Negative electrode and lithium ion secondary battery including said negative electrode

Abstract

a current collector and an active material layer, The active material layer provides a negative electrode containing carbon particles and one or more metal fluoride particles selected from the group consisting of AgF, LiF, ZnF2, AlF3, CaF2, CoF3, CuF2, NiF2, and CoF2, and a lithium ion secondary battery containing the same.

Description

[Technical Field]

[0001] This application claims the benefit of priority based on Korean Patent Application No. 10-2023-0028510 filed on March 3, 2023, and Korean Patent Application No. 10-2024-0029527 filed on February 29, 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] In recent years, 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, anode-less 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 anodeless lithium-ion secondary battery described above is driven by a mechanism in which metallic lithium is deposited in the negative electrode active material layer and between the negative electrode 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 need to develop a variety of materials to improve the driving characteristics and life characteristics of the battery. [Prior art documents] [Patent documents]

[0007] [Patent Document 1] Republic of Korea Patent Publication No. 10-2015-0064697 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 improves 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 a current collector and an active material layer, The active material layer provides a negative electrode containing carbon particles and particles of one or more metal fluorides selected from the group consisting of AgF, LiF, ZnF2, AlF3, CaF2, CoF3, CuF2, NiF2, and CoF2.

[0010] The present invention also provides The lithium ion secondary battery 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 carbonaceous particles and metal fluoride 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 understanding the invention.

[0015] The terms or words used in this specification and claims should not be interpreted limited to their ordinary or dictionary meanings, but should be interpreted in a meaning and concept that is consistent with the technical idea of ​​the present invention, based on the principle that the inventor can appropriately define the concept of the term in order to best describe his / 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. The singular expression includes the plural expression unless a clearly different meaning is present in the context.

[0016] When a component is said to be "connected, mounted, or installed" to another component, it should be understood that the component may be directly connected to or installed on the other component, but there may also be other components between them. Conversely, when a component is said to be "directly connected to or installed" on 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 is characterized by containing carbon particles and one or more metal fluoride particles selected from the group consisting of AgF, LiF, ZnF2, AlF3, CaF2, CoF3, CuF2, NiF2, and CoF2.

[0019] In one embodiment of the present invention, the metal fluoride particles may be contained in an amount of 15 to 50 parts by weight, preferably 15 to 40 parts by weight, more preferably 20 to 30 parts by weight, and even more preferably 23 to 27 parts by weight, based on 100 parts by weight of the total weight of the carbon material particles and the metal fluoride particles.

[0020] If the metal fluoride is contained in an amount less than 15 parts by weight, it is insufficient to form an alloy with lithium, and therefore the advantage of adding the metal fluoride to reduce the alloying activation energy cannot be realized. If the amount exceeds 50 parts by weight, the lithium storage capacity decreases, which is undesirable because it causes problems such as a decrease in overall capacity and a decrease in high-rate discharge characteristics.

[0021] In one embodiment of the present invention, the ratio of the particle size (D50) of the carbon material to the particle size (D50) of the metal fluoride 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 fluoride exceeds 1.5, the dispersibility in the electrode slurry is hindered, resulting in poor coating properties and poor electrode uniformity. Furthermore, if the particle size ratio of the metal fluoride is less than 0.03, the specific surface area of ​​the carbon material and the metal fluoride particles increases significantly, necessitating a significant increase in the amounts of binder and solvent used, which can result in reduced capacity and increased resistance, which is undesirable.

[0022] In one embodiment of the present invention, the carbon material particles and the metal fluoride particles may be contained in a randomly mixed form.

[0023] In one embodiment of the present invention, the carbon particles may be, for example, amorphous carbon particles. Specific examples of the amorphous carbon material include carbon black, such as acetylene black, furnace black, and ketjen black, graphene, or a combination thereof. When the carbon particles have a high degree of crystallinity, lithium intercalation and deintercalation becomes difficult, which can lead to an increase in cell resistance.

[0024] When the amorphous carbon particles contain pores, the size of the pores may be 1 nm or less, preferably 0.5 nm or less. However, it may be more preferable that the amorphous carbon particles do not contain pores. This is because, when the amorphous carbon particles contain pores, lithium may precipitate inside the pores and become inactive, and the amount of deactivated lithium may increase as charge and discharge are repeated.

[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] 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.

[0027] In one embodiment of the present invention, the carbonaceous particles may contain 3 at % to 10 at % of oxygen based on the total 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.

[0028] 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 at% to 10 at%.

[0029] 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 carboxyl group, a hydroxyl group, an ether group, an ester group, an aldehyde group, a carbonyl group, and an amide group.

[0030] The carbonaceous particles containing 3 at% to 10 at% of oxygen can 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 that can introduce oxygen functional groups onto the surface of the carbonaceous material can be used. Examples of the acid include sulfuric acid, nitric acid, and a mixture thereof, and an oxidizing agent such as potassium permanganate can also be used.

[0031] The oxygen-containing carbon material can be directly produced and used, or can be purchased and used.

[0032] The oxygen content of the carbon material can be measured using a photoelectron spectrometer (XPS or ESCA), for example, a K-Alpha (Thermo Fisher Scientific) device.

[0033] 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 surfaces of pores, if any.

[0034] In one embodiment of the present invention, the metal fluoride particles to be used have a particle size (D50) of 10 nm to 150 nm, preferably 20 nm to 100 nm.

[0035] In one embodiment of the present invention, the active material layer contains 60 to 80% by weight of carbon particles, 15 to 30% by weight of metal fluoride 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 can be composed of one or more resin materials selected from these resin materials.

[0036] In one embodiment of the present invention, the carbon material particles and metal fluoride particles may be included in the form of a carbon material-metal fluoride composite.

[0037] 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 a problem in 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 driving characteristics.

[0038] The present invention provides a revolutionary solution to the above-mentioned problems of the prior art. That is, the carbon material-metal fluoride composite of the present invention forms a carbon material-metal fluoride composite with a significantly smaller particle size than when using conventional carbon materials. The carbon material forming the composite contains 3 at% or more of oxygen, which allows it to be well mixed with and uniformly distributed among the metal fluoride particles. This makes it possible to produce a carbon material-metal fluoride composite with excellent component uniformity. Furthermore, for the same reasons as above, it makes it possible to produce a carbon material-metal fluoride composite with a small, uniform particle size.

[0039] In one embodiment of the present invention, the carbonaceous material-metal fluoride composite may be formed by one or more bonds selected from the group consisting of chemical bonds between carbonaceous material particles and metal fluoride particles, van der Waals bonds between carbonaceous material particles and metal fluoride particles, and bonds between carbonaceous material particles and metal fluoride particles via a binder. The chemical bonds may be bonds between metal fluoride particles and oxygen contained in the carbonaceous material.

[0040] In one embodiment of the present invention, the carbon material-metal fluoride composite may contain, based on the total weight, 60 wt % to 80 wt % of the carbon material, 15 wt % to 30 wt % of the metal fluoride, and 3 wt % to 20 wt % of the binder.

[0041] The binder can be used by dissolving it in a solvent together with carbon material particles and metal fluoride particles during wet preparation of the carbon material-metal fluoride composite. In this case, the binder may be contained in the carbon material-metal fluoride composite.

[0042] In one embodiment of the present invention, the particle size (D50) of the carbon material-metal fluoride 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.

[0043] The maximum particle size of the carbon material-metal fluoride composite may be 3 μm or less, 2 μm or less, 1.5 μm or less, or 1 μm or less.

[0044] If the particle size of the carbonaceous material-metal fluoride composite is too large compared to 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 prepare the carbonaceous material-metal fluoride composite with a small particle size.

[0045] The reason why the driving characteristics of the battery deteriorate is that when the surface roughness of the negative electrode active material layer is large, sufficient contact with the electrolyte layer is not achieved in the direction toward the electrolyte, and this does not contribute to uniform deposition of lithium in the direction toward the negative electrode current collector.

[0046] In an anodeless lithium ion secondary battery, the thickness of the negative electrode active material layer can usually be formed in the range of 1 μm to 100 μm or 10 μm to 60 μm, and specifically, it can be formed to a thickness of 10 μm, 20 μm, 30 μm, 40 μm, 50 μm, etc.

[0047] For example, if a carbon material-metal fluoride 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 desirable surface roughness.

[0048] It is preferable that the maximum particle size of the carbon material-metal fluoride composite is 3 μm or less, since the effect of improving the surface roughness can be more reliably obtained. On the other hand, if it exceeds 3 μm, it may be difficult to obtain an excellent surface roughness when forming a thin film.

[0049] The particle size of the carbon material-metal fluoride composite can be measured using a particle size analyzer, for example, a Mastersizer 3000 (Malvem Panalytical) instrument.

[0050] The present invention provides a negative electrode active material layer containing the carbon material-metal fluoride composite.

[0051] The negative electrode active material layer has a uniform distribution of carbon material and metal fluoride and has excellent surface roughness, thereby improving the driving characteristics of a lithium ion secondary battery containing the negative electrode active material layer.

[0052] The present invention also provides The lithium ion secondary battery includes the negative electrode; a positive electrode; and an electrolyte interposed between the negative electrode and the positive electrode.

[0053] The lithium ion secondary battery may be an anode-less battery.

[0054] The lithium ion secondary battery includes the negative electrode active material layer of the present invention, thereby providing improved driving characteristics and life characteristics.

[0055] In one embodiment of the present invention, the solid electrolyte may be a sulfide-based solid electrolyte.

[0056] In one embodiment of the present invention, the lithium ion secondary battery may be an anode-less battery.

[0057] Hereinafter, the embodiments of the present invention will be described more specifically.

[0058] [Structure of all-solid-state lithium-ion secondary batteries] 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.

[0059] The 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, the all-solid-state lithium-ion secondary battery (100) is composed of a positive electrode (10), a negative electrode (20), and a solid electrolyte layer (30) disposed between the positive electrode (10) and the negative electrode (20).

[0060] (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).

[0061] 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.

[0062] The positive electrode active material layer 14 can reversibly absorb and release lithium ions and may contain a positive electrode active material and a solid electrolyte.

[0063] 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 A1- 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, and 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, and 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, and 0<α<2); Li a Ni 1-b-cMn b B' c D' α (wherein, 0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, and 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, and 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 e O2 (wherein 0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, and 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) It can be expressed by one of the following chemical formulas: Fe2(PO4)3(0≦f≦2); LiFePO4.

[0064] 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.

[0065] Specific examples of the positive electrode active material include lithium cobalt oxide (hereinafter referred to as LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel aluminum oxide (hereinafter referred to as NCA), lithium nickel cobalt manganese oxide (hereinafter referred to as NCM), lithium salts such as lithium manganese oxide and lithium iron phosphate, and lithium sulfide. The positive electrode active material layer (14) may contain only one type selected from these compounds as the positive electrode active material, or may contain two or more types selected from these compounds.

[0066] The positive electrode active material may contain, among the lithium salts described above, a lithium salt of a transition metal oxide having a layered rock salt structure. 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 a cubic rock salt structure, resulting in each atomic layer forming a two-dimensional plane. Furthermore, 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 formed by cations and anions are shifted from each other by half the angle of the unit cell.

[0067] Examples of lithium salts of transition metal oxides having such a layered rock salt structure include LiNi x Co y Al z O2(NCA) or LiNix Co y Mn z It may also be a ternary lithium transition metal oxide such as O2(NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1, and x + y + z = 1). By including a lithium salt of such a ternary transition metal oxide having a layered rock salt structure as the positive electrode active material in the positive electrode active material layer (14), the energy density and thermal stability of the all-solid-state lithium ion secondary battery (100) can be improved.

[0068] Here, examples of the shape of the positive electrode active material include particle shapes such as true spherical and ellipsoidal. Also, the particle size of the positive electrode active material is not particularly limited and may be within a range applicable to the positive electrode active material of a normal all-solid-state lithium ion secondary battery. Further, 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 the positive electrode of a normal all-solid-state lithium ion secondary battery.

[0069] Of course, those having a coating layer on the surface of the compound can also be used, or the compound and a compound having a coating layer can be mixed and used. This coating layer may contain 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 the coating element contained in the coating layer include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The coating layer formation process may use any coating method as long as such an element can be used to coat the compound without adversely affecting the physical properties of the positive electrode active material (for example, spray coating, dipping method, etc.). Since this is well understood by those skilled in the art, detailed description thereof is omitted.

[0070] Specific examples of the coating layer include Li2O-ZrO2 and the like.

[0071] 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.

[0072] 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 agent, a binder, a filler, a dispersant, or an ion-conductive auxiliary agent, as appropriate.

[0073] Examples of the conductive agent 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.

[0074] (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).

[0075] The negative electrode current collector 22 may be in the form of a plate or foil. The negative electrode current collector 22 may contain 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.

[0076] 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 a 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 lithium-based metal layer (26) 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).

[0077] The negative electrode active material layer (24) may contain carbon particles, metal fluoride particles, and a binder. The binder can stabilize the negative electrode active material layer (24) on the negative electrode current collector (22). Examples of materials constituting the binder include resin materials such as styrene butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, and polyethylene. The binder can be composed of one or more resin materials selected from these resin materials.

[0078] 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, ion conductors, etc. Specific examples of the additives are the same as those described above for the positive electrode.

[0079] The total thickness of the negative electrode active material layer (24) is not particularly limited, and 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) is high, 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 at an appropriate level.

[0080] Meanwhile, 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.

[0081] The negative electrode current collector 22 does not react with lithium metal, but it can make it difficult to deposit a smooth lithium metal layer on top of it. The film can also be used as a wetting layer to deposit lithium metal evenly on top of the negative electrode current collector 22.

[0082] The material used in the film, which can form an alloy with lithium metal, can include silicon, magnesium, aluminum, lead, silver, tin, or a combination thereof. The material used in the film, which can form a compound with lithium metal, can include carbon, titanium sulfide, iron sulfide, or a combination thereof. The content of the material used in the film can be small as long as it does not affect the electrochemical properties and / or redox potential of the electrode. The film can 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 can be applied by physical vapor deposition (e.g., evaporation or sputtering), chemical vapor deposition, plating, or other methods.

[0083] 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.

[0084] (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.

[0085] 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 any 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 such sulfide-based solid electrolyte materials, or may be made of two or more materials.

[0086] The sulfide-based solid electrolyte may include a solid electrolyte represented by the following chemical formula 1:

[0087] [Chemical formula 1] Li x M' y PSz A w In the above Chemical Formula 1, x, y, z, and w are independently from each other between 0 and 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.

[0088] As the solid electrolyte, the sulfide solid electrolyte material containing sulfur (S), phosphorus (P), and lithium (Li) as constituent elements can be used. For example, a material containing Li2S-P2S5 can be used. When a material containing Li2S-P2S5 is used as the sulfide solid electrolyte material, the molar ratio of Li2S to P2S5 can be selected, for example, from the range of Li2S:P2S5 = 50:50 to 90:10.

[0089] The solid electrolyte may be in an amorphous state or a crystalline state, or may be in a mixed state of amorphous and crystalline.

[0090] The solid electrolyte layer (30) may further contain 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).

[0091] (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.

[0092] [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. The all-solid-state lithium-ion secondary battery 100 according to one embodiment can be obtained by manufacturing the positive electrode 10, the negative electrode 20, and the solid electrolyte layer 30, and then laminating these layers together.

[0093] (1) Positive electrode manufacturing process The manufacturing process of the positive electrode will be described below using 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 the positive electrode (10). In this case, the pressing step is omitted.

[0094] (2) Negative electrode manufacturing process The manufacturing process of the negative electrode will be described below by way of example. First, materials constituting the negative electrode active material layer (24) (carbon particles, metal fluoride particles, binder, etc.) are added to a polar or nonpolar solvent to prepare a slurry (which may be a paste). Next, the obtained slurry is applied to a prepared negative electrode current collector (22) to form the negative electrode active material layer.

[0095] When the negative electrode active material layer further includes one or more additional layers, the additional layers may be stacked in the same manner as above.

[0096] Subsequently, 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.

[0097] Although the method for forming a two-layer negative electrode active material layer 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 in the stacking order using the method described above.

[0098] (3) Manufacturing process of the solid electrolyte layer The solid electrolyte layer 30 can be made of a solid electrolyte containing, for example, a sulfide-based solid electrolyte material.

[0099] 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.

[0100] Furthermore, when mechanical milling is used, the starting materials can be stirred and reacted using a ball mill or the like to produce a sulfide-based solid electrolyte material. The stirring speed and stirring time in mechanical milling are not particularly limited, but the faster the stirring speed, the faster the rate at which the sulfide-based solid electrolyte material is produced, and the longer the stirring time, the higher the conversion rate of the raw materials to the sulfide-based solid electrolyte material.

[0101] The resulting mixed raw material (material for the sulfide-based solid electrolyte) is then heat-treated at a predetermined temperature and then pulverized to produce a particulate solid electrolyte. If the solid electrolyte has a glass transition temperature, the heat treatment may change it from amorphous to crystalline.

[0102] The solid electrolyte obtained by the above method can then be formed into a film using a known film formation method, such as an aerosol deposition method, a cold spray method, or a sputtering method, to produce a solid electrolyte layer 30. Alternatively, the solid electrolyte layer 30 can be produced by compressing solid electrolyte particles. Alternatively, the solid electrolyte layer 30 can be produced by mixing a solid electrolyte with a solvent and a binder, applying the mixture, drying it, and pressurizing it.

[0103] (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 applying pressure thereto using, for example, hydrostatic pressure.

[0104] 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.

[0105] [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.

[0106] In the method for charging the all-solid-state lithium-ion secondary battery (100) according to one embodiment, the all-solid-state lithium-ion secondary battery (100) may be charged beyond the charge capacity of the negative electrode active material layer (24) (i.e., overcharged).

[0107] During the initial stage of charging, lithium may be adsorbed within the negative electrode active material layer (24). When the negative electrode active material layer (24) is charged beyond its charge capacity, as shown in FIG. 2 , lithium may be deposited on the back surface of the negative electrode active material layer (24), i.e., between the negative electrode current collector (22) and the negative electrode 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 negative electrode active material layer (24) and the metal layer (26) may ionize and migrate to the positive electrode (10). Therefore, in the all-solid-state lithium-ion secondary battery (100) of the present invention, lithium may be used as the negative electrode active material. Furthermore, the negative electrode 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 lithium dendrites. This can suppress short circuits and capacity reduction in the all-solid-state lithium-ion secondary battery 100, and can also improve 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 can reduce the manufacturing cost of the all-solid-state lithium-ion secondary battery 100.

[0108] 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 between the negative electrode current collector 22 and the negative electrode active material layer 24 and inside the negative electrode active material layer 24.

[0109] The all-solid-state lithium ion secondary battery (100) of the present invention may be manufactured 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.

[0110] 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, button, sheet, laminate, cylindrical, flat, and rectangular shapes. It can also be applied to large batteries used in electric vehicles. For example, the all-solid-state lithium-ion secondary battery (100) can also be used in hybrid vehicles such as plug-in hybrid electric vehicles (PHEVs). It can also be used in fields requiring large-volume power storage. For example, it can be used in electric bicycles or power tools.

[0111] Hereinafter, the present invention will be described in detail with reference to examples. However, the examples according to the present invention may be modified into various other 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 skilled in the art.

[0112] Preparation Example 1: Selection of carbon material samples with oxygen functional groups introduced Various types of commercially available carbon materials were purchased, and the oxygen content of each carbon material was analyzed using the method described below. Carbon black with an oxygen content of 5.2 at% (Sample 1), 2.6 at% (Sample 2), and 1.3 at% (Sample 3) were selected for use.

[0113] [Analysis method] (1)Analytical equipment Photoelectron spectroscopy (XPS or ESCA) K-Alpha (Thermo Fisher Scientific) (2)Analysis method First, the survey scan spectrum and narrow scan spectrum of each sample were obtained. The narrow scan spectrum was measured at four points for each position, and the average and deviation were calculated.

[0114] (3) ESCA common experimental conditions X-ray source:Monochromated Al Ka(1486.6eV) X-ray spot size: 400 μm Operation mode: CAE (Constant Analyzer Energy) mode Survey scan: pass energy 200eV, energy step 1eV Narrow scan:scanned mode, pass energy 50eV, energy step 0.1eV Charge compensation: flood gun off SF:Al THERMO1, ECF:TPP-2M, BG subtraction:Smart

[0115] [Table 1]

[0116] Example 1-1: Preparation of negative electrode active material slurry 6 g of carbon black (containing an oxygen concentration of 5.2 at%) with a particle size (D50) of 41 nm, 2 g of AgF with a particle size (D50) of 10 to 20 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 at 1800 rpm for 3 minutes each 12 times. After that, an additional 6 g of NMP solution was added, and the mixture was mixed at 1800 rpm for 3 minutes each 5 times to produce the negative electrode active material slurry of Example 1.

[0117] Example 1-2: Preparation of negative electrode active material slurry A negative electrode active material slurry was prepared in the same manner as in Example 1, except that LiF having a particle size of 10 nm to 20 nm was used instead of AgF.

[0118] Example 1-3: Preparation of negative electrode active material slurry A negative electrode active material slurry was prepared in the same manner as in Example 1, except that ZnF2 having a particle size (D50) of 10 nm to 20 nm was used instead of AgF.

[0119] Example 1-4: Preparation of negative electrode active material slurry A negative electrode active material slurry was prepared in the same manner as in Example 1, except that carbon black (containing an oxygen concentration of 2.6 at%) having a particle size (D50) of 50 nm was used instead of carbon black (containing an oxygen concentration of 5.2 at%), and ZnF2 having a particle size (D50) of 10 nm to 20 nm was used instead of AgF.

[0120] Example 1-5: Preparation of negative electrode active material slurry A negative electrode active material slurry was prepared in the same manner as in Example 1, except that carbon black (containing an oxygen concentration of 1.3 at%) having a particle size (D50) of 40 nm was used instead of carbon black (containing an oxygen concentration of 5.2 at%), and ZnF2 having a particle size (D50) of 10 nm to 20 nm was used instead of AgF.

[0121] Example 1-6: Preparation of negative electrode active material slurry 6 g of carbon black (containing an oxygen concentration of 5.2 at%) with a particle size (D50) of 41 nm, 1.1 g of AgF with a particle size (D50) of 10 to 20 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 at 1800 rpm for 3 minutes each 12 times. After that, an additional 6 g of NMP solution was added, and the mixture was mixed at 1800 rpm for 3 minutes each 5 times to produce the negative electrode active material slurry of Example 1.

[0122] Comparative Example 1-1: Preparation 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 60 nm was used instead of 2 g of AgF.

[0123] Comparative Example 1-2: Preparation of negative electrode active material slurry 6 g of carbon black (containing an oxygen concentration of 5.2 at%) with a particle size (D50) of 41 nm, 0.7 g of AgF with a particle size (D50) of 10 to 20 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 at 1800 rpm for 3 minutes each 12 times. After that, an additional 6 g of NMP solution was added, and the mixture was mixed at 1800 rpm for 3 minutes each 5 times to produce the negative electrode active material slurry of Example 1.

[0124] Comparative Example 1-3: Preparation of negative electrode active material slurry A negative electrode active material slurry was prepared in the same manner as in Example 1, except that 22 g of MgF having a particle size (D50) of 40 nm to 60 nm was used instead of 2 g of AgF.

[0125] Comparative Example 1-4: Preparation of negative electrode active material slurry A negative electrode active material slurry was prepared in the same manner as in Example 1, except that carbon black (containing an oxygen concentration of 1.3 at%) having a particle size (D50) of 40 nm was used instead of carbon black (containing an oxygen concentration of 5.2 at%), and MgF2 having a particle size (D50) of 35 nm to 45 nm was used instead of AgF.

[0126] Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4: Production of negative electrodes The negative electrode active material slurries prepared in Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4 were blade-coated on SUS foil to a thickness of 10 μm and dried to prepare negative electrodes (1.2 mAh / cm) of Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4. 2 ) was manufactured.

[0127] Manufacture of all-solid-state lithium-ion secondary batteries of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4 The positive electrode has a positive electrode active material on the current collector with a capacity of 5mAh / cm 2The positive electrode loaded with the above-mentioned Cr-Fe-Nb-Fe-Cu-O-Py ...

[0128] Experimental example 1: Battery characteristic evaluation The pouch-type mono-cells of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4 were operated in an operating voltage range of 4.25 V to 3.0 V and at an operating temperature of 60° C. to evaluate cycle characteristics. The results are shown in Table 2 below.

[0129] [Table 2A]

[0130] [Table 2B]

Claims

1. a current collector and an active material layer, The active material layer is made of carbon particles and AgF, LiF, ZnF ２ , AlF ３ , CaF ２ , CoF ３ , CuF ２ , NiF ２ , CoF ２ A negative electrode comprising one or more metal fluoride particles selected from the group consisting of:

2. The anode according to claim 1 , wherein the metal fluoride particles are contained in an amount of 15 parts by weight or more and 50 parts by weight or less, based on 100 parts by weight of the total weight of the carbon material particles and the metal fluoride particles.

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

5.

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

5. 2. The negative electrode according to claim 1, wherein the active material layer comprises 60% by weight or more and 80% by weight or less of carbon particles, 15% by weight or more and 30% by weight or less of metal fluoride particles, and 3% by weight or more and 20% by weight or less of a binder.

6. 2. The negative electrode according to claim 1, wherein the carbon particles contain oxygen in an amount of 3 at % or more and 10 at % or less.

7. The negative electrode according to claim 6 , wherein the oxygen is present in a form contained in a functional group bonded to the carbon material particle.

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

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. The lithium ion secondary battery according to claim 10, wherein the lithium ion secondary battery is an anodeless battery.

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