Anode and lithium ion secondary battery comprising anode

Abstract

The present invention provides an anode and a lithium ion secondary battery comprising the anode, the anode comprising: a current collector and an active material layer, wherein the active material layer comprises carbon material particles and metal sulfide particles, and the metal sulfide comprises at least one selected from the group consisting of Ag2S, MnS, and GeS.

Description

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

[0001] This application claims the benefit of priority to Korean Patent Application No. 10-2023-0118217, filed September 6, 2023, and Korean Patent Application No. 10-2024-0120636, filed September 5, 2024, the entire contents of which are incorporated herein by reference.

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

[0003] All-solid-state secondary batteries utilizing solid electrolytes have recently attracted attention. To improve the energy density of these all-solid-state secondary batteries, the use of lithium as an anode active material has been proposed. The capacity density (capacity per unit weight) of lithium is approximately ten times that of graphite, a commonly used anode material. Therefore, using lithium as an anode active material allows for thinner all-solid-state secondary batteries while increasing their output.

[0004] As an all-solid-state lithium-ion secondary battery, 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.

[0005] 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.

[0006] The above negative active material layer is formed of carbon material and metal material such as Ag, and development of various materials is required to improve the operating characteristics and life characteristics of the battery.

[0007] [Prior Art Literature]

[0008] [Patent Document]

[0009] Republic of Korea Publication Patent No. 10-2020-0052707

[0010]

[0011] The purpose of the present invention is to provide a negative electrode capable of improving the operating characteristics and life characteristics of a battery and a lithium ion secondary battery including the same.

[0012] In order to achieve the above purpose, the present invention

[0013] Contains the entire collector and active material layer,

[0014] The above active material layer includes carbon particles and metal sulfide particles,

[0015] The above metal sulfide provides a cathode comprising at least one selected from the group consisting of Ag2S, MnS, and GeS.

[0016]

[0017] In addition, the present invention

[0018] 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.

[0019] The negative electrode of the present invention includes a negative electrode active material layer in the form of a mixture of carbon material particles and metal sulfide particles, thereby providing an effect of improving the operating characteristics and life characteristics of a battery.

[0020] In addition, the lithium ion secondary battery of the present invention provides excellent driving characteristics and life characteristics by including the negative electrode active material layer.

[0021] Figures 1 and 2 are cross-sectional views schematically showing the structure of a lithium ion secondary battery of the present invention.

[0022] Hereinafter, the present invention will be described in more detail to help understand the present invention.

[0023] The terms and words used in this specification and claims should not be construed as limited to their conventional or dictionary meanings. Rather, they should be construed with meanings and concepts consistent with the technical spirit of the present invention, based on the principle that the inventor can appropriately define the concept of a term to best describe his or her invention. Furthermore, the terminology used in this specification is used merely to describe exemplary embodiments and is not intended to limit the present invention. The singular expression "a" includes plural expressions unless the context clearly indicates otherwise.

[0024] When a component is referred to as being "connected, provided, or installed" to another component, it should be understood that it may be directly connected or installed to that other component, but there may also be other components in between. Conversely, when a component is referred to as being "directly connected or installed" to another component, it should be understood that there are no other components in between. Similarly, other expressions describing the relationship between components, such as "on top of" and "directly on top of," "between" and "directly between," or "adjacent to" and "directly adjacent to," should be interpreted similarly.

[0025] The term "combination" in this specification includes mixtures, alloys, reaction products, etc., unless specifically stated otherwise.

[0026]

[0027] The negative electrode of the present invention includes a current collector and an active material layer,

[0028] The above active material layer includes carbon particles and metal sulfide particles,

[0029] The above metal sulfide is characterized in that it includes at least one selected from the group consisting of Ag2S, MnS, and GeS.

[0030]

[0031] In one embodiment of the present invention, the metal sulfide particles may be included in an amount of 10 to 50 parts by weight, preferably 12 to 28 parts by weight, and more preferably 15 to 25 parts by weight, based on 100 parts by weight of the combined weight of the carbon material particles and the metal sulfide particles.

[0032] In the above, if the metal sulfide is included in an amount of less than 10 parts by weight, it is not sufficient to form an alloy with lithium, so the advantage of lowering the alloying activation energy by adding the metal sulfide cannot be realized. In addition, if it exceeds 50 parts by weight, the storage capacity of lithium is reduced, which causes problems such as a decrease in overall capacity and a decrease in high-rate discharge characteristics, which is not desirable.

[0033]

[0034] In one embodiment of the present invention, the negative electrode may include metal sulfide particles before being assembled into a battery. That is, in the present invention, the negative electrode may include metal sulfide during the preparation of the negative electrode active material and / or during the preparation of the composition (e.g., slurry) for forming the negative electrode active material layer.

[0035] In one embodiment of the present invention, the cathode may not include a metal in a base form other than a metal sulfide form.

[0036]

[0037] In one embodiment of the present invention, the carbon material particles may be, for example, amorphous carbon material particles. However, the carbon material particles are not limited to amorphous particles. Specific examples of the amorphous carbon material include, but are not limited to, carbon black such as acetylene black, furnace black, and Ketjen black, graphene, or combinations thereof.

[0038] 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 precipitate within 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.

[0039] 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.

[0040]

[0041] At least one selected from the group consisting of Ag2S, MnS, and GeS, which are metal sulfides used in the present invention, has the characteristic of providing superior effects compared to TiS2, CoS, NiS, FeS, MoS2, CuS, Cu2S, WS2, etc. that have been used previously.

[0042] In one embodiment of the present invention, the carbon material particles and metal sulfide particles may be included in a randomly mixed form.

[0043]

[0044] In one embodiment of the present invention, the carbon material particles may be used having a particle size (D50) of 10 nm to 150 nm, preferably 20 nm to 100 nm, and more preferably 20 nm to 60 nm.

[0045] In one embodiment of the present invention, the metal sulfide particles may be used having a particle size (D50) of 5 nm to 100 nm, preferably 5 nm to 80 nm, and more preferably 10 nm to 60 nm.

[0046] In one embodiment of the present invention, the ratio of the carbon material particle size (D50) to the metal sulfide particle size (D50) may be 1: 0.03 to 1.5, 1: 0.1 to 0.7, or 1: 0.2 to 0.7. If the particle size ratio of the metal sulfide particles exceeds 1.5, the dispersibility in the electrode slurry is inhibited, the coatability is reduced, and the uniformity of the electrode is problematic. In addition, if the particle size ratio of the metal sulfide particles is less than 0.03, the specific surface area of ​​the carbon material particles and the metal sulfide particles is greatly increased, which greatly increases the amount of binder and solvent used, which may cause problems such as a decrease in capacity and an increase in resistance, which is not preferable.

[0047] In the present invention, the particle size can be measured using a particle size analyzer. For example, it can be measured using a Mastersizer 3000 (Malvem panalytical) device.

[0048]

[0049] In one embodiment of the present invention, the carbon material particles may be carbon material particles containing 3 to 10 at% of oxygen based on the total elements contained in the carbon material particles. If the oxygen content is less than 3 at%, the surface roughness of the active material layer is lowered, which is undesirable. If the oxygen content exceeds 10 at%, the performance of the battery is lowered due to a side reaction with the solid electrolyte, which is undesirable.

[0050] 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 and the upper limit. Specifically, the oxygen content may be more preferably 5 to 10 at%.

[0051] 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.

[0052] 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 can be treated with an acid and reacted while stirring at a temperature of 25°C to 60°C to introduce oxygen functional groups to the surface of the carbon material. The type of acid is not particularly limited, and any acid capable of introducing oxygen functional groups to the surface of the carbon material can be used. Examples of the acid include sulfuric acid, nitric acid, or mixtures thereof, and an oxidizing agent such as potassium permanganate can also be used.

[0053] The above carbon material containing oxygen can be manufactured and used directly or purchased and used.

[0054] The content of oxygen and other elements 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.

[0055] In one embodiment of the present invention, the components of the carbon material particles containing oxygen may be configured as follows, for example.

[0056] Carbon black sample 1 Carbon black sample 2 Carbon black sample 3 Component average (at%) deviation average (at%) deviation average (at%) deviation O 5.2 0.12 6 0.2 1.3 0.2 C 9 4.5 0.1 9 7.2 0.2 9 8.3 0.2 S 0.3 0.0 4 0.3 0.0 3 0.4 0.04

[0057] In one embodiment of the present invention, the oxygen may be present on the surface of the carbon material particles. The surface does not only refer to the outer surface of the carbon material particles, but also includes the surface of the pores, if pores exist.

[0058] In one embodiment of the present invention, the active material layer may include 60 to 80 wt% of carbon particles, 10 to 30 wt% of metal sulfide particles, and 3 to 20 wt% of a binder. Examples of the binder include resin materials such as styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. The binder may be composed of one or more types selected from these resin materials.

[0059] The above active material layer may additionally contain 5 to 20 wt% of a conductive material. The conductive material exemplified in the positive electrode below may be used as the conductive material.

[0060]

[0061] In one embodiment of the present invention, the carbon material particles and metal sulfide particles may be included in the form of a carbon material-metal sulfide composite.

[0062] In anode-less batteries, the negative active material layer is formed as a very thin film with a micro-thickness. However, conventional active material composites have the problem of being very difficult to form with a small particle size. In other words, if the particle size of the active material 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 this decrease in surface roughness acts as a cause of deterioration in the operating characteristics of the battery.

[0063] The present invention provides an effect that dramatically improves the above-mentioned problems of the prior art. That is, the carbon material-metal sulfide composite of the present invention forms a carbon material-metal sulfide 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 oxygen at 3 at% or more, so that it mixes well with the metal sulfide particles, and is uniformly distributed with the metal sulfide particles. Therefore, it is possible to manufacture a carbon material-metal sulfide composite with excellent component uniformity. In addition, for the above reasons, it is possible to manufacture a carbon material-metal sulfide composite having a small and uniform particle size.

[0064] In one embodiment of the present invention, the carbon material-metal sulfide composite may be formed by at least one bond selected from a chemical bond between carbon material particles and metal sulfide particles, a van der Waals bond between carbon material particles and metal sulfide particles, and a bond between carbon material particles and metal sulfide particles via a binder. The chemical bond may be a bond between the metal sulfide particles and oxygen contained in the carbon material.

[0065] In one embodiment of the present invention, the carbon material-metal sulfide composite may include 60 to 80 wt% of carbon material, 10 to 30 wt% of metal sulfide, and 3 to 20 wt% of binder based on the total weight.

[0066] The above binder can be used by dissolving it in a solvent together with carbon material particles and metal sulfide particles during wet manufacturing of a carbon material-metal sulfide composite, in which case the binder can be included in the carbon material-metal sulfide composite.

[0067] In one embodiment of the present invention, the particle size (D50) of the carbon material-metal sulfide 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.

[0068] Additionally, the maximum particle size of the carbon material-metal sulfide composite may be 3 ㎛ or less, 2 ㎛ or less, 1.5 ㎛ or less, or 1 ㎛ or less.

[0069] If the particle size of the carbon material-metal sulfide composite is too large compared to the micro-thick film, it is difficult to form a negative electrode active material layer with excellent surface roughness, and accordingly, the operating characteristics of the battery are also deteriorated. Therefore, it is very important to manufacture the carbon material-metal sulfide composite with a small particle size.

[0070] 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.

[0071] 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.

[0072] For example, if a carbon material-metal sulfide 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.

[0073] When the maximum particle size of the above carbon material-metal sulfide composite is 3㎛ or less, the surface roughness improvement effect can be more clearly achieved, 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.

[0074] The particle size of the above carbon material-metal sulfide composite can be measured using a particle size analyzer. For example, it can be measured using a Mastersizer 3000 (Malvem panalytical) instrument.

[0075]

[0076] In addition, the present invention

[0077] 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.

[0078] The above lithium ion secondary battery provides improved driving characteristics and life characteristics by including the negative electrode active material layer of the present invention.

[0079] In one embodiment of the present invention, the solid electrolyte may be a sulfide-based solid electrolyte.

[0080] In one embodiment of the present invention, the secondary battery may include a metal sulfide in which the sulfur content is increased by reacting the sulfur included in the sulfide-based solid electrolyte with the metal sulfide included in the negative electrode.

[0081] In one embodiment of the present invention, the lithium ion secondary battery may be an anodeless battery.

[0082]

[0083] Hereinafter, embodiments of the present invention are exemplified in more detail.

[0084] <Composition of an all-solid-state lithium-ion secondary battery>

[0085] 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.

[0086] 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 moving lithium ions between a positive electrode (10) and a negative electrode (20). Specifically, as shown in Fig. 1, this all-solid-state lithium-ion secondary battery (100) is composed of a positive electrode (10), a negative electrode (20), and a solid electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20).

[0087]

[0088] (1) Bipolar

[0089] 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 sequentially toward the negative electrode (20).

[0090] The positive electrode current collector (12) may be plate-shaped or foil-shaped. The positive electrode current collector (12) may be, for example, one type of metal selected from indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, and lithium, or an alloy of two or more types of metals.

[0091] The cathode active material layer (14) can reversibly store and release lithium ions. The cathode active material layer (14) can include a cathode active material and a solid electrolyte.

[0092] The above cathode active material may be a compound capable of insertion / de-insertion of lithium. Examples of the compound capable of insertion / de-insertion of lithium include Li a A 1-b B' b D'2 (in the above formula, 0.90≤a≤1.8, and 0≤b≤0.5); Li a E1- b B' b O 2-c D' c (In the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05); LiE 2-b B' b O 4-c D' c (In the above formula, 0≤b≤0.5, 0≤c≤0.05); Li a Ni 1-b-c Co b B' c D' α (In the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Co b B' c O 2-α F' α(In the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni 1-b-c Mn b B' c D' α (In the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α≤2); Li a Ni 1-b-c Mn b B' c O 2-α F' α (In the above formula, 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, 0<α<2); Li a Ni b E c G d O2 (in the above formula, 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0.001≤d≤0.1); Li a Ni b Co c Mn d G e O2 (in the above formula, 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, 0≤d≤0.5, 0.001≤e≤0.1); Li a NiG b O2 (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li a CoG b O2 (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li a MnG b O2 (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); Li a Mn2G b O4 (in the above formula, 0.90≤a≤1.8, 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0≤f≤2); Li (3-f) Fe2(PO4)3(0≤f≤2); and LiFePO4; Li4Ti5O 12(LTO); can be expressed by any one of the chemical formulas.

[0093] 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.

[0094] 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 aluminumate (hereinafter referred to as NCA), lithium nickel cobalt manganese (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 type selected from these compounds as the positive electrode active material, or may include two or more types.

[0095] The above-described positive electrode active material may include a lithium salt of a transition metal oxide having a layered rock salt structure among the lithium salts described above. Here, the “layered rock salt structure” refers to a structure in which oxygen atomic layers and metal atomic layers are alternately and regularly arranged in the direction of the cubic rock salt structure, and as a result, each atomic layer forms a two-dimensional plane. In addition, the “cubic rock salt structure” refers to a sodium chloride structure, which is a type of crystal structure. For example, the “cubic rock salt structure” refers to a structure in which face-centered cubic lattices in which cations and anions are respectively formed are arranged with a displacement of half of the corners of the unit cell.

[0096] Lithium salts of transition metal oxides having this layered rock salt structure include, for example, LiNi x Co y Al z O2(NCA) or LiNi x Co y Mn z It may be a ternary lithium transition metal oxide such as O2(NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1). The cathode active material layer (14) may include a lithium salt of a 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).

[0097] Here, examples of the shape of the positive electrode active material include spherical, elliptical, and spherical particle shapes. Furthermore, the particle size of the positive electrode active material is not particularly limited, and may be within a range applicable to positive electrode materials for typical all-solid-state lithium-ion secondary batteries. Furthermore, 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 for typical all-solid-state lithium-ion secondary batteries.

[0098] Of course, it is also possible to use a compound having a coating layer on the surface of the compound, or it is also possible to use a mixture of the compound and a compound having a 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. 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 and does not adversely affect the properties of the positive electrode active material (e.g., spray coating, dipping, etc.). Since this is well understood by those working in this field, a detailed description thereof will be omitted.

[0099] Specific examples of the above coating layer include Li2O-ZrO2, etc.

[0100] The solid electrolyte included in the positive electrode active material layer (14) may be the same as or different from the solid electrolyte included in the solid electrolyte layer (30) described later.

[0101] In addition, the cathode active material layer (14) may be a material that appropriately mixes not only the cathode active material and solid electrolyte described above, but also additives such as a conductive agent, a binder, a filler, a dispersant, or an ion conductive auxiliary agent.

[0102] Examples of the conductive material include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, or metal powder. Examples of the binder include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. In addition, known materials commonly used in electrodes of all-solid-state lithium-ion secondary batteries can be used as the filler, dispersant, or ion conductive auxiliary agent.

[0103]

[0104] (2) Cathode

[0105] 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).

[0106] 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, i.e., does not form any alloys or compounds 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 type of these metals, or may be composed of an alloy of two or more types of metals or a clad material.

[0107] The negative electrode active material layer (24) may not contain lithium between the negative electrode current collector (22), the negative electrode active material layer (24), or the negative electrode active material layer (24) and the solid electrolyte layer (30) in the initial state or the state after complete discharge. As described below, when the all-solid-state lithium ion secondary battery (100) according to one embodiment is overcharged, the active material contained in the negative electrode active material layer (24) and lithium ions moved from the positive electrode (10) 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 disposed between the negative electrode current collector (22) and the negative electrode active material layer (24), inside the negative electrode active material layer (24), or 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).

[0108] The above-described negative electrode active material layer (24) may include carbon particles, metal sulfide particles, and a binder. By including the binder (binding agent), 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.

[0109] Additionally, 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 conductive agents. Specific examples of the additives are the same as those described for the positive electrode described above.

[0110] The total thickness of the negative electrode active material layer (24) is not particularly limited, but may be 1 ㎛ to 100 ㎛, or 10 ㎛ to 60 ㎛. If the thickness of the negative electrode 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 electrode active material layer (24) exceeds 100 ㎛, the resistance of the negative electrode active material layer (24) is high, resulting in the performance of the all-solid-state secondary battery not being sufficiently improved. By using the above-described binder, the thickness of the negative electrode active material layer (24) can be easily secured at an appropriate level.

[0111] 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 disposed between the negative electrode current collector (22) and the negative electrode active material layer.

[0112] 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).

[0113] Materials capable of forming an alloy with lithium metal used in the film may include silicon, magnesium, aluminum, lead, silver, tin, or a combination thereof. Materials 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 small within a range that does not affect the electrochemical properties of the electrode and / or the redox potential of the electrode. The film may be applied flatly on the negative electrode current collector (22) to prevent cracking during the charging 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 plating.

[0114] 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.

[0115]

[0116] (3) Solid electrolyte layer

[0117] A solid electrolyte layer (30) is disposed between the positive electrode (10) and the negative electrode (20) (e.g., 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.

[0118] The above sulfide-based solid electrolyte is 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, 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.

[0119] The above sulfide-based solid electrolyte may include a solid electrolyte represented by the following chemical formula 1:

[0120] <Chemical Formula 1>

[0121] Li x M' y PS z A w

[0122] In the above chemical formula 1,

[0123] x, y, z, w are independently 0 to 6;

[0124] M' is one or more of As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, or Ta;

[0125] A is one or more of F, Cl, Br, or I.

[0126] 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 Li2S-P2S5 can be used. When one containing Li2S-P2S5 is used as a sulfide-based solid electrolyte material, the mixing molar ratio of Li2S and P2S5 can be selected in the range of, for example, Li2S:P2S5 = 50:50 to 90:10.

[0127] Additionally, solid electrolytes can be amorphous or crystalline, or a mixture of amorphous and crystalline states.

[0128] 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 materials constituting the binder in the positive electrode active material layer (14) and the negative electrode active material layer (24).

[0129]

[0130] (4) Composition of all-solid-state lithium-ion secondary battery

[0131] 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 a negative electrode (20) in this order, as illustrated in FIG. 1.

[0132]

[0133] <Method for manufacturing an all-solid-state lithium-ion secondary battery>

[0134] 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.

[0135]

[0136] (1) Bipolar manufacturing process

[0137] The positive electrode manufacturing process is explained as follows, for example. First, materials constituting the positive electrode active material layer (14) (positive electrode active material, binder, etc.) are added to a non-polar solvent to produce a slurry (or paste). Next, the obtained slurry is applied onto the prepared positive electrode current collector (12). This is dried to obtain a laminate. Next, the obtained laminate is pressed using, for example, hydrostatic pressure to obtain a positive electrode (10). In this case, the pressing process is omitted.

[0138]

[0139] (2) Cathode manufacturing process

[0140] The negative electrode manufacturing process is explained as follows, for example. First, materials (carbon particles, metal sulfide particles, binder, etc.) constituting the negative electrode active material layer (24) are added to a polar or non-polar solvent to prepare a slurry (paste may also be used). Next, the obtained slurry is applied onto the prepared negative electrode current collector (22) to form a negative electrode active material layer.

[0141] If the above negative active material layer additionally includes one or more layers, additional layers can be laminated in the same manner as above.

[0142] Next, the laminate obtained by the above method is pressed using, for example, hydrostatic pressure to produce a negative electrode (20). In addition, the pressing process may be omitted. In addition, the method for 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.

[0143] The method of forming a two-layer negative electrode active material layer has been described above, but even when 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.

[0144]

[0145] (3) Solid electrolyte layer manufacturing process

[0146] The solid electrolyte layer (30) can be manufactured using a solid electrolyte including, for example, a sulfide-based solid electrolyte material.

[0147] First, the starting materials (e.g., Li2S, P2S5, etc.) are processed by a melt-quenching method or a mechanical milling method to obtain a sulfide-based solid electrolyte material. For example, when the melt-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 rapidly cooled to produce a sulfide-based solid electrolyte material. In addition, the reaction temperature of the mixture of Li2S and P2S5 may be 400°C to 1000°C, for example, 800°C to 900°C. In addition, the reaction time may be 0.1 hour to 12 hours, for example, 1 hour to 12 hours. In addition, the quenching temperature of the reactants may be 10°C or lower, for example, 0°C or lower, and the quenching rate may be typically 1°C / sec to 10,000°C / sec, for example, 1°C / sec to 1000°C / sec.

[0148] In addition, when using a mechanical milling method, a sulfide-based solid electrolyte material can be manufactured by stirring and reacting the starting raw 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 materials into the sulfide-based solid electrolyte material can be.

[0149] Thereafter, the obtained mixed raw material (sulfide-based solid electrolyte material) is heat-treated at a predetermined temperature and then pulverized to produce a solid electrolyte in particle form. In cases where the solid electrolyte has a glass transition point, it may change from an amorphous state to a crystalline state through heat treatment.

[0150] 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, or a sputtering method, 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).

[0151]

[0152] (4) Lamination process

[0153] A solid electrolyte layer (30) is placed between the positive electrode (10) and the 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.

[0154] 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.

[0155]

[0156] <Charging method for all-solid-state lithium-ion secondary batteries>

[0157] Next, a charging method of an all-solid-state lithium-ion secondary battery (100) is described.

[0158] A charging method of an all-solid-state lithium ion secondary battery (100) according to an 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).

[0159] At the initial stage of charging, lithium may be absorbed into the negative electrode active material layer (24). If charging exceeds 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 did not exist 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 functions as a protective layer for the metal layer (26) and can suppress the precipitation and growth of dendritic metallic 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.

[0160] 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).

[0161] The all-solid-state lithium ion secondary battery (100) of the present invention may be manufactured as a unit cell having a structure of positive electrode / separator / negative electrode, a bi-cell having a structure of positive electrode / separator / negative electrode / separator / positive electrode, or a laminated battery having a structure of repeating unit cells.

[0162] 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. Furthermore, the all-solid-state lithium ion secondary battery (100) can be applied to large-scale 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). Furthermore, 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.

[0163] Hereinafter, the present invention will be described in detail with reference to examples 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 to more completely explain the present invention to those of average skill in the art.

[0164]

[0165] Example 1: Preparation of negative electrode active material slurry

[0166] 6 g of carbon black having a particle size (D50) of 41 nm, 2 g of Ag2S having a particle size (D50) of 10 nm to 60 nm, 9.33 g of PVdF binder (solid content 6%), and 6 g of NMP solution were placed in a Thinky mixer container and mixed 12 times for 3 minutes each at 1800 rpm. Thereafter, 6 g of NMP solution was additionally added and mixed 5 times for 3 minutes each at 1800 rpm to prepare a slurry of the negative active material of Example 1.

[0167]

[0168] Example 2: Preparation of negative electrode active material slurry

[0169] In the above Example 1, a negative electrode active material slurry was prepared in the same manner as in Example 1, except that 2 g of GeS having a particle size of 10 nm to 60 nm was used instead of 2 g of Ag2S.

[0170]

[0171] Example 3: Preparation of negative electrode active material slurry

[0172] In the above Example 1, a negative electrode active material slurry was prepared in the same manner as in Example 1, except that 2 g of MnS having a size of 10 nm to 60 nm was used instead of 2 g of Ag2S.

[0173]

[0174] Comparative Example 1: Preparation of negative electrode active material slurry

[0175] In the above Example 1, a slurry of a negative active material of Comparative Example 1 was prepared in the same manner as Example 1, except that 2 g of Ag having a particle size (D50) of 40 nm to 100 nm was used instead of 2 g of Ag2S.

[0176]

[0177] Examples 4 to 6 and Comparative Example 2: Preparation of cathode

[0178] Each negative active material slurry manufactured in Examples 1 to 3 and Comparative Example 1 was blade-coated on SUS foil to a thickness of 10 μm and dried to obtain a slurry having a capacity of 0.9 mAh / cm in Examples 4 to 6 and Comparative Example 2. 2 ) was manufactured.

[0179]

[0180] Manufacturing of all-solid-state lithium-ion secondary batteries of Examples 7 to 9 and Comparative Example 3

[0181] As a cathode, NCM and argyrodite electrolyte were mixed at a weight ratio of 5.7:1 to form a cathode active material, and 6 mAh / cm was applied to the current collector. 2The pouch-type monocells of Examples 7 to 9 and Comparative Example 3 were manufactured using the positive electrode loaded with , the negative electrode manufactured in Examples 4 to 6 and Comparative Example 2 as the cathode, and the sulfide-based all-solid-state electrolyte (LPSCl composition) as the electrolyte.

[0182]

[0183] Experimental Example 1: Battery Characteristic Evaluation

[0184] The following experiments were conducted on the pouch-type monocells manufactured in Examples 7 to 8 and Comparative Example 3, and the results are shown in Table 2 below.

[0185] (1) Initial efficiency evaluation

[0186] The pouch-type monocell was charged at a rate (C-rate) of 0.1C until the voltage reached 4.25 V (vs. Li), and then cut-off at a rate of 0.05C while maintaining 4.25 V (vs. Li). Subsequently, it was discharged at a rate (C-rate) of 0.1C until the voltage reached 3.0 V (vs. Li) (1st cycle). The initial efficiency was calculated as discharge capacity / charge capacity Ⅹ 100 (%).

[0187] (2) Discharge capacity evaluation

[0188] The pouch-type monocell was operated at an operating voltage range of 4.25 V to 3.0 V and an operating temperature of 60°C to evaluate its cycle characteristics.

[0189] (3) Life performance evaluation

[0190] The pouch-type monocell was charged at an operating temperature of 60°C at a rate (C-rate) of 0.33C until the voltage reached 4.25 V (vs. Li), and then cut-off was achieved at a rate of 0.1C while maintaining 4.25 V (vs. Li). Subsequently, the cell was discharged at a rate (C-rate) of 0.33C until the voltage reached 3.0 V (vs. Li) (1st cycle). The above charge-discharge test was repeated 20 cycles, and the capacity retention rate of the discharge capacity was measured.

[0191] Battery active material material Initial efficiency (%) Discharge capacity (%) Capacity retention @ 20 cycle (%) 0.1 C 0.33 C 0.5 C 1.0 C Example 7 Example 1 Manufactured active material 87.8 100 98.89 7.5 93.89 7.21 Example 8 Example 2 Manufactured active material 86.3 100 98.3 96.0 90.6 95.12 Comparative example 3 Comparative example 1 Manufactured active material 86 100 95.73 92.21 82.75 93.20

Claims

1. Includes a collector and an active material layer, The above active material layer includes carbon particles and metal sulfide particles, A cathode comprising at least one metal sulfide selected from the group consisting of Ag2S, MnS, and GeS.

2. In paragraph 1, A cathode characterized in that the metal sulfide particles are included in an amount of 10 to 50 parts by weight based on 100 parts by weight of the combined weight of carbon material particles and metal sulfide particles.

3. In paragraph 1, A cathode characterized in that the ratio of the carbon material particle size (D50) and the metal sulfide particle size (D50) is 1:0.03 to 1.

5.

4. In paragraph 1, A cathode characterized in that the cathode comprises metal sulfide particles before being assembled into a battery.

5. In paragraph 1, A cathode characterized in that the above carbon material particles are amorphous carbon material particles.

6. In paragraph 1, A negative electrode characterized in that the active material layer comprises 60 to 80 wt% of carbon material particles, 10 to 30 wt% of metal sulfide particles, and 3 to 20 wt% of binder.

7. In paragraph 1, A cathode characterized in that the carbon material particles contain 3 to 10 at% of oxygen.

8. In paragraph 7, The above oxygen is characterized in that it exists in a form included in a functional group bonded to carbon material particles.

9. A lithium ion secondary battery comprising the negative electrode of paragraph 1; the positive electrode; and an electrolyte disposed between the negative electrode and the positive electrode.

10. In paragraph 9, A lithium ion secondary battery characterized in that the electrolyte comprises a sulfide-based solid electrolyte.

11. In paragraph 10, The above secondary battery is a lithium ion secondary battery characterized in that it includes a metal sulfide in which the sulfur contained in the sulfide-based solid electrolyte reacts with the metal sulfide contained in the negative electrode, thereby increasing the sulfur content.

12. In paragraph 10, A lithium ion secondary battery characterized in that the above lithium ion secondary battery is an anodeless battery.

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