scan: pass energy 200 eV, energy step 1 eV

Narrow scan: scanned mode, pass energy 50 eV, energy step 0.1 eV

Charge compensation: flood gun off

SF: Al THERMO1, ECF: TPP-2M, BG subtraction: Smart

Carbon black sample 1 Carbon black sample 2 Carbon black sample 3 ingredient Average (at%) Deviation Average (at%) Deviation Average (at%) Deviation O 5.2 0.1 2.6 0.2 1.3 0.2 C 94.5 0.1 97.2 0.2 98.3 0.2 S 0.3 0.04 0.3 0.03 0.4 0.04

Example 1 and Comparative Examples 1 to 2: Negative electrode active material slurry manufacturing

6 g of carbon black (Sample 1, Sample 2, or Sample 3) having a particle size (D50) of 40 nm to 60 nm, 2 g of Ag having a particle size (D50) of 40 nm to 60 nm, 9.33 g of PVdF binder (solid content 6%), and 7.19 g of NMP solution were placed in a Thinky mixer container and mixed 12 times at 2000 rpm for 3 minutes each. Thereafter, 5 g of NMP solution was additionally added, and mixing was performed 5 times at 2000 rpm for 3 minutes each to manufacture the negative active material slurry of Example 1 (using carbon black having an oxygen content of 5.2 at%), the negative active material slurry of Comparative Example 1 (using carbon black having an oxygen content of 2.6 at%), and the negative active material slurry of Comparative Example 2 (using carbon black having an oxygen content of 1.3 at%), respectively.

Experimental Example 1: Particle Size Measurement of Carbon-Metal Composites

(1) Separation of carbon-metal composite sample

A portion of the carbon material-metal composite included in the negative electrode active material slurry of Example 1 and Comparative Example 1 was taken and diluted in an NMP solution to prepare an analysis sample.

(2) Analysis equipment

Particle size analysis was performed using a particle size analyzer model name Mastersizer 3000 (Malvem panalytical). Specifically, carbon-metal composite analysis sample 1 (Example 1, including carbon black with an oxygen content of 5.2 at%) and carbon-metal composite analysis sample 2 (including carbon black with an oxygen content of 2.6 at%) prepared in (1) above were placed into the sample inlet of the device so that the laser obscuration was 10-15%, and measurement was performed.

The above-mentioned analysis device is capable of analyzing particle sizes ranging from 0.01㎛ to 3500㎛, and is a particle size analyzer suitable for wet and dry dispersion types through laser diffraction.

(3) Analysis results

The particle size analysis results of the carbon-metal composite analysis samples 1 and 2 are shown in Table 2 and Figure 3 below.

D10(㎛) D50(㎛) D90(㎛) Carbon-metal composite analysis sample 1 (containing carbon black with oxygen content: 5.2 at%) 0.019 0.261 0.623 Carbon-metal composite analysis sample 2 (containing carbon black with oxygen content of 2.6 at%) 3.14 8.26 18.3

From the results in Table 2 above, it can be seen that the particle size of the carbon material-metal composite including carbon black having an oxygen content of 5.2 at% is significantly smaller than the particle size of the carbon material-metal composite including carbon black having an oxygen content of 2.6 at%.

In addition, according to the analysis results shown in Fig. 3, the maximum particle size of the carbon material-metal composite including carbon black having an oxygen content of 5.2 at% is 1 μm or less, which is significantly smaller than the particle size of the carbon material-metal composite including carbon black having an oxygen content of 2.6 at%.

Experimental Example 2: Measurement of rheological properties of negative electrode active material slurry

The rheological properties of the negative active material slurry of Example 1 (using carbon black having an oxygen content of 5.2 at%) and the negative active material slurry of Comparative Example 1 (using carbon black having an oxygen content of 2.6 at%) were measured using a Rheometer, model number DHR-1 (TA instrument).

At this time, a 40 mm parallel plate geometry was used, and the viscosity of the slurry according to shear was measured through a flow test. The oscillation frequency test was performed before and after the viscosity measurement.

The results of the above rheological property measurements are shown in Fig. 4.

For slurries with good dispersibility, the viscosity decrease rate with increasing shear is similar, and the viscosity change after decreasing shear is also similar. In flow tests, viscosity curvature occurs because the particles are not released, so large particles impede the flow of other small particles.

As confirmed in Fig. 4, the slurry of Example 1 did not show an inflection point, and the viscosity change when the shear rate increased and then decreased was also shown to be almost similar. Therefore, from these results, it can be seen that the slurry of Example 1 has excellent dispersibility.

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. This result means that agglomeration occurred in the slurry.

In general, when the viscosity at a shear rate of 2.5 s ^-1 is 10 Pa s or less, the slurry has excellent coatability. Under these criteria, the slurry of Example 1 was confirmed to have excellent coatability with a viscosity of 4.134 Pa s at a shear rate of 2.5 s ^-1 , whereas the slurry of Comparative Example 1 was confirmed to have poor coatability with a viscosity of 52.546 Pa s at a shear rate of 2.5 s ^-1 .

Example 2 and Comparative Examples 3 to 5: Preparation of cathode

Each of the negative active material slurries manufactured in Example 1 and Comparative Examples 1 and 2 was coated on SUS foil to a thickness of 10 μm and dried to obtain the slurries of Example 2 (using carbon black having an oxygen content of 5.2 at%), Comparative Example 3 (using carbon black having an oxygen content of 2.6 at%), Comparative Example 4 (using carbon black having an oxygen content of 1.3 at%), and Comparative Example 5 (using carbon black having an oxygen content of 2.4 at%). The cathode was manufactured.

Experimental Example 3: Measurement of oxygen content in the negative electrode active material layer

The oxygen content included in the negative electrode active material layer laminated on the negative electrodes manufactured in Example 2, Comparative Example 3, and Comparative Example 4 was analyzed by the following method, and the results are shown in Table 3, Figures 7 and 8 below.

<Analysis method>

(1) Analysis device

Using a Nexsa4 (Thermo Fisher Scientific), a photoelectron spectrometer (XPS or ESCA)

(2) Analysis method

First, Survey scan spectrum and Narrow scan spectrum were obtained for each sample. The Narrow scan spectrum was measured at 4 points for each location and the average and deviation were obtained. Next, the Survey scan spectrum and Narrow scan spectrum were obtained while performing the Depth profile. The Depth profile was performed for up to 5000 seconds using Monatomic Ar ions.

(3) Experimental and data processing conditions

X-ray source: Monochromated Al Ka (1486.6 eV)

X-ray spot size: 400㎛

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 _sample )

Operation mode: CAE (Constant Analyzer Energy) 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

<Analysis Results>

(1) Element composition ratio of the surface of the negative electrode active material layer

The surface element composition ratio of the negative electrode active material layer was measured as shown in Table 3 below.

element Example 2 Comparative Example 3 Comparative Example 4 average
(at%) Deviation average
(at%) Deviation average
(at%) Deviation C 79.1 0.1 81.5 0.4 81.2 0.1 O 2.7 0.02 1.7 0.04 1.1 0.03 F 17.2 0.1 15.5 0.5 16.6 0.1 Ag 0.8 0.01 1.0 0.02 0.8 0.01 S 0.2 0.01 0.3 0.01 0.3 0.01 total 100 100 100

From the results in Table 3 above, it can be seen that the content of oxygen included in the surface of the negative electrode active material layer is proportional to the content of oxygen included in the carbon material included 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) included 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 similar in all of the negative electrode active material layers manufactured in Example 2, Comparative Example 3, and Comparative Example 4.

Figure 8 shows the results of peak deconvolution in the O 1s spectra for oxygen included in the negative active material layers manufactured in Example 2, Comparative Example 3, and Comparative Example 4. From the spectra, it can be confirmed that as the content of oxygen included in the carbon material constituting the negative active material layer increases (Example 2 > Comparative Example 3 > Comparative Example 4), the metal oxides peak increases. The metal oxides peak appears to be due to the combination of oxygen on the surface of the carbon material and Ag, which means that the more oxygen there is on the surface of the carbon material, the better the dispersibility of Ag.

If the above figure 8 is expressed numerically, it is as shown in Table 4 below.

O 1s peak deconvolution(%) Metal oxides OC= O O -C=O, hydroxides, sulfates(S=O) Example 2 6.8 29.8 63.4 Comparative Example 3 1.1 33.6 65.4 Comparative Example 4 0.4 35.3 64.2

Experimental Example 4: Measurement of Surface Roughness of Negative Electrode Active Material Layer

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

Specifically, the cathode for measuring illuminance was prepared in an appropriate size. At this time, three or more samples were prepared for the same electrode to ensure data reliability and to check the illuminance deviation within the sample. These samples were attached to a slide glass using double-sided tape to prevent them from being wrinkled.

After placing the slide glass with the prepared sample attached on the measurement stage, the focus was adjusted and the illuminance was measured.

The SEM images of the negative electrode active material layers laminated on the negative electrodes manufactured in Example 2 and Comparative Example 5 are shown in Fig. 9, and the surface roughness measurement results are shown in Table 5 and Fig. 10 below.

Sa(㎛) Sz(㎛) Spc(mm ^-1 ) Sdr Example 2 0.073 1.377 994 0.0198 Comparative Example 5 0.528 9.737 2408 0.2150

Experimental Example 5: Density and Porosity Analysis of 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.

Density of negative active material layer (g/ml) Porosity (%) Example 2 2.389 64.5 Comparative Example 3 2.389 72.3 Comparative Example 4 2.389 73.3 Comparative Example 5 2.389 77.8

Manufacturing of all-solid-state lithium-ion secondary batteries of Example 3 and Comparative Examples 6 to 7

As the positive electrode, a positive electrode with a positive electrode active material loaded at 5 mAh/ ^cm2 on the current collector is used, and as the negative electrode, a cathode manufactured in Example 2 and Comparative Examples 3 to 4 is used. Pouch-type monocells of Example 3, Comparative Example 6, and Comparative Example 7 were manufactured using a cathode and a sulfide-based solid-state electrolyte (LPSCl composition) as an electrolyte.

Experimental Example 6: Battery Characteristics Evaluation

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

Charge conditions: 0.33C, 4.25V CC/CV, 0.1C cut-off

Discharge conditions: 0.33C, 3.0V, CC

From Fig. 5, it can be confirmed that the battery of Example 3 is operated without a significant decrease in cell capacity as the cycle progresses.

In addition, from FIG. 6, it can be confirmed that the cycle characteristics of the battery of Example 3 are significantly superior to those of the batteries of Comparative Examples 6 and 7.

Claims (18)

Contains a collector and a negative electrode active material layer,
The above negative active material layer comprises one or more active material layers containing 2 to 10 at% of oxygen,
The at least one active material layer comprises 60 to 80 wt% of amorphous carbon particles having 3 to 6 at% of oxygen on the surface, 10 to 30 wt% of metal particles, and 3 to 20 wt% of a binder,
An anode for an anodeless battery, wherein metallic lithium is deposited between the negative electrode active material layer and the negative electrode active material layer and the current collector during charging, and the metallic lithium is ionized and moves toward the positive electrode during discharge. delete delete delete delete In the first paragraph,
A cathode characterized in that the oxygen exists in a form included in a functional group bonded to carbon material particles. In Article 6,
A cathode characterized in that the functional group includes at least one 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. In the first paragraph,
A negative electrode, characterized in that the metal particles are particles that form an alloy with lithium. In Article 8,
A cathode, characterized in that the metal particles are at least one type of particle selected from silver (Ag), gold, platinum, palladium, silicon, aluminum, bismuth, tin, indium, and zinc. In Article 9,
A cathode characterized in that the metal particles include silver (Ag). In the first paragraph,
The above one or more active material layers have the following surface roughness:
0.01 ㎛ ≤ Sa ≤ 0.3 ㎛
0.5 ㎛ ≤ Sz ≤ 5 ㎛
500 mm ^-1 ≤ Spc ≤ 1500 mm ^-1
0.005 ≤ Sdr ≤ 0.15. In the first paragraph,
A negative electrode, wherein the one or more active material layers have a porosity of 55 to 70%. In the first paragraph,
A cathode characterized in that the carbon material particles and metal particles are included in the form of a carbon material-metal composite. In Article 13,
A cathode characterized in that the particle size (D50) of the carbon material-metal composite is 0.1 ㎛ to 0.5 ㎛. In Article 14,
A cathode characterized in that the maximum particle size of the carbon material-metal composite is 3㎛ or less. A lithium ion secondary battery comprising the negative electrode of claim 1; the positive electrode; and an electrolyte disposed between the negative electrode and the positive electrode. In Article 16,
A lithium ion secondary battery, characterized in that the electrolyte comprises a sulfide-based solid electrolyte. In Article 17,
A lithium ion secondary battery, characterized in that the above lithium ion secondary battery is an anodeless battery.