Anode and lithium ion secondary battery including said anode

Abstract

The present invention provides a negative electrode including a current collector and an active material layer, wherein the active material layer includes carbon particles and metal sulfide particles, and the metal sulfide includes one or more selected from the group consisting of AgS, MnS, and GeS, and a lithium ion secondary battery including the negative electrode.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0118217 filed September 6, 2023, and Korean Patent Application No. 10-2024-0120636 filed September 5, 2024, and all contents disclosed in the documents of said Korean patent applications are incorporated herein by reference.

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

[0003] Recently, all-solid-state secondary batteries using solid electrolytes have been attracting attention. To improve the energy density of such all-solid-state secondary batteries, it has been proposed to use lithium as the negative electrode active material. The capacity density (capacity per unit weight) of lithium is about 10 times that of graphite, which is commonly used as a negative electrode active material. Therefore, when lithium is used as the negative electrode active material, it is possible to increase the output power while reducing the thickness of the all-solid-state secondary battery.

[0004] Known all-solid-state lithium ion secondary batteries include, for example, anodeless lithium ion secondary batteries that include a negative electrode active material layer that contains a metal that forms an alloy with lithium and a carbon material.

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

[0006] The negative electrode active material layer is formed of a carbon material and a metal material such as Ag, but there is a demand for the development of various materials to improve the driving characteristics and life characteristics of the battery. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Korean Patent Publication No. 10-2020-0052707 Summary of the Invention [Problem to be solved by the invention]

[0008] An object of the present invention is to provide a negative electrode that can improve the driving characteristics and life characteristics of a battery, and a lithium ion secondary battery including the same. [Means for solving the problem]

[0009] In order to achieve the above object, the present invention provides a current collector and an active material layer, the active material layer contains carbon particles and metal sulfide particles, The metal sulfide particles provide a negative electrode containing one or more selected from the group consisting of Ag2S, MnS, and GeS.

[0010] The present invention also provides A lithium ion secondary battery is provided, which includes the negative electrode, a positive electrode, and an electrolyte interposed between the negative electrode and the positive electrode. [Effects of the Invention]

[0011] The negative electrode of the present invention includes a negative electrode active material layer in the form of a mixture of carbon particles and metal sulfide particles, thereby providing the effect of improving the driving characteristics and life characteristics of the battery.

[0012] Furthermore, the lithium ion secondary battery of the present invention includes the negative electrode active material layer, thereby providing excellent driving characteristics and life characteristics. [Brief explanation of the drawings]

[0013] [Figure 1] 1 is a cross-sectional view schematically showing the structure of a lithium ion secondary battery of the present invention. [Figure 2]1 is a cross-sectional view schematically showing the structure of a lithium ion secondary battery of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0014] The present invention will now be described in more detail to aid in its understanding.

[0015] The terms and words used in this specification and claims should not be interpreted limited to their ordinary or dictionary meanings, but should be interpreted in a way that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concepts of terms in order to best describe his or her invention. Furthermore, the terms used in this specification are merely used to describe exemplary embodiments and are not intended to limit the present invention. Singular expressions include plural expressions unless a clearly different meaning is present in the context.

[0016] When a component is referred to as being "coupled," "comprised," or "provided" with another component, it should be understood that it may be directly coupled to or provided with the other component, but that there may be other components between them. On the other hand, when a component is referred to as being "directly coupled" or "provided" with another component, it should be understood that there are no other components between them. Meanwhile, other expressions describing the relationship between components, such as "on top of" and "directly on top of," or "between" and "immediately between," or "adjacent to" and "directly adjacent to," should be interpreted similarly.

[0017] As used herein, the term "combination" is inclusive of mixtures, alloys, reaction products, and the like, unless specifically stated to the contrary.

[0018] The negative electrode of the present invention includes a current collector and an active material layer, the active material layer contains carbon particles and metal sulfide particles, The metal sulfide particles are characterized by including one or more selected from the group consisting of Ag2S, MnS, and GeS.

[0019] In one embodiment of the present invention, the metal sulfide particles may be contained in an amount of 10 parts by weight to 50 parts by weight, preferably 12 parts by weight to 28 parts by weight, and more preferably 15 parts by weight to 25 parts by weight, based on 100 parts by weight in total of the carbon material particles and the metal sulfide particles.

[0020] If the metal sulfide is contained in an amount less than 10 parts by weight, it is insufficient to form an alloy with lithium, and therefore the benefit of adding the metal sulfide to reduce the alloying activation energy cannot be realized. If the amount exceeds 50 parts by weight, the lithium storage capacity decreases, resulting in problems such as a decrease in overall capacity and a decrease in high-rate discharge characteristics, which is undesirable.

[0021] In one embodiment of the present invention, the negative electrode may contain metal sulfide particles before being assembled into a battery. That is, in the present invention, the negative electrode may contain metal sulfide from the time of producing the negative electrode active material and / or the time of producing the composition for forming the negative electrode active material layer (e.g., slurry).

[0022] In one embodiment of the present invention, the negative electrode may be free of metals in base form, not in the form of metal sulfides.

[0023] 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 a combination thereof.

[0024] When the amorphous carbon particles contain pores, the pore diameter may be 1 nm or less, preferably 0.5 nm or less. However, it may be more preferable that the amorphous carbon particles do not contain pores. This is because, if the amorphous carbon particles contain pores, lithium may be precipitated inside the pores and the lithium may be deactivated. The amount of deactivated lithium may increase with repeated charge and discharge.

[0025] The pore size of the amorphous carbon particles can be measured, for example, through a nitrogen adsorption experiment or through a transmission electron microscope.

[0026] The metal sulfides used in the present invention, which are one or more selected from the group consisting of AgS, MnS, and GeS, have the characteristic of providing superior effects compared to conventionally used metal sulfides such as TiS, CoS, NiS, FeS, MoS, CuS, CuS, and WS.

[0027] In one embodiment of the present invention, the carbon material particles and metal sulfide particles may be contained in a randomly mixed form.

[0028] In one embodiment of the present invention, the carbon particles may have a particle size (D50) of 10 nm to 150 nm, preferably 20 nm to 100 nm, and more preferably 20 nm to 60 nm.

[0029] In one embodiment of the present invention, the metal sulfide particles may have a particle size (D50) of 5 nm to 100 nm, preferably 5 nm to 80 nm, and more preferably 10 nm to 60 nm.

[0030] In one embodiment of the present invention, the ratio of the particle size (D50) of the carbon material particles to the particle size (D50) of the metal sulfide particles may be 1:0.03-1.5, 1:0.1-0.7, or 1:0.2-0.7. If the particle size ratio of the metal sulfide particles exceeds 1.5, the dispersibility of the metal sulfide particles in the electrode slurry is hindered, resulting in poor coating properties and poor electrode uniformity. Furthermore, if the particle size ratio of the metal sulfide particles is less than 0.03, the specific surface area of ​​the carbon material particles to the metal sulfide particles increases significantly, significantly increasing the amounts of binder and solvent used, which may result in reduced capacity and increased resistance, which is undesirable.

[0031] In the present invention, the particle size can be measured using a particle size analyzer, for example, a Mastersizer 3000 (Malvern Panalytical) instrument.

[0032] In one embodiment of the present invention, the carbonaceous particles may contain 3 at % to 10 at % of oxygen based on all elements contained in the carbonaceous particles. In this case, if the oxygen content is less than 3 at %, the surface roughness of the active material layer will decrease, which is undesirable, and if it exceeds 10 at %, the battery performance will decrease due to a side reaction with the solid electrolyte, which is undesirable.

[0033] 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. 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 within a range defined by a combination of the lower limit and the upper limit. Specifically, the oxygen content may be more preferably 5 to 10 at%.

[0034] In one embodiment of the present invention, the oxygen may be present in a form contained in a functional group bound to the carbon material particle, and the functional group may include one or more selected from the group consisting of a carboxy group, a hydroxy group, an ether group, an ester group, an aldehyde group, a carbonyl group, and an amide group.

[0035] The carbonaceous particles containing 3 at% to 10 at% of oxygen may be produced, for example, by oxidizing a carbonaceous material. Specifically, oxygen functional groups can be introduced onto the surface of the carbonaceous material by treating the carbonaceous material with an acid and reacting the acid at a temperature of 25°C to 60°C while stirring. The type of acid is not particularly limited, and any acid capable of introducing oxygen functional groups onto the surface of the carbonaceous material may be used. Examples of the acid include sulfuric acid, nitric acid, and a mixture thereof, and an oxidizing agent such as potassium permanganate may also be used.

[0036] The oxygen-containing carbon material may be directly produced and used, or may be purchased and used.

[0037] The content of oxygen and other elements in the carbon material can be measured using a photoelectron spectrometer (XPS or ESCA), for example, a K-Alpha (Thermo Fisher Scientific) instrument.

[0038] In one embodiment of the present invention, the components of the oxygen-containing carbonaceous particles can be configured, for example, as follows.

[0039] [Table 1]

[0040] In one embodiment of the present invention, the oxygen may be present on the surface of the carbonaceous particles. The surface does not mean only the outer surface of the carbonaceous particles, but also includes the surface of pores, if any.

[0041] In one embodiment of the present invention, the active material layer may contain 60 to 80% by weight of carbon particles, 10 to 30% by weight of metal sulfide particles, and 3 to 20% by weight 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 resin materials selected from these resin materials.

[0042] The active material layer may further contain 5% by weight to 20% by weight of a conductive material. As the conductive material, the conductive materials exemplified below for the positive electrode may be used.

[0043] In one embodiment of the present invention, the carbon material particles and metal sulfide particles may be contained in the form of a carbon material-metal sulfide composite.

[0044] In anodeless batteries, the negative electrode active material layer is formed as a very thin film with a micron thickness, but conventional active material composites have the problem that it is very difficult to form them with a small particle size. In other words, if the particle size of the active material composite is too large compared to the micron thickness of the thin film, it is difficult to form a negative electrode active material layer with good surface roughness, and this reduction in surface roughness acts as a cause of deterioration in the battery's operating characteristics.

[0045] The present invention provides a revolutionary solution to the above-mentioned problems of the prior art. Specifically, the carbon material-metal sulfide composite of the present invention forms a carbon material-metal sulfide composite with significantly smaller particle size than when conventional carbon materials are used. The carbon material forming the composite contains 3 at% or more of oxygen, which allows it to mix well with metal sulfide particles and distribute uniformly with the metal sulfide particles. Therefore, it is possible to produce a carbon material-metal sulfide composite with excellent component uniformity. Furthermore, for the above reasons, it is possible to produce a carbon material-metal sulfide composite with a small and uniform particle size.

[0046] In one embodiment of the present invention, the carbonaceous material-metal sulfide composite may be formed by one or more bonds selected from the group consisting of chemical bonds between carbonaceous material particles and metal sulfide particles, van der Waals bonds between carbonaceous material particles and metal sulfide particles, and bonds between carbonaceous material particles and metal sulfide particles via a binder. The chemical bonds may be bonds between metal sulfide particles and oxygen contained in the carbonaceous material.

[0047] In one embodiment of the present invention, the carbon material-metal sulfide composite may contain, based on the total weight, 60 wt % to 80 wt % of a carbon material, 10 wt % to 30 wt % of a metal sulfide, and 3 wt % to 20 wt % of a binder.

[0048] The binder may be dissolved in a solvent together with the carbon material particles and the metal sulfide particles during the wet preparation of the carbon material-metal sulfide composite. In this case, the binder may be included in the carbon material-metal sulfide composite.

[0049] 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, and the upper limit of the particle size may be 0.4 μm or 0.3 μm.

[0050] The maximum particle size of the carbon material-metal sulfide composite may be 3 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less.

[0051] If the particle size of the carbonaceous material-metal sulfide composite is too large for a micro-thick thin film, it is difficult to form a negative electrode active material layer with excellent surface roughness, which deteriorates the driving characteristics of the battery. Therefore, it is very important to produce the carbonaceous material-metal sulfide composite with a small particle size.

[0052] The reason for the deterioration of the driving characteristics of the battery is that when the surface roughness of the negative electrode active material layer is large, sufficient contact with the electrolyte layer is not achieved on the electrolyte side, which does not contribute to uniform deposition of lithium on the negative electrode current collector side.

[0053] In a negative electrode-less lithium ion secondary battery, the thickness of the negative electrode active material layer may be typically formed in the range of 1 μm to 100 μm, or 10 μm to 60 μm, and specifically, may be formed to a thickness of 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc.

[0054] For example, when a carbon material-metal sulfide composite with a particle size of 10 μm is used to form a negative electrode active material layer with a thickness of 20 μm, it is obvious that it is difficult to form a desired surface roughness.

[0055] When the maximum particle size of the carbon material-metal sulfide composite is 3 μm or less, the effect of improving the surface roughness can be more reliably obtained, which is preferable, whereas when it exceeds 3 μm, it may be difficult to obtain an excellent surface roughness when forming a thin film.

[0056] The particle size of the carbon material-metal sulfide composite can be measured using a particle size analyzer, for example, a Mastersizer 3000 (Malvern Panalytical) instrument.

[0057] The present invention also provides A lithium ion secondary battery is provided, which includes the negative electrode, a positive electrode, and an electrolyte interposed between the negative electrode and the positive electrode.

[0058] The lithium ion secondary battery includes the negative electrode active material layer of the present invention, thereby providing improved driving characteristics and life characteristics.

[0059] In one embodiment of the present invention, the solid electrolyte may be a sulfide-based solid electrolyte.

[0060] In one embodiment of the present invention, the secondary battery may contain a metal sulfide in a state where the sulfur content is increased as a result of a reaction between sulfur contained in the sulfide-based solid electrolyte and the metal sulfide contained in the negative electrode.

[0061] In one embodiment of the present invention, the lithium ion secondary battery may be a negative electrode-less battery.

[0062] The embodiments of the present invention will be illustrated more specifically below.

[0063] <Configuration of all-solid-state lithium-ion secondary battery> FIG. 1 is a cross-sectional view showing a schematic configuration of an all-solid-state lithium-ion secondary battery according to an embodiment of the present invention.

[0064] 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 is charged and discharged by the movement of lithium ions between a positive electrode (10) and a negative electrode (20). Specifically, as shown in FIG. 1, this all-solid-state lithium-ion secondary battery (100) is composed of a positive electrode (10), a negative electrode (20), and a solid electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20).

[0065] (1) Positive electrode As shown in FIG. 1, the positive electrode (10) includes a positive electrode current collector (12) and a positive electrode active material layer (14) arranged in this order toward the negative electrode (20).

[0066] The positive electrode current collector (12) may be in the form of a plate or foil and may be made of, for example, one metal selected from the group consisting of indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, and lithium, or an alloy of two or more metals.

[0067] The positive electrode active material layer 14 can reversibly absorb and release lithium ions and may include a positive electrode active material and a solid electrolyte.

[0068] The positive electrode active material may be a compound capable of intercalating / deintercalating lithium. Examples of the compound capable of intercalating / deintercalating lithium include Li a A 1-b B' bD'2 (wherein 0.90≦a≦1.8 and 0≦b≦0.5), Li a E 1-b B' b O 2-c D' c (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05), LiE 2-b B' b O 4-c D' c (wherein 0≦b≦0.5 and 0≦c≦0.05), Li a Ni 1-b-c Co b B' c D' α (wherein, 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 (wherein, 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 (wherein, 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 (wherein, 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 (wherein 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, and 0.001≦d≦0.1), Li a Ni b Co c Mn d G eO2 (wherein, 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 (wherein 0.90≦a≦1.8, 0.001≦b≦0.1), Li a CoG b O2 (wherein 0.90≦a≦1.8, 0.001≦b≦0.1), Li a MnG b O2 (wherein 0.90≦a≦1.8, 0.001≦b≦0.1), Li a Mn2G b O4 (wherein 0.90≦a≦1.8, 0.001≦b≦0.1), QO2, QS2, LiQS2, V2O5, LiV2O5, LiI'O2, LiNiVO4, Li 3-f J2(PO4)3(0≦f≦2), Li 3-f Fe2(PO4)3 (0≦f≦2), LiFePO4, Li4Ti5O 12 (LTO)

[0069] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, or a combination thereof; D' is O, F, S, P, or a combination thereof; E is Co, Mn, or a combination thereof; F' is F, S, P, or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V, or a combination thereof; Q is Ti, Mo, Mn, or a combination thereof; I' is Cr, V, Fe, Sc, Y, or a combination thereof; and J is V, Cr, Mn, Co, Ni, Cu, or a combination thereof.

[0070] Specific examples of the positive electrode active material include lithium cobaltate (hereinafter referred to as LCO), lithium nickelate, lithium nickel cobaltate, lithium nickel cobalt aluminum oxide (hereinafter referred to as NCA), lithium nickel cobalt manganese oxide (hereinafter referred to as NCM), lithium manganate, lithium salts such as lithium iron phosphate, and lithium sulfide. The positive electrode active material layer (14) may contain only one kind selected from these compounds as the positive electrode active material, or may contain two or more kinds.

[0071] The positive electrode active material may include a lithium salt of a transition metal oxide having a layered rock salt structure among the above-mentioned lithium salts. Here, the "layered rock salt structure" is a structure in which oxygen atom layers and metal atom layers are alternately and regularly arranged in the direction of the cubic rock salt structure, and as a result, each atom layer forms a two-dimensional plane. The "cubic rock salt structure" means a sodium chloride type structure which is a kind of crystal structure. For example, the "cubic rock salt structure" refers to a structure in which face-centered cubic lattices formed by cations and anions are arranged with a deviation of 1 / 2 of the corner of the unit lattice from each other.

[0072] Examples of the lithium salt of the transition metal oxide having such a layered rock salt structure include, for example, LiNi x Co y Al z O2 (NCA) or LiNi x Co y Mn z O2 (NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, x + y + z = 1) and the like may be ternary lithium transition metal oxides. By including a lithium salt of a ternary transition metal oxide having such a layered rock salt structure as the positive electrode active material, the energy density and thermal stability of the all-solid-state lithium ion secondary battery (100) can be improved.

[0073] Here, examples of the shape of the positive electrode active material include particle shapes such as spherical and oval spheres. The particle size of the positive electrode active material is not particularly limited, as long as it is within a range applicable to positive electrode active materials in typical all-solid-state lithium-ion secondary batteries. The content of the positive electrode active material in the positive electrode active material layer (14) is also not particularly limited, as long as it is within a range applicable to positive electrodes in typical all-solid-state lithium-ion secondary batteries.

[0074] Of course, the compound may have a coating layer on its surface, or the compound may be mixed with a compound having a coating layer. The coating layer may include a coating element compound such as an oxide, hydroxide, oxyhydroxide, oxycarbonate, or hydroxycarbonate of the coating element. The compounds constituting these coating layers may be amorphous or crystalline. Examples of coating elements included in the coating layer include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof. The coating layer formation process may be performed using any coating method (e.g., spray coating, dipping, etc.) that does not adversely affect the physical properties of the positive electrode active material. Since this method is well understood by those skilled in the art, a detailed description will be omitted.

[0075] Specific examples of the coating layer include Li2O-ZrO2.

[0076] The solid electrolyte contained in the positive electrode active material layer (14) may be the same as or different from the solid electrolyte contained in the solid electrolyte layer (30) described below.

[0077] The positive electrode active material layer (14) may contain not only the above-described positive electrode active material and solid electrolyte, but also additives such as a conductive material, a binder, a filler, a dispersant, or an ion-conductive auxiliary agent, as appropriate.

[0078] Examples of the conductive material include graphite, carbon black, acetylene black, Ketjen black, carbon fiber, and metal powder. Examples of the binder include styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. Examples of the filler, dispersant, and ion-conducting additive may include known materials typically used in electrodes of all-solid-state lithium-ion secondary batteries.

[0079] (2) Negative electrode The negative electrode (20) may include a negative electrode current collector (22) and a negative electrode active material layer (24) arranged in this order toward the positive electrode (10).

[0080] The negative electrode current collector 22 may be in the form of a plate or foil. The negative electrode current collector 22 may include a material that does not react with lithium, i.e., does not form any alloy or compound with lithium. Examples of materials that can be used for the negative electrode current collector 22 include copper, stainless steel, titanium, iron, cobalt, and nickel. The negative electrode current collector 22 may be made of one of these metals, or may be made of an alloy or clad material of two or more metals.

[0081] The anode active material layer (24) may not contain lithium in the anode current collector (22), the anode active material layer (24), or between the anode active material layer (24) and the solid electrolyte layer (30) in an initial state or after full discharge. As described below, when an all-solid-state lithium-ion secondary battery (100) according to one embodiment is overcharged, the active material contained in the anode active material layer (24) and lithium ions transferred from the cathode (10) may form an alloy or compound, and a metal layer (26) primarily composed of lithium may be formed (deposited) on the anode (20), as shown in FIG. 2. The metal layer (26) may be deposited between the anode current collector (22) and the anode active material layer (24), within the anode 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 disposed closer to the negative electrode current collector layer (22) than to the negative electrode active material layer (24).

[0082] The negative electrode active material layer (24) may contain carbon particles, metal oxide particles, and a binder. The binder (binding agent) can stabilize the negative electrode active material layer (24) 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 resin materials selected from these resin materials.

[0083] The negative electrode active material layer (24) may also contain additives used in conventional all-solid-state lithium ion secondary batteries, such as fillers, dispersants, conductive materials, etc. Specific examples of the additives are the same as those described above for the positive electrode.

[0084] The total thickness of the negative electrode active material layer (24) is not particularly limited, but may be 1 μm to 100 μm, or 10 μm to 60 μm. If the thickness of the negative electrode active material layer (24) is less than 1 μm, the performance of the all-solid-state secondary battery may not be sufficiently improved. If the thickness of the negative electrode active material layer (24) is more than 100 μm, the resistance of the negative electrode active material layer (24) increases, and as a result, the performance of the all-solid-state secondary battery may not be sufficiently improved. By using the above-mentioned binder, the thickness of the negative electrode active material layer (24) can be easily ensured to be at an appropriate level.

[0085] On the other hand, the negative electrode current collector (22) may further include a film containing a material capable of forming an alloy or compound with lithium, and the film may be disposed between the negative electrode current collector (22) and the negative electrode active material layer.

[0086] The negative electrode current collector 22 does not react with lithium metal, but may make it difficult to deposit a smooth lithium metal layer on top. The film may be used as a wetting layer to allow lithium metal to deposit evenly on top of the negative electrode current collector 22.

[0087] 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 small as long as it does not affect the electrochemical properties and / or redox potential of the electrode. The film may be applied evenly on the negative electrode current collector (22) to prevent cracking during charging cycles of the all-solid-state lithium-ion secondary battery (100). The film may be applied using a method such as physical vapor deposition (e.g., evaporation or sputtering), chemical vapor deposition, or plating.

[0088] The thickness of the film may be 1 nm to 500 nm. The thickness of the film may be, for example, 2 nm to 400 nm. The thickness of the film may be, for example, 3 nm to 300 nm. The thickness of the film may be, for example, 4 nm to 200 nm. The thickness of the film may be, for example, 5 nm to 100 nm.

[0089] (3) Solid electrolyte layer The solid electrolyte layer (30) is disposed between the positive electrode (10) and the negative electrode (20) (for example, between the positive electrode active material layer (14) and the negative electrode active material layer (24)). The solid electrolyte layer (30) contains a solid electrolyte capable of transferring ions. The solid electrolyte layer (30) may contain a sulfide-based solid electrolyte.

[0090] The sulfide-based solid electrolytes include Li2S-P2S5, Li2S-P2S5-LiX (X is a halogen element), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, and Li2S-P2S5-Z m S n (m and n are positive numbers, Z is one of Ge, Zn, or Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (p and q are positive numbers, and M is one of P, Si, Ge, B, Al, Ga, and In), or a combination thereof. The solid electrolyte may be made of one material selected from these sulfide-based solid electrolyte materials, or may be made of two or more materials.

[0091] The 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, and w are each independently 0 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.

[0092] As the solid electrolyte, among the sulfide solid electrolyte materials, those containing sulfur (S), phosphorus (P), and lithium (Li) as constituent elements may be used. For example, those containing Li2S-P2S5 may be used. When using a sulfide-based solid electrolyte material containing Li2S-P2S5, the molar ratio of Li2S to P2S5 can be selected, for example, from the range of Li2S:P2S5 = 50:50 to 90:10.

[0093] The solid electrolyte may be in an amorphous state, a crystalline state, or a mixture of amorphous and crystalline states.

[0094] The solid electrolyte layer (30) may further include a binder. Examples of the binder include resins such as styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, and polyacrylic acid. The binder may be the same as or different from the binders in the positive electrode active material layer (14) and the negative electrode active material layer (24).

[0095] (4) Structure 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 a negative electrode (20) in this order, as shown in FIG.

[0096] <Manufacturing method for all-solid-state lithium-ion secondary batteries> Next, a description will be given of a method for manufacturing the all-solid-state lithium-ion secondary battery 100. In one embodiment, the all-solid-state lithium-ion secondary battery 100 is obtained by first preparing a positive electrode 10, a negative electrode 20, and a solid electrolyte layer 30, and then laminating these layers together.

[0097] (1) Positive electrode manufacturing process The process for producing a positive electrode is described below as an 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 prepare a slurry (or paste). Next, the obtained slurry is applied to a 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 step is omitted.

[0098] (2) Negative electrode manufacturing process The process for producing a negative electrode will be described as follows: First, materials constituting the negative electrode active material layer (24) (carbon particles, metal oxide particles, binder, etc.) are added to a polar or nonpolar solvent to produce a slurry (which may be a paste). Next, the resulting slurry is applied to a prepared negative electrode current collector (22) to form the negative electrode active material layer.

[0099] When the negative electrode active material layer further includes one or more layers, the additional layers may be stacked in the same manner as above.

[0100] Next, the laminate obtained by the above method is pressed, for example, using hydrostatic pressure, to produce the negative electrode (20). The pressing step may be omitted. 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 coating, dip coating, spray coating, roll coating, doctor blade coating, and gravure coating.

[0101] Although the method for forming the negative electrode active material layer in two layers has been described above, when an additional layer is to be formed, a negative electrode can be manufactured by preparing slurries for forming each layer and sequentially stacking each layer according to the stacking order using the method described above.

[0102] (3) Solid electrolyte layer manufacturing process The solid electrolyte layer (30) can be made of a solid electrolyte containing, for example, a sulfide-based solid electrolyte material.

[0103] First, starting materials (e.g., Li2S, P2S5, etc.) are processed by melt quenching or mechanical milling to obtain a sulfide-based solid electrolyte material. For example, when using the melt quenching method, predetermined amounts of starting materials are mixed and formed into pellets, which are reacted in a vacuum at a predetermined reaction temperature and then quenched to produce a sulfide-based solid electrolyte material. The reaction temperature for the mixture of Li2S and P2S5 may be 400°C to 1000°C, for example, 800°C to 900°C. The reaction time may be 0.1 hours to 12 hours, for example, 1 hour to 12 hours. The quenching temperature of the reaction product 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.

[0104] Furthermore, when mechanical milling is used, the sulfide-based solid electrolyte material can be produced by stirring and reacting the starting materials using a ball mill, etc. Furthermore, the stirring speed and stirring time in the mechanical milling method are not particularly limited, but the faster the stirring speed, the faster the production rate of the sulfide-based solid electrolyte material can be, and the longer the stirring time, the higher the conversion rate of the raw materials to the sulfide-based solid electrolyte material can be.

[0105] The resulting mixed raw material (sulfide-based solid electrolyte material) is then heat-treated at a predetermined temperature and pulverized to produce a particulate solid electrolyte. If the solid electrolyte has a glass transition point, the heat treatment may cause it to change from amorphous to crystalline.

[0106] The solid electrolyte obtained by the above method can then be formed into a film using a known film formation method, such as aerosol deposition, cold spray, or sputtering, to produce a solid electrolyte layer 30. The solid electrolyte layer 30 may also be produced by pressurizing solid electrolyte particles. The solid electrolyte layer 30 can also be produced by mixing the solid electrolyte with a solvent and a binder, applying the mixture, drying, and pressurizing.

[0107] (4)Lamination process An all-solid-state lithium-ion secondary battery (100) according to one embodiment can be obtained by disposing a solid electrolyte layer (30) between a positive electrode (10) and a negative electrode (20) and pressurizing them using, for example, hydrostatic pressure.

[0108] The all-solid-state lithium-ion secondary battery (100) of the present invention does not require application of high external pressure using end plates or the like, and can provide improved discharge capacity even when the external pressure applied to the positive electrode (10), the negative electrode (20), and the solid electrolyte layer (30) during use is 1 MPa or less.

[0109] <Charging method for all-solid-state lithium-ion secondary batteries> Next, a method for charging the all-solid-state lithium-ion secondary battery (100) will be described.

[0110] According to one embodiment, a method for charging the all-solid-state lithium-ion secondary battery (100) may involve charging the all-solid-state lithium-ion secondary battery (100) beyond the charge capacity of the negative electrode active material layer (24) (i.e., overcharging).

[0111] At the beginning of charging, lithium may be absorbed into the anode active material layer (24). When the anode active material layer (24) is charged beyond its charge capacity, as shown in FIG. 2 , lithium may precipitate on the back surface of the anode active material layer (24), i.e., between the anode current collector (22) and the anode active material layer (24). This lithium may form a metal layer (26) that was not present at the time of manufacturing. During discharge, lithium in the anode active material layer (24) and the metal layer (26) may ionize and migrate to the cathode (10). Therefore, lithium may be used as the anode active material in the all-solid-state lithium-ion secondary battery (100) of the present invention. Furthermore, the anode active material layer (24) coats the metal layer (26), thereby functioning as a protective layer for the metal layer (26) and suppressing the deposition and growth of resin-like metallic lithium. This suppresses short circuits and capacity loss in the all-solid-state lithium-ion secondary battery (100) and further improves the characteristics of the all-solid-state lithium-ion secondary battery (100). Furthermore, according to one embodiment, the metal layer (26) is not pre-formed, which reduces the manufacturing cost of the all-solid-state lithium-ion secondary battery (100).

[0112] 2, 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, but may be formed inside the negative electrode active material layer 24. The metal layer 26 may be formed entirely between the negative electrode current collector 22 and the negative electrode active material layer 24 and inside the negative electrode active material layer 24.

[0113] The all-solid-state lithium ion secondary battery (100) of the present invention may be fabricated in the form of a unit cell having a positive electrode / separator / negative electrode structure, a bi-cell having a positive electrode / separator / negative electrode / separator / positive electrode structure, or a stacked battery structure in which the unit cell structure is repeated.

[0114] 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, laminated, cylindrical, flat, and rectangular shapes. It can also be applied to large-scale batteries used in electric vehicles. For example, the all-solid-state lithium-ion secondary battery (100) may be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). It may also be used in fields requiring large-scale power storage. For example, it may be used in electric bicycles or power tools.

[0115] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to the present invention can be modified into various other forms, and the scope of the present invention should not be construed as being limited to the examples detailed below. The examples of the present invention are provided to more completely explain the present invention to those skilled in the art.

[0116] Example 1: Preparation of negative electrode active material slurry 6 g of carbon black with a particle size (D50) of 41 nm, 2 g of AgS with a particle size (D50) of 10 nm to 60 nm, 9.33 g of PVdF binder (solid content 6%), and 6 g of N-methyl-2-pyrrolidone (NMP) solution were placed in a Thinky mixer container and mixed at 1800 rpm for 3 minutes each 12 times. Then, an additional 6 g of NMP solution was added, and the mixture was mixed at 1800 rpm for 3 minutes each 5 times to prepare a negative electrode active material slurry of Example 1.

[0117] [Example 2: Production of negative electrode active material slurry] 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 (D50) of 10 nm to 60 nm was used instead of 2 g of Ag2S.

[0118] [Example 3: Production of negative electrode active material slurry] A negative electrode active material slurry was prepared in the same manner as in Example 1, except that 2 g of MnS having a particle size (D50) of 10 nm to 60 nm was used instead of 2 g of Ag2S.

[0119] Comparative Example 1: Production of Negative Electrode Active Material Slurry A negative electrode active material slurry of Comparative Example 1 was prepared in the same manner as in 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.

[0120] [Examples 4 to 6 and Comparative Example 2: Production of Negative Electrode] Each of the negative electrode active material slurries prepared in Examples 1 to 3 and Comparative Example 1 was blade coated on a SUS foil to a thickness of 10 μm and dried to obtain the negative electrode active material slurries of Examples 4 to 6 and Comparative Example 2 (0.9 mAh / cm 2 ) anode was produced.

[0121] [Production of all-solid-state lithium-ion secondary batteries in Examples 7 to 9 and Comparative Example 3] The positive electrode was made by mixing NCM and argyrodite-based electrolyte in a weight ratio of 5.7:1 as the positive electrode active material, and the current collector was charged to 6 mAh / cm 2 The positive electrode loaded in Example 1 was used, the negative electrode was the negative electrode produced in Examples 4 to 6 and Comparative Example 2, and the electrolyte was a sulfide-based all-solid electrolyte (LPSCl composition), to produce pouch-type mono-cells in Examples 7 to 9 and Comparative Example 3.

[0122] [Experimental Example 1: Evaluation of battery characteristics] The pouch-type monocells produced in Examples 7 and 8 and Comparative Example 3 were subjected to the following experiments, and the results are shown in Table 2 below.

[0123] (1) Evaluation of initial efficiency The pouch-type mono cell was charged at a 0.1 C rate until the voltage reached 4.25 V (vs. Li), and then cut off at a 0.05 C rate while maintaining 4.25 V (vs. Li). It was then discharged at a 0.1 C rate until the discharge voltage reached 3.0 V (vs. Li) (first cycle). The initial efficiency was calculated as discharge capacity / charge capacity x 100 (%).

[0124] (2) Evaluation of discharge capacity The pouch-type monocell was operated at an operating voltage range of 4.25 V to 3.0 V and at a temperature of 60°C, and the cycle characteristics were evaluated.

[0125] (3) Evaluation of life performance The pouch-type monocell was charged at a rate of 0.33 C at an operating temperature of 60°C until the voltage reached 4.25 V (vs. Li), and then cut off at a rate of 0.1 C while maintaining 4.25 V (vs. Li). It was then discharged at a rate of 0.33 C until the discharge voltage reached 3.0 V (vs. Li) (first cycle). This charge-discharge test was repeated 20 times, and the capacity retention of the discharge capacity was measured.

[0126] [Table 2] [Explanation of symbols]

[0127] 10 positive electrode 12 Positive electrode current collector 14 Cathode active material layer 20 negative electrode 22 Negative electrode current collector 22 Negative electrode current collector layer 24 Negative electrode active material layer 26 metal layer 30 Solid electrolyte layer 60 carbon particles 100 All-solid-state lithium-ion secondary battery

Claims

1. a current collector and an active material layer, the active material layer contains carbon particles and metal sulfide particles, The metal sulfide particles are Ag ２ A negative electrode comprising one or more selected from the group consisting of S, MnS, and GeS.

2. 2. The anode of claim 1, wherein the metal sulfide particles are included in an amount of 10 to 50 parts by weight based on 100 parts by weight of the total of the carbon material particles and the metal sulfide particles.

3. 2. The negative electrode according to claim 1, wherein the ratio of the particle size (D50) of the carbon material particles to the particle size (D50) of the metal sulfide particles is 1:0.03 to 1.

5.

4. The negative electrode of claim 1 , wherein the negative electrode contains the metal sulfide particles before being assembled into a battery.

5. The negative electrode according to claim 1 , wherein the carbon particles are amorphous carbon particles.

6. 2. The negative electrode according to claim 1, wherein the active material layer comprises 60% to 80% by weight of the carbon particles, 10% to 30% by weight of metal sulfide particles, and 3% to 20% by weight of a binder.

7. 2. The negative electrode according to claim 1, wherein the carbon particles contain 3 at % to 10 at % of oxygen.

8. The anode of claim 7 , wherein the oxygen is present in a form contained in a functional group bonded to the carbon material particles.

9. A lithium ion secondary battery comprising the negative electrode according to any one of claims 1 to 8, a positive electrode, and an electrolyte interposed between the negative electrode and the positive electrode.

10. The lithium ion secondary battery according to claim 9, wherein the electrolyte includes a sulfide-based solid electrolyte.

11. 11. The lithium ion secondary battery according to claim 10, wherein the metal sulfide particles have an increased sulfur content due to a reaction between sulfur contained in the sulfide-based solid electrolyte and the metal sulfide particles contained in the negative electrode.

12. The lithium ion secondary battery according to claim 10, wherein the lithium ion secondary battery is a negative electrode-less battery.

Images