Negative electrode and lithium ion secondary battery comprising same

Abstract

The present invention provides a negative electrode and a lithium ion secondary battery comprising the same, in which the negative electrode comprises a current collector and an active material layer, and the active material layer comprises particles of a carbon material and particles of at least one metal fluoride selected from the group consisting of AgF, LiF, ZnF2, AlF3, CaF2, CoF3, CuF2, NiF2, and CoF2.

Description

Technical Field

[0001] This application claims the benefit of and priority to 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, the disclosures of which are incorporated herein by reference in their entirety.

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

[0003] Recently, all-solid-state secondary batteries using solid electrolytes as electrolytes have received attention. In order to improve the energy density of these 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, by using lithium as a negative electrode active material, it is possible to increase power output while thinning the all-solid-state secondary battery.

[0004] For example, as an all-solid-state lithium ion secondary battery, an anode-less lithium ion secondary battery including a negative electrode active material layer having a metal that forms an alloy with lithium and a carbon material is known.

[0005] The anode-free lithium-ion secondary battery as described above is driven by the following mechanism: metallic lithium is deposited in the negative electrode active material layer and between the negative electrode active material layer and the current collector during charge, and is ionized and migrates to the positive electrode during discharge.

[0006] The negative electrode active material layer is composed of a carbon material and a metal material (eg, Ag), and various materials are required to improve the driving characteristics and life characteristics of the battery.

[0007] [Prior art literature]

[0008] [Patent Document]

[0009] Korean Patent Application No. 10-2015-0064697 Summary of the Invention

[0010] [Technical Issues]

[0011] The present invention aims to provide a negative electrode capable of improving the driving characteristics and life characteristics of a battery, and a lithium ion secondary battery including the negative electrode.

[0012] [Technical solution]

[0013] In order to achieve the above object, the present invention provides a negative electrode comprising a current collector and an active material layer.

[0014] The active material layer comprises carbon material particles and at least one metal fluoride particle selected from the group consisting of AgF, LiF, ZnF2, AlF3, CaF2, CoF3, CuF2, NiF2 and CoF2.

[0015] The present invention also provides a lithium ion secondary battery, which comprises: a negative electrode; a positive electrode; and an electrolyte arranged between the negative electrode and the positive electrode.

[0016] [Beneficial Effects]

[0017] The negative electrode of the present invention includes a negative electrode active material layer in the form of a mixture of carbon material particles and metal fluoride particles, which provides effects of improving driving characteristics and life characteristics of a battery.

[0018] Furthermore, by including the above-described negative electrode active material layer, the lithium ion secondary battery of the present invention provides excellent driving characteristics and life characteristics. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 and Figure 2 is a schematic cross-sectional view of the structure of the lithium-ion secondary battery of the present invention. DETAILED DESCRIPTION

[0020] Hereinafter, the present invention is described in more detail to provide a better understanding of the present invention.

[0021] The terms and words used in this specification and claims should not be interpreted as their ordinary meanings or dictionary meanings, but rather as meanings and concepts consistent with the technical ideas of the present invention based on the principle that the inventor can appropriately define the concepts of the terms to best describe his invention. In addition, the terms used in this specification are only used to describe exemplary embodiments and are not intended to limit the present invention. Unless the context clearly indicates otherwise, singular expressions include plural expressions.

[0022] When a component is referred to as being “connected to, provided with, or mounted on” another component, it should be understood that it can be directly connected to or mounted on the component, but other components may exist between them. On the other hand, when a component is referred to as being “directly connected to or directly mounted on” another component, it should be understood that there are no other components between them. Other expressions describing the relationship between components, for example, “on” and “directly on,” “between” and “directly between,” or “adjacent” and “directly adjacent,” should be interpreted similarly.

[0023] As used herein, unless otherwise indicated, the term "combination" is inclusive of mixtures, alloys, and reaction products.

[0024] The negative electrode of the present invention comprises a current collector and an active material layer, wherein the active material layer comprises carbon material particles and one or more metal fluoride particles selected from the group consisting of AgF, LiF, ZnF2, AlF3, CaF2, CoF3, CuF2, NiF2 and CoF2.

[0025] In one embodiment of the present invention, the content of the metal fluoride particles may be 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.

[0026] In the above, if the content of metal fluoride is less than 15 parts by weight, it is insufficient to form an alloy with lithium, so the benefit of reducing the activation energy of alloying by adding metal fluoride cannot be achieved, and if it exceeds 50 parts by weight, the storage capacity of lithium is reduced, resulting in overall capacity degradation and reduced high-rate discharge characteristics, so this is not preferred.

[0027] In one embodiment of the present invention, the ratio of the carbon material particle diameter (D50) to the metal fluoride particle diameter (D50) may be 1: 0.03 to 1.5, 1: 0.1 to 0.7, or 1: 0.2 to 0.7. If the ratio of the metal fluoride particle diameter exceeds 1.5, the dispersibility in the electrode slurry will be affected, resulting in problems such as reduced coating performance and electrode uniformity. In addition, if the ratio of the metal fluoride particle diameter is less than 0.03, the specific surface area of the carbon material particles and the metal fluoride particles increases significantly, and the amount of the binder and solvent used increases significantly, resulting in problems such as capacity degradation and increased resistance, so this is not preferred.

[0028] In one embodiment of the present invention, the carbon material particles and the metal fluoride particles may be included in the form of a random mixture.

[0029] In one embodiment of the present invention, the carbon material particles may be, for example, amorphous carbon material particles. Specific examples of amorphous carbon materials include carbon black, such as acetylene black, furnace black, or Ketjen black, graphene, or a combination thereof. When the carbon material particles have a high degree of crystallinity, lithium insertion and removal become difficult, which leads to the disadvantage of increasing the resistance of the battery cell.

[0030] If the amorphous carbon material particles contain pores, the pore diameter may be 1 nm or less, preferably 0.5 nm or less. However, more preferably, the amorphous carbon material particles do not contain pores. This is because if the amorphous carbon material particles contain pores, lithium may be deposited in the pores, and such lithium may be deactivated. The amount of deactivated lithium may increase with repeated charging and discharging.

[0031] For example, the pore size of the amorphous carbon material particles can be measured by nitrogen adsorption experiments or by transmission electron microscopy.

[0032] In one embodiment of the present invention, carbon material particles having a particle size (D50) of 10 nm to 150 nm, preferably 20 nm to 100 nm, may be used.

[0033] In one embodiment of the present invention, the carbon material particles may contain 3 to 10 atomic % of oxygen based on all elements contained in the carbon material particles. If the oxygen content is less than 3 atomic %, it is not preferred because the surface roughness of the active material layer is degraded, and if the oxygen content is greater than 10 atomic %, it is not preferred because side reactions with the solid electrolyte degrade the battery cell performance.

[0034] In the above, the lower limit of the oxygen content may be 3.5 atomic % or more, 4 atomic % or more, or 4.5 atomic % or more. In addition, the upper limit of the oxygen content may be 9.5 atomic % or less, 9 atomic % or less, 8 atomic % or less, 7.5 atomic % or less, 7 atomic % or less, 6.5 atomic % or less, 6 atomic % or less, or 5.5 atomic % or less. The oxygen content may be within a range including combinations of the above lower and upper limits. Specifically, the oxygen content may more preferably be 5 atomic % to 10 atomic %.

[0035] In one embodiment of the present invention, oxygen may be present in the form of functional groups bound to the carbon material particles. Further, the functional groups may include one or more selected from the group consisting of carboxyl, hydroxyl, ether, ester, aldehyde, carbonyl, and amide groups.

[0036] For example, carbon material particles containing 3 to 10 atomic percent oxygen can be prepared by oxidizing the carbon material. Specifically, oxygen functional groups can be introduced into the surface of the carbon material by treating the carbon material with an acid and reacting it at a temperature of 25°C to 60°C with stirring. The type of acid is not particularly limited and can be any acid capable of introducing oxygen functional groups into the surface of the carbon material. The acid can be, for example, sulfuric acid, nitric acid, or a mixture thereof. Oxidants such as potassium permanganate can also be used.

[0037] Carbon materials containing oxygen can be manufactured and used directly or purchased.

[0038] The oxygen content in the carbon material can be measured using photoelectron spectroscopy (XPS or ESCA), for example, using a K-Alpha device (Thermo Fisher Scientific).

[0039] In one embodiment of the present invention, oxygen may exist on the surface of the carbon material particles. The surface does not necessarily refer to only the outer surface of the carbon material particles, but also includes the surface of the pores (if any).

[0040] In one embodiment of the present invention, metal fluoride particles having a particle size (D50) of 10 nm to 150 nm, preferably 20 nm to 100 nm, may be used.

[0041] In one embodiment of the present invention, the active material layer may include 60% to 80% by weight of carbon material particles, 15% to 30% by weight of metal fluoride particles, and 3% to 20% by weight of a binder. For example, the binder may be a resin material such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, etc. The binder may be composed of at least one selected from these resin materials.

[0042] In one embodiment of the present invention, the carbon material particles and the metal fluoride particles may be included in the form of a carbon material-metal fluoride composite.

[0043] In anode-less batteries, the negative electrode active layer is formed into a microfilm, and it is very difficult to form a conventional active material composite with a small particle size. In other words, if the particle size of the active material composite is too large for the microfilm, it is difficult to form a negative electrode active layer with good surface roughness, and this reduction in surface roughness leads to a decrease in the driving characteristics of the battery.

[0044] The present invention provides a significant improvement over the aforementioned problems of the prior art. Specifically, the carbon material-metal fluoride composite of the present invention forms a carbon material-metal fluoride composite having a significantly smaller particle size than when using conventional carbon materials. The carbon material containing at least 3 atomic % of oxygen that forms the composite has the characteristics of being well mixed with the metal fluoride particles and uniformly distributed with the metal fluoride particles. Therefore, a carbon material-metal fluoride composite having excellent component uniformity can be produced. Furthermore, due to the above reasons, a carbon material-metal fluoride composite having a small and uniform particle size can be produced.

[0045] In one embodiment of the present invention, the carbon material-metal fluoride composite can be formed by one or more bonds selected from the group consisting of chemical bonds between carbon material particles and metal fluoride particles, van der Waals bonds between carbon material particles and metal fluoride particles, and bonds between carbon material particles and metal fluoride particles formed by a binder. The chemical bonds can be bonds between metal fluoride particles and oxygen contained in the carbon material.

[0046] In one embodiment of the present invention, the carbon material-metal fluoride composite may include 60 to 80 wt % of the carbon material, 15 to 30 wt % of the metal fluoride, and 3 to 20 wt % of the binder, based on the total weight.

[0047] The binder may be used in a wet process for preparing the carbon material-metal fluoride composite, wherein the binder is dissolved in a solvent together with the carbon material particles and the metal fluoride particles, wherein the carbon material-metal fluoride composite may contain the binder.

[0048] 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.

[0049] Furthermore, 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.

[0050] It is very important to produce a carbon material-metal fluoride composite with a smaller particle size because, if the particle size of the carbon material-metal fluoride composite is too large compared with the microfilm, it is difficult to form a negative electrode active material layer with good surface roughness and the driving characteristics of the battery are reduced.

[0051] 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, the contact with the electrolyte layer is insufficient on the electrolyte side, and it is not conducive to the uniform precipitation of lithium on the negative electrode current collector side.

[0052] In an anode-free lithium ion secondary battery, the thickness of the negative electrode active material layer may generally be 1 μm to 100 μm, or 10 μm to 60 μm, and specifically, the thickness may be 10 μm, 20 μm, 30 μm, 40 μm, or 50 μm.

[0053] For example, it is obvious that if a carbon material-metal fluoride composite having a particle size of 10 μm is used to form a negative electrode active material layer having a thickness of 20 μm, it is difficult to achieve the desired surface roughness.

[0054] If the maximum particle size of the carbon material-metal fluoride composite is 3 μm or less, it is preferable because the effect of improving surface roughness can be more reliably obtained. On the other hand, if it exceeds 3 μm, it is difficult to obtain excellent surface roughness when forming a thin film.

[0055] The particle size of the carbon material-metal fluoride composite can be measured using a particle size analyzer. For example, the particle size can be measured using a Mastersizer 3000 (Malvern Panalytical).

[0056] The present invention provides a negative electrode active material layer comprising the above-mentioned carbon material-metal fluoride composite.

[0057] The negative electrode active material layer has uniformly distributed carbon material and metal fluoride and has excellent surface roughness, which improves driving characteristics of a lithium ion secondary battery including the negative electrode active material layer.

[0058] The present invention also provides a lithium ion secondary battery comprising a negative electrode, a positive electrode and an electrolyte arranged between the negative electrode and the positive electrode.

[0059] The lithium-ion secondary battery may be an anode-less battery.

[0060] By including the negative electrode active material layer of the present invention, the lithium ion secondary battery provides improved driving characteristics and lifespan characteristics.

[0061] In one embodiment of the present invention, the solid electrolyte may be a sulfide-based solid electrolyte.

[0062] In one embodiment of the present invention, the lithium ion secondary battery may be an anode-less battery.

[0063] The following describes embodiments of the present invention in more detail.

[0064] <Composition of All-Solid-State Lithium-Ion Secondary Battery>

[0065] Figure 1 is a cross-sectional view illustrating a schematic configuration of an all-solid-state lithium-ion secondary battery according to one embodiment of the present invention.

[0066] 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 the positive electrode 10 and the negative electrode 20. Specifically, Figure 1 As shown, the all-solid-state lithium-ion secondary battery 100 includes 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 .

[0067] (1) Positive electrode

[0068] like Figure 1 As shown, the positive electrode 10 includes a positive electrode current collector 12 and a positive electrode active material layer 14 which are sequentially disposed toward the negative electrode 20 .

[0069] The positive electrode current collector 12 may be a plate or foil. For example, the positive electrode current collector 12 may be a metal selected from indium, copper, magnesium, stainless steel, titanium, iron, cobalt, nickel, zinc, aluminum, germanium, and lithium, or an alloy of two or more metals.

[0070] The positive electrode active material layer 14 can reversibly absorb and release lithium ions. The positive electrode active material layer 14 can include a positive electrode active material and a solid electrolyte.

[0071] The positive electrode active material may be a compound capable of inserting / deinserting lithium. Examples of compounds capable of inserting or deinserting lithium may be represented by any of the following: Li a A 1-b B' b D'2 (where 0.90≤a≤1.8, and 0≤b≤0.5); Li a E 1- b B' b O 2-c D' c (where 0.90≤a≤1.8, 0≤b≤0.5, and 0≤c≤0.05); LiE 2-b B' b O 4-c D' c (where 0≤b≤0.5, and 0≤c≤0.05); Li a Ni 1-b-c Co b B' c D' α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2); Li a Ni 1-b-c Co b B' c O 2-α F' α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); Li a Ni 1-b-c Mn b B' c D' α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α≤2);

[0072] Li a Ni 1-b-c Mn b B' c O 2-α F' α (where 0.90≤a≤1.8, 0≤b≤0.5, 0≤c≤0.05, and 0<α<2); Li a Ni b E c G d O2 (where 0.90≤a≤1.8, 0≤b≤0.9, 0≤c≤0.5, and 0.001≤d≤0.1); Li a Ni b Co c Mn dG e O2 (where 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 (where 0.90≤a≤1.8, and 0.001≤b≤0.1); Li a CoG b O2 (where 0.90≤a≤1.8, and 0.001≤b≤0.1); Li a MnG b O2 (where 0.90≤a≤1.8, and 0.001≤b≤0.1); Li a Mn2G b O4 (where 0.90≤a≤1.8 and 0.001≤b≤0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiI'O2; LiNiVO4; Li (3-f) J2(PO4)3(0≤f≤2);Li (3-f) Fe2(PO4)3(0≤f≤2); and LiFePO4.

[0073] In the above formula, A is Ni, Co, Mn or a combination thereof; B' is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element or a combination thereof; D' is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; F' is F, S, P or any combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or any combination thereof; Q is Ti, Mo, Mn or any combination thereof; I' is Cr, V, Fe, Sc, Y or any combination thereof; J is V, Cr, Mn, Co, Ni, Cu or any combination thereof.

[0074] Specific examples of these positive electrode active materials include lithium cobalt oxide (hereinafter referred to as LCO), lithium nickel oxide, lithium nickel cobalt oxide, lithium nickel cobalt aluminum oxide (hereinafter referred to as NCA), 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 selected from these compounds or two or more selected from these compounds as the positive electrode active material.

[0075] 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" refers to 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, such that each layer of atoms forms a two-dimensional plane. The "cubic rock salt structure" also refers to the sodium chloride type structure (one of the crystal structures). For example, the "cubic rock salt structure" refers to a structure in which a face-centered cubic lattice formed by cations and anions is arranged in such a way that they are offset from each other by 1 / 2 of the unit lattice angle.

[0076] The lithium salt of a transition metal oxide having such a layered rock salt structure may be a ternary lithium transition metal oxide, such as LiNi x Co y Al z O2 (NCA) or LiNi x Co y Mn z O2 (NCM) (where 0 < x < 1, 0 < y < 1, 0 < z < 1 and x + y + z = 1). The positive electrode active material layer 14 may contain a lithium salt of a ternary transition metal oxide having such a layered rock salt structure as the positive electrode active material to improve the energy density and thermal stability of the all-solid-state lithium ion secondary battery 100.

[0077] Here, the shape of the positive electrode active material may be, for example, a particulate shape such as an ellipsoidal shape or a spherical shape. In addition, the particle size of the positive electrode active material is not particularly limited and may be within the range applicable to the positive electrode active material of a conventional all-solid-state lithium ion secondary battery. In addition, the content of the positive electrode active material in the positive electrode active material layer 14 is not particularly limited and may be within the range applicable to the positive electrode of a conventional all-solid-state lithium ion secondary battery.

[0078] Of course, a compound having a coating layer on its surface may also be used, or a mixture of the compound and a compound having a coating layer may be used. The coating layer may contain a coating element compound, such as an oxide of the coating element, a hydroxide, a hydroxyoxide of the coating element, an oxycarbonate of the coating element, or a hydroxycarbonate of the coating element. The compound constituting the coating layer may be amorphous or crystalline. The coating elements included in the coating layer may include Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof. The formation process of the coating layer may be carried out by any coating method (such as a spraying or dipping method), as long as the compound can be coated with these elements in a manner that does not adversely affect the properties of the positive electrode active material, which is well known to those skilled in the art and will not be described in detail.

[0079] Specific examples of the above coating layer include Li2O-ZrO2.

[0080] 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 later.

[0081] In addition to the above-described positive electrode active material and solid electrolyte, the positive electrode active material layer 14 may be appropriately combined with additives such as a conductive agent, a binder, a filler, a dispersant, or an ion conductivity aid.

[0082] For example, the conductive agent can be graphite, carbon black, acetylene black, Ketjen black, carbon fiber or metal powder. For example, the binder can include styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride or polyethylene. In addition, any material commonly used in the electrode of all-solid-state lithium ion secondary battery can be used as filler, dispersant or ion conductive auxiliary agent.

[0083] (2) Negative electrode

[0084] The negative electrode 20 may include a negative electrode current collector 22 and a negative electrode active material layer 24 which are sequentially disposed toward the positive electrode 10 .

[0085] The negative electrode current collector 22 may be a plate or foil. The negative electrode current collector 22 may include a material that does not react with lithium, in other words, does not form an alloy or compound with lithium. Materials constituting the negative electrode current collector 22 may include, for example, copper, stainless steel, titanium, iron, cobalt, and nickel. The negative electrode current collector 22 may be composed of one of these metals, or may be composed of an alloy or cladding material of two or more metals.

[0086] In the initial state or the fully discharged state, the negative electrode active material layer 24 may not contain lithium in the negative electrode current collector 22, in the negative electrode active material layer 24, or between the negative electrode active material layer 24 and the solid electrolyte layer 30. As described later, when the all-solid-state lithium ion secondary battery 100 of one embodiment is overcharged, as shown in FIG. Figure 2 As shown, the active material contained in the negative electrode active material layer 24 and the lithium ions that have migrated from the positive electrode 10 can form an alloy or compound, and a metal layer 26 containing lithium as a main component can be formed (deposited) on the negative electrode 20. The metal layer 26 can be deposited and arranged between the negative electrode current collector 22 and the negative electrode active material layer 24, inside the negative electrode active material layer 24, or both. Between the negative electrode current collector 22 and the negative electrode active material layer 24, the lithium-based metal layer 26 can be arranged closer to the negative electrode current collector 22 than the negative electrode active material layer 24.

[0087] The negative electrode active material layer 24 may include carbon material particles, metal fluoride particles, and a binder. By including the binder, the negative electrode active material layer 24 can be stabilized on the negative electrode current collector 22. For example, the material constituting the binder may be a resin material such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, or polyethylene. The binder may include one or more selected from these resin materials.

[0088] The negative electrode active material layer 24 can also be appropriately formulated with additives used in conventional all-solid-state lithium ion secondary batteries (such as fillers, dispersants, or ion conductors). Specific examples of these additives are the same as those described above for the positive electrode.

[0089] The total thickness of the negative electrode active material layer 24 is not particularly limited, but may be 1 μm to 100 μm or 10 μm to 60 μm. If the thickness of the negative electrode active material layer 24 is less than 1 μm, the performance of the all-solid-state secondary battery may not be sufficiently improved. If the thickness of the negative electrode active material layer 24 exceeds 100 μm, the resistance of the negative electrode active material layer 24 may be high, resulting in insufficient improvement in the performance of the all-solid-state secondary battery. 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.

[0090] Meanwhile, the negative electrode current collector 22 may further include a film containing a material capable of forming an alloy or a compound with lithium, wherein the film is provided between the negative electrode current collector 22 and the negative electrode active material layer.

[0091] 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 it. The film can also serve as a wetting layer, allowing lithium metal to be smoothly deposited on the negative electrode current collector 22.

[0092] The material capable of forming an alloy with lithium metal used in the film may include silicon, magnesium, aluminum, lead, silver, tin or a combination thereof. The material capable of forming a compound with lithium metal used in the film may include carbon, titanium sulfide, iron sulfide or a combination thereof. The content of the material used in the film may be a small amount without affecting the electrochemical properties of the electrode and / or the redox potential of the electrode. The film can be applied flatly on the negative electrode current collector 22 to prevent cracking during the charging cycle of the all-solid-state lithium ion secondary battery 100. The film can be applied by physical deposition (such as evaporation or sputtering), chemical deposition or electroplating.

[0093] 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.

[0094] (3) Solid electrolyte layer

[0095] The solid electrolyte layer 30 is provided between the positive electrode 10 and the negative electrode 20 (for example, between the positive electrode active material layer 14 and the negative electrode active material layer 24). The solid electrolyte layer 30 includes a solid electrolyte capable of ion migration. The solid electrolyte layer 30 may include a sulfide-based solid electrolyte.

[0096] The above-mentioned sulfide solid electrolytes may include Li2S-P2S5, Li2S-P2S5-LiX (wherein X is a halogen atom), Li2S-P2S5-Li2O, Li2S-P2S5-Li2O-LiI, Li2S-SiS2, Li2S-SiS2-LiI, Li2S-SiS2-LiBr, Li2S-SiS2-LiCl, Li2S-SiS2-B2S3-LiI, Li2S-SiS2-P2S5-LiI, Li2S-B2S3, Li2S-P2S5-Z m S n (where m and n are positive numbers, and Z is any one of Ge, Zn, and Ga), Li2S-GeS2, Li2S-SiS2-Li3PO4, Li2S-SiS2-Li p MO q (wherein p and q are positive numbers, and M is any one of P, Si, Ge, B, Al, Ga, and In) and combinations thereof. The solid electrolyte may include one or more materials selected from these sulfide-based solid electrolyte materials.

[0097] The sulfide-based solid electrolyte may include a solid electrolyte represented by the following formula 1:

[0098] <Formula 1>

[0099] Li x M' y PS z A w ,

[0100] wherein x, y, z, and w are each independently 0 or greater and 6 or less;

[0101] M' is at least one of As, Ge, Ga, Sb, Si, Sn, Al, In, Ti, V, Nb, and Ta;

[0102] A is at least one of F, Cl, Br and I.

[0103] As a solid electrolyte, a sulfide solid electrolyte material may contain sulfur (S), phosphorus (P), and lithium (Li) as components. For example, a composition containing Li2S-P2S5 may be used. When a sulfide solid electrolyte material containing Li2S-P2S5 is used, the molar ratio of Li2S to P2S5 may be selected within a range of, for example, Li2S:P2S5 of 50:50 to 90:10.

[0104] Solid electrolytes can also be amorphous or crystalline. They can also be a mixture of amorphous and crystalline.

[0105] The solid electrolyte layer 30 may further include a binder. For example, the binder material may be a resin such as styrene-butadiene rubber (SBR), polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, or polyacrylic acid. The binder material may be the same as or different from the binder material constituting the positive electrode active material layer 14 and the negative electrode active material layer 24.

[0106] (4) Composition of all-solid-state lithium-ion secondary batteries

[0107] like Figure 1 As shown, 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 sequence.

[0108] <Method for Manufacturing All-Solid-State Lithium-Ion Secondary Battery>

[0109] Next, a method for manufacturing the all-solid-state lithium ion secondary battery 100 will be described. The all-solid-state lithium ion secondary battery 100 of one embodiment can be obtained by separately manufacturing the positive electrode 10, the negative electrode 20, and the solid electrolyte layer 30 and then stacking the layers.

[0110] (1) Cathode manufacturing process

[0111] An example of a positive electrode manufacturing process is as follows. First, the materials constituting the positive electrode active material layer 14 (i.e., positive electrode active material, binder, etc.) are added to a non-polar solvent to form a slurry (or paste). The slurry is then applied to the prepared positive electrode current collector 12. This is dried to obtain a laminate. The laminate is then pressurized using, for example, hydrostatic pressure to obtain the positive electrode 10. In this case, the pressurization process is omitted.

[0112] (2) Negative electrode manufacturing process

[0113] The negative electrode manufacturing process is described below by way of example. First, a slurry (a paste is also preferred) is prepared by adding the materials constituting the negative electrode active material layer 24 (i.e., carbon material particles, metal fluoride particles, binder, etc.) to a polar solvent or a non-polar solvent. The resulting slurry is then applied to the prepared negative electrode current collector 22 to form the negative electrode active material layer.

[0114] If the negative electrode active material layer further includes more than one layer, the additional layers may be stacked in the same manner as described above.

[0115] Then, for example, the laminate obtained by the above method is pressurized by hydrostatic pressure to produce the negative electrode 20. The method of applying the slurry to the negative electrode collector 22 is not particularly limited, and may be, for example, screen printing, metal mask printing, electrostatic spraying, dip coating, spray coating, roller coating, doctor blade coating, or gravure coating.

[0116] The method of forming two layers of negative electrode active material layers is described above, but even in the case of forming more layers, the negative electrode can be produced by preparing slurries forming each layer and sequentially stacking each layer according to the stacking order using the above method.

[0117] (3) Solid electrolyte layer manufacturing process

[0118] The solid electrolyte layer 30 may be made of a solid electrolyte including, for example, a sulfide-based solid electrolyte material.

[0119] First, the starting material (e.g., Li2S or P2S5) is processed by a melt quenching method or a mechanical grinding method to obtain a sulfide-based solid electrolyte material. For example, when using a melt quenching method, the starting material is mixed in a predetermined amount, granulated, reacted and quenched at a predetermined reaction temperature in a vacuum to produce a sulfide-based solid electrolyte material. In addition, the reaction temperature of the mixture of Li2S and P2S5 can be 400°C to 1000°C, for example, 800°C to 900°C. In addition, the reaction time can be 0.1 hours to 12 hours, for example, 1 hour to 12 hours. In addition, the quenching temperature of the reaction can be below 10°C, for example, below 0°C, and the quenching rate can be typically 1°C / second to 10000°C / second, for example, 1°C / second to 1000°C / second.

[0120] Furthermore, when using a mechanical milling method, a sulfide-based solid electrolyte material can be produced by stirring the starting materials using a ball mill and reacting them. Furthermore, the stirring speed and stirring time of the mechanical milling method are not particularly limited, but the faster the stirring speed, the faster the sulfide-based solid electrolyte material can be produced, and the longer the stirring time, the higher the conversion rate of the raw materials into the sulfide-based solid electrolyte material.

[0121] Then, the obtained mixed raw material (sulfide-based solid electrolyte material) is heat-treated at a predetermined temperature, and the solid electrolyte can be ground to produce a granular solid electrolyte. If the solid electrolyte has a glass transition point, it can be transformed from amorphous to crystalline by heat treatment.

[0122] The solid electrolyte obtained by the above method can then be screened using a known screening method, such as an aerosol positioning method, a cold spray method, or a sputtering method, to prepare a solid electrolyte layer 30. The solid electrolyte layer 30 can also be prepared by pressurizing the solid electrolyte particles. The solid electrolyte layer 30 can also be prepared by mixing the solid electrolyte with a solvent and a binder and drying and pressurizing the solid electrolyte layer 30.

[0123] (4) Lamination process

[0124] The all-solid-state lithium-ion secondary battery 100 of one embodiment can be obtained by providing the solid electrolyte layer 30 between the positive electrode 10 and the negative electrode 20 and pressurizing them using, for example, hydrostatic pressure.

[0125] The all-solid-state lithium-ion secondary battery 100 of the present invention does not require the use of end plates to apply high external pressure 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.

[0126] <Method for Charging All-Solid-State Lithium-Ion Secondary Batteries>

[0127] Next, a method of charging the all-solid-state lithium-ion secondary battery 100 is described.

[0128] According to one embodiment, the charging method of the all-solid-state lithium ion secondary battery 100 may be to charge the all-solid-state lithium ion secondary battery 100 to exceed the charge capacity of the negative active material layer 24 (ie, overcharge).

[0129] At the beginning of charging, lithium can be absorbed in the negative electrode active material layer 24. When charging exceeds the charge capacity of the negative electrode active material layer 24, as shown in FIG. Figure 2As shown, lithium can be deposited from the back side of the negative electrode active material layer 24, that is, deposited between the negative electrode current collector 22 and the negative electrode active material layer 24, and lithium can form a metal layer 26 that does not exist during manufacturing. During the discharge process, the lithium in the negative electrode active material layer 24 and the metal layer 26 can be ionized and migrate to the positive electrode 10 side. Therefore, in the all-solid-state lithium ion secondary battery 100 of the present invention, lithium can be used as the negative electrode active material. In addition, since the negative electrode active material layer 24 covers the metal layer 26, it can act as a protective layer for the metal layer 26, while suppressing the deposition and growth of dendritic metallic lithium. As a result, short circuits and capacity degradation of the all-solid-state lithium ion secondary battery 100 can be suppressed, and the characteristics of the all-solid-state lithium ion secondary battery 100 can be improved. In addition, according to one embodiment, the metal layer 26 is not formed in advance, which can reduce the manufacturing cost of the all-solid-state lithium ion secondary battery 100.

[0130] The metal layer 26 may also be formed inside the negative electrode active material layer 24, but is not limited to the Figure 2 The metal layer 26 is shown formed between the negative current collector 22 and the negative active material layer 24. In addition, the metal layer 26 may be formed between the negative current collector 22 and the negative active material layer 24 and inside the negative active material layer 24.

[0131] The all-solid-state lithium-ion secondary battery 100 of the present invention can be manufactured as a unit cell having a positive electrode / separator / negative electrode structure, a dual cell having a positive electrode / separator / negative electrode / separator / positive electrode structure, or a stacked cell repeating the above single unit cell structure.

[0132] The shape of the all-solid-state lithium ion secondary battery 100 of the present invention is not particularly limited, for example, can be coin-shaped, button-shaped, sheet-shaped, laminated, cylindrical, flat or angular. It can also be applied to the large-scale battery used in electric vehicles. For example, the all-solid-state lithium ion secondary battery 100 can be used in hybrid electric vehicles such as plug-in hybrid electric vehicles (PHEV). They can also be used in applications requiring a large amount of power storage. For example, it can be used in electric bicycles or power tools.

[0133] [Example]

[0134] Hereinafter, examples are provided to illustrate the present invention in detail. However, the embodiments of the present invention can be modified in many other ways, and the scope of the present invention should not be interpreted as being limited to the embodiments described below. Examples of the present invention are provided to more fully illustrate the present invention to those of ordinary skill in the art.

[0135] Preparation Example 1: Selecting a carbon material sample with oxygen functional groups introduced

[0136] Various commercially available carbon materials were purchased, and the oxygen content of each carbon material was analyzed as follows, selecting carbon black with 5.2 atomic % oxygen (sample 1), carbon black with 2.6 atomic % oxygen (sample 2), and carbon black with 1.3 atomic % oxygen (sample 3).

[0137] <Analysis Method>

[0138] (1) Analyzer

[0139] XPS or ESCA was performed using a K-Alpha (Thermo Fisher Scientific)

[0140] (2) Analytical methods

[0141] First, a full scan spectrum and a narrow scan spectrum were obtained for each sample. The narrow scan spectrum was measured at four points for each position, and the average value and deviation were obtained.

[0142] (3) ESCA conventional experimental conditions

[0143] X-ray source: monochromatic Al Ka (1486.6 eV)

[0144] X-ray spot size: 400 μm

[0145] Operation mode: Constant analyzer energy (CAE) mode

[0146] Full scan: pass energy 200eV, energy step 1eV

[0147] Narrow scan: Scan mode, pass energy 50eV, energy step 0.1eV

[0148] Charge compensation: overflow gun closed

[0149] SF:Al THERMO1, ECF:TP-2M, BG subtraction:Intelligent

[0150] [Table 1]

[0151]

[0152] Example 1-1: Preparation of negative electrode active material slurry

[0153] 6 g of carbon black (oxygen concentration of 5.2 atomic %) 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 (6% solids), and 6 g of NMP solution were placed in a Thinky mixer container and mixed at 1800 rpm for 12 times, each for 3 minutes. Then, an additional 6 g of NMP solution was added and mixed at 1800 rpm for 5 times, each for 3 minutes, to prepare the negative active material slurry of Example 1.

[0154] Example 1-2: Preparation of negative electrode active material slurry

[0155] A negative active material slurry was prepared in the same manner as in Example 1, except that LiF having a thickness of 10 nm to 20 nm was used instead of AgF.

[0156] Example 1-3: Preparation of negative electrode active material slurry

[0157] A negative electrode active material slurry was prepared in the same manner as in Example 1, except that ZnF 2 having a particle size (D50) of 10 nm to 20 nm was used instead of AgF.

[0158] Example 1-4: Preparation of negative electrode active material slurry

[0159] 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 atomic %) with a particle size (D50) of 50 nm was used instead of carbon black (containing an oxygen concentration of 5.2 atomic %), and ZnF2 with a particle size (D50) of 10 nm to 20 nm was used instead of AgF.

[0160] Example 1-5: Preparation of negative electrode active material slurry

[0161] 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 atomic %) with a particle size (D50) of 40 nm was used instead of carbon black (containing an oxygen concentration of 5.2 atomic %), and ZnF2 with a particle size (D50) of 10 nm to 20 nm was used instead of AgF.

[0162] Example 1-6: Preparation of negative electrode active material slurry

[0163] 6 g of carbon black (oxygen concentration of 5.2 atomic %) with a particle size (D50) of 41 nm, 1.1 g of AgF with a particle size of 10 to 20 nm, 9.33 g of PVdF binder (6% solids), and 6 g of NMP solution were placed in a Thinky mixer container and mixed at 1800 rpm for 12 times, each for 3 minutes. Then, an additional 6 g of NMP solution was added and mixed at 1800 rpm for 5 times, each for 3 minutes, to prepare the negative active material slurry of Example 1.

[0164] Comparative Example 1-1: Preparation of negative electrode active material slurry

[0165] A negative 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.

[0166] Comparative Example 1-2: Preparation of negative electrode active material slurry

[0167] 6 g of carbon black with a particle size (D50) of 41 nm (oxygen concentration of 5.2 atomic %), 0.7 g of AgF with a particle size (D50) of 10 nm to 20 nm, 9.33 g of PVdF binder (6% solids), and 6 g of NMP solution were placed in a Thinky mixer container and mixed at 1800 rpm for 12 times, each for 3 minutes. Then, an additional 6 g of NMP solution was added and mixed at 1800 rpm for 5 times, each for 3 minutes, to prepare the negative electrode active material slurry of Example 1.

[0168] Comparative Examples 1-3: Preparation of Negative Electrode Active Material Slurry

[0169] A negative active material slurry was prepared in the same manner as in Example 1, except that 2 g of MgF 2 having a particle size (D50) of 40 nm to 60 nm was used instead of 2 g of AgF.

[0170] Comparative Examples 1-4: Preparation of Negative Electrode Active Material Slurry

[0171] 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 atomic %) with a particle size (D50) of 40 nm was used instead of carbon black (containing an oxygen concentration of 5.2 atomic %), and MgF2 with a particle size (D50) of 35 nm to 45 nm was used instead of AgF.

[0172] Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4: Preparation of Negative Electrode

[0173] The negative electrodes (1.2 mAh / cm 2) were prepared by blade coating each of the negative electrode active material slurries prepared in Examples 1-1 to 1-6 and Comparative Examples 1-1 to 1-4 on a SUS foil to a thickness of 10 μm and drying.

[0174] Preparation of All-Solid-State Lithium-Ion Secondary Batteries of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4

[0175] The pouch-type single cells of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4 were manufactured by loading a 5 mAh / cm 2 A positive electrode containing a positive electrode active material of was used as a positive electrode, the negative electrodes manufactured in Examples 2-1 to 2-6 and Comparative Examples 2-1 to 2-4 were used as negative electrodes, and a sulfide-based all-solid electrolyte (LPSCl composition) was used as an electrolyte.

[0176] Experimental Example 1: Evaluating the characteristics of battery cells

[0177] The pouch-type single cells of Examples 3-1 to 3-6 and Comparative Examples 3-1 to 3-4 were operated at an operating temperature of 60° C. within an operating voltage range of 4.25 V to 3.0 V to evaluate their cycle characteristics, and the results are shown in Table 2 below.

[0178] [Table 2]

[0179]

Claims

1. A negative electrode comprising a current collector and an active material layer, in, The active material layer includes carbon material particles and at least one metal fluoride particle selected from the group consisting of AgF, LiF, ZnF2, AlF3, CaF2, CoF3, CuF2, NiF2, and CoF2.

2. The negative electrode according to claim 1, wherein The metal fluoride particles may be present in an amount of 15 to 50 parts by weight based on 100 parts by weight of the total weight of the carbon material particles and the metal fluoride particles.

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

5.

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

5. The negative electrode according to claim 1, wherein The active material layer includes 60 to 80 weight % of carbon material particles, 15 to 30 weight % of metal fluoride particles, and 3 to 20 weight % of a binder.

6. The negative electrode according to claim 1, wherein The carbon material particles contain 3 atomic % to 10 atomic % of oxygen.

7. The negative electrode according to claim 6, wherein Oxygen exists in the form of being incorporated into functional groups bound to the carbon material particles.

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

9. A lithium ion secondary battery comprising: The negative electrode according to claim 1; positive electrode; and An electrolyte is provided 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 anode-less battery.

Images